WO2024071024A1

WO2024071024A1 - Power conversion device and motor module

Info

Publication number: WO2024071024A1
Application number: PCT/JP2023/034690
Authority: WO
Inventors: 耕太郎片岡
Original assignee: ニデック株式会社
Priority date: 2022-09-30
Filing date: 2023-09-25
Publication date: 2024-04-04

Abstract

One aspect of a power conversion device of the present invention comprises H-bridge circuits corresponding to respective phases of a motor, and an auxiliary circuit corresponding to at least one of the H-bridge circuits, wherein the auxiliary circuit includes: a first rectifying element and a first inductor connected in series between a first connection point and a third connection point; a second rectifying element and a second inductor connected in series between a second connection point and the third connection point; a third rectifying element and a third inductor connected in series between the first connection point and a fourth connection point; a fourth rectifying element and a fourth inductor connected in series between the second connection point and the fourth connection point; a fifth switch connected between a positive electrode of a power source and the third connection point; a fifth rectifying element having a negative electrode terminal connected to the third connection point, and a positive electrode terminal connected to a negative electrode of the power source; a sixth rectifying element having a negative electrode terminal connected to the positive electrode, and a positive electrode terminal connected to the fourth connection point; and a sixth switch connected between the negative electrode and the fourth connection point.

Description

Power conversion device and motor module

The present invention relates to a power conversion device and a motor module.

Patent Document 1 discloses an operation control device that uses two three-phase inverters to operate an induction motor having a three-phase stator winding and six lead-out terminals. This operation control device controls the output voltage phases of both inverters to be in phase when the induction motor is operating at low speed. In addition, when the induction motor is operating at high speed, the operation control device inverts the voltage phase of one inverter by 180 degrees and halves the output frequency of both inverters to invert the phase rotation. With this control, the number of poles of the induction motor is equivalently switched from four to two when switching from low to high speed operation, eliminating torque shortages during high speed operation without increasing the size of the induction motor.

JP 2002-136184 A

In the technology disclosed in Patent Document 1, switching losses occur during switching of the switches in the two inverters, which reduces the driving efficiency of the induction motor.

One aspect of the power conversion device of the present invention comprises an H-bridge circuit corresponding to each phase of a motor having two groups of N-phase terminals (N is an integer of 3 or more), an auxiliary circuit corresponding to at least one of the H-bridge circuits, and a control unit that controls the H-bridge circuit and the auxiliary circuit, the H-bridge circuit comprising a first leg including a first switch connected between a positive electrode of a power source and a first connection point, a second switch connected between a negative electrode of the power source and the first connection point, a third switch connected between the positive electrode and the second connection point, and a fourth switch connected between the negative electrode and the second connection point, the auxiliary circuit comprising a first rectifying element and a first inductor connected in series between the first connection point and the third connection point, and a fourth switch connected in series between the second connection point and the third connection point. a second rectifier element and a second inductor connected in series between the first connection point and the fourth connection point; a third rectifier element and a third inductor connected in series between the second connection point and the fourth connection point; a fourth rectifier element and a fourth inductor connected in series between the second connection point and the fourth connection point; a fifth switch connected between the positive electrode and the third connection point; a fifth rectifier element having a negative terminal connected to the third connection point and a positive terminal connected to the negative electrode; a sixth rectifier element having a negative terminal connected to the positive electrode and a positive terminal connected to the fourth connection point; and a sixth switch connected between the negative electrode and the fourth connection point, where the positive terminal of the first rectifier element and the positive terminal of the second rectifier element are located on the third connection point side, and the negative terminal of the third rectifier element and the negative terminal of the fourth rectifier element are located on the fourth connection point side.

One embodiment of the motor module of the present invention comprises a motor having two N-phase terminal groups (N is an integer equal to or greater than 3) and the power conversion device of the above embodiment.

The above aspect of the present invention makes it possible to reduce the switching loss of each switch included in the H-bridge circuit corresponding to each phase of the motor.

FIG. 1 is a diagram illustrating a schematic configuration of a motor module 1 according to the present embodiment. FIG. 2 is a diagram showing a circuit configuration of an H-bridge circuit BC corresponding to the U-phase and an auxiliary circuit SC corresponding to the H-bridge circuit BC. FIG. 3 is a timing chart showing the on/off timing of the first switch Tr1, the second switch Tr2, and the fifth switch Tr5 when a current flows from the first connection point P1 to the motor 20. FIG. 4 is a diagram showing the state of each switch and the direction of current in a first period T1 in the PWM cycle TP shown in FIG. FIG. 5 is a diagram showing the state of each switch and the direction of current in the second period T2 in the PWM cycle TP shown in FIG. FIG. 6 is a diagram showing the state of each switch and the direction of current in the third period T3 in the PWM cycle TP shown in FIG. FIG. 7 is a diagram showing the state of each switch and the direction of current in a fourth period T4 in the PWM cycle TP shown in FIG. FIG. 8 is a diagram showing the state of each switch and the direction of current in a fifth period T5 in the PWM cycle TP shown in FIG. FIG. 9 is a timing chart showing the on/off timing of the first switch Tr1, the second switch Tr2, and the sixth switch Tr6 when a current flows from the motor 20 to the first connection point P1. FIG. 10 is a diagram showing the state of each switch and the direction of current in a first period T11 in the PWM cycle TP shown in FIG. FIG. 11 is a diagram showing the state of each switch and the direction of current in the second period T12 in the PWM cycle TP shown in FIG. FIG. 12 is a diagram showing the state of each switch and the direction of current in the third period T13 in the PWM cycle TP shown in FIG. FIG. 13 is a diagram showing the state of each switch and the direction of current in a fourth period T14 in the PWM cycle TP shown in FIG. FIG. 14 is a diagram showing the state of each switch and the direction of current in a fifth period T15 in the PWM cycle TP shown in FIG. FIG. 15 is a timing chart showing the on/off timing of the first switch Tr1 to the fourth switch Tr4 and the fifth switch Tr5 when current flows from each of the first connection point P1 and the second connection point P2 toward the motor 20. FIG. 16 is a diagram showing the state of each switch and the direction of current in a first period T21 in the PWM cycle TP shown in FIG. FIG. 17 is a diagram showing the state of each switch and the direction of current in the second period T22 in the PWM cycle TP shown in FIG. FIG. 18 is a diagram showing the state of each switch and the direction of current in the third period T23 in the PWM cycle TP shown in FIG. FIG. 19 is a diagram showing the state of each switch and the direction of current in a fourth period T24 in the PWM cycle TP shown in FIG. FIG. 20 is a diagram showing the state of each switch and the direction of current in a fifth period T25 in the PWM cycle TP shown in FIG. FIG. 21 is a timing chart showing the on/off timing of the first switch Tr1 to the fourth switch Tr4 and the fifth switch Tr5 when a current flows from each of the first connection point P1 and the second connection point P2 toward the motor 20 and the on period of the first switch Tr1 is shorter than the on period of the third switch Tr3 within the PWM period TP. FIG. 22 is a diagram showing the state of each switch and the direction of current in a first period T31 in the PWM cycle TP shown in FIG. FIG. 23 is a diagram showing the state of each switch and the direction of current in a second period T32 in the PWM cycle TP shown in FIG. FIG. 24 is a diagram showing the state of each switch and the direction of current in a third period T33 in the PWM cycle TP shown in FIG. FIG. 25 is a diagram showing the state of each switch and the direction of current in a fourth period T34 in the PWM cycle TP shown in FIG. FIG. 26 is a diagram showing the state of each switch and the direction of current in a fifth period T35 in the PWM cycle TP shown in FIG. FIG. 27 is a timing chart showing the on/off timing of the first switch Tr1 to the fourth switch Tr4 and the fifth switch Tr5 when a current flows from each of the first connection point P1 and the second connection point P2 toward the motor 20, and when, within a PWM period TP, the length of the on period of the first switch Tr1 and the length of the on period of the third switch Tr3 are different and the center of the on period of the first switch Tr1 and the center of the on period of the third switch Tr3 are shifted from each other by a half PWM period. FIG. 28 is a timing chart showing the on/off timing of the first switch Tr1 to the fourth switch Tr4 and the sixth switch Tr6 when current flows from the motor 20 to the first connection point P1 and the second connection point P2, respectively. FIG. 29 is a diagram showing the state of each switch and the direction of current in a first period T51 in the PWM cycle TP shown in FIG. FIG. 30 is a diagram showing the state of each switch and the direction of current in the second period T52 in the PWM cycle TP shown in FIG. FIG. 31 is a diagram showing the state of each switch and the direction of current in a third period T53 in the PWM cycle TP shown in FIG. FIG. 32 is a diagram showing the state of each switch and the direction of current in a fourth period T54 in the PWM cycle TP shown in FIG. FIG. 33 is a diagram showing the state of each switch and the direction of current in a fifth period T55 in the PWM cycle TP shown in FIG. FIG. 34 is a timing chart showing the on/off timing of the first switch Tr1 to the fourth switch Tr4 and the sixth switch Tr6 when a current flows from the motor 20 to the first connection point P1 and the second connection point P2, respectively, and the on period of the second switch Tr2 is shorter than the on period of the fourth switch Tr4 within the PWM period TP. FIG. 35 is a diagram showing the state of each switch and the direction of current in a first period T61 in the PWM cycle TP shown in FIG. FIG. 36 is a diagram showing the state of each switch and the direction of current in a second period T62 in the PWM cycle TP shown in FIG. FIG. 37 is a diagram showing the state of each switch and the direction of current in a third period T63 in the PWM cycle TP shown in FIG. FIG. 38 is a diagram showing the state of each switch and the direction of current in a fourth period T64 in the PWM cycle TP shown in FIG. FIG. 39 is a diagram showing the state of each switch and the direction of current in a fifth period T65 in the PWM cycle TP shown in FIG. FIG. 40 is a timing chart showing the on/off timing of the first switch Tr1 to the fourth switch Tr4 and the sixth switch Tr6 when a current flows from the motor 20 to each of the first connection point P1 and the second connection point P2, and when, within a PWM period TP, the length of the on period of the second switch Tr2 and the length of the on period of the fourth switch Tr4 are different and the center of the on period of the second switch Tr2 and the center of the on period of the fourth switch Tr4 are shifted from each other by a half PWM period. FIG. 41 is a timing chart showing the on/off timing of the first switch Tr1 to the sixth switch Tr6 when a current flows from the first connection point P1 to the motor 20 and a current flows from the motor 20 to the second connection point P2. FIG. 42 is a diagram showing the state of each switch and the direction of current in a first period T81 in the PWM cycle TP shown in FIG. FIG. 43 is a diagram showing the state of each switch and the direction of current in a second period T82 in the PWM cycle TP shown in FIG. FIG. 44 is a diagram showing the state of each switch and the direction of current in the third period T83 in the PWM cycle TP shown in FIG. FIG. 45 is a diagram showing the state of each switch and the direction of current in a fourth period T84 in the PWM cycle TP shown in FIG. FIG. 46 is a diagram showing the state of each switch and the direction of current in a fifth period T85 in the PWM cycle TP shown in FIG. FIG. 47 is a timing chart showing the on/off timing of the first switch Tr1 to the fourth switch Tr4 and the fifth switch Tr5 when a current flows from the first connection point P1 to the motor 20 and a current flows from the motor 20 to the second connection point P2 and when the on period of the first switch Tr1 is longer than the on period of the fourth switch Tr4 within the PWM period TP. FIG. 48 is a diagram showing the state of each switch and the direction of current in a first period T91 in the PWM cycle TP shown in FIG. FIG. 49 is a diagram showing the state of each switch and the direction of current in a second period T92 in the PWM cycle TP shown in FIG. FIG. 50 is a diagram showing the state of each switch and the direction of current in the third period T93 in the PWM cycle TP shown in FIG. FIG. 51 is a diagram showing the state of each switch and the direction of current in a fourth period T94 in the PWM cycle TP shown in FIG. FIG. 52 is a diagram showing the state of each switch and the direction of current in a fifth period T95 in the PWM cycle TP shown in FIG. FIG. 53 is a timing chart showing the on/off timing of the first switch Tr1 to the fourth switch Tr4 and the sixth switch Tr6 when a current flows from the first connection point P1 to the motor 20 and a current flows from the motor 20 to the second connection point P2 and when the on period of the first switch Tr1 is shorter than the on period of the fourth switch Tr4 within the PWM period TP. FIG. 54 is a timing chart showing the on/off timings of the first switch Tr1 to the sixth switch Tr6 in a case where a current flows from the first connection point P1 toward the motor 20 and also flows from the motor 20 toward the second connection point P2, and within a PWM period TP, the length of the on period of the first switch Tr1 and the length of the on period of the fourth switch Tr4 are different and the center of the on period of the first switch Tr1 and the center of the on period of the fourth switch Tr4 are shifted from each other by a half PWM period. FIG. 55 is a diagram showing a modified example of the H-bridge circuit BC and the auxiliary circuit SC.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.
Fig. 1 is a diagram showing a schematic configuration of a motor module 1 in this embodiment. As shown in Fig. 1, the motor module 1 includes a power conversion device 10 and a motor 20. The motor 20 has two N-phase terminal groups (N is an integer equal to or greater than 3). In this embodiment, as an example, N is 3. That is, the motor 20 is a three-phase motor having two three-phase terminal groups.

The motor 20 has a first U-phase terminal 21u, a first V-phase terminal 21v, and a first W-phase terminal 21w as one three-phase terminal group. The motor 20 has a second U-phase terminal 22u, a second V-phase terminal 22v, and a second W-phase terminal 22w as the other three-phase terminal group. The motor 20 further has a first U-phase coil 23u, a first V-phase coil 23v, a first W-phase coil 23w, a second U-phase coil 24u, a second V-phase coil 24v, and a second W-phase coil 24w.

Although not shown in FIG. 1, the motor 20 has a motor case, and a rotor and a stator housed in the motor case. The rotor is a rotating body that is rotatably supported inside the motor case by bearing parts such as rotor bearings. The rotor has an output shaft that is coaxially joined to the rotor and passes axially through the radial inside of the rotor. The stator is set inside the motor case, surrounding the outer circumferential surface of the rotor, and generates the electromagnetic force required to rotate the rotor.

The first U-phase coil 23u, the first V-phase coil 23v, and the first W-phase coil 23w are excitation coils provided on the stator. One end of the first U-phase coil 23u is electrically connected to the first U-phase terminal 21u. One end of the first V-phase coil 23v is electrically connected to the first V-phase terminal 21v. One end of the first W-phase coil 23w is electrically connected to the first W-phase terminal 21w. The other end of the first U-phase coil 23u, the other end of the first V-phase coil 23v, and the other end of the first W-phase coil 23w are electrically connected to each other.

The second U-phase coil 24u, the second V-phase coil 24v, and the second W-phase coil 24w are excitation coils provided on the stator. One end of the second U-phase coil 24u is electrically connected to the second U-phase terminal 22u. One end of the second V-phase coil 24v is electrically connected to the second V-phase terminal 22v. One end of the second W-phase coil 24w is electrically connected to the second W-phase terminal 22w. The other end of the second U-phase coil 24u, the other end of the second V-phase coil 24v, and the other end of the second W-phase coil 24w are electrically connected to each other.

The power conversion device 10 controls the energization state of each coil included in the motor 20, generating the electromagnetic force required to rotate the rotor. As the rotor rotates, the output shaft also rotates in sync with the rotor.

The power conversion device 10 includes a first three-phase full bridge circuit 11, a second three-phase full bridge circuit 12, and a control unit 13. The first three-phase full bridge circuit 11 is electrically connected to one of the three-phase terminal groups of the motor 20. The second three-phase full bridge circuit 12 is electrically connected to the other of the three-phase terminal groups of the motor 20. The first three-phase full bridge circuit 11 and the second three-phase full bridge circuit 12 are each electrically connected to a DC power supply 30.

The first three-phase full bridge circuit 11 and the second three-phase full bridge circuit 12 operate in cooperation with each other according to the gate signals output from the control unit 13, thereby performing mutual conversion between DC power and three-phase AC power between the DC power supply 30 and the motor 20. For example, when the first three-phase full bridge circuit 11 and the second three-phase full bridge circuit 12 operate as a dual inverter, the power conversion device 10 converts the DC power supplied from the DC power supply 30 into three-phase AC power and outputs it to the motor 20.

The first three-phase full-bridge circuit 11 has a total of six switches: three high-side switches and three low-side switches. The first three-phase full-bridge circuit 11 has a first U-phase high-side switch UH1, a first V-phase high-side switch VH1, a first W-phase high-side switch WH1, a first U-phase low-side switch UL1, a first V-phase low-side switch VL1, and a first W-phase low-side switch WL1. In this embodiment, each switch included in the first three-phase full-bridge circuit 11 is, for example, an n-channel MOS-FET (Metal-Oxide-Semiconductor Field-Effect Transistor).

Note that each switch may be, for example, an IGBT (Insulated Gate Bipolar Transistor) or a JFET (Junction Field Effect Transistor). Diodes are connected in inverse parallel to these switches. As described above, when using MOS-FETs as switches, the body diodes of the MOS-FETs may be used instead of diodes.

The drain terminal of the first U-phase high-side switch UH1, the drain terminal of the first V-phase high-side switch VH1, and the drain terminal of the first W-phase high-side switch WH1 are each electrically connected to the positive electrode of the DC power supply 30. The source terminal of the first U-phase low-side switch UL1, the source terminal of the first V-phase low-side switch VL1, and the source terminal of the first W-phase low-side switch WL1 are each electrically connected to the negative electrode of the DC power supply 30.

The source terminal of the first U-phase high-side switch UH1 is electrically connected to the first U-phase terminal 21u and the drain terminal of the first U-phase low-side switch UL1. In other words, the source terminal of the first U-phase high-side switch UH1 is electrically connected to one end of the first U-phase coil 23u via the first U-phase terminal 21u.

The source terminal of the first V-phase high-side switch VH1 is electrically connected to the first V-phase terminal 21v and the drain terminal of the first V-phase low-side switch VL1. In other words, the source terminal of the first V-phase high-side switch VH1 is electrically connected to one end of the first V-phase coil 23v via the first V-phase terminal 21v.

The source terminal of the first W-phase high-side switch WH1 is electrically connected to the first W-phase terminal 21w and the drain terminal of the first W-phase low-side switch WL1. In other words, the source terminal of the first W-phase high-side switch WH1 is electrically connected to one end of the first W-phase coil 23w via the first W-phase terminal 21w.

Although not shown in FIG. 1, the gate terminal of the first U-phase high-side switch UH1, the gate terminal of the first V-phase high-side switch VH1, and the gate terminal of the first W-phase high-side switch WH1 are each electrically connected to the control unit 13. Similarly, the gate terminal of the first U-phase low-side switch UL1, the gate terminal of the first V-phase low-side switch VL1, and the gate terminal of the first W-phase low-side switch WL1 are each electrically connected to the control unit 13.

The second three-phase full bridge circuit 12 has a total of six switches: three high-side switches and three low-side switches. The second three-phase full bridge circuit 12 has a second U-phase high-side switch UH2, a second V-phase high-side switch VH2, a second W-phase high-side switch WH2, a second U-phase low-side switch UL2, a second V-phase low-side switch VL2, and a second W-phase low-side switch WL2. In this embodiment, each switch included in the second three-phase full bridge circuit 12 is, for example, an n-channel MOS-FET.

The drain terminal of the second U-phase high-side switch UH2, the drain terminal of the second V-phase high-side switch VH2, and the drain terminal of the second W-phase high-side switch WH2 are each electrically connected to the positive electrode of the DC power supply 30. The source terminal of the second U-phase low-side switch UL2, the source terminal of the second V-phase low-side switch VL2, and the source terminal of the second W-phase low-side switch WL2 are each electrically connected to the negative electrode of the DC power supply 30.

The source terminal of the second U-phase high-side switch UH2 is electrically connected to the second U-phase terminal 22u and the drain terminal of the second U-phase low-side switch UL2. In other words, the source terminal of the second U-phase high-side switch UH2 is electrically connected to the other end of the second U-phase coil 24u via the second U-phase terminal 22u.

The source terminal of the second V-phase high-side switch VH2 is electrically connected to the second V-phase terminal 22v and the drain terminal of the second V-phase low-side switch VL2. In other words, the source terminal of the second V-phase high-side switch VH2 is electrically connected to the other end of the second V-phase coil 24v via the second V-phase terminal 22v.

The source terminal of the second W-phase high-side switch WH2 is electrically connected to the second W-phase terminal 22w and the drain terminal of the second W-phase low-side switch WL2. In other words, the source terminal of the second W-phase high-side switch WH2 is electrically connected to the other end of the second W-phase coil 24w via the second W-phase terminal 22w.

Although not shown in FIG. 1, the gate terminal of the second U-phase high-side switch UH2, the gate terminal of the second V-phase high-side switch VH2, and the gate terminal of the second W-phase high-side switch WH2 are each electrically connected to the control unit 13. Similarly, the gate terminal of the second U-phase low-side switch UL2, the gate terminal of the second V-phase low-side switch VL2, and the gate terminal of the second W-phase low-side switch WL2 are each electrically connected to the control unit 13.

The control unit 13 controls each switch included in the first three-phase full-bridge circuit 11 and the second three-phase full-bridge circuit 12. As an example, the control unit 13 is an MCU (Microcontroller Unit). The control unit 13 generates gate signals required to control each switch by pulse width modulation, and outputs the gate signals to the gate terminals of each switch.

As can be understood from the above description, the power conversion device 10 includes an H-bridge circuit corresponding to each phase of the motor 20. Although not shown in FIG. 1, the power conversion device 10 further includes an auxiliary circuit corresponding to at least one of the H-bridge circuits. Below, the circuit configuration of the H-bridge circuit and the auxiliary circuit will be described using the H-bridge circuit corresponding to the U-phase and the auxiliary circuit corresponding to that H-bridge circuit as a representative example.

FIG. 2 is a diagram showing the circuit configuration of an H-bridge circuit BC corresponding to the U-phase and an auxiliary circuit SC corresponding to the H-bridge circuit BC. As shown in FIG. 2, the H-bridge circuit BC includes a first leg U1 and a second leg U2. The first leg U1 includes a first switch Tr1 corresponding to the first U-phase high-side switch UH1, and a second switch Tr2 corresponding to the first U-phase low-side switch UL1. The second leg U2 includes a third switch Tr3 corresponding to the second U-phase high-side switch UH2, and a fourth switch Tr4 corresponding to the second U-phase low-side switch UL2.

The first switch Tr1 is electrically connected between the positive electrode of the DC power supply 30 and the first connection point P1. Specifically, the drain terminal of the first switch Tr1 is electrically connected to the positive electrode of the DC power supply 30, and the source terminal of the first switch Tr1 is electrically connected to the first connection point P1. The first connection point P1 is a node electrically connected to the first U-phase terminal 21u of the motor 20.

The second switch Tr2 is electrically connected between the negative electrode of the DC power supply 30 and the first connection point P1. Specifically, the source terminal of the second switch Tr2 is electrically connected to the negative electrode of the DC power supply 30, and the drain terminal of the second switch Tr2 is electrically connected to the first connection point P1.

The third switch Tr3 is electrically connected between the positive electrode of the DC power supply 30 and the second connection point P2. Specifically, the drain terminal of the third switch Tr3 is electrically connected to the positive electrode of the DC power supply 30, and the source terminal of the third switch Tr3 is electrically connected to the second connection point P2. The second connection point P2 is a node electrically connected to the second U-phase terminal 22u of the motor 20.

The fourth switch Tr4 is electrically connected between the negative electrode of the DC power supply 30 and the second connection point P2. Specifically, the source terminal of the fourth switch Tr4 is electrically connected to the negative electrode of the DC power supply 30, and the drain terminal of the fourth switch Tr4 is electrically connected to the second connection point P2.

The auxiliary circuit SC includes a first rectifier element D1, a second rectifier element D2, a third rectifier element D3, a fourth rectifier element D4, a fifth rectifier element D5, a sixth rectifier element D6, a first inductor L1, a second inductor L2, a third inductor L3, a fourth inductor L4, a fifth switch Tr5, and a sixth switch Tr6. For example, the first rectifier element D1 to the sixth rectifier element D6 are each diodes. Also, for example, the fifth switch Tr5 and the sixth switch Tr6 are each n-channel MOS-FETs.

The first rectifier element D1 and the first inductor L1 are connected in series between the first connection point P1 and the third connection point P3. Specifically, the anode terminal of the first rectifier element D1 is electrically connected to the third connection point P3, and the cathode terminal of the first rectifier element D1 is electrically connected to one end of the first inductor L1. The other end of the first inductor L1 is electrically connected to the first connection point P1. The anode terminal corresponds to the positive terminal, and the cathode terminal corresponds to the negative terminal.

The second rectifier element D2 and the second inductor L2 are connected in series between the second connection point P2 and the third connection point P3. Specifically, the anode terminal of the second rectifier element D2 is electrically connected to the third connection point P3, and the cathode terminal of the second rectifier element D2 is electrically connected to one end of the second inductor L2. The other end of the second inductor L2 is electrically connected to the second connection point P2.

The third rectifier element D3 and the third inductor L3 are connected in series between the first connection point P1 and the fourth connection point P4. Specifically, the cathode terminal of the third rectifier element D3 is electrically connected to the fourth connection point P4, and the anode terminal of the third rectifier element D3 is electrically connected to one end of the third inductor L3. The other end of the third inductor L3 is electrically connected to the first connection point P1.

The fourth rectifier element D4 and the fourth inductor L4 are connected in series between the second connection point P2 and the fourth connection point P4. Specifically, the cathode terminal of the fourth rectifier element D4 is electrically connected to the fourth connection point P4, and the anode terminal of the fourth rectifier element D4 is electrically connected to one end of the fourth inductor L4. The other end of the fourth inductor L4 is electrically connected to the second connection point P2.

The fifth rectifier element D5 has a cathode terminal electrically connected to the third connection point P3 and an anode terminal electrically connected to the negative electrode of the DC power supply 30. The sixth rectifier element D6 has a cathode terminal electrically connected to the positive electrode of the DC power supply 30 and an anode terminal electrically connected to the fourth connection point P4.

The fifth switch Tr5 is electrically connected between the positive electrode of the DC power supply 30 and the third connection point P3. Specifically, the drain terminal of the fifth switch Tr5 is electrically connected to the positive electrode of the DC power supply 30, and the source terminal of the fifth switch Tr5 is electrically connected to the third connection point P3.

The sixth switch Tr6 is electrically connected between the negative electrode of the DC power supply 30 and the fourth connection point P4. Specifically, the source terminal of the sixth switch Tr6 is electrically connected to the negative electrode of the DC power supply 30, and the drain terminal of the sixth switch Tr6 is electrically connected to the fourth connection point P4.

The control unit 13 controls the H-bridge circuit BC and the auxiliary circuit SC. The control unit 13 controls the first switch Tr1 to the fourth switch Tr4 included in the H-bridge circuit BC, and the fifth switch Tr5 and the sixth switch Tr6 included in the auxiliary circuit SC.

As described above, in the auxiliary circuit SC, the anode terminal of the first rectifier element D1 and the anode terminal of the second rectifier element D2 are located on the side of the third connection point P3. If the condition that the anode terminal of the first rectifier element D1 is located on the side of the third connection point P3 is satisfied, the position of the first rectifier element D1 and the position of the first inductor L1 may be interchanged. Similarly, if the condition that the anode terminal of the second rectifier element D2 is located on the side of the third connection point P3 is satisfied, the position of the second rectifier element D2 and the position of the second inductor L2 may be interchanged.

In the auxiliary circuit SC, the cathode terminal of the third rectifier element D3 and the cathode terminal of the fourth rectifier element D4 are located on the side of the fourth connection point P4. If the condition that the cathode terminal of the third rectifier element D3 is located on the side of the fourth connection point P4 is satisfied, the position of the third rectifier element D3 and the position of the third inductor L3 may be interchanged. Similarly, if the condition that the cathode terminal of the fourth rectifier element D4 is located on the side of the fourth connection point P4 is satisfied, the position of the fourth rectifier element D4 and the position of the fourth inductor L4 may be interchanged.

The above is an explanation of the configuration of the motor module 1. Below, the operation of the control unit 13 provided in the power conversion device 10 will be explained. Note that, for ease of explanation, the operation of the control unit 13 will be explained below with reference to the H-bridge circuit BC corresponding to the U-phase and the auxiliary circuit SC corresponding to that H-bridge circuit BC, among the H-bridge circuits corresponding to each phase of the motor 20, but it should be noted that the same operation also applies to the V-phase and W-phase.

The control unit 13 has a first mode in which the first leg U1 and the second leg U2 output voltages of the same phase, and a second mode in which the first leg U1 and the second leg U2 output voltages of opposite phases. For example, the control unit 13 operates in the first mode when the motor 20 is operating at low speed, and operates in the second mode when the motor 20 is operating at high speed. With this control, when switching from low speed to high speed operation, the number of poles of the motor 20 is equivalently switched from four poles to two poles, so that torque deficiency during high speed operation can be eliminated without increasing the size of the motor 20.

As described above, the control of switching the number of poles according to the rotation speed of the motor 20 is disclosed in Patent Document 1, so a detailed description will be omitted in this embodiment. In this embodiment, a detailed description will be given of the operation performed by the control unit 13 in each mode to achieve soft switching that reduces switching loss in at least one of the first switch Tr1 to the fourth switch Tr4 included in the H-bridge circuit BC. In the following description, the operation performed by the control unit 13 to achieve soft switching may be referred to as a "soft switching operation."

First, before describing each embodiment of the soft switching operation, the basic soft switching operation that is the basis of the soft switching operation will be described. As the basic soft switching operation, the control unit 13 performs at least one of the following: a first operation of turning on the fifth switch Tr5 for a first time before turning on at least one of the first switch Tr1 and the third switch Tr3 within one control period of the pulse width modulation; and a second operation of turning on the sixth switch Tr6 for a second time before turning on at least one of the second switch Tr2 and the fourth switch Tr4 within one control period of the pulse width modulation. Hereinafter, one control period of the pulse width modulation may be referred to as a "PWM (Pulse Width Modulation) period."

FIG. 3 is a timing chart showing the on/off timing of the first switch Tr1, the second switch Tr2, and the fifth switch Tr5 when a current flows from the first connection point P1 of the first leg U1 toward the motor 20. As shown in FIG. 3, when a current flows from the first connection point P1 toward the motor 20, the first operation is to turn on the fifth switch Tr5 for a first time within the PWM period TP before turning on the first switch Tr1. Note that in FIG. 3, the state of the second leg U2 is not taken into consideration.

FIG. 4 is a diagram showing the state of each switch and the direction of current during the first period T1 in the PWM cycle TP shown in FIG. 3. For ease of explanation, in the following, the current flowing toward the top of each circuit diagram may be referred to as the "upward current," the current flowing toward the bottom of each circuit diagram as the "downward current," the current flowing toward the right side of each circuit diagram as the "rightward current," and the current flowing toward the left side of each circuit diagram as the "leftward current."

As shown in FIG. 4, in the first period T1, the first switch Tr1 is off, the second switch Tr2 is on, and the fifth switch Tr5 is off. In the first period T1, an upward current flows through the second switch Tr2, and a current flows from the first connection point P1 toward the motor 20. In the first period T1, the potential of the first connection point P1 is approximately equal to the negative electrode potential of the DC power supply 30.

FIG. 5 is a diagram showing the state of each switch and the direction of the current during the second period T2 in the PWM cycle TP shown in FIG. 3. As shown in FIG. 5, during the second period T2, the first switch Tr1 is off, the second switch Tr2 is on, and the fifth switch Tr5 is on. When the fifth switch Tr5 is turned on during the second period T2, the potential of the third connection point P3 of the auxiliary circuit SC becomes approximately equal to the positive electrode potential of the DC power supply 30, and a rightward current flows through the first inductor L1. During the second period T2, when the rightward current flowing through the first inductor L1 becomes larger than the current flowing from the first connection point P1 toward the motor 20, a downward current flows through the second switch Tr2. The second period T2 corresponds to the first time during which the fifth switch Tr5 is turned on.

FIG. 6 is a diagram showing the state of each switch and the direction of the current during the third period T3 in the PWM cycle TP shown in FIG. 3. As shown in FIG. 6, during the third period T3, the first switch Tr1 is off, the second switch Tr2 is on, and the fifth switch Tr5 is off. When the fifth switch Tr5 is turned off during the third period T3, the downward current flowing through the second switch Tr2 is commutated from the fifth switch Tr5 to the fifth rectifier element D5, and an upward current flows through the fifth rectifier element D5. During the third period T3, the potential of the third connection point P3 is approximately equal to the negative electrode potential of the DC power supply 30.

FIG. 7 is a diagram showing the state of each switch and the direction of the current during the fourth period T4 in the PWM cycle TP shown in FIG. 3. As shown in FIG. 7, during the fourth period T4, the first switch Tr1 is off, the second switch Tr2 is off, and the fifth switch Tr5 is off. When the second switch Tr2 is turned off during the fourth period T4, the current flowing through the fifth rectifier element D5 and the first inductor L1 is commutated from the second switch Tr2 to the first switch Tr1, and an upward current flows through the body diode of the first switch Tr1. During the fourth period T4, the potential of the first connection point P1 is approximately equal to the positive electrode potential of the DC power supply 30, so that the voltage across the first switch Tr1 is approximately zero. The voltage across the first switch Tr1 is the potential difference between the drain terminal and the source terminal. Note that during the fourth period T4, a reverse voltage is applied to the first inductor L1, so the rightward current flowing through the first inductor L1 gradually decreases.

FIG. 8 is a diagram showing the state of each switch and the direction of current during the fifth period T5 in the PWM cycle TP shown in FIG. 3. As shown in FIG. 8, during the fifth period T5, the first switch Tr1 is on, the second switch Tr2 is off, and the fifth switch Tr5 is off. During the fifth period T5, as the current flowing through the first inductor L1 decreases, the upward current flowing through the first switch Tr1 also decreases. Then, when the current flowing through the first inductor L1 becomes smaller than the current flowing from the first connection point P1 toward the motor 20, a downward current flows through the first switch Tr1. When the current flowing through the first inductor L1 becomes zero, the current flowing downward through the first switch Tr1 and the current flowing from the first connection point P1 toward the motor 20 match.

As described above, when a current flows from the first connection point P1 toward the motor 20, the control unit 13 performs a first operation of turning on the fifth switch Tr5 for a first time before turning on the first switch Tr1 within the PWM period TP. As a result, the voltage across the first switch Tr1 becomes nearly zero before the first switch Tr1 is turned on. In other words, by the control unit 13 performing the above first operation, soft switching of the first switch Tr1 is realized, and the switching loss of the first switch Tr1 can be reduced.

When a current flows from the second connection point P2 toward the motor 20, the first operation is an operation of turning on the fifth switch Tr5 for a first time before turning on the third switch Tr3 within the PWM period TP. That is, when a current flows from the second connection point P2 toward the motor 20, the control unit 13 performs a first operation of turning on the fifth switch Tr5 for a first time before turning on the third switch Tr3 within the PWM period TP. As a result, the voltage across the third switch Tr3 becomes almost zero before the third switch Tr3 is turned on. That is, when the control unit 13 performs the above first operation, soft switching of the third switch Tr3 is realized, and the switching loss of the third switch Tr3 can be reduced.

FIG. 9 is a timing chart showing the on/off timing of the first switch Tr1, the second switch Tr2, and the sixth switch Tr6 when a current flows from the motor 20 toward the first connection point P1. As shown in FIG. 9, when a current flows from the motor 20 toward the first connection point P1, the second operation is an operation of turning on the sixth switch Tr6 for a second time within the PWM period TP before turning on the second switch Tr2. Note that in FIG. 9, the state of the second leg U2 is not taken into consideration.

FIG. 10 is a diagram showing the state of each switch and the direction of current during the first period T11 in the PWM cycle TP shown in FIG. 9. As shown in FIG. 10, during the first period T11, the first switch Tr1 is on, the second switch Tr2 is off, and the sixth switch Tr6 is off. During the first period T11, a current flows from the motor 20 toward the first connection point P1, and an upward current flows through the first switch Tr1. During the first period T11, the potential of the first connection point P1 is approximately equal to the positive electrode potential of the DC power supply 30.

11 is a diagram showing the state of each switch and the direction of the current during the second period T12 in the PWM cycle TP shown in FIG. 9. As shown in FIG. 11, during the second period T12, the first switch Tr1 is on, the second switch Tr2 is off, and the sixth switch Tr6 is on. When the sixth switch Tr6 is on during the second period T12, the potential of the fourth connection point P4 of the auxiliary circuit SC becomes approximately equal to the negative electrode potential of the DC power supply 30, and a rightward current flows through the third inductor L3. During the second period T12, when the rightward current flowing through the third inductor L3 becomes larger than the current flowing from the motor 20 toward the first connection point P1, a downward current flows through the first switch Tr1. The second period T12 corresponds to the second time during which the sixth switch Tr6 is on.

FIG. 12 is a diagram showing the state of each switch and the direction of the current during the third period T13 in the PWM cycle TP shown in FIG. 9. As shown in FIG. 12, during the third period T13, the first switch Tr1 is on, the second switch Tr2 is off, and the sixth switch Tr6 is off. When the sixth switch Tr6 is turned off during the third period T13, the rightward current flowing through the third inductor L3 is commutated from the sixth switch Tr6 to the sixth rectifier element D6, and an upward current flows through the sixth rectifier element D6. During the third period T13, the potential of the fourth connection point P4 is approximately equal to the positive electrode potential of the DC power supply 30.

13 is a diagram showing the state of each switch and the direction of the current during the fourth period T14 in the PWM cycle TP shown in FIG. 9. As shown in FIG. 13, during the fourth period T14, the first switch Tr1 is off, the second switch Tr2 is off, and the sixth switch Tr6 is off. When the first switch Tr1 is turned off during the fourth period T14, the current flowing through the third inductor L3 and the sixth rectifier element D6 is commutated from the first switch Tr1 to the second switch Tr2, and an upward current flows through the body diode of the second switch Tr2. During the fourth period T14, the potential of the first connection point P1 is approximately equal to the negative electrode potential of the DC power supply 30, so that the voltage across the second switch Tr2 is approximately zero. Note that during the fourth period T14, a reverse voltage is applied to the third inductor L3, so the rightward current flowing through the third inductor L3 gradually decreases.

14 is a diagram showing the state of each switch and the direction of the current during the fifth period T15 in the PWM cycle TP shown in FIG. 9. As shown in FIG. 14, during the fifth period T15, the first switch Tr1 is off, the second switch Tr2 is on, and the sixth switch Tr6 is off. During the fifth period T15, as the current flowing through the third inductor L3 decreases, the upward current flowing through the second switch Tr2 also decreases. Then, when the current flowing through the third inductor L3 becomes smaller than the current flowing from the motor 20 toward the first connection point P1, a downward current flows through the second switch Tr2. When the current flowing through the third inductor L3 becomes zero, the current flowing downward through the second switch Tr2 and the current flowing from the motor 20 toward the first connection point P1 match.

As described above, when a current flows from the motor 20 toward the first connection point P1, the control unit 13 performs the second operation of turning on the sixth switch Tr6 for the second time before turning on the second switch Tr2 within the PWM period TP. As a result, the voltage across the second switch Tr2 becomes almost zero before the second switch Tr2 is turned on. In other words, by the control unit 13 performing the above-mentioned second operation, soft switching of the second switch Tr2 is realized, and the switching loss of the second switch Tr2 can be reduced.

When a current flows from the motor 20 toward the second connection point P2, the second operation is an operation of turning on the sixth switch Tr6 for a second time before turning on the fourth switch Tr4 within the PWM period TP. That is, when a current flows from the motor 20 toward the second connection point P2, the control unit 13 performs a second operation of turning on the sixth switch Tr6 for a second time before turning on the fourth switch Tr4 within the PWM period TP. As a result, the voltage across the fourth switch Tr4 becomes almost zero before the fourth switch Tr4 is turned on. That is, when the control unit 13 performs the above-mentioned second operation, soft switching of the fourth switch Tr4 is realized, and the switching loss of the fourth switch Tr4 can be reduced.

　Based on the above basic soft switching operation, we will now explain various examples of soft switching operation.

Example 1
Fig. 15 is a timing chart showing the on/off timing of the first switch Tr1 to the fourth switch Tr4 and the fifth switch Tr5 when current flows from the first connection point P1 and the second connection point P2 toward the motor 20. Fig. 15 also shows changes in the currents of the first inductor L1 and the second inductor L2, the currents of the first switch Tr1 and the third switch Tr3, and the voltages across the first switch Tr1 and the third switch Tr3.

In FIG. 15, I_L1 indicates the current of the first inductor L1, and I_L2 indicates the current of the second inductor L2. I_Tr1 indicates the current of the first switch Tr1, and I_Tr3 indicates the current of the third switch Tr3. V_Tr1 indicates the voltage across the first switch Tr1, and V_Tr3 indicates the voltage across the third switch Tr3.

15, when current flows from each of the first connection point P1 and the second connection point P2 toward the motor 20, the control unit 13 turns on both the first switch Tr1 and the third switch Tr3 at a first timing, and performs a first operation before the first timing within the PWM period TP. In other words, when current flows from each of the first connection point P1 and the second connection point P2 toward the motor 20, the control unit 13 performs a first operation of turning on the fifth switch Tr5 for a first time before simultaneously turning on the first switch Tr1 and the third switch Tr3 within the PWM period TP.

FIG. 16 is a diagram showing the state of each switch and the direction of current during the first period T21 in the PWM cycle TP shown in FIG. 15. As shown in FIG. 16, during the first period T21, the first switch Tr1 and the third switch Tr3 are off, the second switch Tr2 and the fourth switch Tr4 are on, and the fifth switch Tr5 is off. During the first period T21, an upward current flows through the second switch Tr2 and the fourth switch Tr4, and a current flows from each of the first connection point P1 and the second connection point P2 toward the motor 20. During the first period T21, the potentials of the first connection point P1 and the second connection point P2 are approximately equal to the negative electrode potential of the DC power supply 30.

17 is a diagram showing the state of each switch and the direction of current during the second period T22 in the PWM cycle TP shown in FIG. 15. As shown in FIG. 17, during the second period T22, the first switch Tr1 and the third switch Tr3 are off, the second switch Tr2 and the fourth switch Tr4 are on, and the fifth switch Tr5 is on. During the second period T22, when the fifth switch Tr5 is turned on, the potential of the third connection point P3 becomes approximately equal to the positive electrode potential of the DC power supply 30, and a rightward current flows through the first inductor L1 and the second inductor L2. During the second period T22, when the rightward current flowing through the first inductor L1 becomes larger than the current flowing from the first connection point P1 toward the motor 20, a downward current flows through the second switch Tr2. In addition, in the second period T22, when the rightward current flowing through the second inductor L2 becomes larger than the current flowing from the second connection point P2 toward the motor 20, a downward current flows through the fourth switch Tr4. The second period T22 corresponds to the first time during which the fifth switch Tr5 is turned on.

18 is a diagram showing the state of each switch and the direction of the current during the third period T23 in the PWM cycle TP shown in FIG. 15. As shown in FIG. 18, during the third period T23, the first switch Tr1 and the third switch Tr3 are off, the second switch Tr2 and the fourth switch Tr4 are on, and the fifth switch Tr5 is off. When the fifth switch Tr5 is turned off during the third period T23, the downward current flowing through the second switch Tr2 is commutated from the fifth switch Tr5 to the fifth rectifier element D5, and an upward current flows through the fifth rectifier element D5. During the third period T23, the potential of the third connection point P3 is approximately equal to the negative electrode potential of the DC power supply 30.

19 is a diagram showing the state of each switch and the direction of current during the fourth period T24 in the PWM cycle TP shown in FIG. 15. As shown in FIG. 19, during the fourth period T24, the first switch Tr1 and the third switch Tr3 are off, the second switch Tr2 and the fourth switch Tr4 are off, and the fifth switch Tr5 is off. During the fourth period T24, when the second switch Tr2 and the fourth switch Tr4 are turned off, the current flowing through the first inductor L1 is commutated from the second switch Tr2 to the first switch Tr1, and the current flowing through the second inductor L2 is commutated from the fourth switch Tr4 to the third switch Tr3, and an upward current flows through the body diodes of the first switch Tr1 and the third switch Tr3. In addition, in the fourth period T24, the potentials of the first connection point P1 and the second connection point P2 are approximately equal to the positive electrode potential of the DC power supply 30, so the voltages across the first switch Tr1 and the third switch Tr3 are approximately zero. In addition, in the fourth period T24, a reverse voltage is applied to the first inductor L1 and the second inductor L2, so the rightward current flowing through the first inductor L1 and the second inductor L2 gradually decreases.

20 is a diagram showing the state of each switch and the direction of current in a fifth period T25 in the PWM cycle TP shown in FIG. 15. As shown in FIG. 20, in the fifth period T25, the first switch Tr1 and the third switch Tr3 are on, the second switch Tr2 and the fourth switch Tr4 are off, and the fifth switch Tr5 is off. In the fifth period T25, as the current flowing through the first inductor L1 and the second inductor L2 decreases, the upward current flowing through the first switch Tr1 and the third switch Tr3 also decreases. Then, when the current flowing through the first inductor L1 becomes smaller than the current flowing from the first connection point P1 to the motor 20 and the current flowing through the second inductor L2 becomes smaller than the current flowing from the second connection point P2 to the motor 20, a downward current flows through the first switch Tr1 and the third switch Tr3.
When the current flowing through the first inductor L1 becomes zero, the current flowing downward through the first switch Tr1 matches the current flowing from the first connection point P1 toward the motor 20. When the current flowing through the second inductor L2 becomes zero, the current flowing downward through the third switch Tr3 matches the current flowing from the second connection point P2 toward the motor 20.

As described above, as a first operation when current flows from each of the first connection point P1 and the second connection point P2 toward the motor 20, the control unit 13 turns off the first switch Tr1 and the third switch Tr3, turns on the second switch Tr2 and the fourth switch Tr4, and turns off the fifth switch Tr5 during the first period T21 from the on timing of the second switch Tr2 and the fourth switch Tr4 to the on timing of the fifth switch Tr5.
Then, in a second period T22 which is the period after the first period T21 and corresponds to the first time, the control unit 13 turns off the first switch Tr1 and the third switch Tr3, turns on the second switch Tr2 and the fourth switch Tr4, and turns on the fifth switch Tr5.
Then, in a third period T23 following the second period T22, the control unit 13 turns off the first switch Tr1 and the third switch Tr3, turns on the second switch Tr2 and the fourth switch Tr4, and turns off the fifth switch Tr5.
Furthermore, during a fourth period T24 from the end timing of the third period T23 to the on timing of the first switch Tr1 and the third switch Tr3, the control unit 13 turns off the first switch Tr1 and the third switch Tr3, turns off the second switch Tr2 and the fourth switch Tr4, and turns off the fifth switch Tr5.

As described above, when a current flows from each of the first connection point P1 and the second connection point P2 toward the motor 20, the control unit 13 performs a first operation of turning on the fifth switch Tr5 for a first time before simultaneously turning on the first switch Tr1 and the third switch Tr3 within the PWM period TP. As a result, the voltages across the first switch Tr1 and the third switch Tr3 become substantially zero before the first switch Tr1 and the third switch Tr3 are simultaneously turned on. Therefore, when a current flows from each of the first connection point P1 and the second connection point P2 toward the motor 20, the control unit 13 performs the above-mentioned soft switching operation, thereby realizing soft switching of the first switch Tr1 and the third switch Tr3 and reducing switching loss of the first switch Tr1 and the third switch Tr3.
In this manner, by synchronizing the turn-on timing of the first switch Tr1 and the third switch Tr3, soft switching can be achieved in both the first leg U1 and the second leg U2.
The auxiliary circuit SC includes only two switch elements, a fifth switch Tr5 and a sixth switch Tr6. This auxiliary circuit SC can perform soft switching in both the first leg U1 and the second leg U2. This allows the auxiliary circuit SC, the drive circuit for the auxiliary circuit SC, and the control signal for the auxiliary circuit SC to be simplified, thereby achieving reduced circuit costs and area.

The above-mentioned Example 1 is an example of soft switching operation in which the first leg U1 and the second leg U2 output voltages of the same phase, and currents flow from the first connection point P1 and the second connection point P2 toward the motor 20. However, when controlling the number of poles to be switched while the motor 20 is rotating, the output voltage of the first leg U1 and the output voltage of the second leg U2 are not simply in phase or out of phase, but the first leg U1 and the second leg U2 have different duties.

Since the pole number switching control is performed in a short time, even if the operation of the auxiliary circuit SC is stopped and hard switching of each switch included in the H-bridge circuit BC is performed during the period in which the pole number switching control is performed, switching loss does not increase. However, as will be explained in the following Example 2, by operating the auxiliary circuit SC in synchronization with either the first leg U1 or the second leg U2, switching loss can be minimized.

Example 2
FIG. 21 is a timing chart showing the on/off timing of the first switch Tr1 to the fourth switch Tr4 and the fifth switch Tr5 when a current flows from each of the first connection point P1 and the second connection point P2 toward the motor 20 and the on period of the first switch Tr1 is shorter than the on period of the third switch Tr3 within the PWM period TP.

In this way, when a current flows from each of the first connection point P1 and the second connection point P2 toward the motor 20, and the length of the on-period of the first switch Tr1 and the length of the on-period of the third switch Tr3 are different within the PWM period TP, the control unit 13 turns on the other switch at the second timing when one of the first switch Tr1 and the third switch Tr3 is on and the other switch is off, and performs the first operation before the second timing within the PWM period TP.

In the example shown in FIG. 21, when the third switch Tr3 is on and the first switch Tr1 is off within the PWM period TP, the control unit 13 turns on the fifth switch Tr5 for a first time before the second timing at which the first switch Tr1 is turned on.

22 is a diagram showing the state of each switch and the direction of current during the first period T31 in the PWM cycle TP shown in FIG. 21. As shown in FIG. 22, during the first period T31, the first switch Tr1 and the fourth switch Tr4 are off, the second switch Tr2 and the third switch Tr3 are on, and the fifth switch Tr5 is off. During the first period T31, an upward current flows through the second switch Tr2, a downward current flows through the third switch Tr3, and current flows from each of the first connection point P1 and the second connection point P2 toward the motor 20. During the first period T31, the potential of the first connection point P1 is approximately equal to the negative electrode potential of the DC power supply 30, and the potential of the second connection point P2 is approximately equal to the positive electrode potential of the DC power supply 30.

23 is a diagram showing the state of each switch and the direction of the current during the second period T32 in the PWM cycle TP shown in FIG. 21. As shown in FIG. 23, during the second period T32, the first switch Tr1 and the fourth switch Tr4 are off, the second switch Tr2 and the third switch Tr3 are on, and the fifth switch Tr5 is on. During the second period T32, when the fifth switch Tr5 is turned on, the potential of the third connection point P3 becomes approximately equal to the positive electrode potential of the DC power supply 30, and a rightward current flows through the first inductor L1. During the second period T32, when the rightward current flowing through the first inductor L1 becomes larger than the current flowing from the first connection point P1 toward the motor 20, a downward current flows through the second switch Tr2. The second period T32 corresponds to the first time during which the fifth switch Tr5 is turned on.

24 is a diagram showing the state of each switch and the direction of the current during the third period T33 in the PWM cycle TP shown in FIG. 21. As shown in FIG. 24, during the third period T33, the first switch Tr1 and the fourth switch Tr4 are off, the second switch Tr2 and the third switch Tr3 are on, and the fifth switch Tr5 is off. When the fifth switch Tr5 is turned off during the third period T33, the downward current flowing through the second switch Tr2 is commutated from the fifth switch Tr5 to the fifth rectifier element D5, and an upward current flows through the fifth rectifier element D5. During the third period T33, the potential of the third connection point P3 is approximately equal to the negative electrode potential of the DC power supply 30.

25 is a diagram showing the state of each switch and the direction of the current during the fourth period T34 in the PWM cycle TP shown in FIG. 21. As shown in FIG. 25, during the fourth period T34, the first switch Tr1, the second switch Tr2, and the fourth switch Tr4 are off, the third switch Tr3 is on, and the fifth switch Tr5 is off. When the second switch Tr2 is turned off during the fourth period T34, the current flowing through the first inductor L1 is commutated from the second switch Tr2 to the first switch Tr1, and an upward current flows through the body diode of the first switch Tr1. During the fourth period T34, the potential of the first connection point P1 is approximately equal to the positive electrode potential of the DC power supply 30, so that the voltage across the first switch Tr1 is approximately zero. During the fourth period T34, a reverse voltage is applied to the first inductor L1, so the rightward current flowing through the first inductor L1 gradually decreases.

Fig. 26 is a diagram showing the state of each switch and the direction of current during a fifth period T35 in the PWM cycle TP shown in Fig. 21. As shown in Fig. 26, during the fifth period T35, the first switch Tr1 and the third switch Tr3 are on, the second switch Tr2 and the fourth switch Tr4 are off, and the fifth switch Tr5 is off. During the fifth period T35, as the current flowing through the first inductor L1 decreases, the upward current flowing through the first switch Tr1 also decreases. Then, when the current flowing through the first inductor L1 becomes smaller than the current flowing from the first connection point P1 toward the motor 20, a downward current flows through the first switch Tr1.
When the current flowing through the first inductor L1 becomes zero, the current flowing downward through the first switch Tr1 and the current flowing from the first connection point P1 toward the motor 20 become equal.

As described above, in a state in which the third switch Tr3 is on and the first switch Tr1 is off during a PWM period TP, the control unit 13 turns on the fifth switch Tr5 for the first time before the second timing for turning on the first switch Tr1. As a result, the voltage across the first switch Tr1 becomes almost zero before the first switch Tr1 is turned on. Therefore, when a current flows from each of the first connection point P1 and the second connection point P2 toward the motor 20 and the on period of the first switch Tr1 is shorter than the on period of the third switch Tr3 during a PWM period TP, the control unit 13 performs the above-mentioned soft switching operation, thereby realizing soft switching of the first switch Tr1 and reducing the switching loss of the first switch Tr1.

FIG. 27 is a timing chart showing the on/off timing of the first switch Tr1 to the fourth switch Tr4 and the fifth switch Tr5 when current flows from each of the first connection point P1 and the second connection point P2 toward the motor 20, and the length of the on period of the first switch Tr1 and the length of the on period of the third switch Tr3 are different within a PWM period TP, and the center of the on period of the first switch Tr1 and the center of the on period of the third switch Tr3 are shifted from each other by a half PWM period.

27, in a period T41 in the PWM cycle TP, when the third switch Tr3 is on and the first switch Tr1 is off, the control unit 13 turns on the fifth switch Tr5 for a first time before turning on the first switch Tr1. Also, in the example shown in FIG. 27, in a period T42 in the PWM cycle TP, when the first switch Tr1 is on and the third switch Tr3 is off, the control unit 13 turns on the fifth switch Tr5 for a first time before turning on the third switch Tr3.

As a result, the voltage across the first switch Tr1 becomes almost zero before the first switch Tr1 is turned on, and the voltage across the third switch Tr3 becomes almost zero before the third switch Tr3 is turned on. Therefore, when a current flows from each of the first connection point P1 and the second connection point P2 toward the motor 20, and the length of the on-period of the first switch Tr1 and the length of the on-period of the third switch Tr3 are different within the PWM period TP, and the center of the on-period of the first switch Tr1 and the center of the on-period of the third switch Tr3 are shifted from each other by a half PWM period, the control unit 13 performs the above-mentioned soft switching operation, thereby realizing soft switching of the first switch Tr1 and the third switch Tr3, and reducing the switching loss of the first switch Tr1 and the third switch Tr3.

Example 3
Fig. 28 is a timing chart showing the on/off timing of the first switch Tr1 to the fourth switch Tr4 and the sixth switch Tr6 when a current flows from the motor 20 to the first connection point P1 and the second connection point P2, respectively. Fig. 28 also shows changes in the currents of the third inductor L3 and the fourth inductor L4, the currents of the second switch Tr2 and the fourth switch Tr4, and the voltages across the second switch Tr2 and the fourth switch Tr4.

In FIG. 28, I_L3 indicates the current of the third inductor L3, and I_L4 indicates the current of the fourth inductor L4. I_Tr2 indicates the current of the second switch Tr2, and I_Tr4 indicates the current of the fourth switch Tr4. V_Tr2 indicates the voltage across the second switch Tr2, and V_Tr4 indicates the voltage across the fourth switch Tr4.

28, when a current flows from the motor 20 toward each of the first connection point P1 and the second connection point P2, the control unit 13 turns on both the second switch Tr1 and the fourth switch Tr4 at a third timing, and performs a second operation before the third timing within the PWM period TP. In other words, when a current flows from the motor 20 toward each of the first connection point P1 and the second connection point P2, the control unit 13 performs a second operation of turning on the sixth switch Tr6 for a second time within the PWM period TP before simultaneously turning on the second switch Tr2 and the fourth switch Tr4.

FIG. 29 is a diagram showing the state of each switch and the direction of current during the first period T51 in the PWM cycle TP shown in FIG. 28. As shown in FIG. 29, during the first period T51, the first switch Tr1 and the third switch Tr3 are on, the second switch Tr2 and the fourth switch Tr4 are off, and the sixth switch Tr6 is off. During the first period T51, current flows from the motor 20 toward the first connection point P1 and the second connection point P2, respectively, and an upward current flows through the first switch Tr1 and the third switch Tr3. During the first period T51, the potentials of the first connection point P1 and the second connection point P2 are approximately equal to the positive electrode potential of the DC power supply 30.

30 is a diagram showing the state of each switch and the direction of current during the second period T52 in the PWM cycle TP shown in FIG. 28. As shown in FIG. 30, during the second period T52, the first switch Tr1 and the third switch Tr3 are on, the second switch Tr2 and the fourth switch Tr4 are off, and the sixth switch Tr6 is on. During the second period T52, when the sixth switch Tr6 is turned on, the potential of the fourth connection point P4 becomes approximately equal to the negative electrode potential of the DC power supply 30, and a rightward current flows through the third inductor L3 and the fourth inductor L4. During the second period T52, when the rightward current flowing through the third inductor L3 becomes larger than the current flowing from the motor 20 toward the first connection point P1, a downward current flows through the first switch Tr1. In addition, in the second period T52, when the rightward current flowing through the fourth inductor L4 becomes larger than the current flowing from the motor 20 toward the second connection point P2, a downward current flows through the third switch Tr3. The second period T52 corresponds to the second time during which the sixth switch Tr6 is turned on.

FIG. 31 is a diagram showing the state of each switch and the direction of the current during the third period T53 in the PWM cycle TP shown in FIG. 28. As shown in FIG. 31, during the third period T53, the first switch Tr1 and the third switch Tr3 are on, the second switch Tr2 and the fourth switch Tr4 are off, and the sixth switch Tr6 is off. When the sixth switch Tr6 is turned off during the third period T53, the rightward current flowing through the third inductor L3 and the fourth inductor L4 is commutated from the sixth switch Tr6 to the sixth rectifier element D6, and an upward current flows through the sixth rectifier element D6. During the third period T53, the potential of the fourth connection point P4 is approximately equal to the positive electrode potential of the DC power supply 30.

32 is a diagram showing the state of each switch and the direction of the current during the fourth period T54 in the PWM cycle TP shown in FIG. 28. As shown in FIG. 32, during the fourth period T54, the first switch Tr1 and the third switch Tr3 are off, the second switch Tr2 and the fourth switch Tr4 are off, and the sixth switch Tr6 is off. During the fourth period T54, when the first switch Tr1 and the third switch Tr3 are off, the current flowing through the sixth rectifier element D6 is commutated from the first switch Tr1 to the second switch Tr2 and from the third switch Tr3 to the fourth switch Tr4, and an upward current flows through the body diodes of the second switch Tr2 and the fourth switch Tr4. During the fourth period T54, the potentials of the first connection point P1 and the second connection point P2 are approximately equal to the negative electrode potential of the DC power supply 30, and therefore the voltages across the second switch Tr2 and the fourth switch Tr4 are approximately zero. In addition, in the fourth period T54, a voltage in the opposite direction is applied to the third inductor L3 and the fourth inductor L4, so the rightward current flowing through the third inductor L3 and the fourth inductor L4 gradually decreases.

33 is a diagram showing the state of each switch and the direction of current in the fifth period T55 in the PWM cycle TP shown in FIG. 28. As shown in FIG. 33, in the fifth period T55, the first switch Tr1 and the third switch Tr3 are off, the second switch Tr2 and the fourth switch Tr4 are on, and the sixth switch Tr6 is off. In the fifth period T55, as the current flowing through the third inductor L3 and the fourth inductor L4 decreases, the upward current flowing through the second switch Tr2 and the fourth switch Tr4 also decreases. Then, when the current flowing through the third inductor L3 becomes smaller than the current flowing from the motor 20 to the first connection point P1, a downward current flows through the second switch Tr2. Also, when the current flowing through the fourth inductor L4 becomes smaller than the current flowing from the motor 20 to the second connection point P2, a downward current flows through the fourth switch Tr4.
When the current flowing through the third inductor L3 becomes zero, the current flowing downward through the second switch Tr2 and the current flowing from the motor 20 to the first connection point P1 become equal. When the current flowing through the fourth inductor L4 becomes zero, the current flowing downward through the fourth switch Tr4 and the current flowing from the motor 20 to the second connection point P2 become equal.

As described above, as a second operation in the case where a current flows from the motor 20 to each of the first connection point P1 and the second connection point P2, the control unit 13 turns on the first switch Tr1 and the third switch Tr3, turns off the second switch Tr2 and the fourth switch Tr4, and turns off the sixth switch Tr6 during a fifth period from the on timing of the first switch Tr1 and the third switch Tr3 to the on timing of the sixth switch Tr6. The first period T51 corresponds to the fifth period.
Then, in a sixth period which is a period after the fifth period and corresponds to the second time, the control unit 13 turns on the first switch Tr1 and the third switch Tr3, turns off the second switch Tr2 and the fourth switch Tr4, and turns on the sixth switch Tr6. The second period T52 corresponds to the sixth period.
Then, in a seventh period following the sixth period, the control unit 13 turns on the first switch Tr1 and the third switch Tr3, turns off the second switch Tr2 and the fourth switch Tr4, and turns off the sixth switch Tr6. The third period T53 corresponds to the seventh period.
Furthermore, during an eighth period from the end timing of the seventh period to the ON timing of the second switch Tr2 and the fourth switch Tr4, the control unit 13 turns off the first switch Tr1 and the third switch Tr3, turns off the second switch Tr2 and the fourth switch Tr4, and turns off the sixth switch Tr6. The fourth period T54 corresponds to the eighth period.

As described above, when a current flows from the motor 20 toward each of the first connection point P1 and the second connection point P2, the control unit 13 performs the second operation of turning on the sixth switch Tr6 for the second time before simultaneously turning on the second switch Tr2 and the fourth switch Tr4 within the PWM period TP. As a result, the voltages across the second switch Tr2 and the fourth switch Tr4 become almost zero before the second switch Tr2 and the fourth switch Tr4 are simultaneously turned on. Therefore, when a current flows from the motor 20 toward each of the first connection point P1 and the second connection point P2, the control unit 13 performs the above-mentioned soft switching operation, thereby realizing soft switching of the second switch Tr2 and the fourth switch Tr4 and reducing the switching loss of the second switch Tr2 and the fourth switch Tr4.
In this manner, by synchronizing the turn-on timing of the second switch Tr2 and the fourth switch Tr4, soft switching can be achieved in both the first leg U1 and the second leg U2.
The auxiliary circuit SC includes only two switch elements, a fifth switch Tr5 and a sixth switch Tr6. This auxiliary circuit SC can perform soft switching in both the first leg U1 and the second leg U2. This allows the auxiliary circuit SC, the drive circuit for the auxiliary circuit SC, and the control signal for the auxiliary circuit SC to be simplified, thereby achieving reduced circuit costs and area.

The above-mentioned Example 3 is an example of soft switching operation in the case where the first leg U1 and the second leg U2 output voltages of the same phase, and current flows from the motor 20 to the first connection point P1 and the second connection point P2, respectively. However, as already mentioned, when controlling the switching of the number of poles while the motor 20 is rotating, the output voltage of the first leg U1 and the output voltage of the second leg U2 are not simply in phase or in opposite phase, but the first leg U1 and the second leg U2 have different duties. As will be explained in the following Example 4, even in the above case, the switching loss can be minimized by operating the auxiliary circuit SC in synchronization with one of the first leg U1 and the second leg U2.

Example 4
FIG. 34 is a timing chart showing the on/off timing of the first switch Tr1 to the fourth switch Tr4 and the sixth switch Tr6 when a current flows from the motor 20 to the first connection point P1 and the second connection point P2, respectively, and the on period of the second switch Tr2 is shorter than the on period of the fourth switch Tr4 within the PWM period TP.

In this way, when a current flows from the motor 20 to each of the first connection point P1 and the second connection point P2, and the length of the on-period of the second switch Tr2 and the length of the on-period of the fourth switch Tr4 are different within the PWM period TP, the control unit 13 turns on the other switch at the fourth timing when one of the second switch Tr2 and the fourth switch Tr4 is on and the other is off, and performs the second operation before the fourth timing within the PWM period TP.

In the example shown in FIG. 34, when the fourth switch Tr4 is on and the second switch Tr2 is off, the control unit 13 turns on the sixth switch Tr6 for a second time before the fourth timing at which the second switch Tr2 is turned on.

35 is a diagram showing the state of each switch and the direction of current during the first period T61 in the PWM cycle TP shown in FIG. 34. As shown in FIG. 35, during the first period T61, the first switch Tr1 and the fourth switch Tr4 are on, the second switch Tr2 and the third switch Tr3 are off, and the sixth switch Tr6 is off. During the first period T61, current flows from the motor 20 to the first connection point P1 and the second connection point P2, respectively, and an upward current flows through the first switch Tr1 and a downward current flows through the fourth switch Tr4. During the first period T61, the potential of the first connection point P1 is approximately equal to the positive electrode potential of the DC power supply 30, and the potential of the second connection point P2 is approximately equal to the negative electrode potential of the DC power supply 30.

FIG. 36 is a diagram showing the state of each switch and the direction of the current during the second period T62 in the PWM cycle TP shown in FIG. 34. As shown in FIG. 36, during the second period T62, the first switch Tr1 and the fourth switch Tr4 are on, the second switch Tr2 and the third switch Tr3 are off, and the sixth switch Tr6 is on. During the second period T62, when the sixth switch Tr6 is turned on, the potential of the fourth connection point P4 becomes approximately equal to the negative electrode potential of the DC power supply 30, and a rightward current flows through the third inductor L3. During the second period T62, when the rightward current flowing through the third inductor L3 becomes larger than the current flowing from the motor 20 toward the first connection point P1, a downward current flows through the first switch Tr1. The second period T62 corresponds to the second time during which the sixth switch Tr6 is turned on.

FIG. 37 is a diagram showing the state of each switch and the direction of the current during the third period T63 in the PWM cycle TP shown in FIG. 34. As shown in FIG. 37, during the third period T63, the first switch Tr1 and the fourth switch Tr4 are on, the second switch Tr2 and the third switch Tr3 are off, and the sixth switch Tr6 is off. When the sixth switch Tr6 is turned off during the third period T63, the rightward current flowing through the third inductor L3 is commutated from the sixth switch Tr6 to the sixth rectifier element D6, and an upward current flows through the sixth rectifier element D6. During the third period T63, the potential of the fourth connection point P4 is approximately equal to the positive electrode potential of the DC power supply 30.

FIG. 38 is a diagram showing the state of each switch and the direction of the current during the fourth period T64 in the PWM cycle TP shown in FIG. 34. As shown in FIG. 38, during the fourth period T64, the fourth switch Tr4 is on, the first switch Tr1, the second switch Tr2, and the third switch Tr3 are off, and the sixth switch Tr6 is off. When the first switch Tr1 is turned off during the fourth period T64, the current flowing through the sixth rectifier element D6 is commutated from the first switch Tr1 to the second switch Tr2, and an upward current flows through the body diode of the second switch Tr2. During the fourth period T64, the potential of the first connection point P1 is approximately equal to the negative electrode potential of the DC power supply 30, so that the voltage across the second switch Tr2 is approximately zero. Note that during the fourth period T64, a reverse voltage is applied to the third inductor L3, so the rightward current flowing through the third inductor L3 gradually decreases.

Fig. 39 is a diagram showing the state of each switch and the direction of current during a fifth period T65 in the PWM cycle TP shown in Fig. 34. As shown in Fig. 39, during the fifth period T65, the first switch Tr1 and the third switch Tr3 are off, the second switch Tr2 and the fourth switch Tr4 are on, and the sixth switch Tr6 is off. During the fifth period T65, as the current flowing through the third inductor L3 decreases, the upward current flowing through the second switch Tr2 also decreases. Then, when the current flowing through the third inductor L3 becomes smaller than the current flowing from the motor 20 toward the first connection point P1, a downward current flows through the second switch Tr2.
When the current flowing through the third inductor L3 becomes zero, the current flowing downward through the second switch Tr2 and the current flowing from the motor 20 toward the first connection point P1 become equal.

As described above, in a PWM period TP, when the fourth switch Tr4 is on and the second switch Tr2 is off, the control unit 13 turns on the sixth switch Tr6 for the second time before the fourth timing at which the second switch Tr2 is turned on. This causes the voltage across the second switch Tr2 to be nearly zero before the second switch Tr2 is turned on. Therefore, when a current flows from the motor 20 to each of the first connection point P1 and the second connection point P2, and the on period of the second switch Tr2 is shorter than the on period of the fourth switch Tr4 within the PWM period TP, the control unit 13 performs the above-mentioned soft switching operation, thereby realizing soft switching of the second switch Tr2 and reducing the switching loss of the second switch Tr2.

FIG. 40 is a timing chart showing the on/off timing of the first switch Tr1 to the fourth switch Tr4 and the sixth switch Tr6 when current flows from the motor 20 to the first connection point P1 and the second connection point P2, and the length of the on period of the second switch Tr2 and the length of the on period of the fourth switch Tr4 are different within a PWM period TP, and the center of the on period of the second switch Tr2 and the center of the on period of the fourth switch Tr4 are shifted from each other by a half PWM period.

In the example shown in FIG. 40, in a period T71 within the PWM cycle TP, when the fourth switch Tr4 is on and the second switch Tr2 is off, the control unit 13 turns on the sixth switch Tr6 for a second time before turning on the second switch Tr2. Also, in the example shown in FIG. 40, in a period T72 within the PWM cycle TP, when the second switch Tr2 is on and the fourth switch Tr4 is off, the control unit 13 turns on the fourth switch Tr4 for a second time before turning on the fourth switch Tr4.

As a result, the voltage across the second switch Tr2 becomes almost zero before the second switch Tr2 is turned on, and the voltage across the fourth switch Tr4 becomes almost zero before the fourth switch Tr4 is turned on. Therefore, when a current flows from the motor 20 to each of the first connection point P1 and the second connection point P2, and the length of the on-period of the second switch Tr2 and the length of the on-period of the fourth switch Tr4 are different within the PWM period TP, and the center of the on-period of the second switch Tr2 and the center of the on-period of the fourth switch Tr4 are shifted from each other by a half PWM period, the control unit 13 performs the above-mentioned soft switching operation, thereby realizing soft switching of the second switch Tr2 and the fourth switch Tr4, and reducing the switching loss of the second switch Tr2 and the fourth switch Tr4.

Example 5
Fig. 41 is a timing chart showing the on/off timing of the first switch Tr1 to the sixth switch Tr6 when a current flows from the first connection point P1 to the motor 20 and also flows from the motor 20 to the second connection point P2. Example 5 is an example of a soft switching operation when the first leg U1 and the second leg U2 output voltages of opposite phases, a current flows from the first connection point P1 to the motor 20 and also flows from the motor 20 to the second connection point P2. Fig. 41 also shows changes in the currents of the first inductor L1 and the fourth inductor L4, the currents of the first switch Tr1 and the fourth switch Tr4, and the voltages across the first switch Tr1 and the fourth switch Tr4.

In FIG. 41, I_L1 indicates the current in the first inductor L1, and I_L4 indicates the current in the fourth inductor L4. I_Tr1 indicates the current in the first switch Tr1, and I_Tr4 indicates the current in the fourth switch Tr4. V_Tr1 indicates the voltage across the first switch Tr1, and V_Tr4 indicates the voltage across the fourth switch Tr4.

As shown in FIG. 41, when a current flows from the first connection point P1 to the motor 20 and a current flows from the motor 20 to the second connection point P2, the control unit 13 turns on both the first switch Tr1 and the fourth switch Tr4 at the fifth timing, and simultaneously performs the first operation and the second operation before the fifth timing within the PWM period TP.

In other words, when a current flows from the first connection point P1 toward the motor 20 and from the motor 20 toward the second connection point P2, the control unit 13 simultaneously performs a first operation of turning on the fifth switch Tr5 for a first time and a second operation of turning on the sixth switch Tr6 for a second time before simultaneously turning on the first switch Tr1 and the fourth switch Tr4 within the PWM period TP. In this case, the first time is equal to the second time.

FIG. 42 is a diagram showing the state of each switch and the direction of the current during the first period T81 in the PWM cycle TP shown in FIG. 41. As shown in FIG. 42, during the first period T81, the first switch Tr1 and the fourth switch Tr4 are off, the second switch Tr2 and the third switch Tr3 are on, and the fifth switch Tr5 and the sixth switch Tr6 are off. During the first period T81, an upward current flows through the second switch Tr2, and a current flows from the first connection point P1 toward the motor 20. Also, during the first period T81, a current flows from the motor 20 toward the second connection point P2, and an upward current flows through the third switch Tr3. During the first period T81, the potential of the first connection point P1 is approximately equal to the negative electrode potential of the DC power supply 30, and the potential of the second connection point P2 is approximately equal to the positive electrode potential of the DC power supply 30.

FIG. 43 is a diagram showing the state of each switch and the direction of the current during the second period T82 in the PWM cycle TP shown in FIG. 41. As shown in FIG. 43, during the second period T82, the first switch Tr1 and the fourth switch Tr4 are off, the second switch Tr2 and the third switch Tr3 are on, and the fifth switch Tr5 and the sixth switch Tr6 are on. During the second period T82, when the fifth switch Tr5 and the sixth switch Tr6 are on, the potential of the third connection point P3 becomes approximately equal to the positive electrode potential of the DC power supply 30, and the potential of the fourth connection point P4 becomes approximately equal to the negative electrode potential of the DC power supply 30, so that a rightward current flows through the first inductor L1 and the fourth inductor L4. During the second period T82, when the rightward current flowing through the first inductor L1 becomes larger than the current flowing from the first connection point P1 toward the motor 20, a downward current flows through the second switch Tr2. In addition, in the second period T82, when the rightward current flowing through the fourth inductor L4 becomes larger than the current flowing from the motor 20 toward the second connection point P2, a downward current flows through the third switch Tr3. The second period T82 corresponds to the first time during which the fifth switch Tr5 is turned on, and corresponds to the second time during which the sixth switch Tr6 is turned on.

FIG. 44 is a diagram showing the state of each switch and the direction of the current during the third period T83 in the PWM cycle TP shown in FIG. 41. As shown in FIG. 44, during the third period T83, the first switch Tr1 and the fourth switch Tr4 are off, the second switch Tr2 and the third switch Tr3 are on, and the fifth switch Tr5 and the sixth switch Tr6 are off. During the third period T83, when the fifth switch Tr5 is turned off, the rightward current flowing through the first inductor L1 is commutated from the fifth switch Tr5 to the fifth rectifier element D5, and an upward current flows through the fifth rectifier element D5. Also, during the third period T83, when the sixth switch Tr6 is turned off, the rightward current flowing through the fourth inductor L4 is commutated from the sixth switch Tr6 to the sixth rectifier element D6, and an upward current flows through the sixth rectifier element D6. In the third period T83, the potential of the third connection point P3 is approximately equal to the negative electrode potential of the DC power supply 30, and the potential of the fourth connection point P4 is approximately equal to the positive electrode potential of the DC power supply 30.

FIG. 45 is a diagram showing the state of each switch and the direction of current during the fourth period T84 in the PWM cycle TP shown in FIG. 41. As shown in FIG. 45, during the fourth period T84, the first switch Tr1 and the fourth switch Tr4 are off, the second switch Tr2 and the third switch Tr3 are off, and the fifth switch Tr5 and the sixth switch Tr6 are off. When the second switch Tr2 is turned off during the fourth period T84, the current flowing through the first inductor L1 is commutated from the second switch Tr2 to the first switch Tr1, and an upward current flows through the body diode of the first switch Tr1. Also, during the fourth period T84, when the third switch Tr3 is turned off, the current flowing through the fourth inductor L4 is commutated from the third switch Tr3 to the fourth switch Tr4, and an upward current flows through the body diode of the fourth switch Tr4. In the fourth period T84, the potential of the first connection point P1 is approximately equal to the positive electrode potential of the DC power supply 30, and the potential of the second connection point P2 is approximately equal to the negative electrode potential of the DC power supply 30, so that the voltages across the first switch Tr1 and the fourth switch Tr4 are approximately zero. Note that in the fourth period T84, a reverse voltage is applied to the first inductor L1 and the fourth inductor L4, so the rightward current flowing through the first inductor L1 and the fourth inductor L4 gradually decreases.

46 is a diagram showing the state of each switch and the direction of current in the fifth period T85 in the PWM cycle TP shown in FIG. 41. As shown in FIG. 46, in the fifth period T85, the first switch Tr1 and the fourth switch Tr4 are on, the second switch Tr2 and the third switch Tr3 are off, and the fifth switch Tr5 and the sixth switch Tr6 are off. In the fifth period T85, as the current flowing through the first inductor L1 and the fourth inductor L4 decreases, the upward current flowing through the first switch Tr1 and the fourth switch Tr4 also decreases. Then, when the current flowing through the first inductor L1 becomes smaller than the current flowing from the first connection point P1 to the motor 20, a downward current flows through the first switch Tr1. Also, when the current flowing through the fourth inductor L4 becomes smaller than the current flowing from the motor 20 to the second connection point P2, a downward current flows through the fourth switch Tr4.
When the current flowing through the first inductor L1 becomes zero, the current flowing downward through the first switch Tr1 matches the current flowing from the first connection point P1 toward the motor 20. When the current flowing through the fourth inductor L4 becomes zero, the current flowing downward through the fourth switch Tr4 matches the current flowing from the motor 20 toward the second connection point P2.

As described above, when a current flows from the first connection point P1 to the motor 20 and a current flows from the motor 20 to the second connection point P2, the control unit 13 simultaneously performs the first operation and the second operation.
That is, during a ninth period from the ON timing of the second switch Tr2 and the third switch Tr3 to the ON timing of the fifth switch Tr5 and the sixth switch Tr6, the control unit 13 turns off the first switch Tr1 and the fourth switch Tr4, turns on the second switch Tr2 and the third switch Tr3, and turns off the fifth switch Tr5 and the sixth switch Tr6. The first period T81 corresponds to the ninth period.
Then, in a tenth period which is a period following the ninth period and corresponds to the first time, the control unit 13 turns off the first switch Tr1 and the fourth switch Tr4, turns on the second switch Tr2 and the third switch Tr3, and turns on the fifth switch Tr5 and the sixth switch Tr6. The second period T82 corresponds to the tenth period.
Then, in an eleventh period after the tenth period, the control unit 13 turns off the first switch Tr1 and the fourth switch Tr4, turns on the second switch Tr2 and the third switch Tr3, and turns off the fifth switch Tr5 and the sixth switch Tr6. The third period T83 corresponds to the eleventh period.
Furthermore, during a twelfth period from the end timing of the eleventh period to the on timing of the first switch Tr1 and the fourth switch Tr4, the control unit 13 turns off the first switch Tr1 and the fourth switch Tr4, turns off the second switch Tr2 and the third switch Tr3, and turns off the fifth switch Tr5 and the sixth switch Tr6. The fourth period T84 corresponds to the twelfth period.

As described above, when a current flows from the first connection point P1 to the motor 20 and from the motor 20 to the second connection point P2, the control unit 13 simultaneously performs a first operation of turning on the fifth switch Tr5 for a first time and a second operation of turning on the sixth switch Tr6 for a second time before simultaneously turning on the first switch Tr1 and the fourth switch Tr4 within the PWM period TP. As a result, the voltages across the first switch Tr1 and the fourth switch Tr4 become almost zero before the first switch Tr1 and the fourth switch Tr4 are simultaneously turned on. Therefore, when a current flows from the first connection point P1 to the motor 20 and from the motor 20 to the second connection point P2, the control unit 13 performs the above-mentioned soft switching operation, thereby realizing soft switching of the first switch Tr1 and the fourth switch Tr4 and reducing the switching loss of the first switch Tr1 and the fourth switch Tr4.
In this manner, by synchronizing the turn-on timing of the first switch Tr1 and the fourth switch Tr4, soft switching can be achieved in both the first leg U1 and the second leg U2.
The auxiliary circuit SC includes only two switch elements, a fifth switch Tr5 and a sixth switch Tr6. This auxiliary circuit SC can perform soft switching in both the first leg U1 and the second leg U2. This allows the auxiliary circuit SC, the drive circuit for the auxiliary circuit SC, and the control signal for the auxiliary circuit SC to be simplified, thereby achieving reduced circuit costs and area.

In addition, when a current flows from the second connection point P2 to the motor 20 and from the motor 20 to the first connection point P1, in the explanation of the fifth embodiment, the first leg U1, the first connection point P1, and the third connection point P3 should be read as the second leg U2, the second connection point P2, and the fourth connection point P4, respectively, the first switch Tr1 and the fourth switch Tr4 should be read as the second switch Tr2 and the third switch Tr3, respectively, and the first inductor L1 and the fourth inductor L4 should be read as the second inductor L2 and the third inductor L3, respectively.

Example 5 is an example of soft switching operation in which the first leg U1 and the second leg U2 output voltages of opposite phases, a current flows from the first connection point P1 toward the motor 20, and a current flows from the motor 20 toward the second connection point P2. As already mentioned, when controlling the number of poles to be switched while the motor 20 is rotating, the output voltage of the first leg U1 and the output voltage of the second leg U2 are not simply in phase or in opposite phase, but the first leg U1 and the second leg U2 have different duties. However, as will be explained in Example 6 below, even in this case, the switching loss can be minimized by operating the auxiliary circuit SC in synchronization with one of the first leg U1 and the second leg U2.

Example 6
FIG. 47 is a timing chart showing the on/off timing of the first switch Tr1 to the fourth switch Tr4 and the fifth switch Tr5 when a current flows from the first connection point P1 to the motor 20 and a current flows from the motor 20 to the second connection point P2 and when the on period of the first switch Tr1 is longer than the on period of the fourth switch Tr4 within the PWM period TP.

In this way, when a current flows from the first connection point P1 to the motor 20 and a current flows from the motor 20 to the second connection point P2, and the length of the on period of the first switch Tr1 differs from the length of the on period of the fourth switch Tr4 within the PWM period TP, the control unit 13 turns on the first switch Tr1 at the sixth timing when the first switch Tr1 is off and the fourth switch Tr4 is off, and performs the first operation before the sixth timing within the PWM period TP.

In the example shown in FIG. 47, when the first switch Tr1 is off and the fourth switch Tr4 is off within the PWM period TP, the control unit 13 turns on the fifth switch Tr5 for the first time before the sixth timing at which the first switch Tr1 is turned on.

FIG. 48 is a diagram showing the state of each switch and the direction of the current during the first period T91 in the PWM cycle TP shown in FIG. 47. As shown in FIG. 48, during the first period T91, the first switch Tr1 and the fourth switch Tr4 are off, the second switch Tr2 and the third switch Tr3 are on, and the fifth switch Tr5 is off. During the first period T91, an upward current flows through the second switch Tr2, and a current flows from the first connection point P1 toward the motor 20. Also, during the first period T91, a current flows from the motor 20 toward the second connection point P2, and an upward current flows through the third switch Tr3. During the first period T91, the potential of the first connection point P1 is approximately equal to the negative electrode potential of the DC power supply 30, and the potential of the second connection point P2 is approximately equal to the positive electrode potential of the DC power supply 30.

FIG. 49 is a diagram showing the state of each switch and the direction of the current during the second period T92 in the PWM cycle TP shown in FIG. 47. As shown in FIG. 49, during the second period T92, the first switch Tr1 and the fourth switch Tr4 are off, the second switch Tr2 and the third switch Tr3 are on, and the fifth switch Tr5 is on. During the second period T92, when the fifth switch Tr5 is turned on, the potential of the third connection point P3 becomes approximately equal to the positive electrode potential of the DC power supply 30, and a rightward current flows through the first inductor L1. During the second period T92, when the rightward current flowing through the first inductor L1 becomes larger than the current flowing from the first connection point P1 toward the motor 20, a downward current flows through the second switch Tr2. The second period T92 corresponds to the first time during which the fifth switch Tr5 is turned on.

FIG. 50 is a diagram showing the state of each switch and the direction of the current during the third period T93 in the PWM cycle TP shown in FIG. 47. As shown in FIG. 50, during the third period T93, the first switch Tr1 and the fourth switch Tr4 are off, the second switch Tr2 and the third switch Tr3 are on, and the fifth switch Tr5 is off. When the fifth switch Tr5 is turned off during the third period T93, the downward current flowing through the second switch Tr2 is commutated from the fifth switch Tr5 to the fifth rectifier element D5, and an upward current flows through the fifth rectifier element D5. During the third period T93, the potential of the third connection point P3 is approximately equal to the negative electrode potential of the DC power supply 30.

FIG. 51 is a diagram showing the state of each switch and the direction of the current during the fourth period T94 in the PWM cycle TP shown in FIG. 47. As shown in FIG. 51, during the fourth period T94, the first switch Tr1, the second switch Tr2, and the fourth switch Tr4 are off, the third switch Tr3 is on, and the fifth switch Tr5 is off. During the fourth period T94, when the second switch Tr2 is turned off, the current flowing through the first inductor L1 is commutated from the second switch Tr2 to the first switch Tr1, and an upward current flows through the body diode of the first switch Tr1. During the fourth period T94, the potential of the first connection point P1 is approximately equal to the positive electrode potential of the DC power supply 30, so that the voltage across the first switch Tr1 is approximately zero. Note that during the fourth period T94, a reverse voltage is applied to the first inductor L1, so the rightward current flowing through the first inductor L1 gradually decreases.

Fig. 52 is a diagram showing the state of each switch and the direction of current during a fifth period T95 in the PWM cycle TP shown in Fig. 47. As shown in Fig. 52, during the fifth period T95, the first switch Tr1 and the third switch Tr3 are on, the second switch Tr2 and the fourth switch Tr4 are off, and the fifth switch Tr5 is off. During the fifth period T95, as the current flowing through the first inductor L1 decreases, the upward current flowing through the first switch Tr1 also decreases. Then, when the current flowing through the first inductor L1 becomes smaller than the current flowing from the first connection point P1 toward the motor 20, a downward current flows through the first switch Tr1.
When the current flowing through the first inductor L1 becomes zero, the current flowing downward through the first switch Tr1 and the current flowing from the first connection point P1 toward the motor 20 become equal.

As described above, when a current flows from the first connection point P1 toward the motor 20 and a current flows from the motor 20 toward the second connection point P2, and the on period of the first switch Tr1 is longer than the on period of the fourth switch Tr4 within the PWM period TP, the control unit 13 turns on the fifth switch Tr5 for a first time before turning on the first switch Tr1 in a state in which the first switch Tr1 is off and the fourth switch Tr4 is off within the PWM period TP. This causes the voltage across the first switch Tr1 to become substantially zero before the first switch Tr1 is turned on. Therefore, when a current flows from the first connection point P1 to the motor 20, and a current flows from the motor 20 to the second connection point P2, and the on-period of the first switch Tr1 is longer than the on-period of the fourth switch Tr4 within the PWM period TP, the control unit 13 performs the above-mentioned soft switching operation, thereby realizing soft switching of the first switch Tr1 and reducing the switching loss of the first switch Tr1.

FIG. 53 is a timing chart showing the on/off timing of the first switch Tr1 to the fourth switch Tr4 and the sixth switch Tr6 when a current flows from the first connection point P1 to the motor 20 and a current flows from the motor 20 to the second connection point P2, and the on period of the first switch Tr1 is shorter than the on period of the fourth switch Tr4 within the PWM period TP.

In the example shown in FIG. 53, when the first switch Tr1 is off and the fourth switch Tr4 is off, the control unit 13 turns on the fourth switch Tr4 at the seventh timing, and performs the second operation before the seventh timing within the PWM period TP. In other words, when the first switch Tr1 is off and the fourth switch Tr4 is off within the PWM period TP, the control unit 13 performs the second operation of turning on the sixth switch Tr6 for a second time before turning on the fourth switch Tr4.

As a result, the voltage across the fourth switch Tr4 becomes nearly zero before the fourth switch Tr4 is turned on. Therefore, in the example shown in FIG. 53, the control unit 13 performs the above-mentioned soft switching operation, thereby realizing soft switching of the fourth switch Tr4 and reducing the switching loss of the fourth switch Tr4.

FIG. 54 is a timing chart showing the on/off timing of the first switch Tr1 to the sixth switch Tr6 when a current flows from the first connection point P1 to the motor 20 and also flows from the motor 20 to the second connection point P2, and the length of the on period of the first switch Tr1 and the length of the on period of the fourth switch Tr4 are different within a PWM period TP, and the center of the on period of the first switch Tr1 and the center of the on period of the fourth switch Tr4 are shifted from each other by a half PWM period.

In the example shown in FIG. 54, the control unit 13 performs a first operation of turning on the fifth switch Tr5 for a first time before turning on the first switch Tr1 in a state in which the third switch Tr3 is on and the first switch Tr1 is off during the PWM period TP. Also, in the example shown in FIG. 54, the control unit 13 performs a second operation of turning on the sixth switch Tr6 for a second time before turning on the fourth switch Tr4 in a state in which the first switch Tr1 is off and the fourth switch Tr4 is off during the PWM period TP.

As a result, the voltage across the first switch Tr1 becomes nearly zero before the first switch Tr1 is turned on, and the voltage across the fourth switch Tr4 becomes nearly zero before the fourth switch Tr4 is turned on. Therefore, in the example shown in FIG. 54, the control unit 13 performs the above-mentioned soft switching operation, thereby realizing soft switching of the first switch Tr1 and the fourth switch Tr4, and the switching loss of the first switch Tr1 and the fourth switch Tr4 can be reduced.

In addition, when a current flows from the second connection point P2 to the motor 20 and from the motor 20 to the first connection point P1, in the explanation of the sixth embodiment, the first leg U1, the first connection point P1, and the third connection point P3 should be read as the second leg U2, the second connection point P2, and the fourth connection point P4, respectively, the first switch Tr1 and the fourth switch Tr4 should be read as the second switch Tr2 and the third switch Tr3, respectively, and the first inductor L1 and the fourth inductor L4 should be read as the second inductor L2 and the third inductor L3, respectively.

[Modifications]
The present invention is not limited to the above-described embodiment, and the configurations described in this specification can be appropriately combined within a range not mutually contradictory.

FIG. 55 is a diagram showing a modified example of the H-bridge circuit BC and the auxiliary circuit SC. The H-bridge circuit BC may include a first capacitor connected in parallel to at least one of the first switch Tr1 to the fourth switch Tr4. In the modified example shown in FIG. 55, the first capacitor C1 is connected in parallel to the first switch Tr1, the first capacitor C2 is connected in parallel to the second switch Tr2, the first capacitor C3 is connected in parallel to the third switch Tr3, and the first capacitor C4 is connected in parallel to the fourth switch Tr4. By adopting such a configuration, the turn-off loss of the first switch Tr1 to the fourth switch Tr4 can also be reduced.

The auxiliary circuit SC may also include a second capacitor connected in parallel to at least one of the fifth switch Tr5 and the sixth switch Tr5. In the modified example shown in FIG. 55, the second capacitor C5 is connected in parallel to the fifth switch Tr5, and the second capacitor C6 is connected in parallel to the sixth switch Tr6. By adopting such a configuration, the turn-off loss of the fifth switch Tr5 and the sixth switch Tr6 can also be reduced. A capacitor may be connected in parallel to at least one of the fifth rectifier element D5 and the sixth rectifier element D6.

In the above embodiment, the motor 20 is illustrated as having a configuration in which the neutral points of the first U-phase coil 23u, the first V-phase coil 23v, and the first W-phase coil 23w are electrically separated from the neutral points of the second U-phase coil 24u, the second V-phase coil 24v, and the second W-phase coil 24w. The present invention is not limited to this, and a motor may be used in which the neutral points of the first U-phase coil 23u, the first V-phase coil 23v, and the first W-phase coil 23w are electrically connected to the neutral points of the second U-phase coil 24u, the second V-phase coil 24v, and the second W-phase coil 24w.

The present technology can be configured as follows: (1) A motor having two N-phase terminal groups (N is an integer of 3 or more), including an H-bridge circuit corresponding to each phase of the motor, an auxiliary circuit corresponding to at least one of the H-bridge circuits, and a control unit that controls the H-bridge circuit and the auxiliary circuit, the H-bridge circuit including a first leg including a first switch connected between a positive electrode of a power source and a first connection point, and a second switch connected between a negative electrode of the power source and the first connection point, a second leg including a third switch connected between the positive electrode and the second connection point, and a fourth switch connected between the negative electrode and the second connection point, the auxiliary circuit including a first rectifying element and a first inductor connected in series between the first connection point and the third connection point, and a second rectifying element and a second inductor connected in series between the second connection point and the third connection point. a third rectifier element and a third inductor connected in series between the first connection point and a fourth connection point, a fourth rectifier element and a fourth inductor connected in series between the second connection point and the fourth connection point, a fifth switch connected between the positive electrode and the third connection point, a fifth rectifier element having a negative terminal connected to the third connection point and a positive terminal connected to the negative electrode, a sixth rectifier element having a negative terminal connected to the positive electrode and a positive terminal connected to the fourth connection point, and a sixth switch connected between the negative electrode and the fourth connection point, wherein the positive terminal of the first rectifier element and the positive terminal of the second rectifier element are located on the third connection point side, and the negative terminal of the third rectifier element and the negative terminal of the fourth rectifier element are located on the fourth connection point side. (2) The power conversion device according to (1), wherein the control unit performs at least one of a first operation of turning on the fifth switch for a first time before turning on at least one of the first switch and the third switch in one control period of pulse width modulation and a second operation of turning on the sixth switch for a second time before turning on at least one of the second switch and the fourth switch in one control period. (3) The power conversion device according to (2), wherein, when a current flows from the first connection point to the motor, the first operation is an operation of turning on the fifth switch for the first time before turning on the first switch in one control period, and when a current flows from the second connection point to the motor, the first operation is an operation of turning on the fifth switch for the first time before turning on the third switch in one control period. (4) The power conversion device according to (2), wherein, when a current flows from the motor to the first connection point, the second operation is an operation of turning on the sixth switch for the second time before turning on the second switch in the one control period, and when a current flows from the motor to the second connection point, the second operation is an operation of turning on the sixth switch for the second time before turning on the fourth switch in the one control period. (5) The power conversion device according to (3), wherein, when a current flows from each of the first connection point and the second connection point to the motor, the control unit turns on both the first switch and the third switch at a first timing, and performs the first operation before the first timing in the one control period. (6) The power conversion device described in (5), wherein, when the control unit performs the first operation, in a first period from an on-timing of the second switch and the fourth switch to an on-timing of the fifth switch, the control unit turns off the first switch and the third switch, turns on the second switch and the fourth switch, and turns off the fifth switch; in a second period that is a period after the first period and corresponds to the first time, the control unit turns off the first switch and the third switch, turns on the second switch and the fourth switch, and turns on the fifth switch; in a third period after the second period, the control unit turns off the first switch and the third switch, turns on the second switch and the fourth switch, and turns off the fifth switch; and in a fourth period from an end timing of the third period to the on-timing of the first switch and the third switch, the control unit turns off the second switch and the fourth switch, and turns off the fifth switch. (7) The power conversion device according to (3), wherein, when a current flows from both the first connection point and the second connection point toward the motor, in a state in which one of the first switch and the third switch is on and the other switch is off, the control unit turns on the other switch at a second timing and performs the first operation before the second timing within the one control period. (8) The power conversion device according to (4), wherein, when a current flows from the motor toward each of the first connection point and the second connection point, the control unit turns on both the second switch and the fourth switch at a third timing and performs the second operation before the third timing within the one control period. (9) The power conversion device described in (8), wherein, when the control unit performs the second operation, in a fifth period from an on-timing of the first switch and the third switch to an on-timing of the sixth switch, it turns on the first switch and the third switch, turns off the second switch and the fourth switch, and turns off the sixth switch; in a sixth period which is a period after the fifth period and corresponds to the second time, it turns on the first switch and the third switch, turns off the second switch and the fourth switch, and turns on the sixth switch; in a seventh period after the sixth period, it turns on the first switch and the third switch, turns off the second switch and the fourth switch, and turns off the sixth switch; and in an eighth period from an end timing of the seventh period to an on-timing of the second switch and the fourth switch, it turns off the first switch and the third switch, turns off the second switch and the fourth switch, and turns off the sixth switch. (10) The power conversion device according to (4), wherein, when a current flows from the motor to each of the first connection point and the second connection point, in a state in which one of the second switch and the fourth switch is on and the other switch is off, the control unit turns on the other switch at a fourth timing, and performs the second operation before the fourth timing within the one control period. (11) The power conversion device according to (2), wherein, when a current flows from the first connection point to the motor and a current flows from the motor to the second connection point, the control unit turns on both the first switch and the fourth switch at a fifth timing, and performs the first operation and the second operation simultaneously before the fifth timing within the one control period, and the first time is equal to the second time. (12) The power conversion device according to (11), wherein, when the first operation and the second operation are performed simultaneously, the control unit turns off the first switch and the fourth switch, turns on the second switch and the third switch, and turns off the fifth switch and the sixth switch in a ninth period from an on timing of the second switch and the third switch to an on timing of the fifth switch and the sixth switch; turns off the first switch and the fourth switch, turns on the second switch and the third switch, and turns on the fifth switch and the sixth switch in a tenth period that is a period after the ninth period and corresponds to the first time; turns off the first switch and the fourth switch, turns on the second switch and the third switch, and turns off the fifth switch and the sixth switch in an eleventh period after the tenth period; and turns off the first switch and the fourth switch, turns on the second switch and the third switch, and turns off the fifth switch and the sixth switch in a twelfth period from an end timing of the eleventh period to an on timing of the first switch and the fourth switch. (13) The power conversion device according to (2), wherein, when a current flows from the first connection point to the motor and a current flows from the motor to the second connection point, the control unit turns on the first switch at a sixth timing in a state where the first switch is off and the fourth switch is off, and performs the first operation before the sixth timing within the one control period. (14) The power conversion device according to (2), wherein, when a current flows from the first connection point to the motor and a current flows from the motor to the second connection point, the control unit turns on the fourth switch at a seventh timing in a state where the first switch is off and the fourth switch is off, and performs the second operation before the seventh timing within the one control period. (15) The power conversion device according to any one of (1) to (14), wherein the control unit has a first mode in which the first leg and the second leg output voltages of the same phase, and a second mode in which the first leg and the second leg output voltages of opposite phases. (16) The power conversion device according to any one of (1) to (15), in which the H-bridge circuit includes a first capacitor connected in parallel to at least one of the first switch to the fourth switch. (17) The power conversion device according to any one of (1) to (16), in which the auxiliary circuit includes a second capacitor connected in parallel to at least one of the fifth switch and the sixth switch. (18) A motor module including a motor having two N-phase terminal groups (N is an integer of 3 or more) and the power conversion device according to any one of (1) to (17).

Claims

an H-bridge circuit corresponding to each phase of a motor having two N-phase terminal groups (N is an integer of 3 or more);
an auxiliary circuit corresponding to at least one of the H-bridge circuits;
A control unit that controls the H-bridge circuit and the auxiliary circuit;
Equipped with
The H-bridge circuit includes:
a first leg including a first switch connected between a positive electrode of a power source and a first node, and a second switch connected between a negative electrode of the power source and the first node;
a second leg including a third switch connected between the positive electrode and a second connection point and a fourth switch connected between the negative electrode and the second connection point;
Equipped with
The auxiliary circuit includes:
a first rectifying element and a first inductor connected in series between the first connection point and a third connection point;
a second rectifying element and a second inductor connected in series between the second connection point and the third connection point;
a third rectifying element and a third inductor connected in series between the first connection point and the fourth connection point;
a fourth rectifying element and a fourth inductor connected in series between the second connection point and the fourth connection point;
a fifth switch connected between the positive electrode and the third node;
a fifth rectifier element having a negative terminal connected to the third connection point and a positive terminal connected to the negative electrode;
a sixth rectifier element having a negative electrode terminal connected to the positive electrode and a positive electrode terminal connected to the fourth connection point;
a sixth switch connected between the negative electrode and the fourth connection point;
Equipped with
a positive terminal of the first rectifying element and a positive terminal of the second rectifying element are located on the third connection point side;
The negative terminal of the third rectifier element and the negative terminal of the fourth rectifier element are located on the fourth connection point side.
Power conversion equipment.
The power conversion device according to claim 1, wherein the control unit performs at least one of a first operation of turning on the fifth switch for a first time before turning on at least one of the first switch and the third switch in one control period of pulse width modulation, and a second operation of turning on the sixth switch for a second time before turning on at least one of the second switch and the fourth switch in one control period.
when a current flows from the first connection point to the motor, the first action is an action of turning on the fifth switch for the first time before turning on the first switch within one control period,
3. The power conversion device according to claim 2, wherein when a current flows from the second connection point toward the motor, the first operation is an operation of turning on the fifth switch for the first time before turning on the third switch within one control period.
when a current flows from the motor to the first connection point, the second operation is an operation of turning on the sixth switch for the second period before turning on the second switch within one control period,
3. The power conversion device according to claim 2, wherein when a current flows from the motor to the second connection point, the second operation is an operation of turning on the sixth switch for the second period before turning on the fourth switch within the one control period.
The power conversion device according to claim 3, wherein the control unit turns on both the first switch and the third switch at a first timing when a current flows from each of the first connection point and the second connection point toward the motor, and performs the first operation before the first timing within one control period.
When the control unit performs the first operation,
during a first period from an on-timing of the second switch and the fourth switch to an on-timing of the fifth switch, turning off the first switch and the third switch, turning on the second switch and the fourth switch, and turning off the fifth switch;
during a second period following the first period and corresponding to the first time, turning off the first switch and the third switch, turning on the second switch and the fourth switch, and turning on the fifth switch;
In a third period after the second period, the first switch and the third switch are turned off, the second switch and the fourth switch are turned on, and the fifth switch is turned off;
during a fourth period from an end timing of the third period to an on timing of the first switch and the third switch, turning off the first switch and the third switch, turning off the second switch and the fourth switch, and turning off the fifth switch;
The power conversion device according to claim 5 ,
The power conversion device according to claim 3, wherein when current flows from both the first connection point and the second connection point toward the motor, the control unit turns on the other switch of the first switch and the third switch at a second timing in a state in which one of the first switch and the third switch is on and the other switch is off, and performs the first operation before the second timing within one control period.
The power conversion device according to claim 4, wherein the control unit turns on both the second switch and the fourth switch at a third timing when a current flows from the motor to each of the first connection point and the second connection point, and performs the second operation before the third timing within one control period.
When the control unit performs the second operation,
during a fifth period from an on-timing of the first switch and the third switch to an on-timing of the sixth switch, turning on the first switch and the third switch, turning off the second switch and the fourth switch, and turning off the sixth switch;
in a sixth period that is a period after the fifth period and corresponds to the second time, turning on the first switch and the third switch, turning off the second switch and the fourth switch, and turning on the sixth switch;
In a seventh period after the sixth period, the first switch and the third switch are turned on, the second switch and the fourth switch are turned off, and the sixth switch is turned off;
during an eighth period from an end timing of the seventh period to an on timing of the second switch and the fourth switch, turning off the first switch and the third switch, turning off the second switch and the fourth switch, and turning off the sixth switch;
The power conversion device according to claim 8 ,
The power conversion device according to claim 4, wherein when a current flows from the motor to each of the first connection point and the second connection point, the control unit turns on the other switch at a fourth timing when one of the second switch and the fourth switch is on and the other switch is off, and performs the second operation before the fourth timing within one control period.
the control unit turns on both the first switch and the fourth switch at a fifth timing when a current flows from the first connection point to the motor and a current flows from the motor to the second connection point, and performs the first operation and the second operation simultaneously before the fifth timing within one control period;
The first time is equal to the second time.
The power conversion device according to claim 2 .
When the control unit performs the first operation and the second operation simultaneously,
during a ninth period from an on-timing of the second switch and the third switch to an on-timing of the fifth switch and the sixth switch, turning off the first switch and the fourth switch, turning on the second switch and the third switch, and turning off the fifth switch and the sixth switch;
in a tenth period which is a period following the ninth period and corresponds to the first time, turning off the first switch and the fourth switch, turning on the second switch and the third switch, and turning on the fifth switch and the sixth switch;
In an eleventh period after the tenth period, the first switch and the fourth switch are turned off, the second switch and the third switch are turned on, and the fifth switch and the sixth switch are turned off;
during a twelfth period from an end timing of the eleventh period to an on timing of the first switch and the fourth switch, turning off the first switch and the fourth switch, turning off the second switch and the third switch, and turning off the fifth switch and the sixth switch;
The power converter according to claim 11 ,
The power conversion device according to claim 2, wherein, when a current flows from the first connection point to the motor and a current flows from the motor to the second connection point, the control unit turns on the first switch at a sixth timing in a state in which the first switch is off and the fourth switch is off, and performs the first operation before the sixth timing within one control period.
The power conversion device according to claim 2, wherein, when a current flows from the first connection point to the motor and a current flows from the motor to the second connection point, the control unit turns on the fourth switch at a seventh timing in a state in which the first switch is off and the fourth switch is off, and performs the second operation before the seventh timing within one control period.
The power conversion device according to any one of claims 1 to 14, wherein the control unit has a first mode in which the first leg and the second leg output voltages of the same phase, and a second mode in which the first leg and the second leg output voltages of opposite phases.
The power conversion device according to any one of claims 1 to 14, wherein the H-bridge circuit includes a first capacitor connected in parallel to at least one of the first switch to the fourth switch.
The power conversion device of claim 16, wherein the auxiliary circuit includes a second capacitor connected in parallel to at least one of the fifth switch and the sixth switch.
A motor having two N-phase terminal groups (N is an integer of 3 or more);
The power conversion device according to any one of claims 1 to 14,
A motor module comprising: