Abstract:
Disclosed herein is a lighting apparatus capable of uniformly maintaining power consumed by light emitting units even in the case in which various voltages are applied, and increasing power efficiency while minimizing a heating problem by adjusting a reference voltage applied to a connection structure of the light emitting units and a distribution switch according to magnitude of the applied voltage.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to Korean Patent Application No. 10-2015-0020469, filed on Feb. 22, 2016, which is herein incorporated by reference in its entirety. 
       BACKGROUND 
       [0002]    Field 
         [0003]    The present invention relates to a lighting apparatus that may be used even at various voltages. 
         [0004]    Description of the Related Art 
         [0005]    A light emitting diode (LED) refers to a kind of semiconductor element capable of implementing light having various colors by configuring a light emitting source by forming a PN diode of a compound semiconductor. Such light emitting element has advantages that it has a long lifespan, it may be miniaturized and lightened, and it may be driven at a low voltage. In addition, since the above-mentioned LED may have impact resistance and vibration resistance, may not need a preheating time and complex driving, and may be packaged after being mounted on a substrate or a lead frame in various forms, it may be modularized in various applications to be applied to a backlight unit, a variety of lighting apparatuses, or the like. 
         [0006]    A voltage value of commercial alternating current (AC) power used for the lighting apparatus varies depending on a region in which the lighting apparatus is used. Accordingly, as different AC power sources are applied to the lighting apparatus, there are problems that brightness of the LED included in the lighting apparatus is not uniformly maintained, and power efficiency of the LED is also degraded. 
         [0007]    Accordingly, the development of technologies capable of uniformly maintaining performance of the lighting apparatus even in the case in which the AC power having various magnitudes is applied has been required. 
       SUMMARY 
       [0008]    An object of the present invention is to provide a lighting apparatus capable of uniformly maintaining power consumed by light emitting units even in the case in which various voltages are applied, and increasing power efficiency while minimizing a heating problem by adjusting a reference voltage applied to a connection structure of the light emitting units and a distribution switch according to magnitude of the applied voltage. 
         [0009]    According to an exemplary embodiment of the present invention, there is provided a lighting apparatus including: a power supply unit generating alternating current (AC) power; a light emitting unit connected in series with the power supply unit and including a first light emitting unit and a second light emitting unit that each have at least one light emitting diode element that emits light according to an input voltage input from the power supply unit and are connected in series with each other; a voltage detecting unit connected in series with the power supply unit and measuring a voltage value input from the power supply unit; a reference voltage controlling unit selectively controlling a first distribution switch unit and a second distribution switch unit which are separately connected to the first light emitting unit and the second light emitting unit, according to the voltage value measured by the voltage detecting unit; a first variable resistor unit connected between the first distribution switch unit and a ground, and including a variable resistor; a second variable resistor unit connected between the second distribution switch unit and the ground, and including a variable resistor; and a power controlling unit changing resistance values of the variable resistors included in the first variable resistor unit and the second variable resistor unit according to the voltage value measured by the voltage detecting unit to uniformly maintain power consumed by the first light emitting unit and the second light emitting unit. 
         [0010]    The power controlling unit may change the resistance values of the variable resistor of the first variable resistor unit and the variable resistor of the second variable resistor unit to the same resistance value when the voltage value measured by the voltage detecting unit is smaller than a switching control reference voltage, and change the resistance values of the variable resistor of the first variable resistor unit and the variable resistor of the second variable resistor unit to different resistance values when the voltage value measured by the voltage detecting unit is greater than the switching control reference voltage. 
         [0011]    The first variable resistor unit and the second variable resistor unit may include one or more variable resistors having different variable resistor ranges, and the power controlling unit may select the variable resistor having the same variable resistor range among the variable resistor of the first variable resistor unit and the variable resistor of the second variable resistor unit and changes the resistance values of the variable resistors to the same resistance value when the voltage value measured by the voltage detecting unit is smaller than a switching control reference voltage, and select the variable resistor having different variable resistor ranges among the variable resistor of the first variable resistor unit and the variable resistor of the second variable resistor unit and changes the resistance values of the variable resistors to different resistance values when the voltage value measured by the voltage detecting unit is greater than the switching control reference voltage. 
         [0012]    The first distribution switch unit and the second distribution switch unit may include one or more transistors which are turned on at a specific voltage among voltages input from the power supply unit. 
         [0013]    The number of the transistors may be equal to the number of light emitting diodes included in the first light emitting unit and the second light emitting unit, respectively. 
         [0014]    The first light emitting unit and the second light emitting unit may each include N light emitting groups including a plurality of light emitting diode elements, and the transistors may be connected to a rear stage of each of the N light emitting groups, and have the same number as 2*N, which is the number of the light emitting groups. 
         [0015]    The reference voltage controlling unit may change distribution switch reference voltages applied to the first distribution switch unit and the second distribution switch unit according to the voltage value measured by the voltage detecting unit. 
         [0016]    The reference voltage controlling unit may supply a first distribution switch reference voltage to the first distribution switch unit and the second distribution switch unit when the voltage value measured by the voltage detecting unit is smaller than a switching control reference voltage. 
         [0017]    The reference voltage controlling unit may supply a first distribution switch reference voltage to the first distribution switch unit, and supply a second distribution switch reference voltage having a value greater than the first distribution switch reference voltage to the second distribution switch unit, when the voltage value measured by the voltage detecting unit is greater than a switching control reference voltage. 
         [0018]    The reference voltage controlling unit may include a first distribution switch reference voltage supplying unit supplying a first distribution switch reference voltage; and a second distribution switch reference voltage supplying unit supplying a second distribution switch reference voltage having a value greater than the first distribution switch reference voltage. 
         [0019]    The first distribution switch unit and the second distribution switch unit may include one or more transistors which are turned on at a specific voltage among voltages input from the power supply unit, and the reference voltage controlling unit may change distribution switch reference voltages applied to the transistors so that the transistors are turned on only at the specific voltage, according to an increase in the voltage value measured by the voltage detecting unit. 
         [0020]    The lighting apparatus may further include a switch unit connected in series with between the power supply unit and the second light emitting unit, turned on to connect the first light emitting unit and the second light emitting unit in parallel to each other, when the voltage value measured by the voltage detecting unit is smaller than a switching control reference voltage, and turned off to connect the first light emitting unit and the second light emitting unit in series with each other, when the voltage value measured by the voltage detecting unit is greater than the switching control reference voltage. 
         [0021]    The first light emitting unit may include one or more backdraft prevention units connected in series with a rear stage of the light emitting diode element. 
         [0022]    The power supply unit may include an AC power generating unit generating an AC waveform; and a rectifying unit rectifying the AC power output from the AC power generating unit. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  is a diagram illustrating a lighting apparatus according to an exemplary embodiment of the present invention; 
           [0024]      FIGS. 2A to 2D  are diagrams illustrating a method for driving a lighting apparatus according to an exemplary embodiment of the present invention, when an input voltage is smaller than a switching control reference voltage; 
           [0025]      FIGS. 3A to 3D  are diagrams illustrating a method for driving a lighting apparatus according to an exemplary embodiment of the present invention, when an input voltage is greater than a switching control reference voltage; 
           [0026]      FIG. 4  is a detailed circuit diagram of the lighting apparatus according to an exemplary embodiment of the present invention; 
           [0027]      FIG. 5  is a diagram illustrating a method for driving a lighting apparatus of a case in which light emitting units of the lighting apparatus are connected in parallel to each other according to an exemplary embodiment of the present invention; 
           [0028]      FIGS. 6A and 6B  are diagrams illustrating currents flowing in a distribution switch unit according to the exemplary embodiment of  FIG. 5 ; 
           [0029]      FIG. 7  is a diagram illustrating a method for driving a lighting apparatus of a case in which light emitting units of the lighting apparatus are connected in series with each other according to an exemplary embodiment of the present invention; and 
           [0030]      FIG. 8  is a diagram illustrating a current flowing in a distribution switch unit according to the exemplary embodiment of  FIG. 7 . 
       
    
    
     DETAILED DESCRIPTION 
       [0031]    Hereinafter, a lighting apparatus according to exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification, different exemplary embodiments will be denoted by the same or similar reference numerals and a description thereof will be replaced by a first description. 
         [0032]      FIG. 1  is a diagram illustrating a lighting apparatus according to an exemplary embodiment of the present invention. 
         [0033]    Referring to  FIG. 1 , a lighting apparatus  100  includes a power supply unit  110 , a first light emitting unit  120 , a second light emitting unit  130 , a first distribution switch unit  140 , a second distribution switch unit  150 , a first variable resistor unit  160 , a second variable resistor unit  170 , a switch unit  180 , a voltage detecting unit  190 , a switching controlling unit  200 , a reference voltage controlling unit  210 , and a power controlling unit  220 . 
         [0034]    The power supply unit  110  may output power having a waveform which is repetitively increased or decreased over time. For example, the power supply unit  110  may include an alternating current (AC) power generating unit (not shown) generating an AC waveform, and a rectifying unit (not shown) rectifying the AC power output from the AC power generating unit. 
         [0035]    The power output from the power supply unit  110  flows through the first light emitting unit  120 , the second light emitting unit  130 , the first distribution switch unit  140 , the second distribution switch unit  150 , the first variable resistor unit  160 , the second variable resistor unit  170 , and the switch unit  180 . 
         [0036]    The power output from the power supply unit  110  may have a period of 100 Hz/120 Hz, and may have a voltage value of 100V/200V/120V/277V/110V/220V. The reason is because the values of the power used in the United States (120V/277V), Japan (100 V/200V), and Korea (110V/220V) are different from each other. 
         [0037]    The first light emitting unit  120  may be connected in series with the power supply unit  110 , and may include a plurality of light emitting groups  121 ,  122 ,  123 , and  124 . Each of the light emitting groups  121 ,  122 ,  123 , and  124  may include one or plurality of light emitting diode (LED) elements which are turned on/off according to the voltage output from the power supply unit  110 . The LED elements included in the light emitting group may be sequentially turned on as the voltage output from the power supply unit  110  is increased. 
         [0038]    The second light emitting unit  130  may be connected in series with the first light emitting unit  120 , and may include a plurality of light emitting groups  131 ,  132 ,  133 , and  134 . Each of the light emitting groups  131 ,  132 ,  133 , and  134  may include one or plurality of light emitting diode (LED) elements which are turned on/off according to the voltage output from the power supply unit  110 . The LED elements included in the light emitting group may be sequentially turned on as the voltage output from the power supply unit  110  is increased. 
         [0039]    Although the present exemplary embodiment describes the case in which there are two light emitting units  120  and  130 , and eight light emitting groups  121 ,  122 ,  123 ,  124 ,  131 ,  132 ,  133 , and  134 , the number of light emitting units and light emitting groups is not limited thereto, and may be variously implemented. 
         [0040]    The first distribution switch unit  140  may be connected to the first light emitting unit  120 , and the second distribution switch unit  150  may be connected to the second light emitting unit  130 . The first distribution switch unit  140  and the second distribution switch unit  150  may be turned on/off according to an input distribution switch reference voltage and the voltage input from the power supply unit  110 . 
         [0041]    For example, the first distribution switch unit  140  and the second distribution switch unit  150  may include a transistor. Examples of the transistor include a bipolar transistor (BT), a field effect transistor (FET), an insulated gate bipolar transistor (IGBT), and the like. However, the kind of transistor is not limited thereto. 
         [0042]    The transistor may be turned on only at a specific voltage among voltages input from the power supply unit  110 , and may be turned off at the remaining voltages. Specifically, for example, the transistor may be turned on only at a voltage of 30V input from the power supply unit  110 , and may be turned off at the remaining voltages. The specific voltage may be varied depending on a distribution switch reference voltage VREF. 
         [0043]    The number of transistors may be equal to the number of LEDs included in the first light emitting unit  120  and the second light emitting unit  130 , respectively. 
         [0044]    As another example, the transistor may be connected to a rear stage of each of N light emitting groups included in the first light emitting unit  120  and the second light emitting unit  130 , respectively, and the number of transistors may be equal to 2*N, which is the number of the light emitting groups. Since four light emitting groups are included in each of the light emitting units in the present exemplary embodiment, the number of transistors may be eight. 
         [0045]    The first variable resistor unit  160  may be connected between the first distribution switch unit  140  and a ground. The first variable resistor unit  160  may include one or more resistors  161  and  162  capable of varying a resistance value, and the respective resistors may have different variable resistance ranges. For example, the first variable resistor unit may include a first variable resistor of which resistance is varied within a first range, and a second variable resistor of which resistance is varied within a second range greater than the first range. 
         [0046]    The second variable resistor unit  170  may be connected between the second distribution switch unit  150  and the ground. The second variable resistor unit  170  may include one or more resistors  171  and  172  capable of varying a resistance value, and the respective resistors may have different variable resistance ranges. The second variable resistor unit  170  may include a third variable resistor of which resistance is varied within the first range, and a fourth variable resistor of which resistance is varied within the second range greater than the first range. For example, the third variable resistor may be equal to the first variable resistor, and the fourth variable resistor may be equal to the second variable resistor. 
         [0047]    Here, the first variable resistor and the third variable resistor are the resistors used in the case in which the input voltage is smaller than the switch control reference voltage, and the second variable resistor and the fourth variable resistor are the resistors used in the case in which the input voltage is greater than the switch control reference voltage. A detailed description thereof will be provided below with reference to  FIGS. 4 to 8 . 
         [0048]    The switch unit  180  may be connected in series between the power supply unit  110  and the second light emitting unit  130 . The switch unit  180  may be turned on/off by the switching controlling unit  200 . 
         [0049]    For example, in the case in which a voltage value measured by the voltage detecting unit  190  is smaller than the switching control reference voltage, the switch unit  180  may be turned on to connect the first light emitting unit  120  and the second light emitting unit  130  in parallel to each other. 
         [0050]    As another example, in the case in which the voltage value measured by the voltage detecting unit  190  is greater than the switching control reference voltage, the switch unit  180  may be turned off to connect the first light emitting unit  120  and the second light emitting unit  130  in series with each other. 
         [0051]    The voltage detecting unit  190  may be connected in series with the power supply unit  110 , and may measure the voltage value from the power supply unit  110 . 
         [0052]    For example, the voltage detecting unit  190  may detect the voltage value input from the power supply unit  110 , and may output a control voltage signal (e.g., a logic value) according to the detected voltage value. Specifically, for example, the voltage detecting unit  190  may include a peak detecting unit (not shown) and a control signal outputting unit (not shown). The peak detecting unit (not shown) may hold a peak value of the input power to output a peak voltage Vpeak. The control signal outputting unit (not shown) may output a control voltage signal having a first logic value (‘high’) when the peak voltage is greater than the switching control reference voltage, and may output a control voltage signal having a second logic value (‘low’) when the peak voltage is smaller than the switching control reference voltage. For example, the control signal outputting unit (not shown) may be implemented as a comparator. 
         [0053]    The switching controlling unit  200  may connect the first light emitting unit  120  and the second light emitting unit  130  in series with or in parallel to each other according to the voltage value input from the power supply unit  110 . 
         [0054]    For example, in the case in which the input voltage value (e.g., 120V) is smaller than the switching control reference voltage (e.g., 140V), the switching controlling unit  200  may turn on the switch unit  180  to connect the first light emitting unit  120  and the second light emitting unit  130  in parallel to each other. 
         [0055]    On the other hand, in the case in which the input voltage value (e.g., 277V) is greater than the switching control reference voltage (e.g., 140V), the switching controlling unit  200  may turn off the switch unit  180  to connect the first light emitting unit  120  and the second light emitting unit  130  in series with each other. 
         [0056]    As such, the connection of the light emitting units  120  and  130  is changed to the series connection or the parallel connection according to the input voltage value, thereby making it possible to drive the light emitting units  120  and  130  without adding a separate apparatus or changing an internal apparatus even in the case in which the voltages (e.g., 120V/277V) having different magnitudes are input. 
         [0057]    The reference voltage controlling unit  210  may change the distribution switch reference voltage applied to the first distribution switch unit  140  or the second distribution switch unit  150  according to the voltage value measured by the voltage detecting unit  190 . 
         [0058]    For example, the reference voltage controlling unit  210  may change the distribution switch reference voltage applied to the transistor so that the transistor is turned on only at a specific voltage, according to the voltage value measured by the voltage detecting unit  190 . In the case in which the measured voltage value is smaller than the switching control reference voltage, the reference voltage controlling unit  210  may apply the distribution switch reference voltage of 0.5V to the transistor so that the transistor is turned on at 30V. Alternatively, in the case in which the measured voltage value is smaller than the switching control reference voltage, the reference voltage controlling unit  210  may apply the distribution switch reference voltage of 1.0V to the transistor so that the transistor is turned on at 60V. As such, the reference voltage controlling unit  210  may change the distribution switch reference voltage so that the transistor is turned on only at the specific voltage. 
         [0059]    The reference voltage controlling unit  210  may include a first distribution switch reference voltage supplying unit supplying a first distribution switch reference voltage and a second distribution switch reference voltage supplying unit supplying a second distribution switch reference voltage having a value greater than the first distribution switch reference voltage. 
         [0060]    For example, in the case in which the input voltage value is smaller than the switching control reference voltage, the reference voltage controlling unit  210  supplies the first distribution switch reference voltage to the first distribution switch unit  140  and the second distribution switch unit  150 . 
         [0061]    On the other hand, in the case in which the measured voltage value is greater than the switching control reference voltage, the reference voltage controlling unit  210  supplies the first distribution switch reference voltage to the first distribution switch unit  140 , and supplies the second distribution switch reference voltage having a value greater than the first distribution switch reference value to the second distribution switch unit  150 . 
         [0062]    The power controlling unit  220  changes resistance values of the variable resistors included in the first variable resistor unit  160  and the second variable resistor unit  170  according to the input voltage value, thereby making it possible to uniformly maintain power consumed by the first light emitting unit  120  and the second light emitting unit  130 . 
         [0063]    Table 1 is to describe the case in which the power controlling unit  220  controls the variable resistor units  160  and  170  to uniformly maintain the consumption power of the light emitting units  120  and  130 . Numerical values of Table 1 are denoted for the purpose of description, and detailed numerical values may be changed according to an implementation situation. 
         [0000]    
       
         
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 180 V 
                 210 V 
                 240 V 
                 277 V 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 Variable resistor unit [Ω] 
                 24 
                 30 
                 33 
                 41 
               
               
                 Consumption Power [W] 
                 30.1 
                 29.9 
                 29.8 
                 30.1 
               
               
                   
               
             
          
         
       
     
         [0064]    Referring to Table 1, in the case in which the input voltage value is 180V, the power controlling unit  220  changes the variable resistor units  160  and  170  to 24[Ω], thereby making it possible to maintain the consumption power of the light emitting units  120  and  130  at 30.1[W]. 
         [0065]    In addition, in the case in which the input voltage value is 277V, the power controlling unit  220  changes the variable resistor units  160  and  170  to 41[Ω], thereby making it possible to maintain the consumption power of the light emitting units  120  and  130  at 30.1[W]. 
         [0066]    As such, even though the input voltage value is changed, the power controlling unit  220  varies magnitudes of resistances of the variable resistor units  160  and  170  to uniformly maintain the consumption power of the light emitting units  120  and  130 . Accordingly, the lighting apparatus  100  may uniformly maintain an overall consumption power even though the input voltage value is changed. 
         [0067]    In the case in which the voltage value measured by the voltage detecting unit  190  is smaller than the switching control reference voltage, the first light emitting unit  120  and the second light emitting unit  130  are connected in parallel to each other, and the power controlling unit  220  changes the resistance values of the variable resistor of the first variable resistor unit  160  and the variable resistor of the second variable resistor unit  170  to the same resistance value (e.g., 24Ω). 
         [0068]    On the other hand, in the case in which the voltage value measured by the voltage detecting unit  190  is greater than the switching control reference voltage, the first light emitting unit  120  and the second light emitting unit  130  are connected in series with to each other, and the power controlling unit  220  changes the resistance values of the variable resistor of the first variable resistor unit  160  and the variable resistor of the second variable resistor unit  170  to different resistance values. For example, the power controlling unit  220  may change the resistance value (e.g., 24Ω) of the variable resistor of the first variable resistor unit  160  so as to be smaller than the resistance value (e.g., 41Ω) of the variable resistor of the second variable resistor unit  170 . 
         [0069]    Hereinafter, it is assumed that the first variable resistor unit  160  and the second variable resistor unit  170  include one or more variable resistors having different variable resistance ranges. 
         [0070]    In the case in which the voltage value measured by the voltage detecting unit  190  is smaller than the switching control reference voltage, the first light emitting unit  120  and the second light emitting unit  130  are connected in parallel to each other, and the power controlling unit  220  selects the variable resistor including 24Ω in the variable resistance range from the first variable resistor unit  160  and the second variable resistor unit  170 . Next, the power controlling unit  220  may change the resistance values of the variable resistor of the first variable resistor unit  160  and the resistance value of the variable resistor of the second variable resistor unit  170  to the same resistance value (e.g., 24Ω). 
         [0071]    In the case in which the voltage value measured by the voltage detecting unit  190  is greater than the switching control reference voltage, the power controlling unit  220  may select the variable resistor having different variable resistance ranges among the variable resistor of the first variable resistor unit  160  and the variable resistor of the second variable resistor unit  170 , and may change the resistance values of the variable resistors to different resistance values. 
         [0072]    For example, the first light emitting unit  120  and the second light emitting unit  130  are connected in series with each other, and the power controlling unit  220  selects the variable resistor including 24Ω in the variable resistance range from the first variable resistor unit  160 , and selects the variable resistor including 41Ω in the variable resistance range from the second variable resistor unit  170 . Next, the power controlling unit  220  may change the resistance value of the variable resistor selected from the first variable resistor unit  160  to 24Ω, and changes the resistance value of the variable resistor selected from the second variable resistor unit  170  to 41Ω. 
         [0073]    According to an exemplary embodiment of the present invention, even in the case in which the magnitude of the applied voltage is changed, the magnitude of the resistance of the variable resistor unit is adjusted, thereby making it possible to uniformly maintain the power consumed by the light emitting units. 
         [0074]    Further, the distribution switch reference voltage applied to the distribution switch unit is changed according to the magnitude of the applied voltage, thereby making it possible to significantly reduce a heating problem by optimizing driving of the LED connected to the distribution switch unit. 
         [0075]      FIGS. 2A to 2D  are diagrams illustrating a method for driving a lighting apparatus according to an exemplary embodiment of the present invention, when an input voltage is smaller than a switching control reference voltage. 
         [0076]    Referring to  FIGS. 1 and 2A , in the case in which the input voltage value (e.g., 120V) is smaller than the switching control reference voltage (e.g., 140V), the switching controlling unit  200  may turn on the switch unit  180  to connect the first light emitting unit  120  and the second light emitting unit  130  in parallel to each other. In this case, the power applied from the power supply unit  110  flows through the first light emitting unit  120  and the second light emitting unit  130  which are connected parallel to each other. 
         [0077]    The reference voltage controlling unit  210  supplies each of the first distribution switch reference voltages (0.5V, 1.0V, 1.5V, and 2.0V) to the first distribution switch unit  140  and the second distribution switch unit  150 . In the case in which the distribution switch reference voltage is 0.5V/1.0V/1.5V/2.0V, the distribution switch is turned on only when the input voltage is 30V/60V/90V/120V. The respective distribution switches are turned off at voltages other than the respective specific voltages. The above-mentioned numerical values are merely examples, and may be variously set. 
         [0078]    Hereinafter, the lighting apparatus which is driven as the input voltage is sequentially increased will be described. 
         [0079]    Referring to  FIGS. 1 and 2A , in the case in which the input voltage value is 30V, a first distribution switch  141  connected to a rear stage of a first light emitting group  121  and a fifth distribution switch  151  connected to a rear stage of a fifth light emitting group  131  are only turned on. The remaining distribution switches are turned off. Accordingly, the power applied from the power supply unit  110  flows through the first light emitting group  121  and the first distribution switch  141 /the fifth light emitting group  131  and the fifth distribution switch  151  which are connected in parallel to each other. 
         [0080]    Referring to  FIGS. 1 and 2B , in the case in which the input voltage value is 60V, a second distribution switch  142  connected to a rear stage of a second light emitting group  122  and a sixth distribution switch  152  connected to a rear stage of a sixth light emitting group  132  are only turned on. The remaining distribution switches are turned off. Accordingly, the power applied from the power supply unit  110  flows through the first light emitting group  121 , the second light emitting group  122  and the second distribution switch  142 /the fifth light emitting group  131 , the sixth light emitting group  132  and the sixth distribution switch  152  which are connected in parallel to each other. 
         [0081]    Referring to  FIGS. 1 and 2C , in the case in which the input voltage value is 90V, a third distribution switch  143  connected to a rear stage of a third light emitting group  123  and a seventh distribution switch  153  connected to a rear stage of a seventh light emitting group  133  are only turned on. The remaining distribution switches are turned off. Accordingly, the power applied from the power supply unit  110  flows through the first light emitting group  121 , the second light emitting group  122 , the third light emitting group  123  and the third distribution switch  143 /the fifth light emitting group  131 , the sixth light emitting group  132 , the seventh light emitting group  133  and the seventh distribution switch  153  which are connected in parallel to each other. 
         [0082]    Referring to  FIGS. 1 and 2D , in the case in which the input voltage value is 120V, a fourth distribution switch  144  connected to a rear stage of a fourth light emitting group  124  and an eighth distribution switch  154  connected to a rear stage of an eighth light emitting group  134  are only turned on. The remaining distribution switches are turned off. Accordingly, the power applied from the power supply unit  110  flows through the first light emitting group  121 , the second light emitting group  122 , the third light emitting group  123 , the fourth light emitting group  124  and the fourth distribution switch  144 /the fifth light emitting group  131 , the sixth light emitting group  132 , the seventh light emitting group  133 , the eighth light emitting group  134  and the eighth distribution switch  154  which are connected in parallel to each other. 
         [0083]    If it is assumed that the first light emitting unit  120  and the second light emitting unit  130  each include N light emitting groups, in the case in which the input voltage is smaller than the switching control reference voltage, the first light emitting unit  120  forms N channels and the second light emitting unit  130  forms N channels. 
         [0084]      FIGS. 3A to 3D  are diagrams illustrating a method for driving a lighting apparatus according to an exemplary embodiment of the present invention, when an input voltage is greater than a switching control reference voltage. 
         [0085]    Referring to  FIGS. 1 and 3A , in the case in which the input voltage value (e.g., 250V) is greater than the switching control reference voltage (e.g., 140V), the switching controlling unit  200  may turn off the switch unit  180  to connect the first light emitting unit  120  and the second light emitting unit  130  in series with each other. In this case, the power applied from the power supply unit  110  flows through the first light emitting unit  120  and the second light emitting unit  130  which are connected in series with each other. 
         [0086]    The reference voltage controlling unit  210  supplies the first distribution switch reference voltages (0.5V, 1.0V, 1.5V, and 2.0V) to the first distribution switch unit  140  and each supplies the second distribution switch reference voltages (2.5V, 3.0V, 3.5V, and 4.0V) to the second distribution switch unit  130 . In the case in which the distribution switch reference voltage is 0.5V/1.0V/1.5V/2.0V/2.5V/3.0V/3.5V/4.0V, the distribution switch is turned on only when the input voltage is 30V/60V/90V/120V/150V/180V/210V/240V. The respective distribution switches are turned off at voltages other than the respective specific voltages. 
         [0087]    Hereinafter, the lighting apparatus which is driven as the input voltage is sequentially increased will be described. 
         [0088]    In the case in which the input voltage is 30V/60V/90V/120V, since the lighting apparatus is driven by the same method as the first light emitting unit  120  of  FIGS. 2A to 2D , a description thereof will be omitted. 
         [0089]    Referring to  FIGS. 1 and 3A , in the case in which the input voltage value is 150V, the fifth distribution switch  151  connected to the rear stage of the fifth light emitting group  131  is only turned on. Accordingly, the power applied from the power supply unit  110  flows through the first light emitting group  121 , the second light emitting group  122 , the third light emitting group  123 , the fourth light emitting group  124 , the fifth light emitting group  131  and the fifth distribution switch  151 . 
         [0090]    Referring to  FIGS. 1 and 3B , in the case in which the input voltage value is 180V, the sixth distribution switch  152  connected to the rear stage of the sixth light emitting group  132  is only turned on. Accordingly, the power applied from the power supply unit  110  flows through the first light emitting group  121 , the second light emitting group  122 , the third light emitting group  123 , the fourth light emitting group  124 , the fifth light emitting group  131 , the sixth light emitting group  132  and the sixth distribution switch  152 . 
         [0091]    Referring to  FIGS. 1 and 3C , in the case in which the input voltage value is 210V, the seventh distribution switch  153  connected to the rear stage of the seventh light emitting group  133  is only turned on. Accordingly, the power applied from the power supply unit  110  flows through the first light emitting group  121 , the second light emitting group  122 , the third light emitting group  123 , the fourth light emitting group  124 , the fifth light emitting group  131 , the sixth light emitting group  132 , the seventh light emitting group  133  and the seventh distribution switch  153 . 
         [0092]    Referring to  FIGS. 1 and 3D , in the case in which the input voltage value is 240V, the eighth distribution switch  154  connected to the rear stage of the eighth light emitting group  134  is only turned on. Accordingly, the power applied from the power supply unit  110  flows through the first light emitting group  121 , the second light emitting group  122 , the third light emitting group  123 , the fourth light emitting group  124 , the fifth light emitting group  131 , the sixth light emitting group  132 , the seventh light emitting group  133 , the eighth light emitting group  134  and the eighth distribution switch  154 . 
         [0093]    If it is assumed that the first light emitting unit  120  and the second light emitting unit  130  each include N light emitting groups, in the case in which the input voltage is greater than the switching control reference voltage, since the first light emitting unit  120  and the second light emitting unit  130  are connected in series with each other, the first light emitting unit  120  and the second light emitting unit  130  form 2*N channels. 
         [0094]      FIG. 4  is a detailed circuit diagram of the lighting apparatus according to an exemplary embodiment of the present invention. 
         [0095]    Referring to  FIG. 4 , a lighting apparatus  400  includes a power supply unit  410 , a first light emitting unit  420 , a second light emitting unit  430 , a first distribution switch unit  440 , a second distribution switch unit  450 , a first variable resistor unit  460 , a second variable resistor unit  470 , a switch unit  480 , a voltage detecting unit  490 , a switching controlling unit  500 , a first distribution switch reference voltage controlling unit  510 , a second distribution switch reference voltage controlling unit  520 , and a power controlling unit  530 . 
         [0096]    The power supply unit  410  may output power having a waveform which is repetitively increased or decreased over time. 
         [0097]    The first light emitting unit  420  includes a first light emitting group  421 , a second light emitting group  422 , a third light emitting group  423 , and a fourth light emitting group  424 , and the second light emitting unit  430  also includes a fifth light emitting group  431 , a sixth light emitting group  432 , a seventh light emitting group  433 , and an eighth light emitting group  434 . Although the present exemplary embodiment is described based on the case in which the light emitting units  420  and  430  each include four light emitting groups, and the respective light emitting groups include two light emitting diode elements, the number of the light emitting diode elements is not limited thereto. 
         [0098]    The first light emitting unit  420  may include a backdraft prevention unit  425  connected between the fourth light emitting group  424  and the second light emitting unit  430 . One or more backdraft prevention units  425  may be included, and may prevent the backdraft of current. 
         [0099]    The first distribution switch unit  440  may be connected between the first light emitting unit  420  and the first variable resistor unit  460 , and the second distribution switch unit  450  may be connected between the second light emitting unit  430  and the second variable resistor unit  470 . 
         [0100]    Specifically, the first distribution switch unit  440  includes a first transistor  441 , a second transistor  442 , a third transistor  443 , and a fourth transistor  444 , and the second distribution switch unit  450  includes a fifth transistor  451 , a sixth transistor  452 , a seventh transistor  453 , and an eighth transistor  454 . 
         [0101]    The first variable resistor unit  460  may be connected between the first distribution switch unit  440  and a ground. The first variable resistor unit  460  may include a first variable resistor  416  of which resistance is varied within a first range, and a second variable resistor  462  of which resistance is varied within a second range greater than the first range. 
         [0102]    The second variable resistor unit  470  may be connected between the second distribution switch unit  450  and the ground. The second variable resistor unit  470  may include a third variable resistor  471  of which resistance is varied within the first range, and a fourth variable resistor  472  of which resistance is varied within the second range greater than the first range. The first variable resistor  461  and the third variable resistor  471  are used in the case in which the input voltage is smaller than the switch control reference voltage, and the second variable resistor  462  and the fourth variable resistor  472  are used in the case in which the input voltage is greater than the switch control reference voltage. 
         [0103]    The switch unit  480  may be connected between the power supply unit  410  and the second light emitting unit  430 . The switch unit  480  may be turned on/off by the switching controlling unit  500 . 
         [0104]    The voltage detecting unit  490  may detect the voltage value input from the power supply unit  410 , and may output a control voltage signal (e.g., a logic value) according to the detected voltage value. 
         [0105]    The switching controlling unit  500  may connect the first light emitting unit  420  and the second light emitting unit  430  in series with or in parallel to each other according to the voltage value input from the power supply unit  410 . 
         [0106]    The first reference voltage controlling unit  510  may change the distribution switch reference voltage applied to the first distribution switch unit  440  according to the input voltage value. The first reference voltage controlling unit  510  may include a first distribution switch reference voltage supplying unit and a second distribution switch reference voltage supplying unit. The first distribution switch reference voltages (V L1 , V L2 , V L3 , and V L4 ) of the first reference voltage supplying unit may have values smaller than the second distribution switch reference voltages (V H1 , V H2 , V H3 , and V H4 ) of the second reference voltage supplying unit. For example, the first distribution switch reference voltages (V L1 , V L2 , V L3 , and V L4 ) of the first reference voltage supplying unit may have distribution switch reference voltage values of 0.4V, 0.7V, 1.0V, and 1.3V, and the second distribution switch reference voltages (V H1 , V H2 , V H3 , and V H4 ) of the second reference voltage supplying unit may have distribution switch reference voltage values of 1.6V, 1.9V, 2.2V, and 2.5V. 
         [0107]    The second reference voltage controlling unit  520  may change the distribution switch reference voltage applied to the second distribution switch unit  450  according to the input voltage value. The second reference voltage controlling unit  520  may include a third distribution switch reference voltage supplying unit and a fourth distribution switch reference voltage supplying unit. The third distribution switch reference voltages (V L5 , V L6 , V L7 , and V L8 ) of the third reference voltage supplying unit may have values smaller than the fourth distribution switch reference voltages (V H5 , V H6 , V H7 , and V H8 ) of the fourth reference voltage supplying unit. For example, the third distribution switch reference voltages (V L5 , V L6 , V L7 , and V L8 ) of the third reference voltage supplying unit may have distribution switch reference voltage values of 0.4V, 0.7V, 1.0V, and 1.3V, and the fourth distribution switch reference voltages (V H5 , V H6 , V H7 , and V H8 ) of the fourth reference voltage supplying unit may have distribution switch reference voltage values of 1.6V, 1.9V, 2.2V, and 2.5V. 
         [0108]    For example, in the case in which the input voltage value is smaller than the switching control reference voltage, the switching controlling unit  500  may turn on the switch unit  480  to connect the first light emitting unit  420  and the second light emitting unit  430  in parallel to each other, and the reference voltage controlling unit  510  may supply the reference voltages (V L1 , V L2 , V L3 , and V L4 ) of the first reference voltage supplying unit to the first distribution switch unit  440 , and supply the reference voltages (V L5 , V L6 , V L7 , and V L8 ) of the third reference voltage supplying unit to the second distribution switch unit  450 . 
         [0109]    On the other hand, in the case in which the input voltage value is greater than the switching control reference voltage, the switching controlling unit  500  may turn off the switch unit  480  to connect the first light emitting unit  420  and the second light emitting unit  430  in series with each other, and the reference voltage controlling unit  510  may supply the first distribution switch reference voltages (V L1 , V L2 , V L3 , and V L4 ) of the first reference voltage supplying unit to the first distribution switch unit  440 , and supply the fourth distribution switch reference voltages (V H5 , V H6 , V H7 , and V H8 ) of the fourth reference voltage supplying unit to the second distribution switch unit  450 . 
         [0110]    The power controlling unit  530  changes resistors of the first variable resistor unit  460  and the second variable resistor unit  470  according to the input voltage value, thereby making it possible to uniformly maintain output power of the first light emitting unit  420  and the second light emitting unit  430 . 
         [0111]    For example, in the case in which the input voltage value is greater than the switching control reference voltage, the power controlling unit  530  may connect the second variable resistor  462  included in the first variable resistor unit  460  to the first distribution switch unit  440 , or may connect the fourth variable resistor  472  included in the second variable resistor unit  470  to the second distribution switch unit  450 . Next, the power controlling unit  530  changes the second variable resistor  462  or the fourth variable resistor  472 , thereby making it possible to uniformly maintain the output power of the first light emitting unit  420  or the second light emitting unit  430 . 
         [0112]    As another example, in the case in which the input voltage value is smaller than the switching control reference voltage, the power controlling unit  530  may connect the first variable resistor  461  included in the first variable resistor unit  460  to the first distribution switch unit  440 , and may connect the third variable resistor  471  included in the second variable resistor unit  470  to the second distribution switch unit  450 . Next, the power controlling unit  530  changes the first variable resistor  461  or the third variable resistor  471 , thereby making it possible to uniformly maintain the output power of the first light emitting unit  420  and the second light emitting unit  430 . 
         [0113]      FIG. 5  is a diagram illustrating a method for driving a lighting apparatus of a case in which light emitting units of the lighting apparatus are connected in parallel to each other according to an exemplary embodiment of the present invention. 
         [0114]    Referring to  FIGS. 4 and 5 , in the case in which the voltage input from the power supply unit  410  is smaller than the switching control reference voltage value, the switching controlling unit  500  may turn on the switch unit  480  to connect the first light emitting unit  420  and the second light emitting unit  430  in parallel to each other. 
         [0115]    In this case, a first current I 1 A flows in the first transistor  441  of the first distribution switch unit  440 , a second current I 2 A flows in the second transistor  442 , a third current I 3 A flows in the third transistor  443 , and a fourth current I 4 A flows in the fourth transistor  444 . 
         [0116]    A fifth current I 1 B flows in the fifth transistor  451  of the second distribution switch unit  450 , a sixth current I 2 B flows in the sixth transistor  452 , a seventh current I 3 B flows in the seventh transistor  453 , and an eighth current I 4 B flows in the eighth transistor  454 . 
         [0117]    In this case, the first light emitting unit  420  forms four channels (‘four light emitting diode elements’), and the second light emitting unit  430  forms four channels (‘four light emitting diode elements’). 
         [0118]    Since the input voltage value is smaller than the switching control reference voltage, the first reference voltage controlling unit  510  turns on the switches  512 ,  514 ,  516 , and  518  so that the voltages (V L1 , V L2 , V L3 , and V L4 ) of the first reference voltage supplying unit are applied to the first distribution switch unit  440 . In this case, the voltages (V L1 , V L2 , V L3 , and V L4 ) of the first reference voltage supplying unit are applied to each of the first transistor  441 , the second transistor  442 , the third transistor  443 , and the fourth transistor  444 . 
         [0119]    The second reference voltage controlling unit  520  turns on the switches  521 ,  523 ,  525 , and  527  so that the voltages (V L5 , V L6 , V L7 , and V L8 ) of the third reference voltage supplying unit are applied to the second distribution switch unit  450 . In this case, the voltages (V L5 , V L6 , V L7 , and V L8 ) of the third reference voltage supplying unit are applied to each of the fifth transistor  451 , the sixth transistor  452 , the seventh transistor  453 , and the eighth transistor  454 . 
         [0120]    The power controlling unit  530  changes resistances of the first variable resistor unit  460  and the second variable resistor unit  470  according to the input voltage value, thereby making it possible to uniformly maintain output power of the first light emitting unit  420  and the second light emitting unit  430 . 
         [0121]      FIGS. 6A and 6B  are diagrams illustrating currents flowing in a distribution switch unit according to the exemplary embodiment of  FIG. 5 . 
         [0122]    Referring to  FIGS. 4 to 6B , an upper graph illustrates an example of one period of a waveform of an output voltage Vi of the power supply unit  410  on a time axis. A lower graph illustrates currents flowing in the transistors according to the output voltage Vi of the power supply unit  410  on the time axis. 
         [0123]    Referring to  FIG. 6A , according to a change of the time axis of the output voltage Vi, the first current I 1 A flows in the first transistor  441  of the first distribution switch unit  440 , the second current I 2 A flows in the second transistor  442 , the third current I 3 A flows in the third transistor  443 , and the fourth current I 4 A flows in the fourth transistor  444 . As such, according to a voltage increase of the output voltage Vi, the light emitting diode elements included in the first light emitting unit  420  are sequentially turned on. 
         [0124]    Referring to  FIG. 6B , according to the change of the time axis of the output voltage Vi, the fifth current I 1 B flows in the fifth transistor  451  of the second distribution switch unit  450 , the sixth current I 2 B flows in the sixth transistor  452 , the seventh current I 3 B flows in the seventh transistor  453 , and the eighth current I 4 B flows in the eighth transistor  454 . 
         [0125]    As such, the first current I 1 A, the second current I 2 A, the third current I 3 A, and the fourth I 4 A have the same values as the fifth current I 1 B, the sixth current I 2 B, the seventh current I 3 B, and the eighth current I 4 B, respectively. 
         [0126]      FIG. 7  is a diagram illustrating a method for driving a lighting apparatus of a case in which light emitting units of the lighting apparatus are connected in series with each other according to an exemplary embodiment of the present invention. 
         [0127]    Referring to  FIGS. 4 and 7 , in the case in which the voltage input from the power supply unit  410  is greater than the switching control reference voltage value, the switching controlling unit  500  may turn off the switch unit  480  to connect the first light emitting unit  420  and the second light emitting unit  430  in series with each other. 
         [0128]    In this case, a first current I 1  flows in the first transistor  441  of the first distribution switch unit  440 , a second current I 2  flows in the second transistor  442 , a third current I 3  flows in the third transistor  443 , and a fourth current I 4  flows in the fourth transistor  444 . 
         [0129]    A fifth current I 5  flows in the fifth transistor  451  of the second distribution switch unit  450 , a sixth current I 6  flows in the sixth transistor  452 , a seventh current I 7  flows in the seventh transistor  453 , and an eighth current I 8  flows in the eighth transistor  454 . 
         [0130]    In this case, the first light emitting unit  420  and the second light emitting unit  430  are connected in series with each other to form a total of eight channels (‘eight light emitting diode elements’). 
         [0131]    As a first example, in the case in which the input voltage value is smaller than the switching control reference voltage, the first reference voltage controlling unit  510  may turn on the switches  511 ,  513 ,  515 , and  517  so that the distribution switch reference voltages (V L1 , V L2 , V L3 , and V L4 ) of the first reference voltage supplying unit are supplied to the transistors  441 ,  442 ,  443 , and  444  of the first distribution switch unit  440 , and the second reference voltage controlling unit  520  may turn on the switches  521 ,  523 ,  525 , and  527  so that the distribution switch reference voltages (V L5 , V L6 , V L7 , and V L8 ) of the third reference voltage supplying unit are supplied to the transistors  451 ,  452 ,  453 , and  454  of the second distribution switch unit  450 . 
         [0132]    On the other hand, in the case in which the input voltage value is greater than the switching control reference voltage, the first reference voltage controlling unit  510  may turn on the switches  511 ,  513 ,  515 , and  517  so that the distribution switch reference voltages (V L1 , V L2 , V L3 , and V L4 ) of the first reference voltage supplying unit are supplied to the transistors  441 ,  442 ,  443 , and  444  of the first distribution switch unit  440 , and the second reference voltage controlling unit  520  may turn on the switches  522 ,  524 ,  526 , and  528  so that the distribution switch reference voltages (V 115 , V 116 , and V H8 ) of the fourth reference voltage supplying unit are supplied to the transistors  451 ,  452 ,  453 , and  454  of the second distribution switch unit  450 . 
         [0133]    As a second example, in the case in which the input voltage value is smaller than the switching control reference voltage, the first reference voltage controlling unit  510  may turn on the switches  512 ,  514 ,  516 , and  518  so that the distribution switch reference voltages (V H1 , V H2 , V H3 , and V H4 ) of the second reference voltage supplying unit are supplied to the transistors  441 ,  442 ,  443 , and  444  of the first distribution switch unit  440 , and the second reference voltage controlling unit  520  may turn on the switches  522 ,  524 ,  526 , and  528  so that the distribution switch reference voltages (V H5 , V H6 , V H7 , and V H8 ) of the fourth reference voltage supplying unit are supplied to the transistors  451 ,  452 ,  453 , and  454  of the second distribution switch unit  450 . 
         [0134]    On the other hand, in the case in which the input voltage value is greater than the switching control reference voltage, the first reference voltage controlling unit  510  may turn on the switches  511 ,  513 ,  515 , and  517  so that the distribution switch reference voltages (V L1 , V L2 , V L3 , and V L4 ) of the first reference voltage supplying unit are supplied to the transistors  441 ,  442 ,  443 , and  444  of the first distribution switch unit  440 , and the second reference voltage controlling unit  520  may turn on the switches  522 ,  524 ,  526 , and  528  so that the distribution switch reference voltages (V H5 , V H6 , V H7 , and V H8 ) of the fourth reference voltage supplying unit are supplied to the transistors  451 ,  452 ,  453 , and  454  of the second distribution switch unit  450 . 
         [0135]    The power controlling unit  530  changes resistances of the first variable resistor unit  460  and the second variable resistor unit  470  according to the input voltage value, thereby making it possible to uniformly maintain output power of the first light emitting unit  420  and the second light emitting unit  430 . 
         [0136]      FIG. 8  is a diagram illustrating a current flowing in a distribution switch unit according to the exemplary embodiment of  FIG. 7 . 
         [0137]    Referring to  FIGS. 4, 7, and 8 , an upper graph illustrates an example of one period of a waveform of an output voltage Vi of the power supply unit  410  on a time axis. A lower graph illustrates currents flowing in the transistors according to the output voltage Vi of the power supply unit  410  on the time axis. 
         [0138]    Referring to  FIG. 8 , according to a change of the time axis of the output voltage Vi, the first current I 1  flows in the first transistor  441  of the first distribution switch unit  440 , the second current I 2  flows in the second transistor  442 , the third current I 3  flows in the third transistor  443 , and the fourth current I 4  flows in the fourth transistor  444 . Next, the fifth current I 5  flows in the fifth transistor  451  of the second distribution switch unit  450 , the sixth current I 6  flows in the sixth transistor  452 , the seventh current I 7  flows in the seventh transistor  453 , and the eighth current I 8  flows in the eighth transistor  454 . 
         [0139]    As such, according to the change of the time axis of the output voltage Vi, the first current I 1 , the second current I 2 , the third current I 3 , the fourth current I 4 , the fifth current I 5 , the sixth current I 6 , the seventh current I 7 , and the eighth current I 8  sequentially flow into the transistors. Accordingly, the transistors  441 ,  442 ,  443 ,  444 ,  451 ,  452 ,  453 , and  454  are sequentially turned on. 
         [0140]    As such, in the case in which the input voltage is greater than the switching control reference voltage, and the first light emitting unit  420  and the second light emitting unit  430  are connected in series with each other, the reference voltage input to the second distribution switch  450  is changed, thereby driving all of the first distribution switch  440  and the second distribution switch  450 . 
         [0141]    Accordingly, as compared to the case in which only the specific light emitting unit is driven, a heating problem may be significantly reduced. Further, as compared to the case in which N channels are used, 2*N channels are used, thereby making it possible to increase power efficiency. 
         [0142]    According to the exemplary embodiments having the configuration described above, even in the case in which the magnitude of the applied voltage is changed, the magnitude of the resistance of the variable resistor unit is adjusted, thereby making it possible to uniformly maintain the power consumed by the light emitting units. 
         [0143]    Further, the reference voltage applied to the distribution switch unit is changed according to the magnitude of the applied voltage, thereby making it possible to significantly reduce the heating problem by optimizing the driving of the LED connected to the distribution switch unit. 
         [0144]    Further, according to an exemplary embodiment of the present invention, when the input voltage is greater than the switching control reference voltage, as compared to the case in which only one distribution switch unit is driven to use the N channels, both of the two distribution switch units are used to use the 2*N channels, thereby making it possible to increase the power efficiency. 
         [0145]    Further, according to an exemplary embodiment of the present invention, the connection of the light emitting units is changed to the series connection or the parallel connection according to the input voltage value, thereby making it possible to drive the light emitting units without adding a separate apparatus or exchanging an internal apparatus even in the case in which the voltages having different magnitudes are input. 
         [0146]    The configurations and the methods of the above-mentioned exemplary embodiments are not restrictively applied to the lighting apparatus as described above. That is, all or some of the respective exemplary embodiments may be selectively combined with each other so that they may be various modified.