Abstract:
A driving device of a synchronous rectification apparatus is provided. The driving device includes a voltage detection part disposed on a power input terminal to detect a voltage value of a power inputted through the power input terminal, an adjustment part receiving the voltage value detected through the voltage detection part, the adjustment part adjusting the receive voltage value to output the adjusted voltage value, and a comparison part receiving the voltage value adjusted through the adjustment part into a positive terminal and a synchronous rectification starting value into a negative terminal, the comparison part outputting an command value of the synchronous rectification apparatus, which is obtained by comparing the received voltage value with the synchronous rectification starting value.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Pursuant to 35 U.S.C. §119(a), this application claims the benefit of earlier filing date and right of priority to Korean Patent Application No. 10-2013-0160676, filed Dec. 20, 2013, the contents of which are all hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     The present disclosure relates to a driving device of a synchronous rectification apparatus, and particularly, to a driving device of a synchronous rectification apparatus, which is capable of driving the synchronous rectification apparatus to generate uniform output current regardless of an input voltage in a charging device for charging a low voltage battery. 
     Low-voltage battery chargers are embedded in eco-friendly vehicles so as to replace generators of engine vehicles. Such a low-voltage battery charger uses energy stored in a high-voltage battery to charge a low-voltage battery having a voltage of about 12 V. 
     Low-voltage battery chargers have operation characteristics in which conditions such as an input voltage, input current, an output voltage, and output current vary when operating. 
     Therefore, synchronous rectification apparatuses are being generally used as the low-voltage battery chargers to realize high efficiency having low-voltage high-output current characteristics. 
       FIG. 1  is a view illustrating a starting device of a synchronous rectification apparatus according to a related art. 
     Referring to  FIG. 1 , a driving device of a synchronous rectification apparatus includes a protection part  11  and a comparison part  12 . 
     The driving device of the synchronous rectification apparatus is designed so that the driving device is stopped in operation when an amount of output current is small and operates when load current increases, so as to improve efficiency under a light load and prevent the synchronous rectification apparatus from being damaged due to discontinuous current. 
     The protection part  11  is configured to protect the synchronous rectification apparatus and is constituted by division resistors. 
     That is, the protection part  11  includes a first resistor R 1  having a first terminal connected to a reference voltage and a second terminal connected to a first terminal of a second resistor R 2  and the second resistor R 2  having the first terminal connected to the second terminal of the first resistor R 1  and a grounded second terminal. 
     The protection part  11  uses the division resistors to output division resistance values according to an input voltage and the reference voltage. The input voltage represents a voltage inputted into the protection part  11 . In detail, the input voltage represents a voltage outputted through a high voltage battery. 
     The comparison part  12  receives the division resistance value outputted through the protection part  11  into a negative terminal (−) and a command starting value into a positive terminal (+). The comparison part  12  outputs a command value according to a result obtained by comparing the value inputted into the negative terminal to the value inputted into the positive value. 
     Here, a preset specific command value and output current may be used as the command starting value. On the other hand, the input current may be used as the command starting value when a primary coil of the low-voltage battery charger is controlled. 
     In the above-described low-voltage battery charger that is designed to control the charging voltage and current of the low voltage battery at the primary coil, it is necessary to correct the command starting value in a case where it is required to accurately control the charging voltage and current when an actual product is embodied due to efficiency, waveform, and duty losses. 
     Particularly, when a voltage of the high voltage battery which is an input value of the low-voltage battery charger is changed, the input current with respect to the output current may have different values under the same output power to change the starting value of the synchronous rectification apparatus. 
     When the input voltage increases in a state where the input power is uniform with respect to the predetermined output voltage and output current, it seems that the input current is relatively low. Thus, primary current may operate at a low value. 
     That is, since the command starting value is set on the basis of the primary current in case of the primary coil control method, the synchronous rectification apparatus operates at a point where the output current is relatively high under the high input voltage than the low input voltage according to the command starting value when the resistors R 1  and R 2  have consistent values, thereby reducing light load efficiency. 
     Here, although it is possible to correct command starting value by changing the command starting value, the command starting value needs to be calculated whenever the above-described situations occurs. As a result, time delay occurs, and the command starting value reacts slowly after the voltage of the high battery is converted. Thus, it may be difficult to quickly correct the command starting value. 
     SUMMARY 
     Embodiments provide a driving device of a synchronous rectification apparatus in which since a starting value of the synchronous rectification apparatus is quickly and constantly converted according to output current by using an active switching device and a comparison unit even though an input voltage of a low-voltage battery charger, shortly, an output voltage of a high voltage battery is changed, the synchronous rectification apparatus may operate at output the constant output current regardless of the input voltage. 
     The feature of the embodiment is not limited to the aforesaid, but other features not described herein will be clearly understood by those skilled in the art from descriptions below. 
     In one embodiment, a driving device of a synchronous rectification apparatus includes: a voltage detection part disposed on a power input terminal to detect a voltage value of a power inputted through the power input terminal; an adjustment part receiving the voltage value detected through the voltage detection part, the adjustment part adjusting the receive voltage value to output the adjusted voltage value; and a comparison part receiving the voltage value adjusted through the adjustment part into a positive terminal and a synchronous rectification starting value into a negative terminal, the comparison part outputting an command value of the synchronous rectification apparatus, which is obtained by comparing the received voltage value with the synchronous rectification starting value. 
     The adjustment part may adjust the voltage value inputted into the positive terminal to a voltage value in inverse proportion to the voltage value detected through the voltage detection part. 
     The driving device may further include a protection part disposed between the adjustment part and the comparison part to determine an initial operation value for operating the adjustment part. 
     The protection part may be connected to a reference voltage terminal to output the reference voltage value to the positive terminal when the adjustment part abnormally operates. 
     The synchronous rectification starting value may be set on the basis of an input current value with respect to the power inputted through the power input terminal. 
     The voltage detection part may be provided with first and second resistor connected in series to each other. 
     The adjustment part may include a switching element including a gate electrode connected between the first and second resistors, a drain electrode connected a first terminal of a third resistor, and a source electrode connected a first terminal of a fourth resistor; the third resistor including the first terminal connected to the drain electrode of the switching element and a second terminal connected to a reference voltage; and the fourth resistor including the first terminal connected to the source electrode of the switching element and a second terminal connected to the ground. 
     The adjustment part may increase or decrease a voltage value inputted to the positive terminal according to the detected voltage value because drain current of the switching element increases in proportion to the detected voltage value, and the reference voltage and voltages of both terminals of the third resistor decrease in inverse proportion to the increased drain current. 
     The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a view illustrating a starting device of a synchronous rectification apparatus according to a related art. 
         FIG. 2  is a schematic block diagram of a charging device according to an embodiment. 
         FIG. 3  is a detailed circuit diagram illustrating the charging device of  FIG. 2 . 
         FIG. 4  is a detailed circuit diagram illustrating a rectification driving unit  180  of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Advantages and features of the present invention, and implementation methods thereof will be clarified through following embodiments described with reference to the accompanying drawings. The present invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. Further, the present disclosure is only defined by scopes of claims. Like reference numerals refer to like elements throughout. 
     In the following description, detailed descriptions of well-known functions or constructions will be omitted since they would obscure the invention in unnecessary detail. Also, the terms used herein are defined according to the functions of the present disclosure. Thus, the terms may vary depending on user&#39;s or operator&#39;s intentions or practices. Therefore, the terms used herein must be understood based on the descriptions made herein. 
       FIG. 2  is a schematic block diagram of a charging device according to an embodiment. 
     Referring to  FIG. 2 , the charging device includes a high voltage battery  110 , an input filter  120 , an input switching unit  130 , a transformer  140 , a rectifier  150 , an output filter  160 , a low voltage battery  170 , and a rectification driving unit  180 . 
     The high voltage battery  110  may be a fuel cell. The high voltage battery  110  may generate direct current (DC) power stored therein in a manner in which hydrogen (H 2 ) chemically reacts with oxygen (O 2 ) contained in the air to generate electric energy, and the generated electric energy is stored in a stack. 
     The high voltage battery  110  may be charged by the DC power supplied through a high voltage battery charger. 
     The input filter  120  blocks overcurrent of the DC power outputted through the high voltage battery  110 . 
     The input switching unit  130  is provided with a plurality of switching elements and converts the DC power outputted through the input filter  120  into alternating current (AC) power. 
     The transformer  140  transforms the AC power converted through the input switching unit  130 . 
     The rectifying unit  150  rectifies the AC power outputted through the transformer  140  to convert the AC power into the DC power. 
     The rectifying unit  150  may include a bridge rectifier. Here, a plurality of diodes constituting the bridge rectifier may be turned at only a voltage equal to or greater than a predetermined driving voltage to output an input power. 
     The rectifying unit  150  includes a plurality active switching elements. 
     The output filter  160  filters the DC power outputted through the rectifying unit  150  and transmits the filtered AC power to the low voltage battery  170  to charge the low voltage battery  170 . 
     The rectifying driving unit  180  controls each of the active switching elements constituting the rectifying unit  150  so as to constantly convert output current of the rectifying unit  150 . 
     Hereinafter, the detailed description with respect to the charging device will be described with reference to the accompanying drawings. 
       FIG. 3  is a detailed circuit diagram illustrating the charging device of  FIG. 2 , and  FIG. 4  is a detailed circuit diagram illustrating a rectification driving unit  180  of  FIG. 2 . 
     Referring to  FIG. 3 , the input filter  120  includes a first inductor L 1  and a first capacitor C 1 . 
     The first inductor L 1  includes a first terminal connected to a positive terminal of the high voltage battery  110  and a second terminal connected to a first terminal of the first capacitor C 1 . 
     The first capacitor C 1  includes the first terminal connected to the second terminal of the first inductor L 1  and a second terminal connected to a source electrode of a second switching element Q 2 . 
     The input switching unit  130  includes a first switching element Q 1 , the second switching element Q 2 , a third switching element Q 3 , and a fourth switching element Q 4 . 
     The first switching element Q 1  includes a drain electrode connected to the second terminal of the first inductor L 1  and to the first terminal of the first capacitor C 1  and a source electrode connected to a drain electrode of the second switching element Q 2 . 
     The second switching element Q 2  includes the drain electrode connected to the source electrode of the first switching element Q 1  and the source electrode connected to the second terminal of the first capacitor C 1  and a source electrode of the fourth switching element Q 4 . 
     The third switching element Q 3  includes a drain electrode connected to the drain electrode of the first switching element Q 1  and a source electrode connected to a drain electrode of the fourth switching element Q 4 . 
     The fourth switching element Q 4  includes the drain electrode connected to source electrode of the third switching element Q 3  and the source electrode connected to the source electrode of the second switching element Q 2 . 
     Gate electrodes of the first to fourth switching elements Q 1  to Q 4  are connected to a digital signal processor (DSP) (not shown), and each of gate electrodes receives a gate signal supplied from the DSP. 
     Each of the first to fourth switching elements Q 1  to Q 4  includes a body diode of which one end is connected to the drain electrode and the other end is connected to the source electrode and a body capacitor. 
     The transformer  140  includes a second inductor L 2 , a third inductor L 3 , and a fourth inductor L 4 . 
     The second inductor L 2  includes a first terminal connected between the source electrode of the third switching element Q 3  and the drain electrode of the fourth switching element Q 4  and a second terminal connected between the source electrode of the first switching element Q 1  and the drain electrode of the second switching element Q 2 . 
     The third inductor L 3  includes a first terminal connected to a drain electrode of a fifth switching element Q 5  and a second terminal connected to a first terminal of the fourth inductor L 4 . 
     The fourth inductor L 4  includes the first terminal connected to the second terminal of the third inductor L 3  and a second terminal connected to a drain electrode of a sixth switching element Q 6 . 
     The rectifying unit  150  includes the fifth and sixth switching elements Q 5  and Q 6 . 
     The fifth switching element Q 5  includes the drain electrode connected to the first terminal of the third inductor L 3  and a source electrode connected to a first terminal of a fifth inductor L 5 . 
     The sixth switching element Q 6  includes the drain electrode connected to the second terminal of the fourth inductor L 4  and a source electrode connected to the first terminal of the fifth inductor L 5 . 
     The output filter  160  includes the fifth inductor L 5  and a second capacitor C 2 . 
     The fifth inductor L 5  includes the first terminal connected to the source electrode of the fifth switching element Q 5  and to the source electrode of the sixth switching element Q 6  and a second terminal connected to the first terminal of the second capacitor C 2  and to a positive terminal of the low voltage battery  170 . 
     The second capacitor C 2  includes the first terminal connected to the second terminal of the fifth inductor L 5  and to the positive terminal of the low voltage battery  170  and a second terminal connected between the second terminal of the third inductor L 3  and the first terminal of the fourth inductor L 4 . 
     Since the charging device including the above-described constitutions has a general circuit of a low voltage battery charger, its detailed description will be omitted. 
     The rectification driving unit  180  includes an input part  181 , an adjustment part  182 , a protection part  183 , and a comparison part  184 . 
     The input part  181  detects an output voltage value of the high voltage battery  110  to output the detected output voltage value. The input part  181  may be a division resistor including a plurality of resistors. 
     The output voltage value detected through the input part  181  is transmitted to the adjustment part  182 . 
     The adjustment part  182  adjusts and outputs the output voltage value of the high voltage battery  110  detected through the input part  181 . 
     The adjustment part  182  includes an active switching element. The output voltage of the input part  181  is applied to a gate of the active switching element. Thus, source and drain currents of the active switching element are changed according to the voltage inputted to the gate electrode. For example, when the voltage inputted into the gate electrode of the active switching element increases, the drain current of the active switching element increases. Therefore, a voltage reduced in inverse proportion to the inputted voltage may be inputted to the protection part  183 . 
     Since the protection part  183  determines an initial operation value of the active switching element constituting the adjustment part  182  when the input voltage decreases, a command value for driving the rectifying unit  150  may be normally outputted when the adjustment part  182  is broken. 
     The comparison part  184  may receive the voltage value outputted from the protection part  182  through a positive terminal (+) and receive a rectification starting value through a negative terminal (−). The comparison part  184  compares the inputted voltage value to the inputted rectification starting value to output a command value of the synchronous rectification apparatus. 
     The detailed description with respect to the constitution of the rectification driving unit  180  will be described in detail. 
     The input part  181  includes a first resistor R 1 , a second resistor R 2 , and a first capacitor C 1 . 
     The first resistor R 1  includes a first terminal connected to the input voltage and a second terminal connected to a first terminal of the second resistor R 2 . 
     The second resistor R 2  includes the first terminal connected to the second terminal of the first resistor R 1  and a grounded second terminal. 
     The first capacitor C 1  includes a first terminal connected to the second terminal of the first resistor R 1  and to the first terminal of the second resistor R 2  and a grounded second terminal. 
     The adjustment part  182  includes an active switching element M 1  and a fourth resistor R 4 . The protection part  183  includes a third resistor R 3  and a fifth resistor R 5 . 
     The third resistor R 3  includes a first terminal connected to a reference voltage and a second terminal connected to a drain electrode of the active switching element M 1 . 
     The active switching element M 1  includes a gate electrode connected to the second terminal of the first resistor R 1 , to the first terminal of the second resistor R 2 , and to the first terminal of the first capacitor C 1  and a source electrode connected to a first terminal of the fourth resistor R 4 . 
     The fourth resistor R 4  includes the first terminal connected to the source electrode of the active switching element M 1  and a grounded second terminal. 
     The fifth resistor R 5  includes a first terminal connected to the second terminal of the third resistor R 3  and to the drain electrode of the active switching element M 1  and a grounded second terminal. 
     The comparison part  184  includes the positive terminal connected to the first terminal of the fifth resistor R 5  and the negative terminal connected to a starting value generating device of the synchronous rectification apparatus. 
     An operation of the above-described rectification driving unit  180  will be described in the following description. 
     The output voltage of the high voltage battery is applied to the active switching element M 1  through the first resistor R 2  and the first capacitor C 1 . 
     Since voltages of both terminals of the fourth resistor R 4  are determined by the voltage applied to the gate electrode of the active switching element M 1 , the active switching element M 1  may be operated in an active area to adjust the source current. Here, the source current of the active switching element M 1  is controlled to control the drain current, thereby adjusting a drain voltage. If this process is described with respect to the input voltage, the rectification driving unit  180  operates as follows. 
     When the output voltage of the high voltage battery increases, in other words, the input voltage applied to the rectification driving unit  180  increases, the drain current of the active switching element M 1  increases. Thus, a difference between the reference voltage determining the drain voltage of the active switching element M 1  and the voltages of both terminals of the third resistor R 3  may be reduced. 
     Therefore, the drain voltage of the active switching element M 1 , shortly, the voltage of both terminals of the fifth resistor R 5  may be reduced. 
     As the drain voltage of the active switching element M 1  decreases, the voltage value applied to the positive terminal of the comparison part  184  decreases. 
     That is, the active switching element M 1  may adjust the voltage value applied to the positive terminal of the comparison part  184  according to the input voltage to allow the command value of the rectification apparatus to vary according to the input voltage. 
     The current (the input current) of the input switching unit  130  may be used as the starting value of the synchronous rectification apparatus that is inputted to the negative terminal of the comparison part  184 . Therefore, since the input current decreases when the input voltage with respect to the same output amount is high, the voltage inputted to the positive terminal may be reduced to generate the command value of the synchronous rectification apparatus at low input current. 
     On the contrary, when the input voltage decreases, the voltages of both terminals of the fourth resistor R 4  are reduced to restrict the source current and drain current of the active switching element M 1  so that each of the source current and drain current is low. Thus, the drain voltage of the active switching element M 1  increases, and the increased voltage value is inputted to the positive terminal of the comparison part  184 . 
     The fifth resistor R 5  may determine an initial operation value of the active switching element M 1  when the input voltage has the lowest value and may secure the operation of the synchronous rectification apparatus even though the active switching element M 1  is broken. 
     Although the third resistor R 3  is included in the protection part  183  in the above description, the embodiment is not limited thereto. For example, the third resistor R 3  may be substantially included in the adjustment part  182 . 
     According to the embodiment, since the starting value of the synchronous rectification apparatus is quickly and constantly converted according to the output current even though the output voltage of the high voltage battery is changed, the synchronous rectification apparatus may operate at output the constant output current regardless of the input voltage. 
     According to the embodiment, since the synchronous rectification apparatus is driven using the reference value even though the driving circuit is abnormal, the damage of the circuit due to the shutdown of the synchronous rectification apparatus may be prevented. 
     It should be understood that the exemplary embodiments described therein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments. 
     Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.