Power converter

Abstract

The problem of reducing radiation noise is solved. A power converter (100) includes a power conversion circuit (11), a switch (8), a resonant capacitor (9), a resonant inductor (L1), a regenerative capacitor (15), and a controller (50). The switch (8) comprises a third switching element (6) and a fourth switching element (7). A controller (50) controls the first switching element (1), the second switching element (2), the third switching element (6) and the fourth switching element (7). The controller (50) enables at least a portion of a high-level period of a control signal for the switch (8) to overlap with a dead time period. The controller (50) causes the third switching element (6) to maintain a state immediately prior to a ringing period during the ringing period in which a voltage across the third switching element (6) rings.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to power converters. More particularly, the present disclosure relates to power converters having the ability to convert DC power to AC power. BACKGROUND

[0002] Patent Document 1 discloses a power conversion system.

[0003] The power conversion system (power converter) of Patent Document 1 includes a switching component including a pair of main switching elements (a first switching element and a second switching element) connected in series with each other, and diodes (a first diode and a second diode) connected in anti-parallel to each of the main switching elements. The power conversion system further includes an auxiliary circuit for performing soft switching of each of the main switching elements, and a controller. The auxiliary circuit includes two capacitors, a coil (resonant inductor), and an auxiliary switch. The controller generates control signals for PWM control of each of the main switching elements, and outputs the control signals to gates of the main switching elements, respectively. In addition, the controller also generates control signals for controlling ON / OFF states of the auxiliary switch, and outputs the control signals to a gate of the auxiliary switch.

[0004] In a power converter, radiated noise is increased in some cases.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2010-233306 SUMMARY

[0008] An object of the present disclosure is to provide a power converter having the ability to reduce radiated noise.

[0009] A power converter according to an aspect of the present disclosure includes a first DC terminal and a second DC terminal, a power conversion circuit, a switch, a resonance capacitor, a resonance inductor, a regeneration capacitor, and a controller. The power conversion circuit includes a switching circuit. The switching circuit includes a first switching element and a second switching element connected in series to each other, a first diode connected in antiparallel to the first switching element, and a second diode connected in antiparallel to the second switching element. In the switching circuit, the first switching element is connected to the first DC terminal, and the second switching element is connected to the second DC terminal. The switch has a first terminal and a second terminal. The first terminal of the switch is connected to a connection node between the first switching element and the second switching element. The resonance capacitor is connected between the first terminal of the switch and the second DC terminal. The resonance inductor is connected to the second terminal of the switch. The regeneration capacitor is connected between the resonance inductor and the second DC terminal. The controller controls the first switching element, the second switching element, and the switch. The switch includes a third switching element and a fourth switching element. The third switching element causes a current from the resonance inductor to flow therethrough when the third switching element is in an on state. The fourth switching element causes a current to flow in a direction opposite to that in the third switching element when the fourth switching element is in an on state. The controller applies a control signal whose potential alternates between a high level and a low level to each of the first switching element, the second switching element, the third switching element, and the fourth switching element. The controller sets a dead time period between a high-level period of the control signal for the first switching element and a high-level period of the control signal for the second switching element. The controller enables at least a portion of a high-level period of the control signal for the third switching element to overlap with the dead time period. The controller causes the third switching element to maintain a state immediately before a ringing period during which a voltage across the third switching element rings. BRIEF DESCRIPTION OF DRAWINGS

[0010] Figure 1 is a circuit diagram of a system including the power converter according to the first embodiment;

[0011] Figure 2 shows how duty ratios and load currents corresponding to three-phase voltage commands in AC loads connected to a plurality of AC terminals of the power converter vary with time, respectively;

[0012] Figure 3 shows a basic operation by the power converter;

[0013] Figure 4 shows a basic operation by the power converter;

[0014] Figure 5 shows the basic operation by the power converter;

[0015] Figure 6 shows how the power converter operates;

[0016] Figure 7 shows how the power converter operates;

[0017] Figure 8 is a timing chart illustrating how the power converter operates;

[0018] Figure 9 is a timing chart illustrating how the comparative example of the power converter operates;

[0019] Figure 10 is a characteristic diagram showing the measurement results of the radiation noise in the example and the comparative example of the power converter;

[0020] Figure 11 is a circuit diagram of a system including the power converter according to the second embodiment;

[0021] Figure 12 is a circuit diagram of a system including the power converter according to the third embodiment;

[0022] Figure 13 is a circuit diagram of a system including the power converter according to the fourth embodiment;

[0023] Figure 14 is a circuit diagram of a system including the power converter according to the fifth embodiment;

[0024] Figure 15 is a timing chart illustrating how the power converter operates;

[0025] Figure 16 is a circuit diagram of a system including the power converter according to the sixth embodiment;

[0026] Figure 17 is a circuit diagram of a system including the power converter according to the seventh embodiment; and

[0027] Figure 18 is a circuit diagram of a system including the power converter according to the eighth embodiment. DETAILED DESCRIPTION

[0028] (First Embodiment)

[0029] Now, the power converter 100 according to the first embodiment will be described with reference to FIGS. 1 to 3. Figures 1 to 8 The power converter 100 according to the first embodiment will be described with reference to FIGS. 1 to 3.

[0030] (1) Overall configuration of power converter

[0031] For example, such as Figure 1 As shown, the power converter 100 includes a first DC terminal 31 and a second DC terminal 32, as well as multiple (in) Figure 1 In the example shown, there are three AC terminals 41. In the power converter 100, a DC power supply E1 is connected between a first DC terminal 31 and a second DC terminal 32. An AC load RA1 is connected to multiple AC terminals 41. The AC load RA1 may be, for example, a three-phase motor. The power converter 100 converts the DC output of the DC power supply E1 into AC power and outputs that AC power to the AC load RA1. The DC power supply E1 may include, for example, a solar cell or a fuel cell. The DC power supply E1 may include a DC-DC converter. In the power converter 100, if the multiple AC terminals 41 are three AC terminals 41, the AC power may be, for example, three-phase AC power with U phase, V phase, and W phase.

[0032] The power converter 100 includes a power conversion circuit 11 and multiple (in) Figure 1 In the example shown, three switches (8) and multiple switches (in) Figure 1 In the example shown, there are three resonant capacitors 9, regenerative capacitors 15, and multiple (in) Figure 1 In the example shown, there are three resonant inductors L1 and a controller 50. Multiple switches 8 can each be, for example, bidirectional switches.

[0033] The power conversion circuit 11 includes multiple (in) Figure 1 In the example shown, three) first switching elements 1 and multiple (in Figure 1 In the example shown, there are three) second switching elements 2. In the power conversion circuit 11, multiple (in Figure 1 In the example shown, the three switching circuits 10 are connected in parallel with each other. In each switching circuit 10, a first switching element of a plurality of first switching elements 1 and a corresponding second switching element of a plurality of second switching elements 2 are connected in series one-to-one. In the power conversion circuit 11, the plurality of first switching elements 1 are connected to a first DC terminal 31, and the plurality of second switching elements 2 are connected to a second DC terminal 32.

[0034] Multiple AC terminals 41 are provided one-to-one for multiple switching circuits 10. Each of the multiple AC terminals 41 is connected to the connection node 3 between the first switching element 1 and the second switching element 2 of the corresponding switching circuit in the multiple switching circuits 10.

[0035] Multiple switches 8 are provided one-to-one for multiple switching circuits 10. Each of the multiple switches 8 has a first terminal 81 and a second terminal 82. The first terminal 81 of each of the multiple switches 8 is connected to the connection node 3 between the first switching element 1 and the second switching element 2 of the corresponding switching circuit in the multiple switching circuits 10.

[0036] The plurality of resonant capacitors 9 are provided one-to-one with respect to the plurality of switches 8. The plurality of resonant capacitors 9 are each connected between the first terminal 81 of the respective switch of the plurality of switches 8 and the second DC terminal 32.

[0037] The plurality of resonant inductors L1 each have a third terminal and a fourth terminal. In each of the plurality of resonant inductors L1, the fourth terminal is connected to the regeneration capacitor 15. In each of the plurality of resonant inductors L1, the third terminal is connected to the second terminal 82 of the respective switch of the plurality of switches 8.

[0038] The regeneration capacitor 15 has a fifth terminal 153 and a sixth terminal 154. In the regeneration capacitor 15, the fifth terminal 153 is connected to the second DC terminal 32, and the sixth terminal 154 is connected to the fourth terminal of each of the plurality of resonant inductors L1.

[0039] The controller 50 controls the plurality of first switching elements 1, the plurality of second switching elements 2, and the plurality of switches 8.

[0040] (2) Details of the power converter

[0041] In the following description, for the sake of convenience of description, the switching circuits 10 for the U-phase, the V-phase, and the W-phase will be hereinafter referred to as "switching circuit 10U", "switching circuit 10V", and "switching circuit 10W", respectively, for the plurality of switching circuits 10. Further, in the following description, the first switching element 1 and the second switching element 2 of the switching circuit 10U will be hereinafter referred to as "first switching element 1U" and "second switching element 2U", respectively. Likewise, in the following description, the first switching element 1 and the second switching element 2 of the switching circuit 10V will be hereinafter referred to as "first switching element 1V" and "second switching element 2V", respectively. Likewise, in the following description, the first switching element 1 and the second switching element 2 of the switching circuit 10W will be hereinafter referred to as "first switching element 1W" and "second switching element 2W", respectively. Further, in the following description, the connection node 3 between the first switching element 1U and the second switching element 2U will be hereinafter referred to as "connection node 3U", the connection node 3 between the first switching element 1V and the second switching element 2V will be hereinafter referred to as "connection node 3V", and the connection node 3 between the first switching element 1W and the second switching element 2W will be hereinafter referred to as "connection node 3W". Further, in the following description, the AC terminal 41 connected to the connection node 3U will be hereinafter referred to as "AC terminal 41U", the AC terminal 41 connected to the connection node 3V will be hereinafter referred to as "AC terminal 41V", and the AC terminal 41 connected to the connection node 3W will be hereinafter referred to as "AC terminal 41W". Further, in the following description, the resonance capacitor 9 connected in parallel to the second switching element 2U will be hereinafter referred to as "resonance capacitor 9U", the resonance capacitor 9 connected in parallel to the second switching element 2V will be hereinafter referred to as "resonance capacitor 9V", and the resonance capacitor 9 connected in parallel to the second switching element 2W will be hereinafter referred to as "resonance capacitor 9W". Further, in the following description, the switch 8 connected to the connection node 3U will be hereinafter referred to as "switch 8U", the switch 8 connected to the connection node 3V will be hereinafter referred to as "switch 8V", and the switch 8 connected to the connection node 3W will be hereinafter referred to as "switch 8W".

[0042] In the power converter 100, the high-potential output terminal (positive electrode) of the DC power supply E1 is connected to the first DC terminal 31, and the low-potential output terminal (negative electrode) of the DC power supply E1 is connected to the second DC terminal 32. Further, in the power converter 100, the U-phase terminal, the V-phase terminal, and the W-phase terminal of the AC load RA1 are connected to the three AC terminals 41U, 41V, and 41W, respectively.

[0043] In the power conversion circuit 11, the plurality of (three in the example shown) first switching elements 1 and the plurality of (three in the example shown) second switching elements 2 are connected in series between the first DC terminal 31 and the second DC terminal 32. Figure 1 In the example shown, the first switching element 1 and the second switching element 2 are connected in series between the first DC terminal 31 and the second DC terminal 32.Figure 1 In the illustrated example, the second switching elements 2 each have a control terminal, a first main terminal, and a second main terminal. The control terminals of the plurality of first switching elements 1 and the plurality of second switching elements 2 are connected to the controller 50. In each of the plurality of switching circuits 10 of the power converter 100, the first main terminal of the first switching element 1 is connected to the first DC terminal 31, the second main terminal of the first switching element 1 is connected to the first main terminal of the second switching element 2, and the second main terminal of the second switching element 2 is connected to the second DC terminal 32. In each of the plurality of switching circuits 10, the first switching element 1 is a high-side switching element (P-side switching element), and the second switching element 2 is a low-side switching element (N-side switching element). The plurality of first switching elements 1 and the plurality of second switching elements 2 each may, for example, be an insulated gate bipolar transistor (IGBT). Thus, in each of the plurality of first switching elements 1 and the plurality of second switching elements 2, the control terminal, the first main terminal, and the second main terminal are respectively a gate terminal, a collector terminal, and an emitter terminal.

[0044] The power conversion circuit 11 further includes a plurality of (e.g., three) first diodes 4 that are connected in anti-parallel one-to-one to the plurality of (e.g., three) first switching elements 1, and a plurality of (e.g., three) second diodes 5 that are connected in anti-parallel one-to-one to the plurality of (e.g., three) second switching elements 2. In each of the plurality of first diodes 4, the anode of the first diode 4 is connected to the second main terminal (emitter terminal) of the first switching element 1 corresponding to the first diode 4, and the cathode of the first diode 4 is connected to the first main terminal (collector terminal) of the first switching element 1 corresponding to the first diode 4. In each of the plurality of second diodes 5, the anode of the second diode 5 is connected to the second main terminal (emitter terminal) of the second switching element 2 corresponding to the second diode 5, and the cathode of the second diode 5 is connected to the first main terminal (collector terminal) of the second switching element 2 corresponding to the second diode 5.

[0045] The U-phase terminal of the AC load RA1 may, for example, be connected to the connection node 3U between the first switching element 1U and the second switching element 2U via the AC terminal 41U. The V-phase of the AC load RA1 may, for example, be connected to the connection node 3V between the first switching element 1V and the second switching element 2V via the AC terminal 41V. The W-phase of the AC load RA1 may, for example, be connected to the connection node 3W between the first switching element 1W and the second switching element 2W via the AC terminal 41W.

[0046] Multiple resonant capacitors 9 are provided one-to-one with the multiple switches 8. Each of the multiple resonant capacitors 9 is connected between the first terminal 81 and the second DC terminal 32 of the corresponding switch in the multiple switches 8. The power converter 100 includes multiple resonant circuits. Each of the multiple resonant circuits includes a corresponding resonant capacitor in the resonant capacitors 9 and a corresponding resonant inductor in the resonant inductor L1.

[0047] Each of the multiple switches 8 includes a third switching element 6 and a fourth switching element 7. Multiple (in) Figure 1 In the example shown, three) third switching elements 6 and multiple (in Figure 1 In the example shown, each of the three fourth switching elements 7 has a control terminal, a first main terminal, and a second main terminal. The control terminals of each of the plurality of third switching elements 6 and the plurality of fourth switching elements 7 are connected to the controller 50. Each of the plurality of third switching elements 6 and the plurality of fourth switching elements 7 can, for example, be implemented as an IGBT. Thus, in each of the plurality of third switching elements 6 and the plurality of fourth switching elements 7, its control terminal, first main terminal, and second main terminal are respectively the gate terminal, collector terminal, and emitter terminal. In each of the plurality of switches 8, the third switching elements 6 and the fourth switching elements 7 are connected in anti-series to each other. In each of the plurality of switches 8, the first main terminal (collector terminal) of the third switching element 6 is connected to the first main terminal (collector terminal) of the fourth switching element 7. In each of the plurality of switches 8, the second main terminal (emitter terminal) of the third switching element 6 is connected to the connection node 3 of the corresponding switching circuit in the plurality of switching circuits 10, and the second main terminal (emitter terminal) of the fourth switching element 7 is connected to the corresponding resonant inductor in the plurality of resonant inductors L1. Each of the multiple switches 8 also includes a diode 61 connected in antiparallel to the third switching element 6 and a diode 71 connected in antiparallel to the fourth switching element 7.

[0048] In the power converter 100, switch 8U is connected to connection node 3U between first switching element 1U and second switching element 2U. Switch 8V is connected to connection node 3V between first switching element 1V and second switching element 2V. Switch 8W is connected to connection node 3W between first switching element 1W and second switching element 2W. In the following description, for ease of description, the third switching element 6 and the fourth switching element 7 of switch 8U will be referred to as "third switching element 6U" and "fourth switching element 7U" respectively, the third switching element 6 and the fourth switching element 7 of switch 8V will be referred to as "third switching element 6V" and "fourth switching element 7V" respectively, and the third switching element 6 and the fourth switching element 7 of switch 8W will be referred to as "third switching element 6W" and "fourth switching element 7W" respectively.

[0049] The plurality of switches 8 is controlled by the controller 50. In other words, the third switching element 6U, the fourth switching element 7U, the third switching element 6V, the fourth switching element 7V, the third switching element 6W, and the fourth switching element 7W are controlled by the controller 50.

[0050] The plurality of resonant inductors L1 each has a third terminal and a fourth terminal. In each of the plurality of resonant inductors L1, the third terminal is connected to the second terminal 82 of the corresponding switch of the plurality of switches 8. The fourth terminal of each of the plurality of resonant inductors L1 is connected to the sixth terminal 154 of the regenerative capacitor 15. The inductance of each of the plurality of resonant inductors L1 is equal to each other. That is, the inductance of each of the three resonant inductors L1 is equal to each other. As used herein, the expression “the inductance of each of the three resonant inductors L1 is equal to each other” not only refers to the case where the inductance of each of two resonant inductors L1 out of the three resonant inductors L1 is exactly equal to the inductance of the other resonant inductor L1, but also refers to the case where the inductance of each of two resonant inductors L1 is equal to or greater than 95% of the inductance of the other resonant inductor L1 and equal to or less than 105% of the inductance of the other resonant inductor L1.

[0051] The regenerative capacitor 15 is connected between the fourth terminal of each of the plurality of resonant inductors L1 and the second DC terminal 32. The regenerative capacitor 15 may, for example, be a film capacitor.

[0052] The controller 50 controls the plurality of first switching elements 1, the plurality of second switching elements 2, and the plurality of switches 8. The agent that performs the function of the controller 50 includes a computer system. The computer system includes a single or a plurality of computers. The computer system includes a processor and a memory as its main hardware components. The computer system functions as the agent that performs the function of the controller 50 according to the present disclosure by causing the processor to execute a program stored in the memory of the computer system. The program can be stored in advance in the memory of the computer system. Alternatively, the program can also be downloaded through a telecommunication line, or distributed after having been recorded in a non-transitory storage medium such as a memory card, an optical disk, or a hard disk drive (magnetic disk), any of which is readable by the computer system. The processor of the computer system can be constituted by a single or a plurality of electronic circuits including a semiconductor integrated circuit (IC) or a large-scale integrated circuit (LSI). These electronic circuits can be integrated together on a single chip or distributed on a plurality of chips, whichever is appropriate. These plurality of chips can be aggregated together in a single device or distributed among a plurality of devices without limitation.

[0053] The controller 50 outputs control signals SU1, SV1, SW1 for controlling the on / off states of the plurality of first switching elements 1U, 1V, 1W, respectively. The control signals SU1, SV1, SW1 each can be, for example, a pulse width modulation (PWM) signal having a potential level that alternates between a first potential level (hereinafter referred to as "low level") and a second potential level (hereinafter referred to as "high level") that is higher than the first potential level. The first switching elements 1U, 1V, 1W each become conductive when the control signals SU1, SV1, SW1 have the high level, and become non-conductive when the control signals SU1, SV1, SW1 have the low level. In addition, the controller 50 also outputs control signals SU2, SV2, SW2 for controlling the on / off states of the plurality of second switching elements 2U, 2V, 2W, respectively. The control signals SU2, SV2, SW2 each can be, for example, a PWM signal having a potential level that alternates between a first potential level (hereinafter referred to as "low level") and a second potential level (hereinafter referred to as "high level") that is higher than the first potential level. The second switching elements 2U, 2V, 2W each become conductive when the control signals SU2, SV2, SW2 have the high level, and become non-conductive when the control signals SU2, SV2, SW2 have the low level.

[0054] The controller 50 generates the control signals SU1, SV1, SW1 for the plurality of first switching elements 1U, 1V, 1W, respectively, and the control signals SU2, SV2, SW2 for the plurality of second switching elements 2U, 2V, 2W, respectively, using a carrier signal having a sawtooth waveform. More specifically, the controller 50 generates the control signals SU1, SU2 to be applied to the first switching element 1U and the second switching element 2U, respectively, based on at least the carrier signal and a U-phase voltage command. Further, the controller 50 generates the control signals SV1, SV2 to be applied to the first switching element 1V and the second switching element 2V, respectively, based on at least the carrier signal and a V-phase voltage command. Further, the controller 50 generates the control signals SW1, SW2 to be applied to the first switching element 1W and the second switching element 2W, respectively, based on at least the carrier signal and a W-phase voltage command. The U-phase voltage command, the V-phase voltage command, and the W-phase voltage command can be, for example, sine wave signals whose phases differ by 120 degrees from each other and whose values (voltage command values) vary with time. Note that the waveform of the carrier signal does not necessarily have to be a sawtooth waveform, but can also be a triangular waveform. Further, the U-phase voltage command, the V-phase voltage command, and the W-phase voltage command each have one period of the same length. In addition, one period of the U-phase voltage command, the V-phase voltage command, and the W-phase voltage command is longer than one period of the carrier signal.

[0055] The duty ratio of the control signals SU1, SU2 to be applied to the first switching element 1U and the second switching element 2U, respectively, from the controller 50 varies in accordance with the U-phase voltage command. In the example of the present embodiment, the duty ratio of the control signals SU1, SU2 is higher when the U-phase voltage command is positive than when the U-phase voltage command is negative.Figure 2 In this diagram, the duty cycle of control signal SU1 is shown as "U-phase duty cycle". Controller 50 (reference) Figure 1 The controller 50 generates a control signal SU1 to be applied to the first switching element 1U by comparing the U-phase voltage command with the carrier signal. The controller 50 generates a control signal SU2 to be applied to the second switching element 2U by inverting the control signal SU1. Furthermore, to prevent the conduction periods of the first switching element 1U and the second switching element 2U from overlapping, the controller 50 sets a dead time period Td (see reference) between the high-level periods of control signal SU1 and control signal SU2. Figure 3 ).

[0056] The duty cycles of the control signals SV1 and SV2 applied from controller 50 to the first switching element 1V and the second switching element 2V respectively vary according to the V-phase voltage command. Figure 2 In this diagram, the duty cycle of control signal SV1 is shown as "V-phase duty cycle". Controller 50 (reference) Figure 1 The controller 50 generates a control signal SV1 to be applied to the first switching element 1V by comparing the V-phase voltage command with the carrier signal. The controller 50 also generates a control signal SV2 to be applied to the second switching element 2V by inverting the control signal SV1. Furthermore, to prevent the conduction periods of the first switching element 1V and the second switching element 2V from overlapping, the controller 50 sets a dead time period between the high-level periods of control signal SV1 and control signal SV2.

[0057] The duty cycles of the control signals SW1 and SW2 applied from controller 50 to the first switching element 1W and the second switching element 2W respectively vary according to the W-phase voltage command. Figure 2 In the diagram, the duty cycle of control signal SW1 is shown as "W-phase duty cycle". Controller 50 (reference) Figure 1 The controller 50 generates a control signal SW1 to be applied to the first switching element 1W by comparing the W-phase voltage command with the carrier signal. The controller 50 generates a control signal SW2 to be applied to the second switching element 2W by inverting the control signal SW1. Furthermore, to prevent the conduction periods of the first switching element 1W and the second switching element 2W from overlapping, the controller 50 sets a dead time period Td between the high-level periods of control signal SW1 and control signal SW2.

[0058] The U-phase voltage command, V-phase voltage command, and W-phase voltage command can, for example, be sinusoidal signals whose phases differ from each other by 120 degrees and whose values ​​vary with time. Thus, for example, as... Figure 2As shown, the duty ratios of the respective control signals SU1, SV1, SW1 (i.e., the U-phase duty ratio, the V-phase duty ratio, and the W-phase duty ratio) vary in the form of a sine wave whose phase is shifted by 120 degrees from one another. In the same manner, the duty ratios of the respective control signals SU2, SV2, SW2 also vary in the form of a sine wave whose phase is shifted by 120 degrees from one another.

[0059] The controller 50 generates the respective control signals SU1, SU2, SV1, SV2, SW1, SW2 based on the carrier signals, the respective voltage commands, and information about the state of the AC load RA1. For example, if the AC load RA1 is a three-phase motor, the information about the state of the AC load RA1 can include, for example, detection values provided by a plurality of current sensors for detecting the output currents (hereinafter referred to as "load currents") iU, iV, iW flowing through the U-phase, the V-phase, and the W-phase of the AC load RA1, respectively.

[0060] The plurality of switches 8, the plurality of resonant inductors L1, the plurality of resonant capacitors 9, and the regeneration capacitor 15 are provided to perform zero-voltage soft switching of the plurality of first switching elements 1 and the plurality of second switching elements 2. Note that, in the power converter 100, Figure 1 the voltage across the regeneration capacitor 15 is designated by V15.

[0061] In the power converter 100, the controller 50 not only controls the plurality of first switching elements 1 and the plurality of second switching elements 2 of the power conversion circuit 11 but also controls the plurality of switches 8.

[0062] The controller 50 generates control signals SU6, SU7, SV6, SV7, SW6, SW7 for controlling the on / off states of the respective third switching element 6U, fourth switching element 7U, third switching element 6V, fourth switching element 7V, third switching element 6W, and fourth switching element 7W, and outputs the control signals SU6, SU7, SV6, SV7, SW6, SW7 to the gate terminals of the respective third switching element 6U, fourth switching element 7U, third switching element 6V, fourth switching element 7V, third switching element 6W, and fourth switching element 7W.

[0063] If the third switching element 6U is on and the fourth switching element 7U is off, the switch 8U enables a charging current, which is a current for charging the resonant capacitor 9U, to flow in the order of the regeneration capacitor 15, the resonant inductor L1, the switch 8U, and the resonant capacitor 9U. On the other hand, if the third switching element 6U is off and the fourth switching element 7U is on, the switch 8U enables a discharging current, which is a current for discharging the resonant capacitor 9U, to flow in the order of the resonant capacitor 9U, the switch 8U, the resonant inductor L1, and the regeneration capacitor 15.

[0064] If the third switching element 6V is on and the fourth switching element 7V is off, then switch 8V allows the charging current to flow sequentially through the regenerative capacitor 15, the resonant inductor L1, switch 8V, and the resonant capacitor 9V. This charging current is used to charge the resonant capacitor 9V. Conversely, if the third switching element 6V is off and the fourth switching element 7V is on, then switch 8V allows the discharging current to flow sequentially through the resonant capacitor 9V, switch 8V, the resonant inductor L1, and the regenerative capacitor 15. This discharging current is used to discharge from the resonant capacitor 9V.

[0065] If the third switching element 6W is turned on and the fourth switching element 7W is turned off, then switch 8W allows the charging current, which flows sequentially through regenerative capacitor 15, resonant inductor L1, switch 8W, and resonant capacitor 9W, to pass through. This charging current is used to charge resonant capacitor 9W. Conversely, if the third switching element 6W is turned off and the fourth switching element 7W is turned on, then switch 8W allows the discharging current, which flows sequentially through resonant capacitor 9W, switch 8W, resonant inductor L1, and regenerative capacitor 15, to pass through. This discharging current is used to discharge from resonant capacitor 9W.

[0066] (3) Operation of the power converter

[0067] In the following description, for the current iL1 flowing through the resonant inductor L1, if the current is in the direction of... Figure 1 If the current flows in the direction indicated by the arrow, then the polarity of the current iL1 is assumed to be positive. On the other hand, if the current iL1 flows in the direction indicated by the arrow... Figure 1 If the arrows indicate flow in the opposite direction, then the polarity of current iL1 is assumed to be negative. Furthermore, in the following description, for the load currents iU, iV, and iW flowing through phases U, V, and W of AC load RA1 respectively, if the load currents iU, iV, and iW are flowing in the direction indicated by the arrows, then the polarity of current iL1 is assumed to be negative. Figure 1 If the load currents flow in the direction indicated by the corresponding arrows in the diagram, then it is assumed that the polarity of the load currents iU, iV, and iW is positive. On the other hand, if the load currents iU, iV, and iW flow in the direction indicated by the arrows in the diagram, then the polarity of the load currents iU, iV, and iW is positive. Figure 1 If the arrows indicate flow in the opposite direction, then it is assumed that the polarity of the load currents iU, iV, and iW is negative. Furthermore, for the currents i9U, i9V, and i9W flowing through the resonant capacitors 9U, 9V, and 9W respectively, if the currents i9U, i9V, and i9W are flowing in the direction indicated by the arrows, then... Figure 1 If the currents flow in the direction indicated by the corresponding arrows in the diagram, then it is assumed that the polarity of currents i9U, i9V, and i9W is positive. On the other hand, if currents i9U, i9V, and i9W flow in the direction indicated by the arrows in the diagram, then the polarity of currents i9U, i9V, and i9W is positive. Figure 1The polarities of the currents i9u, i9v, i9w are assumed to be negative if the directions indicated by the arrows are opposite directions. Thus, the polarities of the currents i9u, i9v, i9w are positive in the case of a discharging operation in which the resonant capacitors 9u, 9v, 9w are discharged. On the other hand, the polarities of the currents i9u, i9v, i9w are negative in the case of a charging operation in which the resonant capacitors 9u, 9v, 9w are charged.

[0068] The controller 50 sets a dead time period Td between the high-level period of the control signal su1, sv1, sw1 for the first switching element 1u, 1v, 1w and the high-level period of the control signal su2, sv2, sw2 for the second switching element 2u, 2v, 2w for each of the plurality of switching circuits 10.

[0069] Next, the basic operation of the controller 50 to perform zero-voltage soft switching of each of the plurality of first switching elements 1 and the plurality of second switching elements 2 will be described with reference to Figures 1 to 5 Figures 6 to 8 Next, the operation of the controller 50 in a ringing period in which ringing occurs and before and after the ringing period will be described with reference to

[0070] (3.1) Basic operation

[0071] When performing zero-voltage soft switching of the first switching element 1, it is necessary to reduce the voltage across the first switching element 1 to zero immediately before the first switching element 1, which is the target of zero-voltage soft switching, becomes conductive. When performing zero-voltage soft switching of the second switching element 2, it is necessary to reduce the voltage across the second switching element 2 to zero immediately before the second switching element 2, which is the target of zero-voltage soft switching, becomes conductive. In the following description, the switching element, which is the first switching element 1 or the second switching element 2, which is the target of zero-voltage soft switching will be referred to hereinafter as the "target switching element".

[0072] The basic operation of the controller 50 changes depending on the polarity of the load current flowing through the AC terminal 41 connected to the target switching element, i.e., positive or negative, and depending on whether the resonant capacitor 9 connected in series or parallel to the target switching element is performing a charging operation or a discharging operation. The load current iu, iv, iw has a positive polarity when flowing from the AC terminal 41 toward the AC load Ral, and has a negative polarity when flowing from the AC load Ral toward the AC terminal 41. When the resonant capacitor 9 is performing a charging operation, the voltage across the resonant capacitor 9 increases. On the other hand, when the resonant capacitor 9 is performing a discharging operation, the voltage across the resonant capacitor 9 decreases. The voltage across each of the plurality of second switching elements 2 is the same as the voltage across the resonant capacitor 9 connected in parallel to the second switching element 2.

[0073] ​If the object of soft switching is the first switching element 1 (hereinafter referred to as "object first switching element 1"), and the polarity of the load current flowing through the AC terminal 41 connected to the object first switching element 1 is positive, the controller 50 makes the third switching element 6 corresponding to the object first switching element 1 become conductive. In this way, the controller 50 causes the resonant inductor LI and the resonant capacitor 9 connected to the object first switching element 1 to resonate, thereby charging the resonant capacitor 9 with the electric charge supplied from the regeneration capacitor 15 and lowering the voltage across the object first switching element 1 to zero. This enables the power converter 100 to perform zero-voltage soft switching of the object first switching element 1.

[0074] On the other hand, if the polarity of the load current flowing through the AC terminal 41 connected to the object second switching element 2 is negative, the controller 50 makes the fourth switching element 7 corresponding to the object second switching element 2 become conductive. In this way, the controller 50 causes the resonant capacitor 9 and the resonant inductor LI connected to the object second switching element 2 to resonate, thereby discharging from the resonant capacitor 9 and lowering the voltage across the object second switching element 2 to zero. This enables the power converter 100 to perform zero-voltage soft switching of the object second switching element 2.

[0075] In Figure 3 the control signals SU1, SU2, the control signals SU6, SU7, the current iLi flowing through the resonant inductor LI, the voltage VIu across the first switching element 1U, and the voltage V2u across the second switching element 2U are shown in the case where the object switching element is the first switching element 1U of the switching circuit 10U and in the case where the object switching element is the second switching element 2U of the switching circuit 10U. Further, in Figure 3 the dead time period Td set by the controller 50 to prevent the in-phase first switching element 1U and the second switching element 2U from becoming conductive at the same time is also shown. Further, in Figure 3 the voltage value of the DC power supply El is shown as Vd.

[0076] If the object switching element is the first switching element 1U, in the switching circuit 10U, the voltage V2u across the second switching element 2U becomes equal to Vd at the time t2 at which the dead time period Td immediately preceding the high level period of the control signal SU1 ends, and the voltage VIu across the first switching element 1U becomes zero at the time t2 at which the dead time period Td immediately preceding the high level period of the control signal SU1 ends. Thus, when the control signal SU1 changes from low to high at the time t2, the first switching element 1U is subjected to zero-voltage soft switching. In Figure 3In the example shown, the current iL1 flowing through the resonant inductor L1 starts to flow at the time t1 at which the high period of the control signal SU6 starts, and becomes zero at the time t2 at which the dead time period Td ends. The control signal SU6 changes from high to low at the time t3 later than the time t2. The time t3 will be described later in the section "(3.2) Operation in the ringing period in which ringing occurs and before and after the ringing period". The current iL1 flowing between the times t1 and t2 is a resonant current flowing from the regenerative capacitor 15 to the resonant capacitor 9U via the resonant inductor L1 (i.e., a charging current of the resonant capacitor 9U).

[0077] On the other hand, if the subject switching element is the second switching element 2U, in the switching circuit 10U, the voltage Vu across the first switching element 1U becomes equal to Vd at the time t5 at which the dead time period Td ends immediately before the high period of the control signal SU2, and the voltage Vu across the second switching element 2U becomes zero at the time t5 at which the dead time period Td ends. Thus, when the control signal SU2 changes from low to high at the time t5, the second switching element 2U is subjected to zero-voltage soft switching. In the example shown, the current iL1 flowing through the resonant inductor L1 starts to flow at the time t4 at which the high period of the control signal SU7 starts, and becomes zero at the time t5 at which the dead time period Td ends. The control signal SU7 changes from high to low at the time t6 later than the time t5. The time t6 is earlier than the time t7 at which the control signal SU2 changes from high to low (refer to FIG. 6) but can be the same as the time t7. That is, the time t6 can be the same as or earlier than the time t7, either of which is appropriate. The current iL1 flowing between the times t4 and t5 is a resonant current flowing from the resonant capacitor 9U to the resonant inductor L1 (i.e., a discharging current of the resonant capacitor 9U). Figure 3 In the example shown, the current iL1 flowing through the resonant inductor L1 starts to flow at the time t1 at which the high period of the control signal SU6 starts, and becomes zero at the time t2 at which the dead time period Td ends. The control signal SU6 changes from high to low at the time t3 later than the time t2. The time t3 will be described later in the section "(3.2) Operation in the ringing period in which ringing occurs and before and after the ringing period". The current iL1 flowing between the times t1 and t2 is a resonant current flowing from the regenerative capacitor 15 to the resonant capacitor 9U via the resonant inductor L1 (i.e., a charging current of the resonant capacitor 9U). Figure 8 In the example shown, the current iL1 flowing through the resonant inductor L1 starts to flow at the time t1 at which the high period of the control signal SU6 starts, and becomes zero at the time t2 at which the dead time period Td ends. The control signal SU6 changes from high to low at the time t3 later than the time t2. The time t3 will be described later in the section "(3.2) Operation in the ringing period in which ringing occurs and before and after the ringing period". The current iL1 flowing between the times t1 and t2 is a resonant current flowing from the regenerative capacitor 15 to the resonant capacitor 9U via the resonant inductor L1 (i.e., a charging current of the resonant capacitor 9U).

[0078] In Figure 4 the control signals SV1, SV2, the control signals SV6, SV7, the current iL1, the voltage V1v across the first switching element 1V, and the voltage V2v across the second switching element 2V are shown in the case where the subject switching element is the first switching element 1V of the switching circuit 10V and in the case where the subject switching element is the second switching element 2V of the switching circuit 10V.

[0079] If the object switching element is the first switching element 1V, in the switching circuit 10V, the voltage V2v across the second switching element 2V becomes equal to Vd at the time t12 at which the dead time period Td immediately preceding the high level period of the control signal SV1 ends, and the voltage V1v across the first switching element 1V becomes zero at the time t12 at which the dead time period Td immediately preceding the high level period of the control signal SV1 ends. Thus, when the control signal SV1 changes from the low level to the high level at the time t12, the first switching element 1V is subjected to zero voltage soft switching. In Figure 4 In the example shown, the current iL1 flowing through the resonant inductor L1 starts to flow at the time t11 at which the high level period of the control signal SV6 starts, and becomes zero at the time t12 at which the dead time period Td ends. The control signal SV6 changes from the high level to the low level at the time t13 later than the time t12. The current iL1 flowing between the times t11 and t12 is a resonant current flowing from the regeneration capacitor 15 to the resonant capacitor 9V via the resonant inductor L1 (i.e., a charging current of the resonant capacitor 9V).

[0080] On the other hand, if the object switching element is the second switching element 2V, in the switching circuit 10V, the voltage V1v across the first switching element 1V becomes equal to Vd at the time t15 at which the dead time period Td immediately preceding the high level period of the control signal SV2 ends, and the voltage V2v across the second switching element 2V becomes zero at the time t15 at which the dead time period Td ends. Thus, when the control signal SV2 changes from the low level to the high level at the time t15, the second switching element 2V is subjected to zero voltage soft switching. In Figure 4 In the example shown, the current iL1 flowing through the resonant inductor L1 starts to flow at the time t14 at which the high level period of the control signal SV7 starts, and becomes zero at the time t15 at which the dead time period Td ends. The control signal SV7 changes from the high level to the low level at the time t16 later than the time t15. The time t16 is earlier than the time at which the control signal SV2 changes from the high level to the low level. The current iL1 flowing between the times t14 and t15 is a resonant current flowing from the resonant capacitor 9V to the resonant inductor L1 (i.e., a discharging current of the resonant capacitor 9V).

[0081] In Figure 5 The control signals SW1, SW2, SW6, SW7, the current iL1, the voltage V1w across the first switching element 1W, and the voltage V2w across the second switching element 2W in the case where the object switching element is the first switching element 1W or the second switching element 2W of the switching circuit 10W are shown in FIG. 17.

[0082] If the object switching element is the first switching element 1W, in the switching circuit 10W, the voltage V2w across the second switching element 2W becomes equal to Vd at the time t22 at which the dead time period Td immediately before the high level period of the control signal SW1 ends, and the voltage V1w across the first switching element 1W becomes zero at the time t22 at which the dead time period Td immediately before the high level period of the control signal SW1 ends. Thus, when the control signal SW1 changes from the low level to the high level at the time t22, the first switching element 1W is subjected to zero voltage soft switching. In Figure 5 In the example shown, the current iL1 flowing through the resonant inductor L1 starts to flow at the time t21 at which the high level period of the control signal SW6 starts, and becomes zero at the time t22 at which the dead time period Td ends. The control signal SW6 changes from the high level to the low level at the time t23 later than the time t22. The current iL1 flowing between the times t21 and t22 is a resonant current flowing from the regeneration capacitor 15 to the resonant capacitor 9W via the resonant inductor L1 (i.e., a charging current of the resonant capacitor 9W).

[0083] On the other hand, if the object switching element is the second switching element 2W, in the switching circuit 10W, the voltage V1w across the first switching element 1W becomes equal to Vd at the time t25 at which the dead time period Td immediately before the high level period of the control signal SW2 ends, and the voltage V2w across the second switching element 2W becomes zero at the time t25 at which the dead time period Td ends. Thus, when the control signal SW2 changes from the low level to the high level at the time t25, the second switching element 2W is subjected to zero voltage soft switching. In Figure 5 In the example shown, the current iL1 flowing through the resonant inductor L1 starts to flow at the time t24 at which the high level period of the control signal SW7 starts, and becomes zero at the time t25 at which the dead time period Td ends. The control signal SW7 changes from the high level to the low level at the time t26 later than the time t25. The time t26 is earlier than the time at which the control signal SW2 changes from the high level to the low level. The current iL1 flowing between the times t24 and t25 is a resonant current flowing from the resonant capacitor 9W to the resonant inductor L1 (i.e., a discharging current of the resonant capacitor 9W).

[0084] (3.2) Operation in and before and after the ring period in which the ring occurs

[0085] The operation of the controller 50 in and before and after the ring period in which the ring occurs will be described with reference to Figures 6 to 8

[0086] In Figure 6 ​In the example, when the third switching element 6U of the U-phase switch 8U is turned on and its fourth switching element 7U is turned off (i.e., in the first operating mode), the current path of the current iL1 flowing through the resonant inductor L1 immediately after the current iL1 flowing through the resonant inductor L1 has become zero is indicated by the thick line. Figure 7 In the middle, as an example, when from Figure 6 When the state transitions to the state where the third switching element 6U is off and the fourth switching element 7U is off (i.e., the second operating mode), the current path of the current iL1 flowing through the resonant inductor L1 after the third switching element 6U immediately following the switch 8U has become off is indicated by the thick line. Additionally, in Figure 7 The parasitic capacitor 62 of the third switching element 6U is also shown.

[0087] In the power converter 100, immediately after the current flowing through the resonant inductor L1 has become zero, the current resumes flowing through the switch 8U, and therefore, the current iL flows along... Figure 6 The current flows along the path shown. Specifically, the current iL1 flows along the current path in sequence through the regenerative capacitor 15, the resonant inductor L1, the diode 71, the third switching element 6U, the resonant capacitor 9U, and the regenerative capacitor 15.

[0088] In the power converter 100, if the operation mode changes from the first operating mode to the second operating mode, the current iL1 flows along... Figure 7 The current path shown flows. Specifically, the current iL1 flows along the current path sequentially through regenerative capacitor 15, resonant inductor L1, diode 71, parasitic capacitor 62, resonant capacitor 9U, and regenerative capacitor 15. Note that from Figure 7 Examples of all parasitic capacitors except parasitic capacitor 62 are omitted. On the other hand, from Figure 1 Examples of all parasitic capacitors, including parasitic capacitor 62, are omitted.

[0089] On the other hand, in this power converter 100, ringing does not occur until the current flowing through the resonant inductor L1 has become zero. Additionally, in the power converter 100, ringing also occurs when the voltage V6u across the third switching element 6U of the switch 8U rises from zero volts. Ringing occurs at the precise moment when the current iL1 flowing through the resonant inductor L1 becomes zero, at which point the voltage V6u across the third switching element 6U also rings.

[0090] In a comparative example of the power converter 100 according to the first embodiment, such as Figure 9 As shown, when the voltage V6u across the third switching element 6U is ringing, the control signal SU6 changes from high to low. In this case, the timing of the third switching element 6U turning off (at...) Figure 9In the example shown, at time t2), the ringing waveform of the voltage V6u across the third switching element 6U is distorted (i.e., ringing waveform noise is superimposed).

[0091] In contrast, in the power converter 100 according to the first embodiment, as shown in Figure 8 the controller 50 causes the third switching element 6U to maintain the state immediately before a ringing period in which the voltage V6u across the third switching element 6U rings (i.e., in the Figure 8 In the example shown, the on state). As used herein, the phrase “ringing period in which the voltage V6u across the third switching element 6U rings” refers to a period in which the voltage V6u across the third switching element 6U will ring when the power converter 100 is designed, and is determined during the design phase. As used herein, the phrase “causes the third switching element 6U to maintain the state immediately before the ringing period” means that the third switching element 6U is caused to maintain the on state by keeping the level of the control signal SU6 at the high level. This enables the controller 50 to determine the timing at which the control signal SU6 to the third switching element 6U is switched from the high level to the low level (i.e., in the Figure 8 In the example shown, the ringing period in which the voltage V6u across the third switching element 6U rings is estimated before time t2). During the ringing period thus estimated, the controller 50 causes the third switching element 6U to maintain the state immediately before the ringing period thus estimated, thereby reducing the likelihood of the ringing waveform being distorted. In the power converter 100 according to the first embodiment, the controller 50 determines the timing at which the ringing period of the voltage V6u across the third switching element 6U ends (i.e., in the Figure 8 In the example shown, at time t3), the control signal SU6 is changed from the high level to the low level. As used herein, the phrase “timing at which the ringing period of the voltage V6u across the third switching element 6U ends” refers to the timing at which the amplitude of the ringing becomes zero. However, this is merely an example, and should not be construed as limiting. The timing need not necessarily be the timing at which the amplitude of the ringing becomes zero, but can also be the timing at which the amplitude of the ringing becomes equal to or smaller than a threshold value. The threshold value is a value determined during the design phase of the power converter 100. For example, the threshold value can be 10% of the steady-state voltage of the voltage V6u across the third switching element 6U determined during the design phase. Note that in Figure 8 and Figure 9 the control signals SU1, SU2, SU6, SU7, the current iL1 flowing through the resonant inductor LI, and the voltage V6u across the third switching element 6U are shown.

[0092] Reference has been made to Figures 6 to 8The ringing period of the ringing that occurs when the voltage V6u across the U-phase third switching element 6U rises from zero volts and the operation of the controller 50 during the ringing period are described. The same statements apply equally to the ringing period of the ringing that occurs when the voltage across the V-phase third switching element 6V rises from zero volts and the operation of the controller 50 during the ringing period and the ringing period of the ringing that occurs when the voltage across the W-phase third switching element 6W rises from zero volts and the operation of the controller 50 during the ringing period. The statements that apply to the ringing period of the ringing that occurs when the voltage V6u across the U-phase third switching element 6U rises from zero volts and the operation of the controller 50 during the ringing period also apply to the ringing period of the ringing that occurs when the voltage across the U-phase fourth switching element 7U rises from zero volts and the operation of the controller 50 during the ringing period, the ringing period of the ringing that occurs when the voltage across the V-phase fourth switching element 7V rises from zero volts and the operation of the controller 50 during the ringing period, and the ringing period of the ringing that occurs when the voltage across the W-phase fourth switching element 7W rises from zero volts and the operation of the controller 50 during the ringing period.

[0093] (3.3) Characteristics

[0094] In Figure 10 A1 indicates a measured value of the radiated noise generated in the power converter 100 according to the first embodiment, and A2 indicates a measured value of the radiated noise generated in the power converter according to the comparative example. In Figure 10 In

[0095] (4) Advantages

[0096] The power converter 100 according to the first embodiment includes a first DC terminal 31 and a second DC terminal 32, a power conversion circuit 11, a plurality of switches 8, a plurality of resonance capacitors 9, a plurality of resonance inductors L1, a regeneration capacitor 15, a plurality of AC terminals 41, and a controller 50. The power conversion circuit 11 includes a plurality of switching circuits 10. The plurality of switching circuits 10 each includes a first switching element 1 and a second switching element 2 connected in series with each other, a first diode 4 connected in anti-parallel to the first switching element 1, and a second diode 5 connected in anti-parallel to the second switching element 2. In the plurality of switching circuits 10, the first switching element 1 is connected to the first DC terminal 31, and the second switching element 2 is connected to the second DC terminal 32. The plurality of switches 8 each has a first terminal 81 and a second terminal 82. The plurality of switches 8 is provided one-to-one with respect to the plurality of switching circuits 10. The plurality of switches 8 is each connected to a connection node 3 between the first switching element 1 and the second switching element 2 of a corresponding switching circuit of the plurality of switching circuits 10. The plurality of resonance capacitors 9 is provided one-to-one with respect to the plurality of switches 8. The plurality of resonance capacitors 9 is each connected between the first terminal 81 of a corresponding switch of the plurality of switches 8 and the second DC terminal 32. The plurality of resonance inductors L1 is provided one-to-one with respect to the plurality of switches 8. The plurality of resonance inductors L1 is each connected to the second terminal 82 of a corresponding switch of the plurality of switches 8. The plurality of AC terminals 41 is provided one-to-one with respect to the plurality of switching circuits 10. The plurality of AC terminals 41 is each connected to the connection node 3 between the first switching element 1 and the second switching element 2 of a corresponding switching circuit of the plurality of switching circuits 10. The controller 50 controls the plurality of first switching elements 1, the plurality of second switching elements 2, and the plurality of switches 8. The plurality of switches 8 each includes a third switching element 6 and a fourth switching element 7. When the third switching element 6 is in an on state, the third switching element 6 causes a current iL1 from the resonance inductor L1 to flow therethrough. When the fourth switching element 7 is in an on state, the fourth switching element 7 causes a current to flow therethrough in a direction opposite to that in the third switching element 6. The controller 50 applies a control signal having a potential alternated between a high level and a low level to each of the plurality of first switching elements 1, the plurality of second switching elements 2, the plurality of third switching elements 6, and the plurality of fourth switching elements 7. The controller 50 sets, with respect to each of the plurality of switching circuits 10, a dead time period Td between a high-level period of the control signal for the first switching element 1 and a high-level period of the control signal for the second switching element 2. The controller 50 enables at least a part of a high-level period of the control signal for each of the plurality of switches 8 to overlap with the dead time period Td. The controller 50 causes, with respect to each of the plurality of switches 8, the third switching element 6 to maintain a state (i.e., an on state) immediately before a ringing period during which a voltage across the third switching element 6 rings.

[0097] This configuration allows the radiation noise to be reduced.

[0098] In the power converter 100 according to the first embodiment, the controller 50 causes the third switching element 6 corresponding one-to-one to the plurality of switching circuits 10 to be turned off at or before the timing at which the first switching element 1 is caused to be turned off in each of the plurality of switching circuits 10. Note that the phrase "at or before the timing at which the first switching element 1 is caused to be turned off" refers not only to a timing earlier than the timing at which the first switching element 1 is caused to be turned off, but also to the timing at which the first switching element 1 is caused to be turned off.

[0099] This configuration allows zero-voltage soft switching of the first switching element 1 to be performed.

[0100] In addition, the controller 50 also causes the fourth switching element 7 to maintain the state immediately before the ring period in which the voltage across the fourth switching element 7 rings. This enables the power converter 100 according to the first embodiment to further reduce radiated noise.

[0101] (Second Embodiment)

[0102] A power converter 100A according to a second embodiment will be described with reference to Figure 11

[0103] (1) Configuration

[0104] The power converter 100A further includes another regeneration capacitor 16 (hereinafter referred to as "second regeneration capacitor 16") connected between a sixth terminal 154 of the regeneration capacitor 15 (hereinafter referred to as "first regeneration capacitor 15"), which is different from the power converter 100.

[0105] ​The second regenerative capacitor 16 is connected in series to the first regenerative capacitor 15. Thus, in the power converter 100A, a series circuit of the second regenerative capacitor 16 and the first regenerative capacitor 15 is connected between the first DC terminal 31 and the second DC terminal 32. In the power converter 100A, a plurality of resonant inductors L1 is connected to a path between the first regenerative capacitor 15 and the second regenerative capacitor 16. The capacitance of the second regenerative capacitor 16 is the same as the capacitance of the first regenerative capacitor 15. As used herein, the expression "the capacitance of the second regenerative capacitor 16 is the same as the capacitance of the first regenerative capacitor 15" refers not only to the case where the capacitance of the second regenerative capacitor 16 is exactly equal to the capacitance of the first regenerative capacitor 15, but also to the case where the capacitance of the second regenerative capacitor 16 is equal to or greater than 95% of the capacitance of the first regenerative capacitor 15 and equal to or less than 105% of the capacitance of the first regenerative capacitor 15.

[0106] In the power converter 100A according to the second embodiment, the voltage V15 across the first regenerative capacitor 15 (i.e., the potential at the sixth terminal 154 of the first regenerative capacitor 15) has a value calculated by dividing the voltage value Vd of the DC power source El by 2, which is the number of the capacitors (i.e., the second regenerative capacitor 16 and the first regenerative capacitor 15) provided. Thus, the voltage V15 across the first regenerative capacitor 15 is approximately equal to Vd / 2. In the power converter 100A according to the second embodiment, the controller 50 can store in advance the value of the voltage V15 across the first regenerative capacitor 15.

[0107] (2) Advantages

[0108] The controller 50 of the power converter 100A according to the second embodiment operates in the same manner as the controller 50 of the power converter 100 according to the first embodiment. Thus, the power converter 100A according to the second embodiment can also reduce the radiated noise as with the power converter 100 according to the first embodiment.

[0109] (Third Embodiment)

[0110] The power converter 100B according to the third embodiment will be described with reference to Figure 12 The power converter 100B according to the third embodiment will be described with reference to

[0111] (1) Configuration

[0112] The power converter 100B includes only one resonant inductor LI, which is different from the power converter 100 according to the first embodiment. In the power converter 100B, the resonant inductor LI is commonly shared by the plurality of resonant circuits. In the power converter 100B, the third end of the resonant inductor LI is connected to the common connection node 25. The second ends 82 of the plurality of switches 8 are commonly connected to the common connection node 25.

[0113] (2) Operation of the power converter

[0114] In the power converter 100B, as in the power converter 100, the controller 50 also controls the plurality of (for example, three in the example shown) first switching elements 1, the plurality of (for example, three in the example shown) second switching elements 2, and the plurality of (for example, three in the example shown) switches 8 in the same manner as the controller 50 of the power converter 100. Figure 12 Figure 12 Figure 12

[0115] (3) Advantages

[0116] In the power converter 100B according to the third embodiment, as in the power converter 100 according to the first embodiment, the controller 50 also causes, for each of the plurality of third switching elements 6, the third switching element 6 to maintain the state (i.e., the on state) immediately before a ringing period in which the voltage across the third switching element 6 rings during the ringing period. Thus, the power converter 100B according to the third embodiment can also reduce the radiated noise, like the power converter 100 according to the first embodiment.

[0117] Further, in the power converter 100B according to the third embodiment, the number of resonant inductors LI provided is one, and the second ends 82 of the plurality of switches 8 are commonly connected to the single resonant inductor LI. Thus, the power converter 100B according to the third embodiment can contribute to miniaturization.

[0118] (Fourth Embodiment)

[0119] The power converter 100C according to the fourth embodiment will be described with reference to Figure 13 (1) Configuration

[0120]

[0121] ​​​​The power converter 100C further includes another regeneration capacitor 16 (hereinafter referred to as "second regeneration capacitor 16") connected between the sixth terminal 154 of the regeneration capacitor 15 (hereinafter referred to as "first regeneration capacitor 15"), which is different from the power converter 100B.

[0122] The second regeneration capacitor 16 is connected in series to the first regeneration capacitor 15. Thus, in this power converter 100C, the series circuit of the second regeneration capacitor 16 and the first regeneration capacitor 15 is connected between the first DC terminal 31 and the second DC terminal 32. The capacitance of the second regeneration capacitor 16 is the same as the capacitance of the first regeneration capacitor 15. As used herein, the expression "the capacitance of the second regeneration capacitor 16 is the same as the capacitance of the first regeneration capacitor 15" refers not only to the case where the capacitance of the second regeneration capacitor 16 is exactly equal to the capacitance of the first regeneration capacitor 15, but also to the case where the capacitance of the second regeneration capacitor 16 is equal to or greater than 95% of the capacitance of the first regeneration capacitor 15 and equal to or less than 105% of the capacitance of the first regeneration capacitor 15.

[0123] In the power converter 100C according to the fourth embodiment, the voltage V15 across the first regeneration capacitor 15 (i.e., the potential at the sixth terminal 154 of the first regeneration capacitor 15) has a value calculated by dividing the voltage value Vd of the DC power source El by 2, which is the number of the set capacitors (i.e., the second regeneration capacitor 16 and the first regeneration capacitor 15). Thus, the voltage V15 across the first regeneration capacitor 15 is approximately equal to Vd / 2. In the power converter 100C according to the fourth embodiment, the controller 50 can store in advance the value of the voltage V15 across the first regeneration capacitor 15.

[0124] (2) Operation

[0125] The controller 50 of the power converter 100C according to the fourth embodiment operates in the same manner as the controller 50 of the power converter 100B according to the third embodiment.

[0126] (3) Advantages

[0127] The power converter 100C according to the fourth embodiment can also reduce the radiated noise, like the power converter 100B according to the third embodiment.

[0128] (Fifth Embodiment)

[0129] Reference will be made to Figure 14 and Figure 15A power converter 100D according to a fifth embodiment will be described. In the following description, any constituent element in the power converter 100D according to the fifth embodiment that has the same function as the corresponding part of the above-described power converter 100B according to the third embodiment will be designated by the same reference numeral as that of the corresponding part, and the description thereof will be omitted herein.

[0130] (1) Configuration

[0131] The power converter 100D further includes a third diode 13 and a fourth diode 14, which are different from the power converter 100B.

[0132] In the third diode 13, the anode of the third diode 13 is connected to the connection node between the resonant inductor LI and the plurality of switches 8. In the third diode 13, the cathode of the third diode 13 is connected to the first DC terminal 31. The fourth diode 14 is connected between the connection node at which the resonant inductor LI and the plurality of switches 8 are connected to each other and the second DC terminal 32. In the fourth diode 14, the anode of the fourth diode 14 is connected to the second DC terminal 32. In the fourth diode 14, the cathode of the fourth diode 14 is connected to the connection node between the resonant inductor LI and the plurality of switches 8. Thus, the fourth diode 14 is connected in series to the third diode 13.

[0133] (2) Operation

[0134] In the power converter 100D according to the fifth embodiment, the controller 50 causes the third switching element 6 to become off before the current iLi flowing through the resonant inductor LI becomes zero, and causes the third switching element 6 to maintain its state immediately before a ringing period in which the voltage across the third switching element 6 rings, i.e., the off state, during the ringing period. More specifically, when zero-voltage soft switching of the U-phase first switching element IU is performed, for example, as shown in FIG. 12, the controller 50 changes the control signal SU6 of the third switching element 6 for the switch 8U from the high level to the low level before the current iLi flowing through the resonant inductor LI becomes zero, and maintains the potential level of the control signal SU6 at the low level during a ringing period in which the voltage V6u across the third switching element 6 rings. Figure 15

[0135] The power converter 100D includes the third diode 13. This makes it possible for the current iLi to flow along the path through the third diode 13 even when the third switching element 6 becomes off before the current iLi flowing through the resonant inductor LI becomes zero.

[0136] Reference has been made to Figure 15 ​The ringing period of the ringing that occurs when the voltage V6u across the U-phase third switching element 6U rises from zero volts and the operation of the controller 50 during the ringing period are described. The same statement is equally applicable to the ringing period of the ringing that occurs when the voltage across the V-phase third switching element 6V rises from zero volts and the operation of the controller 50 during the ringing period and the ringing period of the ringing that occurs when the voltage across the W-phase third switching element 6W rises from zero volts and the operation of the controller 50 during the ringing period.

[0137] (3) Advantages

[0138] In the power converter 100D according to the fifth embodiment, the controller 50 causes, for each of the plurality of switches 8, the third switching element 6 to maintain the state (i.e., the on state) immediately before the ringing period in which the voltage across the third switching element 6 rings during the ringing period. Thus, the power converter 100D can also reduce the radiated noise.

[0139] (4) Modification of the Fifth Embodiment

[0140] As in the first embodiment, the controller 50 causes the third switching element 6 to maintain its state (i.e., the on state) immediately before the ringing period during the ringing period and causes the third switching element 6 to become off at the timing at which the ringing period ends.

[0141] According to this modification of the fifth embodiment, as in the first embodiment, the radiated noise can also be reduced.

[0142] (Sixth Embodiment)

[0143] The power converter 100E according to the sixth embodiment will be described with reference to Figure 16 In the following description, any constituent element in the power converter 100E according to the sixth embodiment that has the same function as the corresponding part of the above-described power converter 100 according to the first embodiment will be designated by the same reference numeral as that of the corresponding part, and the description thereof will be omitted herein.

[0144] (1) Configuration

[0145] In the power converter 100E, the plurality of switches 8 each include a third switching element 6A and a fourth switching element 7A in place of the third switching element 6 and the fourth switching element 7, which is different from the power converter 100. The plurality of third switching elements 6A and the plurality of fourth switching elements 7A are each a MOSFET. In the power converter 100E, the control terminal, the first main terminal, and the second main terminal of each of the plurality of third switching elements 6A and the plurality of fourth switching elements 7A are a gate terminal, a drain terminal, and a source terminal, respectively. In each of the plurality of switches 8, the third switching element 6A and the fourth switching element 7A are connected in antiparallel. In the power converter 100E, in each of the plurality of switches 8, the first main terminal (drain terminal) of the third switching element 6A and the first main terminal (drain terminal) of the fourth switching element 7A are connected to each other. In addition, each of the plurality of switches 8 further includes a diode 61 connected in antiparallel to the third switching element 6A and a diode 71 connected in antiparallel to the fourth switching element 7A. In each of the plurality of switches 8, the second main terminal (source terminal) of the fourth switching element 7A is connected to the resonant inductor LI. In each of the plurality of switches 8, the second main terminal (source terminal) of the third switching element 6A is connected to the connection node 3 of the switching circuit 10 corresponding to the switch 8 including the third switching element 6A. The control signal SU6, SU7 is applied from the controller 50 to the third switching element 6A and the fourth switching element 7A of the switch 8U, respectively. The control signal SV6, SV7 is applied from the controller 50 to the third switching element 6A and the fourth switching element 7A of the switch 8V, respectively. The control signal SW6, SW7 is applied from the controller 50 to the third switching element 6A and the fourth switching element 7A of the switch 8W, respectively.

[0146] (2) Operation of the power converter

[0147] For example, the power converter 100E operates in the same manner as the power converter 100.

[0148] (3) Advantages

[0149] The power converter 100E according to the sixth embodiment can also reduce the radiation noise as with the power converter 100 according to the first embodiment.

[0150] (Seventh Embodiment)

[0151] A power converter 100F according to a seventh embodiment will be described with reference to Figure 17 In the following description, any constituent element in the power converter 100F according to the seventh embodiment that has the same function as the corresponding part of the above-described power converter 100 according to the first embodiment will be designated by the same reference sign as that of the corresponding part, and the description thereof will be omitted herein.

[0152] (1) Configuration

[0153] In the power converter 100F, the plurality of switches 8 each include two switching elements (i.e., the third switching element 6 and the fourth switching element 7) connected in anti-parallel with each other. In each of the plurality of switches 8, the first main terminal (collector terminal) of the third switching element 6 and the second main terminal (emitter terminal) of the fourth switching element 7 are connected to each other, and the second main terminal (emitter terminal) of the third switching element 6 and the first main terminal (collector terminal) of the fourth switching element 7 are connected to each other. In each of the plurality of switches 8, the second main terminal (emitter terminal) of the third switching element 6 is connected to the connection node 3 of the switching circuit 10 corresponding to the switch 8 including the third switching element 6. In each of the plurality of switches 8, the first main terminal (collector terminal) of the fourth switching element 7 is connected to the connection node 3 of the switching circuit 10 corresponding to the switch 8 including the fourth switching element 7. More specifically, the switch 8U is connected to the connection node 3U between the first switching element 1U and the second switching element 2U. The switch 8V is connected to the connection node 3V between the first switching element 1V and the second switching element 2V. The switch 8W is connected to the connection node 3W between the first switching element 1W and the second switching element 2W.

[0154] (2) Operation of the power converter

[0155] For example, the power converter 100F operates in the same manner as the power converter 100.

[0156] (3) Advantages

[0157] The power converter 100F according to the seventh embodiment can also reduce the radiated noise as with the power converter 100 according to the first embodiment.

[0158] (Eighth Embodiment)

[0159] The power converter 100G according to the eighth embodiment will be described with reference to Figure 18 In the following description, any constituent element in the power converter 100G according to the eighth embodiment that has the same function as the corresponding part of the above-described power converter 100 according to the first embodiment will be designated by the same reference sign as that of the corresponding part, and the description thereof will be omitted herein.

[0160] (1) Configuration

[0161] For example, as Figure 18As shown, the power converter 100G includes the first DC terminal 31 and the second DC terminal 32 and two AC terminals 41. In the power converter 100G, the DC power source El is connected between the first DC terminal 31 and the second DC terminal 32, and the AC load RA1 is connected to the two AC terminals 41. The AC load RA1 may, for example, be an AC motor. The power converter 100 converts a DC output of the DC power source El into AC power and outputs the AC power to the AC load RA1. The DC power source El may, for example, include a solar cell or a fuel cell. The DC power source El can include a DC-DC converter.

[0162] In the power converter 100G according to the eighth embodiment, the power conversion circuit 11 includes only one switching circuit 10, which is different from the power converter 100 according to the first embodiment. In addition, in the power converter 100G according to the eighth embodiment, one of the two AC terminals 41 is connected to the connection node 3 between the first switching element 1 and the second switching element 2, and the other AC terminal is connected to the second DC terminal 32, which is another difference from the power converter 100. Further, the power converter 100G according to the eighth embodiment includes only one switch 8, only one resonant inductor LI, and only one resonant capacitor 9, which is yet another difference from the power converter 100.

[0163] The controller 50 controls each of the first switching element 1, the second switching element 2, and the switch 8. The controller 50 outputs a control signal SI for controlling the first switching element 1, a control signal S2 for controlling the second switching element 2, a control signal S6 for controlling the third switching element 6, and a control signal S7 for controlling the fourth switching element 7.

[0164] (2) Operation of the power converter

[0165] In this power converter 100G, the controller 50 controls the first switching element 1, the second switching element 2, and the switch 8. The controller 50 operates in the same manner as the controller 50 of the power converter 100. More specifically, the control signals SI, S2, S6, S7 output by the controller 50 of the power converter 100G are the same as the control signals SU1, SU2, SU6, SU7 output by the controller 50 of the power converter 100 (refer to Figure 1 , Figure 3 and Figure 8 ).

[0166] (3) Advantages

[0167] The power converter 100G according to the eighth embodiment includes a first DC terminal 31 and a second DC terminal 32, a power conversion circuit 11, a switch 8, a resonance capacitor 9, a resonance inductor LI, a regeneration capacitor 15, and a controller 50. The power conversion circuit 11 includes a switching circuit 10. The switching circuit 10 includes a first switching element 1 and a second switching element 2 connected in series to each other, a first diode 4 connected in anti-parallel to the first switching element 1, and a second diode 5 connected in anti-parallel to the second switching element 2. In the switching circuit 10, the first switching element 1 is connected to the first DC terminal 31, and the second switching element 2 is connected to the second DC terminal 32. The switch 8 has a first terminal 81 and a second terminal 82. The first terminal 81 of the switch 8 is connected to a connection node 3 between the first switching element 1 and the second switching element 2. The resonance capacitor 9 is connected between the first terminal 81 of the switch 8 and the second DC terminal 32. The resonance inductor LI is connected to the second terminal 82 of the switch 8. The regeneration capacitor 15 is connected between the resonance inductor LI and the second DC terminal 32. The controller 50 controls the first switching element 1, the second switching element 2, and the switch 8. The switch 8 includes a third switching element 6 and a fourth switching element 7. When the third switching element 6 is in an on state, the third switching element 6 causes a current iL1 from the resonance inductor LI to flow therethrough. When the fourth switching element 7 is in an on state, the fourth switching element 7 causes a current to flow therethrough in a direction opposite to that in the third switching element 6. The controller 50 applies control signals S1, S2, S6, S7 having potentials that alternate between a high level and a low level to the first switching element 1, the second switching element 2, the third switching element 6, and the fourth switching element 7, respectively. The controller 50 sets a dead time period Td between a high-level period of the control signal S1 for the first switching element 1 and a high-level period of the control signal S2 for the second switching element 2 (refer to FIG. 6). The controller 50 enables at least a portion of a high-level period of the control signal S6 for the third switching element 6 to overlap the dead time period Td. The controller 50 causes the third switching element 6 to maintain its state immediately before a ringing period during which a voltage across the third switching element 6 rings. Figure 8 ) The controller 50 sets a dead time period Td between a high-level period of the control signal S1 for the first switching element 1 and a high-level period of the control signal S2 for the second switching element 2 (refer to FIG. 6). The controller 50 enables at least a portion of a high-level period of the control signal S6 for the third switching element 6 to overlap the dead time period Td. The controller 50 causes the third switching element 6 to maintain its state immediately before a ringing period during which a voltage across the third switching element 6 rings.

[0168] This configuration allows the radiation noise to be reduced.

[0169] (Other modifications)

[0170] Note that the first embodiment to the eighth embodiment and the modifications thereof described above are merely exemplary embodiments of the various embodiments and the modifications thereof of the present disclosure, and should not be construed as limiting. Rather, the first exemplary embodiment to the eighth exemplary embodiment and the modifications thereof can be easily modified in various ways according to design choice or any other factor without departing from the scope of the present disclosure.

[0171] In the power converter 100, the diodes 61, 71 are connected as external components to the third switching element 6 and the fourth switching element 7, respectively. However, this is merely an example, and should not be construed as limiting. The diodes 61, 71 can each also be elements built into the same chip as the third switching element 6 or the fourth switching element 7.

[0172] Further, in the power converter 100G, the switch 8 has the same configuration as the switch 8 of the power converter 100. Alternatively, the switch 8 of the power converter 100G can also have the same configuration as the switch 8 of the power converter 100E or the switch 8 of the power converter 100F, whichever is appropriate.

[0173] Optionally, in the power converters 100, 100A, 100B, 100C, 100D, 100E, 100F, 100G, if the plurality of resonance capacitors 9 each have a relatively small capacitance, instead of providing the plurality of resonance capacitors 9 as separate elements, the parasitic capacitors across the plurality of second switching elements 2 can also be used as the plurality of resonance capacitors 9.

[0174] Further, in the above-described embodiments, the length of the dead time period Td is set to be as long as one resonance half-period. However, the length of the dead time period Td can also be set to be different from one resonance half-period. As used herein, “one resonance half-period” is one-half of a resonance period, which is the inverse of the resonance frequency of the resonance circuit including the resonance inductor L1 and one resonance capacitor 9.

[0175] The dead time period Td can also be set by a dead time generation circuit included in, for example, a gate driver integrated circuit (IC) provided separately from the controller 50. Alternatively, the controller 50 can include a gate driver IC, and the dead time generation circuit included in the gate driver IC can set the dead time period Td.

[0176] Further, the power converters 100, 100A, 100B, 100C, 100D, 100E, 100F do not necessarily have to be configured to output three-phase AC power, but can also be configured to output more than three-phase, multi-phase AC power.

[0177] Optionally, the controller 50 can make the start timing of each of the high-level periods of the control signals SU6, SV6, and SW6 earlier than the start timing of the dead time period Td by an additional time. In order to start the LC resonance at the start timing of the dead time period Td, the controller 50 determines the additional time based on the load current so that the in-phase current iL1 and the load current are equal to each other at the start timing of the dead time period Td. More specifically, for example, using a detection result of the load current with a current sensor or a signal-processed value thereof, or an estimated value of the load current, a previously stored inductance L of the resonance inductor L1, and a detection result of the voltage V15 across the regenerative capacitor 15, the controller 50 determines the additional time by the following formula: additional time = load current x (L / V15). In this case, as the detection result of the load current or the signal-processed value thereof, a detection value at a carrier period to which the additional time is added or a detection value at a timing closest to the carrier period can be used. Further, in this case, as the estimated value of the load current, for example, a value of the load current estimated at a carrier period to which the additional time is added can be used.

[0178] (Aspects)

[0179] The foregoing description provides specific implementations of the following aspects of the present disclosure.

[0180] The power converter (100; 100A; 100B; 100C; 100D; 100E; 100F; 100G) according to the first aspect includes a first DC terminal (31) and a second DC terminal (32), a power conversion circuit (11), a switch (8), a resonance capacitor (9), a resonance inductor (LI), a regeneration capacitor (15), and a controller (50). The power conversion circuit (11) includes a switching circuit (10). The switching circuit (10) includes: a first switching element (1) and a second switching element (2) connected in series with each other; a first diode (4) connected in anti-parallel to the first switching element (1); and a second diode (5) connected in anti-parallel to the second switching element (2). In the switching circuit (10), the first switching element (1) is connected to the first DC terminal (31), and the second switching element (2) is connected to the second DC terminal (32). The switch (8) has a first end (81) and a second end (82). The first end (81) of the switch (8) is connected to a connection node (3) between the first switching element (1) and the second switching element (2). The resonance capacitor (9) is connected between the first end (81) of the switch (8) and the second DC terminal (32). The resonance inductor (LI) is connected to the second end (82) of the switch (8). The regeneration capacitor (15) is connected between the resonance inductor (LI) and the second DC terminal (32). The controller (50) controls the first switching element (1), the second switching element (2), and the switch (8). The switch (8) includes a third switching element (6; 6A) and a fourth switching element (7; 7A). When the third switching element (6; 6A) is in an on state, the third switching element (6; 6A) causes a current (iLi) from the resonance inductor (LI) to flow therethrough. When the fourth switching element (7; 7A) is in an on state, the fourth switching element (7; 7A) causes the current to flow therethrough in a direction opposite to that in the third switching element (6; 6A). The controller (50) applies a control signal to each of the first switching element (1), the second switching element (2), the third switching element (6; 6A), and the fourth switching element (7; 7A), the control signal having a potential that alternates between a high level and a low level. The controller (50) sets a dead time period (Td) between a high-level period of the control signal for the first switching element (1) and a high-level period of the control signal for the second switching element (2). The controller (50) enables at least a portion of a high-level period of the control signal for the third switching element (6; 6A) to overlap with the dead time period (Td). The controller (50) causes the third switching element (6; 6A) to maintain a state immediately preceding a ringing period during which a voltage across the third switching element (6; 6A) rings.

[0181] This aspect allows the radiation noise to be reduced.

[0182] In the power converter (100; 100A; 100B; 100C; 100E; 100F; 100G) according to the second aspect, which can be implemented in combination with the first aspect, the controller (50) causes the third switching element (6; 6A) to maintain the on state during the ringing period.

[0183] In the power converter (100; 100A; 100B; 100C; 100D; 100E; 100F; 100G) according to the third aspect, which can be implemented in combination with the first aspect, the controller (50) causes the third switching element (6; 6A) to become off before the timing at which the switching element selected from the group consisting of the first switching element (1) and the second switching element (2) to be subjected to zero-voltage soft switching becomes off.

[0184] This aspect enables the first switching element (1) to be subjected to zero-voltage soft switching.

[0185] In the power converter (100; 100A; 100B; 100C; 100E; 100F; 100G) according to the fourth aspect, which can be implemented in combination with the first aspect, the controller (50) is configured to control the third switching element (6; 6A) by defining the timing at which the voltage across the third switching element (6; 6A) becomes equal to or less than a threshold value as the end timing of the ringing period. The controller (50) causes the third switching element (6; 6A) to maintain the on state during the ringing period. The controller (50) causes the third switching element (6; 6A) to become off at the end timing of the ringing period.

[0186] This aspect enables the first switching element (1) to be subjected to zero-voltage soft switching.

[0187] The power converter (100D) according to the fifth aspect, which can be implemented in combination with the first aspect, further includes a third diode (13) and a fourth diode (14). The anode of the third diode (13) is connected to the connection node between the switch (8) and the resonant inductor (LI), and the cathode thereof is connected to the first DC terminal (31). The anode of the fourth diode (14) is connected to the connection node between the switch (8) and the resonant inductor (LI), and the cathode thereof is connected to the second DC terminal (32).

[0188] This aspect enables the control to hold the third switching element (6; 6A) off during the ringing period.

[0189] In the power converter (100; 100A; 100E; 100F) according to the sixth aspect, which can be implemented in combination with any one of the first aspect to the fifth aspect, the power conversion circuit (11) includes a plurality of switching circuits (10). The power converter (100) includes a plurality of switches (8), a plurality of resonant capacitors (9), and a plurality of resonant inductors (LI). The power converter (100) further includes a plurality of AC terminals (41). The plurality of switches (8) are provided one-to-one for the plurality of switching circuits (10). The plurality of switches (8) are each connected to a connection node (3) at which first and second switching elements (1, 2) of a corresponding one of the plurality of switching circuits (10) are connected to each other. The plurality of resonant capacitors (9) are provided one-to-one for the plurality of switches (8). The plurality of resonant capacitors (9) are each connected between a first terminal (81) of a corresponding one of the plurality of switches (8) and a second DC terminal (32). The plurality of resonant inductors (LI) are provided one-to-one for the plurality of switches (8). The plurality of resonant inductors (LI) are each connected to a second terminal (82) of a corresponding one of the plurality of switches (8). The plurality of AC terminals (41) are provided one-to-one for the plurality of switching circuits (10). The plurality of AC terminals (41) are each connected to the connection node (3) between the first and second switching elements (1, 2) of a corresponding one of the plurality of switching circuits (10). The plurality of switches (8) include a plurality of third switching elements (6; 6A) and a plurality of fourth switching elements (7; 7A). The controller (50) controls the plurality of first switching elements (1), the plurality of second switching elements (2), the plurality of third switching elements (6; 6A), and the plurality of fourth switching elements (7; 7A).

[0190] In the power converter (100B; 100C; 100D) according to the seventh aspect, which can be implemented in combination with any one of the first to fifth aspects, the power conversion circuit (11) includes a plurality of switching circuits (10). The power converter (100) includes a plurality of switches (8) and a plurality of resonant capacitors (9). The power converter (100) further includes a plurality of AC terminals (41). The plurality of switches (8) are provided one-to-one for the plurality of switching circuits (10). The plurality of switches (8) are each connected to a connection node (3) between a first switching element (1) and a second switching element (2) of a corresponding switching circuit of the plurality of switching circuits (10). The plurality of resonant capacitors (9) are provided one-to-one for the plurality of switches (8). The plurality of resonant capacitors (9) are each connected between a first terminal (81) of a corresponding switch of the plurality of switches (8) and a second DC terminal (32). The plurality of AC terminals (41) are provided one-to-one for the plurality of switching circuits (10). The plurality of AC terminals (41) are each connected to the connection node (3) between the first switching element (1) and the second switching element (2) of a corresponding switching circuit of the plurality of switching circuits (10). The second terminal (82) of each of the plurality of switches (8) is commonly connected to a resonant inductor (L1). The plurality of switches (8) include a plurality of third switching elements (6; 6A) and a plurality of fourth switching elements (7; 7A). The controller (50) controls the plurality of first switching elements (1), the plurality of second switching elements (2), the plurality of third switching elements (6; 6A), and the plurality of fourth switching elements (7; 7A).

[0191] This aspect makes it possible to reduce the number of resonant inductors (L1) provided to one, thereby contributing to downsizing.

[0192] BRIEF DESCRIPTION OF DRAWINGS

[0193] 1 first switching element

[0194] 2 second switching element

[0195] 3 connection node

[0196] 4 first diode

[0197] 5 second diode

[0198] 6, 6A third switching element

[0199] 7, 7A fourth switching element

[0200] 8 switch

[0201] 81 first terminal

[0202] 82 second terminal

[0203] 9 resonant capacitor

[0204] 10 switching circuit

[0205] 13 third diode

[0206] 14 fourth diode

[0207] 11 power conversion circuit

[0208] 15 regeneration capacitor

[0209] 153 fifth end

[0210] 154 sixth end

[0211] 31 first DC terminal

[0212] 32 second DC terminal

[0213] 41 AC terminal

[0214] 50 controller

[0215] 100, 100A, 100B, 100C, 100D, 100E, 100F, 100G power converter

[0216] iu, iv, iw output current (load current)

[0217] Li resonant inductor

[0218] RA1 AC load

[0219] SU1, SU2, SU6, SU7 control signal

[0220] SV1, SV2, SV6, SV7 control signal

[0221] SW1, SW2, SW6, SW7 control signal

[0222] Td dead time period

[0223] V15 voltage

Claims

1. A power converter comprising: a first DC terminal and a second DC terminal; a power conversion circuit including a switching circuit including: a first switching element and a second switching element connected in series to each other; a first diode connected in antiparallel to the first switching element; and a second diode connected in antiparallel to the second switching element, the first switching element being connected to the first DC terminal in the switching circuit, the second switching element being connected to the second DC terminal in the switching circuit; a switch having a first end and a second end, the first end of the switch being connected to a connection node between the first switching element and the second switching element; a resonance capacitor connected between the first end of the switch and the second DC terminal; a resonance inductor connected to the second end of the switch; a regeneration capacitor connected between the resonance inductor and the second DC terminal; and a controller configured to control the first switching element, the second switching element, and the switch, the switch including: a third switching element configured to cause a current from the resonance inductor to flow therethrough when the third switching element is in an on state; and a fourth switching element configured to cause a current to flow therethrough in a direction opposite to that in the third switching element when the fourth switching element is in an on state, the controller being configured to: apply a control signal having a potential alternated between a high level and a low level to each of the first switching element, the second switching element, the third switching element, and the fourth switching element; set a dead time period between a high-level period of the control signal for the first switching element and a high-level period of the control signal for the second switching element; cause at least a portion of a high-level period of the control signal for the third switching element to overlap with the dead time period; and cause the third switching element to maintain a state immediately before a ringing period during which a voltage across the third switching element rings.

2. The power converter according to claim 1, wherein the controller is configured to cause the third switching element to maintain the on state during the ringing period.

3. The power converter according to claim 1, wherein the controller is configured to cause the third switching element to become off before a timing at which a switching element selected from a group consisting of the first switching element and the second switching element, which is to undergo zero-voltage soft switching, becomes off.

4. The power converter according to claim 1, wherein the controller is configured to control the switch by defining a timing at which a voltage between a first end and a second end of the third switching element becomes equal to or smaller than a threshold value as an end timing of the ringing period, and the controller is configured to: cause the switch to maintain in the on state during the ringing period, and cause the third switching element to become off at the end timing.

5. The power converter according to claim 1, further comprising: a third diode having an anode connected to a connection node between the switch and the resonant inductor; and a cathode connected to the first DC terminal; and a fourth diode having an anode connected to a connection node between the switch and the resonant inductor; and a cathode connected to the second DC terminal.

6. The power converter of any one of claims 1 to 5, wherein the power conversion circuit includes a plurality of the switching circuits, the power converter includes: a plurality of the switches; a plurality of the resonant capacitors; and a plurality of the resonant inductors, the power converter further includes a plurality of AC terminals, the plurality of the switches are provided one-to-one for the plurality of the switching circuits, the plurality of the switches each being connected to a connection node between the first switching element and the second switching element of a respective switching circuit of the plurality of the switching circuits, the plurality of the resonant capacitors are provided one-to-one for the plurality of the switches, the plurality of the resonant capacitors each being connected between the first terminal of a respective switch of the plurality of the switches and the second DC terminal, the plurality of the resonant inductors are provided one-to-one for the plurality of the switches, the plurality of the resonant inductors each being connected to the second terminal of a respective switch of the plurality of the switches, the plurality of the AC terminals are provided one-to-one for the plurality of the switching circuits, the plurality of the AC terminals each being connected to a connection node between the first switching element and the second switching element of a respective switching circuit of the plurality of the switching circuits, the plurality of the switches include the plurality of the third switching elements and the plurality of the fourth switching elements, and the controller is configured to control the plurality of the first switching elements, the plurality of the second switching elements, the plurality of the third switching elements, and the plurality of the fourth switching elements.

7. The power converter of any one of claims 1 to 5, wherein the power conversion circuit includes a plurality of the switching circuits, the power converter includes: a plurality of the switches; and a plurality of the resonant capacitors, the power converter further includes a plurality of AC terminals, the plurality of the switches are provided one-to-one for the plurality of the switching circuits, the plurality of the switches each being connected to a connection node between the first switching element and the second switching element of a respective switching circuit of the plurality of the switching circuits, the plurality of the resonant capacitors are provided one-to-one for the plurality of the switches, the plurality of the resonant capacitors each being connected between the first terminal of a respective switch of the plurality of the switches and the second DC terminal, the plurality of the AC terminals are provided one-to-one for the plurality of the switching circuits, the plurality of the AC terminals each being connected to a connection node between the first switching element and the second switching element of a respective switching circuit of the plurality of the switching circuits, the second terminals of the plurality of the switches are collectively connected to the resonant inductor, the plurality of the switches include the plurality of the third switching elements and the plurality of the fourth switching elements, and the controller is configured to control the plurality of the first switching elements, the plurality of the second switching elements, the plurality of the third switching elements, and the plurality of the fourth switching elements. ​ ​

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