Patent Publication Number: US-11398779-B2

Title: Multi-path converter and control method therefor

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation in Part of International Application No. PCT/KR2018/003301, filed on Mar. 21, 2018, which claims priority from Korean Patent Application No. 10-2017-0042876, filed on Apr. 3, 2017, Korean Patent Application No. 10-2017-0083619, filed on Jun. 30, 2017, and Korean Patent Application No. 10-2018-0015712, filed on Feb. 8, 2018. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a converter having multiple paths and a control method thereof, and more specifically, to a converter for converting a voltage of input power to output the converted voltage to a load, and a control method thereof. 
     BACKGROUND ART 
     As the number of applications applied to electrical and electronic devices is increased and functions of the electrical and electronic devices are increased, power consumed by the devices is increasing continuously. Accordingly, power management circuits that supply power required by the devices should be designed to have high power efficiency characteristics in high power applications. This is because a power management circuit having high power efficiency not only increases a usage time of a device but also reduces heat generated in the power management circuit in the device. 
     The conventional power management circuits are mainly designed through two methods. One method is a switched capacitor or charge pump method using a capacitor, and the other method is a switched inductor method using an inductor. 
     First, since the switched capacitor method does not use a bulky inductor and uses a capacitor that is advantageous in being embedded in a chip as compared with an inductor, there is a great advantage that an area of a printed circuit board (PCB) may be reduced. However, since a practicable voltage conversion ratio (V OUT /V IN ) is discontinuous in the switched capacitor method, a high efficiency characteristic may be achieved only at a specific voltage conversion ratio. Therefore, in order to increase a practicable voltage conversion ratio to implement a high efficiency characteristic in a wide voltage range, a power management integrated circuit (PMIC) should be designed as a reconfigurable type, which increases complexity of a system. In addition, when a load current (I LOAD ) is increased, since capacitance of a capacitor constituting a converter should be increased, the capacitor may not be integrated in an integrated circuit (IC), and thus, a plurality of external capacitors may be required. As a result, the switched capacitor method may consume a larger area of a PCB as compared with the switched inductor method. Therefore, the switched capacitor method is mainly used in low power applications. 
     On the other hand, a power management circuit using the switched inductor method is bulky and uses an inductor that is relatively expensive as compared with other external devices, there are many advantages to the switched capacitor method in that a practicable voltage conversion ratio is continuous and a high efficiency characteristic is implemented in a very wide range. In addition, since there is no additional external device even when a load current is increased, the power management circuit using the switched inductor method is indispensably used in various modern devices of which power consumption is increasing. 
       FIG. 1  is a diagram illustrating an example of the conventional power management circuit using the switched inductor method.  FIG. 2A  and  FIG. 2B  show diagrams for describing a method of improving efficiency of the conventional power management circuit shown in  FIG. 1 . 
     As shown in  FIG. 1 , when a load current I LOAD  is increased, a current I L  flowing in an inductor is also increased. A parasitic resistor (R DCR ) connected in series with the inductor is inevitably included in the inductor, and as a level of the current flowing in the inductor is increased, power loss caused by the parasitic resistor is considerably increased. The power loss limits efficiency characteristics of the power management circuit and causes heat generation. Therefore, in order to increase power efficiency, it is preferable to use an inductor having a small parasitic resistance value as shown in  FIG. 2A . In this case, a volume or unit cost of the inductor is increased. 
     In particular, in the case of a power management circuit to be included in a mobile device that is being continuously miniaturized, a volume thereof is also restricted according to a size of a device to be manufactured. Thus, an inductor indispensably used in a switched-inductor power management circuit is also limited to an ultra-small inductor (having a height ranging from 1 mm to 1.5 mm). That is, as described above, it is impossible to use a bulky inductor which has a small parasitic resistance value. Therefore, it is necessary to use a smaller inductor for the same inductance to satisfy volume characteristics of a mobile device, but a small inductor includes a very large parasitic resistor. To improve efficiency under such conditions, as shown in  FIG. 2B , there is a method of using a plurality of inductors in parallel. This method reduces a level of a current flowing in each inductor, thereby reducing the total current loss caused by a parasitic resistor. However, since the method requires the plurality of inductors, a volume and a unit cost are increased. Also, a circuit for controlling a current to be divided to each inductor is additionally required, thereby increasing complexity of a system. 
     In addition, in the case of the conventional buck-boost converter and boost converter, since a current is not supplied to a load while a current in the inductor is built-up, a current supplied to the load is discontinuous. Accordingly, a level of the current in the inductor should be much greater than that of a load current, which requires an inductor with a high saturation current value. In addition, the discontinuous supplying of a current generates a large ripple voltage at an output voltage terminal and causes a switching spike. 
     DISCLOSURE 
     Technical Problem 
     The present disclosure is directed to providing a multi-path converter in which a current transfer path using a capacitor is used in addition to a current transfer path using an inductor. As such, a current flows through a plurality of parallel paths to an output terminal (i.e., load), thereby reducing a total root mean square (RMS) current flowing in an inductor, and a control method thereof. 
     Technical Solution 
     The exemplary embodiments may provide a converter including: an input unit; an output unit; and a conversion unit configured to convert a voltage of power input through the input unit and transfer the converted voltage to the output unit by transferring a current to the output unit through a plurality of parallel current transfer paths including at least one inductor and at least one capacitor. 
     The plurality of parallel current transfer paths may include a first current transfer path including at least one inductor and a second current transfer path including at least one capacitor. 
     The plurality of parallel current transfer paths may include more than one of the first current transfer path or more than one of the second current transfer path. 
     The first current transfer path may further includes at least one capacitor. 
     The conversion unit may periodically perform an operation including a plurality of conversion operation modes, and the conversion unit may divide and transfer the current to the output unit through the plurality of parallel current transfer paths in at least one of the plurality of conversion operation modes. 
     The conversion unit may function as one of a step-down converter, a step-up converter, and a step-up-and-down converter. 
     The converter may include a plurality of conversion units which convert voltages concurrently in different conversion operation modes. 
     The converter may include a plurality of output units including the output unit, and the conversion unit may convert the power input through the input unit to transfer the converted power to each of the plurality of output units. 
     The conversion unit may perform a function of a step-up converter with respect to some output units of the plurality of output units and may perform a function of a step-down converter with respect to remaining output units of the plurality of output units. 
     The converter may include a plurality of conversion units including the conversion unit, and the plurality of conversion units may be connected in series, parallel, or series-parallel with each other. 
     The conversion unit may transfer the current to the output unit while the voltage of the input power is converted. 
     The exemplary embodiment may provide a control method of a multi-path converter including converting a voltage of power input through the input unit by transferring a current to the output unit through a plurality of parallel current transfer paths using at least one inductor and at least one capacitor. 
     The plurality of parallel current transfer paths may include a first current transfer path including at least one inductor and a second current transfer path including at least one capacitor. 
     The parallel current transfer paths may include more than one of the first current transfer path or more than one of the second current transfer path. 
     The first current transfer path may further include at least one capacitor. 
     The transferring may include periodically performing an operation including a plurality of conversion operation modes, and the current is divided and transferred to the output unit through the plurality of parallel current transfer paths in at least one of the plurality of conversion operation modes. 
     The current may be transferred to the output unit while the voltage of the input power is converted. 
     According to an exemplary embodiment, a step-down converting method includes operating a step-down converter including a power source, an inductor, a capacitor, and a load in a multi-path manner and operating the step-down converter in a single-path manner. In the operating in the multi-path manner, a current is transferred to the load through a plurality of parallel current transfer paths, and in the operating in the single-path manner, a current is transferred to the load through a single current transfer path. 
     Advantageous Effects 
     According to the exemplary embodiments, since a current is divided and supplied to a load through an additional current transfer path using a capacitor, a root mean square (RMS) current flowing in an inductor can be reduced as compared with when a static current is supplied to the load (i.e., output terminal) by using only an inductor. Therefore, when a level of a load current is increased, it is possible to greatly reduce power loss caused by a parasitic resistor of an inductor which has the greatest power consumption in a power management integrated circuit (PMIC) for mobile applications. As such, it is possible to overcome a limitation of power efficiency which is not overcome by any conventional power management circuit technology. 
     According to the exemplary embodiments, since a capacitor having a relatively small volume and low unit cost as compared with an inductor is used as an element for distributing a current, it is possible to reduce a volume and a cost. Furthermore, a capacitor has a very low parasitic resistance value of about several mOhms as compared with an inductor which includes a serial parasitic resistor having a very high parasitic resistance value of about several hundred mOhms. Thus, power loss occurring in an additional current path using a capacitor is less than power loss in a current path using an inductor. In summary, an inductor structure according to the exemplary embodiments has a high efficiency characteristic. In addition, the inductor structure can increase a usage time of a device, greatly reduce heat generated in a power management circuit, and also reduce consumption of an area and volume of a printed circuit board (PCB). 
     Furthermore, according to the exemplary embodiments, since a current is divided and supplied to a load through an additional current transfer path other than a current path through which a current flows to the load, power loss can be reduced as compared with a conventional step-down converter, thereby increasing efficiency. Consequently, according to the exemplary embodiments, under a condition of having the same efficiency as the conventional step-down converter, it is possible to increase efficiency as compared with the conventional step-down converter and also provide an output voltage in the same range as that of the conventional step-down converter. 
     According to the exemplary embodiments, a partial current is allowed to flow to an output terminal even while input power is stepped up, thereby reducing the current in the inductor to improve efficiency, reducing a ripple, and reducing switching noise due to a continuous current flow. Therefore, according to the exemplary embodiments, it is possible to prevent a reduction in performance of a load connected to an output terminal of a step-up converter, that is, performance of a block to which a high voltage formed by the step-up converter is applied. 
    
    
     
       DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram illustrating an example of a conventional power management circuit of a switched inductor method. 
         FIGS. 2A and 2B  show diagrams for describing a method of improving efficiency of the conventional power management circuit shown in  FIG. 1 . 
         FIG. 3  is a block diagram illustrating a converter with a multi-path according to an exemplary embodiment. 
         FIG. 4  is a diagram illustrating an extended example of the multi-path converter shown in  FIG. 3 . 
         FIG. 5  is a diagram illustrating another extended example of the multi-path converter shown in  FIG. 3 . 
         FIG. 6  is a diagram illustrating still another extended example of the multi-path converter shown in  FIG. 3 . 
         FIG. 7  is a diagram illustrating yet another extended example of the multi-path converter shown in  FIG. 3 . 
         FIG. 8  is a diagram illustrating yet another extended example of the multi-path converter shown in  FIG. 3 . 
         FIG. 9  is a diagram illustrating yet another extended example of the multi-path converter shown in  FIG. 3 . 
         FIG. 10  is a diagram illustrating yet another extended example of the multi-path converter shown in  FIG. 3 . 
         FIG. 11  is a flowchart illustrating a control method of the multi-path converter according to the exemplary embodiment. 
         FIG. 12  is a block diagram illustrating a first step-down converter with a dual-path according to an exemplary embodiment. 
         FIG. 13  is a circuit diagram illustrating a configuration of the first step-down converter shown in  FIG. 12 . 
         FIGS. 14A and 14B  show diagrams for describing an example of a step-down operation mode of the first step-down converter shown in  FIG. 13 . 
         FIG. 15  shows diagrams illustrating an example of the first step-down converter with the dual-path according to the exemplary embodiment. 
         FIG. 16  shows graphs each obtained by testing the first step-down converter with the dual-path according to the exemplary embodiment in an environment with a duty ratio of 0.4. 
         FIG. 17  is a graph obtained by testing the first step-down converter with the dual-path according to the exemplary embodiment in a first simulation environment. 
         FIG. 18  is a graph obtained by testing the first step-down converter with the dual-path according to the exemplary embodiment in a second simulation environment. 
         FIG. 19  is a flowchart illustrating a control method of the first step-down converter with the dual-path according to the exemplary embodiment. 
         FIG. 20  is a flowchart illustrating a current transferring operation shown in  FIG. 19  in more detail. 
         FIG. 21  is a circuit diagram illustrating a configuration of a second step-down converter with a dual-path according to the exemplary embodiment. 
         FIGS. 22A to 22C  show diagrams for describing an example of a step-down operation mode of the second step-down converter shown in  FIG. 21   
         FIG. 23  is a diagram illustrating an example of the second step-down converter with the dual-path according to the exemplary embodiment. 
         FIG. 24  is a flowchart illustrating a control method of the second step-down converter with the dual-path according to the exemplary embodiment. 
         FIG. 25  is a flowchart illustrating a current transferring operation shown in  FIG. 24  in more detail. 
         FIG. 26  is a circuit diagram illustrating a configuration of a third step-down converter with a dual-path according to the exemplary embodiment. 
         FIGS. 27A and 27B  show diagrams for describing an example of a step-down operation mode of the third step-down converter shown in  FIG. 26 . 
         FIG. 28  is a flowchart illustrating a control method of the third step-down converter with the dual-path according to the exemplary embodiment. 
         FIG. 29  is a circuit diagram illustrating a configuration of a fourth step-down converter with a dual-path according to the exemplary embodiment. 
         FIGS. 30A to 30B  show diagrams for describing an example of a step-down operation mode of the fourth step-down converter shown in  FIG. 29 . 
         FIG. 31  is a circuit diagram illustrating a configuration of a fifth step-down converter with a dual-path according to the exemplary embodiment. 
         FIGS. 32A to 32C  show diagrams for describing an example of a step-down operation mode of the fifth step-down converter shown in  FIG. 31 . 
         FIG. 33  is a circuit diagram illustrating a configuration of a sixth step-down converter with a dual-path according to the exemplary embodiment. 
         FIGS. 34A and 34B  show diagrams for describing an example of a step-down operation mode of the sixth step-down converter shown in  FIG. 33 . 
         FIGS. 35A to 35C  show diagrams for describing another example of a step-down operation mode of the sixth step-down converter shown in  FIG. 33 . 
         FIG. 36  is a circuit diagram illustrating a configuration of a seventh step-down converter with a dual-path according to the exemplary embodiment. 
         FIG. 37  is a circuit diagram illustrating a configuration of an eighth step-down converter with a dual-path according to the exemplary embodiment. 
         FIG. 38  is a circuit diagram illustrating a configuration of a ninth step-down converter with a dual-path according to the exemplary embodiment. 
         FIG. 39  is a circuit diagram illustrating a configuration of a tenth step-down converter with a dual-path according to the exemplary embodiment. 
         FIG. 40  is a circuit diagram illustrating a configuration of an eleventh step-down converter with a triple-path according to the exemplary embodiment. 
         FIG. 41  is a circuit diagram illustrating a configuration of a twelfth step-down converter with a triple-path according to the exemplary embodiment. 
         FIG. 42  is a circuit diagram illustrating a configuration of a thirteenth step-down converter with a multi-path according to the exemplary embodiment. 
         FIG. 43  is a circuit diagram illustrating a configuration of a fourteenth step-down converter with a multi-path according to the exemplary embodiment. 
         FIG. 44  is a block diagram illustrating a first step-up converter with a dual-path according to another exemplary embodiment. 
         FIG. 45  is a circuit diagram illustrating a configuration of the first step-up converter shown in  FIG. 44 . 
         FIGS. 46A and 46B  show diagrams for describing an example of a step-up operation mode of the first step-up converter with the dual-path according to another exemplary embodiment. 
         FIGS. 47A to 47C  show diagrams for describing another example of a step-up operation mode of the first step-up converter with the dual-path according to another exemplary embodiment. 
         FIGS. 48A and 48B  show diagrams for describing inductor current change due to step-up operation mode of first step-up converter having dual-path according to another exemplary embodiment. 
         FIG. 49  shows graphs each obtained by testing the first step-up converter according to another exemplary embodiment in an environment with a duty ratio of 0.5. 
         FIG. 50  shows graphs each obtained by testing the first step-up converter according to another exemplary embodiment in an environment with a duty ratio of 0.7. 
         FIG. 51  shows graphs each obtained by testing the first step-up converter according to another exemplary embodiment in an environment with a duty ratio of 0.4. 
         FIG. 52  shows graphs each obtained by testing the first step-up converter according to another exemplary embodiment in an environment with a duty ratio of 0.2. 
         FIG. 53  is a flowchart illustrating a control method of the first step-up converter with the dual-path according to another exemplary embodiment. 
         FIG. 54  is a flowchart illustrating a stepped-up power transferring operation shown in  FIG. 53  in more detail. 
         FIG. 55  is a diagram illustrating an example of a configuration and a step-up operation mode of a second step-up converter with the dual-path according to another exemplary embodiment. 
         FIG. 56  is a diagram illustrating another example of a step-up operation mode of the second step-up converter shown in  FIG. 55 . 
         FIG. 57  is a circuit diagram illustrating a configuration of a third step-up converter with a multi-path according to another exemplary embodiment. 
         FIG. 58  is a circuit diagram illustrating a configuration of a fourth step-up converter with a multi-path according to another exemplary embodiment. 
         FIGS. 59A and 59B  show diagrams for describing an example in which the second step-down converter shown in  FIG. 21  is operated in a single-path manner. 
         FIG. 60  is a graph showing a comparison between efficiencies when the second step-down converter shown in  FIG. 21  is operated in a multi-path manner and a single-path manner. 
         FIG. 61  is a flowchart for describing a step-down converting method according to a first exemplary embodiment. 
         FIG. 62  is a graph showing a comparison between efficiencies when the second step-down converter shown in  FIG. 21  is operated in a two-phase manner and a three-phase manner. 
         FIG. 63  is a flowchart for describing a step-down converting method according to a second exemplary embodiment. 
     
    
    
     MODES OF THE INVENTION 
     Hereinafter, exemplary embodiments of a converter with a multi-path and a control method thereof according to the exemplary embodiments will be described in detail with reference to the accompanying drawings. 
     A multi-path converter and a control method thereof according to an exemplary embodiment will be described with reference to  FIGS. 3 to 11 . 
     First, the multi-path converter according to the exemplary embodiment according to the present invention will be described with reference to  FIG. 3 . 
       FIG. 3  is a block diagram illustrating the multi-path converter according to the exemplary embodiment. 
     Referring to  FIG. 3 , in a converter  100  having multiple paths (hereinafter, referred to as a “converter”) according to the exemplary embodiment, a current is divided and transferred to an output terminal through a plurality of parallel current transfer paths using inductors and capacitors. That is, the converter  100  uses a current transfer path using a capacitor in addition to a current transfer path using an inductor, a current flows through a plurality of parallel paths so as to be output to an output terminal (load), thereby reducing a total root mean square (RMS) current flowing in the inductor. 
     To this end, the converter  100  may include an input unit  110  to which power is input, a conversion unit  130  which converts (steps down or up) a voltage of the input power, and an output unit  150  which receives and transfers the converted power to an external device. 
     Here, the input unit  110  may include an alternating current (AC) power source, a direct current (DC) power source, a power supply source (various voltage or current power sources), and the like. 
     In addition, the output unit  150  may include any type of load that may be modeled using various passive elements including a resistor, a capacitor, and an inductor. That is, any type of load using a conventional power management integrated circuit (PMIC) may be included in the output unit  150 . 
     The conversion unit  130  may include functions of all conventional converters. For example, the conversion unit  130  may perform a function of a step-down converter or buck converter in which a voltage of an output terminal is lower than a voltage of an input terminal. Also, the conversion unit  130  may perform a function of a step-up converter or boost converter in which a voltage of an output terminal is higher than a voltage of an input terminal. The conversion unit  130  may also perform a function of a step-up-and-down converter or buck-boost converter in which a voltage of an output terminal is lower or higher than a voltage of an input terminal. 
     The conversion unit  130  divides and transfers a current to the output unit through a plurality of current transfer paths. For example, the conversion unit  130  may divide and transfer a current to the output unit  150  through the plurality of current transfer paths including a first current transfer path using an inductor and a second current transfer path using a capacitor. Here, in the plurality of current transfer paths, at least one of the first current transfer path and the second current transfer path may include a plurality of current transfer paths. For example, the plurality of current transfer paths may include a current transfer path using an inductor, a current transfer path using a first capacitor, and a current transfer path using a second capacitor. Of course, one current transfer path may use one inductor, one capacitor, a plurality of inductors, a plurality of capacitors, or a combination of at least one inductor and at least one capacitor. 
     In addition, when the conversion unit  130  repeatedly performs an operation including a plurality of conversion operation modes (for example, a plurality of step-down operation modes or a plurality of step-up operation modes), the conversion unit  130  may divide and transfer a current to the output unit  150  through the plurality of current transfer paths in an entire section in which the plurality of conversion operation modes are driven or in a partial section in which some conversion operation modes of the plurality of conversion operation modes are driven. 
     As described above, in the converter  100  according to the exemplary embodiment, a current may be divided and supplied to a load through an additional parallel current transfer path using a capacitor unlike a conventional converter in which a current is supplied to a load by using only an inductor. That is, according to the converter  100 , a DC current level of an inductor may be reduced. When the converter  100  performs a function of a step-down converter, a ripple current of an inductor may be reduced. In addition, an inductor and a capacitor of the converter  100  may supply a static current to the load (i.e., output terminal). In addition, as compared with an inductor, as can be confirmed in Table 1, a capacitor includes a much smaller parasitic resistor and has a relatively small volume and low unit cost. Therefore, as compared with only using a plurality of inductors, adding a capacitor may reduce a current level flowing in an inductor. Thus, it is possible to considerably reduce power loss occurring in a parasitic resistor and overcome a limitation of power efficiency which is not overcome by any conventional power management circuit technology. In addition, by using a capacitor having a relatively small volume and low unit cost, it is possible to reduce the volume and cost of inductor that is relatively large and expensive. Accordingly, it is possible to greatly reduce heat generated in a power management circuit, increase a usage time of a device, and reduce consumption of an area and volume of a printed circuit board (PCB). 
     
       
         
           
               
             
               
                 TABLE 1 
               
               
                   
               
             
            
               
                 List of External Inductors 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                   
                 Saturation 
                 Dimension 
                   
                   
                   
               
               
                   
                 Inductance 
                 current 
                 [L × W × H] 
                 DCR 
                 Cost ($) 
               
               
                   
                 (uH) 
                 rating (A) 
                 (mm) 
                 (mΩ) 
                 @1000 
                 Type 
               
               
                   
               
               
                 Bulky size 
                 4.7 
                 25.4 
                 11.8 × 11.8 × 10.0 
                 5.7 
                 2.05 
                 XAL1010-472 
               
               
                 and small 
                 4.7 
                 12 
                 13.0 × 13.0 × 6.0 
                 6.1 
                 0.74 
                 SER1360-472 
               
               
                 DCR 
                 2.2 
                 10 
                 11.2 × 11.2 × 5.2 
                 4.0 
                 1.15 
                 SER1052-222 
               
               
                   
                 2.2 
                 19.6 
                 8.0 × 8.0 × 7.0 
                 6.3 
                 1.45 
                 XAL7070-222 
               
               
                 Small 
                 4.7 
                 0.57 
                 2.2 × 1.45 × 1.0 
                 680 
                 0.29 
                 PFL2010-472 
               
               
                 size, large 
                 4.7 
                 1.1 
                 5.0 × 5.0 × 1.0 
                 175 
                 0.49 
                 LPS5010-472 
               
               
                 DCR, and 
                 2.2 
                 1.4 
                 3.2 × 2.3 × 1.5 
                 130 
                 0.28 
                 PFL3515-222 
               
               
                 cheap 
                 2.2 
                 2.7 
                 5.0 × 5.0 × 1.5 
                 90 
                 0.46 
                 LPS5015-222 
               
               
                 price 
                 2.2 
                 0.79 
                 2.2 × 1.45 × 1.0 
                 465 
                 0.29 
                 PFL2010-222 
               
               
                   
                 2.2 
                 1.6 
                 5.0 × 5.0 × 1.0 
                 100 
                 0.49 
                 LPS5010-222 
               
               
                   
               
            
           
           
               
            
               
                 List of External Capacitors 
               
            
           
           
               
               
               
               
               
               
               
            
               
                   
                   
                 Rated 
                 Dimension 
                   
                   
                   
               
               
                   
                 Capacitance 
                 Voltage 
                 [L × W × H] 
                 ESR 
                 Cost ($) 
               
               
                   
                 (uF) 
                 [DC] (V) 
                 (mm) 
                 (mΩ) 
                 @1000 
                 Type 
               
               
                   
               
               
                 Small 
                 22 
                 10 
                 2.0 × 1.25 × 0.85 
                 2.6 
                 0.14 
                 C2012X5R1A226M085AC 
               
               
                 size, small 
                 22 
                 10 
                 2.0 × 1.25 × 1.25 
                 2.3 
                 0.16 
                 C2012X5R1A226K125AB 
               
               
                 ESR, and 
                 10 
                 25 
                 2.0 × 1.25 × 0.85 
                 2.7 
                 0.05 
                 C2012X5R1C106K085AC 
               
               
                 cheap 
                 10 
                 25 
                 2.0 × 1.25 × 1.25 
                 2.1 
                 0.08 
                 C2012X5R1E106K125AB 
               
               
                 price 
                 10 
                 6.3 
                 1.6 × 0.8 × 0.8 
                 4.4 
                 0.13 
                 C1608X5R0J106K080AB 
               
               
                   
               
            
           
         
       
     
     Extended examples of the multi-path converter according to the exemplary embodiment will be described with reference to  FIGS. 4 to 10 . 
       FIG. 4  is a diagram illustrating an example of the multi-path converter shown in  FIG. 3 . 
     Referring to  FIG. 4 , a converter  100  according to the exemplary embodiment may include one conversion unit  130 , one output unit  150 , and a plurality of input units  110 . Here, an output voltage may have various characteristics such as step-down, step-up, and step-down-and-up. 
     A plurality of inductors, a plurality of capacitors, and/or a plurality of switches may be included in the conversion unit  130 . Here, examples of the input unit  110  may include, but are not limited to, an AC power source, a DC power source, a power supply source (various voltage or current power sources), and the like. In addition, the output unit  150  may include any type of load that may be modeled using various passive elements including a resistor, a capacitor, and an inductor, that is, any type of load using the conventional PMIC. 
       FIG. 5  is a diagram illustrating another example of the multi-path converter shown in  FIG. 3 . 
     Referring to  FIG. 5 , a converter  100  according to the exemplary embodiment may include one input unit  110 , one conversion unit  130 , and a plurality of output units  150 . 
     Here, an output voltage may have various characteristics such as step-down, step-up, and step-down-and-up. 
     A plurality of inductors, a plurality of capacitors, and/or a plurality of switches may be included in the conversion unit  130 . In addition, examples of the input unit  110  may include, but are not limited to, an AC power source, a DC power source, a power supply source (various voltage or current power sources), and the like. Furthermore, the output unit  150  may include any type of load that may be modeled using various passive elements including a resistor, a capacitor, and an inductor. That is, any type of load using the conventional PMIC may be included in the output unit  150 . 
       FIG. 6  is a diagram illustrating still another example of the multi-path converter shown in  FIG. 3 . 
     Referring to  FIG. 6 , a converter  100  according to the exemplary embodiment may include a plurality of input units  110 , a plurality of conversion units  130 , and a plurality of output units  150 . 
     Here, an output voltage may have various characteristics such as step-down, step-up, and step-down-and-up. 
     A plurality of inductors, a plurality of capacitors, and/or a plurality of switches may be included in the conversion unit  130 . In addition, the input unit  110  may include an AC power source, a DC power source, a power supply source (various voltage or current power sources), and the like. Furthermore, the output unit  150  may include any type of load that may be modeled using various passive elements including a resistor, a capacitor, and an inductor. That is, any type of load using the conventional PMIC may be included in the output unit  150 . 
       FIG. 7  is a diagram illustrating yet another example of the multi-path converter shown in  FIG. 3 . 
     Referring to  FIG. 7 , a converter  100  according to the exemplary embodiment may include one input unit  110 , one output unit  150 , and a plurality of conversion units  130 . 
     Here, the plurality of conversion units  130  may be connected in series with each other. 
       FIG. 8  is a diagram illustrating yet another example of the multi-path converter shown in  FIG. 3 . 
     Referring to  FIG. 8 , a converter  100  according to the exemplary embodiment may include one input unit  110 , one output unit  150 , and a plurality of conversion units  130 . 
     Here, the plurality of conversion units  130  may be connected in parallel with each other. 
     The conversion units  130  are arranged in parallel in  FIG. 7  and arranged in parallel in  FIG. 8 , but the arrangement of the conversion units  130  is not limited thereto. For example, the plurality of conversion units  130  may be connected in series-parallel (combination of series and parallel) with each other according to exemplary embodiments. 
       FIG. 9  is a diagram illustrating yet another example of the multi-path converter shown in  FIG. 3 . 
     Referring to  FIG. 9 , a converter  100  according to the exemplary embodiment may include one input unit  110 , one output unit  150 , a plurality of conversion units  130 , and a conventional converter module  10 . 
     Here, the plurality of conversion units  130  and the conventional converter module  10  may be connected in series with each other. 
       FIG. 10  is a diagram illustrating yet another example of the multi-path converter shown in  FIG. 3 . 
     Referring to  FIG. 10 , a converter  100  according to the exemplary embodiment may include one input unit  110 , one output unit  150 , a plurality of conversion units  130 , and a conventional converter module  10 . 
     Here, the plurality of conversion units  130  and the conventional converter module  10  may be connected in parallel with each other. 
     The plurality of conversion units  130  and the conventional converter module  10  are connected in serial in  FIG. 9  and connected in parallel in  FIG. 10 , the arrangement is not limited thereto. For example, the plurality of conversion units  130  and the conventional converter module  10  may be connected in series-parallel (combination of series and parallel) with each other according to exemplary embodiments. 
     In addition, in the converter  100  shown in  FIGS. 7 to 10 , the plurality of conversion units  130  may be operated in synchronization with each other. Otherwise, the plurality of conversion units  130  may be independently operated according to different clocks. 
     The control method of the multi-path converter according to the exemplary embodiment will be described with reference to  FIG. 11 . 
       FIG. 11  is a flowchart illustrating the control method of the multi-path converter according to the exemplary embodiment. 
     Referring to  FIG. 11 , the control method of the multi-path converter according to the exemplary embodiment includes converting (e.g., stepping down or up) a voltage of power input to the converter  10  and transferring a current to the output terminal. The current is divided and transferred to the output terminal through a plurality of current transfer paths using at least one inductor and at least one capacitor (S 100 ). 
     In this case, in the transferring of the current, the current is divided and transferred to the output unit through the plurality of current transfer paths. For example, in the converter  100 , the current may be divided and transferred to the output terminal through the plurality of current transfer paths including a first current transfer path using an inductor and a second current transfer path using a capacitor. Here, the plurality of current transfer paths may include a plurality of the first current transfer paths and/or a plurality of the second current transfer paths. For example, the plurality of current transfer paths may include a current transfer path using an inductor, a current transfer path using a first capacitor, and a current transfer path using a second capacitor. According to an exemplary embodiment, one current transfer path may use one or more inductors, one or more capacitors, or a combination thereof. 
     In addition, in the transferring of the current, when an operation including a plurality of conversion operation modes (for example, a plurality of step-down operation modes or a plurality of step-up operation modes) is periodically performed, the current may be divided and transferred to the output terminal through the plurality of current transfer paths in an entire section in which the plurality of conversion operation modes are driven or in a partial section in which some conversion operation modes of the plurality of conversion operation modes are driven. 
     As described above, in the multi-path converter and the control method thereof according to the exemplary embodiments, a current is divided and transferred through a plurality of current transfer paths using at least one inductor and at least one capacitor to flow to an output terminal (i.e., a load). As such, an amount of power loss may be reduced as compared with a conventional converter, thereby increasing power efficiency. 
     Embodiment 1: Multi-Path Step-Down Converter 
     A multi-path converter and a control method thereof according to exemplary embodiments will be described in detail with reference to  FIGS. 12 and 43 . 
     The multi-path converter according to the exemplary embodiment may perform a function of a step-down converter configured to step down input power. That is, in the converter according to the exemplary embodiment, an output voltage V OUT  is lower than an input voltage V IN , and a current is divided and transferred to an output terminal through a plurality of current transfer paths (for example, two current transfer paths, three current transfer paths, or n current transfer paths) using at least one inductor and at least one capacitor. 
     First, a first step-down converter with a dual-path according to the exemplary embodiment will be described with reference to  FIGS. 12 to 14 . 
       FIG. 12  is a block diagram illustrating the first step-down converter with the dual-path according to the exemplary embodiment.  FIG. 13  is a circuit diagram illustrating a configuration of the first step-down converter shown in  FIG. 12 .  FIGS. 14A and 14B  show diagrams for describing an example of a step-down operation mode of the first step-down converter shown in  FIG. 13 . 
     Referring to  FIGS. 12 and 13 , a first step-down converter  100 - 1  with a dual-path (hereinafter, referred to as a “first step-down converter”) according to the exemplary embodiment includes an input unit  110  to which power is input, a conversion unit  130  which steps down the input power, and an output unit  150  which receives and transfers the stepped-down power to an external device. Here, a power conversion ratio (V OUT /V IN ) of the first step-down converter  100 - 1  is in a range of 0.5 to 1. 
     That is, the conversion unit  130  steps down the power input through the input unit  110  and transfers the stepped-down power to the output unit  150 . The conversion unit  130  transfers a current to the output unit  150  through two different current transfer paths. For example, the conversion unit  130  may divide and transfer the current to the output unit  150  through a first current transfer path using an inductor I and a second current transfer path using a capacitor C. Accordingly, as compared with a conventional step-down converter which transfers a current to an output terminal (i.e., load) only through an inductor, the first step-down converter  100  according to the exemplary embodiment divides and transfers the current to the output terminal through the first current transfer path including the inductor I and the second current transfer path including the capacitor C. As such, power loss is reduced and efficiency is increased. 
     To this end, the conversion unit  130  may include the inductor I, the capacitor C, a first switch SW 1 , a second switch SW 2 , and a third switch SW 3 . 
     One end of the inductor I is connected to a node between the first switch SW 1  and the capacitor C, and the other end thereof is connected to a node between the output unit  150  and the second switch SW 2 . 
     One end of the capacitor C is connected to a node between the first switch SW 1  and the inductor I, and the other end thereof is connected to a node between the second switch SW 2  and the third switch SW 3 . 
     One end of the first switch SW 1  is connected to the input unit  110 , and the other end thereof is connected to a node between the inductor I and the capacitor C. 
     One end of the second switch SW 2  is connected to a node between the capacitor C and the third switch SW 3 , and the other end thereof is connected to a node between the inductor I and the output unit  150 . 
     One end of the third switch SW 3  is connected to a node between the capacitor C and the second switch SW 2 , and the other end thereof is connected to a node between the input unit  110  and the output unit  150 . 
     More specifically, the conversion unit  130  may be driven in the order of a first step-down operation mode and a second step-down operation mode. That is, the conversion unit  130  may periodically perform an operation that sequentially includes the first step-down operation mode and the second step-down operation mode. The conversion unit  130  may step down the power input from the input unit  110 , and transfer the stepped-down power to the output unit  150 . In this case, a duty ratio indicating a driving time of the first step-down operation mode may be determined based on an input voltage, an output voltage, and the like. 
     As shown in  FIG. 14A , the conversion unit  130  may be driven in the first step-down operation mode in which the first switch SW 1  and the second switch SW 2  are turned on and the third switch SW 3  is turned off. Accordingly, a current flowing to the output unit  150  (i.e., a load) is divided and transferred through a first current transfer path P 1  composed of the inductor I and a second current transfer path P 2  composed of the capacitor C. Therefore, an RMS value of the current flowing in the inductor I is reduced due to the additional current transfer path using the capacitor C. 
     After the conversion unit  130  is driven in the first step-down operation mode, the conversion unit  130  may be driven in the second step-down operation mode in which the third switch SW 3  is turned on and the first switch SW 1  and the second switch SW 2  are turned off, as shown in  FIG. 14B . 
     As described above, in the first step-down operation mode, while a current is accumulated in the inductor I, a current is divided and transferred to the output unit  150  (i.e., the load) through the first current transfer path using the inductor I and the second current transfer path using the capacitor C. In the second step-down operation mode, the current accumulated in the inductor I is transferred to the output unit  150 , that is, the load. Accordingly, since a current to be transferred to the output unit  150  (i.e., the load) is divided and transferred through two paths (first current transfer path and second current transfer path), an amount of power loss of the first step-down converter  100 - 1  according to the exemplary embodiment may be further reduced as compared with the conventional step-down converter, thereby increasing power efficiency. 
     The first step-down converter according to the exemplary embodiment will be further described with reference to  FIGS. 15 and 16 . 
       FIG. 15  shows diagrams illustrating an example of the first step-down converter according to the exemplary embodiment, and  FIG. 16  shows graphs each obtained by testing the first step-down converter according to the exemplary embodiment in an environment with a duty ratio of 0.4. That is,  FIG. 16  illustrates waveforms obtained by testing the first step-down converter  100 - 1  according to the exemplary embodiment under conditions in which a duty ratio is 40%, a voltage V IN  input through the input unit  110  is 5 V, a voltage V OUT  output through the output unit  150  is 3.06 V, and a current output through the output unit  150  is 1 A. 
     Referring to  FIGS. 15 and 16 , the first step-down converter  100 - 1  according to the exemplary embodiment periodically performs an operation that sequentially includes a first step-down operation mode Φ 1  and a second step-down operation mode Φ 2  to step down and transfer input power to the output terminal, that is, the load. 
     In this case, when the first step-down converter  100 - 1  according to the exemplary embodiment is driven in the first step-down operation mode Φ 1 , in the first step-down converter  100 - 1 , a current is divided and transferred to the output terminal (i.e., the load) through the first current transfer path using the inductor I and the second current transfer path using the capacitor C. 
     Performance of the first step-down converter according to the exemplary embodiment will be further described with respect to  FIGS. 17 and 18 . 
       FIG. 17  is a graph obtained by testing the first step-down converter with the dual-path according to the exemplary embodiment in a first simulation environment, and  FIG. 18  is a graph obtained by testing the first step-down converter with the dual-path according to the exemplary embodiment in a second simulation environment. 
     In order to test the performance of the first step-down converter  100 - 1  according to the exemplary embodiment, experiments were performed so as to compare the first step-down converter  100 - 1  with the conventional step-down converter in two simulation environments. 
     In the first simulation environment, the input voltage V IN  was fixed at 4.5 V, a driving time D 1  of the first step-down operation mode was changed between 0.05 and 0.95, and the current of the output terminal (that is, the load) was fixed at 1 A. Accordingly, the voltage V OUT  of the output terminal (that is, the load) is V IN /(2−D 1 ), that is, 2.25 V&lt;V OUT &lt;4.5 V, and a driving time D 2  of the second step-down operation mode is 1/(2−D 1 ). 
     In the second simulation environment, the voltage V OUT  of the output terminal (that is, the load) was fixed at 2.8 V, the driving time D 1  of the first step-down operation mode was changed between 0.05 and 0.95, and the current of the output terminal (that is, the load) was fixed at 1 A. Accordingly, the input voltage V IN  is V OUT (2−D 1 ), that is, 3.0 V&lt;V IN &lt;5.5 V, and the driving time D 2  of the second step-down operation mode is 1/(2−D 1 ). 
     Referring to  FIG. 17 , a test result in the first simulation environment confirms that power efficiency (solid line in  FIG. 17 ) of the first step-down converter according to the exemplary embodiment is increased by about 5% as compared with power efficiency (dashed line in  FIG. 17 ) of the conventional step-down converter. 
     Referring to  FIG. 18 , as a test result in the second simulation environment, it may be confirmed that power efficiency (solid line in  FIG. 18 ) of the first step-down converter according to the exemplary embodiment is further increased by about 4.7% as compared with power efficiency (dashed line in  FIG. 18 ) of the conventional step-down converter. 
     A control method of the first step-down converter according to the exemplary embodiment will be described with reference to  FIGS. 19 and 20 . 
       FIG. 19  is a flowchart illustrating the control method of the first step-down converter according to the exemplary embodiment. 
     Referring to  FIG. 19 , the first step-down converter  100 - 1  steps down an input power to transfer a current to the output unit  150 , and when the current is transferred to the output unit  150 , the current is transferred to the output unit  150  through two different current transfer paths (S 110 - 1 ). 
     For example, in the first step-down converter  100 - 1 , the current may be divided and transferred to the output unit  150  through a first current transfer path using the inductor I and a second current transfer path using the capacitor C. Accordingly, as compared with the conventional step-down converter which transfers a current to the output terminal (i.e., load) only through an inductor, the first step-down converter  100 - 1  according to the exemplary embodiment divides and transfers the current to the output terminal through the first current transfer path including the inductor I and the second current transfer path including the capacitor C, thereby reducing power loss and increasing efficiency. 
       FIG. 20  is a flowchart illustrating a current transferring operation shown in  FIG. 19  in more detail. 
     Referring to  FIG. 20 , the first step-down converter  100 - 1  may be driven in a first step-down operation mode (S 111 ). That is, the first step-down converter  100 - 1  may be driven in the first step-down operation mode in which the first switch SW 1  and a second switch SW 2  are turned on and the third switch SW 3  is turned off. Accordingly, a current which flows to the output unit  150  (i.e., the load) is divided and transferred through a first current transfer path P 1  using the inductor I and a second current transfer path P 2  using the capacitor C. 
     After the first step-down converter  100 - 1  is driven in the first step-down operation mode, the first step-down converter  100 - 1  may be driven in a second step-down operation mode (S 113 ). In the second step-down operation mode, the third switch SW 3  is turned on and the first switch SW 1  and the second switch SW 2  are turned off. 
     As described above, the first step-down converter  100 - 1  may periodically perform an operation that sequentially includes the first step-down operation mode and the second step-down operation mode. As such, the first step-down converter  100 - 1  may step down and transfer the power input from the input unit  110  to the output unit  150 . 
     In the first step-down operation mode, while a current is accumulated in the inductor I, a current is divided and transferred to the output unit  150  (i.e., the load) through the first current transfer path using the inductor I and the second current transfer path using the capacitor C. In the second step-down operation mode, the current accumulated in the inductor I is transferred to the output unit  150 , that is, the load. Accordingly, since the current to be transferred to the output unit  150  (i.e., the load) is divided and transferred through two paths (first current transfer path and second current transfer path), an amount of power loss of the first step-down converter  100 - 1  according to the exemplary embodiment may be reduced as compared with the conventional step-down converter, thereby increasing power efficiency. 
     A second step-down converter with a dual-path according to the exemplary embodiment will be described with reference to  FIGS. 21 to 22 . 
       FIG. 21  is a circuit diagram illustrating a configuration of the second step-down converter with the dual-path according to the exemplary embodiment.  FIGS. 22A to 22C  show diagrams for describing an example of a step-down operation mode of the second step-down converter shown in  FIG. 21 . 
     Since a second step-down converter  200 - 1  with a dual-path (hereinafter referred to as a “second step-down converter”) according to the exemplary embodiment is substantially similar to the first step-down converter  100 - 1  according to the above-described exemplary embodiment, differences therebetween will be described. 
     Referring to  FIG. 21 , the second step-down converter  200 - 1  according to the exemplary embodiment further includes a fourth switch SW 4  added to the first step-down converter  100 - 1  according to the exemplary embodiment. 
     That is, a conversion unit  230  may include an inductor I, a capacitor C, a first switch SW 1 , a second switch SW 2 , a third switch SW 3 , and the fourth switch SW 4 . 
     One end of the fourth switch SW 4  is connected to a node between the first switch SW 1  and the inductor I, and the other end thereof is connected to a node between the input unit  110  and the third switch SW 3 . 
     Here, the first switch SW 1  may be a P-type metal oxide semiconductor (PMOS) switch. The second switch SW 2 , the third switch SW 3 , and the fourth switch SW 4  may be N-type metal oxide semiconductor (NMOS) switches. 
     More specifically, the conversion unit  230  may be driven in the order of a first step-down operation mode, a third step-down operation mode, and a second step-down operation mode. That is, the conversion unit  230  may periodically perform an operation that sequentially includes the first step-down operation mode, the third step-down operation mode, and the second step-down operation mode. As such, the conversion unit  230  may step down and transfer power input from an input unit  210  to an output unit  250 . 
     That is, as shown in  FIG. 22A , the conversion unit  230  may be driven in the first step-down operation mode in which the first switch SW 1  and the second switch SW 2  are turned on and the third switch SW 3  and the fourth switch SW 4  are turned off. Accordingly, a current which flows to the output unit  250  (i.e., a load) is divided and transferred through a first current transfer path P 1  using an inductor I and a second current transfer path P 2  using a capacitor C. Therefore, an RMS value of the current flowing in the inductor I is reduced due to the additional current transfer path using the capacitor C. 
     After the conversion unit  230  is driven in the first step-down operation mode, as shown in  FIG. 22B , the conversion unit  230  may be driven in third step-down operation mode in which the fourth switch SW 4  is turned on and the first switch SW 1 , the second switch SW 2 , and the third switch SW 3  are turned off. 
     In addition, after the conversion unit  230  is driven in the third step-down operation mode, as shown in  FIG. 22C , the conversion unit  230  may be driven in the second step-down operation mode in which the third switch SW 3  is turned on and the first switch SW 1 , the second switch SW 2 , and the fourth switch SW 4  are turned off. 
     As described above, in the first step-down operation mode, while a current is accumulated in the inductor I, a current is divided and transferred to the output unit  250  (i.e., the load) through the first current transfer path using the inductor I and the second current transfer path using the capacitor C. Accordingly, since a current to be transferred to the output unit  250  (i.e., the load) is divided and transferred through two paths (first current transfer path and second current transfer path), an amount of power loss of the second step-down converter  200 - 1  according to the exemplary embodiment may be reduced as compared with the conventional step-down converter, thereby increasing power efficiency. 
     In addition, unlike the first step-down converter  100 - 1 , the second step-down converter  200 - 1  includes the fourth switch SW 4  which enables the third step-down operation mode. Thus, the second step-down converter  200 - 1  has a power conversion ratio (V OUT /V IN ) ranging from 0 and 1, which is a range wider than that of the first step-down converter  100 - 1 . Furthermore, in the second step-down converter  200 - 1 , an RMS current flowing in the first switch SW 1  may be reduced as compared with the first step-down converter  100 - 1 . Also, an RMS current flowing in the capacitor C may be reduced by adjusting a duty ratio of the first step-down operation mode Φ 1  and the second step-down operation mode Φ 3 . 
     That is, the first step-down converter  100 - 1  according to the exemplary embodiment may provide an output voltage having a range represented by [Expression 1] below.
 
 V   OUT =1/(2 −D   1 )* V   IN  
 
(½* V   IN   ≤V   OUT   ≤V   IN )  [Expression 1]
 
     Here, V IN  refers to an input voltage, V OUT  refers to an output voltage, and D 1  refers to a driving time of the first step-down operation mode. 
     On the other hand, the second step-down converter  200 - 1  according to the exemplary embodiment may provide an output voltage having a range represented by [Expression 2] below.
 
 V   OUT =(1 −D   2 )/(2 −D   1   −D   2 )* V   IN  
 
(0≤ V   OUT   ≤V   IN )  [Expression 2]
 
     Here, V IN  refers to an input voltage, V OUT  refers to an output voltage, D 1  refers to a driving time of the first step-down operation mode, and D 2  refers to a driving time of the third step-down operation mode. 
     An example of the second step-down converter according to the exemplary embodiment will be described with reference to  FIG. 23 . 
       FIG. 23  is a diagram illustrating an example of the second step-down converter according to the exemplary embodiment. 
     Referring to  FIG. 23 , the second step-down converter  200 - 1  according to the exemplary embodiment repeatedly performs an operation including a first step-down operation mode Φ 1 , a third step-down operation mode Φ 2 , and a second step-down operation mode Φ 3  and steps down and transfers input power to an output terminal, i.e., a load. 
     In this case, when the second step-down converter  200 - 1  according to the exemplary embodiment is driven in the first step-down operation mode Φ 1 , in the first step-down converter  100 - 1 , a current is divided and transferred to the output terminal (i.e., the load) through the first current transfer path using the inductor I and the second current transfer path using the capacitor C. 
     A control method of the second step-down converter according to the exemplary embodiment will be described with reference to  FIGS. 24 and 25 . 
       FIG. 24  is a flowchart illustrating the control method of the second step-down converter according to the exemplary embodiment. 
     Referring to  FIG. 24 , the second step-down converter  200 - 1  steps down input power to transfer a current to the output unit  250 , and when the current is transferred to the output unit  250 , the current is transferred to the output unit  250  through two different current transfer paths (S 210 - 1 ). 
     For example, in the second step-down converter  200 - 1 , the current may be divided and transferred to the output unit  250  through the first current transfer path using the inductor I and the second current transfer path using the capacitor C. Accordingly, as compared with the conventional step-down converter which transfers a current to an output terminal (i.e., load) through only an inductor, the second step-down converter  200 - 1  according to the exemplary embodiment divides and transfers a current to an output terminal through the first current transfer path passing including the inductor I and the second current transfer path including the capacitor C, thereby reducing power loss and increasing efficiency. 
       FIG. 25  is a flowchart illustrating a current transferring operation shown in  FIG. 24  in more detail. 
     Referring to  FIG. 25 , the second step-down converter  200 - 1  may be driven in the first step-down operation mode (S 211 ). That is, the second step-down converter  200 - 1  may be driven in the first step-down operation mode of turning the first switch SW 1  and the second switch SW 2  on and turning the third switch SW 3  and the fourth switch SW 4  off. Accordingly, a current flowing to the output unit  250  (i.e., the load) is divided and transferred through the first current transfer path P 1  using the inductor I and the second current transfer path P 2  using the capacitor C. 
     After the second step-down converter  200 - 1  is driven in the first step-down operation mode, the second step-down converter  200 - 1  may be driven in the third step-down operation mode (S 213 ) in which the fourth switch SW 4  is turned on and the first switch SW 1 , the second switch SW 2 , and the third switch SW 3  are turned off. 
     After the second step-down converter  200 - 1  is driven in the third step-down operation mode, the second step-down converter  200 - 1  may be driven in the second step-down operation mode (S 215 ) in which the third switch SW 4  is turned on and the first switch SW 1 , the second switch SW 2 , and the fourth switch SW are turned off. 
     As described above, the second step-down converter  200 - 1  may periodically perform an operation that sequentially includes the first step-down operation mode, the third step-down operation mode, and the second step-down operation mode. As such, the second step-down converter  200 - 1  may step down and transfer the power input from the input unit  210  to the output unit  250 . 
     That is, in the first step-down operation mode, while a current is accumulated in the inductor I, a current is divided and transferred to the output unit  250  (i.e., the load) through the first current transfer path using the inductor I and the second current transfer path using the capacitor C. Accordingly, since the current to be transferred to the output unit  250  (i.e., the load) is divided and transferred through two paths (first current transfer path and second current transfer path), an amount of power loss of the first step-down converter  200 - 1  according to the exemplary embodiment may be reduced as compared with the conventional step-down converter, thereby increasing power efficiency. 
     A third step-down converter with a dual-path according to the exemplary embodiment will be described with reference to  FIGS. 26 to 27 . 
       FIG. 26  is a circuit diagram illustrating a configuration of the third step-down converter with the dual-path according to the exemplary embodiment.  FIGS. 27A and 27B  show diagrams for describing an example of a step-down operation mode of the third step-down converter shown in  FIG. 26 . 
     Since a third step-down converter  300 - 1  with a dual-path (hereinafter referred to as a “third step-down converter”) according to the exemplary embodiment is substantially similar to the second step-down converter  200 - 1  according to the above-described exemplary embodiment, differences therebetween will be described. 
     Referring to  FIG. 26 , the third step-down converter  300 - 1  according to the exemplary embodiment additionally includes a fifth switch SW 5 , a sixth switch SW 6 , and a capacitor C 2 , in comparison with the second step-down converter  200 - 1 . 
     That is, a conversion unit  330  may include an inductor I, a capacitor C, a first switch SW 1 , a second switch SW 2 , a third switch SW 3 , a fourth switch SW 4 , a fifth switch SW 5 , a sixth switch SW 6 , and a capacitor C 2 . 
     One end of the capacitor C 2  is connected to a node between the first switch SW 1  and the inductor I, and the other end thereof is connected to the fourth switch SW 4 . 
     One end of the sixth switch SW 6  is connected to a node between the capacitor C 2  and the inductor I, and the other end thereof is connected to the capacitor C. 
     One end of the fifth switch SW 5  is connected to a node between the capacitor C 2  and the fourth switch SW 4 , and the other end thereof is connected to a node between the sixth switch SW 6  and the capacitor C. 
     More specifically, the conversion unit  330  may be driven in the order of a first step-down operation mode and a second step-down operation mode. That is, the conversion unit  330  may periodically perform an operation that sequentially includes the first step-down operation mode and the second step-down operation mode. As such, the conversion unit  330  may step down and transfer power input from an input unit  310  to an output unit  350 . 
     That is, as shown in  FIG. 27A , the conversion unit  330  may be driven in the first step-down operation mode in which the first switch SW 1 , the second switch SW 2 , and the fifth switch SW 5  are turned on and the third switch SW 3 , the fourth switch SW 4 , and the sixth switch SW 6  are turned off. Accordingly, a current which flows to the output unit  350  (i.e., a load) is divided and transferred through a first current transfer path P 1  using the inductor I and a second current transfer path P 2  using the capacitor C 2  and the capacitor C. 
     After the conversion unit  330  is driven in the first step-down operation mode, the conversion unit  330  may be driven in the second step-down operation mode in which the third switch SW 3 , the fourth switch SW 4 , and the sixth switch SW 6  are turned on and the first switch SW 1 , the second switch SW 2 , and the fifth switch SW 5  are turned off, as shown in  FIG. 27B . Accordingly, the current flowing to the output unit  350  (i.e., the load) is divided and transferred through a third current transfer path P 3  using the capacitor C and a fourth current transfer path P 4  using the capacitor C 2 . 
     As described above, in the first step-down operation mode, a current is divided and transferred to the output unit  350  (i.e., the load) through the first current transfer path P 1  using the inductor I and the second current transfer path P 2  using the capacitor C 2  and the capacitor C. In the second step-down operation mode, a current is divided to the output unit  350  (i.e., the load) through a third current transfer path P 3  using the capacitor C and a fourth current transfer path using the capacitor C 2 . Accordingly, since the current is divided and transferred through a plurality of current transfer paths in an entire section in which a plurality of step-down operation modes are driven, an amount of power loss of the third step-down converter  300 - 1  according to the exemplary embodiment may be reduced as compared with the conventional step-down converter, thereby increasing power efficiency. 
     A control method of the third step-down converter according to the exemplary embodiment will be described with reference to  FIG. 28 . 
       FIG. 28  is a flowchart illustrating the control method of the third step-down converter with the dual-path according to the exemplary embodiment. 
     Referring to  FIG. 28 , the third step-down converter  300 - 1  steps down an input power to transfer a current to the output unit  350  through two different current transfer paths (S 310 - 1 ). 
     More specifically, the third step-down converter  300 - 1  may be driven in the first step-down operation mode in which the first switch SW 1 , the second switch SW 2 , and the fifth switch SW 5  are turned on and the third switch SW 3 , the fourth switch SW 4 , and the sixth switch SW 6  are turned off. Accordingly, a current flowing to the output unit  350  (i.e., the load) is divided and transferred through the first current transfer path P 1  using the inductor I and the second current transfer path P 2  using the capacitor C 2  and the capacitor C. 
     After the third step-down converter  300 - 1  is driven in the first step-down operation mode, the third step-down converter  300 - 1  may be driven in the second step-down operation mode in which the third switch SW 3 , the fourth switch SW 4 , and the sixth switch SW 6  are turned on and the first switch SW 1 , the second switch SW 2 , and the fifth switch SW 5  are turned off. Accordingly, a current flowing to the output unit  350  (i.e., the load) is divided and transferred through the third current transfer path P 3  using the capacitor C and the fourth current transfer path P 4  using the capacitor C 2 . 
     A fourth step-down converter with a dual-path according to the exemplary embodiment will be described with reference to  FIGS. 29 and 30 . 
       FIG. 29  is a circuit diagram illustrating a configuration of the fourth step-down converter with the dual-path according to the exemplary embodiment, and  FIGS. 30A and 30B  show diagrams for describing an example of a step-down operation mode of the fourth step-down converter shown in  FIG. 29 . 
     Referring to  FIG. 29 , a fourth step-down converter  400 - 1  with a dual-path (hereinafter referred to as a “fourth step-down converter”) according to the present exemplary embodiment is configured by changing positions of some elements of the first step-down converter  100 - 1 . Here, a power conversion ratio (V OUT /V IN ) of the fourth step-down converter  400 - 1  is in the range of 0 to 0.5. 
     That is, a conversion unit  430  may include an inductor I, a capacitor C, a first switch SW 1 , a second switch SW 2 , and a third switch SW 3 . 
     One end of the inductor I is connected to a node between the capacitor C and the third switch SW 3 , and the other end thereof is connected to a node between the second switch SW 2  and an output unit  450 . 
     One end of the capacitor C is connected to a node between the first switch SW 1  and the second switch SW 2 , and the other end thereof is connected to a node between the inductor I and the third switch SW 3 . 
     One end of the first switch SW 1  is connected to an input unit  410 , and the other end thereof is connected to a node between the second switch SW 2  and the capacitor C. 
     One end of the second switch SW 2  is connected to a node between the first switch SW 1  and the capacitor C, and the other end thereof is connected to a node between the output unit  450  and the inductor I. 
     One end of the third switch SW 3  is connected to a node between the capacitor C and the inductor I, and the other end thereof is connected to a node between the input unit  410  and the output unit  450 . 
     More specifically, the conversion unit  430  may be driven in the order of a first step-down operation mode and a second step-down operation mode. That is, the conversion unit  430  may periodically perform an operation that sequentially includes the first step-down operation mode and the second step-down operation mode. As such, the conversion unit  430  may step down and transfer power input from the input unit  410  to the output unit  450 . 
     That is, as shown in  FIG. 30A , the conversion unit  430  may be driven in the first step-down operation mode in which the first switch SW 1  is turned on and the second switch SW 2  and the third switch SW 3  are turned off. 
     After the conversion unit  430  is driven in the first step-down operation mode, the conversion unit  430  may be driven in the second step-down operation mode in which the second switch SW 2  and the third switch SW 3  are turned on and the first switch SW 1  is turned off, as shown in  FIG. 30B . Accordingly, a current which flows to the output unit  450  (i.e., a load) is divided and transferred through a first current transfer path P 1  using the inductor I and a second current transfer path P 2  using the capacitor C. Therefore, an RMS value of the current flowing in the inductor I is reduced due to the additional current transfer path using the capacitor C. 
     A fifth step-down converter with a dual-path according to the exemplary embodiment will be described with reference to  FIGS. 31 and 32 . 
       FIG. 31  is a circuit diagram illustrating a configuration of the fifth step-down converter with the dual-path according to the exemplary embodiment, and  FIGS. 32A to 32C  show diagrams for describing an example of a step-down operation mode of the fifth step-down converter shown in  FIG. 31 . 
     Since a fifth step-down converter  500 - 1  with a dual-path (hereinafter referred to as a “fifth step-down converter”) according to the exemplary embodiment is substantially similar to the fourth step-down converter  400 - 1  according to the above-described exemplary embodiment, differences therebetween will be described. 
     Referring to  FIG. 31 , the fifth step-down converter  500 - 1  according to the exemplary embodiment may further include a fourth switch SW 4  in comparison with the fourth step-down converter  400 - 1 . 
     That is, a conversion unit  530  may include an inductor I, a capacitor C, a first switch SW 1 , a second switch SW 2 , a third switch SW 3 , and a fourth switch SW 4 . 
     One end of the inductor I is connected to a node between the capacitor C and the third switch SW 3 , and the other end thereof is connected to a node between the second switch SW 2  and an output unit  550 . 
     One end of the fourth switch SW 4  is connected to an input unit  510 , and the other end thereof is connected to a node between the capacitor C and the third switch SW 3 . 
     More specifically, the conversion unit  530  may be driven in the order of a first step-down operation mode, a third step-down operation mode, and a second step-down operation mode. That is, the conversion unit  530  may periodically perform an operation that sequentially includes the first step-down operation mode, the third step-down operation mode, and the second step-down operation mode. As such, the conversion unit  530  may step down and transfer power input from the input unit  510  to the output unit  550 . 
     That is, as shown in  FIG. 32A , the conversion unit  530  may be driven in the first step-down operation mode in which the first switch SW 1  is turned on and the second switch SW 2 , the third switch SW 3 , and the fourth switch SW 4  are turned off. 
     After the conversion unit  530  is driven in the first step-down operation mode, the conversion unit  530  may be driven in the third step-down operation mode in which the fourth switch SW 4  is turned on and the first switch SW 1 , the second switch SW 2 , and the third switch SW 3  are turned off, as shown in  FIG. 32B . 
     In addition, after the conversion unit  530  is driven in the third step-down operation mode, the conversion unit  530  may be driven in the second step-down operation mode in which the second switch SW 2  and the third switch SW 3  are turned on and the first switch SW 1  and the fourth switch SW 4  are turned off, as shown in  FIG. 32C . Accordingly, a current which flows to the output unit  550  (i.e., a load) is divided and transferred through a first current transfer path P 1  using the inductor I and a second current transfer path P 2  using the capacitor C. Therefore, an RMS value of the current flowing in the inductor I is reduced due to the additional current transfer path using the capacitor C. 
     As described above, since the current to be transferred to the output unit  550  (i.e., the load) is divided and transferred through two paths (first current transfer path and second current transfer path), an amount of power loss of the fifth step-down converter  500 - 1  according to the exemplary embodiment may be reduced as compared with the conventional step-down converter, thereby increasing power efficiency. 
     In addition, unlike the fourth step-down converter  400 - 1 , the fifth step-down converter  500 - 1  includes the fourth switch SW 4  which enables the third step-down operation mode. As such, the fifth step-down converter  500 - 1  has a power conversion ratio (V OUT /V IN ) ranging from 0 to 1, which is a range wider than that of the fourth step-down converter  400 - 1 . Furthermore, in the fifth step-down converter  500 - 1 , an RMS current flowing in the third switch SW 3  may be reduced as compared with the fourth step-down converter  400 - 1 , and an RMS current flowing in the capacitor C may be further reduced by adjusting a duty ratio of the first step-down operation mode Φ 1  and the second step-down operation mode Φ 3 . 
     A sixth step-down converter with a dual-path according to the exemplary embodiment will be described with reference to  FIGS. 33 to 35 . 
       FIG. 33  is a circuit diagram illustrating a configuration of the sixth step-down converter with the dual-path according to the exemplary embodiment.  FIGS. 34A and 34B  show diagrams for describing an example of a step-down operation mode of the sixth step-down converter shown in  FIG. 33 .  FIGS. 35A to 35C  show diagrams for describing another example of a step-down operation mode of the sixth step-down converter shown in  FIG. 33 . 
     Referring to  FIG. 33 , a sixth step-down converter  600 - 1  with a dual-path (hereinafter, referred to as a “sixth step-down converter”) according to the exemplary embodiment is configured by changing positions of some elements of the second step-down converter  200 - 1  and adding a fifth switch SW 5 . Here, a power conversion ratio (V OUT /V IN ) of the sixth step-down converter  600 - 1  is in the range of 0 to 1. 
     That is, a conversion unit  630  may include an inductor I, a capacitor C, a first switch SW 1 , a second switch SW 2 , a third switch SW 3 , a fourth switch SW 4 , and a fifth switch SW 5 . 
     One end of the inductor I is connected to a node between the first switch SW 1  and the fourth switch SW 4 , and the other end thereof is connected to a node between the fifth switch SW 5  and the capacitor C. 
     One end of the capacitor C is connected to a node between the inductor I and the fifth switch SW 5 , and the other end thereof is connected to a node between the second switch SW 2  and the third switch SW 3 . 
     One end of the first switch SW 1  is connected to an input unit  610 , and the other end thereof is connected to a node between the inductor I and the fourth switch SW 4 . 
     One end of the second switch SW 2  is connected to a node between the capacitor C and the third switch SW 3 , and the other end thereof is connected to a node between the fifth switch SW 5  and an output unit  650 . 
     One end of the third switch SW 3  is connected to a node between the capacitor C and the second switch SW 2 , and the other end thereof is connected to a node between the fourth switch SW 4  and the output unit  650 . 
     One end of the fourth switch SW 4  is connected to a node between the first switch SW 1  and the inductor I, and the other end thereof is connected to a node between the input unit  610  and the third switch SW 3 . 
     One end of the fifth switch SW 5  is connected to a node between the inductor I and the capacitor C, and the other end thereof is connected to a node between the output unit  650  and the second switch SW 2 . 
     More specifically, the conversion unit  630  may be driven in the order of a first step-down operation mode and a third step-down operation mode. That is, the conversion unit  630  may periodically perform an operation that sequentially includes the first step-down operation mode and the third step-down operation mode. As such, the conversion unit  630  may step down and transfer power input from the input unit  610  to the output unit  650 . 
     That is, as shown in  FIG. 34A , the conversion unit  630  may be driven in the first step-down operation mode in which the first switch SW 1  and the second switch SW 2  are turned on and the third switch SW 3 , the fourth switch SW 4 , and the fifth switch SW 5  are turned off. 
     After the conversion unit  630  is driven in the first step-down operation mode, the conversion unit  630  may be driven in the third step-down operation mode in which the first switch SW 1 , the third switch SW 3 , and the fifth switch SW 5  are turned on and the second switch SW 2  and the fourth switch SW 4  are turned off, as shown in  FIG. 34B . Accordingly, a current which flows to the output unit  650  (i.e., a load) is divided and transferred through a first current transfer path P 1  using the inductor I and a second current transfer path P 2  using the capacitor C. Therefore, an RMS value of the current flowing in the inductor I is reduced due to the additional current transfer path using the capacitor C. 
     Furthermore, the conversion unit  630  may be driven in the order of the first step-down operation mode and a second step-down operation mode. That is, the conversion unit  630  may periodically perform an operation that sequentially includes the first step-down operation mode and the second step-down operation mode. As such, the conversion unit  630  may step down and transfer power input from the input unit  610  to the output unit  650 . 
     That is, as shown in  FIG. 35A , the conversion unit  630  may be driven in the first step-down operation mode in which the first switch SW 1  and the second switch SW 2  are turned on and the third switch SW 3 , the fourth switch SW 4 , and the fifth switch SW 5  are turned off. 
     After the conversion unit  630  is driven in the first step-down operation mode, the conversion unit  630  may be driven in the second step-down operation mode in which the third switch SW 3 , the fourth switch SW 4 , the fifth switch SW 5  are turned on and the first switch SW 1  and the second switch SW 2  are turned off, as shown in  FIG. 35C . Accordingly, a current which flows to the output unit  650  (i.e., a load) is divided and transferred through a third current transfer path P 3  using the inductor I and a fourth current transfer path P 4  using the capacitor C. Therefore, an RMS value of the current flowing in the inductor I is reduced due to the additional current transfer path using the capacitor C. 
     According to an exemplary embodiment, the conversion unit  630  may be driven in the order of the first step-down operation mode, the third step-down operation mode, and a second step-down operation mode. That is, the conversion unit  630  may periodically perform an operation that sequentially includes the first step-down operation mode, the third step-down operation mode, and the second step-down operation mode. As such, the conversion unit  630  may step down and transfer power input from the input unit  610  to the output unit  650 . 
     That is, as shown in  FIG. 35A , the conversion unit  630  may be driven in the first step-down operation mode in which the first switch SW 1  and the second switch SW 2  are turned on and the third switch SW 3 , the fourth switch SW 4 , and the fifth switch SW 5  are turned off. 
     After the conversion unit  630  is driven in the first step-down operation mode, the conversion unit  630  may be driven in the third step-down operation mode in which the first switch SW 1 , the third switch SW 3 , the fifth switch SW 5  are turned on and the second switch SW 2  and the fourth switch SW 4  are turned off, as shown in  FIG. 35B . Accordingly, a current which flows to the output unit  650  (i.e., a load) is divided and transferred through a first current transfer path P 1  using the inductor I and a second current transfer path P 2  using the capacitor C. Therefore, an RMS value of the current flowing in the inductor I is reduced due to the additional current transfer path using the capacitor C. 
     In addition, after the conversion unit  630  is driven in the third step-down operation mode, the conversion unit  630  may be driven in the second step-down operation mode in which the third switch SW 3 , the fourth switch SW 4 , and the fifth switch SW 5  are turned on and the first switch SW 1  and the second switch SW 2  are turned off, as shown in  FIG. 35C . Accordingly, a current flowing to the output unit  650  (i.e., the load) is divided and transferred through a third current transfer path P 3  using the inductor I and a fourth current transfer path P 4  using the capacitor  2 . Therefore, an RMS value of the current flowing in the inductor I is reduced due to the additional current transfer path using the capacitor C. 
     A seventh step-down converter with a dual-path according to the exemplary embodiment will be described with reference to  FIG. 36 . 
       FIG. 36  is a circuit diagram illustrating a configuration of the seventh step-down converter with the dual-path according to the exemplary embodiment. 
     Since a seventh step-down converter  700 - 1  with a dual-path (hereinafter referred to as a “seventh step-down converter”) according to the exemplary embodiment is substantially the similar to the first step-down converter  100 - 1 , differences therebetween will be described. 
     Referring to  FIG. 36 , the seventh step-down converter  700 - 1  according to the exemplary embodiment further includes three switches and one capacitor added to the first step-down converter  100 - 1 . 
     Accordingly, in the seventh step-down converter  700 - 1  according to the exemplary embodiment, unlike the first step-down converter  100 - 1 , sections in which currents are supplied in parallel may be expanded to two phases according to the exemplary embodiment. 
     More specifically, a conversion unit  730  may be driven in the order of a first step-down operation mode Φ 1  and a second step-down operation mode Φ 2 . That is, the conversion unit  730  may periodically perform an operation that sequentially includes the first step-down operation mode Φ 1  and the second step-down operation mode Φ 2  and may step down and transfer power input from an input unit  710  to an output unit  750 . 
     That is, as shown in  FIG. 36 , the conversion unit  730  may be driven in the first step-down operation mode Φ 1  in which a current flowing to the output unit  750  (i.e., a load) is divided and transferred through a first current transfer path using a capacitor and a second current transfer path using at least one inductor and at least one capacitor. 
     After the conversion unit  730  is driven in the first step-down operation mode Φ 1 , the conversion unit  730  may be driven in the second step-down operation mode Φ 2 , as shown in  FIG. 36 . Accordingly, a current flowing to the output unit  750  (i.e., the load) is divided and transferred through a third current transfer path using a capacitor and an inductor and a fourth current transfer path using a switch. 
     As described above, in the seventh step-down converter  700 - 1  according to the exemplary embodiment, sections in which currents are supplied in parallel may be expanded to the step-down operation modes Φ 1  and Φ 2 , that is, two phases, unlike the first step-down converter  100 - 1 . 
     An eighth step-down converter with a dual-path according to the exemplary embodiment will be described with reference to  FIG. 37 . 
       FIG. 37  is a circuit diagram illustrating a configuration of the eighth step-down converter with the dual-path according to the exemplary embodiment. 
     Since an eighth step-down converter  800 - 1  with a dual-path (hereinafter referred to as an “eighth step-down converter”) according to the exemplary embodiment is substantially similar to the second step-down converter  200 - 1  according to the, differences therebetween will be described. 
     Referring to  FIG. 37 , the eighth step-down converter  800 - 1  according to the exemplary embodiment further includes three switches and one capacitor added to the second step-down converter  200 - 1 . 
     Accordingly, in the eighth step-down converter  800 - 1  according to the exemplary embodiment, sections in which currents are supplied in parallel may be expanded to two phases, unlike the second step-down converter  200 - 1 . 
     More specifically, a conversion unit  830  may be driven in the order of a first step-down operation mode Φ 1 , a third step-down operation mode Φ 2 , and a second step-down operation mode Φ 3 . That is, the conversion unit  830  may periodically perform an operation that sequentially includes the first step-down operation mode Φ 1 , the third step-down operation mode Φ 2 , and the second step-down operation mode Φ 2  and may step down and transfer power input from an input unit  810  to an output unit  850 . 
     That is, as shown in  FIG. 37 , the conversion unit  830  may be driven in the first step-down operation mode Φ 1 . Accordingly, a current which flows to the output unit  850  (i.e., a load) is divided and transferred through a first current transfer path using a capacitor and a second current transfer path using at least one inductor and at least one capacitor. 
     After the conversion unit  830  is driven in the first step-down operation mode Φ 1 , the conversion unit  630  may be driven in the third step-down operation mode Φ 2 , as shown in  FIG. 37 . Accordingly, a current which flows to the output unit  850  (i.e., the load) is divided and transferred through a third current transfer path using a capacitor and an inductor and a fourth current transfer path using a switch. 
     In addition, after the conversion unit  830  is driven in the third step-down operation mode Φ 2 , as shown in  FIG. 37 , the conversion unit  830  may be driven in the second step-down operation mode Φ 3 . Accordingly, a current which flows to the output unit  850  (i.e., the load) is transferred through a fifth current transfer path using an inductor. 
     As described above, in the eighth step-down converter  800 - 1  according to the exemplary embodiment, sections in which currents are supplied in parallel may be expanded to the first and third step-down operation modes Φ 1  and Φ 2 , that is, two phases, unlike the second step-down converter  200 - 1  according to the exemplary embodiment 
     A ninth step-down converter with a dual-path according to the exemplary embodiment will be described with reference to  FIG. 38 . 
       FIG. 38  is a circuit diagram illustrating a configuration of the ninth step-down converter with the dual-path according to the exemplary embodiment. 
     Since a ninth step-down converter  900 - 1  with a dual-path (hereinafter referred to as a “ninth step-down converter”) according to the exemplary embodiment is substantially similar to the fourth step-down converter  400 - 1 , differences therebetween will be described. 
     Referring to  FIG. 38 , the ninth step-down converter  900 - 1  according to the exemplary embodiment further includes three switches and one capacitor added to the fourth step-down converter  400 - 1 . 
     Accordingly, in the ninth step-down converter  900 - 1  according to the exemplary embodiment, sections in which currents are supplied in parallel may be expanded to two phases unlike the fourth step-down converter  400 - 1  according to the exemplary embodiment. 
     More specifically, a conversion unit  930  may be driven in the order of a first step-down operation mode Φ 1  and a second step-down operation mode Φ 2 . That is, the conversion unit  930  may periodically perform an operation that sequentially includes the first step-down operation mode Φ 1  and the second step-down operation mode Φ 2  and may step down and transfer power input from an input unit  910  to an output unit  950 . 
     That is, as shown in  FIG. 38 , the conversion unit  930  may be driven in the first step-down operation mode Φ 1 . Accordingly, a current which flows to the output unit  950  (i.e., a load) is divided and transferred through a first current transfer path using a capacitor and a second current transfer path using at least one inductor and at least one capacitor. 
     After the conversion unit  930  is driven in the first step-down operation mode Φ 1 , the conversion unit  930  may be driven in the second step-down operation mode Φ 2 , as shown in  FIG. 38 . Accordingly, a current which flows to the output unit  950  (i.e., the load) is divided and transferred through a third current transfer path using a capacitor and an inductor and a fourth current transfer path using a capacitor. 
     As described above, in the ninth step-down converter  900 - 1  according to the exemplary embodiment, sections in which currents are supplied in parallel may be expanded to step-down operation modes Φ 1  and Φ 2 , that is, two phases, unlike the fourth step-down converter  400 - 1 . 
     A tenth step-down converter with a dual-path according to the exemplary embodiment will be described with reference to  FIG. 39 . 
       FIG. 39  is a circuit diagram illustrating a configuration of the tenth step-down converter with the dual-path according to the exemplary embodiment. 
     Since a tenth step-down converter  1000 - 1  with a dual-path (hereinafter referred to as a “tenth step-down converter”) according to the exemplary embodiment is substantially similar to the fifth step-down converter  500 - 1 , differences therebetween will be described. 
     Referring to  FIG. 39 , the tenth step-down converter  1000 - 1  according to the exemplary embodiment further includes three switches and one capacitor added to the fifth step-down converter  500 - 1 . 
     Accordingly, in the tenth step-down converter  1000 - 1  according to the exemplary embodiment, sections in which currents are supplied in parallel may be expanded to two phases unlike the fifth step-down converter  500 - 1 . 
     More specifically, a conversion unit  1030  may be driven in the order of a first step-down operation mode Φ 1 , a third step-down operation mode Φ 2 , and a second step-down operation mode Φ 3 . That is, the conversion unit  1030  may periodically perform an operation that sequentially includes the first step-down operation mode Φ 1 , the third step-down operation mode Φ 2 , and the second step-down operation mode Φ 3  and may step down and transfer power input from an input unit  1010  to an output unit  1050 . 
     That is, as shown in  FIG. 39 , the conversion unit  1030  may be driven in the first step-down operation mode Φ 1 . Accordingly, a current which flows to the output unit  1050  (i.e., a load) is divided and transferred through a first current transfer path using a capacitor and a second current transfer path using at least one inductor and at least one capacitor. 
     After the conversion unit  1030  is driven in the first step-down operation mode Φ 1 , the conversion unit  1030  may be driven in the third step-down operation mode Φ 2 , as shown in  FIG. 39 . Accordingly, a current which flows to the output unit  1050  (i.e., the load) is transferred through a third current transfer path using an inductor. 
     In addition, after the conversion unit  1030  is driven in the third step-down operation mode Φ 2 , the conversion unit  1030  may be driven in the second step-down operation mode Φ 3 , as shown in  FIG. 39 . Accordingly, a current which flows to the output unit  1050  (i.e., the load) is divided and transferred through a fourth current transfer path using a capacitor and an inductor and a fifth current transfer path using a capacitor. 
     As described above, in the tenth step-down converter  1000 - 1  according to the exemplary embodiment, sections in which currents are supplied in parallel may be expanded to the first and second step-down operation modes Φ 1  and Φ 3 , that is, two phases, unlike the fifth step-down converter  500 - 1 . 
     An eleventh step-down converter with a triple-path according to the exemplary embodiment will be described with reference to  FIG. 40 . 
       FIG. 40  is a circuit diagram illustrating a configuration of the eleventh step-down converter with the triple-path according to the exemplary embodiment. 
     Referring to  FIG. 40 , an eleventh step-down converter  1100 - 1  with a triple-path (hereinafter, referred to as an “eleventh step-down converter”) according to the exemplary embodiment is configured by expanding the first step-down converter  100 - 1  so as to have three current transfer paths. Here, a power conversion ratio (V OUT /V IN ) of the eleventh step-down converter  1100 - 1  is in the range of 0.67 to 1. 
     That is, a conversion unit  1130  may include an inductor I, a first capacitor C 1 , a second capacitor C 2 , a first switch SW 1 , a second switch SW 2 , a third switch SW 3 , a fourth switch SW 4 , a fifth switch SW 5 , and a sixth switch SW 6 . 
     One end of the inductor I is connected to a node between the first switch SW 1  and the first capacitor C 1 , and the other end thereof is connected to a node between an output unit  1150  and the second switch SW 2 . 
     One end of the first capacitor C 1  is connected to a node between the first switch SW 1  and the inductor I, and the other end thereof is connected to a node between the second switch SW 2  and the third switch SW 3 . 
     One end of the second capacitor C 2  is connected to a node between the third switch SW 3  and the fourth switch SW 4 , and the other end thereof is connected to a node between the fifth switch SW 5  and the sixth switch SW 6 . 
     One end of the first switch SW 1  is connected to an input unit  1110 , and the other end thereof is connected to a node between the inductor I and the first capacitor C 1 . 
     One end of the second switch SW 2  is connected to a node between the first capacitor C 1  and the third switch SW 3 , and the other end thereof is connected to a node between the inductor I and the output unit  1150 . 
     One end of the third switch SW 3  is connected to a node between the first capacitor C 1  and the second switch SW 2 , and the other end thereof is connected to a node between the fourth switch SW 4  and the second capacitor C 2 . 
     One end of the fourth switch SW 4  is connected to a node between the input unit  1110  and the first switch SW 1 , and the other end thereof is connected to a node between the third switch SW 3  and the second capacitor C 2 . 
     One end of the fifth switch SW 5  is connected to a node between the second capacitor C 2  and the sixth switch SW 6 , and the other end thereof is connected to a node between the inductor I and the second switch SW 2 . 
     One end of the sixth switch SW 6  is connected to a node between the second capacitor C 2  and the fifth switch SW 5 , and the other end thereof is connected to a node between the input unit  1110  and the output unit  1150 . 
     More specifically, the conversion unit  1130  may be driven in the order of a first step-down operation mode Φ 1  and a second step-down operation mode Φ 2 . That is, the conversion unit  1130  may periodically perform an operation that sequentially includes the first step-down operation mode Φ 1  and the second step-down operation mode Φ 2  and may step down and transfer power input from the input unit  1110  to the output unit  1150 . In this case, a duty ratio indicating a driving time of the first step-down operation mode Φ 1  may be determined based on an input voltage, an output voltage, and the like. 
     That is, as shown in  FIG. 40 , the conversion unit  1130  may be driven in the first step-down operation mode Φ 1  in which the first switch SW 1 , the second switch SW 2 , the fourth switch SW 4 , and the fifth switch SW 5  are turned on and the third switch SW 3  and the sixth switch SW 6  are turned off. Accordingly, a current which flows to the output unit  1150  (i.e., a load) is divided and transferred through a triple-path including a first current transfer path using the first switch SW 1  and the inductor I, a second current transfer path using the first switch SW 1 , the first capacitor C 1 , and the second switch SW 2 , and a third current transfer path using the fourth switch SW 4 , the second capacitor C 2 , and the fifth switch SW 5 . Therefore, due to the additional two current transfer paths using the two capacitors C 1  and C 2 , an RMS value of the current flowing in the inductor I is further reduced as compared with a dual path structure. 
     After the conversion unit  1130  is driven in the first step-down operation mode Φ 1 , the conversion unit  1130  may be driven in the second step-down operation mode Φ 2  in which the third switch SW 3  and the sixth switch SW 6  are turned on and the first switch SW 1 , the second switch SW 2 , the fourth switch SW 4 , and the fifth switch SW 5  are turned off, as shown in  FIG. 40 . 
     A twelfth step-down converter with a triple-path according to the exemplary embodiment will be described with reference to  FIG. 41 . 
       FIG. 41  is a circuit diagram illustrating a configuration of the twelfth step-down converter with the triple-path according to the exemplary embodiment. 
     Referring to  FIG. 41 , a twelfth step-down converter  1200 - 1  with a triple-path (hereinafter, referred to as a “twelfth step-down converter”) according to the exemplary embodiment further includes a seventh switch SW 7  added to the eleventh step-down converter  1100 - 1 . 
     That is, a conversion unit  1230  includes an inductor I, a first capacitor C 1 , a second capacitor C 2 , a first switch SW 1 , a second switch SW 2 , a third switch SW 3 , a fourth switch SW 4 , a fifth switch SW 5 , a sixth switch SW 6 , and the seventh switch SW 7 . 
     One end of the seventh switch SW 7  is connected to a node between an input unit  1210  and the first switch SW 1 , and the other end thereof is connected to a node between the input unit  1210  and the sixth switch SW 6 . 
     More specifically, a conversion unit  1230  may be driven in the order of a first step-down operation mode Φ 1 , a third step-down operation mode Φ 2 , and a second step-down operation mode Φ 3 . That is, the conversion unit  1230  may periodically perform an operation that sequentially includes the first step-down operation mode Φ 1 , the third step-down operation mode Φ 2 , and the second step-down operation Φ 3  and may step down and transfer power input from the input unit  1210  to an output unit  1250 . 
     That is, as shown in  FIG. 41 , the conversion unit  1230  may be driven in the first step-down operation mode Φ 1  in which the first switch SW 1 , the second switch SW 2 , the fourth switch SW 4 , and the fifth switch SW 5  are turned on and the third switch SW 3 , the sixth switch SW 6 , and the seventh SW 7  are turned off. Accordingly, a current which flows to the output unit  1250  (i.e., a load) is divided and transferred through a first current transfer path using the first switch SW 1  and the inductor I, a second current transfer path using the first switch SW 1 , the first capacitor C 1 , and the second switch SW 2 , and a third current transfer path using the fourth switch SW 4 , the second capacitor C 2 , and the fifth switch SW 5 . Therefore, due to the additional two current transfer paths using the two capacitors C 1  and C 2 , an RMS value of the current flowing in the inductor I is further reduced as compared with a dual path structure. 
     After the conversion unit  1230  is driven in the first step-down operation mode Φ 1 , the conversion unit  1230  may be driven in the third step-down operation mode Φ 2  in which the first switch SW 1  and the seventh switch SW 7  are turned on and the second switch SW 2 , the third switch SW 3 , the fourth switch SW 4 , the fifth switch SW 5 , and the sixth switch SW 6  are turned off, as shown in  FIG. 41 . 
     In addition, after the conversion unit  1230  is driven in the third step-down operation mode Φ 2 , the conversion unit  1230  may be driven in the second step-down operation mode Φ 3  in which the third switch SW 3  and the sixth switch SW 6  are turned on and the first switch SW 1 , the second switch SW 2 , the fourth switch SW 4 , the fifth switch SW 5 , and the seventh switch SW 7  are turned off, as shown in  FIG. 41 . 
     As described above, unlike the eleventh step-down converter  1100 - 1  according to the exemplary embodiment, the twelfth step-down converter  1200 - 1  is driven in the third step-down operation mode by including the seventh switch SW 7  and thus has a power conversion ratio (V OUT /V IN ) ranging from 0 to 1, which is a range wider than that of the eleventh step-down converter  1100 - 1 . Furthermore, in the twelfth step-down converter  1200 - 1 , an RMS current flowing in the first switch SW 1  may be further reduced as compared with the eleventh step-down converter  1100 - 1 , and RMS currents flowing in two capacitors C 1  and C 2  may be further reduced by adjusting a duty ratio of the first step-down operation mode Φ 1  and the second step-down operation mode Φ 3 . 
     A thirteenth step-down converter having a multi-path according to the exemplary embodiment will be described with reference to  FIG. 42 . 
       FIG. 42  is a circuit diagram illustrating a configuration of the thirteenth step-down multi-path converter according to the exemplary embodiment. 
     Referring to  FIG. 42 , a thirteenth step-down converter  1300 - 1  having a multi-path (hereinafter, referred to as a “thirteenth step-down converter”) according to the exemplary embodiment is configured by expanding the first step-down converter  100 - 1  so as to have n current transfer paths. Here, a power conversion ratio (V OUT /V IN ) of the thirteenth step-down converter  1300 - 1  is in the range of (n−1)/n to 1. 
     A conversion unit  1330  may include n−1 capacitors and a plurality of switches. 
     More specifically, the conversion unit  1330  may be driven in the order of a first step-down operation mode Φ 1  and a second step-down operation mode Φ 2 . That is, the conversion unit  1330  may periodically perform an operation that sequentially includes the first step-down operation mode Φ 1  and the second step-down operation mode Φ 2  and may step down and transfer power input from an input unit  1310  to an output unit  1350 . 
     That is, as shown in  FIG. 42 , the conversion unit  1330  may be driven in the first step-down operation mode Φ 1 . Accordingly, a current which flows to the output unit  1350  (i.e., a load) is divided and transferred through multiple paths including a current transfer path using an inductor and n−1 current transfer paths using capacitors. Therefore, due to the additional n−1 current transfer paths using n−1 capacitors, an RMS value of the current flowing in the inductor I is further reduced. 
     After the conversion unit  1330  is driven in the first step-down operation mode Φ 1 , as shown in  FIG. 42 , the conversion unit  1330  may be driven in the second step-down operation mode Φ 2 . 
     A fourteenth step-down converter with multiple paths according to the exemplar embodiment of the present invention will be described with reference to  FIG. 43 . 
       FIG. 43  is a circuit diagram illustrating a configuration of the fourteenth step-down multi-path converter according to the exemplary embodiment. 
     Referring to  FIG. 43 , a fourteenth step-down converter  1400 - 1  with multiple paths (hereinafter, referred to as a “fourteenth step-down converter”) according to the exemplary embodiment further includes one switch added to the thirteenth step-down converter  1300 - 1 . 
     More specifically, a conversion unit  1430  may be driven in the order of a first step-down operation mode Φ 1 , a third step-down operation mode Φ 2 , and a second step-down operation mode Φ 3 . That is, the conversion unit  1430  may periodically perform an operation that sequentially includes the first step-down operation mode Φ 1 , the third step-down operation mode Φ 2 , and the second step-down operation mode Φ 3  and may step down and transfer power input from an input unit  1410  to an output unit  1450 . 
     That is, as shown in  FIG. 43 , the conversion unit  1430  may be driven in the first step-down operation mode Φ 1 . Accordingly, a current which flows to the output unit  1450  (i.e., a load) is divided and transferred through multiple paths including a current transfer path using an inductor and n−1 current transfer paths using capacitors. Therefore, due to the additional n−1 current transfer paths using n−1 capacitors, an RMS value of the current flowing in the inductor I is further reduced. 
     After the conversion unit  1430  is driven in the first step-down operation mode Φ 1 , the conversion unit  1430  may be driven in the third step-down operation mode Φ 2  as shown in  FIG. 43 . 
     In addition, after the conversion unit  1430  is driven in the third step-down operation mode Φ 2 , the conversion unit  1430  may be driven in the second step-down operation mode Φ 3 , as shown in  FIG. 43 , 
     As described above, unlike the thirteenth step-down converter  1300 - 1 , the fourteenth step-down converter  1400 - 1  is driven in the third step-down operation mode by including the additional switch. As such, the fourteenth step-down converter  1400 - 1  has a power conversion ratio (V OUT /V IN ) ranging from 0 to 1, which is a range wider than that of the thirteenth step-down converter  1300 - 1 . Furthermore, in the fourteenth step-down converter  1400 - 1 , an RMS current flowing in a first switch SW 1  may be further reduced as compared with the thirteenth step-down converter  1300 - 1 , and RMS currents flowing in the n−1 capacitors may be further reduced by adjusting a duty ratio of the first step-down operation mode Φ 1  and the second step-down operation mode Φ 3 . 
     Embodiment 2: Multi-Path Step-Up Converter 
     Hereinafter, a multi-path converter and a control method thereof according to the exemplary embodiments will be described in detail with reference to  FIGS. 44 to 58 . 
     The exemplary embodiments below relate to a multi-path converter which performs a function of a step-up converter configured to step up input power. That is, an output voltage V OUT  is higher than an input voltage V IN , and a current is divided and transferred to an output terminal through a plurality of current transfer paths (for example, two current transfer paths, three current transfer paths, or n current transfer paths) using at least one inductor and at least one capacitor. 
     First, a first step-up converter with a dual-path according to an exemplary embodiment will be described with reference to  FIGS. 44 to 48 . 
       FIG. 44  is a block diagram illustrating the first step-up converter with a dual-path according to the exemplary embodiment.  FIG. 45  is a circuit diagram illustrating a configuration of the first step-up converter shown in  FIG. 44 .  FIGS. 46A and 46B  show diagrams for describing an example of a step-up operation mode of the first step-up converter.  FIGS. 47A to 47C  show diagrams for describing another example of a step-up operation mode of the first step-up converter.  FIGS. 48A and 48B  illustrate inductor current change due to the step-up operation mode of the first step-up converter. 
     Referring to  FIG. 44 , a first step-up converter  100 - 2  with a dual-path (hereinafter, referred as a “first step-up converter) includes an input unit  110  to which power is input, a conversion unit  130  which steps up the input power, and an output unit  150  which receives and transfers the stepped-up power to an external device. 
     That is, the conversion unit  130  steps up the power input through the input unit  110  and transfers the stepped-up power to the output unit  150 . The conversion unit  130  transfers a current to the output unit  150  even while the input power is being stepped-up. 
     To this end, the conversion unit  130  may include a first conversion circuit unit  131  and a second conversion circuit unit  133 . 
     The first conversion circuit unit  131  steps up the power input through the input unit  110 . The first conversion circuit unit  131  transfers the stepped-up power to the output unit  150 . 
     Referring to  FIG. 45 , the first conversion circuit unit  131  may include an inductor I 1 , a first switch SW 1 , a second switch SW 2 , and a third switch SW 3 . 
     One end of the inductor I 1  is connected to an input unit  110 , and the other end thereof is connected to an output unit  150 . 
     The first switch SW 1  is disposed between the input unit  110  and the inductor I 1 . One end thereof is connected to the input unit  110 , and the other end thereof is connected to the inductor I 1 . 
     The second switch SW 2  is disposed between the inductor I 1  and the output unit  150 . One end thereof is connected to the inductor I 1 , and the other end thereof is connected to the output unit  150 . 
     One end of the third switch SW 3  is connected to a ground, and the other end thereof is connected to a node between the inductor I 1  and the second switch SW 2 . 
     The second conversion circuit unit  133  transfers a current to the output unit  150  while the first conversion circuit unit  131  steps up power. 
     Referring to  FIG. 45 , the second conversion circuit unit  133  may include a fourth switch SW 4 , a capacitor C 1 , and a fifth switch SW 5 . 
     One end of the fourth switch SW 4  is connected to the input unit  110 , and the other end thereof is connected to the fifth switch SW 5 . 
     One end of the capacitor C 1  is connected to a node between the fourth switch SW 4  and the fifth switch SW 5 , and the other end thereof is connected to a node between the first switch SW 1  and the inductor I 1 . 
     One end of the fifth switch SW 5  is connected to the fourth switch SW 4 , and the other end thereof is connected to the output unit  150 . 
     The above-described first step-up converter  100 - 2  exhibits characteristics of a step-up converter according to a duty ratio indicating a driving time of a first step-up operation mode. For example, when a duty ratio is “0,” a conversion ratio is “1,” and when the duty ratio is “1,” the conversion ratio is infinite. Thus, the first step-up converter  100 - 2  has the characteristics of the step-up converter. A current, which flows when the capacitor C 1  is connected parallel with the inductor I 1 , divides a current, which flows to the inductor I 1 , into two currents and reduces the current of the inductor I 1  by half as compared with a conventional step-up converter. In addition, a conduction loss is increased in the form of a square of a current, so when the current is reduced by half, the conduction loss is reduced to ¼, thereby increasing efficiency. 
     In addition, in the first step-up converter  100 - 2 , a switch may be designed as a low withstanding voltage element, thereby further reducing an overlap loss caused by a switching node. 
     More specifically, the conversion unit  130  may be driven in the order of a first step-up operation mode and a second step-up operation mode. 
     That is, as shown in  FIG. 46A , the conversion unit  130  may be driven in the first step-up operation mode in which the first switch SW 1 , the third switch SW 3 , and the fifth switch SW 5  are turned on and the second switch SW 2  and the fourth switch SW 4  are turned off. Accordingly, the conversion unit  130  may step up power input through the input unit  110  using the inductor I 1  and may transfer a current to the output unit  150  while stepping up the power. 
     After the conversion unit  130  is driven in the first step-up operation mode, as shown in  FIG. 46B , the conversion unit  130  may be driven in the second step-up operation mode in which the second switch SW 2  and the fourth switch SW 4  are turned on and the first switch SW 1 , the third switch SW 3 , and the fifth switch SW 5  are turned off. The conversion unit  130  may transfer the stepped-up power to the output unit  150 . 
     As described above, while the current of the inductor I 1  is built-up in the first step-up operation mode, a current is transferred to an output terminal through a path including the capacitor C 1 . In the second step-up operation mode, the inductor I 1  and capacitor C 1  are connected in series to transfer a current to the output terminal. Accordingly, in the first step-up converter  100 - 2 , since a current is transferred to the output terminal in all modes, the output current may be continuous. Accordingly, an RMS value of the current in the inductor may be further reduced as compared with a conventional step-up converter, and a ripple and switching noise of an output voltage may be greatly reduced. 
     On the other hand, when a duty ratio indicating a driving time of the first step-up operation mode is greater than a preset value (for example, “0.5” or the like), the conversion unit  130  may be driven in the order of the first step-up operation mode and the second step-up operation mode and may step up the power input through the input unit  110  to transfer the stepped-up power to the output unit  150 . The conversion unit  130  may transfer a current to the output unit  150  even while the input power is stepped-up. 
     Meanwhile, when the duty ratio indicating the driving time of the first step-up operation mode is less than the preset value (for example, “0.5” or the like), the conversion unit  130  may be driven in the order of the first step-up operation mode, a third step-up operation mode, and the second step-up operation mode. 
     That is, as shown in  FIG. 47A , the conversion unit  130  may be driven in the first step-up operation mode in which the first switch SW 1 , the third switch SW 3 , and the fifth switch SW 5  are turned on and the second switch SW 2  and the fourth switch SW 4  are turned off. 
     After the conversion unit  130  is driven in the first step-up operation mode, the conversion unit  130  may be driven in the third step-up operation mode in which the first switch SW 1 , the second switch SW 2 , and the fifth switch SW 5  are turned on and the third switch SW 3  and the fourth switch SW 4  are turned off, as shown in  FIG. 47B . 
     After the conversion unit  130  is driven in the third step-up operation mode, the conversion unit  130  may be driven in the second step-up operation mode in which the second switch SW 2  and the fourth switch SW 4  are turned on and the first switch SW 1 , the third switch SW 3 , and the fifth switch SW 5  are turned off, as shown in  FIG. 47C . 
     Here, when the conversion unit  130  is driven in the order of the first step-up operation mode, the third step-up operation mode, and the second step-up operation mode, the conversion unit  130  may be driven in the second step-up operation mode for a preset time (for example, duty ratio of “0.5” or the like). For example, when a preset value used as a reference for a duty ratio comparison is “0.5” and a duty ratio is “0.3,” the duty ratio is less than the preset value. Accordingly, the conversion unit  130  is driven in the order of the first step-up operation mode, the third step-up operation mode, and the second step-up operation mode. In this case, in order to maintain a driving time of the second step-up operation mode at “0.5” which is a preset time, the conversion unit  130  is driven in the first step-up operation mode for a time of “0.3,” the third step-up operation mode for a time of “0.2,” and the second step-up operation mode for a time of “0.5.” 
     As described above, when the duty ratio indicating the driving time of the first step-up operation mode is less than the preset value (for example, “0.5” or the like), the conversion unit  130  may be driven in the third step-up operation mode between the first step-up operation mode and the second step-up operation mode, and thus, a time for supplying a current to the capacitor C 1  may be extended. Accordingly, a negative effect on efficiency which is caused when a large amount of current is supplied within a short time may be prevented. 
     Accordingly, in the first step-up converter  100 - 2  according to another exemplary embodiment, since a current is transferred to the output terminal in all modes, a continuous output current may be exhibited. Accordingly, an RMS value of the current in the inductor may be further reduced as compared with the conventional step-up converter, and a ripple and switching noise of an output voltage may be greatly reduced. 
     In other words, when the duty ratio indicating the driving time of the first step-up operation mode is greater than the preset value (for example, “0.5” or the like), the conversion unit  130  may be driven in the order of a first step-up operation mode D 1  and a second step-up operation mode D 2 , as shown in  FIG. 48A . 
     When the duty ratio indicating the driving time of the first step-up operation mode is less than the preset value (for example, “0.5” or the like), the conversion unit  130  may be driven in the order of the first step-up operation mode D 1 , a third step-up operation mode D 3 , and the second step-up operation mode D 2 , as shown in  FIG. 48B . 
     Performance of the first step-up converter according to an exemplary embodiment will be described with reference to  FIGS. 49 to 52 . 
       FIG. 49  shows graphs each obtained by testing the first step-up converter according to the exemplary embodiment in an environment with a duty ratio of 0.5.  FIG. 50  shows graphs each obtained by testing the first step-up converter according to the exemplary embodiment in an environment with a duty ratio of 0.7.  FIG. 51  shows graphs each obtained by testing the first step-up converter according to the exemplary embodiment in an environment with a duty ratio of 0.4.  FIG. 52  shows graphs each obtained by testing the first step-up converter according to the exemplary embodiment in an environment with a duty ratio of 0.2. 
     Referring to  FIG. 49 , it can be confirmed that an average of the current in the inductor of the first step-up converter  100 - 2  according to the exemplary embodiment is reduced by about half of that of the conventional step-up converter. Unlike the conventional step-up converter in which a current flowing to an output terminal had discontinuity, in the first step-up converter  100 - 2  according to the exemplary embodiment, it may be confirmed that a current (I OUT ) flowing to an output terminal does not drop to zero and has continuity. As a result, a ripple of an output voltage is considerably reduced as compared with the conventional step-up converter. Therefore, performance of a load connected to the output terminal of the first step-up converter  100 - 2 , that is, performance of a block using a high voltage formed by the first step-up converter  100 - 2 , may be prevented from decreasing. 
     Referring to  FIGS. 50 to 52 , it can be confirmed that the first step-up converter  100 - 2  according to the exemplary embodiment shows better performance than the conventional converter. 
     A control method of the first step-up converter with the dual-path according to the exemplary embodiment will be described with reference to  FIGS. 53 and 54 . 
       FIG. 53  is a flowchart illustrating the control method of the first step-up converter with the dual-path according to the exemplary embodiment. 
     Referring to  FIG. 53 , the first step-up converter  100 - 2  steps up input power and transfers a current to the output unit while stepping up the input power (S 110 - 2 ). That is, the first step-up converter  100 - 2  may be driven in a first step-up operation mode in which the first switch SW 1 , the third switch SW 3 , and the fifth switch SW 5  are turned on and the second switch SW 2  and the fourth switch SW 4  are turned off. 
     Then, the first step-up converter  100 - 2  transfers the stepped-up power to the output unit (S 130 - 2 ). That is, after the first step-up converter  100 - 2  is driven in the first step-up operation mode, the first step-up converter  100 - 2  may be driven in a second step-up operation mode in which the second switch SW 2  and the fourth switch SW 4  are turned on and the first switch SW 1 , the third switch SW 3 , and the fifth switch SW 5  are turned off. 
       FIG. 54  is a flowchart illustrating a stepped-up power transferring operation shown in  FIG. 53  in more detail. 
     Referring to  FIG. 54 , when a duty ratio is greater than a preset value (Yes in operation S 131 ), the first step-up converter  100 - 2  may be driven in the second step-up operation mode (S 133 ). That is, when a duty ratio indicating a driving time of the first step-up operation mode is greater than the preset value (for example, “0.5” or the like), the first step-up converter  100 - 2  may be driven in the second step-up operation mode. 
     Meanwhile, when the duty ratio is less than the preset value (No in operation S 131 ), the first step-up converter  100 - 2  may be driven in a third step-up operation mode (S 135 ). That is, when the duty ratio indicating a driving time of the first step-up operation mode is less than the preset value (for example, duty ratio of “0.5” or the like), the first step-up converter  100 - 2  may be driven in the third step-up operation mode in which the first switch SW 1 , the second switch SW 2 , and the fifth switch SW 5  are turned on and the third switch SW 3  and the fourth switch SW 4  are turned off. 
     Next, the first step-up converter  100 - 2  may be driven in the second step-up operation mode (S 137 ). In this case, the first step-up converter  100 - 2  may be driven in the second step-up operation mode for a preset time (for example, duty ratio of “0.5” or the like). 
     A second step-up converter with dual paths according to an embodiment will be described with reference to  FIGS. 55 and 56 . 
       FIG. 55  is a diagram illustrating an example of a configuration and a step-up operation mode of the second step-up converter with the dual-path according to the exemplary embodiment, and  FIG. 56  is a diagram illustrating another example of a step-up operation mode of the second step-up converter shown in  FIG. 55 . 
     Since a second step-up converter  200 - 2  with a dual-path (hereinafter referred to as a “second step-up converter”) according to the exemplary embodiment is substantially similar to the first step-up converter  100 - 2 , differences therebetween will be described. 
     Referring to  FIGS. 55 and 56 , the second step-up converter  200 - 2  according to the exemplary embodiment is configured by changing positions of some elements of the first step-up converter  100 - 2 . 
     That is, a conversion unit  230  may include an inductor I 1 , a capacitor C 1 , a first switch SW 1 , a second switch SW 2 , a third switch SW 3 , a fourth switch SW 4 , and a fifth switch SW 5 . 
     One end of the inductor I 1  is connected to an input unit  210 , and the other end thereof is connected to a node between the second switch SW 2  and the third switch SW 3 . 
     One end of the capacitor C 1  is connected to a node between the first switch SW 1  and the fourth switch SW 4 , and the other end thereof is connected to a node between the third switch SW 3  and the fifth switch SW 5 . 
     One end of the first switch SW 1  is connected to a node between the input unit  210  and the inductor I 1  and the other end thereof is connected to a node between the fourth switch SW 4  and the capacitor C 1 . 
     One end of the second switch SW 2  is connected to a node between the inductor I 1  and the third switch SW 3 , and the other end thereof is connected to a node between the input unit  210  and an output unit  250 . 
     One end of the third switch SW 3  is connected to a node between the inductor I 1  and the second switch SW 2 , and the other end thereof is connected to a node between the capacitor C 1  and the fifth switch SW 5 . 
     One end of the fourth switch SW 4  is connected to a node between the first switch SW 1  and the capacitor C 1 , and the other end thereof is connected to a node between the output unit  250  and the fifth switch SW 5 . 
     One end of the fifth switch SW 5  is connected to a node between the capacitor C 1  and the third switch SW 3 , and the other end thereof is connected to the output unit  250 . 
     The conversion unit  230  may be driven in the order of a first step-up operation mode Φ 2  and a second step-up operation mode Φ 2 . 
     That is, as shown in  FIG. 55 , the conversion unit  230  may be operated in the first step-up operation mode Φ 1  in which the first switch SW 1 , the second switch SW 2 , and the fifth switch SW 5  are turned on and the third switch SW 3  and the fourth switch SW 4  are turned off. Accordingly, the conversion unit  230  may step up power input through the input unit  210  using the inductor I 1  and may transfer a current to the output unit  250  while stepping up the power. 
     After the conversion unit  230  is driven in the first step-up operation mode Φ 1 , the conversion unit  230  may be driven in the second step-up operation mode Φ 2  in which the third switch SW 3  and the fourth switch SW 4  are turned on and the first switch SW 1 , the second switch SW 2 , and the fifth switch SW 5  are turned off, as shown in  FIG. 55 . Therefore, the conversion unit  230  may transfer the stepped-up power to the output unit  250 . 
     As described above, while the current of the inductor I 1  is built-up in the first step-up operation mode Φ 1 , a current is transferred to an output terminal through a path including the capacitor C 1 . In the second step-up operation mode Φ 2 , a current is transferred to the output terminal through the inductor I 1  and capacitor C 1  connected in series. Accordingly, in the second step-up converter  200 - 2  according to the exemplary embodiment, a current is transferred to the output terminal in all modes, so a continuous output current is exhibited. 
     On the other hand, the conversion unit  230  may be driven in the order of a first step-up operation mode Φ 1 , a third step-up operation mode Φ 2 , and a second step-up operation mode Φ 3 . 
     That is, as shown in  FIG. 56 , the conversion unit  230  may be operated in the first step-up operation mode Φ 1  in which the first switch SW 1 , the second switch SW 2 , and the fifth switch SW 5  are turned on and turning the third switch SW 3  and the fourth switch SW 4  are turned off. Accordingly, the conversion unit  230  may step up power input through the input unit  210  using the inductor I 1  and may transfer a current to the output unit  250  while stepping up the power. 
     After the conversion unit  230  is driven in the first step-up operation mode Φ 1 , the conversion unit  230  may be driven in the third step-up operation mode Φ 2  in which the first switch SW 1 , the third switch SW 3 , and the fifth switch SW 5  are turned on and the second switch SW 2  and the fourth switch SW 4  are turned off, as shown in  FIG. 56 . 
     After the conversion unit  230  is driven in the third step-up operation mode Φ 2 , the conversion unit  230  may be driven in the second step-up operation mode Φ 3  in which the third switch SW 3  and the fourth switch SW 4  are turned on and the first switch SW 1 , the second switch SW 2 , and the fifth switch SW 5  are turned off as shown in  FIG. 56 . Therefore, the conversion unit  230  may transfer the stepped-up power to the output unit  250 . 
     As described above, the conversion unit  230  may be driven in the third step-up operation mode Φ 2  between the first step-up operation mode Φ 1  and the second step-up operation mode Φ 3 , and thus, a time for supplying a current to the capacitor C 1  may be extended. Accordingly, an adverse effect on efficiency which is caused when a large amount of current is supplied within a short time may be prevented. 
     Accordingly, in the second step-up converter  200 - 2  according to the exemplary embodiment, a current is transferred to the output terminal in all modes. As a result, a output current may be continuous. Accordingly, an RMS value of the current in the inductor may be further reduced as compared with the conventional step-up converter, and a ripple and switching noise of an output voltage may be greatly reduced. 
     A third step-up converter with a multi-path according to the exemplary embodiment will be described with reference to  FIG. 57 . 
       FIG. 57  is a circuit diagram illustrating a configuration of the third step-up multi-path converter according to the exemplary embodiment. 
     Referring to  FIG. 57 , a third step-up converter  300 - 2  with multiple paths (hereinafter, referred to as a “third step-up converter”) according to an embodiment is configured by expanding the second step-up converter  200 - 1  so as to have n current transfer paths. 
     More specifically, a conversion unit  330  may be driven in the order of a first step-up operation mode Φ 1  and a second step-up operation mode Φ 2 . 
     That is, as shown in  FIG. 57 , the conversion unit  330  may be driven in the first step-up operation mode Φ 1 . Accordingly, the conversion unit  330  may step up power input through an input unit  310  using an inductor I 1  and may transfer a current to an output unit  350  through n current transfer paths using n capacitors while stepping up the power. 
     After the conversion unit  330  is driven in the first step-up operation mode Φ 1 , the conversion unit  330  may be driven in the second step-up operation mode Φ 2 , as shown in  FIG. 57 . Therefore, the conversion unit  330  may transfer the stepped-up power to the output unit  350 . 
     A fourth step-up converter with a multi-path according to an exemplary embodiment will be described with reference to  FIG. 58 . 
       FIG. 58  is a circuit diagram illustrating a configuration of the fourth step-up multi-path converter according to the exemplary embodiment. 
     Referring to  FIG. 58 , a fourth step-up converter  400 - 2  with multiple paths (hereinafter, referred to as a “fourth step-up converter”) according to the embodiment is configured by expanding the first step-up converter  100 - 1  to have n current transfer paths. 
     More specifically, a conversion unit  430  may be driven in the order of a first step-up operation mode Φ 1  and a second step-up operation mode Φ 2 . 
     That is, as shown in  FIG. 58 , the conversion unit  430  may be driven in the first step-up operation mode Φ 1 . Accordingly, the conversion unit  430  may step up power input through an input unit  410  using an inductor I 1  and may transfer a current to an output unit  450  through n current transfer paths using n capacitors while stepping up the power 
     After the conversion unit  430  is driven in the first step-up operation mode Φ 1 , the conversion unit  430  may be driven in the second step-up operation mode Φ 2 , as shown in  FIG. 58 . Therefore, the conversion unit  430  may transfer the stepped-up power to the output unit  450 . 
       FIGS. 59A and 59B  show diagrams for describing an example in which the second step-down converter shown in  FIG. 21  is operated in a single-path manner. Referring to  FIGS. 21 and 59 , when the second step-down converter is operated in the single-path manner, the conversion unit  230  may be driven in the order of the fourth step-down operation mode and the fifth step-down operation mode. That is, the conversion unit  230  may periodically perform an operation that sequentially includes the fourth step-down operation mode and the fifth step-down operation mode and may step down power input from the input unit  210  and transfer the stepped-down power to the output unit  250 . 
     That is, as shown in  FIG. 59A , the conversion unit  230  may be driven in the fourth-down operation mode in which a first switch SW 1  is turned on and second to fourth switches SW 2  to SW 4  are turned off. Accordingly, a current flowing to the output unit  250  is transferred through a first current transfer path P 1  using an inductor I. That is, when the conversion unit  230  is driven in the fourth step-down operation mode, the current is transferred to the output unit  250  through a single current transfer path. 
     After the conversion unit  230  is driven in the fourth-down operation mode, the conversion unit  230  may be driven in the fifth step-down operation mode in which the fourth switch SW 4  is turned on and the first to third switches SW 1  to SW 3  are turned off, as shown in  FIG. 59B . 
     As described above, when the conversion unit  230  is operated in the single-path manner, the current is transferred to the output unit  250  through the single current transfer path P 1  in the same manner as in a conventional step-down converter. In the following description, for convenience of description, a manner in which a current is transferred to an output unit through a plurality of parallel current transfer paths that are the same as in the manner shown in  FIGS. 22A to 22C  will be referred to as a multi-path manner. 
       FIG. 60  is a graph showing efficiencies when the second step-down converter shown in  FIG. 21  is operated in the multi-path manner (see  FIGS. 22A to 22C ) and the single-path manner (see  FIGS. 59A and 59B ). Referring to  FIG. 60 , the efficiency of the multi-path manner (e.g., dual-path step-down converter (DPNC)) is generally higher than the efficiency of the single-path manner (e.g., conventional buck converter topology (CBT)). However, when a current I LOAD  in a load is low (for example, 0.2 A), the efficiency of the single-path manner is higher than the efficiency of the multi-path manner. Therefore, when the current I LOAD  in the load is high, the second step-down converter may be operated in the multi-path manner, and when the current I LOAD  in the load is low, the second step-down converter may be operated in the single-path manner. In this way, it is possible to increase the overall efficiency of the second step-down converter. 
       FIG. 61  is a flowchart for describing a step-down converting method according to the first exemplary embodiment. Referring to  FIG. 61 , the step-down converting method includes operating a step-down converter including a power source, an inductor, a capacitor, and a load in a multi-path manner (S 611 ) and operating the step-down converter in a single-path manner (S 612 ). Operation S 611  of the operating in the multi-path manner is illustrated in the drawing as being performed prior to operation S 612  of the operating in the single-path manner, but operation S 611  of the operating in the multi-path manner may be performed after operation S 612  of the operating in the single-path manner. In addition, after operation S 611  of the operating in the multi-path manner and operation S 612  of the operating in the single-path manner are performed, operation S 611  of the operating in the multi-path manner and operation S 612  of the operating in the single-path manner may be repeated once or more. 
     Hereinafter, the step-down converting method shown in  FIG. 61  will be described with reference to the second step-down converter shown in  FIG. 21 . Operation S 611  of the operating in the multi-path manner may be performed in order of, for example, the first step-down operation mode (see  FIG. 22A ), the third step-down operation mode (see  FIG. 22B ), and the second step-down operation mode (see  FIG. 22C ). In addition, operation S 611  of the operating in the multi-path manner may include, for example, the first step-down operation mode (see  FIG. 22A ) and the second step-down operation mode (see  FIG. 22C ). Operation S 612  of the operating in the single-path manner may be performed in order of, for example, the fourth step-down operation mode (see  FIG. 59A ) and the fifth step-down operation mode (see  FIG. 59B ). 
     A current I LOAD  flowing in a load in operation S 611  of the operating in the multi-path manner may be higher than the current I LOAD  flowing in the load in operation S 612  of the operating in the single-path manner. For example, when the current I LOAD  in the load is more than a certain value, operation S 611  of the operating in the multi-path manner may be performed, and when the current I LOAD  in the load is less than a certain value, operation S 612  of the operating in the single-path manner may be performed. When the current  ILOAD  is equal to the certain value, any one of operation S 612  of the operating in the single-path manner and operation S 611  of the operating in the multi-path manner may be performed. The certain value may be, for example, a value of the current I LOAD  in the load at an intersection point between the efficiency of the multi-path manner (DPNC) and the efficiency of the single-path manner (CBT) of  FIG. 60  or may be a certain value of a current which is adjacent to the intersection point. For example, when the current I LOAD  in the load is changed from less than a first certain value to more than the first certain value, operation S 611  of the operating in the multi-path manner may be performed, and when the current I LOAD  in the load is changed from more than a second certain value to less than the second certain value, operation S 612  of the operating in the single-path manner may be performed. In this case, the first certain value may be greater than the second certain value. As described above, hysteresis may be provided to prevent frequent switching between operation S 611  of the operating in the multi-path manner and operation S 612  of the operating in the single-path manner. 
     In general, a current I LOAD  flowing in a load is related with an operation mode of an electronic system (not shown, for example, a portable electronic device such as a smartphone or a laptop computer, or a stationary electronic device such as a personal computer or a display) including a step-down converter. Accordingly, one of operation S 611  of the operating in the multi-path manner and operation S 612  of the operating in the single-path manner may be performed according to the operation mode of the electronic system. For example, when the electronic system is in a normal operation mode or a maximum performance mode, the current I LOAD  flowing in the load has a high value. When the electronic system is in a power saving mode or an idle mode, the current I LOAD  flowing in the load has a low value. Therefore, when the electronic system is in the normal operation mode or the maximum performance mode, operation S 611  of the operating in the multi-path manner may be performed. When the electronic system is in the power saving mode or the idle mode, operation S 612  of the operating in the single-path manner may be performed. In other words, operation S 611  of the operating in the multi-path manner may be performed when the electronic system is operated in the normal operation mode or the maximum performance mode. On the other hand, operation S 612  of the operating in the single-path manner may be performed when the electronic system is operated in the power saving mode or the idle mode. 
     In addition, the current I LOAD  flowing in the load is related with an execution function (e.g., audio output, video output, cellular communication, Wi-Fi communication, etc.) of the electronic system. Accordingly, one of operation S 611  of the operating in the multi-path manner and operation S 612  of the operating in the single-path manner may be performed according to the execution function of the electronic system. For example, when the electronic system performs the video output function, the current I LOAD  flowing in the load may have a high value. When the electronic system performs the audio output function, the current I LOAD  flowing in the load may have a low value. Accordingly, when the electronic system performs the video output function, operation S 611  of the operating in the multi-path manner may be performed. When the electronic system performs the audio output function, operation S 612  of the operating in the single-path manner may be performed. In other words, the electronic system performs the video output function in operation S 611  of the operating in the multi-path manner. The electronic system performs the audio output function in operation S 612  of the operating in the single-path manner. For another example, when the electronic system performs video output function, audio output function and the like, operation S 611  of the operating in the multi-path manner may be performed. When the electronic system does not perform such functions, operation S 612  of the operating in the single-path manner may be performed. For the same reason as described above, one of operation S 611  of the operating in the multi-path manner and operation S 612  of the operating in the single-path manner may be performed according to a combination of the execution functions of the electronic system. 
     While the step-down converting method of  FIG. 61  has been described with reference to the second step-down converter shown in  FIG. 21 , the step-down converting method may be applicable to step-down converters with a plurality of various transfer paths. For example, the step-down converting method of the third step-down converter (see  FIG. 26 ) may also include operating the third step-down converter in the multi-path manner (S 611 ) and operating the third step-down converter in the single-path manner (S 612 ). Operation S 611  of the operating in the multi-path manner may be performed in the order of the first step-down operation mode (see  FIG. 27A ) and the second step-down operation mode (see  FIG. 27B ). Operation S 612  of the operating in the single-path manner may be performed in the order of the fourth step-down operation mode (in which the first switch SW 1  is turned on and the second to sixth switches SW 2  to SW 6  are turned off in the third step-down converter of  FIG. 26 ) and the fifth step-down operation mode (in which the fourth to sixth switches SW 4  to SW 6  are turned on and the first to third switches SW 1  to SW 3  are turned off in the third step-down converter of  FIG. 26 ). 
     For example, the step-down converting method of the fifth step-down converter (see  FIG. 31 ) may also including operating the fifth step-down converter in the multi-path manner (S 611 ) and operating the fifth step-down converter in the single-path manner (S 612 ). Operation S 611  of the operating in the multi-path manner may be performed in the order of the first step-down operation mode (see  FIG. 32A ), the third step-down operation mode (see  FIG. 32B ), and the second step-down operation mode (see  FIG. 32C ). Operation S 612  of the operating in the single-path manner may include the fourth step-down operation mode (in which the fourth switch SW 4  is turned on and the first to third switches SW 1  to SW 3  are turned off in the fifth step-down converter of  FIG. 31 ) and the fifth step-down operation mode (in which the third switch SW 3  is turned on and the first, second, and fourth switches SW 1 , SW 2 , and SW 4  are turned off in the fifth step-down converter of  FIG. 31 ). 
     For example, the step-down converting method of the sixth step-down converter (see  FIG. 33 ) may also include operating the sixth step-down converter in the multi-path manner (S 611 ) and operating the sixth step-down converter in the single-path manner (S 612 ). Operation S 611  of the operating in the multi-path manner may be performed in the order of the first step-down operation mode (see  FIG. 35A ), the third step-down operation mode (see  FIG. 35B ), and the second step-down operation mode (see  FIG. 35C ). Alternatively, operation S 611  of the operating in the multi-path manner may be performed in the order of the first step-down operation mode (see  FIG. 35A ), and the second step-down operation mode (see  FIG. 35C ). Also, operation S 611  of the operating in the multi-path manner may be performed in the order of the first step-down operation mode (see  FIG. 34A ), and the third step-down operation mode (see  FIG. 34B ). Operation S 612  of the operating in the single-path manner may include the fourth step-down operation mode (in which the first and fifth switches SW 1  and SW 5  are turned on and the second to fourth switches SW 2  to SW 4  are turned off in the sixth step-down converter of  FIG. 33 ) and the fifth step-down operation mode (in which the fourth and fifth switches SW 4  and SW 5  are turned on and the first to third switches SW 1  to SW 3  are turned off in the sixth step-down converter of  FIG. 33 ). 
     By referencing the above-described contents, those skilled in the art may understand that other step-down converters shown in the drawings may also be operated in the single path manner, and thus detailed descriptions thereof will be omitted for convenience of description. In addition, in the case of the exemplary embodiment (see  FIG. 10 ) including the conventional converter module  10  and the conversion unit  130  with a plurality of parallel current transfer paths, operation S 611  of the operating in the multi-path manner may be performed using the conversion unit  130  with the plurality of parallel current transfer paths, and operation S 612  of the operating in the single-path manner may be performed using the conventional converter module  10 . 
       FIG. 62  is a graph showing efficiencies when the second step-down converter shown in  FIG. 21  is operated in a two-phase manner and a three-phase manner. Here, the second step-down converter being operated in the two-phase manner means that the second step-down converter periodically performs an operation that sequentially includes the first step-down operation mode (see  FIG. 22A ) and the second step-down operation mode (see  FIG. 22C ). In addition, the second step-down converter being operated in the three-phase manner means that the second step-down converter periodically performs an operation that sequentially includes the first step-down operation mode (see  FIG. 22A ), the third step-down operation mode (see  FIG. 22B ), and the second step-down operation mode (see  FIG. 22C ). Referring to  FIG. 62 , when a ratio (V OUT /V IN ) of an output voltage to an input voltage is high, the efficiency of the two-phase manner (DPNC-2Φ Mode) is higher than the efficiency of the three-phase manner (DPNC-3Φ Mode). In addition, when the ratio (V OUT /V IN ) of the output voltage to the input voltage is low, the efficiency of the three-phase manner (DPNC-3Φ Mode) is higher than the efficiency of the two-phase manner (DPNC-2ΦMode). Therefore, when the ratio (V OUT /V IN ) of the input voltage to the output voltage is high, the second step-down converter may be operated in the two-phase manner, and when the ratio (V OUT /V IN ) of the input voltage to the output voltage is low, the second step-down converter may be operated in the three-phase manner. In this way, it is possible to increase the overall efficiency of the second step-down converter. 
       FIG. 63  is a flowchart for describing a step-down converting method according to a second exemplary embodiment. Referring to  FIG. 63 , the step-down converting method includes operating a step-down converter including a power source, an inductor, a capacitor, and a load in a two-phase manner (S 631 ) and operating the step-down converter in a three-phase manner (S 632 ).  FIG. 63  shows that operation S 631  of the operating in the two-phase manner is performed prior to operation S 632  of the operating in the three-phase manner, but operation S 631  of the operating in the two-phase manner may be performed after operation S 632  of the operating in the three-phase manner. In addition, after operation S 631  of the operating in the two-phase manner and operation S 632  of the operating in the three-phase manner are performed, operation S 631  of the operating in the two-phase manner and operation S 632  of the operating in the three-phase manner may be repeated once or more. Operation S 631  of the operating in the two-phase manner may include driving the step-down converter in a first step-down operation mode (S 633 ) and driving the step-down converter in a second step-down operation mode (S 634 ). In addition, operation S 632  of the operating in the three-phase manner may include driving the step-down converter in the first step-down operation mode (S 633 ), driving the step-down converter in a third step-down operation mode (S 635 ), and driving the step-down converter in the second step-down operation mode (S 634 ). 
     Hereinafter, the step-down converting method shown in  FIG. 63  will be described with reference to the second step-down converter shown in  FIG. 21 . Operation S 631  of the operating in the two-phase manner may include driving the step-down converter in the first step-down operation mode (see  FIG. 22A ) (S 633 ) and driving the step-down converter in the second step-down operation mode (see  FIG. 22C ) (S 634 ). In addition, operation S 632  of the operating in the three-phase manner may include driving the step-down converter in the first step-down operation mode (see  FIG. 22A ) (S 633 ), driving the step-down converter in the third step-down operation mode (see  FIG. 22B ) (S 635 ), and driving the step-down converter in the second step-down operation mode (see  FIG. 22C ) (S 634 ). 
     A ratio (V OUT /V IN ) of an output voltage to an input voltage in operation S 631  of the operating in the two-phase manner may be higher than a ratio (V OUT /V IN ) of an output voltage to an input voltage in operation S 632  of the operating in the three-phase manner. For example, when the ratio (V OUT /V IN ) of the output voltage to the input voltage is more than a certain value, operation S 631  of the operating in the two-phase manner may be performed. When the ratio (V OUT /V IN ) of the output voltage to the input voltage is less than a certain value, operation S 632  of the operating in the three-phase manner may be performed. The certain value may be, for example, a value of the ratio (V OUT /V IN ) of the output voltage to the input voltage at an intersection point between the efficiency of the two-phase manner (DPNC-2Φ Mode) and the efficiency of the three-phase manner (DPNC-3Φ Mode) of  FIG. 62  or may be a certain value adjacent to the value of the intersection. For example, when the ratio (V OUT /V IN ) of the output voltage to the input voltage is changed from less than a first certain value to more than the first certain value, operation S 631  of the operating in the two-phase manner may be performed. When the ratio (V OUT /V IN ) of the output voltage to the input voltage is changed from more than a second certain value to less than the second certain value, operation S 632  of the operating in the three-phase manner may be performed. In this case, the first certain value may be smaller than the second certain value. As described above, hysteresis may be provided to prevent frequent switching between operation S 631  of the operating in the two-phase manner and operation S 632  of the operating in the three-phase manner. 
     In many cases, since the input voltage V IN  has a fixed value, the ratio (V OUT /V IN ) of the output voltage to the input voltage is proportional to the output voltage V OUT . Therefore, the description in relation to the ratio (V OUT /V IN ) of the output voltage to the input voltage may also be applied to the output voltage V OUT . For example, the output voltage V OUT  in operation S 631  of the operating in the two-phase manner may be higher than the output voltage V OUT  in operation S 632  of the operating in the three-phase manner. In other words, one of operation S 631  of the operating in the two-phase manner and operation S 632  of the operating in the three-phase manner may be selected and performed according to the output voltage V OUT  of the step-down converter. For example, one of operation S 631  of the operating in the two-phase manner and operation S 632  of the operating in the three-phase manner may be selected and performed according to a value of the output voltage V OUT  of the step-down converter set by a processor (not shown) which controls the step-down converter. For example, when the output voltage V OUT  is more than a certain value, operation S 631  of the operating in the two-phase manner may be performed. When the output voltage V OUT  is less than a certain value, operation S 632  of the operating in the three-phase manner may be performed. In addition, when an electronic system (not shown) including a step-down converter is in a normal operation mode or a maximum performance mode, a high output voltage V OUT  may be required, and when the electronic system (not shown) is in a power saving mode or an idle mode, a low output voltage V OUT  may be required. Accordingly, when the electronic system is in the normal operation mode or the maximum performance mode, operation S 631  of the operating in the two-phase manner may be performed, and when the electronic system is in the power saving mode or the idle mode, operation S 632  of the operating in the three-phase manner may be performed. In other words, operation S 631  of the operating in the two-phase manner may be performed when the electronic system is operated in the normal operation mode or the maximum performance mode, and operation S 632  of the operating in the three-phase manner may be performed when the electronic system is operated in the power saving mode or the idle mode. In addition, a required output voltage V OUT  may be determined according to execution functions or a combination of the execution functions of the electronic system, and thus, any one of operation S 631  of the operating in the two-phase manner and operation S 632  of the operating in the three-phase manner may be performed according to the execution functions or the combination of the execution functions of the electronic system. 
     While the step-down converting method of  FIG. 63  has been described with reference to the second step-down converter shown in  FIG. 21 , the step-down converting method may be applicable to step-down converters with a plurality of various transfer paths. For example, the step-down converting method of the fifth step-down converter (see  FIG. 31 ) may be performed by operating the fifth step-down converter in the two-phase manner (S 631 ) and then operating the fifth step-down converter in the three-phase manner (S 632 ). Operation S 631  of the operating in the two-phase manner may be performed in the order of driving the fifth step-down converter in the first step-down operation mode (see  FIG. 32A ) (S 633 ) and driving the fifth step-down converter in the second step-down operation mode (see  FIG. 32C ) (S 634 ). In addition, operation S 632  of the operating in the three-phase manner may be performed in order of driving the fifth step-down converter in the first step-down operation mode (see  FIG. 32A ) (S 633 ), driving the fifth step-down converter in the third step-down operation mode (see  FIG. 32B ) (S 635 ), and driving the step-down converter in the second step-down operation mode (see  FIG. 32C ) (S 634 ). 
     For example, the step-down converting method of the sixth step-down converter (see  FIG. 33 ) may be performed in order of operating the sixth step-down converter in the two-phase manner (S 631 ) and operating the sixth step-down converter in the three-phase manner (S 632 ). Operation S 631  of the operating in the two-phase manner may be performed in order of driving the sixth step-down converter in the first step-down operation mode (see  FIG. 35A ) (S 633 ) and driving the sixth step-down converter in the second step-down operation mode (see  FIG. 35C ) (S 634 ). Alternatively, operation S 631  of the operating in the two-phase manner may be performed in order of driving the sixth step-down converter in the first step-down operation mode (see  FIG. 35A ) (S 633 ) and driving the sixth step-down converter in the third step-down operation mode (see  FIG. 35B ) (S 635 ). In addition, operation S 632  of the operating in the three-phase manner may be performed in order of driving the sixth step-down converter in the first step-down operation mode (see  FIG. 35A ) (S 633 ), driving the sixth step-down converter in the third step-down operation mode (see  FIG. 35B ) (S 635 ), and driving the step-down converter in the second step-down operation mode (see  FIG. 35C ) (S 634 ). 
     By referencing the above-described contents, those skilled in the art may understand that other step-down converters shown in the drawings may also be operated in the two-phase manner and the three-phase manner, and thus detailed descriptions thereof will be omitted for convenience of description. 
     Operation S 631  of operating the step-down converter in the two-phase manner and operation S 632  of operating the step-down converter in the three-phase manner may be included in operation S 611  of operating the step-down converter in the multi-path manner shown in  FIG. 61 . That is, operation S 611  of the operating in the multi-path manner may include operation S 631  of operating the step-down converter in the two-phase manner and operation S 632  of operating the step-down converter in the three-phase manner. In addition, operation S 611  of the operating in the multi-path manner may include operation S 631  of operating the step-down converter in the two-phase manner or operation S 632  of operating the step-down converter in the three-phase manner. Furthermore, operation S 611  of the operating in the multi-path manner may include a plurality of operations S 631  of operating the step-down converter in the two-phase manner and a plurality of operations S 632  of operating the step-down converter in the three-phase manner. 
     The exemplary embodiments described above include circuits for a DC-DC converter, but the present invention is not limited thereto and may be equally applied to an AC-AC converter, a DC-AC converter, and an AC-DC converter according to exemplary embodiments. 
     The inventive concept is not limited to the above-described exemplary embodiments. Those skilled in the art may variously modify the exemplary embodiments without departing from the gist of the invention claimed by the appended claims and the modifications are within the scope of the claims.