JP2014075943A - Converter and bidirectional converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a converter and a bidirectional converter reducing a switching loss, capable of coping with a wide range input/output voltage/current.SOLUTION: The converter and the bidirectional converter include: a first circuit which is connected to a primary winding of a transformer; a second circuit which is connected to a secondary winding of the transformer; and inductance means which is connected to the primary winding side or the second winding side of the transformer. Out of a first circuit switching element of an upper arm of a first or second leg becoming a set in an on-state and the first circuit switching element of a lower arm of a second or first leg in a first circuit, the first circuit switching element in which first capacitors or second capacitors are connected in parallel is turned off earlier.

Description

  The present invention relates to a converter and a bidirectional converter.

  Generally, a transformer for insulating an input side and an output side is used in a DC-DC converter. Further, the input DC voltage can be stepped up or stepped down according to the turn ratio between the input side and the output side of the transformer. As a conventional DC-DC converter, for example, the DC-DC converter disclosed in Patent Document 1 uses a step-up transformer 16. This DC-DC converter turns off the second and third switching elements 15b and 15c when the first and fourth switching elements 15a and 15d are on, as shown in FIG. By inverting these operations in the next period and generating each period alternately, a high-frequency AC voltage rectangular wave is generated. The high-frequency AC voltage rectangular wave generated by this operation is boosted by the transformer 16 and output via the full-wave rectifier circuit 17. When a desired output voltage is obtained, the converter control unit 20 controls the first and fourth switching elements 15a and 15d or the second and third switching elements 15b and 15c of the inverter circuit 14 to be turned off.

  Similarly, in the DC-DC converter shown in FIG. 7 of Patent Document 2, the input DC voltage is converted to AC by the duty ratio control of the inverter 8, and the obtained AC is transformed by the transformer 9 and passed through the rectifier circuit 10. Output a DC voltage. In this DC-DC converter, the duty ratio of the inverter 8 is changed according to the change of the input voltage. In this Patent Document 2, when the input voltage largely fluctuates, the loss of the transformer 9 increases when the duty ratio decreases. For this reason, in the DC-DC converter shown in FIG. 8 of Patent Document 2, the step-down circuit 7 is inserted before the inverter 8, and the step-down circuit 7 is operated when the input voltage is large. In the DC-DC converter shown in FIG. 1 of Patent Document 2, a connection switching circuit 18 is provided, and when the input voltage is large, the output voltage is lowered via the connection switching circuit 18.

JP 2008-278723 A JP-A-11-187654

  However, these DC-DC converters have a problem that switching loss occurs because the switch of the inverter circuit is turned off in a state where the current is still flowing when the desired output voltage is reached. Also, in order to realize a wide range of input / output voltage currents, if the switching elements in the inverter are handled by duty ratio control, the loss of the transformer increases, and if a step-down circuit or switching circuit is provided to reduce the loss of the transformer, the circuit There is a problem that the control becomes complicated.

  Therefore, an object of the present invention is to provide a converter and a bidirectional converter that can cope with a wide range of input / output voltage currents and reduce switching loss.

  The converter according to the present invention includes a transformer having a primary winding and a secondary winding, a switching element having a switching element in which an antiparallel diode and a parallel capacitor are respectively connected in parallel, as upper and lower arms, and a first terminal. A first leg and a second leg respectively connected in parallel with the second terminal; one switching element of the upper and lower arms of the first leg or the second leg; or the upper arm of the first leg and the second leg Alternatively, the first capacitor connected in parallel to one switching element of the lower arm and the other switching element of the upper and lower arms of the first leg or the second leg, or the upper arm or the lower arm of the first leg and the second leg A second capacitor connected in parallel to the other switching element of the first circuit, the first circuit connected to the primary winding side, and a bridge connection At least two of the unidirectional elements include a bridge connection circuit in which switching elements including switch elements each having a parallel capacitor connected in parallel are connected in parallel, and at least two of the switching elements. A third capacitor and a fourth capacitor each connected in parallel; a second circuit connected to the secondary winding side; a connection point side of the upper and lower arms of the first leg; Between the connection point side of the upper and lower arms via the primary winding or in the bridge connection circuit, the unidirectional elements are connected in series with the same polarity and the unidirectional elements. Switching the upper arm of the first or second leg with inductance means connected via the secondary winding to the other connection point side connected in series with the same polarity A switch and a switching element of the lower arm of the second or first leg are turned on and off alternately to convert direct current input from the first and second terminal sides into alternating current and output from the first circuit. When the on / off control of the switching elements in the set is alternately performed, the switching of the upper arm switching element in the first or second leg and the lower arm in the second leg in the on state are switched. And a control circuit that first turns off the switching element to which the first capacitor or the second capacitor is connected in parallel among the elements.

  The converter and bidirectional converter of the present invention can cope with a wide range of input / output voltage currents and can reduce switching loss.

1 is a configuration diagram of a converter according to a first embodiment of the present invention. Driving the switching elements S1 to S4 of the first circuit 1 and the switching elements S5 and S6 of the second circuit 2 when the switching elements S5 and S6 of the second circuit 2 are turned on and off in the converter according to the first embodiment of the present invention. It is a wave form diagram which shows an example of a signal. An example of voltage and current of switching elements S1 to S4 of first circuit 1 and exciting current of transformer 11 when switching elements S5 and S6 of second circuit 2 are turned on and off in the converter according to the first embodiment of the present invention. FIG. In the converter according to the first embodiment of the present invention, when the switching elements S5 and S6 of the second circuit 2 are turned on and off, the voltages and currents of the switching elements S5 and S6 of the second circuit 2 and the unidirectional elements D7 and D8 It is a wave form diagram which shows an example of a voltage and an electric current. FIG. 4 is an enlarged waveform diagram of a part of the waveform diagram of FIG. 3. FIG. 4 is a circuit diagram formed at each timing when switching elements S5 and S6 of the second circuit 2 are turned on and off in the converter according to the first embodiment of the present invention. In the converter according to the first embodiment of the present invention, the voltage output to the side between the third terminal T3 and the fourth terminal T4 is obtained from the output voltage obtained by turning on and off the switching elements S5 and S6 of the second circuit 2. 6 is an example of a waveform diagram showing drive signals for switching elements S1 to S4 of the first circuit 1 and switching elements S5 and S6 of the second circuit 2 in the operation of lowering the voltage. In the converter according to the first embodiment of the present invention, the voltage output to the side between the third terminal T3 and the fourth terminal T4 is obtained from the output voltage obtained by turning on and off the switching elements S5 and S6 of the second circuit 2. 6 is a waveform diagram showing an example of voltages and currents of the switching elements S1 to S4 of the first circuit 1 and an exciting current of the transformer 11 in the operation of lowering the voltage. In the converter according to the first embodiment of the present invention, the voltage output to the side between the third terminal T3 and the fourth terminal T4 is obtained from the output voltage obtained by turning on and off the switching elements S5 and S6 of the second circuit 2. 6 is a waveform diagram showing an example of voltages and currents of the unidirectional elements D5 to D8 of the second circuit 2 in the operation of lowering the second circuit 2. FIG. In the converter according to the first embodiment of the present invention, the voltage output to the side between the third terminal T3 and the fourth terminal T4 is obtained from the output voltage obtained by turning on and off the switching elements S5 and S6 of the second circuit 2. It is a circuit diagram formed at each timing for the operation of lowering. It is a block diagram of the bidirectional | two-way converter which concerns on the 2nd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the following embodiment is one form of this invention, and this invention is not limited to these embodiment. In the following embodiments and drawings of the present specification, components having the same reference numerals indicate the same components.

(First embodiment)
A converter according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a configuration diagram of a converter according to a first embodiment of the present invention. The converter shown in FIG. 1 includes a transformer 11, a first circuit 1 connected to the primary winding 11a side of the transformer 11, and a second circuit 2 connected to the secondary winding 11b side of the transformer 11. Inductance means L and control circuit 3 are provided. This converter converts the direct current input from the first terminal T1 and the second terminal T2 side into alternating current and outputs it from the first circuit 1, and converts the alternating current into direct current in the second circuit 2 via the transformer 11. Electric power is supplied to the third terminal T3 and the fourth terminal T4 side on the output side.

  Power from an external power supply is input to the first terminal T1 and the second terminal. A capacitor 16 is connected between the first terminal T1 and the second terminal T2, and becomes a DC voltage. Further, the first circuit 1 is connected between the first terminal T1 and the second terminal, and the first circuit 1 is a full bridge in which upper and lower arms of the first leg 12 and the second leg 13 are configured by switching elements S1 to S4. It is a circuit.

  The first leg 12 and the second leg 13 are connected in parallel between the first terminal and the second terminal, respectively. The first leg 12 has switching elements S1 and S2 as upper and lower arms, and the second leg 13 has switching elements S3 and S4 as upper and lower arms. In FIG. 1, switching elements S1 to S4 in which antiparallel diodes D1 to D4 and parallel capacitors C1 to C4 are connected in parallel to the switching elements Q1 to Q4 are used. That is, the antiparallel diodes D1 to D4 are internal diodes of the switching elements S1 to S4, and the parallel capacitors C1 to C4 are parasitic capacitances of the switching elements S1 to S4.

  In the present invention, as the antiparallel diodes D1 to D4 connected in parallel to the switching elements Q1 to Q4, the built-in diodes of the switching elements S1 to S4 may be used as shown in FIG. A diode externally attached to -S4 may be used, or a combination thereof may be used. Similarly, the parallel capacitors C1 to C4 connected in parallel to the switching elements Q1 to Q4 may use the parasitic capacitances of the switching elements S1 to S4 as shown in FIG. 1, and are separate from the switching elements S1 to S4. An external capacitor may be used, or a combination thereof.

  The first capacitor Ca and the second capacitor Cb are respectively connected in parallel to the switching elements S1 and S4 or the switching elements S2 and S3 of the first circuit 1 to be turned off first. In FIG. 1, the first capacitor Ca and the second capacitor Cb are respectively connected in parallel to the switching elements S3 and S4 of the upper and lower arms of the second leg 13 that are turned off first.

  The second circuit 2 includes a bridge connection circuit including unidirectional elements D7 and D8 and two switching elements S5 and S6, a third capacitor Cc and a fourth capacitor connected in parallel to the two switching elements S5 and S6, respectively. And a capacitor Cd, which is connected to the secondary winding 11b side of the transformer 11. In FIG. 1, switching elements S5 and S6 including switch elements Q5 and Q6 in which unidirectional elements D5 and D6 and parallel capacitors C5 and C6 are respectively connected in parallel are used. Further, a series circuit of unidirectional elements D5 and D6 connected in series with the same polarity and a series circuit of unidirectional elements D7 and D8 connected in series with the same polarity are respectively connected to the third terminal T3. Are connected in parallel between the fourth terminals T4.

  In FIG. 1, switching elements S5 and S6 in which antiparallel diodes D5 and D6 and parallel capacitors C5 and C6 are connected in parallel to switching elements Q5 and Q6, respectively, are used. That is, the unidirectional elements D5 and D6 are internal diodes of the switching elements S5 and S6, and the parallel capacitors C5 and C6 are parasitic capacitances of the switching elements S5 and S6. In the present invention, the unidirectional elements D5 and D6 may use diodes built in the switching elements S5 and S6 as shown in FIG. 1, and are diodes externally attached separately from the switching elements S5 and S6. Or a combination thereof. Similarly, the parallel capacitors C5 and C6 may use the parasitic capacitances of the switching elements S5 and S6 as shown in FIG. 1, or may use external capacitors separately from the switching elements S5 and S6. Alternatively, a combination thereof may be used.

  In the bridge connection circuit of the second circuit 2, the connection point side where the unidirectional elements D5, D6 are connected in series with the same polarity and the other connection where the unidirectional elements D7, D8 are connected in series with the same polarity The secondary winding 11b of the transformer 11 is connected to the point side. A capacitor 17 is connected between the third terminal T3 and the fourth terminal T4, and a DC voltage is output between the third terminal T3 and the fourth terminal T4.

  The inductance means L is connected to the connection point side of the upper and lower arms of the first leg 12 and the connection point side of the upper and lower arms of the second leg 13 via the primary winding 11 a of the transformer 11. In the inductance means L, the unidirectional elements D5 and D6 are connected in series with the same polarity in the bridge connection circuit of the second circuit 2, and the unidirectional elements D7 and D8 are connected in series with the same polarity. The other connection point side may be connected via the secondary winding 11b of the transformer 11. In FIG. 1, one end of the inductance means L is connected to the connection point side of the upper and lower arms of the first leg 12, and the other end is connected to the primary winding 11a side of the transformer 11. The other end may be connected to the primary winding 11 a side of the transformer 11 on the connection point side of the upper and lower arms of the two legs 13. The same applies to the case where the inductance means L is connected via the secondary winding 11b.

  The control circuit 3 gives drive signals to the switching elements S1 to S4 of the first circuit 1 and the switching elements S5 and S6 of the second circuit 2 to control on / off of each switching element. In the converter of FIG. 1, the switching element S1 or S3 of the upper arm of the first leg 12 or the second leg 13 and the switching element S4 or S2 of the lower arm of the second leg 13 or the first leg 12 are each set. Alternately turn on and off. Of the switching elements S1 and S4 of the first circuit 1 to be paired, the switching element S4 or S1 is turned off first, and then the switching element S1 or S4 is turned off later. Similarly, among the switching elements S2 and S3 of the first circuit 1 which is the other set, the switching element S3 or S2 is turned off first, and then the switching element S2 or S3 is turned off later.

  The output voltage detection means 18 of the second circuit 2 shown in FIG. 1 detects the output voltage of the second circuit 2 output between the third terminal T3 and the fourth terminal T4. This output voltage detection value is input to the control circuit 3. The control circuit 3 controls the output voltage of the second circuit 2 by turning on and off the switching elements S1 to S4 of the first circuit 1 and the switching elements S5 and S6 of the second circuit 2 based on the output voltage detection value. For example, the control circuit 3 uses the pulse widths and frequencies of the switching elements S1 to S4 of the first circuit 1 and the switching elements S5 and S6 of the second circuit 2 so that the output voltage detection value approaches the target voltage value according to the load condition. Pulse control that modulates etc. is performed. The output voltage detection means 18 of the second circuit 2 connects a resistor on the output side, for example, and detects the voltage applied to this resistor.

  The control circuit 3 controls the amount of energy accumulated in the inductance means L from the first terminal T1 and second terminal T2 side by pulse control of the drive signal applied to the switching element S5 or S6 of the second circuit 2. In this case, the switching elements S5 and S6 of the second circuit 2 are turned on during a period in which the switching elements S1 and S4 of the first circuit 1 and the switching elements S2 and S3 of the first circuit 1 that are paired are in the on state. The secondary winding 11b side of the transformer 11 is short-circuited. Thereby, the energy input from the first terminal T1 and the second terminal T2 side is accumulated in the inductance means L. Next, the switching elements S5 and S6 of the second circuit 2 are turned off during a period in which the switching elements S1 and S4 of the first circuit 1 and the switching elements S2 and S3 of the pair of the first circuit 1 continue to be on. . Thereby, the energy stored in the inductance means L is supplied to the third terminal T3 and the fourth terminal T4 side.

  Further, the control circuit 3 operates to lower the voltage output between the third terminal T3 and the fourth terminal T4 than the output voltage obtained by the operation of turning on and off the switching elements S5 and S6 of the second circuit 2 described above. In this case, the switching element of the first circuit is pulse-controlled, and the switching elements S5 and S6 of the second circuit are operated so as not to conduct in the forward direction. Specifically, the control circuit 3 inputs from the first terminal T1 and the second terminal T2 side during a period in which the switching elements S1 and S4 of the first circuit or the switching elements S2 and S3 of the first circuit to be paired are in the ON state. The switching element of the first circuit is pulse-controlled so that the energy to be supplied is supplied to the third terminal T3 and the fourth terminal T4 side via the inductance means L, and the switching elements S5 and S6 of the second circuit are forwardly driven. Operate so as not to conduct. In this operation, since the control circuit 3 does not conduct the switching elements S5 and S6 of the second circuit 2 in the forward direction, the bridge connection circuit of the second circuit 2 is a full bridge in which the unidirectional elements D5 to D8 are conducted. Functions as a rectifier circuit.

  The drive signal will be described in the following operation with the drive signal for turning on the switching element of the first circuit 1 and the switching element of the second circuit 2 being an on signal and the drive signal for turning off the off signal. As the drive signal, voltage, current, or the like is used. Further, the on signal, the off signal, and the like are not particularly limited, and may be a signal that is given throughout the on or off period or a signal that is given as a trigger for a short time.

  Next, an example of the operation of the converter according to the first embodiment of the present invention will be described. First, the case where the operation | movement which turns on / off switching element S5, S6 of the 2nd circuit 2 of a converter is demonstrated using FIGS. 2-6. FIG. 2 is a waveform diagram showing an example of drive signals for the switching elements S1 to S4 of the first circuit 1 and the switching elements S5 and S6 of the second circuit 2. FIG. 3 is a waveform diagram showing an example of the voltage and current of the switching elements S1 to S4 of the first circuit 1 and the exciting current of the transformer 11. FIG. 4 is a waveform diagram showing an example of the voltage and current of the switching elements S5 and S6 of the second circuit 2 and the voltage and current of the unidirectional elements D7 and D8. FIG. 5 is an enlarged view of a part of time Tx in the waveform diagram of FIG. FIG. 6 is a circuit diagram formed at each timing. In the current waveforms shown in FIGS. 3 to 5, the current flowing in the forward direction through the switching elements S1 to S4 of the first circuit 1 and the switching elements S5 and S6 of the second circuit 2 is positive, and the switching of the first circuit 1 is performed. The current flowing in the reverse direction through the elements S1 to S4 and the switching elements S5 and S6 of the second circuit 2 and the current flowing in the forward direction through the unidirectional elements D7 and D8 are negative.

  Assume that an ON signal is given to the switching elements S1 and S4 of the first circuit 1 to be paired at time t1. It is assumed that the ON signal of the switching element S6 of the second circuit 2 has already been given before time t1. Then, the switch elements Q1, Q4 and the switch element Q6 conduct in the forward direction. In this state, as shown in FIG. 6A, the input power supplied from the first terminal T1 and the second terminal T2 side causes the current to flow from the first terminal T1 side to the switching element Q1, the inductance means L, It flows to the primary winding 11a, the switch element Q4, and the second terminal T2. On the secondary winding 11b side of the transformer 11, a current flows through the secondary winding 11b, the switch element Q6, and the unidirectional element D8, and the secondary winding 11b side is short-circuited. For this reason, energy is stored in the inductance means L by the input power supplied from the first terminal T1 and the second terminal T2. In addition, power is supplied from the capacitor 17 to the third terminal T3 and the fourth terminal T4 side.

  At time t2, for example, the second timing is determined by the control circuit 3 so that the voltage detection value between the third terminal T3 and the fourth terminal T4 detected by the output voltage detection means 18 of the second circuit approaches the target value. Assuming that an off signal is given to the switching element S6 of the circuit 2, supply of energy stored in the inductance means L to the output side of the second circuit 2 is started. As shown in FIG. 6B, a current flows through the same path on the primary winding 11a side of the transformer 11 from the time t1, but the switch element Q6 is turned off on the secondary winding 11b side. As shown in FIG. 4, at this time t2, the switching element Q6 is turned off while a large current flows through the switching element S6 of the second circuit 2, so that switching loss becomes a problem. As a means for reducing the switching loss, it is conceivable to reduce the voltage across the switching element S6 when the switching element S6 is off.

  In the present invention, a parallel capacitor C6 and a fourth capacitor Cd are connected in parallel to the switch element Q6 to increase the capacitance of the capacitor. Similarly, a parallel capacitor C5 and a third capacitor Cc are connected in parallel to the switch element Q5 to increase the capacitance of the capacitor. When the switch element Q6 is turned off at time t2, as shown in FIG. 6B, on the secondary winding 11b side, the parallel capacitor C6 and the fourth capacitor Cd connected in parallel to the turned off switch element Q6 are charged. In the direction, current flows from the secondary winding 11b through the parallel capacitor C6, the fourth capacitor Cd, and the unidirectional element D8. On the other hand, a discharge current flows from the parallel capacitor C5 and the fourth capacitor Cc through the third terminal T3, the fourth terminal T4 side, the unidirectional element D8, and the secondary winding 11b. By increasing the capacitor capacity, it is possible to moderate the rise in the voltage across the switching element S6 of the second circuit 2 due to the charge / discharge operation of the parallel capacitor C6 and the fourth capacitor Cd, and the parallel capacitor C5 and the third capacitor Cc. . For this reason, the switching loss at the time of OFF of switching element S6 of the 2nd circuit 2 can be reduced.

  When charging / discharging of the parallel capacitor C6 and the fourth capacitor Cd and the parallel capacitor C5 and the third capacitor Cc of the second circuit 2 is completed at time t3, as shown in FIG. 6C, the unidirectional element D5 becomes conductive. To do. The current on the secondary winding 11b side flows from the secondary winding 11b through the unidirectional element D5, the third terminal T3, the fourth terminal T4 side, and the unidirectional element D8. The energy accumulated in the inductance means L between the time t1 and the time t2 is supplied to the output side of the second circuit 2. In addition, in the supply to the second circuit 2 output side by the energy accumulated in the inductance means L described above, in addition to the supply to the load connected to the tip of the third terminal T3 and the fourth terminal T4, the time from the time t1 to the time The capacitor 17 discharged during t2 is charged. Further, the current on the primary winding 11a side continues to flow through the same current path from time t1 to time t4 when the switch element Q4 is turned off.

  At time t4, the control circuit 3 gives an off signal to the switching element S4 of the first circuit 1 to be turned off first, among the switching elements S1 and S4 of the first circuit 1 to be paired. For this reason, as shown in FIG. 3, since the switching element Q4 is turned off in a state where the current value is relatively large, a switching loss occurs when the switching element S4 of the first circuit 1 is turned off. As a means for reducing this switching loss, it is conceivable to reduce the voltage across the switching element S4 of the first circuit 1 when the switching element S4 of the first circuit 1 is off.

  In the present invention, in addition to the parallel capacitor C4, the second capacitor Cb is also connected in parallel to the switch element Q4 to increase the capacitance of the capacitor. Similarly, in addition to the parallel capacitor C3, the first capacitor Ca is connected in parallel to the switch element Q3 to increase the capacitance of the capacitor. Therefore, when the switch element Q4 is turned off at time t4, as shown in FIG. 6D, on the primary winding 11a side, the parallel capacitor C4 and the second capacitor Cb connected in parallel to the turned off switch element Q4. Current flows in the direction of charging the inductance means L, the primary winding 11a, the parallel capacitor C4 and the second capacitor Cb, the second terminal T2, and the first terminal T1 through the switch element Q1. On the other hand, a discharge current flows from the parallel capacitor C3 and the first capacitor Ca through the switch element Q1, the inductance means L, and the primary winding 11a. By increasing the capacitor capacity, it is possible to moderately increase the voltage across the switching element S4 due to the charge / discharge operation of the parallel capacitor C4 and the second capacitor Cb, the parallel capacitor C3 and the first capacitor Ca. Therefore, the switching loss when the switching element S4 of the first circuit 1 is turned off can be reduced.

  When the discharge of the parallel capacitor C3 and the first capacitor Ca and the charge of the parallel capacitor C4 and the second capacitor Cb are finished at time t5, as shown in FIG. 6E, the antiparallel diode connected in parallel to the switch element Q3. D3 conducts. On the primary winding 11a side, due to the energy accumulated in the inductance means L and the exciting current of the transformer 11, the inductance means in the same direction as the current flowing in the primary winding 11a and the inductance means L immediately before time t5. L, a current flows from the primary winding 11a through the antiparallel diode D3 and the switching element Q1. The current on the secondary winding 11b side continues from time t3 and flows through the secondary winding 11b, the unidirectional element D5, the third terminal T3 side, the fourth terminal T4 side, and the unidirectional element D8. Yes. This period of flowing through the current path on the secondary winding 11b side continues from when the unidirectional element D5 is conducted until the current flowing through the unidirectional element D5 becomes substantially zero.

  At time t6, among the switching elements S1 and S4 of the first circuit 1 to be paired, the drive signal for the switching element S1 to be turned off later is turned off. Since the switching element Q1 is turned off, a current flows from the primary winding 11a through the anti-parallel diode D3, the parallel capacitor C1, and the inductance means L due to the exciting current of the transformer that flows immediately before time t6, and charges the parallel capacitor C1. To do. On the other hand, a discharge current flows from the parallel capacitor C2 through the inductance means L, the primary winding 11a, the antiparallel diode D3, the first terminal T1 side, and the second terminal T2 side. At this time, the switch element Q1 is turned off while the current is still flowing, but this current can be used as the exciting current of the transformer 11 having a very small value. Therefore, since the switching element S1 can be turned off later, the current value when the switching element S1 is turned off can be reduced. Therefore, the switching loss can be reduced as compared with the switching element Q4 that is turned off first.

  When the charging and discharging of the parallel capacitors C1 and C2 are completed at time t7, the antiparallel diode D2 is turned on as shown in FIG. On the primary winding 11a side, the anti-parallel diode D3 and the first terminal T1 from the primary winding 11a in the same direction as the current flowing in the primary winding 11a immediately before time t7 due to the exciting current of the transformer 11. Current flows through the side, the second terminal T2 side, the anti-parallel diode D2, and the inductance means L. The current on the secondary winding 11b side continues from time t3 and flows through the secondary winding 11b, the unidirectional element D5, the third terminal T3 side, the fourth terminal T4 side, and the unidirectional element D8. Yes. This period of flowing through the current path on the secondary winding 11b side continues from when the unidirectional element D5 is conducted until the current flowing through the unidirectional element D5 becomes substantially zero.

  At time t8, the drive signals of the switching elements S2 and S3 of the first circuit 1 that are in the other set are turned on. As shown in FIG. 6 (h), on the primary winding 11a side, the switch element Q2 and the switch element Q3 conduct in the forward direction, and the first terminal T1 side, the switch element Q3, the primary winding 11a, inductance means A current flows through L, the switch element Q2, and the second terminal T2. On the secondary winding 11b side, the ON signal is given to the drive signal of the switching element S5 of the second circuit 2 before the time t8, and the switching element Q5 is in a state in which the switching element Q5 can conduct in the forward direction at the time t8. Yes. For this reason, when the switch element Q5 conducts in the forward direction, a current flows from the secondary winding 11b through the antiparallel diode D7 and the switch element Q5, and the secondary winding 11b side is in a short circuit state. Therefore, energy is stored in the inductance means L by the electric power input from between the first terminal T1 and the second terminal T2.

  In the present invention, immediately before time t8, the anti-parallel diodes D2 and D3 connected in parallel to the switching elements Q2 and Q3, respectively, are conducting, so that as shown in FIG. 5, the switching elements of the first circuit 1 S2 and S3 can realize zero voltage switching when turned on.

  In addition, since the unidirectional element D5 in parallel with the switch element Q5 is conducted immediately before time t8, the switch element Q5 can be turned on with zero voltage. In order to realize the zero voltage switching of the switching element Q5, the ON signal that is the drive signal of the switching element S5 of the second circuit 2 is the time from the time t3 that is a period in which the unidirectional element D5 is conducting. You should give it during the period of 8.

  The operations of the switching elements S2 and S3 of the first circuit 1 that are the other set after time t8 are operated in the same manner as from the time t1 to the time t8 of the switching elements S1 and S4 that are the above set. That is, during the period when the switch element Q2 and the switch element Q3 are conducting, for example, control is performed so that the voltage detection value between the third terminal T3 and the fourth terminal T4 on the output side of the second circuit 2 becomes a predetermined value. An OFF signal is given to the switching element S5 of the second circuit 2 at a timing determined by the circuit 3. Thereby, the energy stored in the inductance means L is supplied to the third terminal T3 and the fourth terminal T4 side. Thereafter, the switch element Q3 to which the first capacitor Ca is connected in parallel is turned off first among the switching elements S2 and S3 to be paired, and the switch element Q2 is turned off later.

  In the present invention, as shown in FIG. 1, the switching elements S1 and S2 of the first circuit 1 to be turned off later are connected in series. In order to realize the zero voltage switching for the switching elements S1 and S2 to be turned off thereafter, for example, when the switching element S1 is turned off, the voltage across the switching element S2 of the other lower arm in the same first leg is set to zero. An ON signal is given to the switch element Q2 after being lowered to. Here, a period from when an OFF signal is applied to the switch element Q1 to when an ON signal is applied to the switch element Q2, that is, a period during which both the switching elements S1 and S2 are turned off is defined as Td.

  The discharge operation for reducing the voltage across the switching element S2 to zero, that is, discharging until the capacitor C2 voltage becomes zero, is due to the above-described excitation current flowing. Therefore, in order to realize zero voltage switching of the switching element S2 to be turned off later, first, it is necessary to make the excitation current large enough to reduce the voltage across the switching element S2 to zero. Furthermore, it is necessary to provide a period Td during which both the switching elements S1 and S2 can be turned off so that the voltage across the switching element S2 can be reduced to zero by the excitation current. The same applies to the case where zero voltage switching is realized for the switching element S1 of the first circuit 1 to be turned off later. It is necessary to provide an excitation current having a magnitude that can reduce the voltage across the switching element S1 to zero and a period Td during which both the switching elements S1 and S2 are turned off.

  If the period Td during which both the switching elements S1 and S2 of the first circuit 1 are turned off is set to a large value, the voltage rises again after the voltage across the first switching element S1 or S2 drops to zero. C1 or C2 may be charged after being discharged to zero. For this reason, it is preferable that the period Td during which both the switching elements S1 and S2 are turned off is set to a period during which the voltage across the switching element S1 or S2 drops to zero. Further, the parallel capacitors C1 and C2 having the capacitances of the capacitors connected in parallel to the switch elements Q1 and Q2 to be turned off later have a small capacitance value such as a parasitic capacitance built in the switching elements S1 and S2, and may vary depending on parts. . For this reason, a separate capacitor may be connected in parallel to the parasitic capacitances built in the switching elements S1 and S2, and these combined capacitances may be used as the parallel capacitors C1 and C2.

  Next, referring to the converter circuit diagram of FIG. 1 and FIGS. 7 to 10, the voltage output to the side between the third terminal T3 and the fourth terminal T4 is turned on / off for the switching elements S5 and S6 of the second circuit 2 described above. An operation for causing the second circuit 2 to function as a full-bridge rectifier circuit when the output voltage is lower than the output voltage obtained by the operation is described. FIG. 7 is a waveform diagram showing an example of drive signals for the switching elements S1 to S4 of the first circuit 1 and the switching elements S5 and S6 of the second circuit 2 in this operation. FIG. 8 is a waveform diagram showing an example of the voltages and currents of the switching elements S1 to S4 of the first circuit 1 and the exciting current of the transformer 11 in this operation. FIG. 9 is a waveform diagram showing an example of voltages and currents of the unidirectional elements D5 to D8 of the second circuit 2 in this operation. FIG. 10 is a circuit diagram formed at each timing for this operation of the converter according to the first embodiment of the present invention. 8 and 9, the current flowing in the forward direction through the switching elements S1 to S4 of the first circuit 1 is positive, and the current flowing in the reverse direction through the switching elements S1 to S4 of the first circuit 1 The current flowing in the forward direction through the unidirectional elements D5 to D8 is negative.

  In the case of this operation, the converter circuit of FIG. 1 functions as a full-bridge rectifier circuit in which the bridge connection circuit of the second circuit 2 conducts the unidirectional elements D5 to D8. For this reason, since the converter of Embodiment 1 should just have the unidirectional element D5-D8 at least in the 2nd circuit 2, as shown in FIG. 7, in the drive signal of switching element S5 and S6 of the 2nd circuit 2, No ON signal is given.

  Time t21 is a time point at which an ON signal is given to the ON signal to the switching elements S1 and S4 of the first circuit 1 to be paired. At this time, no ON signal is given to the switching elements S5 and S6 of the second circuit 2. As shown in FIG. 10 (a), on the primary winding 11a side of the transformer 11, the current flows from the first terminal T1 side to the switching element Q1, the inductance means L, the primary winding 11a, the switching element Q4, It flows to the two terminal T2 side. On the secondary winding 11b side of the transformer 11, a current flows from the secondary winding 11b through the unidirectional element D8 from the unidirectional element D5, the third terminal T3, and the fourth terminal T4 side. Input power supplied from the first terminal T1 and the second terminal T2 side is supplied to the third terminal T3 and the fourth terminal T4 side via the inductance means L.

  At time t22, for example, the control circuit 3 makes a pair so that the voltage detection value between the third terminal T3 and the fourth terminal T4 detected by the output voltage detection means 18 of the second circuit approaches the target value. Of the switching elements S1 and S4 of one circuit 1, an off signal is given to the switching element S4 that is turned off first. For this reason, as shown in FIG. 8, since the switching element Q4 is turned off in a state where the current value is relatively large, a switching loss occurs when the switching element S4 is turned off. In the present invention, as described in the operation of turning on and off the switching elements S5 and S6 of the second circuit 2, the second capacitor Cb is connected in parallel to the switching element Q4 in addition to the parallel capacitor C4. The capacity is increased. Similarly, in addition to the parallel capacitor C3, the first capacitor Ca is connected in parallel to the switch element Q3 to increase the capacitance of the capacitor.

  Therefore, when the switch element Q4 is turned off at time t22, as shown in FIG. 10B, on the primary winding 11a side, the parallel capacitor C4 and the second capacitor Cb connected in parallel to the turned off switch element Q4. Current flows in the direction of charging the inductor L, the primary winding 11a, the parallel capacitor C4 and the second capacitor Cb, the second terminal T2, and the first terminal T1 through the switch element Q1. On the other hand, a discharge current flows from the parallel capacitor C3 and the first capacitor Ca through the switch element Q1, the inductance means L, and the primary winding 11a. The capacitance of the capacitor connected in parallel to the switching elements S4 and S3 of the first circuit 1 to be turned off first is increased, and the voltage at both ends of the switching element S4 is gradually increased, whereby the switching element S4 of the first circuit 1 is moderated. The switching loss at the time of OFF is reduced.

  When the discharge of the parallel capacitor C3 and the first capacitor Ca and the charge of the parallel capacitor C4 and the second capacitor Cb are finished at time t23, as shown in FIG. 10C, the antiparallel diode connected in parallel to the switch element Q3. D3 conducts. On the primary winding 11a side, due to the energy accumulated in the inductance means L and the exciting current of the transformer 11, the inductance means L in the same direction as the current flowing in the primary winding 11a and the inductance means L immediately before time t5. A current flows from the primary winding 11a through the antiparallel diode D3 and the switch element Q1. The current on the secondary winding 11b side continues from time t21 and flows through the secondary winding 11b, the unidirectional element D5, the third terminal T3 side, the fourth terminal T4 side, and the unidirectional element D8. Yes.

  At time t24, the driving signal for the switching element S1 to be turned off later among the switching elements S1 and S4 of the first circuit 1 to be paired is turned off. Since the switching element Q1 is turned off, the transformer exciting current that flows immediately before time t23 causes the primary winding 11a to move from the primary winding 11a to the antiparallel diode D3, the parallel capacitor C1, and the inductance means L as shown in FIG. A current flows through and charges the parallel capacitor C1. On the other hand, a discharge current flows from the parallel capacitor C2 through the inductance means L, the primary winding 11a, the antiparallel diode D3, the first terminal T1, and the second terminal T2. At this time, the switch element Q1 is turned off while the current is still flowing, but the current can be made smaller than that of the switch element Q4 turned off first. Therefore, the switching loss of the switch element Q1 to be turned off later can be reduced as compared to when the switch element Q4 to be turned off first is turned off.

  When the charging and discharging of the parallel capacitors C1 and C2 are completed at time t25, the antiparallel diode D2 becomes conductive as shown in FIG. On the primary winding 11a side, the anti-parallel diode D3 and the first terminal T1 from the primary winding 11a in the same direction as the current flowing in the primary winding 11a immediately before time t25 due to the exciting current of the transformer 11 A current flows through the second terminal T2 side, the antiparallel diode D2, and the inductance means L. The current on the secondary winding 11b side continues from time t21 and flows through the secondary winding 11b, the unidirectional element D5, the third terminal T3 side, the fourth terminal T4 side, and the unidirectional element D8. Yes.

  At time t26, an ON signal is given to the switching elements S2 and S3 of the first circuit 1 which is the other set. As shown in FIG. 10 (f), on the primary winding 11a side, the switch element Q2 and the switch element Q3 conduct in the forward direction, and the first terminal T1 side, the switch element Q3, the primary winding 11a, inductance means A current flows through L, the switch element Q2, and the second terminal T2. Since the current flowing through the primary winding 11a is in the opposite direction, the unidirectional element D6 and the unidirectional element D7 conduct in the forward direction on the secondary winding 11b side, and the secondary winding 11b A current flows from the unidirectional element D7, the third terminal T3, the fourth terminal T4 side through the unidirectional element D6. As in the case of FIG. 10A, the power input from between the first terminal T1 and the second terminal T2 is supplied to the third terminal T3 and the fourth terminal T4 side via the inductance means L.

  As in the case of the operation of turning on and off the switching elements S5 and S6 of the second circuit 2 described above, the switching element immediately before the time t26 is also performed in the operation of causing the bridge connection circuit of the second circuit 2 to function as a full-bridge rectifier circuit. Since antiparallel diodes D2 and D3 connected in parallel to Q2 and Q3, respectively, are conducting, as shown in FIG. 8, switching elements S2 and S3 of first circuit 1 realize zero voltage switching when turned on. be able to.

  The operation of the switching elements S2 and S3 of the first circuit 1 which is the other set after the time t26 is operated in the same manner as from the time t21 to the time t26 of the switching elements S1 and S4 which are the above set. That is, for example, the control circuit 3 includes a first capacitor Ca connected in parallel among the pair of switching elements S2 and S3 so that the output voltage between the third terminal T3 and the fourth terminal T4 has a desired value. The switch element Q3 is turned off first, and the switch element Q2 is turned off later.

  In the converter according to the first embodiment, the control circuit 3 performs the operation of causing the bridge connection circuit of the second circuit 2 described above to function as a full-bridge rectifier circuit. If the detected value of the voltage output from the side between the third terminal T3 and the fourth terminal T4 does not approach the target value even if the pulse width or frequency of the signal is modulated, the switching elements S5 and S6 of the second circuit 2 are turned on. Switch to on / off operation. On the contrary, the control circuit 3 modulates the pulse width and frequency of the switching elements S5 and S6 of the second circuit 2 when performing the operation of turning on and off the switching elements S5 and S6 of the second circuit 2 described above. If the detected value of the voltage output from the side between the third terminal T3 and the fourth terminal T4 does not approach the target value, the operation is switched to the operation for causing the bridge connection circuit of the second circuit 2 to function as a full bridge rectifier circuit. By switching between the two operations, a wide range of input / output voltage currents can be handled regardless of circuit constants such as the turns ratio of the transformer 11 and load conditions.

  Note that, as in the case of the operation of turning on and off the switching elements S5 and S6 of the second circuit 2 described above, the operation of causing the bridge connection circuit of the second circuit 2 to function as a full-bridge rectifier circuit is also included in the first circuit 1 set. Among the switching elements to be turned off, the capacity of the capacitor connected in parallel to the switch element to be turned off first is set larger than the capacity of the capacitor connected in parallel to the switch element to be turned off later. Further, in order to realize zero voltage switching for the switching elements S1 and S2 of the first circuit 1 to be turned off later, first, it is necessary to make the excitation current large enough to reduce the voltage across the switching element S2 or S1 to zero. is there. Furthermore, it is necessary to provide a period Td during which both the switching elements S1 and S2 can be turned off so that the voltage across the switching element S2 or S1 can be reduced to zero by the excitation current.

  The period Td during which both the switching elements S1 and S2 of the first circuit 1 are turned off is preferably about a period during which the voltage across the switching element S1 or S2 drops to zero. In addition, the parallel capacitors C1 and C2 of the capacitors connected in parallel to the switch elements Q1 and Q2 to be turned off later have a small capacitance value such as in the case of the parasitic capacitance built in the first switching elements S1 and S2, and may vary depending on the parts. is there. For this reason, a separate capacitor may be connected in parallel to the parasitic capacitances built in the switching elements S1 and S2, and these combined capacitances may be used as the parallel capacitors C1 and C2.

  In FIG. 2 and FIG. 7, an ON signal that is a drive signal for the switching elements S2 and S3 of the first circuit 1 is simultaneously applied at time t8 and time t26, and the switch element Q2 and the switch element Q3 are sequentially switched. An example of the operation starting to conduct in the direction is shown. However, the present invention is not limited to an example of the operation of the above-described embodiment, and the time points when the ON signals of the switching elements S2 and S3 are given may not be the same. Further, the time point when the ON signals of the switching elements S2 and S3 are given may be a period in which the antiparallel diodes D2 and D3 are conducting. In this case, the time when the ON signals of the switching elements S2 and S3 are given does not coincide with the time when the switching elements Q2 and Q3 start to conduct in the forward direction, for example, the current that conducts the antiparallel diodes D2 and D3 is zero. Then, current starts to flow in the forward direction through the switch element Q2 and the switch element Q3. In addition, when the voltage drop of the switching elements Q2 and Q3 when the current flows in the reverse direction is smaller than the forward voltage that is the voltage drop of the antiparallel diodes D2 and D3 when the forward current flows, the switching element It is possible to reduce the conduction loss of the switching elements S2 and S3 by providing the ON signals of S2 and S3 and causing the switching elements Q2 and Q3 to conduct in the reverse direction. The same applies to the switching elements S1 and S4 of the first circuit 1 which are the other set.

  In the first embodiment described above, the switching elements S4 and S3 of the upper and lower arms of the second leg 13 among the switching elements S1 and S4, S2 and S3 of the first circuit 1 to be paired are turned off first. The switching elements S1 and S2 of the upper and lower arms of the first leg 12 may be turned off first. In this case, the first capacitor Ca and the second capacitor Cb are respectively connected to the switching elements S1 and S2 that are turned off first. The switching elements of the first circuit 1 to be turned off first are the switching elements S1 and S3 of the upper arms of the first leg 12 and the second leg 13, or the lower arms of the first leg 12 and the second leg 13. The switching elements S2 and S4 may be used. In this case, the first capacitor Ca and the second capacitor Cb are connected in parallel to the switching elements S1 and S3 or the switching elements S2 and S4 that are turned off first.

  In the first embodiment, the series circuit of the switching elements S5 and S6 connected between the third terminal T3 and the fourth terminal T4 in the bridge connection circuit of the second circuit 2 shown in FIG. The position of the unidirectional elements D7 and D8 with the series circuit may be switched. Also in this case, the third capacitor Cc and the fourth capacitor Cd are respectively connected in parallel to the switching elements S5 and S6 of the second circuit 2 to be turned on / off. Further, in the second circuit 2, a circuit configuration of a mixed bridge connection that connects a series circuit of the unidirectional element D7 or D8 and the switching element S5 or S6 of the second circuit 2 between the third terminal T3 and the fourth terminal T4, respectively. It may be. Also in this case, the third capacitor Cc and the fourth capacitor Cd are connected in parallel to the switching elements S5 and S6 of the second circuit 2 to be turned on / off, respectively.

  Furthermore, in the description of the first embodiment, the diode is shown as the unidirectional element D7 and the unidirectional element D8 of the second circuit 2, but the element that conducts current in one direction without being limited to this example. If it is. Further, as the unidirectional element, an internal diode of the switching element may be used similarly to the switching elements S5 and S6. In the description of the operation for causing the bridge connection circuit of the second circuit 2 described above to function as a full-bridge rectifier circuit, for example, an on signal is supplied to the switching elements S5 and S6 in FIG. And the switch elements Q5 and Q6 may be conducted in the reverse direction, that is, in the forward direction of the unidirectional elements D5 and D6. When the voltage drop of the switching elements Q5 and Q6 when the current flows in the reverse direction is smaller than the forward voltage that is the voltage drop of the reverse unidirectional elements D5 and D6 when the forward current flows, The conduction loss of the conductive elements D5 and D6 can be reduced. Similarly, when the switching elements S7 and S8 including the unidirectional elements D7 and D8 or the switching elements S7 and S8 connected in parallel with the unidirectional elements D7 and D8 are used, the switching elements Q7 and Q8 are reversed. It is possible to reduce the conduction loss of the unidirectional elements D7 and D8. In the above-described converter, the voltage output between the third terminal T3 and the fourth terminal T4 side is used only for the operation to lower the output voltage obtained by the operation of turning on / off the switching elements S5 and S6 of the second circuit 2. In this case, the second circuit 2 may have at least a switching element that can flow a current in the same direction as the forward direction of the unidirectional elements D5 to D8 or the unidirectional elements D5 to D8 that operate as a full-bridge rectifier circuit.

  The converter of the present invention uses the inductance means connected to the primary winding or secondary winding side of the transformer, turns on and off the switching element of the second circuit, and rectifies the bridge connection circuit of the second circuit as a full bridge. By realizing the operation of functioning as a circuit, a wide range of input / output voltage currents can be handled. In addition, the switching loss that occurs when the switching element is turned off while the current is flowing can be reduced, and occurs when one of the switching elements of the first circuit to be paired is turned off later. Switching loss can be reduced. Furthermore, switching loss can be reduced by realizing zero voltage switching.

(Second Embodiment)
FIG. 11 shows an electric circuit diagram of the bidirectional converter according to the second embodiment of the present invention. In the bidirectional converter according to the second embodiment of the present invention, components having the same reference numerals as those of the converter according to the first embodiment indicate the same components. Here, the configuration and operation different from those of the converter according to the first embodiment will be mainly described.

  In the bidirectional converter according to the second embodiment, the second circuit is configured in the same manner as the first circuit in order to operate in both directions. For this reason, in FIG. 11, the second circuit 22 has a circuit structure in which the switching elements are the upper and lower arms of two legs. In addition, since the drive signal is also given to the switching elements S7 and S8 of the second circuit 22, the control circuit 23 is used here. The first leg 12, the second leg 13 and the third leg 14 of the second circuit 22 of the first circuit 1 are the same as the configuration shown in FIG. 1 described in the first embodiment. Similarly to FIG. 1, in FIG. 11, the inductance means L is connected to the primary winding 11a side, but it may be connected to the secondary winding 11b side.

  Of the switching elements S1 and S4 and S2 and S3 of the first circuit 1 paired with the first circuit 1, the upper and lower arms of one leg that is turned off first, here the switching elements S3 of the upper and lower arms of the first leg 12, S4 is connected in series. First and second capacitors Ca and Cb are connected in parallel to the switching elements S3 and S4 of the first circuit 1 to be turned off first.

  As shown in FIG. 11, the third leg 24 and the fourth leg 25 of the second circuit 22 are respectively connected in parallel between the third terminal T3 and the fourth terminal T4. The third leg 24 and the fourth leg 25 are full-bridge connection circuits in which the upper and lower arms are configured by the switching elements S5 to S8. The switching elements S5 to S8 are connected in parallel with switching elements Q5 to Q8, unidirectional elements D5 to D8, and parallel capacitors C5 to C8, respectively. As in the first embodiment, the unidirectional elements D5 to D8 may use the built-in diodes of the switching elements S5 to S8 of the second circuit 22 as shown in FIG. In addition to the switching elements S5 to S8, an externally attached diode may be used, or a combination thereof may be used. Similarly, the parallel capacitors C5 to C8 may use the parasitic capacitances of the switching elements S5 to S8 of the second circuit 22 as shown in FIG. An attached capacitor may be used, or a combination thereof.

  When supplying power from the second circuit 22 to the first circuit 1, the upper and lower arms of one leg of the switching elements S5 and S8 and S6 and S7 that are paired in the second circuit 22 that are turned off first, Then, the switching elements S5 and S6 of the upper and lower arms of the third leg 24 are connected in series. The third and fourth capacitors Cc and Cd are connected in parallel to the switching elements S5 and S6 that are turned off first.

  When power is supplied from the first circuit 1 to the second circuit 22 side, the same operation as described in the first embodiment is performed. When power is supplied from the second circuit 22 to the first circuit 1 side, the control circuit 23 includes the third and fourth capacitors among the switching elements S5 and S8 and S6 and S7 that form a pair in the second circuit 22. The switching elements S5 and S6 to which Cc and Cd are respectively connected in parallel are turned off first.

  When power is supplied from the first circuit 1 to the second circuit 22 side, when the switching element of the second circuit 2 on the output side is turned on / off, the control circuit 23, as in the first embodiment, The switching elements S5 and S6 to which the third and fourth capacitors Cc and Cd of the two circuit 22 are connected in parallel are turned on and off. In addition, when power is supplied from the second circuit 22 to the first circuit 1 side, when the switching element of the first circuit 1 on the output side is turned on / off, the control circuit 23 is the first circuit 1 in the first circuit 1. 1. The switching elements S3 and S4 of the first circuit 1 to which the first and second capacitors Ca and Cb are respectively connected in parallel are turned on and off. Note that, in the case of an operation in which the voltage on the output side is lower than the output voltage obtained by the operation of turning on or off the switching element of the second circuit or the first circuit, as described in the first embodiment, The switching elements S5 to S8 of the two circuit 22 or the switching elements S1 to S4 of the first circuit 1 function as a rectifier circuit.

  In addition, when the control circuit 23 performs an operation for causing the second circuit 22 or the first circuit 1 on the output side to function as a rectifier circuit, the pulse width or frequency of the switching element of the first circuit 1 or the second circuit 22 If the detected value of the voltage output from the third terminal T3 and the fourth terminal T4 or the side between the first terminal T1 and the second terminal T2 does not approach the target value even when the signal is modulated, the second circuit on the output side 22 or the switching element of the first circuit 1 is switched to the on / off operation.

  Specifically, when power is supplied from the first circuit 1 to the second circuit 22 side, the control circuit 3 is a period in which the switching elements S1 and S4 or S2 and S4 of the first circuit to be paired are in an ON state. The switching element S4 or S3 of the first circuit 1 is pulsed so that the energy input from the first terminal T1 and second terminal T2 side is supplied to the third terminal T3 and fourth terminal T4 side via the inductance means L. Control. At this time, the switching elements S5 and S6 of the second circuit 2 are not conducted in the forward direction. From this state, the energy input from the first terminal T1 and the second terminal T2 side is accumulated in the inductance means L during the period when the switching elements S1 and S4 or S2 and S4 of the first circuit to be paired are in the ON state. In addition, the switching element S6 or S5 of the second circuit 2 to which the third capacitor Cc or the fourth capacitor Cd is connected in parallel is conducted in the forward direction. Then, before switching off the switching element S4 or S3 of the first circuit 1 to be turned off first, the operation is switched to the operation of turning off the switching element S6 or S5 of the second circuit 2 that is conducted in the forward direction.

  Conversely, when the control circuit 23 performs an operation of turning on or off the switching element of the second circuit 22 or the first circuit 1 on the output side, the pulse width of the switching element of the second circuit 22 or the first circuit 1 is If the detected value of the voltage output from the third terminal T3 and the fourth terminal T4 or between the first terminal T1 and the second terminal T2 does not approach the target value even if the frequency is modulated, the second on the output side The operation is switched to allow the circuit 22 or the first circuit 1 to function as a rectifier circuit.

  Specifically, when supplying power from the first circuit 1 to the second circuit 22 side, the control circuit 3 sets the switching elements S1 and S4 or S2 and S4 of the first circuit 1 to be in the ON state. The switching element S6 of the second circuit 2 to which the third capacitor Cc or the fourth capacitor Cd is connected in parallel so that the energy input from the first terminal T1 and the second terminal T2 side is stored in the inductance means L in a certain period. Alternatively, S5 is conducted in the forward direction. At this time, the switching element S6 of the second circuit 22 that turns off the switching element S6 or S5 of the second circuit 22 that is conducted in the forward direction before turning off the switching element S4 or S3 of the first circuit 1 that is turned off first. Alternatively, assume that the pulse control of S5 is performed. Next, from this operation, the energy input from the first terminal T1 and the second terminal T2 side during the period in which the switching elements S1 and S4 or S2 and S4 of the first circuit 1 in the pair are in the ON state is used as the inductance means. The operation is switched to the operation in which the switching element of the second circuit 2 is not conducted in the forward direction so as to be supplied to the third terminal T3 and the fourth terminal T4 via L.

  As described above, the operation of the first circuit and the second circuit is switched so that the detected value of the voltage output from the third and fourth terminals or between the first and second terminals is brought close to the target value. Performs pulse control of the switching element. By switching between the two operations, a wide range of input / output voltage currents can be handled without being limited by circuit constants such as the turns ratio of the transformer and load conditions.

  As described above, in the present invention, among the switch elements that form the first or second circuit set on the input side, the capacitance of the capacitor connected in parallel to the switch element that is turned off first is parallel to the switch element that is turned off later. It should be larger than the capacitance of the capacitor connected to. Similarly, a capacitor is connected in parallel to the switching element of the second circuit or the first circuit on the output side to be turned on / off. This reduces switching loss that occurs when the switching element of the first circuit and the switching element of the second circuit are turned on and off.

  In order to realize zero voltage switching for the switching elements S1 and S2 of the first circuit 1 or the switching elements S7 and S8 of the second circuit 22 to be turned off later, for example, the switching element S1 or second of the first circuit 1 When the switching element S7 of the circuit 22 is turned off, the voltage across the switching element S2 of the first circuit 1 or the switching element S8 of the second circuit 22 of the other arm in the same leg is lowered to zero before the switching element Q2 Alternatively, it is necessary to give an ON signal to Q8. The discharge operation for discharging until the voltage across the switching element S2 of the first circuit 1 or the switching element S8 of the second circuit 22, that is, the voltage of the capacitor C2 or C8 becomes zero, is due to the above-described excitation current flowing.

  Therefore, in order to realize zero voltage switching of the switching element S2 of the first circuit 1 or the switching element S8 of the second circuit 22 to be turned off later, first, the exciting current is changed to the switching element S2 or the second circuit 22 of the first circuit 1. The voltage across the switching element S8 needs to be large enough to reduce it to zero. Furthermore, the switching element S1, S2 of the first circuit 1 or the second circuit 22 of which the voltage across the switching element S2 of the first circuit 1 or the switching element S8 of the second circuit 22 can be reduced to zero by the excitation current. It is necessary to provide a period Td during which both the switching elements S7 and S8 are turned off. The same applies to the case where zero voltage switching is realized for the switching element S1 of the first circuit 1 and the switching element S7 of the second circuit 2 which are turned off later. The exciting current of such a magnitude that the voltage across the switching element S1 of the first circuit 1 or the switching element S8 of the second circuit 22 can be reduced to zero and the switching elements S1, S2 or the second circuit 22 of the first circuit 1 It is necessary to provide a period Td during which both switching elements S7 and S8 are turned off.

  If the period Td during which both the switching elements S1 and S2 of the first circuit 1 are turned off is set to a large value, the voltage rises again after the voltage across the switching element S1 or S2 drops to zero, that is, the capacitor C1. Or it may be charged after C2 is discharged to zero. For this reason, it is preferable that the period Td during which both the switching elements S1 and S2 are turned off is set to a period during which the voltage across the switching element S1 or S2 drops to zero. The same applies to the switching elements S7 and S8 of the second circuit 22. Further, the parallel capacitors C1 and C2 having the capacitance of the capacitors connected in parallel to the switch elements Q1 and Q2 to be turned off later have a small capacitance value such as in the case of the parasitic capacitance built in the switching elements S1 and S2 of the first circuit 1, There are variations. For this reason, a separate capacitor may be connected in parallel to the parasitic capacitances built in the switching elements S1 and S2 of the first circuit 1, and these combined capacitors may be used as the parallel capacitors C1 and C2. The same applies to the parallel capacitors C7 and C8 of the second circuit 22.

  In the present invention, in the above description, an inductance component provided in parallel with the primary winding or the secondary winding of the transformer 11 in order to set the excitation current to an appropriate magnitude is also included in the excitation inductance of the above-described transformer. In the above description, the current that flows due to the combined inductance of the exciting inductance of the transformer 11 and the inductance component provided in parallel with the transformer 11 is also included in the above-described exciting current. The transformer excitation inductance can be adjusted in the transformer structure, for example, by the gap width of the core, the number of windings, the core material, and the like.

  In the first and second embodiments described above, the control circuits 3 and 23 allow the voltage values detected by the output voltage detection means 18 of the second circuit and the output voltage detection means 19 of the first circuit to approach the target values. However, the detection value to be used may be a combination of these in addition to the output current value and the output power. Similarly, the detected value of voltage, current, or power on the input side may approach the target value. In general, a calculated value obtained by multiplying the detected voltage and current is used as the detected power value. The above output voltage, current or power detection value or input voltage, current or power detection value is calculated by multiplying or dividing a certain coefficient by these values or adding or subtracting a certain value. The value obtained in this way is also included.

  The present invention uses an inductance means connected to the primary winding or secondary winding side of the transformer to turn on or off the second circuit on the output side or the switching element of the first circuit, and the second circuit on the output side. Alternatively, it is possible to cope with a wide range of input / output voltage currents by realizing the operation of causing the first circuit to function as a rectifier circuit. In addition, the switching loss that occurs when the switching element is turned off while the current is flowing can be reduced, and occurs when one of the switching elements of the first circuit to be paired is turned off later. Switching loss can be reduced. Furthermore, switching loss can be reduced by realizing zero voltage switching.

  In the electric circuit of the present invention, the connection point refers to a portion that is electrically connected and at the same potential, and does not refer to a point that is physically connected. Further, the configuration, structure, number, arrangement, shape, material, and the like of each part in the converter and the bidirectional converter according to the present invention are not limited to the above-described specific examples, and those appropriately adopted by those skilled in the art are also included in the present invention. As long as the gist of the present invention is included, it is included in the scope of the present invention.

  More specifically, for example, the semiconductor elements illustrated by symbols are not limited to these specific electric elements, but include an electric element including a single electric element or a plurality of electric elements having the same function or action. All of these variations are included within the scope of the present invention. Similarly, the number and arrangement of circuit elements including diodes, capacitors, and switching elements that are appropriately designed by those skilled in the art are included in the scope of the present invention.

T1 ... 1st terminal, T2 ... 2nd terminal, T3 ... 3rd terminal, T4 ... 4th terminal, 1 ... 1st circuit, 2, 22 ... 2nd circuit, 3, 23 ... control circuit, 11 ... transformer, 12 ... first leg, 13 ... second leg, 24 ... third leg, 25 ... fourth leg, 16, 17 ... Capacitors, 18 ... Output voltage detection means of the second circuit, 19 ... Output voltage detection means of the first circuit, S1 to S4 ... Switching elements of the first circuit, Q1 to Q4 ... Switch elements, D1 to D4 ... antiparallel diodes, C1 to C4 ... parallel capacitors, D5 to D8 ... unidirectional elements (antiparallel diodes), S5 to S8 ... switching elements of the second circuit , Q5 to Q8... Switch element, C5 to C8... Parallel capacitor, Ca to Cd. The fourth capacitor, L ··· inductance means

Claims (8)

A transformer having a primary winding and a secondary winding;
A first leg and a second leg connected in parallel between a first terminal and a second terminal, respectively, with a switching element having a switching element in which an anti-parallel diode and a parallel capacitor are connected in parallel; A first capacitor connected in parallel to one switching element of the upper and lower arms of the first leg or the second leg or one switching element of the upper arm or the lower arm of the first leg and the second leg; A second capacitor connected in parallel to the other switching element of the upper arm of the leg or the second leg or the other switching element of the upper arm or the lower arm of the first leg and the second leg, and A first circuit connected to the winding side;
At least two of the unidirectional elements to be bridge-connected include a bridge connection circuit in which switching elements including switching elements each having a parallel capacitor connected in parallel are connected in parallel, and at least two of the unidirectional elements A second circuit connected to the secondary winding side, having a third capacitor and a fourth capacitor respectively connected in parallel to the switching element;
The unidirectional elements are the same between the connection point side of the upper and lower arms of the first leg and the connection point side of the upper and lower arms of the second leg through the primary winding or in the bridge connection circuit. Inductance means connected via the secondary winding between a connection point side connected in series with polarity and the other connection point side where the unidirectional elements are connected in series with the same polarity;
Direct current input from the first and second terminal sides by alternately switching on and off the switching element of the upper arm of the first or second leg and the switching element of the lower arm of the second or first leg. Is converted into alternating current and output from the first circuit, and the switching elements in the set are alternately turned on and off, and the switching elements of the upper arm of the first or second leg in the set in the on state A control circuit that first turns off the first capacitor or the switching element to which the second capacitor is connected in parallel among the switching elements of the lower arm of the second or first leg, Converter.   In the control circuit, a detection value of voltage, current or power output from the side between the third and fourth terminals or a detection value of voltage, current or power input from the side between the first and second terminals is a target. The third capacitor or the third capacitor or the second capacitor so that the energy input from the first and second terminals is accumulated in the inductance means during a period in which the switching elements of the first circuit in the set are in an ON state so as to approach the value. The switching element of the second circuit that has been made conductive in the forward direction before turning off the switching element of the first circuit to be turned off first is made conductive in the forward direction by the switching element connected in parallel with the fourth capacitor. The converter according to claim 1, wherein the converter is turned off.   In the control circuit, a detection value of voltage, current or power output from the side between the third and fourth terminals or a detection value of voltage, current or power input from the side between the first and second terminals is a target. Energy that is input from the first and second terminal sides during a period in which the switching elements of the first circuit in the set are in an ON state so as to approach the value, through the inductance means, the third and fourth terminals 3. The converter according to claim 1, wherein the switching element of the second circuit is not electrically connected in a forward direction so as to be supplied to the side. 4.   The control circuit transmits energy input from the first and second terminal sides during the period in which the switching elements of the first circuit in the set are in an on state via the inductance means to the third and fourth terminal sides. From the operation of switching the switching element of the first circuit so that the switching element of the first circuit is pulse-controlled so that the switching element of the second circuit is not conducted in the forward direction. The switching element of the second circuit to which the third capacitor or the fourth capacitor is connected in parallel is made to conduct in the forward direction so that the energy input from the first and second terminals is stored in the inductance means. The switching element of the second circuit that is conducted in the forward direction before turning off the switching element of the first circuit that is turned off first. The operation is switched to the operation to turn off the detection value of the voltage, current or power output from the side between the third and fourth terminals, or the detection of the voltage, current or power input from the side between the first and second terminals. 4. The converter according to claim 1, wherein the value is brought close to a target value.   The control circuit includes the third capacitor or the second capacitor so that energy input from the first and second terminal sides is accumulated in the inductance means during a period in which the switching elements of the first circuit in the set are in an ON state. A switching element of the second circuit connected in parallel with four capacitors is made to conduct in the forward direction, and the second circuit is made to conduct in the forward direction before turning off the switching element of the first circuit to be turned off first. Energy input from the first and second terminal sides during the period in which the switching elements of the first circuit in the set are in the ON state from the operation of performing pulse control of the switching elements of the second circuit to turn off the switching elements In the forward direction so that the switching element of the second circuit is supplied to the third and fourth terminal sides via the inductance means. Switching to an operation that does not pass, the detected value of voltage, current, or power output from the side between the third and fourth terminals, or the detected value of voltage, current, or power input from the side between the first and second terminals The converter according to any one of claims 1 to 3, wherein the value is made close to a target value. The combined capacitance of the parallel capacitor and the first capacitor or the second capacitor connected in parallel to the switch element of the switching element of the first circuit that is turned off first among the switching elements of the first circuit that form a set is: Greater than the capacitance of the parallel capacitor connected in parallel to the switching element of the switching element of the first circuit to be turned off later;
The transformer is configured such that the voltage across the parallel capacitor connected in parallel to the switch element of the switching element of the upper or lower arm in the same leg as the switching element of the switching element of the first circuit to be turned off later is near zero. Having an exciting inductance for passing an exciting current of a magnitude that discharges the electric charge of the parallel capacitor so as to lower,
The control circuit has both ends of the parallel capacitor connected in parallel to the switching elements of the other upper or lower arm switching elements in the same leg as the switching elements of the switching elements of the first circuit to be turned off later by the exciting current. A period is provided in which both the switching element of the switching element of the first circuit to be turned off and the switching element of the other upper or lower arm switching element in the same leg are turned off until the voltage drops to near zero. A converter according to any one of claims 1 to 5. The anti-parallel diode connected in parallel to the switching element of the switching element of the first circuit includes a built-in diode of the switching element of the first circuit, a diode externally attached separately from the switching element of the first circuit, Or a combination thereof, and the parallel capacitor connected in parallel to the switching element of the switching element of the first circuit includes a parasitic capacitance of the switching element of the first circuit, and a switching element of the first circuit. Is a separate external capacitor, or a combination of these,
The unidirectional element connected in parallel to the switching element of the switching element of the second circuit includes a built-in diode of the switching element of the second circuit and an external diode separately from the switching element of the second circuit Or a combination thereof, and a parallel capacitor connected in parallel to the switching element of the switching element of the second circuit is connected to the parasitic capacitance of the switching element of the second circuit and the switching element of the second circuit. The converter according to any one of claims 1 to 6, wherein the converter is an external capacitor or a combination thereof. Switching of the first circuit in which the first capacitor is connected in parallel with the first capacitor as the upper and lower arms of the first or second leg of the first circuit and the second circuit in which the second capacitor is connected in parallel The device is connected,
The bridge connection circuit of the second circuit includes the switch element in which the unidirectional element and the parallel capacitor are connected in parallel, and the switching element of the second circuit is an upper and lower arm, and a third terminal and a fourth terminal And a switching element of the second circuit, wherein the third capacitor is connected in parallel as upper and lower arms of the third or fourth leg, respectively. A switching element of the second circuit to which the fourth capacitor is connected in parallel;
The control circuit alternately turns on and off a pair of switching elements of the second circuit of the upper arm of the third or fourth leg and switching elements of the second circuit of the lower arm of the fourth or third leg. The direct current input from the third and fourth terminal sides is converted into alternating current and output from the second circuit, and the on-off control is alternately performed on the switching elements of the second circuit in the set. Among the switching elements of the second circuit of the upper arm of the third or fourth leg and the switching elements of the second circuit of the lower arm of the fourth or third leg that form a pair, the third capacitor or the fourth 8. A bidirectional converter comprising the converter according to claim 1, wherein the switching element of the second circuit to which a capacitor is connected in parallel is turned off first.

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