JP2018011432A - Dc/dc conversion device, computer program, and abnormality determination method for dc/dc conversion device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DC/DC conversion device, a computer program, and an abnormality determination method for the DC/DC conversion device, capable of determining abnormalities of a resonance capacitor.SOLUTION: A DC/DC conversion device comprises: a switching device that turns on and off a current flowing from an input side to an output side; a resonance inductor connected in series to the switching device; a plurality of parallel-connected resonance capacitors that configure a resonance circuit together with the resonance inductor; a controller that on/off-controls the switching device; and a determination unit that determines presence or absence of abnormalities of some of the plurality of parallel-connected resonance capacitors on the basis of whether or not a predetermined condition is satisfied.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a DC / DC converter, a computer program for determining an abnormality of the DC / DC converter, and an abnormality determination method of the DC / DC converter.

  A DC / DC converter that converts a direct-current voltage on the input side into a direct-current voltage on the output side is used in in-vehicle devices and industrial devices. In recent years, there is a high demand for miniaturization of in-vehicle equipment and industrial equipment, and the operating frequency (switching frequency) of the DC / DC converter is reduced due to miniaturization of passive elements (for example, inductors, capacitors, etc.) used in the DC / DC converter. It is getting higher. However, when the operating frequency is increased, the switching loss of the switching device increases.

  Therefore, zero current switching (ZCS) is performed to turn off the energization switch when the resonance current flowing through the energization switch becomes zero due to resonance of the resonance circuit composed of the resonance inductor and the resonance capacitor. Thus, a current resonance type DC / DC converter that reduces switching loss during turn-off is disclosed (see Patent Document 1).

JP 2007-74828 A

  In a conventional DC / DC converter such as Patent Document 1, since a large current flows through a resonance capacitor, a plurality of capacitors may be connected in parallel to distribute the current. However, a method for quickly determining a failure when some of a plurality of capacitors have failed has not been shown so far.

  The present invention has been made in view of such circumstances, and a DC / DC converter that can determine an abnormality of a resonance capacitor, a computer program for determining an abnormality of the DC / DC converter, and a DC / DC It is an object of the present invention to provide an abnormality determination method for a DC converter.

  A DC / DC converter according to an embodiment of the present invention includes a switching device for turning on / off a current flowing from an input side to an output side, a resonant inductor connected in series to the switching device, and a resonance with the resonant inductor. A plurality of parallel-connected resonance capacitors constituting a circuit, a control unit that controls on / off of the switching device, and one of the plurality of parallel-connected resonance capacitors based on whether or not a predetermined condition is satisfied A determination unit that determines whether there is an abnormality in the resonance capacitor of the unit.

  A computer program according to an embodiment of the present invention causes a computer to resonate with a switching device that turns on / off a current flowing from the input side to the output side, a resonant inductor connected in series to the switching device, and the resonant inductor. A computer program for determining an abnormality of a DC / DC converter comprising a plurality of resonant capacitors connected in parallel constituting a circuit and a control unit for controlling on / off of the switching device, the computer comprising: Based on whether or not a predetermined condition is satisfied, it functions as a determination unit that determines whether or not there is an abnormality in some of the plurality of parallel-connected resonance capacitors.

  An abnormality determination method for a DC / DC converter according to an embodiment of the present invention includes a switching device for turning on / off a current flowing from an input side to an output side, a resonant inductor connected in series to the switching device, An abnormality determination method for a DC / DC conversion apparatus, comprising: a plurality of parallel-connected resonance capacitors that form a resonance circuit together with a resonance inductor; and a control unit that controls on / off of the switching device. The determination unit determines whether there is an abnormality in some of the plurality of parallel-connected resonance capacitors based on whether or not to do so.

  According to the present invention, it is possible to determine abnormality of the resonance capacitor.

It is explanatory drawing which shows an example of a structure of the DC / DC converter of 1st Embodiment. It is explanatory drawing which shows an example of the waveform of the resonant current which flows into a resonant inductor. It is explanatory drawing which shows an example of the specific information memorize | stored in the memory | storage part of the DC / DC converter of 1st Embodiment. It is explanatory drawing which shows an example of the mode of the change of the resonant current based on the normal / abnormality of a resonant capacitor. It is a flowchart which shows an example of the process sequence of the abnormality determination method by the DC / DC converter of 1st Embodiment. It is explanatory drawing which shows an example of a structure of the DC / DC converter of 2nd Embodiment. It is explanatory drawing which shows an example of the mode of the change of the resonant current based on the normal / abnormality of a resonant capacitor. It is a flowchart which shows an example of the process sequence of the abnormality determination method by the DC / DC converter of 2nd Embodiment. It is a flowchart which shows an example of the process sequence of the abnormality determination method by the DC / DC converter of 2nd Embodiment. It is explanatory drawing which shows an example of a structure of the DC / DC converter of 3rd Embodiment. It is explanatory drawing which shows an example of the mode of the change of the resonant current based on the normal / abnormality of a resonant capacitor. It is a flowchart which shows an example of the process sequence of the abnormality determination method by the DC / DC converter of 3rd Embodiment. It is a flowchart which shows an example of the process sequence of the abnormality determination method by the DC / DC converter of 3rd Embodiment. It is explanatory drawing which shows an example of the waveform of the resonant current in case a resonant capacitor is normal. It is explanatory drawing which shows an example of the waveform of the resonant current in case a resonant capacitor is abnormal.

[Description of Embodiment of Present Invention]
A DC / DC converter according to an embodiment of the present invention includes a switching device for turning on / off a current flowing from an input side to an output side, a resonant inductor connected in series to the switching device, and a resonance with the resonant inductor. A plurality of parallel-connected resonance capacitors constituting a circuit, a control unit that controls on / off of the switching device, and one of the plurality of parallel-connected resonance capacitors based on whether or not a predetermined condition is satisfied A determination unit that determines whether there is an abnormality in the resonance capacitor of the unit.

  A computer program according to an embodiment of the present invention causes a computer to resonate with a switching device that turns on / off a current flowing from the input side to the output side, a resonant inductor connected in series to the switching device, and the resonant inductor. A computer program for determining an abnormality of a DC / DC converter comprising a plurality of resonant capacitors connected in parallel constituting a circuit and a control unit for controlling on / off of the switching device, the computer comprising: Based on whether or not a predetermined condition is satisfied, it functions as a determination unit that determines whether or not there is an abnormality in some of the plurality of parallel-connected resonance capacitors.

  An abnormality determination method for a DC / DC converter according to an embodiment of the present invention includes a switching device for turning on / off a current flowing from an input side to an output side, a resonant inductor connected in series to the switching device, An abnormality determination method for a DC / DC conversion apparatus, comprising: a plurality of parallel-connected resonance capacitors that form a resonance circuit together with a resonance inductor; and a control unit that controls on / off of the switching device. The determination unit determines whether there is an abnormality in some of the plurality of parallel-connected resonance capacitors based on whether or not to do so.

  The switching device turns on / off current flowing from the input side to the output side. The switching device is, for example, a device such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The resonant inductor is connected in series with the switching device. A plurality of resonant capacitors connected in parallel constitute a resonant circuit together with a resonant inductor. The control unit controls on / off of the switching device.

  The determination unit determines whether or not there is an abnormality in some of the resonance capacitors connected in parallel based on whether or not a predetermined condition is satisfied. The abnormality of some resonance capacitors can be, for example, an open failure of some resonance capacitors. For example, when one resonance capacitor among a plurality of resonance capacitors connected in parallel has an open failure, the combined capacitance of the resonance capacitors connected in parallel becomes small. For this reason, the resonance period of the resonance current changes (shortens). Therefore, it is possible to determine abnormality of the resonance capacitor by providing a predetermined condition that captures the change of the resonance current.

  A DC / DC converter according to an embodiment of the present invention includes a device temperature acquisition unit that acquires the temperature of the switching device, a reference temperature acquisition unit that acquires a reference temperature at a predetermined location, and a current acquisition that acquires an output current. A storage unit that stores specific information that preliminarily specifies the relationship between the temperature of the switching device, the reference temperature, and the output current, the reference temperature acquired by the reference temperature acquisition unit, and the output current acquired by the current acquisition unit And a temperature specifying unit that specifies the temperature of the switching device based on the specifying information, and the determination unit determines a temperature difference between the temperature acquired by the device temperature acquiring unit and the temperature specified by the temperature specifying unit. Based on this, it is determined whether or not the resonance capacitor is abnormal.

  The device temperature acquisition unit acquires the temperature of the switching device. The temperature of the switching device can be obtained by providing a temperature sensor at or near the switching device. The reference temperature acquisition unit acquires a reference temperature at a predetermined location. The predetermined location may be a location where the atmospheric temperature of the switching device can be obtained, and can be, for example, a substrate in a DC / DC converter. The reference temperature can be acquired by providing a temperature sensor at a predetermined location.

  The current acquisition unit acquires the output current of the DC / DC converter. For example, a shunt resistor can be used to acquire the output current. The storage unit stores specific information that specifies in advance the relationship between the temperature of the switching device, the reference temperature, and the output current. The temperature specifying unit specifies the temperature of the switching device corresponding to the reference temperature acquired by the reference temperature acquisition unit and the output current acquired by the current acquisition unit with reference to the specific information stored in the storage unit.

  The determination unit determines whether the resonance capacitor is abnormal based on a temperature difference between the temperature acquired by the device temperature acquisition unit and the temperature specified by the temperature specifying unit. The control unit performs so-called zero current switching (ZCS) in which the switching device is turned off in a state where the resonance current flowing through the resonance inductor (that is, the current flowing through the switching device) becomes zero or negative. For this reason, when the resonant capacitor is normal, zero current switching is performed, so that the loss of the switching device is small and the temperature rise is also below a predetermined temperature. However, if one resonance capacitor is abnormal (open failure), the resonance period of the resonance current changes, so zero current switching cannot be performed, the switching device loss increases, and the temperature rise also exceeds the predetermined temperature. become. Therefore, when the temperature difference between the acquired temperature and the specified temperature exceeds a predetermined temperature threshold (for example, 20 ° C., 30 ° C., etc.), it can be determined that the resonance capacitor is abnormal.

  A DC / DC converter according to an embodiment of the present invention includes a resonance current acquisition unit that acquires a resonance current flowing through the switching device and the resonance inductor, and a point when the resonance current becomes zero from when the switching device is turned on. A storage unit that stores in advance the reference conduction time until the resonance current acquired by the resonance current acquisition unit becomes zero from the time when the switching device is turned on and the reference Whether or not the resonance capacitor is abnormal is determined based on a time difference from the conduction time.

  The resonance current acquisition unit acquires a resonance current flowing through the switching device and the resonance inductor. For obtaining the resonance current, for example, a shunt resistor connected in series with the resonance inductor can be used. The storage unit stores in advance a reference conduction time from when the switching device is turned on to when the resonance current becomes zero. The reference conduction time can be obtained by specifying a point in time when the acquired resonance current becomes zero when the resonance capacitor is normal.

  The determination unit determines whether there is an abnormality in the resonance capacitor based on a time difference between the conduction time from the time when the switching device is turned on to the time when the resonance current acquired by the resonance current acquisition unit becomes zero and the reference conduction time. The reference conduction time when the resonant capacitor is normal is T0. When one resonance capacitor is abnormal (open failure), the resonance period of the resonance current is shortened, so that the conduction time is shorter than the reference conduction time T0. Therefore, when the time difference between the conduction time based on the acquired resonance current and the reference conduction time T0 exceeds a predetermined time threshold, it can be determined that the resonance capacitor is abnormal.

  A DC / DC converter according to an embodiment of the present invention includes a resonance current acquisition unit that acquires a resonance current flowing through the switching device and the resonance inductor, and a resonance at a time when a predetermined time has elapsed since the switching device was turned on. A storage unit that stores a reference current value of current in advance, and the determination unit includes a resonance current acquired by the resonance current acquisition unit when the predetermined time elapses from the time when the switching device is turned on, and the reference current value. The presence or absence of abnormality of the resonant capacitor is determined based on the current difference.

  The resonance current acquisition unit acquires a resonance current flowing through the switching device and the resonance inductor. For obtaining the resonance current, for example, a shunt resistor connected in series with the resonance inductor can be used. The storage unit stores in advance a reference current value of the resonance current when a predetermined time has elapsed since the switching device was turned on. When one resonance capacitor is abnormal (open failure), the resonance period of the resonance current changes, so the instantaneous value of the resonance current also changes. The predetermined time elapse time can be, for example, a time when the current difference between the instantaneous value of the normal resonance current and the instantaneous value of the abnormal resonance current becomes large. The reference current value of the resonance current is a current value when the resonance capacitor is normal.

  The determination unit determines whether there is an abnormality in the resonance capacitor based on a current difference between the resonance current acquired by the resonance current acquisition unit and a reference current value when a predetermined time has elapsed since the switching device was turned on. When one resonance capacitor is abnormal (open failure), the resonance period of the resonance current is shortened, so the instantaneous value of the resonance current also changes. Therefore, when the current difference between the resonance current acquired at the time when the predetermined time has elapsed from when the switching device is turned on and the reference current value is larger than the predetermined current threshold, it can be determined that the resonance capacitor is abnormal.

  In the DC / DC converter according to the embodiment of the present invention, the error of the resonance current is Ie, the predetermined time lapse time is Tz, the inductance of the resonance inductor is L, and the amplitude of the AC component of the resonance current is When the output current is I, the combined capacitance C of the plurality of resonance capacitors connected in parallel and the capacitance Cd of one resonance capacitor are Ie <I + Ir · sin {Tz / √ [L · (C -Cd)]} is satisfied.

  When a resonance current error is Ie, a predetermined time point is Tz, an inductance of the resonance inductor is L, an amplitude of an alternating current component of the resonance current is Ir, and an output current is I, a plurality of resonances connected in parallel The combined capacitance C of the capacitor and the capacitance Cd of one resonance capacitor satisfy the equation Ie <I + Ir · sin {Tz / √ [L · (C−Cd)]}.

  When the resonant capacitor is normal, the time from when the switching device is turned on to when the resonant current becomes zero is T0, and from when the switching device is turned on to when the resonant current becomes negative from zero and becomes zero again. If the time (equal to the resonance period of the resonance current) is Tn, the instantaneous value of the resonance current is 0 or negative between time T0 and time Tn. On the other hand, if one resonant capacitor is open-failed, the combined capacitance of the resonant capacitor is reduced and the resonant period of the resonant current is shortened. Therefore, the instantaneous value of the resonant current when the time Tn elapses from when the switching device is turned on. There are cases where are positive. Therefore, when the predetermined time elapses Tz, the instantaneous value of the resonance current at the predetermined time elapse Tz when the resonance capacitor is normal becomes ≦ 0, and the resonance at the predetermined time elapse Tz when the resonance capacitor is abnormal The instantaneous value of current can be set to be> 0.

  The resonance current error Ie is a detection error by a current sensor such as a shunt resistor. (C-Cd) is a combined capacitance of the resonance capacitors when one of the plurality of resonance capacitors has an open failure. That is, I + Ir · sin {Tz / √ [L · (C−Cd)]} represents an instantaneous value of the resonance current at a predetermined time Tz when one resonance capacitor has an open failure. In an ideal case where there is no error in the resonance current, if the equation 0 <I + Ir · sin {Tz / √ [L · (C−Cd)]} is satisfied, the resonance capacitor is determined based on the instantaneous value of the resonance current. It can be determined that there is an abnormality. Therefore, if the equation of Ie <I + Ir · sin {Tz / √ [L · (C−Cd)]} is satisfied, the resonance capacitor can be determined based on the instantaneous value of the resonance current even when the resonance current error Ie exists. It can be determined that there is an abnormality.

  In the DC / DC converter according to the embodiment of the present invention, the combined capacitance C satisfies the equation −Ie ≧ I + Ir · sin {Tz / √ (L · C)}.

  Further, the combined capacitance C satisfies the equation −Ie ≧ I + Ir · sin {Tz / √ (L · C)}. I + Ir · sin {Tz / √ (L · C)} represents an instantaneous value of the resonance current at a predetermined time point Tz when the resonance capacitor is normal. In an ideal case where there is no error in the resonance current, if the equation 0 ≧ I + Ir · sin {Tz / √ (L · C)} is satisfied, the resonance capacitor is normal based on the instantaneous value of the resonance current. Can be determined. Therefore, if the equation −Ie ≧ I + Ir · sin {Tz / √ (L · C)} is satisfied, the resonance capacitor is normal based on the instantaneous value of the resonance current even when the resonance current error Ie exists. Can be determined.

  In the DC / DC converter according to the embodiment of the present invention, the control unit stops turning on / off the switching device when the determination unit determines that the resonance capacitor is abnormal.

  When the determination unit determines that the resonance capacitor is abnormal, the control unit stops turning on / off the switching device. As a result, if there is an abnormality in some of the plurality of resonance capacitors, the switching operation of the DC / DC converter is stopped, so that the abnormality can be detected promptly and overcurrent to other normal resonance capacitors is also possible. Can be prevented.

[Details of the embodiment of the present invention]
(First embodiment)
Hereinafter, the present invention will be described with reference to the drawings illustrating embodiments. FIG. 1 is an explanatory diagram illustrating an example of the configuration of the DC / DC conversion apparatus 100 according to the first embodiment. The DC / DC converter 100 according to the first embodiment includes input terminals G1 and G2 and output terminals G3 and G4. The input voltage applied to the input terminals G1 and G2 is stepped down and output from the output terminals G3 and G4. To do. The input terminal G2 is connected to the output terminal G4.

  The input terminal G1 is connected to the drain of the switching device 10 for turning on / off the current flowing from the input side to the output side. One end of the resonant inductor 11 is connected to the source of the switching device 10. That is, the switching device 10 and the resonant inductor 11 are connected in series. Hereinafter, the switching device 10 will be described as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). The switching device 10 includes a diode connected in antiparallel between the source and the drain.

  Between the other end of the resonant inductor 11 and the input terminal G2, a resonant capacitor 12 that constitutes a resonant circuit together with the resonant inductor 11 is connected. The resonant capacitor 12 is formed by connecting a plurality of resonant capacitors 121, 122, and 123 (three in the example of FIG. 1 but the number of parallels is not limited to three) in parallel. An inductor 14 is connected between the connection point of the resonant inductor 11 and the resonant capacitor 12 and the output terminal G3. A capacitor 15 is connected between the output terminals G3 and G4. Further, the cathode of the diode 13 is connected to the connection point of the resonant inductor 11 and the resonant capacitor 12, and the anode of the diode 13 is connected to the output terminal G4.

  The resonant inductor 11 and the resonant capacitor 12 are provided to realize zero current switching (ZCS) of the switching device 10.

  A current detector 21 that detects an output current is connected to the output terminal G3. The current detection unit 21 can be configured with, for example, a shunt resistor. The current detection unit 21 outputs the detected current to the control unit 30.

  A temperature sensor 22 is provided at or near the switching device 10. The temperature sensor 22 detects the temperature of the switching device 10 and outputs the detected temperature to the control unit 30. A temperature sensor 23 is provided at a predetermined location of the DC / DC converter 100. The predetermined location may be a location where the ambient temperature of the switching device 10 can be obtained, and may be, for example, a substrate (not shown) in the DC / DC converter 100. The temperature sensor 23 detects the reference temperature and outputs the detected reference temperature to the control unit 30.

  The control unit 30 includes a current acquisition unit 31, a reference temperature acquisition unit 32, a device temperature acquisition unit 33, a temperature specification unit 34, a storage unit 35, a determination unit 36, a control unit 37, and the like.

  The control unit 37 controls on / off of the switching device 10. That is, when the switching device 10 is turned on, a current flows through the switching device 10 due to an input voltage between the input terminals G1 and G2, and an output current is output from the output terminal G3 via the inductors 11 and 14. Energy is stored in the inductor 14 while a current flows. When the switching device 10 is turned off, current flows through the inductor 14, the output terminal G3, and the output terminal G4 via the diode 13 by the energy stored in the inductor 14. By repeating ON / OFF of the switching device 10, an output voltage obtained by stepping down the input voltage is output from between the output terminals G3 and G4.

  Further, the control unit 37 controls the timing at which the switching device 10 is turned off in order to realize zero current switching. Hereinafter, zero current switching will be described.

  FIG. 2 is an explanatory diagram showing an example of a waveform of a resonance current flowing through the resonance inductor 11. The horizontal axis indicates time, and the vertical axis indicates current. When the resonance current flowing through the resonance inductor 11 is i, the resonance current i can be expressed by Expression (1).

  Here, I represents an output current flowing through the output terminal G3, Ir is the amplitude of the alternating current component of the resonance current i, and w is the resonance angular frequency of the resonance circuit including the resonance inductor 11 and the resonance capacitor 12. The resonance angular frequency w can be expressed by Equation (2). Here, L is the inductance of the resonant inductor 11, and C is the capacitance (synthetic capacitance) of the resonant capacitor 12. If the capacitances of the resonance capacitors 121, 122, and 123 are Cd, C = 3 × Cd.

  In FIG. 2, T0 is the time when the resonance current i ≧ 0, T1 is the time from i = 0 to i = I, and Tn is the period of the resonance current i. As can be seen from FIG. 2, the relationship of equation (3) is established. From Formula (3), T1 can be represented by Formula (4).

  Further, the amplitude Ir of the alternating current component of the resonance current i can be expressed by Expression (5). Here, Zn is a characteristic impedance and can be expressed by Equation (6). V is an input voltage applied to the input terminals G1 and G2. When Expression (5) is substituted into Expression (4), Expression (4) can be expressed by Expression (7).

  Further, the equation (8) is established from FIG. Here, when I = 0, T1 = 0 and T0 = Tn / 2. When I = Ir, T0 = Tn. From equation (8), when I = 0, T1 = 0, and when I = Ir, T1 = Tn / 4. That is, when I changes from 0 to Ir, T1 changes from 0 to Tn / 4. When this change in T1 is approximated by a linear function of I, equation (9) is obtained from equation (7).

  Substituting equation (9) into equation (8) yields equation (10). The period Tn of the resonance current i can be expressed by Expression (11). By substituting equation (11) into equation (10), the energization time T0 can be calculated by equation (12).

  As shown in FIG. 2, since the resonance current i ≦ 0 and the current does not flow from the drain to the source of the switching device 10 during the time period from the time T0 to the time Tn, zero current switching can be performed ( ZCS formation range).

  The determination unit 36 determines whether or not there is an abnormality in some of the resonance capacitors 121, 122, and 123 connected in parallel based on whether or not a predetermined condition is satisfied. The abnormality of some resonance capacitors can be, for example, an open failure of some resonance capacitors. For example, when one of the plurality of resonant capacitors 121, 122, 123 connected in parallel has an open failure, the combined capacitance of the resonant capacitors connected in parallel decreases.

  For example, when the resonant capacitor 121 has an open failure, the combined capacitance of the resonant capacitor 12 is changed from C to (C-Cd). For this reason, the resonance period of the resonance current changes (shortens). Therefore, it is possible to determine abnormality of the resonant capacitor 12 by providing a predetermined condition that captures a change in the resonant current.

  Next, a method for determining whether or not a predetermined condition is satisfied will be described in detail. Whether or not the predetermined condition is satisfied is, for example, (1) based on the temperature of the switching device 10, (2) based on the time when the resonance current becomes zero (conduction time when the resonance current is positive), (3) It may be based on the instantaneous value of the resonance current. First, a case based on the temperature of the switching device 10 will be described.

  The device temperature acquisition unit 33 acquires the temperature of the switching device 10 from the temperature sensor 22. The temperature of the switching device 10 is the temperature of the switching device 10 or its vicinity.

  The reference temperature acquisition unit 32 acquires a reference temperature at a predetermined location from the temperature sensor 23. The predetermined location may be a location where the ambient temperature of the switching device 10 can be obtained, and may be, for example, a substrate in the DC / DC converter 100.

  The current acquisition unit 31 acquires the output current of the DC / DC conversion device 100 from the current detection unit 21.

  The storage unit 35 stores specific information that specifies in advance the relationship between the temperature of the switching device 10, the reference temperature, and the output current.

  FIG. 3 is an explanatory diagram illustrating an example of the specific information stored in the storage unit 35 of the DC / DC conversion apparatus 100 according to the first embodiment. As shown in FIG. 3, the specific information indicates a correspondence relationship between the output current, the reference temperature, and the temperature of the switching device 10 (also referred to as device temperature) when the resonant capacitor 12 is normal. For example, when the output current is I1 and the reference temperature is tr1, the device temperature is td11. The same applies to the other output currents, the reference temperature, and the temperature of the switching device 10.

  The temperature identification unit 34 refers to the identification information stored in the storage unit 35 and identifies the temperature of the switching device 10 corresponding to the reference temperature acquired by the reference temperature acquisition unit 32 and the output current acquired by the current acquisition unit 31. . For example, when the output current acquired by the current acquisition unit 31 is I1 and the reference temperature acquired by the reference temperature acquisition unit 32 is tr1, the temperature specifying unit 34 specifies that the device temperature is td11.

  The determination unit 36 determines whether there is an abnormality in the resonant capacitor 12 based on the temperature difference between the temperature acquired by the device temperature acquisition unit 33 and the temperature specified by the temperature specifying unit 34.

  FIG. 4 is an explanatory diagram illustrating an example of a change in the resonance current based on normality / abnormality of the resonance capacitor 12. The upper diagram of FIG. 4 shows the waveform of the resonance current, the solid line is the resonance current when the resonance capacitor 12 is normal, and the broken line is the resonance current when the resonance capacitor 12 is abnormal. The lower diagram shows the on / off state of the switching device 10.

  The control unit 37 performs so-called zero current switching (ZCS) in which the switching device 10 is turned off in a state where the resonance current flowing through the resonance inductor 11 (that is, the switching device 10) becomes zero or negative. In the example of FIG. 4, the switching device 10 is turned on at time t1 and turned off at time t2 within the ZCS establishment range. At time t2, the resonance current is negative. When the resonant capacitor 12 is normal, zero current switching is performed, so that the loss of the switching device 10 is small and the temperature rise is also below a predetermined temperature.

  However, when one resonance capacitor is abnormal (open failure), the resonance period of the resonance current changes (shortens). As shown in FIG. 4, since the resonance period of the resonance current changes, the resonance current becomes larger than zero at time t2, and zero current switching cannot be performed. For this reason, the loss of the switching device 10 becomes large and the temperature rise also exceeds the predetermined temperature.

  Therefore, when the temperature difference between the acquired temperature and the specified temperature exceeds a predetermined temperature threshold (for example, 20 ° C., 30 ° C., etc.), it can be determined that the resonance capacitor 12 is abnormal.

  When the determination unit 36 determines that the resonance capacitor 12 is abnormal, the control unit 37 stops turning on / off the switching device 10. As a result, if there is an abnormality in some of the plurality of resonance capacitors 121, 122, 123, the switching operation of the DC / DC converter 100 is stopped, so that the abnormality can be detected promptly and other normal resonances. An overcurrent to the capacitor can also be prevented.

  Next, the operation of the DC / DC converter 100 of the first embodiment will be described. FIG. 5 is a flowchart illustrating an example of a processing procedure of the abnormality determination method performed by the DC / DC converter 100 according to the first embodiment. Hereinafter, for the sake of convenience, the subject of processing will be described as the control unit 30. The control unit 30 operates the DC / DC converter 100 to acquire an output current (S11) and acquire a reference temperature (S12).

  The control unit 30 specifies the temperature of the switching device 10 based on the acquired output current and the reference temperature (S13). The control unit 30 acquires the temperature of the switching device 10 (S14), and determines whether the temperature difference between the acquired temperature and the specified temperature is greater than a predetermined temperature threshold (S15).

  If the temperature difference is larger than the predetermined temperature threshold (YES in S15), the control unit 30 determines that an open failure of the resonance capacitor (S16), and performs the process of step S17 described later. If the temperature difference is not greater than the predetermined temperature threshold (NO in S15), the control unit 30 determines whether to end the process without performing the process of step S16 (S17). When it is determined that the process is not to be ended (NO in S17), the control unit 30 continues the process after step S11, and when it is determined that the process is to be ended (YES in S17), the process is ended.

(Second Embodiment)
In the second embodiment, a method for determining whether or not the above-described predetermined condition is satisfied based on the time when the resonance current becomes zero (the conduction time during which the resonance current is positive) will be described.

  FIG. 6 is an explanatory diagram illustrating an example of the configuration of the DC / DC conversion apparatus 120 according to the second embodiment. The difference from the case of the first embodiment is that, instead of the temperature sensors 22 and 23, the reference temperature acquisition unit 32, the device temperature acquisition unit 33, the temperature specification unit 34, and the storage unit 35, the voltage detection unit 24 and the resonance current detection Unit 25, voltage acquisition unit 38, resonance current acquisition unit 39, conduction time management unit 40, and storage unit 41. In addition, the same code | symbol is attached | subjected to the structure similar to 1st Embodiment, and description is abbreviate | omitted.

  A resonance current detector 25 for detecting a resonance current is connected in series with the resonance inductor 11. The resonance current detection unit 25 can be configured with, for example, a shunt resistor. The resonance current detection unit 25 outputs the detected resonance current to the control unit 30.

  A voltage detector 24 that detects an input voltage is connected between the input terminals G1 and G2. The voltage detection unit 24 can be a series circuit including a plurality of resistors connected between the input terminals G1 and G2, for example. The voltage detection unit 24 outputs the detected voltage to the control unit 30.

  The resonance current acquisition unit 39 acquires the resonance current flowing from the resonance current detection unit 25 to the resonance inductor 11. Further, the voltage acquisition unit 38 acquires the input voltage from the voltage detection unit 24.

  The conduction time management unit 40 specifies the reference conduction time from the time when the switching device 10 is turned on to the time when the resonance current becomes zero, based on the time when the resonance current acquired by the resonance current acquisition unit 39 becomes zero. The reference conduction time is the time from when the switching device 10 is turned on to when the resonance current becomes zero when the resonance capacitor 12 is normal, and is, for example, the time T0 illustrated in FIG.

  The conduction time management unit 40 stores the reference conduction time in the storage unit 41 in association with the output current and the input voltage acquired at or near the time when the resonance current acquired by the resonance current acquisition unit 39 becomes zero.

  The storage unit 41 stores a reference conduction time from when the switching device 10 is turned on to when the resonance current becomes zero when the resonance capacitor 12 is normal. As can be seen from the equation (12), the reference conduction time can change according to the output current and the input voltage, so the storage unit 41 stores the reference conduction time in association with the output current and the input voltage.

  Based on the time when the resonance current acquired by the resonance current acquisition unit 39 becomes zero, the determination unit 36 specifies the conduction time from the time when the switching device 10 is turned on to the time when the resonance current becomes zero. Then, the determination unit 36 determines whether there is an abnormality in the resonant capacitor 12 based on the time difference between the specified conduction time and the reference conduction time stored in the storage unit 41.

  FIG. 7 is an explanatory diagram illustrating an example of a change in the resonance current based on normality / abnormality of the resonance capacitor 12. The solid line is the resonance current when the resonance capacitor 12 is normal, and the broken line is the resonance current when the resonance capacitor 12 is abnormal. As shown in FIG. 7, the reference conduction time when the resonant capacitor 12 is normal is T0. When the resonance capacitor 12 is abnormal (open failure), the resonance period of the resonance current is shortened, so that the conduction time is shorter than the reference conduction time T0. In the example of FIG. 7, the conduction time when the resonance capacitor 12 is abnormal is set to TE0.

  For example, assuming that the combined capacitance when the resonant capacitor 12 is normal is C and the capacitance of the resonant capacitor that has an open failure is Cd, the conduction time TE0 when the resonant capacitor 12 is abnormal can be expressed by Expression (13). .

  As described above, when the time difference ΔT between the conduction time based on the acquired resonance current and the reference conduction time T0 exceeds a predetermined time threshold, it can be determined that the resonance capacitor 12 is abnormal.

  When the determination unit 36 determines that the resonance capacitor 12 is abnormal, the control unit 37 stops turning on / off the switching device 10. As a result, if there is an abnormality in some of the plurality of resonance capacitors 121, 122, 123, the switching operation of the DC / DC converter 100 is stopped, so that the abnormality can be detected promptly and other normal resonances. An overcurrent to the capacitor can also be prevented.

  Next, the operation of the DC / DC converter 120 according to the second embodiment will be described. 8 and 9 are flowcharts illustrating an example of a processing procedure of the abnormality determination method by the DC / DC converter 120 according to the second embodiment. First, FIG. 8 will be described. The process shown in FIG. 8 is a process performed in advance when the resonant capacitor 12 is normal. That is, the processing shown in FIG. 8 may be performed at the design stage or the manufacturing stage of the DC / DC converter 120, or may be performed at a predetermined timing during operation after shipment.

  The control unit 30 operates the DC / DC converter 120 to acquire a resonance current (S31). The resonance current can be acquired at a predetermined sampling period. The control unit 30 determines whether or not the acquired resonance current is zero (S32). If the resonance current is not zero (NO in S32), the process of step S31 is continued.

  When the acquired resonance current is zero (YES in S32), the control unit 30 acquires the output current (S33), acquires the input voltage (S34), and the resonance current is zero from when the switching device 10 is turned on. The conduction time, which is the time until the point in time, is specified (S35). The control unit 30 associates the specified conduction time with the acquired output current and input voltage and stores them in the storage unit 41 as the reference conduction time (S36), and ends the process.

  The process shown in FIG. 9 is a process for determining failure of the resonant capacitor 12. The control unit 30 acquires the resonance current (S41). The resonance current can be acquired at a predetermined sampling period. The control unit 30 determines whether or not the acquired resonance current is zero (S42). If the resonance current is not zero (NO in S42), the process of step S41 is continued.

  When the acquired resonance current is zero (YES in S42), the control unit 30 acquires the output current (S43), acquires the input voltage (S44), and the resonance current is zero from when the switching device 10 is turned on. The conduction time that is the time until the point of time is specified (S45). The control unit 30 determines whether or not the time difference between the specified conduction time and the reference conduction time is larger than the time threshold value (S46). In addition, when comparing conduction | electrical_connection time with reference | standard conduction | electrical_connection time, what is necessary is just to use the reference | standard conduction | electrical_connection time corresponding to the output current and input voltage equivalent to the output current and input voltage which were acquired when the conduction | electrical_connection time was specified.

  When the time difference is larger than the time threshold value (YES in S46), the control unit 30 determines that the resonance capacitor is open failure (S47), and performs the process of step S48 described later. If the time difference is not greater than the time threshold (NO in S46), the control unit 30 determines whether or not to end the process without performing the process of step S47 (S48). When it is determined that the process is not to be ended (NO in S48), the control unit 30 continues the process after step S41, and when it is determined that the process is to be ended (YES in S48), the process is ended.

(Third embodiment)
In the third embodiment, a method for determining whether or not the aforementioned predetermined condition is satisfied based on the instantaneous value of the resonance current will be described.

  FIG. 10 is an explanatory diagram showing an example of the configuration of the DC / DC converter 140 according to the third embodiment. The difference from the second embodiment is that a reference current management unit 42 is provided instead of the conduction time management unit 40. Note that the same components as those of the second embodiment are denoted by the same reference numerals, and description thereof is omitted.

  The resonance current acquisition unit 39 acquires the resonance current flowing through the resonance inductor 11 and outputs the acquired value of the resonance current to the reference current management unit 42. The current acquisition unit 31 outputs the acquired output current value to the reference current management unit 42, and the voltage acquisition unit 38 outputs the acquired input voltage value to the reference current management unit 42.

  Based on the resonance current acquired by the resonance current acquisition unit 39, the reference current management unit 42 specifies the reference current value of the resonance current when a predetermined time has elapsed since the switching device 10 was turned on. The predetermined time elapse time can be, for example, a time when the current difference between the instantaneous value of the normal resonance current and the instantaneous value of the abnormal resonance current becomes large. The details of the method for specifying the predetermined time point will be described later. The reference current value of the resonance current is a current value when the resonance capacitor 12 is normal.

  The resonance current i when the resonance capacitor 12 is normal can be expressed by Expression (14). Expression (14) can be obtained from Expression (1), Expression (2), Expression (5), and Expression (6).

  The reference current value iref of the resonance current can be expressed by Expression (15). Here, Tz is a predetermined time from when the switching device 10 is turned on.

  The reference current management unit 42 stores the specified reference current value in the storage unit 41 in association with the output current and the input voltage acquired at the time when the predetermined time has passed or in the vicinity of the time.

  The storage unit 41 stores a reference current value of the resonance current. The storage unit 41 can store a reference current value in association with the output current and the input voltage.

  The determination unit 36 determines whether the resonance capacitor 12 is abnormal based on the current difference between the resonance current acquired by the resonance current acquisition unit 39 and the reference current value stored in the storage unit 41 when a predetermined time has elapsed since the switching device 10 was turned on. The presence or absence of is determined.

  FIG. 11 is an explanatory diagram showing an example of a change in resonance current based on normality / abnormality of the resonance capacitor 12. The solid line is the resonance current when the resonance capacitor 12 is normal, and the broken line is the resonance current when the resonance capacitor 12 is abnormal. When one resonance capacitor 121, 122, 123 is abnormal (open failure), the resonance period of the resonance current changes, so the instantaneous value of the resonance current also changes. As shown in FIG. 11, when a predetermined time (indicated by reference signs Tz1 and Tz2 in the example of FIG. 11) elapses from the time when the switching device 10 is turned on, the difference between the instantaneous values of the resonance current (in the example of FIG. (Indicated by Δi) increases, and it becomes easier to determine whether or not the resonance capacitor 12 is abnormal by comparing the difference between the instantaneous values of the resonance current when the predetermined time elapses.

  As described above, when one resonance capacitor 121, 122, 123 is abnormal (open failure), the resonance period of the resonance current is shortened, so the instantaneous value of the resonance current also changes. Therefore, when the current difference between the resonance current acquired at the time when a predetermined time has elapsed from when the switching device 10 is turned on and the reference current value is larger than a predetermined current threshold, it is determined that the resonance capacitor 12 is abnormal. it can.

  When the determination unit 36 determines that the resonance capacitor 12 is abnormal, the control unit 37 stops turning on / off the switching device 10. As a result, if there is an abnormality in some of the plurality of resonance capacitors 121, 122, 123, the switching operation of the DC / DC converter 100 is stopped, so that the abnormality can be detected promptly and other normal resonances. An overcurrent to the capacitor can also be prevented.

  Next, a method for specifying a predetermined time from when the switching device 10 is turned on will be described. The resonance current i when the resonance capacitor 12 is normal can be expressed by Expression (16). Expression (16) is the same as Expression (14).

  When one resonant capacitor (capacitance is Cd) has an open failure, the combined capacitance of the resonant capacitor 12 is (C-Cd). Therefore, when one resonant capacitor (capacitance is Cd) has an open failure. The resonance current i ′ can be expressed by equation (17).

  Expression (18) can be obtained from Expression (16) and Expression (17). When the equation (18) is differentiated with respect to time t to obtain the extreme value, the equation (19) is obtained, and the equation (20) can be obtained from the equation (19). The extreme value means a case where the difference between the resonance current i when the resonance capacitor 12 is normal and the resonance current i ′ when one resonance capacitor has an open failure becomes a maximum value. T satisfying Expression (20) can be derived from Expression (21) and Expression (22). That is, Tz1 represented by the equation (21) and Tz2 represented by the equation (22) are predetermined times from when the switching device 10 is turned on. The predetermined time is a timing at which the difference between the resonance current i when the resonance capacitor 12 is normal and the resonance current i ′ when one resonance capacitor has an open failure becomes maximum. Note that Tz1 and Tz2 have timings as shown in FIG.

  The time point at which the predetermined time has elapsed since the switching device 10 was turned on is not limited to the above-described Tz1 and Tz2. For example, the predetermined time point can be set as a required time point within the ZCS establishment range.

  Next, the operation of the DC / DC converter 140 according to the third embodiment will be described. 12 and 13 are flowcharts illustrating an example of a processing procedure of the abnormality determination method by the DC / DC converter 140 according to the third embodiment. First, FIG. 12 will be described. The process shown in FIG. 12 is a process performed in advance when the resonant capacitor 12 is normal. That is, the process shown in FIG. 12 may be performed at the design stage or the manufacturing stage of the DC / DC converter 140, or may be performed at a predetermined timing during the operation after shipment.

  The control unit 30 acquires the resonance current when a predetermined time has elapsed from when the switching device 10 is turned on (S51), acquires the output current (S52), and acquires the input voltage (S53). The control unit 30 stores the acquired resonance current in the storage unit 41 as a reference current value in association with the acquired output current and input voltage (S54), and ends the process.

  The process shown in FIG. 13 is a process for determining failure of the resonant capacitor 12. The control unit 30 acquires the resonance current when a predetermined time has elapsed from when the switching device 10 is turned on (S61), acquires the output current (S62), and acquires the input voltage (S63). The control unit 30 determines whether or not the current difference between the acquired resonance current and the reference current value is larger than the current threshold (S64). When comparing the resonance current and the reference current value, a reference current value corresponding to the output current and input voltage equivalent to the output current and input voltage acquired when the resonance current is acquired may be used.

  When the current difference is larger than the current threshold (YES in S64), the control unit 30 determines that the resonance capacitor is open (S65), and performs the process of step S66 described later. When the current difference is not larger than the current threshold (NO in S64), the control unit 30 determines whether or not to end the process without performing the process of step S65 (S66). When it is determined that the process is not to be ended (NO in S66), the control unit 30 continues the process after Step S61, and when it is determined that the process is to be ended (YES in S66), the process is ended.

  Next, an error in obtaining the resonance current will be described. The error is, for example, a detection error in the resonance current detection unit 25. When a shunt resistor is used as the resonance current detection unit 25, the error is a detection error due to variation in the resistance value of the shunt resistor.

  When the resonant capacitor 12 is normal, the time from when the switching device 10 is turned on to the time when the resonant current becomes zero is T0, and when the switching device 10 is turned on, the resonant current is changed from zero to negative and becomes zero again. Assuming that the time up to a certain point (equal to the resonance period of the resonance current) is Tn, the instantaneous value of the resonance current is 0 or negative between time T0 and time Tn.

  On the other hand, when one of the resonance capacitors 121, 122, 123 fails, the combined capacitance of the resonance capacitor 12 is reduced and the resonance period of the resonance current is shortened. Therefore, when the time Tn has elapsed since the switching device 10 was turned on. There are cases where the instantaneous value of the resonance current at is positive. Therefore, the time Tz at which the predetermined time elapses is the time Tz when the predetermined time elapses when the resonance capacitor 12 is normal, and the instantaneous value of the resonance current at the time Tz when the resonance capacitor 12 is normal is ≦ 0. The instantaneous value of the resonance current can be set to be> 0.

  FIG. 14 is an explanatory diagram showing an example of the waveform of the resonance current when the resonance capacitor 12 is normal. When a resonance current error is Ie, a predetermined time point is Tz, an inductance of the resonance inductor 11 is L, an amplitude of an alternating current component of the resonance current is Ir, and an output current is I, a plurality of parallel connections are made. The combined capacitance C of the resonant capacitor 12 satisfies Expression (23).

  In Expression (23), I + Ir · sin {Tz / √ (L · C)} represents an instantaneous value of the resonance current at a predetermined time Tz when the resonance capacitor 12 is normal. In an ideal case where there is no error in the resonance current, if the equation 0 ≧ I + Ir · sin {Tz / √ (L · C)} is satisfied, the resonance capacitor 12 is normal based on the instantaneous value of the resonance current. Can be determined. Therefore, if Expression (23) is satisfied, it can be determined that the resonant capacitor 12 is normal based on the instantaneous value of the resonance current, even if the resonance current error Ie exists, as shown in FIG. .

FIG. 15 is an explanatory diagram showing an example of the waveform of the resonance current when the resonance capacitor 12 is abnormal. The combined capacitance C of the plurality of resonant capacitors 12 connected in parallel and the capacitance Cd of one resonant capacitor 121, 122, 123 satisfy Expression (24).

  (C-Cd) is a combined capacitance of the resonant capacitor 12 when one of the plurality of resonant capacitors 121, 122, 123 has an open failure. That is, in the equation (24), I + Ir · sin {Tz / √ [L · (C−Cd)]} is an instantaneous value of the resonance current at a predetermined time Tz when one resonance capacitor has an open failure. Represent. In an ideal case where there is no error in the resonance current, if the equation 0 <I + Ir · sin {Tz / √ [L · (C−Cd)]} is satisfied, the resonance capacitor 12 is based on the instantaneous value of the resonance current. Can be determined to be abnormal. Therefore, if the equation (24) is satisfied, it can be determined that the resonance capacitor 12 is abnormal based on the instantaneous value of the resonance current, even if the resonance current error Ie exists, as shown in FIG. .

  In the abnormality determination method for the DC / DC converter according to the present embodiment, the control unit 30 is constituted by, for example, a CPU (processor), a RAM (memory), and the like, and FIG. 5, FIG. 8, FIG. As shown in FIG. 13, a computer program that defines the procedure of each process is loaded into a RAM (memory), and the computer program is executed by a CPU (processor). Can be realized.

  The embodiments and examples disclosed above should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above embodiments and examples but by the scope of claims, and is intended to include all modifications and variations within the meaning and scope equivalent to the scope of claims. .

DESCRIPTION OF SYMBOLS 10 Switching device 11 Resonance inductor 12, 121, 122, 123 Resonance capacitor 13 Diode 14 Inductor 15 Capacitor 21 Current detection part 22, 23 Temperature sensor 24 Voltage acquisition part 25 Resonance current detection part 30 Control unit 31 Current acquisition part 32 Reference temperature acquisition Unit 33 device temperature acquisition unit 34 temperature identification unit 35, 41 storage unit 36 determination unit 37 control unit 38 voltage acquisition unit 39 resonance current acquisition unit 40 conduction time management unit 42 reference current management unit

Claims (9)

A switching device for turning on / off the current flowing from the input side to the output side;
A resonant inductor connected in series with the switching device;
A plurality of parallel connected resonant capacitors that together with the resonant inductor constitute a resonant circuit;
A controller for controlling on / off of the switching device;
A DC / DC converter comprising: a determination unit that determines whether or not there is an abnormality in some of the plurality of parallel-connected resonance capacitors based on whether or not a predetermined condition is satisfied. A device temperature acquisition unit for acquiring the temperature of the switching device;
A reference temperature acquisition unit for acquiring a reference temperature of a predetermined location;
A current acquisition unit for acquiring an output current;
A storage unit that stores specific information that pre-identifies the relationship between the temperature of the switching device, the reference temperature, and the output current;
A temperature specifying unit that specifies the temperature of the switching device based on the reference temperature acquired by the reference temperature acquisition unit, the output current acquired by the current acquisition unit, and the specific information;
The determination unit
2. The DC / DC converter according to claim 1, wherein presence / absence of abnormality of the resonance capacitor is determined based on a temperature difference between a temperature acquired by the device temperature acquisition unit and a temperature specified by the temperature specifying unit. A resonance current acquisition unit for acquiring a resonance current flowing through the switching device and the resonance inductor;
A storage unit that stores in advance a reference conduction time from when the switching device is turned on to when the resonance current becomes zero, and
The determination unit
The presence or absence of abnormality of the resonance capacitor is determined based on a time difference between a conduction time from a time when the switching device is turned on to a time when a resonance current acquired by the resonance current acquisition unit becomes zero and a reference conduction time. The DC / DC converter according to claim 1 or 2. A resonance current acquisition unit for acquiring a resonance current flowing through the switching device and the resonance inductor;
A storage unit that stores in advance a reference current value of a resonance current at a predetermined time from the time when the switching device is turned on, and
The determination unit
The presence or absence of abnormality of the resonance capacitor is determined based on a current difference between a resonance current acquired by the resonance current acquisition unit and the reference current value after the predetermined time has elapsed since the switching device was turned on. The DC / DC converter according to claim 2. When the error of the resonance current is Ie, the elapsed time is Tz, the inductance of the resonance inductor is L, the amplitude of the AC component of the resonance current is Ir, and the output current is I, the plurality of parallel currents The combined capacitance C of the connected resonance capacitors and the capacitance Cd of one resonance capacitor are:
Ie <I + Ir · sin {Tz / √ [L · (C−Cd)]}
The DC / DC converter according to claim 4 satisfying the expression: The combined capacitance C is
−Ie ≧ I + Ir · sin {Tz / √ (L · C)}
The DC / DC converter according to claim 5 satisfying the expression: The controller is
The DC / DC converter according to any one of claims 1 to 6, wherein when the determination unit determines that the resonance capacitor is abnormal, the switching device is turned on / off. A switching device for turning on / off a current flowing from an input side to an output side in a computer, a resonant inductor connected in series to the switching device, and a plurality of parallel-connected resonant capacitors that constitute a resonant circuit together with the resonant inductor And a computer program for determining an abnormality of a DC / DC converter comprising a control unit that controls on / off of the switching device,
Computer
A computer program that functions as a determination unit that determines whether there is an abnormality in some of the plurality of resonant capacitors connected in parallel based on whether or not a predetermined condition is satisfied. A switching device for turning on / off a current flowing from the input side to the output side, a resonant inductor connected in series to the switching device, a plurality of parallel-connected resonant capacitors that constitute a resonant circuit together with the resonant inductor, An abnormality determination method for a DC / DC converter comprising a control unit that controls on / off of a switching device,
An abnormality determination method in which a determination unit determines whether there is an abnormality in some of the plurality of parallel-connected resonance capacitors based on whether or not a predetermined condition is satisfied.

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