JP2022153069A - Power conversion device, power conversion system, control method, and program - Google Patents

Abstract

To reduce a possibility of an abnormal operation in a DC/DC converter.SOLUTION: A power conversion device 3 includes a DC/DC converter 1, and a control circuit 2. The DC/DC converter 1 has a pair of first ends 11 and 12, a first winding N1, one or more first switching elements Q1-Q4, one or more first diodes D1-D4, a pair of second ends 13 and 14, a second winding N2, one or more second switching elements Q5-Q8, and one or more second diodes D5-D8. In a synchronous rectification control, the control circuit 2 switches the second switching elements Q5-Q8 from OFF to ON at a second timing delayed by a delay time from a first timing at which the first switching elements Q1-Q4 are switched from ON to OFF.SELECTED DRAWING: Figure 1

Description

The present disclosure generally relates to a power conversion device, power conversion system, control method and program. More specifically, the present disclosure relates to a power conversion device including a DC/DC converter, a power conversion system, and a control method and program for controlling the operation of this DC/DC converter.

The resonance type power supply device (power conversion device) described in Patent Document 1 applies a pulse-like voltage to the transformer and the resonance element by switching the input voltage with the primary side switching element, and the switching is performed by the secondary side switching element. to control the output voltage. In the resonant power supply, the command value of the output voltage is set to one or less than the turn ratio of the amplitude of the pulsed voltage divided by the turn ratio of the transformer, the switching frequency for the set period is obtained, and the switching frequency is set to the obtained switching frequency. It has a control function of correcting the gate signal of the secondary side switching element based on this.

JP 2017-195664 A

An object of the present disclosure is to provide a power conversion device, a power conversion system, a control method, and a program that can reduce the possibility of abnormal operation of a DC/DC converter.

A power converter according to an aspect of the present disclosure includes a DC/DC converter and a control circuit that controls operation of the DC/DC converter. The DC/DC converter includes a pair of first ends, a first winding, one or more first switching elements, one or more first diodes, a pair of second ends, and a second winding. , one or more second switching elements, and one or more second diodes. The first switching element is electrically connected between the first winding and the pair of first ends. One or more first diodes are connected in parallel with one or more first switching elements in one-to-one correspondence. The second winding constitutes an isolation transformer together with the first winding. The second switching element is electrically connected between the second winding and the pair of second ends. One or more of the second diodes are connected in parallel with one or more of the second switching elements in a one-to-one correspondence. The control circuit performs synchronous rectification control to turn on and off both the first switching element and the second switching element. In the synchronous rectification control, the control circuit switches the second switching element from off to on at a second timing delayed by a delay time from the first timing for switching the first switching element from on to off.

A power conversion system according to an aspect of the present disclosure includes the power converter and an inverter. The inverter is electrically connected to the pair of first ends or the pair of second ends of the DC/DC converter.

A control method according to one aspect of the present disclosure is a control method for controlling the operation of a DC/DC converter. The DC/DC converter includes a pair of first ends, a first winding, one or more first switching elements, one or more first diodes, a pair of second ends, and a second winding. , one or more second switching elements, and one or more second diodes. The first switching element is electrically connected between the first winding and the pair of first ends. One or more first diodes are connected in parallel with one or more first switching elements in one-to-one correspondence. The second winding constitutes an isolation transformer together with the first winding. The second switching element is electrically connected between the second winding and the pair of second ends. One or more of the second diodes are connected in parallel with one or more of the second switching elements in a one-to-one correspondence. The control method includes performing synchronous rectification control to turn on and off both the first switching element and the second switching element. In the synchronous rectification control, the second switching element is switched from off to on at a second timing delayed by a delay time from the first timing for switching the first switching element from on to off.

A program according to an aspect of the present disclosure is a program for causing one or more processors to execute the control method.

Advantageously, the present disclosure can reduce the possibility of abnormal operation of the DC/DC converter.

FIG. 1 is a circuit block diagram of a power conversion system according to Embodiment 1. FIG. FIG. 2 is an explanatory diagram of first synchronous rectification control in high-frequency switching of the power conversion system of the same. FIG. 3 is a circuit diagram of a main part of the power conversion system same as the above. FIG. 4 is an explanatory diagram of second synchronous rectification control in high-frequency switching of the power conversion system of the same. FIG. 5 is an explanatory diagram showing control according to a comparative example for the same power conversion system. FIG. 6 is an explanatory diagram of first synchronous rectification control in low-frequency switching of the power conversion system of the same. FIG. 7 is an equivalent circuit diagram of main parts of the power conversion system according to the second embodiment. FIG. 8 is an explanatory diagram showing control of the power conversion system same as above. FIG. 9 is an explanatory diagram showing control of the power conversion system according to the third embodiment.

In each embodiment below, a power conversion device and a power conversion system of the present disclosure will be described with reference to the drawings. However, each embodiment described below is only a part of various embodiments of the present disclosure. Each of the embodiments described below can be modified in various ways according to design and the like as long as the object of the present disclosure can be achieved.

(Embodiment 1)
(Overview)
As shown in FIG. 1 , the power conversion device 3 of this embodiment includes a DC/DC converter 1 and a control circuit 2 . A control circuit 2 controls the operation of the DC/DC converter 1 .

The DC/DC converter 1 includes a pair of first ends 11 and 12, a first winding N1, one or more (four in FIG. 1) first switching elements Q1 to Q4, and one or more (in FIG. 1 4) first diodes D1 to D4, a pair of second ends 13, 14, a second winding N2, one or more (four in FIG. 1) second switching elements Q5 to Q8, and one or more (four in FIG. 1) second diodes D5 to D8. The first switching elements Q1-Q4 are electrically connected between the first winding N1 and the pair of first ends 11,12. One or more first diodes D1-D4 are connected in parallel with one or more first switching elements Q1-Q4 in one-to-one correspondence. The second winding N2 constitutes an isolation transformer Tr1 together with the first winding N1. The second switching elements Q5-Q8 are electrically connected between the second winding N2 and the pair of second ends 13,14. One or more second diodes D5-D8 are connected in parallel with one or more second switching elements Q5-Q8 in one-to-one correspondence. The control circuit 2 performs synchronous rectification control to turn on/off both the first switching elements Q1-Q4 and the second switching elements Q5-Q8. In the synchronous rectification control, the control circuit 2 controls the second switching elements Q5 to Q8 at the second timing delayed by the delay time tx (see FIG. 2) from the first timing for switching the first switching elements Q1 to Q4 from on to off. switch from off to on.

According to the present embodiment, by providing the delay time tx in the synchronous rectification control, it is possible to reduce the possibility that the current in the negative direction flows in the period when the current in the positive direction should flow in the second winding N2. It is possible to reduce the possibility that a current in the positive direction flows during a period in which a current in the negative direction should flow in the second winding N2. In this way, it is possible to reduce the possibility of a reverse current flowing through the second winding N2. That is, it is possible to reduce the possibility that the DC/DC converter 1 will operate abnormally.

In addition, by turning on the second switching elements Q5-Q8, current flows through the second switching elements Q5-Q8 instead of the second diodes D5-D8, so the current loss in the second diodes D5-D8 can be reduced. can.

In the following description, the first switching elements Q1-Q4 and the second switching elements Q5-Q8 may be simply referred to as switching elements Q1-Q8, respectively. Also, in the following description, the first diodes D1-D4 and the second diodes D5-D8 may be simply referred to as diodes D1-D8, respectively.

(detail)
(1) Configuration of Power Conversion System As shown in FIG. 1 , the power conversion system 10 includes a power conversion device 3 and an inverter 5 . The inverter 5 may be electrically connected to the first ends 11 and 12 or the second ends 13 and 14 of the DC/DC converter 1 . In this embodiment, the inverter 5 is electrically connected to the second ends 13 , 14 of the DC/DC converter 1 . Power conversion system 10 further comprises a detection circuit 4 and a chopper circuit 6 .

The power conversion system 10 is electrically connected between a power source and a power destination. The power conversion system 10 converts power input from a power supply source and outputs the converted power to a supply destination. The power conversion system 10 of this embodiment is capable of bi-directional power conversion. As such, a configuration that was a source of power at one point in time may be a destination of power at another point in time. Conversely, the configuration that was receiving power at one time may be the source of power at another time.

In FIG. 1, a storage battery B1 is electrically connected to the power conversion system 10 as a power supply source or supply destination. Storage battery B<b>1 as a power supply source supplies power to a load via power conversion system 10 . Storage battery B<b>1 as a power supply destination receives power from a power source such as a commercial power source via power conversion system 10 and is charged. Storage battery B1 is mounted, for example, in an electric vehicle. The power conversion system 10 is, for example, a power conditioner conforming to the CHAdeMO (registered trademark) specification.

As shown in FIG. 1, the DC/DC converter 1 is an insulating bidirectional DC/DC converter using an insulating transformer Tr1. More specifically, the DC/DC converter 1 is a CLLC resonance type bi-directional DC/DC converter that utilizes resonance by a first capacitor C1, a first inductor L1, a second inductor L2, and a second capacitor C2. A first inductor L1 and a second inductor L2 are leakage inductances of the isolation transformer Tr1.

The DC/DC converter 1 has an isolation transformer Tr1, a first capacitor C1 and a second capacitor C2. The DC/DC converter 1 also has first ends 11 , 12 and second ends 13 , 14 . Each of the first ends 11 , 12 and the second ends 13 , 14 may be a terminal, or may be a part of wiring that constitutes a circuit of the power conversion system 10 .

The DC/DC converter 1 is a switching type DC/DC converter, and has a plurality of (eight in FIG. 1) switching elements S1 to S8 (semiconductor switching elements). A first winding N1 of the isolation transformer Tr1 is electrically connected to first ends 11 and 12 via switching elements S1 to S4. A second winding N2 of the isolation transformer Tr1 is electrically connected to second ends 13 and 14 via switching elements S5 to S8. In the following description, the configuration closer to the first winding N1 than the second winding N2 is called the "primary side", and the configuration closer to the second winding N2 than the first winding N1 is called the "secondary side". sometimes called

The inverter 5 is a switching type inverter and has a plurality of (six in FIG. 1) switching elements S9 to S14 (semiconductor switching elements). The inverter 5 further has three inductors L3-L5.

Chopper circuit 6 is electrically connected between DC/DC converter 1 and storage battery B1. The chopper circuit 6 has an inductor L6 and a plurality of (two in FIG. 1) switching elements S15 and S16 (semiconductor switching elements).

Each switching element S1-S16 has a control terminal, a first main terminal and a second main terminal. A control terminal of each switching element S1 to S16 is electrically connected to the control circuit 2 . Each of the switching elements S1 to S16 is turned on and off according to a control signal (control voltage) given from the control circuit 2. FIG. In other words, the presence or absence of conduction between the first main terminal and the second main terminal is switched according to the control signal given from the control circuit 2 .

In this embodiment, as an example, each of the switching elements S1 to S16 is a MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor). More specifically, each switching element S1-S16 is an n-channel MOSFET. Here, the n-channel MOSFET is a normally-off Si-based MOSFET. A control terminal, a first main terminal and a second main terminal of each switching element S1 to S16 are a gate terminal, a drain terminal and a source terminal, respectively.

The control circuit 2 controls switching of the DC/DC converter 1, the inverter 5, and the chopper circuit 6 independently. The control circuit 2 performs PFM (Pulse Frequency Modulation) control on the switching elements S1 to S8. That is, the switching frequency of each switching element S1 to S8 is variable. Each switching element S1-S8 is switched at a common switching frequency. The closer the switching frequency is to the resonance frequency of the DC/DC converter 1, the greater the gain of the DC/DC converter 1 becomes. The resonance frequency of the DC/DC converter 1 is determined by a resonance circuit RC1 consisting of a first capacitor C1, a first inductor L1, a second inductor L2 and a second capacitor C2.

Each switching element S1-S16 includes a switching element and a diode. In FIG. 1, the switching elements Q1 to Q8 and the diodes D1 to D8 included in the switching elements S1 to S8 are denoted by reference numerals, and the switching elements and diodes included in the switching elements S9 to S16 are omitted.

The switching elements are turned on and off according to control signals (control voltages) supplied from the control circuit 2 .

Each diode is a parasitic diode of switching elements S1 to S16, which are MOSFETs. Each diode has an anode and a cathode. In each switching element S1 to S16, the anode of the diode is electrically connected to the second main terminal (source terminal), and the cathode of the diode is electrically connected to the first main terminal (drain terminal). there is That is, the diode is connected anti-parallel to the switching element.

The DC/DC converter 1 has a series circuit of switching elements Q1 and Q2, a series circuit of switching elements Q3 and Q4, a series circuit of switching elements Q5 and Q6, and a series circuit of switching elements Q7 and Q8. A series circuit of switching elements Q1, Q2 is electrically connected between the first ends 11,12. A series circuit of switching elements Q3, Q4 is electrically connected between the first ends 11,12. A series circuit of switching elements Q5, Q6 is electrically connected between the second ends 13,14. A series circuit of switching elements Q7, Q8 is electrically connected between the second ends 13,14.

The switching elements S1 and S3 are provided on the first end 11 side of the first ends 11 and 12, and the switching elements S2 and S4 are provided on the first end 12 side of the first ends 11 and 12. FIG.

A drain terminal of the switching element S1 is electrically connected to the first end 11 . A source terminal of the switching element S1 is electrically connected to a drain terminal of the switching element S2. A source terminal of the switching element S2 is electrically connected to the first end 12 .

A drain terminal of the switching element S3 is electrically connected to the first end 11 . A source terminal of the switching element S3 is electrically connected to a drain terminal of the switching element S4. A source terminal of the switching element S4 is electrically connected to the first end 12 .

A drain terminal of the switching element S5 is electrically connected to the second end 13 . A source terminal of the switching element S5 is electrically connected to a drain terminal of the switching element S6. A source terminal of the switching element S6 is electrically connected to the second end 14 .

A drain terminal of the switching element S7 is electrically connected to the second end 13 . A source terminal of the switching element S7 is electrically connected to a drain terminal of the switching element S8. A source terminal of the switching element S8 is electrically connected to the second end 14 .

A first winding N1 of the isolation transformer Tr1 is connected in series with the first capacitor C1. A series circuit of the first winding N1 and the first capacitor C1 is electrically connected between a connection point between the switching element S1 and the switching element S2 and a connection point between the switching element S3 and the switching element S4. there is

A second winding N2 of the isolation transformer Tr1 is connected in series with the second capacitor C2. A series circuit of the second winding N2 and the second capacitor C2 is electrically connected between a connection point between the switching element S5 and the switching element S6 and a connection point between the switching element S7 and the switching element S8. there is

In the isolation transformer Tr1, a first leakage inductance (first inductor L1) is formed on the primary side, and a second leakage inductance (second inductor L2) is formed on the secondary side. In the DC/DC converter 1, a resonance circuit RC1 (CLLC resonance circuit) is formed by a first capacitor C1, a first inductor L1, a second inductor L2, and a second capacitor C2.

The DC/DC converter 1 further includes capacitors C3 and C4. Capacitors C3 and C4 are, for example, electrolytic capacitors. A capacitor C3 is electrically connected between the first ends 11,12. A capacitor C4 is electrically connected between the second ends 13,14.

In chopper circuit 6 , the drain terminal of switching element S<b>15 is electrically connected to first end 11 . A source terminal of the switching element S15 is electrically connected to a drain terminal of the switching element S16. A source terminal of the switching element S16 is electrically connected to the first end 12 . The first end 12 is electrically connected to the negative terminal of the storage battery B1.

Inductor L6 is electrically connected between the positive terminal of storage battery B1 and the source terminal of switching element S15. The first end 11 is electrically connected to the positive terminal of the storage battery B1 via the switching element S15 and the inductor L6.

The chopper circuit 6 is a step-up/step-down chopper circuit capable of a step-down operation (step-down chopper operation) and a step-up operation (step-up chopper operation). When the chopper circuit 6 performs a step-up operation to convert the voltage of the storage battery B1 to a voltage higher than that of the storage battery B1, the switching element S15 is turned off, and the switching element S16 is alternately turned on and off at a high frequency. Thereby, the chopper circuit 6 functions as a boost chopper circuit.

Further, when the chopper circuit 6 performs a step-down operation to convert the voltage between the first terminals 11 and 12 of the DC-DC converter 1 to a voltage smaller than the voltage, the switching element S16 is turned off and the switching element S15 is turned on. , off alternately at high frequencies. Thereby, the chopper circuit 6 functions as a step-down chopper circuit.

The inverter 5 performs a DC/AC conversion operation of converting the DC voltage, which is the output voltage of the DC/DC converter 1, into an AC voltage, and also converts the AC voltage input to the inverter 5 into a DC voltage and outputs the DC voltage to the DC/DC converter 1. and an AC/DC conversion operation.

Inverter 5 is a three-phase inverter. The inverter 5 has six switching elements S9-S14 and three inductors L3-L5. The six switching elements S9-S14 of the inverter 5 are connected in a three-phase bridge configuration. In other words, the six switching elements S9 to S14 are composed of two switching elements S9 and S10 forming the upper and lower stages of the U phase, two switching elements S11 and S12 forming the upper and lower stages of the V phase, and a switching element S11 and S12 forming the upper and lower stages of the W phase. and two switching elements S13 and S14 forming the upper stage and the lower stage. The upper switching element and the lower switching element of each phase are connected in series. As a result, three sets of series circuits composed of two switching elements in the upper stage and the lower stage are formed, and these three sets of series circuits are connected in parallel with each other. The three sets of series circuits are electrically connected between the second ends 13,14. A connection point between the upper stage and the lower stage of each of the three sets of series circuits is electrically connected to a load or a power supply via inductors L3 to L5.

The DC/DC converter 1 performs a first conversion operation of converting a primary-side input voltage into a secondary-side output voltage, and a second conversion operation of converting a secondary-side input voltage into a primary-side output voltage. , is possible. The input and output voltages on the primary side are the voltages between the first ends 11,12. The input and output voltages on the secondary side are the voltages across the second ends 13,14. Hereinafter, the input voltage and the output voltage on the primary side are collectively referred to as the primary side voltage, and the input voltage and the output voltage on the secondary side are collectively referred to as the secondary side voltage. In the following description, unless otherwise specified, the first conversion operation is the focus of the first conversion operation and the second conversion operation. Appropriately applicable.

The detection circuit 4 detects the voltage between the first terminals 11 and 12 of the DC/DC converter 1 as the primary side voltage. Also, the detection circuit 4 detects the voltage between the second terminals 13 and 14 of the DC/DC converter 1 as the secondary side voltage. The detection circuit 4 includes, for example, a first resistive voltage dividing circuit connected across the capacitor C3, a second resistive voltage dividing circuit connected across the capacitor C4, a reference voltage source, a first a comparator that compares the voltage detected by the two-resistor voltage divider with the voltage of the reference voltage source.

Furthermore, the detection circuit 4 detects the current flowing through the first winding N1 as the primary side current. Further, the detection circuit 4 detects the current flowing through the second winding N2 as the secondary side current. The detection circuit 4 includes, for example, a current transformer or a Rogowski coil.

Furthermore, the detection circuit 4 calculates the primary power based on the primary voltage and the primary current. Primary power is power that is input to or output from the first ends 11 and 12 . The detection circuit 4 also calculates the secondary power based on the secondary voltage and the secondary current. Secondary power is power that is input to or output from the second ends 13 and 14 .

A control circuit 2 controls the operation of the DC/DC converter 1 . More specifically, the control circuit 2 controls each switching element of the switching elements S1-S16. The control circuit 2 is configured to apply a control voltage (gate voltage) to each switching element. The control circuit 2 has, for example, a drive circuit that applies a control voltage to each switching element, and a control section that controls the drive circuit. The control voltage is the voltage applied between the control terminal and the second main terminal of the switching element. The control voltage, for example, alternates in voltage level between a voltage value (e.g., 10 V) higher than the threshold voltage (gate threshold voltage) of the switching element and a voltage value (e.g., 0 V) lower than the threshold voltage. voltage.

An execution subject of the control circuit 2 includes a computer system. A computer system has one or more computers. A computer system is mainly composed of a processor and a memory as hardware. A processor executes a program recorded in the memory of the computer system, thereby realizing the function of the control circuit 2 in the present disclosure as an execution entity. The program may be recorded in advance in the memory of the computer system, may be provided through an electric communication line, or may be stored in a non-temporary storage medium such as a computer system-readable memory card, optical disk, or hard disk drive (magnetic disk). may be recorded on a physical recording medium and provided. A processor in a computer system consists of one or more electronic circuits including semiconductor integrated circuits (ICs) or large scale integrated circuits (LSIs). A plurality of electronic circuits may be integrated into one chip, or may be distributed over a plurality of chips. A plurality of chips may be integrated in one device, or may be distributed in a plurality of devices.

(2) Synchronous rectification control in high-frequency switching Next, synchronous rectification control by the control circuit 2 will be described with reference to FIG. As described above, synchronous rectification control is control that turns on and off both the first switching elements Q1-Q4 and the second switching elements Q5-Q8.

The control circuit 2 can operate the DC/DC converter 1 at least in a full bridge control mode, a voltage doubler control mode, and a secondary side phase shift control mode. Synchronous rectification control can be realized in each mode. In this embodiment, only the full bridge control mode will be described, and the voltage doubler control mode and the secondary side phase shift control mode will be described in the second and third embodiments.

In FIG. 2, the switching frequency of each switching element Q1-Q8 is equal to or higher than the resonance frequency of the DC/DC converter 1. In FIG. Switching with such a switching frequency is referred to as high frequency switching in this disclosure.

In FIG. 2, the primary side current It1 is the current that flows through the first winding N1. The secondary current It2 is a current that flows through the second winding N2. A detection circuit 4 can detect the primary side current It1 and the secondary side current It2. Due to the existence of the resonant circuit RC1 consisting of the first capacitor C1, the first inductor L1, the second inductor L2 and the second capacitor C2, a phase difference occurs between the primary side current It1 and the secondary side current It2.

In addition, FIG. 2 shows temporal changes in control voltages (gate voltages) applied to the switching elements Q1 to Q8. The control voltage repeats the same waveform with one cycle from time t1 to time t5. Each switching element Q1-Q8 is turned on when a high-level control voltage is applied, and turned off when a low-level control voltage is applied. The control voltage applied to the switching elements Q1, Q4 is common. The control voltage applied to the switching elements Q2, Q3 is common. The control voltage applied to switching elements Q5 and Q8 is common. The control voltage applied to switching elements Q6 and Q7 is common.

The control circuit 2 alternately turns on the set of switching elements Q1, Q4 and the set of switching elements Q2, Q3. A dead time td exists between when one of the set of switching elements Q1 and Q4 and the set of switching elements Q2 and Q3 is switched from on to off until the other is switched from off to on.

The control circuit 2 repeats control in the first to fourth periods. The first period is a period in which the switching elements Q1 and Q4 are turned off and the switching elements Q2 and Q3 are turned on. The second period is a period in which the switching elements Q1 to Q4 are turned off. The third period is a period in which the switching elements Q1 and Q4 are turned on and the switching elements Q2 and Q3 are turned off. A fourth period is a period in which the switching elements Q1 to Q4 are turned off.

FIG. 3 shows an example of current paths when the control circuit 2 controls the DC/DC converter 1 in full bridge control mode. In the first period, first, current flows through the path indicated by the dashed arrow in FIG. That is, on the primary side, current flows through the path of first terminal 11-switching element Q3-first winding N1-first inductor L1-first capacitor C1-switching element Q2-first terminal 12. FIG. On the secondary side, a current flows through the path of second terminal 14-switching element S6-second capacitor C2-second inductor L2-second winding N2-switching element S7-second terminal 13. FIG. The current flowing through the first winding N1 crosses zero in the middle of the first period, and the direction of the current flowing through the first winding N1 reverses.

In the first period, when the switching element Q6 is on, a current flows through the switching element Q6 of the switching element S6, and when the switching element Q6 is off, a current flows through the diode D6. Similarly, when the switching element Q7 is on, a current flows through the switching element Q7 of the switching element S7, and when the switching element Q7 is off, a current flows through the diode D7. In this manner, current loss in the diode can be reduced by causing the current to flow through the switching element instead of the diode during at least part of the period in the secondary circuit. The same applies to the second to fourth periods.

As shown in FIG. 2, the switching frequency and on-period length of switching elements Q5 and Q8 are equal to the switching frequency and on-period length of switching elements Q1 and Q4, respectively. The control voltages applied to switching elements Q5, Q8 are waveforms that are out of phase with the control voltages applied to switching elements Q1, Q4. That is, the on/off timings of the switching elements Q5 and Q8 are out of phase with the on/off timings of the switching elements Q1 and Q4.

The switching frequency and on-period length of switching elements Q6, Q7 are equal to the switching frequency and on-period length of switching elements Q2, Q3, respectively. The control voltages applied to switching elements Q6, Q7 are waveforms that are out of phase with respect to the control voltages applied to switching elements Q2, Q3. That is, the on/off timings of the switching elements Q6 and Q7 are out of phase with the on/off timings of the switching elements Q2 and Q3.

Specifically, the switching elements Q6 and Q7 are switched from OFF to ON at a timing (time t4) delayed by the delay time tx from the timing (time t3) at which the switching elements Q1 and Q4 are switched from ON to OFF. Further, the switching elements Q5 and Q8 are switched from OFF to ON at a timing (time t2) delayed by the delay time tx from the timing (time t1) at which the switching elements Q2 and Q3 are switched from ON to OFF.

In FIG. 2 , the switching elements Q5 and Q8 are switched from off to on at time t2, and after the switching elements Q5 and Q8 are switched from on to off between time t3 and time t4, when the dead time td elapses, , the switching elements Q6, Q7 are switched from off to on. After that, the switching elements Q5 and Q8 are switched from off to on after the dead time td has passed after the switching elements Q6 and Q7 are switched from on to off between the time points t1 and t2.

The control circuit 2 determines the delay time tx based on predetermined parameters. The predetermined parameters are primary voltage, primary current and primary power at first terminals 11, 12 and secondary voltage, secondary current and secondary power at second terminals 13, 14. It is preferable to include at least one of Also, the predetermined parameters preferably further include the switching frequencies of the first switching elements Q1-Q4.

As an example, the control circuit 2 may increase the delay time tx as the primary side power detected by the detection circuit 4 increases. Also, the correlation between the primary side power and the delay time tx may change according to the primary side voltage. As an example, the control circuit 2 stores, as a data table, the correlation between the predetermined parameters including the primary side power and the delay time tx. good.

Further, the control circuit 2 converts the input voltage on the secondary side to The delay time tx may be different between when the second conversion operation is performed to convert the voltage to the output voltage of . That is, the control circuit 2 may refer to different data tables depending on whether the DC/DC converter 1 is performing the first conversion operation or the second conversion operation.

[Table 1] is an example of a data table for obtaining the delay time tx during the first conversion operation (when the storage battery B1 is discharging). The values in the first column are the magnitudes of the secondary power and are normalized to values from 0 to 1. The values in the second to fourth columns represent the delay time tx and are normalized to values between 0 and 1. When the value of the secondary side voltage is given, which of the voltage conditions 1 to 3 applies is selected according to the magnitude of the secondary side voltage, and the delay time tx is set together with the value of the secondary side power. It is determined.

As an example, the delay time tx (each value in the data table) may be determined so as to satisfy the following first and second conditions. The first condition is that the timing (time t4) at which the switching elements Q6 and Q7 switch from off to on coincides with the timing at which the secondary current It2 changes from negative to zero. The second condition is that the timing (time t2) at which the switching elements Q5 and Q8 switch from off to on coincides with the timing at which the secondary current It2 changes from positive to zero. A delay time tx that satisfies the first condition and the second condition may be calculated in advance for each value of the predetermined parameter, and the delay time tx may be stored as a data table. Synchronous rectification control that satisfies the first condition and the second condition is hereinafter referred to as "first synchronous rectification control".

If the delay time tx is determined to satisfy the first and second conditions, as shown in FIG. 2, the secondary current It2 during the ON period of the switching elements Q5 and Q8 becomes negative, and the switching element Q6 becomes negative. , Q7 are on, the secondary current It2 is more likely to be positive. Therefore, it is possible to reduce the possibility of reverse current flowing to the secondary side in synchronous rectification control.

However, the capacitance of the first capacitor C1 and the second capacitor C2 and the inductance of the first inductor L1 and the second inductor L2 of the DC/DC converter 1 may vary from individual to individual. As a result, the timing at which the secondary current It2 becomes 0 may vary among the plurality of DC/DC converters 1 .

Therefore, it is preferable that the control circuit 2 determines the delay time so that the second switching elements Q5 to Q8 are switched from off to on at a timing later than the timing at which the polarity of the secondary current It2 is switched. Such control is hereinafter referred to as "second synchronous rectification control". Here, the “secondary current It2” described as “the timing at which the positive and negative of the secondary current It2 are switched” includes the switching frequency of each switching element, the capacitance of the first capacitor C1 and the second capacitor C2, and the It is a value determined based on design values such as the inductance of the inductor L1 and the second inductor L2. The "secondary current It2" referred to here does not necessarily have to match the actually detected secondary current It2.

When executing the second synchronous rectification control, even if the timing at which the secondary current It2 becomes 0 varies, it is possible to reduce the possibility that the current will flow in the opposite direction to the secondary side.

An example of the second synchronous rectification control is shown in FIG. In FIG. 4, the primary side current It1, the secondary side current It2, and the control voltages of the switching elements Q1 to Q4 are the same as in FIG. In FIG. 4, the switching frequency of each switching element Q1-Q8 is equal to or higher than the resonance frequency of the DC/DC converter 1. In FIG.

In FIG. 4, the positive/negative of the secondary current It2 switches at time t2. After this, at time t21, the switching elements Q5 and Q8 are switched from off to on. After that, at time t22 before time t3, the switching elements Q5 and Q8 are switched from on to off. The ON periods of the switching elements Q5 and Q8 are shorter than the ON periods of the switching elements Q1 and Q4.

At time t4, the secondary current It2 switches between positive and negative. After this, at time t41, the switching elements Q6 and Q7 are switched from off to on. After that, at time t42 before time t5 (t1), the switching elements Q6 and Q7 are switched from on to off. The ON periods of switching elements Q6 and Q7 are shorter than the ON periods of switching elements Q2 and Q3.

Dead times td1 and td2 of switching elements Q5-Q8 are longer than dead time td of switching elements Q1-Q4.

In the second synchronous rectification control, the switching elements Q5 to Q8 are switched from off to on with a delay from the timing of switching from off to on in the first synchronous rectification control. The delay length (margin tm) is, for example, a fixed value shorter than half the switching period. The margin tm is stored in advance in the memory of the control circuit 2, for example. In the second synchronous rectification control, the delay time is the sum of the delay time tx and the margin tm, and the second switching elements Q1 to Q4 are switched from on to off at a second timing delayed by the delay time from the first timing. It can be said that this is control for switching Q5 to Q8 from off to on.

By switching the ON/OFF control of the switching elements Q1 to Q4 and the ON/OFF control of the switching elements Q5 to Q8, the second conversion operation for converting the input voltage on the secondary side to the output voltage on the primary side can also be performed in the first conversion operation. and second synchronous rectification control are applicable.

(3) Comparative Example FIG. 5 shows a timing chart of a control method according to a comparative example. The control method according to the comparative example differs from the embodiment in the on/off timings of the switching elements Q5 to Q8. In FIG. 5, the switching elements Q6 and Q7 are switched from off to on at the timing (time t3) when the switching elements Q1 and Q4 are switched from on to off. Moreover, the switching elements Q5 and Q8 are switched from off to on at the timing (time t1) at which the switching elements Q2 and Q3 are switched from on to off.

In FIG. 5, the switching elements Q6, Q7 are on from time t3 to time t43 between time t4 and time t5 (t1). The direction of the secondary current It2 during the period from time t3 to time t4 is opposite to the direction of the secondary current It2 during the period from time t4 to time t43. That is, the secondary current It2 in the opposite direction flows through the second winding N2. On the other hand, in FIGS. 2 and 4 corresponding to the embodiment, by delaying the on/off timing by at least the delay time tx, the possibility that the secondary current It2 flows in the opposite direction can be reduced.

(4) Synchronous Rectification Control in Low-Frequency Switching In the explanation so far, the synchronous rectification control has been explained on the condition that the switching frequency of each switching element Q1 to Q8 is equal to or higher than the resonance frequency of the DC/DC converter 1. Synchronous rectification control under the condition that the switching frequencies of the switching elements Q1 to Q8 are lower than the resonance frequency of the DC/DC converter 1 will be described below with reference to FIG. Switching with such a switching frequency is referred to as low frequency switching in this disclosure.

As shown in FIG. 6, the length of the period from time t1 to time t3 is half the switching period. After the secondary current It2 changes from 0 to a negative value, the length of the period (time t1 to time t24) until the secondary current It2 becomes 0 is shorter than half the switching period. .

When the switching frequency of each of the switching elements Q1 to Q8 is equal to or higher than the resonance frequency of the DC/DC converter 1 (see FIGS. 2 and 4), the timing at which the secondary current It2 changes from a negative value to 0 is the switching frequency determined by On the other hand, when the switching frequency is lower than the resonance frequency (see FIG. 6), the timing at which the secondary current It2 changes from a negative value to 0 is not the switching frequency but the resonance frequency of the DC/DC converter 1. determined by Therefore, when the switching frequency is lower than the resonance frequency, the control circuit 2 determines the timing of switching the second switching element from on to off based on the resonance frequency. Specifically, the control circuit 2 obtains the timing (time t24) at which the secondary current It2 becomes 0 based on the resonance frequency, and switches the switching elements Q6 and Q7 from on to off at this timing.

As shown in FIG. 6, the length of the period from time t3 to time t5 (t1) is half the switching period. After the secondary current It2 changes from 0 to a positive value, the length of the period until the secondary current It2 becomes 0 (time t3 to time t44) is shorter than half the switching period. .

When the switching frequency of each of the switching elements Q1 to Q8 is equal to or higher than the resonance frequency of the DC/DC converter 1 (see FIGS. 2 and 4), the timing at which the secondary current It2 changes from a positive value to 0 is the switching frequency determined by On the other hand, when the switching frequency is lower than the resonance frequency (see FIG. 6), the timing at which the secondary current It2 changes from a positive value to 0 is not the switching frequency but the resonance frequency of the DC/DC converter 1. determined by Therefore, when the switching frequency is lower than the resonance frequency, the control circuit 2 determines the timing of switching the second switching element from on to off based on the resonance frequency. Specifically, the control circuit 2 obtains the timing (time t44) at which the secondary current It2 becomes 0 based on the resonance frequency, and switches the switching elements Q5 and Q8 from on to off at this timing.

As described above, the DC/DC converter 1 includes the first capacitor C1 electrically connected to the first winding N1 and the second capacitor C2 electrically connected to the second winding N2. At least one of them (in this embodiment, both). The control circuit 2 includes at least one of the first capacitor C1 and the second capacitor C2, a first leakage inductance (first inductor L1) on the side of the first winding N1, and a second leakage inductance on the side of the second winding N2. (second inductor L2), and when the resonance frequency of the resonance circuit RC1 is lower than the switching frequencies of the first switching elements Q1 to Q4 and the second switching elements Q5 to Q8, the second switching elements Q5 to Q8 The timing for switching from on to off is determined based on the resonance frequency.

If the resonance frequency is lower than the switching frequency, it is not essential to determine the timing of switching the second switching elements Q5-Q8 from on to off based on the resonance frequency. Even when the resonance frequency is lower than the switching frequency, the same control as when the resonance frequency is equal to or higher than the switching frequency may be performed.

(5) Diode Rectification Control The control circuit 2 basically performs the above-described synchronous rectification control. However, the control circuit 2 may perform diode rectification control when the load is light. Diode rectification control is control to turn off the first switching elements Q1 to Q4 while keeping the second switching elements Q5 to Q8 off. In diode rectification control, on the secondary side, current flows through the second diodes D5-D8 instead of the second switching elements Q5-Q8.

The control circuit 2 may determine the timing of switching between the diode rectification control and the synchronous rectification control based on the predetermined parameters described above. Here, it is assumed that the control circuit 2 determines the switching timing based on the output power (secondary side power) included in a predetermined parameter. The output power is a value of 0 or greater.

For example, the control circuit 2 performs synchronous rectification control when the output power of the DC/DC converter 1 is greater than a threshold, and performs diode rectification control when the output power is equal to or less than the threshold.

A predetermined parameter when the control circuit 2 switches from diode rectification control to synchronous rectification control and a predetermined parameter when the control circuit 2 switches from synchronous rectification control to diode rectification control may have hysteresis. . That is, the first threshold when the control circuit 2 switches from diode rectification control to synchronous rectification control and the second threshold when the control circuit 2 switches from synchronous rectification control to diode rectification control may be different. As a specific example, the first threshold is greater than the second threshold. When performing diode rectification control, the control circuit 2 switches to synchronous rectification control when the output power becomes greater than the first threshold. Also, when the synchronous rectification control is performed, the control circuit 2 switches to the diode rectification control when the output power becomes smaller than the second threshold value.

(Embodiment 2)
In the second embodiment, a case where the control circuit 2 operates the DC/DC converter 1 in the double voltage control mode will be described. The configuration of the power conversion system 10 is the same as that of the first embodiment. It is assumed that the switching frequency of each switching element Q1-Q8 is equal to or higher than the resonance frequency of the DC/DC converter 1. FIG.

When the DC/DC converter 1 performs the first conversion operation, the control circuit 2 turns off the switching element Q7, turns on the switching element Q8, and switches the switching elements Q1 to Q6 in the voltage doubler control mode. FIG. 7 is an equivalent circuit diagram of the DC/DC converter 1 when the control circuit 2 controls the DC/DC converter 1 in the voltage doubler control mode. The voltage gain when the control circuit 2 controls the DC/DC converter 1 in the full-bridge control mode is approximately twice the voltage gain when the DC/DC converter 1 is controlled in the double voltage control mode.

FIG. 8 shows an example of temporal changes in the primary side current It1, the secondary side current It2, and the control voltage applied to each of the switching elements Q1 to Q8 in the voltage doubler control mode. The control shown in FIG. 8 is the second synchronous rectification control. That is, the delay time is the sum of tx and margin tm.

The switching element Q6 is switched from OFF to ON at a timing (time t41) delayed by the delay time (tx+tm) from the timing (time t3) at which the switching elements Q1 and Q4 are switched from ON to OFF.

Further, the switching element Q5 is switched from OFF to ON at a timing (time t21) delayed by the delay time (tx+tm) from the timing (time t1) at which the switching elements Q2 and Q3 are switched from ON to OFF.

Further, at time t2, the secondary current It2 switches between positive and negative. After this, at time t21, the switching element Q5 switches from off to on. Thereafter, at time t22, which is earlier than time t3, switching element Q5 switches from on to off. The ON period of the switching element Q5 is shorter than the ON periods of the switching elements Q1 and Q4.

At time t4, the secondary current It2 switches between positive and negative. After this, at time t41, the switching element Q6 switches from off to on. After that, at time t42, which is earlier than time t5 (t1), switching element Q6 switches from on to off. The ON period of the switching element Q6 is shorter than the ON periods of the switching elements Q2 and Q3.

Even in the voltage doubler control mode, the current loss in the diode can be reduced by causing the current to flow through the switching element instead of the diode for at least part of the period in the secondary circuit. Moreover, by providing the delay time, it is possible to reduce the possibility that the current flows in the opposite direction to the secondary side.

(Embodiment 3)
Embodiment 3 describes a case where the control circuit 2 causes the DC/DC converter 1 to operate in the secondary side phase shift control mode. The configuration of the power conversion system 10 is the same as that of the first embodiment. It is assumed that the switching frequency of each switching element Q1-Q8 is lower than the resonance frequency of the DC/DC converter 1. FIG.

The secondary side phase shift control is to change the control voltage given to the switching elements Q6 and Q8 out of the four switching elements Q5 to Q8 that make up the secondary side full bridge circuit to the control voltage given to the switching elements Q1 to Q4. In this method, a phase difference is provided. More specifically, a phase difference is provided between the control voltage applied to the switching elements Q1 and Q4 and the control voltage applied to the switching element Q8, and the control voltage applied to the switching elements Q2 and Q3 and the control voltage applied to the switching element Q6 and are provided with a phase difference. Further, in the secondary side phase shift control, the OFF periods of the switching elements Q5 and Q7 are set longer than the OFF periods of the switching elements Q6 and Q8.

FIG. 9 shows an example of temporal changes in the primary side current It1, the secondary side current It2, and the control voltage applied to each of the switching elements Q1 to Q8 in the secondary side phase shift control mode. The control shown in FIG. 9 is the second synchronous rectification control. That is, the delay time is the sum of tx and margin tm. One cycle of the control voltage is from time t1 to t9.

The switching element Q7 is switched from OFF to ON at a timing (time t61) delayed by the delay time (tx+tm) from the timing (time t5) at which the switching elements Q1 and Q4 are switched from ON to OFF.

Further, the switching element Q5 is switched from OFF to ON at a timing (time t21) delayed by the delay time (tx+tm) from the timing (time t1) at which the switching elements Q2 and Q3 are switched from ON to OFF.

Further, at time t2, the secondary current It2 switches between positive and negative. After this, at time t21, the switching element Q5 switches from off to on. After that, at time t22 before time t3, switching element Q5 is switched from on to off, and at time t4 between time t1 and time t5, switching element Q8 is switched from off to on.

At time t6, the secondary current It2 switches between positive and negative. After this, at time t61, the switching element Q7 switches from off to on. Then, at time t8 between time t5 and time t1, switching element Q6 switches from off to on.

Even in the secondary side phase shift control mode, the current loss in the diode can be reduced by causing the current to flow through the switching element instead of the diode at least part of the time in the secondary side circuit. Moreover, by providing the delay time, it is possible to reduce the possibility that the current flows in the opposite direction to the secondary side.

(Modification)
Modifications of the present disclosure are listed below. The following modifications are applicable to the first to third embodiments, respectively. The following modified examples may be implemented in combination as appropriate.

The means for determining the delay time tx is not limited to referring to the data table, and the delay time tx may be determined by a predetermined formula.

In the first embodiment, the control circuit 2 performs digital processing to change the delay time tx discontinuously with respect to changes in a predetermined parameter. On the other hand, the control circuit 2 may be provided with an analog circuit for inputting a predetermined parameter and outputting the delay time tx, thereby continuously changing the delay time tx with respect to changes in the predetermined parameter.

The first inductor L1 and the second inductor L2 are not limited to being composed only of the leakage inductance of the isolation transformer Tr1. That is, an external inductor may be electrically connected to at least one of the primary side and the secondary side of the isolation transformer Tr1.

Diodes D1-D8 are not limited to parasitic diodes. That is, the switching element and the diode may be provided separately.

The DC/DC converter 1 may have either one of the first capacitor C1 and the second capacitor C2, or neither.

In Embodiment 1, the plurality of first switching elements Q1-Q4 and the plurality of second switching elements Q5-Q8 are connected to form a full bridge, but the connection mode of each switching element is limited to this. not. For example, each switching element may be connected to form a half-bridge.

Control in the power conversion system 10 of the present disclosure can be embodied in a control method, (computer) program, or non-temporary recording medium recording the program.

A control method according to one aspect is a control method for controlling the operation of the DC/DC converter 1 . The DC/DC converter 1 includes a pair of first ends 11 and 12, a first winding N1, one or more first switching elements Q1 to Q4, one or more first diodes D1 to D4, and a pair of , a second winding N2, one or more second switching elements Q5-Q8, and one or more second diodes D5-D8. The first switching elements Q1-Q4 are electrically connected between the first winding N1 and the pair of first ends 11,12. One or more first diodes D1-D4 are connected in parallel with one or more first switching elements Q1-Q4 in one-to-one correspondence. The second winding N2 constitutes an isolation transformer Tr1 together with the first winding N1. The second switching elements Q5-Q8 are electrically connected between the second winding N2 and the pair of second ends 13,14. One or more second diodes D5-D8 are connected in parallel with one or more second switching elements Q5-Q8 in one-to-one correspondence. The control method includes performing synchronous rectification control to turn on and off both the first switching elements Q1-Q4 and the second switching elements Q5-Q8. In the synchronous rectification control, the second switching elements Q5-Q8 are switched from off to on at a second timing delayed by the delay time tx from the first timing of switching the first switching elements Q1-Q4 from on to off.

A program according to one aspect is a program for causing one or more processors to execute the above control method. The program may be recorded on a computer-readable non-transitory recording medium.

A power conversion system 10 according to the present disclosure includes a computer system as a configuration of the control circuit 2 . A computer system is mainly composed of a processor and a memory as hardware. At least part of the function of the control circuit 2 in the present disclosure is realized by the processor executing a program recorded in the memory of the computer system. The program may be recorded in advance in the memory of the computer system, may be provided through an electric communication line, or may be recorded in a non-temporary recording medium such as a computer system-readable memory card, optical disk, or hard disk drive. may be provided. A processor in a computer system consists of one or more electronic circuits, including semiconductor integrated circuits (ICs) or large scale integrated circuits (LSIs). The integrated circuit such as IC or LSI referred to here is called differently depending on the degree of integration, and includes integrated circuits called system LSI, VLSI (Very Large Scale Integration), or ULSI (Ultra Large Scale Integration). In addition, a field-programmable gate array (FPGA) that is programmed after the LSI is manufactured, or a logic device capable of reconfiguring the bonding relationship inside the LSI or reconfiguring the circuit partitions inside the LSI may also be adopted as the processor. can be done. A plurality of electronic circuits may be integrated into one chip, or may be distributed over a plurality of chips. A plurality of chips may be integrated in one device, or may be distributed in a plurality of devices. A computer system, as used herein, includes a microcontroller having one or more processors and one or more memories. Accordingly, the microcontroller also consists of one or more electronic circuits including semiconductor integrated circuits or large scale integrated circuits.

In addition, it is not an essential configuration of the power conversion system 10 that a plurality of functions in the power conversion system 10 are integrated into one housing, and the components of the power conversion system 10 are distributed over a plurality of housings. may be provided. Furthermore, at least part of the functions of the power conversion system 10 may be realized by a cloud (cloud computing) or the like.

Conversely, in the embodiment, at least part of the functions of the power conversion system 10 distributed over multiple housings may be integrated into one housing. For example, some functions of the power conversion system 10 distributed to the DC/DC converter 1 and the inverter 5 may be integrated into one housing.

In the comparison of two values in this disclosure, "greater than" refers to when one of the two values is greater than the other. However, the term "greater than" as used herein may be synonymous with "greater than or equal to" including both cases in which two values are equal and cases in which one of the two values exceeds the other. In other words, whether or not two values are equal can be arbitrarily changed depending on the setting of the reference value, etc., so there is no technical difference between "greater than" and "greater than or equal to". Similarly, "less than" may be synonymous with "less than".

(summary)
The following aspects are disclosed from the embodiments and the like described above.

A power converter (3) according to a first aspect includes a DC/DC converter (1) and a control circuit (2) that controls the operation of the DC/DC converter (1). A DC/DC converter (1) includes a pair of first ends (11, 12), a first winding (N1), one or more first switching elements (Q1 to Q4), and one or more first one diode (D1-D4), a pair of second ends (13, 14), a second winding (N2), one or more second switching elements (Q5-Q8), one or more second 2 diodes (D5-D8). The first switching elements (Q1-Q4) are electrically connected between the first winding (N1) and the pair of first ends (11, 12). One or more first diodes (D1-D4) are connected in parallel with one or more first switching elements (Q1-Q4) in one-to-one correspondence. The second winding (N2) constitutes an isolation transformer (Tr1) together with the first winding (N1). The second switching elements (Q5-Q8) are electrically connected between the second winding (N2) and the pair of second ends (13, 14). One or more second diodes (D5-D8) are connected in parallel to one or more second switching elements (Q5-Q8) in one-to-one correspondence. The control circuit (2) performs synchronous rectification control to turn on and off both the first switching elements (Q1-Q4) and the second switching elements (Q5-Q8). In synchronous rectification control, the control circuit (2) controls the second switching element (Q5 ~Q8) from off to on.

According to the above configuration, compared to the case where the first timing and the second timing match, it is possible to reduce the possibility of a reverse current flowing through the second winding (N2). That is, it is possible to reduce the possibility that the DC/DC converter (1) will operate abnormally.

Moreover, in the power conversion device (3) according to the second aspect, in the first aspect, the control circuit (2) determines the delay time (tx) based on a predetermined parameter. The predetermined parameters are the primary voltage, primary current and primary power at the pair of first ends (11, 12) and the secondary voltage, 2 At least one of secondary current and secondary power.

According to the above configuration, switching according to a predetermined parameter can be realized.

Further, in the power conversion device (3) according to the third aspect, in the second aspect, the predetermined parameter further includes switching frequencies of the first switching elements (Q1 to Q4).

According to the above configuration, the switching timing is determined according to the switching frequency, so that the DC/DC converter (1) can obtain a gain larger than the winding ratio of the isolation transformer (Tr1).

Further, in the power conversion device (3) according to the fourth aspect, in the second or third aspect, the control circuit (2) switches the second switching element at a timing later than the timing at which the positive/negative of the secondary current is switched. Determine the delay time (tx+tm) to switch (Q5-Q8) from off to on.

According to the above configuration, even if there are variations in the resonance frequency of the DC/DC converter (1), it is possible to reduce the possibility that the DC/DC converter (1) will operate abnormally.

Further, in the power conversion device (3) according to the fifth aspect, in any one of the second to fourth aspects, the control circuit (2) sets the delay time (tx) with respect to the change of the predetermined parameter. change continuously.

According to the above configuration, highly accurate synchronous rectification control can be realized.

Further, in the power conversion device (3) according to the sixth aspect, in any one of the second to fourth aspects, the control circuit (2) sets the delay time (tx) with respect to the change of the predetermined parameter. change discontinuously.

According to the above configuration, the delay time (tx) can be determined using a microcontroller or the like.

Further, in the power converter (3) according to the seventh aspect, in any one of the second to sixth aspects, the DC/DC converter (1) is electrically connected to the first winding (N1) and a second capacitor (C2) electrically connected to the second winding (N2). The control circuit (2) includes at least one of a first capacitor (C1) and a second capacitor (C2), a first leakage inductance (first inductor L1) on the side of the first winding (N1), and a second winding (N1). The resonance frequency of the resonance circuit (RC1) including the second leakage inductance (second inductor L2) on the line (N2) side is the same as that of the first switching elements (Q1 to Q4) and the second switching elements (Q5 to Q8) When the frequency is lower than the switching frequency, the timing for switching the second switching elements (Q5 to Q8) from on to off is determined based on the resonance frequency.

According to the above configuration, synchronous rectification control can be realized even when the resonance frequency is lower than the switching frequency.

Further, in the power conversion device (3) according to the eighth aspect, in any one of the second to seventh aspects, the control circuit (2) keeps the second switching elements (Q5 to Q8) off. The timing of switching between diode rectification control for turning on and off the first switching elements (Q1 to Q4) and synchronous rectification control is determined based on a predetermined parameter.

According to the above configuration, the operation of the DC/DC converter (1) can be stabilized by using diode rectification control in addition to synchronous rectification control.

Further, in the power conversion device (3) according to the ninth aspect, in the eighth aspect, the control circuit (2) has a predetermined parameter when switching from diode rectification control to synchronous rectification control, and the control circuit (2) A hysteresis is provided to a predetermined parameter when switching from synchronous rectification control to diode rectification control.

According to the above configuration, it is possible to reduce the possibility of occurrence of a chattering phenomenon in which synchronous rectification control and diode rectification control are frequently switched.

Configurations other than the first mode are not essential configurations for the power converter (3), and can be omitted as appropriate.

A power conversion system (10) according to a tenth aspect includes a power converter (3) according to any one of the first to ninth aspects, and an inverter (5). The inverter (5) is electrically connected to a pair of first ends (11, 12) or a pair of second ends (13, 14) of the DC/DC converter (1).

According to the above configuration, it is possible to reduce the possibility that the DC/DC converter (1) will operate abnormally.

A control method according to an eleventh aspect is a control method for controlling the operation of a DC/DC converter (1). A DC/DC converter (1) includes a pair of first ends (11, 12), a first winding (N1), one or more first switching elements (Q1 to Q4), and one or more first one diode (D1-D4), a pair of second ends (13, 14), a second winding (N2), one or more second switching elements (Q5-Q8), one or more second 2 diodes (D5-D8). The first switching elements (Q1-Q4) are electrically connected between the first winding (N1) and the pair of first ends (11, 12). One or more first diodes (D1-D4) are connected in parallel with one or more first switching elements (Q1-Q4) in one-to-one correspondence. The second winding (N2) forms an isolation transformer (Tr1) together with the first winding (N1). The second switching elements (Q5-Q8) are electrically connected between the second winding (N2) and the pair of second ends (13, 14). One or more second diodes (D5-D8) are connected in parallel to one or more second switching elements (Q5-Q8) in one-to-one correspondence. The control method includes performing synchronous rectification control to turn on and off both the first switching elements (Q1-Q4) and the second switching elements (Q5-Q8). In synchronous rectification control, the second switching elements (Q5 to Q8) are switched from off to on at a second timing delayed by the delay time (tx) from the first timing of switching the first switching elements (Q1 to Q4) from on to off. switch to

According to the above configuration, it is possible to reduce the possibility that the DC/DC converter (1) will operate abnormally.

A program according to a twelfth aspect is a program for causing one or more processors to execute the control method according to the eleventh aspect.

According to the above configuration, it is possible to reduce the possibility that the DC/DC converter (1) will operate abnormally.

Various configurations (including modifications) of the power conversion system (10) according to the embodiment, not limited to the above aspects, are embodied in a non-temporary recording medium recording a control method, (computer) program, or program It is possible.

1 DC/DC converter 2 control circuit 3 power conversion device 5 inverter 10 power conversion system 11, 12 first terminals 13, 14 second terminals C1 first capacitor C2 second capacitors D1 to D4 first diodes D5 to D8 second diodes L1 first inductor (first leakage inductance)
L2 second inductor (second leakage inductance)
N1 First winding N2 Second winding Q1-Q4 First switching elements Q5-Q8 Second switching element RC1 Resonant circuit Tr1 Isolation transformer tx Delay time

Claims (12)

a DC/DC converter;
a control circuit that controls the operation of the DC/DC converter,
The DC/DC converter is
a pair of first ends;
a first winding;
one or more first switching elements electrically connected between the first winding and the pair of first ends;
one or more first diodes connected in parallel in one-to-one correspondence with one or more of the first switching elements;
a pair of second ends;
a second winding that forms an isolation transformer together with the first winding;
one or more second switching elements electrically connected between the second winding and the pair of second ends;
one or more second diodes connected in parallel in one-to-one correspondence with one or more of the second switching elements;
The control circuit performs synchronous rectification control to turn on and off both the first switching element and the second switching element,
In the synchronous rectification control, the control circuit switches the second switching element from off to on at a second timing delayed by a delay time from a first timing for switching the first switching element from on to off.
Power converter. The control circuit determines the delay time based on a predetermined parameter,
The predetermined parameters are primary side voltage, primary side current and primary side power at the pair of first terminals, and secondary side voltage, secondary side current and secondary side at the pair of second terminals. including at least one of electrical power;
The power converter according to claim 1. the predetermined parameter further includes a switching frequency of the first switching element;
The power converter according to claim 2. The control circuit determines the delay time so as to switch the second switching element from off to on at a timing later than the timing at which the positive and negative of the secondary current is switched.
The power converter according to claim 2 or 3. The control circuit continuously changes the delay time with respect to changes in the predetermined parameter.
The power converter according to any one of claims 2 to 4. the control circuit discontinuously changes the delay time with respect to changes in the predetermined parameter;
The power converter according to any one of claims 2 to 4. the DC/DC converter further includes at least one of a first capacitor electrically connected to the first winding and a second capacitor electrically connected to the second winding;
The control circuit is a resonance circuit including at least one of the first capacitor and the second capacitor, a first leakage inductance on the first winding side, and a second leakage inductance on the second winding side. is lower than the switching frequencies of the first switching element and the second switching element, the timing for switching the second switching element from on to off is determined based on the resonance frequency.
The power converter according to any one of claims 2-6. The control circuit determines switching timing between diode rectification control in which the second switching element is kept off and the first switching element is turned on and off, and the synchronous rectification control, based on the predetermined parameter.
The power converter according to any one of claims 2 to 7. The predetermined parameter when the control circuit switches from the diode rectification control to the synchronous rectification control and the predetermined parameter when the control circuit switches from the synchronous rectification control to the diode rectification control have hysteresis. seta,
The power converter according to claim 8. A power conversion device according to any one of claims 1 to 9,
an inverter electrically connected to the pair of first ends or the pair of second ends of the DC/DC converter;
power conversion system. A control method for controlling the operation of a DC/DC converter, comprising:
The DC/DC converter is
a pair of first ends;
a first winding;
one or more first switching elements electrically connected between the first winding and the pair of first ends;
one or more first diodes connected in parallel in one-to-one correspondence with one or more of the first switching elements;
a pair of second ends;
a second winding that forms an isolation transformer together with the first winding;
one or more second switching elements electrically connected between the second winding and the pair of second ends;
one or more second diodes connected in parallel in one-to-one correspondence with one or more of the second switching elements;
The control method includes performing synchronous rectification control to turn on and off both the first switching element and the second switching element,
In the synchronous rectification control, the second switching element is switched from off to on at a second timing delayed by a delay time from the first timing of switching the first switching element from on to off.
control method. for causing one or more processors to execute the control method according to claim 11,
program.

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