Power conversion device, control device, and control method

Abstract

A power conversion device (101) comprises: circuits (6), (7) that have a plurality of switching legs and are connected in parallel; magnetically coupled reactors (3), (4) that are respectively connected to the circuits (6), (7); and a control circuit (10) that controls switching elements included in the switching legs. The control circuit (10) drives the circuits (6), (7) while changing, for each of the circuits (6), (7), the amplitude of ripple current generated in each winding included in the magnetically coupled reactors (3), (4) on the basis of a phase change in an input voltage input from an AC power supply 1.

Description

Power conversion device, control device, and control method

[0001] The present disclosure relates to a power conversion device, a control device, and a control method for performing power conversion.

[0002] One type of power conversion device has a reactor provided in a switching leg and operates in an interleaved manner. In this power conversion device, reduction of generated heat and loss, reduction of ripple current, etc. are desired.

[0003] The power conversion device described in Patent Document 1 has a magnetic coupling reactor in which a DC winding and a plurality of coupling windings are wound around one magnetic body. In this magnetic coupling reactor, one end of the DC winding is connected to a voltage source and the other end is connected to each one end of the plurality of coupling windings, and each other end of the plurality of coupling windings is connected to each intermediate connection point of a plurality of legs (upper and lower arms) composed of switching elements. This magnetic coupling reactor is configured such that magnetic fluxes generated by currents flowing through the DC winding and the coupling windings merge in the same direction. And in the power conversion device described in Patent Document 1, a control device that controls the switching element drives the upper arm or the lower arm in a phase - drive manner when the duty of the switching operation is less than 0.5, and drives the upper arm or the lower arm in an interleaved manner when the duty is greater than 0.5, thereby suppressing the ripple current and achieving low loss.

[0004] Japanese Patent No. 6636179

[0005] However, in the technology of Patent Document 1 above, when suppressing the winding current flowing through the magnetic coupling reactor in order to reduce the ripple current of the circuit input current, which is the input current to the circuit, the ripple current of the device input current, which is the input current to the power conversion device, increases by the amount of the suppressed winding current, and the loss of the input filter increases. Therefore, for the power conversion device of Patent Document 1, it is necessary to enhance the input filter. Thus, it is difficult for the power conversion device of Patent Document 1 to suppress the ripple current of the device input current while reducing the losses generated in each circuit with a miniaturized device configuration.

[0006] This disclosure has been made in view of the above, and aims to provide a power converter that can reduce losses occurring in each circuit and suppress ripple current of the device input current in a miniaturized device configuration.

[0007] To solve the above-mentioned problems and achieve the objective, the power conversion device of this disclosure comprises a plurality of converter circuits having a plurality of switching legs and connected in parallel, a magnetic coupling reactor connected to each of the converter circuits, and a control circuit for controlling the switching elements included in the switching legs. The control circuit drives the plurality of converter circuits while changing the amplitude of the ripple current generated in each of the windings included in the magnetic coupling reactor for each of the plurality of converter circuits based on the phase change of the input voltage input from the AC power supply.

[0008] The power conversion device described herein has a miniaturized device configuration and offers the effect of suppressing ripple current of the device input current while reducing losses occurring in each circuit.

[0009] Figure 1 shows the circuit configuration of the power converter according to Embodiment 1. Figure 2 shows the configuration of the magnetic coupling reactor in the power converter according to Embodiment 1. Figure 3 shows the configuration of the control circuit in the power converter according to Embodiment 1. Figure 4 explains the waveform of the graph shown in Figure 4. Figure 4 explains the current flowing through the power converter of the comparative example. Figure 4 explains the ripple current in the power converter according to Embodiment 1 and the ripple current in the power converter. Figure 5 shows the processing procedure of the power conversion process performed by the power converter according to Embodiment 1. Figure 6 explains the current flowing through the power converter when the power converter according to Embodiment 2 performs the first control. Figure 7 explains the current flowing through the power converter when the power converter according to Embodiment 2 performs the second control. Figure 8 explains the current flowing through the power converter when the power converter according to Embodiment 3 performs the third control. Figure 9 explains the current flowing through the power converter when the power converter according to Embodiment 3 performs the fourth control. Figure 4 illustrates the current flowing through the power converter when the operation is performed. Figure 5 illustrates the loss in each leg set when the power converter according to Embodiment 4 switches the drive state for each leg set. Figure 6 illustrates the current flowing through the power converter when the type of control method is switched for each drive period. Figure 7 illustrates the loss when the power converter according to Embodiment 4 changes the control method according to the load size. Figure 8 shows a first circuit configuration example of the power converter according to Embodiment 5. Figure 9 shows a second circuit configuration example of the power converter according to Embodiment 5. Figure 10 shows a third circuit configuration example of the power converter according to Embodiment 5. Figure 11 shows a fourth circuit configuration example of the power converter according to Embodiment 5. Figure 12 shows an example of the configuration of the processing circuit when the processing circuit of the control circuit of the power converter according to Embodiments 1 to 5 is implemented with a processor and memory. Figure 13 shows an example of the configuration of the processing circuit when the processing circuit of the control circuit of the power converter according to Embodiments 1 to 5 is implemented with dedicated hardware.

[0010] The power conversion device, control device, and control method according to embodiments of this disclosure will be described in detail below with reference to the drawings.

[0011] Embodiment 1. Figure 1 is a diagram showing the circuit configuration of a power conversion device according to Embodiment 1. The power conversion device 101 converts the AC voltage, which is the power supply voltage applied from the AC power source 1, into DC power, and outputs the converted DC power to an inverter 51 connected in parallel to a smoothing capacitor 8. The inverter 51 converts the DC power into AC voltage and outputs the converted AC voltage to a motor load 52. The AC power source 1 may be a single-phase AC power source or a three-phase AC power source. The power conversion device 101, inverter 51, and motor load 52 are applied to air conditioners and the like.

[0012] The power converter 101 comprises magnetic coupling reactors 3 and 4, converter circuits 6 and 7, a smoothing capacitor 8, and a control circuit 10. The power converter 101 is connected to an AC power source 1 and an inverter 51, and the inverter 51 is connected to a motor load 52.

[0013] Magnetic coupling reactor 3 and magnetic coupling reactor 4 have similar configurations, but in Embodiment 1, they are given different reference numerals for the sake of explanation. Similarly, circuits 6 and 7 have similar configurations, but in Embodiment 1, they are given different reference numerals for the sake of explanation. One of circuits 6 and 7 is the first converter circuit, and the other is the second converter circuit.

[0014] Magnetic coupling reactor 3 is connected to circuit 6, and magnetic coupling reactor 4 is connected to circuit 7. Thus, the power converter 101 has two sets of combinations of magnetic coupling reactors and circuits.

[0015] The AC power supply 1 is connected to magnetic coupling reactors 3 and 4 and circuits 6 and 7. Magnetic coupling reactors 3 and 4 are reactors that integrate multiple reactors into one. Magnetic coupling reactor 3 has a first winding 3a, a second winding 3b, and a third winding 3c. Magnetic coupling reactor 4 has a fourth winding 4a, a fifth winding 4b, and a sixth winding 4c. Winding 3a is the same as winding 4a, winding 3b is the same as winding 4b, and winding 3c is the same as winding 4c.

[0016] Furthermore, the magnetic coupling reactor 3 has four connection terminals 31A, 31B, 31C, and 31D. Terminals 31A, 31B, and 31C are terminals connected to the outside of the magnetic coupling reactor 3, while terminal 31D is a terminal located inside the magnetic coupling reactor 3. Winding 3a is connected to terminals 31A and 31D, winding 3b is connected to terminals 31B and 31D, and winding 3c is connected to terminals 31C and 31D.

[0017] The magnetic coupling reactor 4 has four connection terminals 41A, 41B, 41C, and 41D. Terminals 41A, 41B, and 41C are terminals connected to the outside of the magnetic coupling reactor 4, while terminal 41D is a terminal located inside the magnetic coupling reactor 4. Winding 4a is connected to terminals 41A and 41D, winding 4b is connected to terminals 41B and 41D, and winding 4c is connected to terminals 41C and 41D. Terminals 41A, 41B, 41C, and 41D are the same as terminals 31A, 31B, 31C, and 31D, respectively.

[0018] Terminal 31C is connected to one end of the AC power supply 1, and terminals 31A and 31B are connected to circuit 6. Terminal 41C is connected to one end of the AC power supply 1, and terminals 41A and 41B are connected to circuit 7.

[0019] Circuits 6 and 7 are connected in parallel. Circuit 6 has switching legs LA and LB and one rectifier circuit (rectifier leg). The rectifier circuit of circuit 6 is composed of rectifier elements 61 and 62. In this rectifier circuit, rectifier elements 61 and 62 are connected in series, and the connection point between rectifier elements 61 and 62 is connected to the other end of the AC power supply 1. The cathode of rectifier element 61 is connected to the positive terminal of the smoothing capacitor 8, and the anode of rectifier element 62 is connected to the negative terminal of the smoothing capacitor 8. In circuit 6, the rectifier circuit, leg LA, and leg LB are connected in parallel.

[0020] Circuit 7 has legs LC, LD and one rectifier circuit. The rectifier circuit of circuit 7 is composed of rectifier elements 71 and 72. In this rectifier circuit, rectifier elements 71 and 72 are connected in series, and the connection point between rectifier elements 71 and 72 is connected to the other end of the AC power supply 1. The cathode of rectifier element 71 is connected to the positive terminal of the smoothing capacitor 8, and the anode of rectifier element 72 is connected to the negative terminal of the smoothing capacitor 8. In circuit 7, the rectifier circuit, legs LC, and legs LD are connected in parallel. If circuit 6 is the first converter circuit, legs LA and LB are the first leg set, and legs LC and LD are the second leg set. If circuit 7 is the first converter circuit, legs LC and LD are the first leg set, and legs LA and LB are the second leg set.

[0021] Rectifier elements 71 and 72 are rectifier elements similar to rectifier elements 61 and 62, respectively, and legs LC and LD are legs similar to legs LA and LB. Legs LA, LB, LC, and LD each have two switching elements connected in series. The switching elements in legs LA, LB, LC, and LD are all similar switching elements.

[0022] In the power converter 101, since circuits 6 and 7 are connected in parallel, the current flowing through each switching element in circuits 6 and 7 can be reduced. This reduces the losses (amount of loss) in circuits 6 and 7 and distributes the heat (amount of heat generated). In other words, the power converter 101 can reduce the losses in circuit 6 compared to the case where circuit 6 is present but circuit 7 is not. Note that circuits 6 and 7 may each have four or more even-numbered legs.

[0023] The AC terminal at the connection point of the two switching elements of Leg LA is connected to terminal 31A of the magnetic coupling reactor 3. The AC terminal at the connection point of the two switching elements of Leg LB is connected to terminal 31B of the magnetic coupling reactor 3.

[0024] The AC terminals at the connection point of the two switching elements of the Leg LC are connected to terminal 41A of the magnetic coupling reactor 4. The AC terminals at the connection point of the two switching elements of the Leg LD are connected to terminal 41B of the magnetic coupling reactor 4.

[0025] Circuits 6 and 7 are connected in parallel with inverter 51. Each switching element of legs LA to LD is a switching element having a parasitic diode which is an antiparallel diode, such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) or an IGBT (Insulated Gate Bipolar Transistor), but is not limited to these.

[0026] In circuits 6 and 7, the cathodes of the parasitic diodes of the switching elements of legs LA to LD are connected to the positive terminal of the smoothing capacitor 8, and the anodes are connected to the negative terminal of the smoothing capacitor 8, such that circuits 6 and 7 are connected to the smoothing capacitor 8. The smoothing capacitor 8 smooths the voltage output from circuits 6 and 7.

[0027] In the AC power supply 1, the voltage value Vac of the AC voltage output by the AC power supply 1 is detected by sensor 81, and the voltage value Vac is transmitted to the control circuit 10. In the smoothing capacitor 8, the voltage value Vdc of the DC voltage flowing through the smoothing capacitor 8 is detected by sensor 82, and the voltage value Vdc is transmitted to the control circuit 10. The voltage value Vac is the input voltage value to the power converter 101, and the voltage value Vdc is the output voltage value from the power converter 101. The voltage value Vac detected by sensor 81 contains information about the phase of the AC voltage. Note that in Figure 1, the connection lines between sensor 81 and the control circuit 10, and the connection lines between sensor 82 and the control circuit 10 are not shown.

[0028] In Embodiment 1, the current value of the alternating current input from the AC power source 1 to the power converter 101 is denoted as current value iac. Furthermore, the current value of the alternating current input to the magnetic coupling reactor 4 is denoted as current value iac1, and the current value of the alternating current input to the magnetic coupling reactor 3 is denoted as current value iac2.

[0029] Furthermore, the current value of the alternating current output from terminal 31A of the magnetic coupling reactor 3 is denoted as current value iac3, and the current value of the alternating current output from terminal 31B is denoted as current value iac4. Also, the current value of the alternating current output from terminal 41A of the magnetic coupling reactor 4 is denoted as current value iac5, and the current value of the alternating current output from terminal 41B is denoted as current value iac6.

[0030] In magnetic coupling reactor 3, the current value iac2 is detected by sensor 39 and transmitted to control circuit 10. In magnetic coupling reactor 4, the current value iac1 is detected by sensor 49 and transmitted to control circuit 10. Note that in Figure 1, the connection lines between sensor 39 and control circuit 10, and the connection lines between sensor 49 and control circuit 10 are not shown.

[0031] The control circuit 10 is a circuit that controls the switching elements of legs LA to LD. The control circuit 10 receives the voltage value Vac of the AC voltage detected by the AC power supply 1 and the voltage value Vdc of the DC voltage detected by the smoothing capacitor 8. The control circuit 10 also receives the current value iac2 detected by the magnetic coupling reactor 3 and the current value iac1 detected by the magnetic coupling reactor 4.

[0032] The control circuit 10 determines the number of switching cycles and on-time of the legs LA to LD based on the voltage values ​​Vac, Vdc and current values ​​iac1, iac2, and generates a gate signal (control pulse signal) to control the legs LA to LD. The control circuit 10 controls the operation of the switching elements of the legs LA to LD by transmitting the generated gate signal to the legs LA to LD.

[0033] The control circuit 10 performs switching control to short-circuit the magnetic coupling reactor 3 to the AC power supply 1 using two legs LA and LB. The control circuit 10 also performs switching control to short-circuit the magnetic coupling reactor 4 to the AC power supply 1 using two legs LC and LD.

[0034] Furthermore, the power converter 101 may detect current values ​​iac3 to iac6. Also, the power converter 101 or the AC power supply 1 may detect the current value iac.

[0035] Here, we will describe the configurations of magnetic coupling reactors 3 and 4. Since magnetic coupling reactors 3 and 4 have similar configurations, we will describe the configuration of magnetic coupling reactor 3 here.

[0036] Figure 2 shows the configuration of a magnetic coupling reactor in the power conversion device according to Embodiment 1. The magnetic coupling reactor 3 comprises three windings 3a to 3c and three cores 35d to 35f around which each winding 3a to 3c is swirled. Windings 3a and 3b are coupling windings, and winding 3c is a DC winding.

[0037] In the magnetic coupling reactor 3, a DC winding 3c and multiple coupling windings 3a and 3b are wound around (swirled) a single magnetic material, with coupling winding 3a being swirled around core 35d and coupling winding 3b being swirled around core 35e.

[0038] Furthermore, in the magnetic coupling reactor 3, one end of windings 3a to 3c is connected at terminal 31D. As mentioned above, the other end of winding 3c is connected to one end of the AC power supply 1 via terminal 31C. Also, the other end of winding 3a is connected to the AC terminal of circuit 6 via terminal 31A, and the other end of winding 3b is connected to the AC terminal of circuit 6 via terminal 31B. In this way, one end of winding 3c is connected to one end of windings 3a and 3b, and the other end of winding 3c is connected to the AC power supply 1.

[0039] In the magnetic coupling reactor 3, the other ends of windings 3a and 3b are connected to intermediate connection points of a plurality of upper and lower arms made up of switching elements, and the magnetic flux generated by the currents flowing through winding 3c and windings 3a and 3b is configured to converge in the same direction.

[0040] In Figure 2, the current value of winding 3a is shown by iac3, and the current value of winding 3b is shown by iac4. Also in Figure 2, the direction of the DC magnetic flux 36 and the direction of the AC magnetic flux 37 are indicated by arrows. Note that the direction of the DC magnetic flux 36 and the direction of the AC magnetic flux 37 change due to the switching operation.

[0041] The core shape of the magnetic coupling reactor 3 is, for example, a tripod shape such as an EE type or EI type. Winding 3a is wound around the side leg 38d of core 35d, and winding 3b is wound around the side leg 38e of core 35e, so as to cancel each other out in terms of DC magnetic flux 36, forming a coupling reactor. Winding 3c is wound around the central leg 38f of core 35f in a direction that reinforces the magnetic flux of windings 3a and 3b, forming a DC reactor. A gap is provided at the central leg 38f of core 35f to prevent DC magnetic flux saturation. This gap also adjusts the degree of coupling of the coupling reactor and the degree of coupling between the coupling reactor and the DC reactor. The magnetic coupling reactor 3 may also have a structure that cancels out AC magnetic flux 37 leaking from the gap.

[0042] The direct magnetic flux 36 is generated so as to converge on the central leg 38f of the core 35f, and its direction does not change as long as the power transmission direction remains unchanged. On the other hand, the alternating magnetic flux 37 changes direction each time the switching element switches so as to circulate through the side legs 38d and 38e of the cores 35d and 35e. At the central leg 38f of the core 35f, this circulating alternating magnetic flux 37 is always in the opposite direction and thus canceled out.

[0043] In this way, in the magnetic coupling reactor 3, the windings 3a and 3b are swiveled so as to be AC-coupled. Therefore, magnetic fluxes are induced in the core 35d around which the winding 3a is swiveled and in the core 35e around which the winding 3b is swiveled in directions corresponding to the operation of the circuit 6. In the core 35f around which the winding 3c is swiveled, a magnetic flux is induced in a direction corresponding to the polarity of the AC power supply 1. Note that the magnetic coupling reactors 3 and 4 are not limited to the above-described configuration, and other configurations may be used.

[0044] FIG. 3 is a diagram showing the configuration of a control circuit included in the power conversion device according to Embodiment 1. The control circuit 10 includes a control operation determiner 11, an output voltage controller 12, a carrier generator 13, and gate signal generators 14A, 14B, 14C, and 14D.

[0045] The control circuit 10 receives the current value iac1 of the alternating current input to the magnetic coupling reactor 4, which is detected by the magnetic coupling reactor 4. Further, the control circuit 10 receives the current value iac2 of the alternating current input to the magnetic coupling reactor 3, which is detected by the magnetic coupling reactor 3.

[0046] Further, the control circuit 10 receives the voltage value Vac of the alternating voltage output by the AC power supply 1, which is detected by the sensor 81. Also, the control circuit 10 receives the voltage value Vdc of the direct current voltage flowing through the smoothing capacitor 8, which is detected by the sensor 82. The control circuit 10 transmits the current values iac1 and iac2 and the voltage values Vac and Vdc to the output voltage controller 12. Further, the control circuit 10 transmits the current values iac1 and iac2 and the voltage value Vac to the control operation determiner 11.

[0047] The control operation determination unit 11 is a controller that calculates the command value of the output voltage output from circuits 6 and 7, and also calculates carrier waveform information for controlling the switching by the switching element.

[0048] The control operation determination unit 11 detects the phase of the input voltage from the AC power supply 1 to the power converter 101 based on the voltage value Vac. The control operation determination unit 11 also detects the circuit ripple current, which is the ripple current of circuits 6 and 7. Specifically, the control operation determination unit 11 detects the circuit ripple current of circuit 7 based on the current value iac1 and the circuit ripple current of circuit 6 based on the current value iac2. The circuit ripple current of circuit 7 is the ripple current with current value iac1, and the circuit ripple current of circuit 6 is the ripple current with current value iac2.

[0049] The control operation determination unit 11 calculates the output voltage command value, which is the command value of the voltage output from circuits 6 and 7, and the carrier waveform information, which is information about the carrier waveform, based on the phase of the input voltage to the power converter 101 and the circuit ripple current of circuits 6 and 7.

[0050] Furthermore, the control operation determination device 11 may change the control method based on the magnitude of the load driven by the power converter 101. A control method corresponding to the magnitude of the load will be described in Embodiment 4.

[0051] The carrier waveform information includes information for generating duty cycle signals to control the switching of circuits 6 and 7, and information for generating carrier signals to operate legs LA to LD.

[0052] Specifically, the carrier waveform information includes information indicating whether the currents input to legs LA and LB are in phase or out of phase, and information indicating whether the currents input to legs LC and LD are in phase or out of phase. The carrier waveform information also includes information indicating whether or not to change the frequency of the currents input to legs LA and LB, and information indicating whether or not to change the frequency of the currents input to legs LC and LD. The control operation determination unit 11 transmits a selection signal indicating the output voltage command value to the output voltage controller 12 and a selection signal indicating the carrier waveform information to the carrier generator 13.

[0053] The output voltage controller 12 is a controller that generates a duty cycle signal for the gate signal (gate drive signal) based on current values ​​ia1, ia2, voltage values ​​Vac, Vdc, and output voltage command value.

[0054] The output voltage controller 12 generates a duty cycle signal to control the output voltage from the power converter 101 to the output voltage command value, while controlling the power factor of the current waveforms of current values ​​iac1 and iac2 to 1. The duty cycle signal generated by the output voltage controller 12 is the duty cycle signal of the gate signal used when driving the gate of the switching element.

[0055] The output voltage controller 12 generates a duty cycle signal for each of the gate signal generators 14A to 14D and transmits the duty cycle signals to the gate signal generators 14A to 14D. The duty cycle signal to gate signal generator 14A is the duty cycle signal for operating leg LA, and the duty cycle signal to gate signal generator 14B is the duty cycle signal for operating leg LB. The duty cycle signal to gate signal generator 14C is the duty cycle signal for operating leg LC, and the duty cycle signal to gate signal generator 14D is the duty cycle signal for operating leg LD.

[0056] The carrier generator 13 is a controller that generates a carrier signal for each of the gate signal generators 14A to 14D to operate each of the legs LA to LD, and transmits the carrier signal to the gate signal generators 14A to 14D.

[0057] The carrier generator 13 generates carrier signals based on carrier waveform information. The carrier signal to gate signal generator 14A is the carrier signal for operating leg LA, and the carrier signal to gate signal generator 14B is the carrier signal for operating leg LB. Furthermore, the carrier signal to gate signal generator 14C is the carrier signal for operating leg LC, and the carrier signal to gate signal generator 14D is the carrier signal for operating leg LD.

[0058] Based on the carrier waveform information, the carrier generator 13 determines whether to delay the carrier phase by 180 degrees for each leg or to what extent to set the frequency, and generates and outputs the carrier signals for each leg LA to LD.

[0059] Each gate signal generator 14A to 14D generates a gate signal based on the duty cycle signal received from the output voltage controller 12 and the carrier signal received from the carrier generator 13, and transmits the gate signal to the legs LA to LD. The gate signal generators 14A to 14D compare the duty cycle signal and the carrier signal and generate a pulse signal indicating "0" or "1" as the gate signal based on the comparison result. Specifically, the gate signal generators 14A to 14D generate a pulse signal indicating "1" when the magnitude of the duty cycle signal is greater than the magnitude of the carrier signal, and generate a pulse signal indicating "0" when the magnitude of the duty cycle signal is less than or equal to the magnitude of the carrier signal. The gate signal generators 14A to 14D input the generated pulse signals to the gates of the switching elements of the legs LA to LD.

[0060] The gate signal generator 14A generates a gate signal to control leg LA and transmits it to leg LA, and the gate signal generator 14B generates a gate signal to control leg LB and transmits it to leg LB. In addition, the gate signal generator 14C generates a gate signal to control leg LC and transmits it to leg LC, and the gate signal generator 14D generates a gate signal to control leg LD and transmits it to leg LD. As a result, the control circuit 10 controls the switching of legs LA to LD by the gate signals.

[0061] The control circuit 10 of Embodiment 1 changes the amplitude of the ripple current generated in the windings 3a-3c and 4a-4c of the magnetic coupling reactors 3 and 4 based on the phase change of the input voltage to the power converter 101. The ripple current generated in windings 3a-3c corresponds to the circuit ripple current in circuit 6, and the ripple current generated in windings 4a-4c corresponds to the circuit ripple current in circuit 7.

[0062] The control circuit 10 suppresses the range of change in the device input current, which is the input current to the power converter 101, to a specific value (for example, 5%) or less by changing the amplitude of each winding current. In other words, the control circuit 10 controls the range of change in the ripple current of the device input current (device input ripple current) relative to the overall amplitude by changing the amplitude of the ripple current of each winding current, so that it is less than or equal to a specific value. The range of change in the device input ripple current is the ratio of the amplitude of the device input ripple current to the amplitude of the device input current.

[0063] In Embodiment 1, driving a large amplitude of winding ripple current may be referred to as driving a large amplitude of current to circuits 6 and 7.

[0064] The control circuit 10 increases the cancellation effect of the ripple current between legs LA and LD by changing the amplitude of the winding ripple current in accordance with the phase change of the input voltage from the AC power supply 1 to the power converter 101. As a result, the range of change in the ripple current of the device input current becomes less than a specific value. In addition, the power converter 101 can suppress the ripple of the device input current and the circuit input current, thereby suppressing the generation of harmonics.

[0065] Furthermore, the power converter 101 distributes the legs that drive the switching elements between legs LA and LD by changing the ripple current of each switching element. This allows the power converter 101 to distribute the losses, heat generation, and noise in circuits 6 and 7, thereby thermally averaging them out. In circuits 6 and 7, heat generation is suppressed by suppressing losses, and heat generation is suppressed by suppressing noise. The power converter 101 suppresses losses and noise by distributing them in circuits 6 and 7, and thereby suppresses heat generation.

[0066] The power converter 101, for example, changes the ripple current of each switching element to reduce the ripple current of legs LA and LB for a certain period, thereby suppressing losses, heat generation, and noise in legs LA and LB, and to reduce the ripple current of legs LC and LD for a certain period, thereby suppressing losses, heat generation, and noise in legs LC and LD. The power converter 101 repeats these processes to distribute losses, heat generation, and noise in circuits 6 and 7.

[0067] Figure 4 is a diagram illustrating the current flowing through the power converter according to Embodiment 1. Figure 5 is a diagram illustrating the waveform of the graph shown in Figure 4. In the graph shown in Figure 4, the horizontal axis represents time, and the vertical axis represents current.

[0068] Waveform W1 shown in Figure 5 is an enlarged portion of the current waveform in the third row from the top in Figure 4. Waveform W2 is an enlarged portion of waveform W1, and waveform W3 is an enlarged portion of waveform W2.

[0069] Waveforms W1 to W3 in Figure 5 represent the current values ​​iac3 and iac4 in legs LA and LB, respectively. Of the waveforms W1 to W3, periods with a large amplitude of ripple current correspond to periods when reverse-phase drive is performed in legs LA and LB, periods with a low switching frequency, etc., while periods with a small amplitude of ripple current correspond to periods when common-phase drive is performed in legs LA and LB, periods with a high switching frequency, etc.

[0070] Each waveform shown in Figure 4 has various amplitudes, similar to waveforms W1 to W3 in Figure 5. However, because the waveforms detected over a long period of time have been compressed and shown, adjacent waveforms are touching. In each waveform shown in Figure 4, the thicker parts indicate areas where the ripple current amplitude is large.

[0071] In the graphs shown in Figure 4, the first graph from the top represents the current (device input current) input from the AC power source 1 to the power converter 101, and corresponds to the current value iac.

[0072] In the graphs shown in Figure 4, the second graph from the top shows the current input to circuit 6 (circuit input current) and the current input to circuit 7. The current value of the circuit input current flowing through circuit 6 is current value iac2, and the current value of the circuit input current flowing through circuit 7 is current value iac1.

[0073] In Figure 4, the current value iac1 is shown as a light-colored waveform, and the current value iac2 is shown as a dark-colored waveform. Only the portion of the current value iac1 waveform that does not overlap with the current value iac2 waveform is shown.

[0074] The current value iac2 in circuit 6 corresponds to the current value input to the magnetic coupling reactor 3, and the current value iac1 in circuit 7 corresponds to the current value input to the magnetic coupling reactor 4.

[0075] In the graphs shown in Figure 4, the third graph from the top shows the first winding current input to circuit 6 from winding 3a of the magnetic coupling reactor 3 and the first winding current input to circuit 6 from winding 3b of the magnetic coupling reactor 3. The current value of the first winding current input to circuit 6 from winding 3a is current value iac3, and the current value of the first winding current input to circuit 6 from winding 3b is current value iac4.

[0076] In Figure 4, the current value iac3 is shown as a light-colored waveform, and the current value iac4 is shown as a dark-colored waveform. The amplitude of the waveform for current value iac4 is approximately the same as the amplitude of the waveform for current value iac3. In the waveforms of current values ​​iac3 and iac4, there are periods when the phases of current values ​​iac3 and iac4 are the same (in-phase drive period) and periods when they are 180 degrees apart (out-of-phase drive period). The period when the amplitude of the ripple current of current values ​​iac3 and iac4 is large is the out-of-phase drive period when out-of-phase drive is performed between legs LA and LB, and the period when the amplitude of the ripple current is small is the in-phase drive period when in-phase drive is performed between legs LA and LB. In Figure 4, only the portion of the waveform for current value iac4 that does not overlap with the waveform for current value iac3 is shown. During the in-phase drive period, the portion where the waveforms for current value iac3 and current value iac4 do not overlap represents the error caused by the simulation.

[0077] In the graphs shown in Figure 4, the fourth graph from the top shows the second winding current input to the circuit 7 from winding 4a of the magnetic coupling reactor 4, and the second winding current input to the circuit 7 from winding 4b of the magnetic coupling reactor 4. The current value of the second winding current input to the circuit 7 from winding 4a is current value iac5, and the current value of the second winding current input to the circuit 7 from winding 4b is current value iac6.

[0078] In Figure 4, the current value iac5 is shown as a light-colored waveform, and the current value iac6 is shown as a dark-colored waveform. The amplitude of the waveform for current value iac6 is approximately the same as the amplitude of the waveform for current value iac5. In the waveforms of current values ​​iac5 and iac6, there are in-phase drive periods where the phases of current values ​​iac5 and iac6 are the same, and out-of-phase drive periods where they are shifted by 180 degrees. The period when the amplitude of the ripple current of current values ​​iac5 and iac6 is large is the out-of-phase drive period when out-of-phase drive is performed between the leg LC and LD, and the period when the amplitude of the ripple current is small is the in-phase drive period when in-phase drive is performed between the leg LC and LD. In Figure 4, only the portion of the waveform for current value iac6 that does not overlap with the waveform for current value iac5 is shown. During the in-phase drive period, the portion where the waveforms for current value iac5 and current value iac6 do not overlap represents the error caused by the simulation.

[0079] In the second graph from the top, the current value iac2 in circuit 6 is a waveform obtained by combining the waveforms of current value iac3 and current value iac4. Similarly, in the second graph from the top, the current value iac1 in circuit 7 is a waveform obtained by combining the waveforms of current value iac5 and current value iac6. Furthermore, the current value iac input to the power converter 101 shown in the first graph from the top is a waveform obtained by combining the waveforms of current value iac1 and current value iac2.

[0080] The waveforms of current values ​​iac3 and iac4 show periods of large ripple current (periods with large amplitude) and periods of small ripple current (periods with small amplitude). Periods with large ripple current amplitude include periods when reverse-phase drive is performed between legs LA and LB, and periods with low switching frequencies. Periods with large ripple current amplitude include periods when common-phase drive is performed between legs LA and LB, and periods with high switching frequencies.

[0081] In other words, the period during which the amplitude of the ripple currents iac3 and iac4 is large is, for example, the period during which reverse-phase drive is performed between legs LA and LB. During this period, the waveforms of currents iac3 and iac4 are added together in opposite phases and weaken each other, so the amplitude of the composite wave of currents iac3 and iac4, iac2, becomes small, about half the amplitude.

[0082] Furthermore, during periods when the amplitude of the ripple currents iac3 and iac4 is small, for example, in-phase drive is being performed between legs LA and LB. During these periods, the waveforms of iac3 and iac4 are added together in phase and reinforce each other. As a result, the amplitude of iac2, which is the composite wave of iac3 and iac4, becomes about twice as large as that of iac3 or iac4.

[0083] Similarly, the waveforms of current values ​​iac5 and iac6 show periods of large ripple current (periods with large amplitude) and periods of small ripple current (periods with small amplitude). Periods with large ripple current amplitude include periods when reverse-phase drive is performed between the leg LC and LD, and periods with low switching frequencies. Periods with large ripple current amplitude include periods when common-phase drive is performed between the leg LC and LD, and periods with high switching frequencies.

[0084] In other words, the period during which the amplitude of the ripple currents iac5 and iac6 is large corresponds to a period during which, for example, reverse-phase drive is being performed between the leg LC and LD. During this period, the waveforms of currents iac5 and iac6 are added together in opposite phases, causing them to cancel each other out. As a result, the amplitude of the combined wave of currents iac5 and iac6, iac1, becomes approximately half the amplitude.

[0085] Furthermore, during periods when the amplitude of the ripple currents iac5 and iac6 is small, for example, in-phase drive is being performed between the leg LC and LD. During these periods, the waveforms of currents iac5 and iac6 are added together in phase and reinforce each other. As a result, the amplitude of current iac1, which is the composite wave of currents iac5 and iac6, becomes about twice as large as that of current iac5 or iac6.

[0086] In the control circuit 10 of Embodiment 1, during periods when current values ​​iac3 and iac4 are added together in opposite phases to weaken each other (such as the reverse-phase drive period), current values ​​iac5 and iac6 are added together in the same phase by in-phase drive or the like to reinforce each other. That is, during periods when the amplitudes of current values ​​iac3 and iac4 are large, such as the reverse-phase drive period, the control circuit 10 reduces the amplitudes of current values ​​iac5 and iac6 by in-phase drive or the like. As a result, during periods when current values ​​iac3 and iac4 are added together in opposite phases, the amplitude of current value iac2 becomes about half its original value, and the amplitude of current value iac1 becomes about twice the value of current values ​​iac5 and iac6.

[0087] On the other hand, during periods when current values ​​iac3 and iac4 are added together in phase to reinforce each other (such as in-phase drive periods), the control circuit 10 adds current values ​​iac5 and iac6 together in opposite phases to destructively cancel each other out. In other words, during in-phase drive periods when the amplitudes of current values ​​iac3 and iac4 are small, the control circuit 10 increases the amplitudes of current values ​​iac5 and iac6 by driving in opposite phases. As a result, during periods when current values ​​iac3 and iac4 are added together in phase, the amplitude of current value iac2 becomes about twice the value of current values ​​iac3 and iac4, and current value iac1 becomes about half the value.

[0088] The control circuit 10 reverses the drive state of a pair of legs LA and LB (even number, 2 in Embodiment 1) and the drive state of a pair of legs LC and LD (even number, 2 in Embodiment 1) at specific periodic timings corresponding to the phase change of the input voltage. That is, the control circuit 10 reverses the drive state between the pairs of legs by performing a drive with a large current amplitude on one pair of legs and a drive with a small current amplitude on the other pair of legs. When the control circuit 10 changes one pair of legs from a drive with a large current amplitude to a drive with a small current amplitude, it also changes the other pair from a drive with a small current amplitude to a drive with a large current amplitude. At specific periodic intervals, the control circuit 10 changes one pair of legs from a drive with a large current amplitude to a drive with a small current amplitude, and at the same time changes the other pair from a drive with a small current amplitude to a drive with a large current amplitude.

[0089] As a result, during periods when the amplitude of current value iac1 is approximately twice that of current value iac5 or current value iac6, the amplitude of current value iac2 becomes a small value of about half. On the other hand, during periods when the amplitude of current value iac1 is a small value of about half, the amplitude of current value iac2 becomes approximately twice that of current value iac3 or current value iac4. In other words, in each period, one of the current values ​​iac1 or iac2 becomes approximately twice that of current values ​​iac3 to iac6, while the other becomes a small value of about half. To put it another way, in each period, the ripple current of one of the current values ​​iac1 or iac2 becomes approximately twice that of the ripple current of current values ​​iac3 to iac6, while the other becomes a small value of about half.

[0090] Here, for the sake of explanation, we will describe the current values ​​iac1 to iac6 assuming that simulation errors are ignored. Among the current values ​​iac3 to iac6, let Y1 be the amplitude during the period when the current value or ripple current amplitude is small, and Y be the amplitude during the period when the amplitude is large. x Let Y1 be the amplitude of the current values ​​iac3 and iac4 when in-phase drive is performed on legs LA and LB, and Y1 be the amplitude of the current values ​​iac3 and iac4 when reverse-phase drive is performed. xSimilarly, when in-phase drive is performed on the legs LC and LD, the amplitudes of the current values ​​iac5 and iac6 are Y1, and when out-of-phase drive is performed, the amplitudes of the current values ​​iac5 and iac6 are Y x Let's assume that.

[0091] In this case, during periods when current values ​​iac3 and iac4 mutually enhance each other's displacement (such as the in-phase drive period), the amplitude of the combined current value iac2 is 2Y1. Conversely, during periods when current values ​​iac3 and iac4 mutually de-escalate each other (such as the out-of-phase drive period), the amplitude of the combined current value iac2 becomes a small value of about half its original value (here, this is denoted as Y0).

[0092] Similarly, during periods when current values ​​iac5 and iac6 mutually enhance each other's displacement (such as in-phase drive periods), the amplitude of the combined current value iac1 is twice that of Y1, which is 2Y1. Also, during periods when current values ​​iac5 and iac6 mutually de-escalate each other (such as out-of-phase drive periods), the amplitude of the combined current value iac1 is approximately half that of Y0.

[0093] As mentioned above, the current value iac shown in the first graph from the top is a waveform obtained by combining the waveform of current value iac1 and the waveform of current value iac2. In the power converter 101, at any given time, either current value iac1 or iac2 becomes Y0, which is about half its original value, and the other becomes 2Y1. As a result, the amplitude (ripple current of the device input current) of the combined current value iac, which is obtained by combining current values ​​iac1 and iac2, becomes smaller at all times, and the power converter 101 can suppress the ripple current of current value iac.

[0094] Thus, the control circuit 10 of Embodiment 1 drives circuits 6 and 7 while changing the amplitude of the ripple current generated in the windings 3a to 3c and 4a to 4c of the magnetic coupling reactors 3 and 4, in accordance with the phase change of the input voltage to the power converter 101, so as to suppress the device input ripple current.

[0095] In other words, the power converter 101 drives the leg LC and LD such that the amplitude of current value iac1, which is a composite wave of current values ​​iac3 and iac4, decreases during periods when the amplitude of current value iac2, which is a composite wave of current values ​​iac3 and iac4, increases. Also, the power converter 101 drives the leg LC and LD such that the amplitude of current value iac1, which is a composite wave of current values ​​iac5 and iac6, increases during periods when the amplitude of current value iac2, which is a composite wave of current values ​​iac3 and iac4, decreases. As a result, a large cancellation effect of the ripple current (current value iac) input to the power converter 101 can be obtained.

[0096] As a result, the ripple current of the current value iac input to the power converter 101 (the ripple current of the device input current) is suppressed. The control circuit 10 can suppress the range of change in the ripple current of the current value iac to 5% or less by controlling, for example, the amplitude of the current flowing through legs LA to LD.

[0097] Furthermore, in the power converter 101, since circuits 6 and 7 are connected in parallel, the current flowing through each switching element in circuits 6 and 7 can be reduced. As a result, losses and heat generation are distributed in circuits 6 and 7, reducing losses and heat generation.

[0098] Figure 6 is a diagram illustrating the current flowing through the comparative example power converter. In the graph shown in Figure 6, the horizontal axis represents time, and the vertical axis represents current. The comparative example power converter (hereinafter referred to as the comparative power converter) is a power converter described in Patent Document 1, in which two sets of integrated magnetic components and converter circuits are arranged.

[0099] The graph of current flowing through the comparative power converter shown in Figure 6 corresponds to the graph of current flowing through the power converter 101 shown in Figure 4. Specifically, the first row of graphs from the top in Figure 6 represents the current value iacX, which corresponds to the current value iac. The second row of graphs from the top in Figure 6 represents the current values ​​iac1X and iac2X, which correspond to the current values ​​iac1 and iac2. The third row of graphs from the top in Figure 6 represents the current values ​​iac3X and iac4X, which correspond to the current values ​​iac3 and iac4. The fourth row of graphs from the top in Figure 6 represents the current values ​​iac5X and iac6X, which correspond to the current values ​​iac5 and iac6.

[0100] In the case of the comparative power converter, the current values ​​iac3X and iac4X are the same as the current values ​​iac3 and iac4, and the current values ​​iac5X and iac6X are also the same as the current values ​​iac3 and iac4. Therefore, the third and fourth graphs shown in Figure 6 are the same as the third graph shown in Figure 4. Also, the graphs for current values ​​iac1X and iac2X shown in Figure 6 are the same as the graphs for current values ​​iac1 and iac2 shown in Figure 4.

[0101] When the comparative power converter drives the legs corresponding to current values ​​iac3X and iac4X in phase, it also drives the legs corresponding to current values ​​iac5X and iac6X in phase. Similarly, when the comparative power converter drives the legs corresponding to current values ​​iac3X and iac4X in opposite phase, it also drives the legs corresponding to current values ​​iac5X and iac6X in opposite phase. Therefore, in the comparative power converter, when current values ​​iac3X and iac4X reinforce each other, current values ​​iac5X and iac6X also reinforce each other, and when current values ​​iac3X and iac4X are added in opposite phase, current values ​​iac5X and iac6X are also added in opposite phase.

[0102] Thus, in the comparative power converter, the period during which current values ​​iac3X and iac4X reinforce each other is the same as the period during which current values ​​iac5X and iac6X reinforce each other. During this period, the current value iac2X, which is a combination of current values ​​iac3X and iac4X, and the current value iac1X, which is a combination of current values ​​iac5X and iac6X, reinforce each other. Therefore, during the period during which current values ​​iac3X and iac4X reinforce each other (the period during which current values ​​iac5X and iac6X reinforce each other), the device ripple current, which is the current value iacX, a combination of current values ​​iac1X and iac2X, becomes large. As a result, the ripple current in the comparative power converter becomes larger than the ripple current in the power converter 101.

[0103] Figure 7 is a diagram illustrating the ripple current in the power converter according to Embodiment 1 and the ripple current in the comparison power converter. In the graph shown in Figure 7, the horizontal axis represents time and the vertical axis represents current.

[0104] In a comparative power converter, there are periods when current values ​​iac1X and iac2X reinforce each other, resulting in periods where the ripple current of the device's input current increases. For example, during the period when current values ​​iac3X and iac4X are driven in phase, current values ​​iac3X and iac4X reinforce each other, so current value iac2X has twice the amplitude of iac3X. Similarly, during the period when current values ​​iac5X and iac6X are driven in phase, current values ​​iac5X and iac6X reinforce each other, so current value iac1X has twice the amplitude of iac5X. Furthermore, since the period during which current values ​​iac3X and iac4X are driven in phase is the same as the period during which current values ​​iac5X and iac6X are driven in phase, the period during which current value iac2X has twice the amplitude of iac current value 3X is the same as the period during which iac1X has twice the amplitude of iac5X. During this period, current values ​​iac1X and iac2X reinforce each other, resulting in an amplitude twice that of current value iac1X, or four times that of current value iac3X, thus increasing the ripple current of the device input current.

[0105] On the other hand, in the case of the power converter 101, as described above, one of the current values ​​iac1 and iac2 becomes Y0, which is about half the original value, and the other becomes 2Y1. Therefore, the combined current value iac, which is the sum of the current values ​​iac1 and iac2, results in a smaller ripple current of the device input current throughout the entire period.

[0106] Figure 8 is a flowchart showing the processing procedure of the power conversion process performed by the power conversion device according to Embodiment 1. The control circuit 10 of the power conversion device 101 receives the device input voltage, which is the input voltage to the power conversion device 101, from the sensor 81. That is, the control circuit 10 receives the voltage value Vac of the AC voltage detected by the sensor 81 from the sensor 81. Based on the voltage value Vac, the control circuit 10 detects the phase of the device input voltage (step S10).

[0107] The control circuit 10 performs a drive step (step S20) that changes the amplitude of the winding current based on the detected phase. Specifically, the control circuit 10 changes the amplitude of the winding current for the parallel circuits 6 and 7 such that the amplitude of the ripple current in circuit 7 decreases when the amplitude of the ripple current in circuit 6 is large, and increases the amplitude of the ripple current in circuit 7 when the amplitude of the ripple current in circuit 6 is small. In other words, the control circuit 10 changes the amplitude of the winding current such that the amplitude of the current value iac1, which is a combination of current values ​​iac5 and iac6, decreases when the amplitude of the current value iac2, which is a combination of current values ​​iac3 and iac4, is large. Also, the control circuit 10 changes the amplitude of the winding current such that the amplitude of the current value iac1, which is a combination of current values ​​iac5 and iac6, increases when the amplitude of the current value iac2, which is a combination of current values ​​iac3 and iac4, is small. As a result, the control circuit 10 can suppress the ripple current of the current value iac, which corresponds to the device input ripple current, obtained by combining the current values ​​iac1 and iac2.

[0108] As described above, the power converter 101 of the first embodiment includes two circuits 6 and 7, a magnetic coupling reactor 3 connected to circuit 6, and a magnetic coupling reactor 4 connected to circuit 7. The power converter 101 drives circuits 6 and 7 while changing the amplitude of the ripple current generated in the windings 3a to 3c and 4a to 4c of the magnetic coupling reactors 3 and 4 for each of the circuits 6 and 7, so that the ripple current of the device input current is suppressed in accordance with the phase change of the device input voltage to the power converter 101.

[0109] As a result, the power converter 101 can suppress the ripple current of the device input current. Furthermore, since circuits 6 and 7 are connected in parallel in the power converter 101, the current flowing through each switching element in circuits 6 and 7 can be reduced. This distributes losses and heat generation in the power converter 101.

[0110] Furthermore, the power converter 101 can suppress the ripple current of the device input current, thereby reducing losses in the input filter and suppressing the generation of harmonics. As a result, there is no need to enhance the input filter for the power converter 101, and the power converter 101 can suppress the ripple current of the device input current while reducing losses in circuits 6 and 7 with a compact device configuration.

[0111] Embodiment 2. Next, Embodiment 2 will be described using Figures 9 and 10. In Embodiment 2, the power converter 101 changes the phase of each circuit's leg to either in-phase or out-of-phase in accordance with the phase of the input voltage, so as to suppress the ripple current of the device's input current.

[0112] The power converter 101 of Embodiment 2 has the same configuration as the power converter 101 of Embodiment 1. In Embodiment 2, the control method by the control circuit 10 differs from the control method in Embodiment 1.

[0113] Figure 9 is a diagram illustrating the current flowing through the power converter when the power converter according to Embodiment 2 performs the first control. In the graph shown in Figure 9, the horizontal axis represents time, and the vertical axis represents current. Note that Figure 9 does not show graphs showing the current input to circuit 6 and the current input to circuit 7. The first control is a control in which one of circuits 6 and 7 is driven in phase, and the other is driven in opposite phase.

[0114] When the control circuit 10 performs the first control, it uses in-phase drive and out-of-phase drive depending on whether it is circuit 6 or circuit 7. That is, the control circuit 10 performs in-phase drive and out-of-phase drive according to circuits 6 and 7. For example, when the control circuit 10 performs in-phase drive on legs LA and LB of circuit 6, it performs out-of-phase drive on legs LC and LD of circuit 7. On the other hand, when the control circuit 10 performs out-of-phase drive on legs LA and LB of circuit 6, it performs in-phase drive on legs LC and LD of circuit 7.

[0115] In the graphs shown in Figure 9, the second graph from the top shows the current values ​​iac3 and iac4 of the first winding current when the control circuit 10 performs in-phase drive P1 on legs LA and LB of circuit 6 for a period of time T0 to T1.

[0116] In the graphs shown in Figure 9, the third graph from the top shows the current values ​​iac5 and iac6 of the second winding current when the control circuit 10 performs reverse-phase drive P2 on the legs LC and LD of circuit 7 for a period of time T0 to T1. In this way, the control circuit 10 drives either circuit 6 or circuit 7 in phase and the other in reverse phase.

[0117] In the graphs shown in Figure 9, the first graph from the top, similar to the first graph from the top in Figure 4, shows the current value iac of the current input from the AC power source 1 to the power converter 101. The waveform of the first graph from the top in Figure 9 is a combined waveform of current values ​​iac3 to iac6.

[0118] Figure 10 is a diagram illustrating the current flowing through the power converter when the power converter according to Embodiment 2 performs the second control. In the graph shown in Figure 10, the horizontal axis represents time and the vertical axis represents current. Note that Figure 10 does not show graphs showing the current input to circuit 6 and the current input to circuit 7. The second control is a control that switches between in-phase drive and out-of-phase drive at specific periods (for example, every 1 period, every 2 periods, etc.) while driving either circuit 6 or 7 in phase and the other in opposite phase.

[0119] In Figure 10, the timing of a phase of 0 degrees is shown at time T2, the timing of a phase of 45 degrees is shown at time T3, the timing of a phase of 135 degrees is shown at time T4, and the timing of a phase of 180 degrees (0 degrees) is shown at time T5.

[0120] When the control circuit 10 performs the second control, it drives circuits 6 and 7 while switching between in-phase drive and out-of-phase drive according to the phase of the input voltage to the power converter 101. For example, while the control circuit 10 is performing in-phase drive on legs LA and LB of circuit 6, it performs out-of-phase drive on legs LC and LD of circuit 7. On the other hand, while the control circuit 10 is performing out-of-phase drive on legs LA and LB of circuit 6, it performs in-phase drive on legs LC and LD of circuit 7.

[0121] When the control circuit 10 changes the direction of the legs LA and LB from in-phase drive to out-of-phase drive, it also changes the direction of the legs LC and LD from out-of-phase drive to in-phase drive. On the other hand, when the control circuit 10 changes the direction of the legs LA and LB from out-of-phase drive to in-phase drive, it also changes the direction of the legs LC and LD from in-phase drive to out-of-phase drive.

[0122] In the graphs shown in Figure 10, the second graph from the top shows the current values ​​iac3 and iac4 when the control circuit 10 performs reverse-phase drive P2 on legs LA and LB of circuit 6 between times T2 and T3, performs in-phase drive P1 between times T3 and T4, and performs reverse-phase drive P2 again between times T4 and T5.

[0123] In the graphs shown in Figure 10, the third graph from the top shows the current values ​​iac5 and iac6 when the control circuit 10 performs in-phase drive P1 on the legs LC and LD of circuit 7 between times T2 and T3, performs reverse-phase drive P2 between times T3 and T4, and performs in-phase drive P1 again between times T4 and T5.

[0124] In the graphs shown in Figure 10, the first graph from the top, similar to the first graph from the top in Figure 4, shows the current value iac of the current input from the AC power source 1 to the power converter 101.

[0125] The control circuit 10 simultaneously performs in-phase and out-of-phase drive switching for legs LA and LB, and out-of-phase and in-phase drive switching for legs LC and LD. Figure 10 shows the case where the control circuit 10 switches between in-phase and out-of-phase drive at timings of 45 degrees and 135 degrees in the input voltage phase. Note that the control circuit 10 may perform the switching between in-phase and out-of-phase drive for legs LA to LD at any timing.

[0126] Furthermore, the control circuit 10 averages the drive periods of in-phase drive and out-of-phase drive, for example. That is, the control circuit 10 drives legs LA to LD such that the length of the in-phase drive and the length of the out-of-phase drive to legs LA to LD are the same. As a result, the control circuit 10 can drive legs LA, LB and legs LC, LD with a duty cycle of 0.5.

[0127] In this way, the control circuit 10 performs in-phase drive P1 on one of the circuits 6 and 7 while performing reverse-phase drive P2 on the other, and switches between in-phase drive P1 and reverse-phase drive P2 at a specific period. Note that the control circuit 10 may switch between in-phase drive and reverse-phase drive at any period, such as every half-period, every one period, or every two periods.

[0128] The control circuit 10 can achieve the same effect whether it drives legs LA to LD as described in Figure 10 or as described in Figure 9. In other words, the control circuit 10 can achieve a drive that minimizes the losses of the switching elements and the reactor, regardless of whether it is the drive method described in Figure 9 or Figure 10.

[0129] The losses in a switching element include switching loss and conduction loss, while the losses in a reactor include iron loss and copper loss. Switching loss and iron loss are constant regardless of the current value, while conduction loss and copper loss increase as the current value increases.

[0130] The ratio of losses in the switching elements and reactors changes depending on the load conditions. Since it is well known which loss can be effectively suppressed by in-phase drive and which by reverse-phase drive, the power converter 101 changes whether to perform in-phase drive P1 or reverse-phase drive P2 on legs LA, LB and legs LC, LD, based on which loss can be effectively suppressed, so as to reduce the total of the losses in the switching elements and reactors.

[0131] As a result, the power converter 101 can switch between in-phase drive and out-of-phase drive according to the load conditions and phase conditions, thereby achieving a drive that minimizes losses in the switching element and the reactor.

[0132] Thus, the power converter 101 of the second embodiment can suppress ripple current of the device input current, as well as suppress losses and heat generation, by switching between in-phase drive P1 and out-of-phase drive P2 according to load conditions and phase conditions, with a compact device configuration.

[0133] Embodiment 3. Next, Embodiment 3 will be described using Figures 11 and 12. In Embodiment 3, the power converter 101 changes the switching frequency of each circuit leg in accordance with the phase of the input voltage so that the ripple current of the device input current is suppressed.

[0134] The power converter 101 of Embodiment 3 has the same configuration as the power converter 101 of Embodiment 1. In Embodiment 3, the control method by the control circuit 10 differs from the control method in Embodiment 1.

[0135] Figure 11 is a diagram illustrating the current flowing through the power converter when the power converter according to Embodiment 3 performs the third control. In the graph shown in Figure 11, the horizontal axis represents time and the vertical axis represents current. Note that Figure 11 does not show graphs showing the current input to circuit 6 and the current input to circuit 7. The third control is a control that drives either circuit 6 or 7 at a first switching frequency F1 and the other at a second switching frequency F2. The first switching frequency F1 is a higher frequency than the second switching frequency F2. An example of the first switching frequency F1 is 20 kHz, and an example of the second switching frequency F2 is 10 kHz.

[0136] When the control circuit 10 performs the third control, it changes the switching frequency of circuits 6 and 7. That is, the control circuit 10 drives circuits 6 and 7 by changing the switching frequency according to circuits 6 and 7. For example, when the control circuit 10 drives the legs LA and LB of circuit 6 at the first switching frequency F1, it drives the legs LC and LD of circuit 7 at the second switching frequency F2. On the other hand, when the control circuit 10 drives the legs LA and LB at the second switching frequency F2, it drives the legs LC and LD at the first switching frequency F1. When the control circuit 10 performs the third control, it drives circuits 6 and 7 in-phase or out-of-phase, and does not change between in-phase and out-of-phase driving.

[0137] In the graphs shown in Figure 11, the second graph from the top shows the current values ​​iac3 and iac4 of the first winding current when the control circuit 10 drives the legs LA and LB of the circuit 6 at the first switching frequency F1 during the time T0 to T1.

[0138] In the graphs shown in Figure 11, the third graph from the top shows the current values ​​iac5 and iac6 of the second winding current when the control circuit 10 drives the leg LC and LD of circuit 7 at a second switching frequency F2 during time T0 to T1. An example of the first switching frequency F1 is 20 kHz, and an example of the second switching frequency F2 is 10 kHz. In this way, the control circuit 10 drives circuit 6 and circuit 7 at different switching frequencies.

[0139] In the graphs shown in Figure 11, the first graph from the top, similar to the first graph from the top in Figure 4, shows the current value iac of the device input current input from the AC power source 1 to the power converter 101.

[0140] The control circuit 10 can achieve the same effect whether it drives legs LA to LD as described in Figures 9 and 10, or as described in Figure 11. In other words, the control circuit 10 can achieve the smallest possible loss in the switching element and the reactor regardless of which driving method is used, as described in Figures 9 and 10 or Figure 11.

[0141] Figure 12 is a diagram illustrating the current flowing through the power converter when the power converter according to Embodiment 3 performs the fourth control. In the graph shown in Figure 12, the horizontal axis represents time and the vertical axis represents current. Note that Figure 12 does not show graphs showing the current input to circuit 6 and the current input to circuit 7. The fourth control is a control that drives either circuit 6 or 7 at a first switching frequency F1 and the other at a second switching frequency F2, while switching between driving at the first switching frequency F1 and driving at the second switching frequency F2 at a specific period. When the control circuit 10 performs the fourth control, it drives circuits 6 and 7 in phase or in opposite phase, and does not change between in-phase and opposite-phase driving.

[0142] In Figure 12, the timing when the phase is 0 degrees is shown at time T2, the timing when the phase is 45 degrees is shown at time T3, the timing when the phase is 135 degrees is shown at time T4, and the timing when the phase is 180 degrees (0 degrees) is shown at time T5.

[0143] When the control circuit 10 performs the fourth control, it drives circuits 6 and 7 while switching the switching frequency between the first switching frequency F1 and the second switching frequency F2 according to the phase of the input voltage to the power converter 101. For example, while the control circuit 10 drives the legs LA and LB of circuit 6 at the first switching frequency F1, it drives the legs LC and LD of circuit 7 at the second switching frequency F2. On the other hand, while the control circuit 10 drives the legs LA and LB of circuit 6 at the second switching frequency F2, it drives the legs LC and LD of circuit 7 at the first switching frequency F1.

[0144] When the control circuit 10 changes the drive of legs LA and LB from the first switching frequency F1 to the second switching frequency F2, it also changes the drive of legs LC and LD from the second switching frequency F2 to the first switching frequency F1. On the other hand, when the control circuit 10 changes the drive of legs LA and LB from the second switching frequency F2 to the first switching frequency F1, it also changes the drive of legs LC and LD from the first switching frequency F1 to the second switching frequency F2. Hereinafter, the drive using the first switching frequency F1 may be referred to as the first frequency drive, and the drive using the second switching frequency F2 may be referred to as the second frequency drive.

[0145] In the graphs shown in Figure 12, the second graph from the top shows the current values ​​iac3 and iac4 when the control circuit 10 drives the legs LA and LB of the circuit 6 with a second switching frequency F2 from time T2 to T3, drives them with a first switching frequency F1 from time T3 to T4, and drives them with the second switching frequency F2 from time T4 to T5.

[0146] In the graphs shown in Figure 12, the third graph from the top shows the current values ​​iac5 and iac6 when the control circuit 10 drives the leg LC and LD of circuit 7 at a first switching frequency F1 from time T2 to T3, drives them at a second switching frequency F2 from time T3 to T4, and drives them at the first switching frequency F1 from time T4 to T5.

[0147] In the graphs shown in Figure 12, the first graph from the top, similar to the first graph from the top in Figure 4, shows the current value iac of the current input from the AC power source 1 to the power converter 101.

[0148] The control circuit 10 simultaneously switches between first-frequency drive and second-frequency drive for legs LA and LB. Figure 12 shows the case where the control circuit 10 switches between first-frequency drive and second-frequency drive at timings of 45 degrees and 135 degrees in phase of the input voltage. Note that the control circuit 10 may perform the switching between first-frequency drive and second-frequency drive for legs LA to LD at any timing.

[0149] Furthermore, the control circuit 10 averages the driving periods of the first frequency drive and the second frequency drive, for example. That is, the control circuit 10 drives legs LA to LD such that the length of the first frequency drive and the length of the second frequency drive are the same. As a result, the control circuit 10 can drive legs LA, LB and legs LC, LD with a duty cycle of 0.5.

[0150] Thus, the control circuit 10 drives either circuit 6 or circuit 7 by a first switching frequency F1 and the other by a second switching frequency F2. The control circuit 10 may also switch between the first frequency drive and the second frequency drive at intervals of half a period, one period, or two periods.

[0151] The control circuit 10 can achieve the same effect whether it drives legs LA to LD as described in Figure 11 or as described in Figure 12. In other words, the control circuit 10 can achieve a drive that minimizes the losses of the switching elements and the reactor, regardless of which driving method is used, as described in Figure 11 or Figure 12.

[0152] Since it is well known which loss—the loss of the switching element or the loss of the reactor—can be effectively suppressed for each switching frequency, the power converter 101 changes whether to drive the legs LA, LB and legs LC, LD at the first switching frequency F1 or the second switching frequency F2, based on which loss can be effectively suppressed, so that the sum of the losses of the switching element and the reactor is reduced.

[0153] As a result, the power converter 101 can switch between driving at a first switching frequency F1 and driving at a second switching frequency F2 depending on the load conditions and phase conditions, thereby achieving a drive that minimizes the losses of the switching elements and the reactor.

[0154] Thus, the power converter 101 of the third embodiment can suppress ripple current of the device input current, as well as suppress losses and heat generation, by switching between driving with a first switching frequency F1 and driving with a second switching frequency F2 according to the load conditions and phase conditions, with a compact device configuration.

[0155] Embodiment 4. Next, Embodiment 4 will be described using Figures 13 to 15. In Embodiment 4, the power converter 101 switches the drive state between the leg LA, LB pair and the leg LC, LD pair at specific intervals.

[0156] The power converter 101 of Embodiment 4 has the same configuration as the power converter 101 of Embodiment 1. In Embodiment 4, the control method by the control circuit 10 differs from the control method in Embodiment 1.

[0157] In the power converter 101, if the drive for legs LA and LB as shown in the third graph of Figure 6 and the drive for legs LC and LD as shown in the fourth graph of Figure 6 are continued, the amount of loss in legs LA and LB will differ from the amount of loss in legs LC and LD due to individual differences in the switching elements.

[0158] If the losses in legs LA and LB differ from those in legs LC and LD, the thermal design of the power converter 101 is based on the leg with the largest loss. In this case, the legs with smaller losses than the leg with the largest loss will be over-designed. Therefore, in Embodiment 4, the maximum loss in each set of legs of the power converter 101 is suppressed by averaging the losses in legs LA to LD.

[0159] Specifically, the control circuit 10 switches the drive state of each even-numbered set of legs at each cycle of the device input voltage, which is the input voltage to the power converter 101, in order to average the losses in legs LA to LD. Here, the control circuit 10 switches the drive state of the leg LA, LB set and the leg LC, LD set at each cycle of the device input voltage.

[0160] Figure 13 is a diagram illustrating the losses in each leg set when the power converter according to Embodiment 4 switches the drive state for each leg set. In the graph shown in Figure 13, the horizontal axis is time, and the vertical axis is loss (heat generation).

[0161] Graph 201 shows examples of losses in legs LA and LB and legs LC and LD when the driving conditions shown in the third graph of Figure 6 for legs LA and LB are continued, and the driving conditions shown in the fourth graph of Figure 6 for legs LC and LD are continued. Graph 201 shows a case where the losses in legs LA and LB are greater than the losses in legs LC and LD due to individual differences in the switching elements.

[0162] The power converter 101 of Embodiment 4 switches the drive state between the leg LA, LB pair and the leg LC, LD pair at specific cycles (for example, every cycle). The control circuit 10, for example, sequentially switches between in-phase drive as shown in the second graph of Figure 9 and out-of-phase drive as shown in the third graph for legs LA to LD.

[0163] The control circuit 10 performs in-phase drive on legs LA and LB while performing in-phase drive on legs LC and LD, and performs in-phase drive on legs LC and LD while performing in-phase drive on legs LA and LB.

[0164] For example, in the first period, the control circuit 10 performs in-phase drive on legs LA and LB as shown in the second waveform of Figure 9, and out-of-phase drive on legs LC and LD as shown in the second waveform of Figure 9. Then, in the second period, the control circuit 10 performs out-of-phase drive on legs LA and LB as shown in the third waveform of Figure 9, and in-phase drive on legs LC and LD as shown in the third waveform of Figure 9. Furthermore, in the third period, the control circuit 10 performs in-phase drive on legs LA and LB as shown in the second waveform of Figure 9, and out-of-phase drive on legs LC and LD as shown in the third waveform of Figure 9. In other words, in the Nth (N is a natural number) period, the control circuit 10 performs in-phase drive on legs LA and LB and out-of-phase drive on legs LC and LD, and in the (N+1)th period, it performs out-of-phase drive on legs LA and LB and in-phase drive on legs LC and LD.

[0165] The control circuit 10 switches the drive state for each even-numbered set of legs by repeatedly performing in-phase and out-of-phase driving for legs LA and LB, and repeatedly performing out-of-phase and in-phase driving for legs LC and LD. By changing between in-phase and out-of-phase driving at a low frequency for the leg LA and LB sets and the leg LC and LD sets, the control circuit 10 makes it possible to average out the heat generation, losses, and noise in legs LA to LD.

[0166] Graph 202 shows the loss of leg LA to LD when the losses in leg LA to LD are averaged. As shown in graphs 201 and 202, the maximum loss of leg LA to LD when losses are averaged is smaller than the maximum loss of leg LA to LD when losses are not averaged. This makes it possible to suppress excessive thermal design, and thus to manufacture the power converter 101 at a low cost.

[0167] Furthermore, the control circuit 10 may perform a drive as shown in the second graph of Figures 10 to 12 instead of an in-phase drive as shown in the second graph of Figure 9, and a drive as shown in the third graph of Figures 10 to 12 instead of an out-of-phase drive as shown in the third graph of Figure 9. Hereinafter, the drive as shown in the second graph of Figures 9 to 12 may be referred to as the first drive, and the drive as shown in the third graph may be referred to as the second drive. Also, as mentioned above, the control described in Figure 9 is the first control, the control described in Figure 10 is the second control, the control described in Figure 11 is the third control, and the control described in Figure 12 is the fourth control.

[0168] When the control circuit 10 performs the second and third stages of driving as shown in Figure 10, it performs in-phase driving on legs LA and LB while performing in-phase driving on legs LC and LD, and performs in-phase driving on legs LC and LD while performing in-phase driving on legs LA and LB.

[0169] In this case, the control circuit 10 repeatedly performs a first drive to legs LA and LB, as shown in the second waveform of Figure 10, and a second drive, as shown in the third waveform of Figure 10, and repeats the second drive to legs LC and LD, as shown in the third waveform of Figure 10, and the first drive, as shown in the second waveform of Figure 10.

[0170] Furthermore, when the control circuit 10 performs the second and third stages of driving as shown in Figure 11, while it is performing the first frequency drive on legs LA and LB, it performs the second frequency drive on legs LC and LD, and while it is performing the second frequency drive on legs LA and LB, it performs the first frequency drive on legs LC and LD.

[0171] In this case, the control circuit 10 repeatedly performs a first drive to legs LA and LB, as shown in the second waveform of Figure 11, and a second drive, as shown in the third waveform of Figure 11, and repeats the second drive to legs LC and LD, as shown in the third waveform of Figure 11, and the first drive, as shown in the second waveform of Figure 11.

[0172] Furthermore, when the control circuit 10 performs the second and third stages of driving as shown in Figure 12, while it is performing the first frequency drive on legs LA and LB, it performs the second frequency drive on legs LC and LD, and while it is performing the second frequency drive on legs LA and LB, it performs the first frequency drive on legs LC and LD.

[0173] In this case, the control circuit 10 repeatedly performs a first drive to legs LA and LB, as shown in the second waveform of Figure 12, and a second drive, as shown in the third waveform of Figure 12, and repeats the second drive to legs LC and LD, as shown in the third waveform of Figure 12, and the first drive, as shown in the second waveform of Figure 12.

[0174] Furthermore, the control circuit 10 may combine the first to fourth controls shown in Figures 9 to 12. For example, during the Nth drive period, the control circuit 10 may execute the Mth control (M is a natural number from 1 to 4) from the first to fourth controls for legs LA to LD, and during the (N+1)th drive period, it may execute a control other than the Mth control (hereinafter referred to as the Xth control) from the first to fourth controls for legs LA to LD.

[0175] The control circuit 10 may drive legs LA to LD such that the duration of the first drive and the duration of the second drive in the control of leg LA to LD are the same length. Alternatively, the control circuit 10 may drive legs LA to LD such that the duration of the first drive and the duration of the second drive in the control of leg LA to LD are the same length.

[0176] The control circuit 10 may, for example, perform control of the Mth (where M is a natural number from 1 to 4) during the Nth and (N+1)th drive periods, and perform control of the Xth leg LA to LD during the (N+2)th and (N+3)th drive periods.

[0177] In this case, during the Nth drive period, the control circuit 10 performs the first drive of the Mth control to legs LA and LB, and the second drive of the Mth control to legs LC and LD. Then, during the (N+1)th drive period, the control circuit 10 reverses the first and second drives of the Mth control. That is, during the (N+1)th drive period, the control circuit 10 performs the second drive of the Mth control to legs LA and LB, and the first drive of the Mth control to legs LC and LD.

[0178] Then, during the (N+2)th drive period, the control circuit 10 performs the first drive of the Xth control to legs LA and LB, and the second drive of the Xth control to legs LC and LD. Then, during the (N+3)th drive period, the control circuit 10 reverses the first and second drives of the Xth control. That is, during the (N+3)th drive period, the control circuit 10 performs the second drive of the Xth control to legs LA and LB, and the first drive of the Xth control to legs LC and LD.

[0179] Figure 14 is a diagram illustrating the current flowing through the power converter when the power converter according to Embodiment 4 switches the type of control method for each operating period. In the graph shown in Figure 14, the horizontal axis represents time and the vertical axis represents current. Figure 14 shows the current flowing through the power converter 101 when the control circuit 10 combines the first control in Figure 9 and the second control in Figure 10. In Figure 14, the timings with a phase of 0 degrees are indicated by times T11, T12, and T13.

[0180] In the waveforms shown in Figure 14, the second waveform from the top shows the current values ​​iaac3 and iaac4 of the first winding current when the control circuit 10 drives legs LA and LB with the first drive of the first control in Figure 9 during the first drive period, time T11 to T12, and drives legs LA and LB with the first drive of the second control in Figure 10 during the second drive period, time T12 to T13. That is, the current values ​​iaac3 and iaac4 in the second waveform from the top in Figure 14 between time T11 and T12 correspond to the current values ​​iaac3 and iaac4 in the second waveform from the top in Figure 9. Also, the current values ​​iaac3 and iaac4 in the second waveform from the top in Figure 14 between time T12 and T13 correspond to the current values ​​iaac3 and iaac4 in the second waveform from the top in Figure 10.

[0181] Note that in the second waveform of Figure 10, the waveform for current value iac4 is shown above the waveform for current value iac3, whereas in the second waveform from the top of Figure 14, the waveform for current value iac3 is shown above the waveform for current value iac4.

[0182] In the waveforms shown in Figure 14, the third waveform from the top shows the current values ​​iac5 and iac6 of the second winding current when the control circuit 10 drives the leg LC and LD with the second drive of the first control in Figure 9 between times T11 and T12, and drives the leg LC and LD with the second drive of the second control in Figure 10 between times T12 and T13. That is, the current values ​​iac5 and iac6 between times T11 and T12 in the third waveform from the top in Figure 14 correspond to the current values ​​iac5 and iac6 in the third waveform from the top in Figure 9. Also, the current values ​​iac5 and iac6 between times T12 and T13 in the third waveform from the top in Figure 14 correspond to the current values ​​iac5 and iac6 in the third waveform from the top in Figure 10.

[0183] Note that in the third waveform of Figures 9 and 10, the waveform for current value iac5 is shown above the waveform for current value iac6, whereas in the third waveform from the top of Figure 14, the waveform for current value iac6 is shown above the waveform for current value iac5.

[0184] Of the waveforms shown in Figure 14, the first waveform from the top, like the first waveform from the top shown in Figure 4, represents the current value iac of the current input from the AC power source 1 to the power converter 101. In other words, the first waveform from the top shown in Figure 14 is the waveform of the current value iac, which is a combination of current values ​​iac3 to iac6.

[0185] Since the power converter 101 drives legs LA to LD with the first control described in Figure 9 during the time T11 to T12, the ripple current of the device input current can be suppressed, as well as losses and heat generation, as described in Embodiment 2.

[0186] Furthermore, since the power converter 101 drives legs LA to LD with the second control described in Figure 10 during the time T12 to T13, the ripple current of the device input current can be suppressed, as well as losses and heat generation, as described in Embodiment 2.

[0187] Furthermore, the power converter 101 may drive legs LA to LD using any of the first to fourth controls during the periods T11 to T12 and T12 to T13. During the period when the power converter 101 drives legs LA and LB with the Mth control, it drives legs LC and LD with the Mth control. Also, when the power converter 101 drives legs LA and LB with the first control, it drives legs LC and LD with the second control, and when the power converter 101 drives legs LA and LB with the second control, it drives legs LC and LD with the first control.

[0188] In Figure 14, the control method of legs LA to LD between times T11 and T12 by the control circuit 10 is the first control method, and the control method of legs LA to LD between times T12 and T13 is the second control method.

[0189] Since the power converter 101 changes the type of control method between time T11-T12 and time T12-T13, it can distribute losses and heat generation even more effectively than in the case of using only one type of control method.

[0190] Furthermore, the power converter 101 may apply three or more types of control. That is, the power converter 101 may apply three or more types of control from the first to fourth types of control and drive the legs LA to LD while switching between the three or more types of control. In this case as well, the control circuit 10 may drive the legs LA to LD such that the period of the first drive to the legs LA to LD and the period of the second drive are the same length.

[0191] Incidentally, in the power converter 101, the smaller the load being driven (the smaller the power used for driving), the larger the ratio of switching loss and iron loss, which are fixed loss values, becomes, and the less efficient the driving becomes. Therefore, the control circuit 10 of the power converter 101 may change the number of circuits being driven according to the size of the load. For example, if the load being driven is smaller than a specific value, the control circuit 10 drives only one of circuits 6 and 7 at specific intervals and stops driving the other. That is, the control circuit 10 switches between the circuits that are driven and the circuits that are not driven at specific intervals.

[0192] The power converter 101 calculates the load, for example, assuming that the voltage value Vac is a constant value. In this case, the power converter 101 calculates the load by (voltage value Vac) × (current value iac).

[0193] The load driven by the power converter 101 corresponds to the current value iac. Therefore, the control circuit 10 may determine, based on the current value iac, whether to drive only one of circuits 6 and 7 or both.

[0194] The control circuit 10 calculates the current value iac of the device input current by, for example, summing the current value iac2, which is the circuit input current to circuit 6, and the current value iac1, which is the circuit input current to circuit 7. The control circuit 10 calculates the load based on the current value iac and voltage value Vac of the device input current to the power converter 101, and determines whether to drive only one of circuits 6 and 7 or both based on the magnitude of the load. In this way, the control circuit 10 uses the current value iac2, which is the circuit input current to circuit 6, and the current value iac1, which is the circuit input current to circuit 7, to determine whether to drive only one of circuits 6 and 7 or both.

[0195] The control circuit 10 drives only one of circuits 6 or 7, for example, when the load is smaller than a first reference value. The first reference value is set based on the load size at which the loss when both circuits 6 and 7 are driven is the same as the loss when only one of circuits 6 or 7 is driven. In this way, the control circuit 10 drives only one of circuits 6 or 7 according to the load size driven by the power converter 101.

[0196] As a result, when the load to be driven is smaller than the first reference value, the control circuit 10 can reduce the number of drive circuits, thereby reducing the number of conductive components and lowering losses compared to when the number of drive circuits is not reduced.

[0197] Furthermore, when the load to be driven is smaller than the first reference value, the control circuit 10 may switch between the driven circuit and the non-driven (stopped) circuit among circuits 6 and 7 at a specific period. When the load to be driven is smaller than the first reference value, for example, the control circuit 10 drives circuit 6 and stops circuit 7 in the Nth period, and stops circuit 6 and drives circuit 7 in the (N+1)th period. The control circuit 10 switches between the driven circuit and the stopped circuit so that the driving time of circuits 6 and 7 is the same when the load is smaller than the first reference value.

[0198] When the load being driven is smaller than the first reference value, the control circuit 10 can average out the heat generation, losses, and noise in circuits 6 and 7 by changing the driving and stopping of circuits 6 and 7 at a low frequency.

[0199] Furthermore, when the load being driven is smaller than the first reference value and only one of the circuits 6 and 7 is being driven, the control circuit 10 may determine whether to perform only in-phase drive and / or out-of-phase drive, or both in-phase drive and out-of-phase drive, for the driven circuit among circuits 6 and 7.

[0200] In this case, the control circuit 10 determines, based on the current value iac, whether to perform either in-phase drive or out-of-phase drive, or both, for the driving circuit among circuits 6 and 7.

[0201] For example, when the current value iac is smaller than a first reference value, the control circuit 10 determines, based on the current value iac, whether to perform only one of in-phase drive and / or reverse-phase drive, or both, for either circuit 6 or 7.

[0202] For example, if the load is smaller than a second reference value which is smaller than the first reference value, the control circuit 10 may either drive all of the legs of either circuit 6 or 7 in reverse phase, or drive all of them in the same phase. This allows the control circuit 10 to further reduce losses when the load is smaller than the second reference value.

[0203] Figure 15 is a diagram illustrating the loss when the control method of the power conversion device according to Embodiment 4 is changed according to the load size. Figure 15 shows a graph representing the relationship between the load size and the loss size. In the graph shown in Figure 15, the horizontal axis represents the load size, and the vertical axis represents the loss (heat generation).

[0204] The loss L1 shown in Figure 15 represents the loss in the power converter 101 according to Embodiment 4, and the loss Lx represents the loss in the comparative power converter. The loss Lx in the comparative power converter is proportional to the magnitude of the load.

[0205] The loss L1 in the power converter 101 and the loss Lx in the comparative power converter become smaller as the load decreases. Furthermore, for loads of the same magnitude, the loss L1 is smaller than the loss Lx. For example, in the power converter 101, when the load is greater than or equal to the first reference value V1, both circuits 6 and 7 are driven, so the loss is distributed. Therefore, even when the magnitude of the current value iac is greater than or equal to the first reference value V1, for current values ​​iac of the same magnitude, the loss L1 is smaller than the loss Lx.

[0206] When the magnitude of the current value iac is smaller than the first reference value V1, the power converter 101 reduces the number of circuits it drives. That is, when the magnitude of the current value iac is smaller than the first reference value V1, the power converter 101 drives only one of circuits 6 or 7. As a result, when the magnitude of the current value iac is smaller than the first reference value V1, the power converter 101 can reduce the number of drives compared to when both circuits 6 and 7 are driven, thus reducing losses compared to when the number of drives is not reduced.

[0207] Furthermore, if the load is smaller than the second reference value V2 (< the first reference value V1), the power converter 101 drives all legs in reverse phase for either one of the circuits 6 or 7 being driven. As a result, when the load being driven is smaller than the second reference value V2, the power converter 101 can reduce losses compared to when both reverse-phase and in-phase driving are performed for either one of the circuits 6 or 7 being driven.

[0208] Furthermore, the control circuit 10 may monitor the amount of heat generated in circuits 6 and 7 and, based on the amount of heat generated in circuits 6 and 7, switch between the driven circuit and the non-driven circuit so that the amount of heat generated in circuits 6 and 7 is averaged out. In this case, the control circuit 10 monitors the amount of heat generated in circuits 6 and 7 at specific intervals, drives the circuit with the smaller amount of heat generated, and stops the circuit with the larger amount of heat generated.

[0209] Alternatively, the control circuit 10 may calculate the total loss in circuits 6 and 7 and switch between driving and not driving the circuit that minimizes the total loss. In this case, the control circuit 10 calculates the total loss in circuits 6 and 7 at specific intervals, determines which of circuits 6 and 7 results in a larger total loss when driven, drives the circuit with the smaller total loss, and stops the circuit with the larger total loss.

[0210] The control circuit 10 calculates the total loss in circuits 6 and 7 based on the input power to the power converter 101, for example. The input power to the power converter 101 is calculated by the product of the current value iac sent to the power converter 101 and the voltage value Vac of the AC voltage output by the AC power supply 1. For example, the control circuit 10 drives the circuit with the smaller total loss between the total loss over the most recent L (L is a natural number) cycles when driving circuit 6 and the total loss over the most recent L cycles when driving circuit 7. The control circuit 10 may also switch the driven circuit using MPPT (Maximum Power Point Tracking) control, such as the hill-climbing method.

[0211] Thus, the power converter 101 of Embodiment 4 switches the control method of circuit 6 (the set of legs LA and LB) and circuit 7 (the set of legs LC and LD) at specific intervals, making it possible to average out the heat generation, losses, and noise in the legs LA to LD.

[0212] Embodiment 5. Next, Embodiment 5 will be described using Figures 16 to 19. In Embodiment 5, the power conversion process in Embodiments 1 to 4 is realized by a circuit different from the circuits 6 and 7 provided in the power conversion device. Note that in the power conversion device shown in Figures 16 to 19, the sensors such as sensors 39, 49, 81, and 82 are not shown.

[0213] Figure 16 is a diagram showing a first circuit configuration example of a power conversion device according to Embodiment 5. Among the components in Figure 16, components that achieve the same function as the power conversion device 101 of Embodiment 1 shown in Figure 1 are denoted by the same reference numerals, and redundant explanations are omitted.

[0214] Compared to power converter 101, power converter 102 is equipped with circuits 6P and 7P instead of circuits 6 and 7. Circuit 6P is connected in the same position as circuit 6, and circuit 7P is connected in the same position as circuit 7.

[0215] Compared to circuit 6, circuit 6P has switching elements 65 and 66 instead of rectifier elements 61 and 62. That is, circuit 6P has switching elements 65 and 66 as a rectifier circuit. Thus, circuit 6P has switching elements 65 and 66 and legs LA and LB.

[0216] The switching elements 65 and 66 are the same type of switching elements as those in the legs LA and LB, and are connected to the positions of the rectifier elements 61 and 62. Since the legs LA and LB each have two switching elements, the circuit 6P has a total of six switching elements.

[0217] Similarly, circuit 7P has switching elements 75 and 76 instead of rectifier elements 71 and 72, compared to circuit 7. That is, circuit 7P has switching elements 75 and 76 and leg LC and LD. Switching elements 75 and 76 are the same type of switching elements as those in leg LC and LD, and are connected in the positions of rectifier elements 71 and 72. Since leg LC and LD each have two switching elements, circuit 7P has a total of six switching elements.

[0218] As described above, the rectifier circuit of circuit 6P is composed of switching elements 65 and 66. In this rectifier circuit, switching element 65 and switching element 66 are connected in series, and the connection point between switching element 65 and switching element 66 is connected to the other end of the AC power supply 1.

[0219] Similarly, the rectifier circuit of circuit 7P is composed of switching elements 75 and 76. In this rectifier circuit, switching elements 75 and 76 are connected in series, and the connection point between switching elements 75 and 76 is connected to the other end of the AC power supply 1.

[0220] In circuits 6P and 7P, the cathodes of the parasitic diodes of each switching element are connected to the positive terminal of the smoothing capacitor 8, and the anodes are connected to the negative terminal of the smoothing capacitor 8, so that circuits 6P and 7P are connected to the smoothing capacitor 8.

[0221] In circuit 6P, the switching elements 65 and 66 perform the same operations as the rectifier elements 61 and 62, so circuit 6P can perform the same operations as circuit 6. In circuit 7P, the switching elements 75 and 76 perform the same operations as the rectifier elements 71 and 72, so circuit 7P can perform the same operations as circuit 7. As a result, the power converter 102 can perform the same operations as the power converter 101 described in embodiments 1 to 4.

[0222] Figure 17 shows a second example of the circuit configuration of the power conversion device according to Embodiment 5. Among the components in Figure 17, components that achieve the same function as the power conversion device 102 in Figure 16 are denoted by the same reference numerals, and redundant explanations are omitted.

[0223] The power converter 103 has three sets of combinations of magnetic coupling reactors and circuits. Compared to the power converter 102, the power converter 103 has a magnetic coupling reactor 5 in addition to magnetic coupling reactors 3 and 4. Also, compared to the power converter 102, the power converter 103 has a circuit 8P in addition to circuits 6P and 7P. Magnetic coupling reactor 5 is connected to circuit 8P. Circuit 8P is a circuit similar to circuit 6P and has six switching elements.

[0224] Circuits 6P to 8P are connected in parallel. Circuit 8P has legs LE and LF, which are the same as legs LA and LB, and a rectifier circuit. The rectifier circuit of circuit 8P is composed of switching elements 85 and 86, which are the same as switching elements 65 and 66. In the rectifier circuit of circuit 8P, switching elements 85 and 86 are connected in series, and the connection point between switching elements 85 and 86 is connected to the other end of the AC power supply 1. The cathode of switching element 85 is connected to the positive terminal of the smoothing capacitor 8, and the anode of switching element 86 is connected to the negative terminal of the smoothing capacitor 8.

[0225] The power converter 103 has a sensor (referred to here as sensor 59) similar to sensors 39 and 49, but sensor 59 is not shown in Figure 17. In the magnetic coupling reactor 5, the current value iac flowing through the magnetic coupling reactor 5 is detected by sensor 59, and the detected current value iac is transmitted to the control circuit 10. Note that the connection lines between sensor 59 and the control circuit 10 are not shown in Figure 17.

[0226] Thus, while the power converter 102 had two combinations of magnetic coupling reactors and circuits, the power converter 103 has three combinations of magnetic coupling reactors and circuits.

[0227] The control circuit 10 of the power converter 103 performs the drive described in Embodiments 1 to 4 on two of the circuits 6P to 8P, and keeps the remaining circuit stopped. The control circuit 10 controls the two circuits to be driven to run in sequence so that the driving times of circuits 6P to 8P are approximately the same.

[0228] As a result, the power converter 103 can perform the same operation as the power converter 101 described in Embodiments 1 to 4. Furthermore, since the control circuit 10 of the power converter 103 has three sets of combinations of magnetic coupling reactors and circuits, the current flowing per switching element in circuits 6P to 8P can be reduced compared to the case with two sets. As a result, losses and heat generation are distributed more evenly in the power converter 103 than in the power converter 102.

[0229] The power converter 103 may have three circuits similar to circuit 6 instead of circuits 6P to 8P. In other words, the circuit provided by the power converter 103 may be a circuit having two legs and two rectifier elements.

[0230] Furthermore, the power converter 103 may have four or more combinations of magnetic coupling reactors and circuits. Even when the power converter 103 has four or more combinations of magnetic coupling reactors and circuits, each circuit is connected in parallel with the inverter 51. In this case, the control circuit 10 controls the two circuits to be driven to switch sequentially at a specific period so that the driving time of each circuit is the same.

[0231] Figure 18 shows a third example of the circuit configuration of the power converter according to Embodiment 5. Among the components in Figure 18, components that achieve the same function as the power converter 102 in Figure 16 are denoted by the same reference numerals, and redundant explanations are omitted.

[0232] Compared to power converter 102, power converter 104 includes circuits 6Q and 7Q instead of circuits 6P and 7P. In addition to the components of power converter 102, power converter 104 also includes rectifier diodes 2. Circuit 6Q is connected in the same position as circuit 6P, and circuit 7Q is connected in the same position as circuit 7P.

[0233] Circuit 6Q does not have switching elements 65 and 66, unlike circuit 6P. That is, circuit 6Q has legs LA and LB. Since legs LA and LB each have two switching elements, circuit 6Q has a total of four switching elements.

[0234] Similarly, circuit 7Q does not have switching elements 75 and 76 compared to circuit 7P. That is, circuit 7Q has leg LC and LD. Since leg LC and LD each have two switching elements, circuit 7Q has a total of four switching elements.

[0235] The AC power supply 1 is connected to the rectifier diode 2. The rectifier diode 2 is connected to the magnetic coupling reactors 3 and 4 and circuits 6Q and 7Q. Thus, in the power converter 104, the rectifier diode 2 is connected between the AC power supply 1 and the magnetic coupling reactors 3 and 4 and circuits 6Q and 7Q.

[0236] Since the power converter 104 is equipped with a rectifier diode 2, it can perform the same driving as circuits 6P and 7P, which have switching elements 65, 66, 75, and 76 that are rectifier circuits, even if circuits 6Q and 7Q do not have a rectifier circuit. As a result, the power converter 104 can perform the same operation as the power converter 101 described in Embodiments 1 to 4.

[0237] The power converter 104 may have three sets of magnetic coupling reactors and circuits, similar to the power converter 103. In this case as well, the power converter 104 performs the same driving operation as the power converter 103.

[0238] Furthermore, the power converter 104 may have four or more combinations of magnetic coupling reactors and circuits. In this case as well, the control circuit 10 controls the operation so that the driving time of each circuit is approximately the same by sequentially switching between the two circuits to be driven.

[0239] Figure 19 shows a fourth example of the circuit configuration of the power converter according to Embodiment 5. Among the components in Figure 19, components that achieve the same function as the power converter 104 in Figure 18 are denoted by the same reference numerals, and redundant explanations are omitted.

[0240] Compared to power converter 104, power converter 105 is equipped with circuits 6R and 7R instead of circuits 6Q and 7Q. Circuit 6R is connected in the same position as circuit 6Q, and circuit 7R is connected in the same position as circuit 7Q.

[0241] Circuit 6R, compared to circuit 6Q, features leg LAar and LBr instead of leg LA and LB. Circuit 7R, compared to circuit 7Q, features leg LCr and LDr instead of leg LC and LD.

[0242] LegLar to LDr have a similar configuration. That is, LegLar to LDr consists of one switching element and one rectifier diode connected in series. In LegLar to LDr, the rectifier diode is connected to the positive terminal of the smoothing capacitor 8, and the switching element is connected to the negative terminal of the smoothing capacitor 8.

[0243] The AC terminal at the connection point between the switching element and the rectifier diode of the RegLar is connected to the magnetic coupling reactor 3. The AC terminal at the connection point between the switching element and the rectifier diode of the RegLBr is connected to the magnetic coupling reactor 3.

[0244] The AC terminal at the connection point between the switching element and the rectifier diode of the LegLCr is connected to the magnetic coupling reactor 4. The AC terminal at the connection point between the switching element and the rectifier diode of the LegLDr is connected to the magnetic coupling reactor 4.

[0245] In the power converter 105, a rectifier diode 2 is connected before circuits 6R and 7R, so the upper side of the legs LAr to LDr of circuits 6R and 7R does not switch. For this reason, in the power converter 105, the upper side of the legs LAr to LDr of circuits 6R and 7R (the positive side of the smoothing capacitor 8) is used as a rectifier diode.

[0246] Thus, the power converter 105 is equipped with legs LAr to LDr that can perform the same operation as legs LAr to LD, instead of legs LAr to LD. As a result, the power converter 105 can perform the same operation as the power converter 101 described in Embodiments 1 to 4.

[0247] The power converter 105 may have three sets of magnetic coupling reactors and circuits, similar to the power converter 103. In this case as well, the power converter 105 performs the same driving operation as the power converter 103.

[0248] As described above, according to Embodiment 5, the power converters 102 to 105 are configured to perform the same operations as the power converter 101, and therefore can perform the same operations as the power converter 101. Consequently, the power converters 102 to 105 can suppress the ripple current of the device input current with a miniaturized device configuration. Furthermore, since the two circuits of the power converters 102 to 105 are connected in parallel, the losses and heat generated by the power converters 102 to 105 can be distributed.

[0249] Next, the hardware configuration of the control circuit 10 will be described. The control circuit 10 is implemented by a processing circuit. The processing circuit may be a processor and memory that execute a program stored in memory, or it may be dedicated hardware.

[0250] Figure 20 shows an example of the configuration of a processing circuit when the processing circuit included in the control circuit of the power conversion device according to Embodiments 1 to 5 is implemented using a processor and memory. Since the control circuits 10 included in power conversion devices 102 to 105 have a similar hardware configuration, the hardware configuration of the control circuit 10 included in power conversion device 101 will be described here.

[0251] The processing circuit 90 shown in Figure 20 comprises a processor 91 and a memory 92. When the processing circuit 90 consists of a processor 91 and a memory 92, each function of the processing circuit 90 is realized by software, firmware, or a combination of software and firmware. The software or firmware is written as a control program and stored in the memory 92. In the processing circuit 90, each function is realized by the processor 91 reading and executing the control program stored in the memory 92. In other words, the processing circuit 90 includes a memory 92 for storing a control program that will ultimately be executed by the processing of the control circuit 10. This control program can also be said to be a program that causes the control circuit 10 to execute each function realized by the processing circuit 90. This control program may be provided on a computer-readable recording medium on which the control program is recorded, or it may be provided by other means such as a communication medium.

[0252] In the case of the control circuit 10 of Embodiment 1, the control program can also be described as a program that causes the control circuit 10 to execute the processes of steps S10 and S20 in Figure 8.

[0253] Here, the processor 91 is, for example, a CPU (Central Processing Unit), processing unit, arithmetic unit, microprocessor, microcomputer, or DSP (Digital Signal Processor). The memory 92 is, for example, a non-volatile or volatile semiconductor memory such as RAM (Random Access Memory), ROM (Read Only Memory), flash memory, EPROM (Erasable Programmable ROM), EEPROM (Registered Trademark) (Electrically EPROM), magnetic disk, flexible disk, optical disk, compact disk, minidisc, or DVD (Digital Versatile Disc).

[0254] Figure 21 is a diagram showing an example of the configuration of a processing circuit when the processing circuit included in the control circuit of the power conversion device according to Embodiments 1 to 5 is configured with dedicated hardware. Note that the control circuits 10 included in power conversion devices 102 to 105 have a similar hardware configuration, so here we will describe the hardware configuration of the control circuit 10 included in power conversion device 101.

[0255] The processing circuit 93 shown in Figure 21 may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. The processing circuit 93 may be partially implemented with dedicated hardware and partially with software or firmware. In this way, the processing circuit 93 can realize the above-mentioned functions through dedicated hardware, software, firmware, or a combination thereof.

[0256] The configurations shown in the above embodiments are merely examples, and it is possible to combine them with other known technologies, combine different embodiments, and omit or modify parts of the configuration without departing from the gist of the invention.

[0257] 1 AC power supply, 2 rectifier diodes, 3-5 magnetic coupling reactors, 3a-3c, 4a-4c windings, 6, 7, 6P-8P, 6Q, 7Q, 6R, 7R circuits, 8 smoothing capacitors, 10 control circuits, 11 control operation judging unit, 12 output voltage controller, 13 carrier generators, 14A-14D gate signal generators, 31A-31D, 41A-41D terminals, 35d-35f cores, 36 DC magnetic flux, 37 AC magnetic flux, 38d, 38e side legs, 38f center leg, 39, 49, 59, 81, 82 sensors, 51 inverters, 52 motor loads, 61, 62, 71, 72 rectifier elements, 65, 66, 75, 76, 85, 86 switching elements, 90, 93 processing circuits, 91 Processor, 92 memory, 101-105 power converter, 201, 202 graph, F1 first switching frequency, F2 second switching frequency, L1, Lx loss, LA-LF, LAr-LDr leg, P1 common-mode drive, P2 reverse-mode drive, T0-T5, T11-T13 time, V1 first reference value, V2 second reference value, Vac, Vdc voltage value, W1-W3 waveform, iac, iac1-iac6, iacX, iac1X-iac6X current value.

Claims

1. A power conversion device comprising: a plurality of converter circuits having a plurality of switching legs and connected in parallel; a magnetic coupling reactor connected to each of the converter circuits; and a control circuit for controlling the switching elements included in the switching legs, wherein the control circuit drives the plurality of converter circuits while changing the amplitude of the ripple current generated in each of the windings included in the magnetic coupling reactor for each of the plurality of converter circuits based on the phase change of the input voltage input from the AC power supply.

2. The power conversion device according to claim 1, wherein the plurality of converter circuits include a first converter circuit and a second converter circuit, the first converter circuit includes a first leg set which is a set of an even number of switching legs as a plurality of switching legs, the second converter circuit includes a second leg set which is a set of an even number of switching legs as a plurality of switching legs, and the control circuit changes the amplitude of the ripple current by driving the second leg set in a second driving state when the first leg set is driven in a first driving state, and driving the second leg set in a first driving state when the first leg set is driven in a second driving state.

3. The power conversion device according to claim 2, characterized in that the first drive state is in-phase drive, the second drive state is out-of-phase drive, the control circuit drives the second leg set out-of-phase when the first leg set is driven in-phase, drives the second leg set in-phase when the first leg set is driven out-of-phase, and drives the first leg set and the second leg set while switching between in-phase drive and out-of-phase drive for the first leg set and the second leg set.

4. The power conversion device according to claim 2, characterized in that the first driving state is driving at a first switching frequency, the second driving state is driving at a second switching frequency, the control circuit drives the second leg set at a second switching frequency when the first leg set is driven at a first switching frequency, drives the second leg set at a first switching frequency when the first leg set is driven at a second switching frequency, and drives the first leg set and the second leg set while switching between the first switching frequency and the second switching frequency for the first leg set and the second leg set.

5. The power conversion device according to any one of claims 1 to 4, characterized in that the control circuit controls a plurality of converter circuits by a first control method during a first driving period, and controls a plurality of converter circuits by a second control method during a second driving period.

6. The power conversion device according to any one of claims 2 to 5, characterized in that the control circuit changes the number of converter circuits to be driven from among the plurality of converter circuits according to the magnitude of the load to be driven.

7. The power conversion device according to claim 6, characterized in that the control circuit switches between a converter circuit to be driven and a converter circuit that is not driven from among the plurality of converter circuits at specific intervals.

8. The power conversion device according to claim 7, characterized in that the control circuit switches between a converter circuit to be driven and a converter circuit not to be driven among the plurality of converter circuits based on the amount of heat generated in the plurality of converter circuits, so as to average the amount of heat generated in the plurality of converter circuits.

9. The power conversion device according to claim 7, characterized in that the control circuit calculates the total loss in a plurality of converter circuits and switches between a converter circuit to be driven and a converter circuit not to be driven so as to minimize the total loss.

10. The power conversion device according to claim 6, characterized in that the control circuit reduces the number of converter circuits to be driven when the magnitude of the load is less than a first reference value, and drives the converter circuits to be driven by either in-phase drive or reverse-phase drive when the magnitude of the load is less than a second reference value which is less than the first reference value.

11. The power conversion device according to any one of claims 1 to 10, characterized in that the converter circuit has one rectifier leg and two switching legs.

12. The power conversion device according to claim 11, characterized in that the rectifier leg comprises two rectifier elements connected in series.

13. The power conversion device according to claim 11, characterized in that the rectifier leg comprises two switching elements connected in series.

14. The power conversion device according to any one of claims 11 to 13, characterized in that the switching leg comprises two switching elements connected in series.

15. The power conversion device according to any one of claims 11 to 13, characterized in that the switching leg comprises one switching element and one rectifier diode connected in series.

16. The power conversion device according to any one of claims 1 to 10, further comprising the plurality of converter circuits, the magnetic coupling reactor, and the rectifier diode connected to the AC power supply, wherein the converter circuit has two switching legs.

17. A control device for controlling a power conversion device comprising a plurality of converter circuits having a plurality of switching legs and connected in parallel, and a magnetic coupling reactor connected to each of the converter circuits, characterized in that the control device controls the switching elements included in the switching legs and drives the plurality of converter circuits while changing the amplitude of the ripple current generated in each of the windings included in the magnetic coupling reactor for each of the plurality of converter circuits based on the phase change of the input voltage input from the AC power supply.

18. A control method for a power conversion device comprising a plurality of converter circuits having a plurality of switching legs and connected in parallel, and a magnetic coupling reactor connected to each of the converter circuits, characterized in that the control circuit for controlling the switching elements included in the switching legs includes a drive step of driving the plurality of converter circuits while changing the amplitude of the ripple current generated in each of the windings included in the magnetic coupling reactor for each of the plurality of converter circuits based on the phase change of the input voltage input from the AC power supply.

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