Power converter and power conversion method

Abstract

In the ARCP method, this invention provides a power converter that can perform soft switching control with higher precision and reduce switching losses. [Solution] The control unit 15 controls Leg 1 to perform soft switching and causes the resonant operation that occurs when the main switches S1 and S2 are turned on to be executed multiple times. Based on the power supply voltage VH and the load current IL, the time from when the auxiliary switches A1 and A2 are turned on until the terminal voltage Vds of the corresponding switches S1 and S2 start to rise from zero V is measured as the boost time T2, the time from when the terminal voltage Vds of one of the switches S1 and S2 starts to rise from zero V until the terminal voltage Vds of the other switch drops to zero V is measured as the first resonant time T3(1), and the time from when the terminal voltage Vds of the other switch S1 and S2 starts to rise from zero V until the terminal voltage Vds of the one switch drops to zero V is measured as the second resonant time T3(2). Based on these times, the control unit 15 corrects the timing of switching switches S1 and S2.

Description

Technical Field

[0001] The present invention relates to a power converter that performs switching control in an ARCP (Auxiliary Resonant Commutated Pole) method and a power conversion method.

Background Art

[0002] In recent years, in order to miniaturize power converters and reduce the losses of electric motors, efforts have been made to increase the frequency of switching control of power converters. When the switching control frequency is increased, the switching loss increases. Therefore, as a countermeasure, it is necessary to apply soft switching technology to reduce the loss.

[0003] In the ARCP method, which is one of the soft switching technologies, a partial resonance operation by a resonance inductor Lr and a resonance capacitor Cr is utilized. However, due to variations in products, changes in operating conditions, changes in temperature characteristics, aging changes, etc. in these circuit elements, there are variations in the resonance time. Therefore, it is important to accurately adjust the relative switching timing between the on-timing of the auxiliary switch that constitutes the auxiliary resonance circuit and the on-timing of the main switch that is the target of soft switching.

[0004] For example, in Patent Documents 1 and 2, in a DC / DC converter circuit provided with an ARCP circuit, a control unit 11A that controls main switches S1, S2 and resonance switches S3, S4, and a storage unit 12A that stores a first calculation formula regarding the operation timing for turning on the main switches S1, S2 are provided. The control unit 11A calculates a first time from when the resonance switches S3, S4 are turned on until the main switches S1, S2 are turned on based on the first calculation formula, and performs switching processing to turn on the main switches S1, S2 at the end of the first time, and corrects and updates the first calculation formula so that the deviation amount between the crossing timing when the falling resonance current IL2 and the reactor current IL1 cross and the operation timing decreases.

Prior Art Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2023-96959 [Patent Document 2] Japanese Patent Publication No. 2023-37774 [Overview of the project] [Problems that the invention aims to solve]

[0006] Patent documents 1 and 2 disclose a technique for determining the correctness of the switching timing after the power output operation of a power converter and correcting it if it is incorrect. The key point is how to determine the correctness of the switching timing. If the accuracy of such correction is poor, the effect of reducing switching losses will be limited. Furthermore, although switching losses can be reduced once the correction is complete and the optimal switching timing is achieved, losses occur while the correction is being performed in stages.

[0007] The present invention has been made in view of the above circumstances, and its purpose is to provide a power converter and a power conversion method that can perform soft switching control with higher precision and reduce switching losses in the ARCP system. [Means for solving the problem]

[0008] According to the power converter described in claim 1, the power conversion unit (11) comprises one or more legs (1) having a series circuit of a high-potential side main switch (S1) and a low-potential side main switch (S2), a resonant capacitor (Cr) connected in parallel to each main switch, and a series circuit of two auxiliary switches (A1, A2) and a resonant inductor (Lr), one end of which is connected to the common connection point of the two main switches and the other end of which is connected to a common connection to form a bidirectional switch. The power supply voltage detection unit (8) detects the DC power supply voltage supplied to the power conversion unit, and the current detection unit (6) detects the load current supplied from the power conversion unit to the load (5). The terminal voltage detection unit (7) detects the voltage between the conductive terminals of the main switches.

[0009] The control unit (15) controls the legs to perform soft switching and also causes the resonant operation that occurs when the main switch is turned on to be executed multiple times. Based on the power supply voltage and load current, the time from when the auxiliary switch is turned on until the terminal voltage of the corresponding main switch starts to rise from zero V is measured as the boost time, the time from when the terminal voltage of one of the two main switches starts to rise from zero V until the terminal voltage of the other switch drops to zero V is measured as the first resonant time, and the time from when the terminal voltage of the other switch starts to rise from zero V until the terminal voltage of the one switch drops to zero V is measured as the second resonant time.

[0010] The boost time and the first and second resonance times measured by the control unit are stored in the memory unit, and the control unit corrects the timing of switching the main switches based on these times. In this way, by measuring the boost time and the first and second resonance times for the actual resonance operation in each leg, the accuracy of the timing of turning on each main switch can be improved when performing soft switching control.

[0011] According to the power converter described in claim 2, the control unit uses the average value of the resonance times measured for multiple resonance operations as a correction, so that even if there are variations in the multiple resonance times, the timing of switching the main switch can be appropriately corrected.

[0012] According to the power converter described in claim 3, the control unit switches the resonant operation to be performed once or multiple times depending on the conditions. When the resonant operation is set to once, the control unit measures the time from when the voltage between the terminals of one of the two main switches starts to rise from zero V until the voltage between the terminals of the other switch drops to zero V as the resonant time, and stores this time in the memory unit. The control unit then corrects the timing of switching the main switches based on the boost time and the resonant time. As a result, even when the resonant operation is set to once, the timing of switching the main switches can be corrected based on the resonant time stored in the memory unit. [Brief explanation of the drawing]

[0013] [Figure 1] This is a first embodiment, and the diagram shows the configuration of the drive system of the power converter. [Figure 2] Functional block diagram showing the configuration of the power converter's control system. [Figure 3] Diagram showing the detailed configuration of the time measurement unit. [Figure 4] Flowchart showing the processing performed by the control unit. [Figure 5] Timing chart corresponding to the above process [Figure 6] This is a second embodiment, and is a flowchart showing the processing content by the control unit. [Figure 7] This is a third embodiment, a flowchart showing the processing content by the control unit. [Modes for carrying out the invention]

[0014] (First Embodiment) As shown in Figure 1, the power converter 11 of this embodiment includes a leg 1 which is an ARCP-type power circuit section. The series circuits of the high-potential side main switch S1 and the low-potential side main switch S2 that constitute leg 1 are connected in parallel to the DC power supply 4 together with the series circuits of smoothing capacitors 2, 3a and 3b. Leg 1 includes a series circuit of auxiliary switches A1 and A2 and a resonant inductor Lr, which are connected between the midpoint of capacitors 3a and 3b, i.e., the neutral point, and the common connection point of main switches S1 and S2.

[0015] In this embodiment, the main switches S1 and S2 and the auxiliary switches A1 and A2 are all, for example, N-channel MOSFETs. The series circuit of auxiliary switches A1 and A2 is a bidirectional switch, connected such that, for example, their sources or drains are common. Resonant capacitors Cr, which are parasitic capacitances or added capacitances, are connected in parallel to the main switches S1 and S2, respectively.

[0016] A load 5, such as a motor, is connected between the common connection point of the main switches S1 and S2, which are the output terminals of Leg 1, and the negative terminal of the DC power supply 4. A current sensor 6 is positioned between the output terminal of Leg 1 and the load 5. The current sensor 6, which is a current detection unit, detects the load current IL flowing through the load 5. Voltage sensors 7(1) and 7(2), which are terminal voltage detection units, are connected between the drain and source of the main switches S1 and S2, respectively. Voltage sensors 7(1) and 7(2) detect the drain-source voltage Vds of the main switches S1 and S2, respectively. In addition, a voltage sensor 8 is connected to both ends of the DC power supply 4. The voltage sensor 8, which is a power supply voltage detection unit, detects the voltage VH of the DC power supply 4.

[0017] The power converter 11 includes a control device 12 shown in FIG. 2. The control device 12 is composed of, for example, a microcomputer or the like, and includes a storage unit 13, a correction unit 14, a control unit 15, and a time measurement unit 16. The time measurement unit 16 measures the time corresponding to the power supply voltage VH and the load current IL at the switching operation timing of leg 1 that changes during the operation as an inverter or a converter, and outputs the measurement result to the control unit 15. The aforementioned voltage sensors 7(1) and 7(2) are components of the time measurement unit 16. The correction unit 14 corrects the timing at which the control unit 15 controls the switching of leg 1 based on the measurement result of the time measurement unit 16. The above measurement results and the like are stored in the storage unit 13.

[0018] In the following description of the time measurement unit 16 shown in FIG. 3 below, since the configurations of the main switches S1 and S2 are symmetric, the description will be given without attaching (1) and (2) to each reference numeral. The low-potential side terminal of the drive IC 17 is connected to the source of the main switch S, and the high-potential side terminal thereof is connected to the drain of the main switch S via a resistance element 18 and a diode 19. The drive IC 17 drives the gate of the main switch S via a gate resistance 20. A series circuit of resistance elements 21a and 21b is connected between the anode of the diode 19 and the low-potential side terminal of the drive IC 17.

[0019] The common connection point of the resistance elements 21a and 21b is connected to the non-inverting input terminal of the comparator 22. A threshold voltage source 23 is connected between the inverting input terminal of the comparator 22 and the low-potential side terminal of the drive IC 17. The output terminal of the comparator 22 is connected to the input terminal of the control unit 15 via an isolation communication element 24. That is, the comparator 22 compares the drain-source voltage Vds of the main switch S divided by the resistance elements 21a and 21b with the threshold voltage Vref, and outputs the comparison result to the control unit 15.

[0020] The threshold voltage Vref is set near 0V. When the output signal of the comparator 22 changes from the low level to the high level, the control unit 15 determines that the drain-source voltage Vds has started to rise above 0V. Also, when the output signal of the comparator 22 changes from the high level to the low level, the control unit 15 determines that the drain-source voltage Vds has become 0V.

[0021] Based on the signal input from the time measurement unit 16, the control unit 15 measures the boost time T2 and the resonance time T3 as follows. Here, the case of turning on the auxiliary switch A1 and the main switch S1 side will be described. <Boost time T2> · The time from when the control unit 15 turns on the auxiliary switch A1 until the drain-source voltage Vds of the main switch S2 starts to rise from 0V by the voltage sensor 7(2).

[0022] <Resonance time T3> · The time from when the drain-source voltage Vds of the main switch S2 starts to rise from 0V by the voltage sensor 7(2) until the drain-source voltage Vds of the main switch S1 detected by the voltage sensor 7(1) drops to 0V. This corresponds to the case where the number of resonance times is 1 or more (Fig. 4, S6, S11), and is defined as the time T3(1).

[0023] · The time from when the drain-source voltage Vds of the main switch S1 starts to rise from 0V by the voltage sensor 7(1) until the drain-source voltage Vds of the main switch S2 detected by the voltage sensor 7(2) drops to 0V. This corresponds to the case where the number of resonance times is 3 or more (Fig. 4, S12), and is defined as the time T3(2).

[0024] Next, the operation of this embodiment will be described. This description will also mainly focus on the case where the auxiliary switch A1 and the main switch S1 are turned on. As shown in Figure 4, the control unit 15 detects the voltage VH of the DC power supply 4 and the load current IL, which are the operating conditions for Leg 1, using the voltage sensor 8 and the current sensor 6, respectively (S1). Then, in step S9, which will be described later, the control unit reads out the times T1, T2, and T3 corresponding to the power supply voltage VH and load current IL that were previously written to the memory unit 13 (S2). Next, when the auxiliary switch A1 is turned on (S3), the boost time T2 is measured (S4).

[0025] Here, it is determined whether or not the number of resonances generated by driving leg 1 should be 1 (S5). If the number of resonances is 1 (YES), the resonance time T3(1) is measured (S6) and the process proceeds to step S7. If the number of resonances is an odd number of 3 or more (NO), the resonance times T3(1) and T3(2) are measured (S11, S12).

[0026] The following describes the conditions for determining the number of resonances in step S5. For example, when the output is high, such that the load current IL is above a predetermined threshold, the boost time T2 becomes longer. Therefore, even if the number of resonances is only one, there is enough time to perform the correction calculation in the microcomputer constituting the control unit 15 within the time until the main switch S1 is turned on. Thus, the number of resonances is set to one when the system conditions result in high output, and to multiple times when the output is low, such as when the load current IL is below the threshold.

[0027] Furthermore, if the inductance value of the resonant inductor Lr is small, the boost time T2 and resonance time T3 will be shortened. Also, if the capacitance value of the resonant capacitor Cr is small, the resonance time T3 will be shortened, so if there is insufficient time to perform the correction calculation, the number of resonance cycles should be set to multiple cycles. Note that "when the inductance value is small" and "when the capacitance value is small" include cases where the inductance value and capacitance value are small for a single element, cases where an element with a small inductance value is selected and switched from among multiple elements, and cases where an element with a small capacitance value is selected and switched from among multiple elements.

[0028] The resonance times T3(1) and T3(2) are measured by repeating the loop of steps S11 and S12 (N-1) / 2 times if the number of resonances is N. For example, if the number of resonances is 5, resonance times T3(1) to T3(4) will be measured. If N=3, the first resonance time T3(1) and the second resonance time T3(2) will be measured, and if N=5, the first resonance time T3(3) and the second resonance time T3(4) will be added to these. Then, based on the measured times T2 and T3, the SW timing T1 is calculated by correction calculation as (T1=T2+T3×N) (S13). When N=3, the resonance time T3 used in the calculation can be either T3(1) or T3(2), or the more recent time T3(2) can be selected. After that, the same processing as in step S10 is performed (S14) and the process moves to step S8.

[0029] The resonance time measured in step S14 is T3(3) as shown in Figure 5 if N=3, and T3(5), or T3(N), if N=5. The resonance time T3(N) measured at this point cannot be used to calculate the SW timing T1 in step S13 due to processing time constraints. However, in order to improve the accuracy of the correction calculations performed later, it is measured at this timing so that it can be written to the storage unit 13 in step S10, which will be described later.

[0030] In step S7, which is executed when N=1, the SW timing T1 is calculated (T1=T2+T3) based on the boost time T2 measured in step S4 and the resonance time T3 read in step S2, and then the process proceeds to step S8. In step S8, when the main switch S1 is turned on at SW timing T1, the auxiliary switch A1 is turned off after a time T2 measured from that point (S9). Then, T1~T3, which have been corrected and calculated in accordance with the power supply voltage VH and load current IL detected in step S1, are written to the memory unit 13 (S10). However, if N=1, the resonance time T3 measured in step S6 is written to the memory unit 13. After that, the main switch S1 is turned off (S15), but here the resonant capacitor Cr becomes a snubber capacitor, resulting in soft switching operation, and the process returns to step S1.

[0031] Figures 4 and 5 illustrate the operation of turning on the high-potential main switch S1 and auxiliary switch A1 as an example, but this operation corresponds to the case where source current flows from leg 1 to load 5. The timing for turning on the low-potential main switch S2 and auxiliary switch A2 is when sink current flows from load 5 to leg 1, and is controlled similarly during the period when the high-potential main switch S1 is off. However, in the flow of the main switch S2 on operation and main switch S2 off operation, auxiliary switch A1 in steps S3 and S9 becomes A2, main switch S1 in steps S6, S8, S9, S11 and S14 becomes S2, and main switch S2 in steps S4 and S12 becomes S1.

[0032] As described above, according to this embodiment, the power conversion unit 11 includes a leg 1 having a series circuit of main switches S1 and S2, a resonant capacitor Cr connected in parallel to main switches S1 and S2, and a series circuit of auxiliary switches A1 and A2 and a resonant inductor Lr, one end of which is connected to the common connection point of main switches S1 and S2 and the other end of which is connected to a common connection point. The voltage sensor 8 detects the DC power supply voltage VH supplied to the power conversion unit 11, and the current sensor 6 detects the load current IL supplied from the power conversion unit 11 to the load 5. The voltage sensors 7(1) and 7(2) detect the drain-source voltage Vds of the main switches S1 and S2.

[0033] The control unit 15 controls leg 1 to perform soft switching and also causes the resonant operation that occurs when the main switches S1 and S2 are turned on to be executed multiple times. Based on the power supply voltage VH and the load current IL, the control unit 15 measures the time from when the auxiliary switches A1 and A2 are turned on until the terminal voltages Vds of the corresponding main switches S1 and S2 start to rise from zero V as the boost time T2, the time from when the terminal voltage Vds of one of the main switches S1 and S2 starts to rise from zero V until the terminal voltage Vds of the other terminal drops to zero V as the first resonant time T3(1), and the time from when the terminal voltage Vds of the other terminal starts to rise from zero V until the terminal voltage Vds of the one terminal drops to zero V as the second resonant time T3(2).

[0034] The boost time T2 and the first and second resonance times T3(1) and T3(2) measured by the control unit 15 are stored in the memory unit 13, and the control unit 15 corrects the timing of switching the main switches S1 and S2 based on these times. In this way, by measuring the times T2 and T3 for the actual resonance operation in Leg 1, the accuracy of the timing of turning on the main switches S1 and S2 when performing soft switching control can be improved, thereby reducing switching losses.

[0035] (Second Embodiment) In the following description, parts identical to those in the first embodiment are denoted by the same reference numerals and their descriptions are omitted, while the differences are described. The configuration of the power converter in the second embodiment is the same as in the first embodiment, except that the processing by the control unit 15 is different. As shown in Figure 6, in the second embodiment, step S16 is added after step S12.

[0036] In step S16, the (N-1) measured resonance times T3 obtained by repeating the loop processing in steps S11 and S12 are averaged. Then, the process moves to step S13, where the SW timing T1 is calculated using the averaged resonance time T3. In this way, by using the averaged resonance time T3, the SW timing T1 can be determined with higher accuracy.

[0037] (Third embodiment) The configuration of the power converter in the third embodiment is the same as in the first embodiment, except that the processing by the control unit 15 is different. As shown in Figure 7, in the third embodiment, step S17 is added in place of step S7. In step S17, machine learning is applied to the boost time T2 and resonance time T3 measured in the current switching control, as well as information on boost time T2 and resonance time T3 obtained from past switching controls.

[0038] In machine learning, the temperature characteristics and aging changes of each constant of the resonant inductor Lr and resonant capacitor Cr are learned from parameter information such as the water temperature of the cooling water used to cool heat-generating parts such as power devices and drive ICs in the drive system, and the cumulative operating time. This allows for the estimation of the boost time T2 and resonance time T3 used in switching control. By applying machine learning to the estimation of times T2 and T3 in this way, it is possible to reflect in the estimation the fluctuations of times T2 and T3 that correspond to the operating conditions specific to the system to which it is applied.

[0039] (Other embodiments) The number of legs can be two or more, and the SW timing T1 can be calculated similarly for each leg. The main and auxiliary switches may be composed of other power devices besides MOSFETs, such as using IGBTs only for main switches S1 and S2, IGBTs only for auxiliary switches A1 and A2, or IGBTs for main switches S1 and S2 and auxiliary switches A1 and A2. This disclosure is described in accordance with the embodiments, but it is understood that this disclosure is not limited to such embodiments or structures. This disclosure also includes various modifications and variations within the equivalence. In addition, various combinations and forms, as well as other combinations and forms that include only one, more, or fewer of those elements, fall within the scope and concept of this disclosure. [Explanation of symbols]

[0040] In the drawing, 1 is a leg, 2 and 3 are smoothing capacitors, 4 is a DC power supply, 5 is a load, 6 is a current sensor, 7 and 8 are voltage sensors, 11 is a power converter, 12 is a control device, 13 is a memory unit, 14 is a correction unit, 15 is a control unit, 16 is a time measurement unit, S1 is the high-potential side main switch, S2 is the low-potential side main switch, A1 and A2 are auxiliary switches, Lr is a resonant inductor, and Cr is a resonant capacitor.

Claims

1. A series circuit of a high-potential side main switch (S1) and a low-potential side main switch (S2), A resonant capacitor (Cr) is connected in parallel to the high-potential main switch and the low-potential main switch, respectively. A power conversion unit (11) having one or more legs (1) comprising two auxiliary switches (A1, A2) that constitute a bidirectional switch, each having one end connected to the common connection point of the high-potential side main switch and the low-potential side main switch, and the other end connected to a common connection point, with the drain or emitter or source or collector common to both transistors, and a series circuit of a resonant inductor (Lr), A power supply voltage detection unit (8) detects the DC power supply voltage supplied to this power conversion unit, A current detection unit (6) detects the load current supplied from the power conversion unit to the load (5), A terminal voltage detection unit (7) detects the voltage between the conductive terminals of the main switch, The power conversion unit comprises a control unit (15) that controls the switching of each switch constituting the power conversion unit, The control unit controls the leg to perform soft switching, The resonant operation that occurs when the main switch is turned on is performed multiple times. Based on the power supply voltage and the load current, the time from when the auxiliary switch is turned on until the voltage across the terminals of the corresponding main switch starts to rise from zero V is measured as the boost time. The time from when the voltage between one terminal of the high-potential main switch and the low-potential main switch starts rising from zero V until the voltage between the other terminal drops to zero V is measured as the first resonance time, and the time from when the voltage between the other terminal starts rising from zero V until the voltage between the one terminal drops to zero V is measured as the second resonance time. The system includes a storage unit (13) that stores the boost time, the first resonance time, and the second resonance time. A power converter that corrects the timing of switching the main switch based on the boost time, the first resonance time, and the second resonance time.

2. The power converter according to claim 1, wherein the control unit uses the average value of the resonance time measured for multiple resonance operations for the correction.

3. The control unit switches the resonant operation to be performed once or multiple times depending on the conditions. When the aforementioned resonant operation is set to a single cycle, the time from when the voltage between one terminal of the high-potential side main switch and the low-potential side main switch starts to rise from zero V until the voltage between the other terminal drops to zero V is measured as the resonant time. The resonance time is stored in the memory unit. The power converter according to claim 1 or 2, wherein the timing for switching the main switch is corrected based on the boost time and the resonance time.

4. The control unit sets the resonant operation to be performed to a single time if the output from the power conversion unit to the load exceeds a threshold value. The power converter according to claim 3, wherein, when the output is low and below the threshold, the power converter switches to setting the number of times to perform the resonance operation to be executed to multiple times.

5. The control unit stores multiple sets of resonance time data measured in past control operations in the storage unit. The power converter according to claim 3, wherein machine learning is performed on the data from the multiple trials, with at least the characteristics of the constants of the resonant capacitor and the resonant inductor as parameters, and the timing of switching the main switch is corrected by also considering the boost time and resonance time obtained as a result.

6. A series circuit of a high-potential side main switch and a low-potential side main switch, A resonant capacitor is connected in parallel to the high-potential main switch and the low-potential main switch, respectively. A power conversion unit comprising one or more legs having a series circuit of two auxiliary switches and a resonant inductor, each consisting of two transistors with a common drain or emitter, one end of which is connected to the common connection point of the high-potential side main switch and the low-potential side main switch, and the other end of which is connected to a common connection point, the two transistors having a common drain or emitter, and constituting a bidirectional switch, The DC power supply voltage supplied to the power conversion unit is detected, The load current supplied to the load from the power conversion unit is detected, The voltage between the conductive terminals of the main switch is detected, The aforementioned leg is controlled to perform soft switching, The resonant operation that occurs when the main switch is turned on is performed multiple times. Based on the power supply voltage and the load current, the time from when the auxiliary switch is turned on until the voltage across the terminals of the corresponding main switch starts to rise from zero V is measured as the boost time. The time from when the voltage between one terminal of the high-potential main switch and the low-potential main switch starts rising from zero V until the voltage between the other terminal drops to zero V is measured as the first resonance time, and the time from when the voltage between the other terminal starts rising from zero V until the voltage between the one terminal drops to zero V is measured as the second resonance time. The boost time, as well as the first resonance time and the second resonance time, are stored. A power conversion method for correcting the timing of switching the main switch based on the boost time, the first resonance time, and the second resonance time.

7. The power conversion method according to claim 6, wherein the average value of the resonance time measured for multiple resonance operations is used for the correction.

8. The resonant operation to be performed can be switched between a single or multiple times depending on the conditions. When the aforementioned resonant operation is set to a single cycle, the time from when the voltage between one terminal of the high-potential side main switch and the low-potential side main switch starts to rise from zero V until the voltage between the other terminal drops to zero V is measured as the resonant time. The aforementioned resonance time is stored, The power conversion method according to claim 6 or 7, wherein the timing of switching the main switch is corrected based on the boost time and the resonance time.

9. If the output from the power conversion unit to the load exceeds a threshold, the resonant operation to be performed is set to a single cycle. The power conversion method according to claim 8, wherein, when the output is low and below the threshold, the method switches to setting the number of times to perform the resonance operation to be executed to multiple times.

10. The system stores multiple sets of resonance time data measured in past control operations. The power conversion method according to claim 8, wherein machine learning is performed on the data from the multiple trials, with at least the characteristics of the constants of the resonant capacitor and the resonant inductor as parameters, and the timing of switching the main switch is corrected by also considering the boost time and resonance time obtained as a result.

Images