WO2014098221A1

WO2014098221A1 - Converter, and bidirectional converter

Info

Publication number: WO2014098221A1
Application number: PCT/JP2013/084262
Authority: WO
Inventors: 基久人見
Original assignee: オリジン電気株式会社
Priority date: 2012-12-21
Filing date: 2013-12-20
Publication date: 2014-06-26
Also published as: JP2014124050A; JP5992820B2

Abstract

　Provided are a converter and a bidirectional converter in which switching losses are reduced.　In this converter and bidirectional converter, when the percentage of time that both switching elements forming a set in a first or second circuit (1, 2, 22) are on is low, after one switching element (S4 or S5) among the conducting set of switching elements (S1 and S4 or S5 and S8) of the second or first circuit (2, 22, 1) has been switched off in advance, the switching element (S5, S4) of the second or first circuit (2, 22, 1) is allowed to conduct in the forward direction and then switched off while an excitation current from a transistor (11) flows in a primary or secondary side circulation path, and zero-voltage switching of the switching elements (S2 and S1 or S8 and S7) that are subsequently switched off is implemented by the flow of current through the primary or secondary side circulation path, the current being larger than the excitation current as a result of being superimposed with the influence of the resonance effect from a secondary or primary side capacitor and an inductance means.

Description

Converter and bidirectional converter

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 for 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. There is a DC-DC converter that generates a high-frequency AC voltage rectangular wave, boosts it with a transformer, and performs full-wave rectification (see, for example, Patent Document 1). In addition, there is a type in which an input DC voltage is converted to AC by duty ratio control of an inverter, and the obtained AC is transformed by a transformer and rectified to output a DC voltage (see, for example, Patent Document 2).

Furthermore, examples of converters and bidirectional converters that can deal with a wide range of input / output voltage currents and that reduce switching loss are shown in FIGS. 1 and 11 of Japanese Patent Application No. 2012-223133, which is an earlier application of the present applicant. There are converters and bidirectional converters. In this converter and the bidirectional converter, for example, when the energy input from the first terminal T1 and the second terminal T2 side is supplied to the third terminal T3 and the fourth terminal T4 side, the two operations are switched. Can be used for a wide range of input / output voltage and current. The first of the two operations described above is performed while the switching elements S1 and S4 or S2 and S3 of the first circuit 1 that are paired are on while the switching elements S6 and S5 of the second circuit 2 are on. And the secondary winding 11b is short-circuited to store energy in the inductance means L, and then the switching element S6 or S5 is turned off to transfer the energy stored in the inductance means L to the third terminal T3 and the fourth terminal. Supply to the T4 side. In the second operation, the bridge connection circuit of the second circuit 2 is caused to function as a full-bridge rectifier circuit.

In this converter and the bidirectional converter, in the above two operations, when the energy input from the first terminal T1 and the second terminal T2 side is supplied to the third terminal T3 and the fourth terminal T4 side, 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 are turned on and off alternately. At this time, one switching element connected to the first or second capacitor in parallel is turned off first, and then the other switching element is turned off later.

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

However, in the above-described converter and bidirectional converter, when the bridge connection circuit of the second circuit 2 on the output side is operated so as to function as a full-bridge rectifier circuit, for example, when the load is light, the first If the ratio of the time during which both of the switching elements S1 and S4 constituting the set of the circuit 1 are on is reduced, the current flowing through the switching element S1 after the switching element S4 is turned off may oscillate. is there. This is because it is affected by the resonance operation by the capacitor on the secondary winding 11b side of the transformer 11 and the inductance means L. In this case, the switching element S2 to be turned off later can be turned off after the switching element S2 to be turned on next is lowered to the zero voltage and then turned on, and switching loss may occur.

Therefore, an object of the present invention is to provide a converter and a bidirectional converter with reduced 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, a first circuit connected to the primary winding side, and a bridge connection At least two of the unidirectional elements to be connected 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 in the bridge connection circuit A second circuit connected to the secondary winding side, and a connection point side of the upper and lower arms of the first leg, each having a third capacitor and a fourth capacitor connected in parallel to the two switching elements. A connection point side in which the unidirectional elements are connected in series with the same polarity via the primary winding or in the bridge connection circuit between the upper leg and the connection point side of the upper and lower arms of the second leg Inductance means connected via the secondary winding between the other unidirectional elements connected in series with the same polarity in series; the first or second element; The switching element of the upper arm and the switching element of the lower arm of the second or first leg are turned on and off alternately to convert the direct current input from the first and second terminal sides into alternating current, and When the switching elements that are output from the first circuit are alternately turned on / off, the switching elements of the upper arm of the first or second leg that are in the on state and the second or first leg The switching element in which the exciting current of the transformer is turned off later from the primary winding after the switching element connected to the first or second capacitor in parallel among the switching elements of the lower arm is turned off first The switch element in which the third or fourth capacitor of the second circuit is connected in parallel is made to conduct in the forward direction while flowing in the primary side circulation path having The third capacitor, the parallel capacitor connected in parallel to the third capacitor, the fourth capacitor, the parallel capacitor connected in parallel to the third capacitor, and the inductance means are superimposed on each other. And a control circuit for flowing a current larger than the exciting current to the primary-side circulation path.

The converter and bidirectional converter of the present invention can reduce switching loss.

It is explanatory drawing of the converter which concerns on the 1st Embodiment of this invention. 4 is a waveform diagram showing an example of voltages and currents of switching elements S1 to S4 of the first circuit 1 in the converter according to the first embodiment of the present invention. FIG. 4 is a waveform diagram showing an example of voltages and currents of switching elements S5 and S6 of the second circuit 2 and voltages and currents of unidirectional elements D7 and D8 in the converter according to the first embodiment of the present invention. FIG. It is a circuit diagram formed at each timing in the converter according to the first embodiment of the present invention. It is a block diagram of the bidirectional | two-way converter which concerns on the 2nd Embodiment of this invention.

(First embodiment)
A converter according to a first embodiment of the present invention will be described. FIG. 1 is an explanatory diagram of a converter according to the first embodiment of the present invention, FIG. 1 (a) is a configuration diagram of the converter according to the first embodiment of the present invention, and FIG. 1 (b) is the present invention. It is explanatory drawing of the drive timing of the switching element of the converter which concerns on 1st Embodiment. As shown in FIG. 1A, the converter includes a transformer 11, a first circuit 1 connected to the primary winding 11a side of the transformer 11, and a second circuit connected to the secondary winding 11b side of the transformer 11. 2 circuit 2, inductance means L, and control circuit 3. 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.

DC power from an external power supply is input to the first terminal T1 and the second terminal T2. 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 T2, 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 becomes the circuit of.

The first leg 12 and the second leg 13 of the first circuit 1 are respectively connected in parallel between the first terminal T1 and the second terminal T2. 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 (a), switching elements S1 to S4 include switching elements Q1 to Q4 including antiparallel diodes D1 to D4 and parallel capacitors C1 to C4, respectively. 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, the anti-parallel diodes D1 to D4 connected in parallel to the switching elements Q1 to Q4 may use the built-in diodes of the switching elements S1 to S4 as shown in FIG. An external diode may be used separately from the switching elements S1 to S4, 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. Alternatively, an externally attached capacitor may be used, or a combination thereof may be used.

The first capacitor Ca and the second capacitor Cb are 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. 1A, the first capacitor Ca and the second capacitor Cb are 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.

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

In FIG. 1 (a), 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 the built-in diodes of the switching elements S5 and S6 as shown in FIG. 1A, and are externally attached separately from the switching elements S5 and S6. Diodes may be used, 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. 1A, and use capacitors externally attached separately from the switching elements S5 and S6. Or a combination thereof.

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.

Next, 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. 1A, 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. One end may be connected to the connection point side of the upper and lower arms of the second leg 13, and the other end may be connected to the primary winding 11 a side of the transformer 11. 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, respectively, and performs on / off control of each switching element. In the converter of FIG. 1A, 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 respectively one. Turns on and off alternately in pairs. For example, among the switching elements S1 and S4 of the first circuit 1 to be paired, the switching element S4 to which the second capacitor Cb is connected in parallel is turned off first, and then the switching element S1 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 to which the first capacitor Ca is connected in parallel is turned off first, and then the switching element S2 is turned on later. To turn off.

In addition, the control circuit 3 sets the switching element S4 or S3 to be turned off first even when the ratio of the time when both of the switching elements S1 and S4 or S2 and S3 that are the set of the first circuit 1 are on is small. When turning off, the switching element S5 or S6 of the second circuit 2 is made conductive. Then, the switching element S5 or S6 of the second circuit 2 that is turned on before turning off the switching element S1 or S2 to be turned off later is turned off.

Note that the control circuit 3 performs on / off control of the switching elements S5 and S6 of the second circuit 2 during the period in which the switching elements S1 and S4 or S2 and S3 of the pair of the first circuit 1 are simultaneously turned on. A wide range of input / output voltage currents can be handled by switching between the operation of causing the two circuits to function as a rectifier circuit and the operation of causing the secondary winding 11b to be in a short circuit state.

In the operation of allowing the former second circuit to function as a rectifier circuit, the switching element S5 or S6 of the second circuit 2 is switched on during the period when the switching elements S1 and S4 or S2 and S3 are simultaneously turned on. The power input from the first terminal T1 and the second terminal T2 side without conducting in the forward direction is supplied from the inductance means L via the unidirectional elements D5 and D8 or D6 and D7 to the third terminal T3 and the fourth terminal. Supply to the T4 side.

In the operation of short-circuiting the secondary winding 11b, the switching element S1 and S4 or the switching element S6 or S5 of the second circuit 2 is turned on during the period in which the switching elements S1 and S4 or S2 and S3 are simultaneously turned on. The power input from the second terminal T2 side is temporarily stored in the inductance means L and then turned off, and the energy stored in the inductance means L is supplied to the third terminal T3, the fourth through the unidirectional elements D5, D8. Supply to the terminal T4 side.

The output voltage detection means 18 of the second circuit 2 shown in FIG. 1A 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 performs pulse control for modulating the pulse width, frequency, and the like of the switching elements S1 to S4 of the first circuit 1 so that the output voltage detection value approaches the target voltage value according to the load condition. 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 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. Percentage of time during which both switching elements S1 and S4 or S2 and S3, which are a set of the first circuit 1 on the input side, are turned on when power is supplied from the first circuit 1 side to the second circuit 2 side The operation of the converter when is small will be described.

FIG. 1B 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 the converter according to the first embodiment of the present invention. is there.

In FIG. 1B, it is assumed that an ON signal is given to the switching elements S1 and S4 of the first circuit 1 that are paired at time t1, and an ON signal of the switching element S5 is given between times t1 and t2. . In FIG. 1B, the ON signal of the switching element S5 is given between times t1 and t2. However, in order to prevent the oscillation of the current flowing through the primary winding 11a, the switching element Q5 is moved forward. It is only necessary that the ON signal is given at the time point t3 when the connection is made.

FIG. 2 is a waveform diagram showing an example of voltages and currents of the switching elements S1 to S4 of the first circuit 1 in the converter according to the first embodiment of the present invention, and FIG. 3 is a waveform diagram showing the first embodiment of the present invention. It is a wave form diagram showing an example of voltage and current of switching elements S5 and S6 of the 2nd circuit 2, and voltage and current of unidirectional elements D7 and D8 in a converter concerning a form. FIG. 4 is a circuit diagram formed at each operation timing in the converter according to the first embodiment of the present invention.

Here, in the current waveforms shown in FIGS. 2 and 3, 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, The current flowing in the reverse direction through the switching elements S1 to S4 and the switching elements S5 and S6 in the second circuit 2 and the current flowing in the forward direction through the unidirectional elements D7 and D8 are negative.

As shown in FIG. 2, at time t1, the current of the switching element S1 and the current of the switching element S4 are on the negative side, that is, the diodes D1 and D4, but then the positive side, that is, the switching elements Q1 and Q4 are forward. Conducted to.

FIG. 4 (a) shows the flow of current when the switch elements Q1 and Q4 after the time t1 are conducting in the forward direction. On the primary winding 11a side of the transformer 11, current flows through the switching elements Q1 and Q4, and on the secondary winding 11b side, current flows through the unidirectional elements D5 and D8. 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 t2, for example, the control circuit 3 is paired 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 2 approaches the target value. An off signal is given to switching element S4 which turns off first among switching elements S1 and S4 of the 1st circuit 1. FIG. For this reason, as shown in FIG. 2, the switch element Q4 is turned off with a relatively large current value. When the switch element Q4 is turned off at time t2, as shown in FIG. 4B, 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 are charged. A current flows in the direction 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. Therefore, 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 rise of the voltage across the switching element S4 is moderated, whereby the switching of the first circuit 1 is performed. The switching loss when the element S4 is off is reduced. Similarly, the switching element S3 is connected to the parallel capacitor C3 in parallel with the first capacitor Ca to reduce the switching loss when the switching element S3 is off. Note that the current on the secondary winding 11b side continues to flow through the unidirectional elements D5 and D8 from time t1.

When the parallel capacitor C3 and the first capacitor Ca are discharged and the parallel capacitor C4 and the second capacitor Cb are charged, the antiparallel diode D3 connected in parallel to the switch element Q3 is turned on. On the primary winding 11a side, the primary winding 11a and the primary winding 11a are arranged in the same direction as the current flowing in the primary winding 11a and the inductance means L immediately before by the energy accumulated in the inductance means L and the exciting current of the transformer 11. A primary side circulation path having a switching element S1 to be turned off later, here, as shown in FIG. 4C, is formed by a primary winding 11a, an antiparallel diode D3, a switching element Q1, and an inductance means L. Current flows through the path.

The current on the secondary winding 11b side continues to flow in the forward direction through the unidirectional elements D5 and D8 from time t1, but when the forward conduction in the unidirectional element D5 ends at time t3, the switch element Start to flow forward in Q5. The ON signal of the switching element S5 is given to the unidirectional element D5 at the time t3 when the forward conduction ends so that the current flowing through the primary-side circulation path does not vibrate.

When the unidirectional element D5 conducts in the forward direction, as shown in FIG. 4C, the exciting current of the transformer 11 flows through the switch element Q5 and the unidirectional element D7 on the secondary winding 11b side. For this reason, the exciting current of the transformer 11 is shunted to the primary circulation path on the primary winding 11a side and the secondary winding 11b side.

Since the exciting current of the transformer 11 is also shunted to the secondary winding 11b side, the current flowing through the primary side circulation path becomes very small as shown by the currents of the switching elements S1 and S3 in FIG. If the switching element S1 to be turned off later in this state is turned off, zero voltage switching may not be realized when the other switching element S2 of the same leg 12 as the switching element S1 is turned on. After the switching element S1 is turned off, the capacitor C1 is charged by the exciting current of the transformer 11, and the switching element S2 is turned on in the zero voltage state unless the capacitor C2 of the switching element S2 to be turned on is discharged to zero voltage. It is because it cannot be made.

In the present invention, before turning off the switching element S1 to be turned off later, the switching element S5 in the conductive state is turned off, and the capacitors on the secondary winding 11b side, that is, the capacitor C5, the third capacitor Cc, and the capacitor C6. The current flowing through the primary-side circulation path during charging and discharging of the capacitors C1 and C2 is increased by utilizing the resonance operation of the combined capacitance of the fourth capacitor Cd and the inductor L.

This operation will be described specifically. As shown in FIG. 1B, the drive signal for the switching element S5 is turned off at time t4. Then, as shown in FIG. 4 (d), on the secondary winding 11b side, a current for charging the capacitor C5 and the third capacitor Cc and discharging the capacitor C6 and the fourth capacitor Cd flows, and the switching of FIG. The voltage and current waveforms of the elements S5 and S6 are waveforms that reflect the resonant operation of the inductance means and the secondary side capacitor. The resonance current on the secondary winding side 11 b is superimposed on the current flowing through the primary side circulation path on the primary winding 11 a side via the transformer 11. As shown in FIG. 4D, a current continuously flows in the primary circulation path on the primary winding 11a side, and the current waveform of the switching element S1 in FIG. 2 is the exciting current value of the transformer 11 until time t4. The current value increased after time t4. That is, a current larger than the excitation current caused by the superposition due to the resonance effect of the combined capacitance of the capacitor on the secondary winding 11b side and the inductance means L flows through the primary side circulation path.

When the switching element S1 to be turned off later is turned off at the time t5, the switching element S1 to be turned off later is turned off, as shown in FIG. 4E, on the primary winding 11a side, the capacitor C1 is connected via the diode D3. , A current for charging / discharging C2 flows. Since the current flowing in the primary circulation path at time t5 is made large enough to charge and discharge the capacitors C1 and C2 using the above resonance operation, the voltage of the switching element S2 in FIG. The waveform has dropped to almost zero volts after time t5. Here, the period from time t4 to t5 from the start of the resonance operation of the combined capacitance of the capacitor on the secondary winding 11b side and the inductance means L to the time when the switching element S1 is turned off is the resonance one in the resonance operation described above. The time is within 1/2 of the cycle. The current obtained by superimposing the resonance current on the excitation current flowing through the primary side circulation path rises up to 1/2 of one resonance cycle after the start of resonance operation, and reaches a peak value at 1/2 of one resonance cycle. It is because it decreases after that. On the other hand, on the secondary winding 11b side in FIG. 4E, the capacitor C5 and the third capacitor Cc are discharged, and a current that charges the capacitor C6 and the fourth capacitor Cd flows.

When the charging and discharging of the parallel capacitors C1 and C2 are completed at time t6, the antiparallel diode D2 becomes conductive as shown in FIG. On the primary winding 11a side, a current flows from the primary winding 11a through the antiparallel diodes D3 and D2 in the same direction as the current flowing in the primary winding 11a immediately before time t6. On the other hand, on the secondary winding 11b side, the capacitor C5, the third capacitor Cc, the capacitor C6, the fourth capacitor Cd, and the inductor L are recharged to recharge the capacitor C5 and the third capacitor Cc. A current that discharges C6 and the fourth capacitor Cd flows. At time t6 when the antiparallel diode D2 starts to conduct, the current on the secondary winding 11b side is discharged from the capacitor C5 and the third capacitor Cc shown in FIG. It may be in a state where a current for charging the capacitor Cd is flowing.

At time t7, as shown in FIG. 2, an ON signal is given to the switching elements S2 and S3 of the first circuit 1 which is the other set. At time t7, as shown in FIG. 3, the currents of the switching elements S2 and S3 are flowing through the negative side, that is, the antiparallel diodes D2 and D3, but the currents of the switching elements S2 and S3 are thereafter the positive side, that is, the switching element. It flows through Q2 and Q3. FIG. 4G shows an operation in which the current on the primary winding 11a side flows through the switch elements Q2 and Q3. At this time, the current on the secondary winding 11b side flows through the unidirectional elements D6 and D7. As in the case of FIG. 4A, 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.

Since the antiparallel diodes D2 and D3 connected in parallel to the switch elements Q2 and Q3, respectively, are turned on immediately before the switch elements Q2 and Q3 are turned on in the forward direction, as shown in FIG. The switching elements S2 and S3 realize zero voltage switching when turned on. As described above, even when the excitation current flowing through the primary side circulation path is small, by increasing the current flowing through the primary side circulation path using the resonance operation, the switching element that is turned off later is turned on. Zero voltage switching can be realized.

About the operation | movement of switching element S2, S3 of the 1st circuit 1 used as the other group after time t7, it is made to operate similarly to the time t7 of switching element S1, S4 used as the above-mentioned group. 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. Next, the switch element Q6 is turned on, and the switch element Q6 is turned off in a state where the exciting current of the transformer 11 is shunted to the primary and

secondary windings

11a and 11b. Switch element that turns off the current flowing in the primary-side circulation path in a state in which the current flowing through the primary-side circulation path is increased by utilizing the resonance operation of the combined capacitance of the capacitor on the secondary winding 11b side after the switch element Q6 is turned off and the inductance means L Turn off Q2. By operating in this way, even when the excitation current flowing through the primary-side circulation path is small, such as when the ratio of the time during which both the switching elements S1 and S4 or S2 and S3 are on is small, Therefore, it is possible to secure a current necessary for zero voltage switching of the switching element to be turned off.

Here, synchronous rectification may be performed by giving an ON signal to the switching element S5 during a period in which the unidirectional element D5 of the second circuit 2 conducts in the forward direction. Usually, since the voltage drop of the switch element S5 during reverse conduction is smaller than the voltage drop during forward conduction of the unidirectional element D5, conduction loss can be reduced by conducting the switch element Q5 in the reverse direction. it can. The same applies to the unidirectional element D6 and the switch element Q6 of the second circuit 2. Furthermore, in the description of the first embodiment, the diodes are shown as the unidirectional elements D7 and D8 of the second circuit 2. However, the present invention is not limited to this example, and any element that conducts current in one direction may be used. . For example, as the unidirectional elements D7 and D8, switching elements S7 and S8 having the unidirectional elements D7 and D8 attached externally or having internal diodes D7 and D8 may be used. As with the unidirectional elements D5 and D6 described above, the switch elements Q7 and Q8 having a small voltage drop during reverse conduction during the period in which the unidirectional elements D7 and D8 conduct in the forward direction are conducted by conducting in the reverse direction. Loss can be reduced.

As shown in FIG. 1 (b), during the period Td in which the drive signals of the switching elements S1 and S2 that are turned off later are both off signals, the voltage across the terminals is zero in order to realize zero voltage switching of the switching element S1 or S2. It will be about the period to fall to. 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.

As shown in FIGS. 1B and 2, at time t7, an ON signal that is a drive signal for the switching elements S2 and S3 of the first circuit 1 is simultaneously applied, and thereafter, the switching element Q2 and the switching element Q3. Shows an example of the operation that starts to conduct in the forward direction. However, without being limited to an example of the operation of the above-described embodiment, the time t7 when the ON signals of the switching elements S2 and S3 are applied may be a period in which the antiparallel diodes D2 and D3 are conductive. Further, the time point at which the ON signals of the switching elements S2 and S3 are applied may coincide with the time point at which the switch element Q2 and the switch element Q3 start to conduct in the forward direction at time t7. When the voltage drop at the time of reverse conduction of the switching elements Q2 and Q3 is smaller than the voltage drop at the time of forward conduction of the antiparallel diodes D2 and D3, an ON signal of the switching elements S2 and S3 is given to switch the switching elements S2, The conduction loss of S3 can be reduced. The same applies to the case of the switching elements S1 and S4 of the first circuit 1 as 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.

(Second Embodiment)
FIG. 5 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. 5, the second circuit 22 has a circuit structure in which the switching elements are 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. Further, as in FIG. 1, in FIG. 5, the inductance means L is connected to the primary winding 11a side, but 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. 5, 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. 5, and are separated from the switching elements S5 to S8 of the second circuit 22. 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. Further, third and fourth capacitors Cc and Cd are connected in parallel to the switching elements S5 and S6 that are turned off first.

When supplying power 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 the ratio of the time during which both of the switching elements S5 and S8 or S6 and S7 that are a set of the second circuit 22 are on is small, the switching that is turned off first among the switching elements that are the set of the second circuit 22 After the element S5 or S6 is turned off, the switching element S4 or S3 while the exciting current of the transformer 11 flows through the secondary circulation path having the secondary winding 11b and the switching element S8 or S7 to be turned off later. In the forward direction. Then, before turning off the switching element S8 or S7 to be turned off later, the switching element S4 or S3 is turned off to turn off the capacitor C3 on the primary winding 11a side, the first capacitor Ca, the capacitor C4, and the second capacitor. Utilizing the resonance operation of the combined capacitance of Cb and the inductor L, the current flowing through the secondary-side circulation path when charging and discharging the capacitors C7 and C8 is increased. By increasing the current flowing through the secondary circulation path, the parallel capacitor C8 or C7 can be discharged until it reaches zero voltage, so that zero voltage switching of the switching element S8 or S7 that is turned off later can be realized.

Similar to the first embodiment, the switching elements S5, S6 are in a period in which the unidirectional elements (antiparallel diodes) D5, D6 or the antiparallel diodes D3, D4 of the second circuit 22 or the first circuit 1 are forward-conductive. Alternatively, synchronous rectification may be performed by giving an ON signal to S3 and S4. Normally, the voltage drop of the switch elements Q5 and Q6 during reverse conduction is smaller than the voltage drop during forward conduction of the unidirectional elements D5 and D6, so that by switching the switch elements Q5 and Q6 in the reverse direction, The conduction loss can be reduced. The same applies to the antiparallel diodes D3 and D4 and the switch elements Q3 and Q4 of the first circuit 1. Similarly, the switching elements S7 and S8 of the second circuit 22 or the switching elements S1 and S2 of the first circuit 1 have the unidirectional elements (antiparallel diodes) D7 and D8 or the antiparallel diodes D1 and D2 in the forward direction. The conduction loss can be reduced by conducting the switch elements Q7, Q8 or Q1, Q2 having a small voltage drop during reverse conduction during the conduction period in the reverse direction.

As described above, in the present invention, the current when 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 is turned off is used as the capacitor of the second circuit or the first circuit. The zero voltage switching is realized 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 by increasing the resonance by the resonance operation of the capacitor and the inductance means L. The resulting switching loss is reduced.

In the converter and the bidirectional converter according to the present invention, the

control circuits

3 and 23 modulate the pulse width and frequency of the switching element of the first circuit 1 or the second circuit 22, and the second circuit 22 or the second circuit on the output side. In one circuit 1, it is possible to deal with a wide range of input / output voltage currents by changing the on / off timing of the switching elements. Furthermore, among the switch elements that form the first or second circuit set on the input side, the capacitance of the capacitor that is connected in parallel to the switch element that is turned off first is the capacitance of the capacitor that is connected in parallel to the switch element that is turned off later. By making it larger than the capacitance, it is possible to reduce the switching loss that occurs when the switching element of the first circuit or the second circuit is turned off. Similarly, the switching loss generated at the time of OFF can be reduced by connecting a capacitor in parallel with the switching element of the output-side second circuit or the first circuit to be turned ON / 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 make the excitation current have an appropriate magnitude is also included in the excitation inductance of the transformer 11 described above. . 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 excitation inductance of the transformer 11 can be adjusted in the transformer structure by, for example, 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.

In the electric circuit of the present invention, the connection point means a part that is electrically connected and at the same potential, and does not mean 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

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 the bridge connection circuit A second capacitor connected to the secondary winding side, and having a third capacitor and a fourth capacitor connected in parallel to at least two of the switching elements,
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 After switching off the switching element having the first or second capacitor connected in parallel among the switching elements of the lower arm of the second or first leg, the exciting current of the transformer is connected to the primary winding. A switch element in which the third or fourth capacitor of the second circuit is connected in parallel while flowing in a primary-side circulation path having the switching element to be turned off later. The third capacitor, the parallel capacitor connected in parallel to the third capacitor, the fourth capacitor, the parallel capacitor connected in parallel to the third capacitor, and the inductance means are turned off. And a control circuit for flowing a current larger than the excitation current caused by the influence of the current to the primary-side circulation path.
The control circuit gives an ON signal to the switching element connected in parallel with the unidirectional element when the unidirectional element connected in parallel with the third or fourth capacitor is conducting. The converter according to claim 1, characterized in that:
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 claim 1, wherein the converter is a separately attached 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. The third or fourth capacitor is connected in parallel between the switching element of the second circuit of the upper arm of the third or fourth leg and the switching element of the second circuit of the lower arm of the fourth or third leg forming a set. After the switching element of the second circuit is turned off first, the exciting current of the transformer flows into the secondary side circulation path having the secondary winding and the switching element of the second circuit to be turned off later. During this time, the switch element in which the first or second capacitor of the first circuit is connected in parallel is made to conduct in the forward direction and then turned off, and the first capacitor and the parallel capacitor connected in parallel to the first capacitor And flowing a current larger than the excitation current caused by the resonance effect of the second capacitor, the parallel capacitor connected in parallel to the capacitor, and the inductance means to the secondary circulation path. A bidirectional converter comprising the converter according to any one of claims 1 to 3.