JP2011188713A - Discharge control unit of power conversion system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem, wherein there is no guarantee that discharge control in a fault for discharging a capacitor 16 by turning on both of a switching element Swp at a high-potential side and a switching element Swn at a low-potential side in an inverter IV, to short-circuit both the electrodes of the capacitor 16 operates, when a fault actually occurs. <P>SOLUTION: A charge unit 60 for diagnoses charges the capacitor 16 up to a diagnosis voltage. After that, by output of a discharge command dis in a fault, the switching element Swp at the high-potential side and the switching element Swn at the low-potential side are turned on, thus short-circuiting both the electrodes of the capacitor 16 and performing discharge control in a fault for discharging the capacitor 16. In this case, it is determined whether current flows in the switching element Swn, on the basis of a minute current outputted from a sense terminal St. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a power conversion circuit for converting the power of a DC power supply to a predetermined value, a capacitor interposed between the power conversion circuit and the DC power supply, and an electric path between the power conversion circuit, the capacitor and the DC power supply. Discharge that is applied to a power conversion system including an opening / closing means for opening and closing the capacitor, and that controls discharge of the charging voltage of the capacitor below a specified voltage by operating the power conversion circuit in a state where the opening / closing means is opened. The present invention relates to a discharge control device for a power conversion system including a control unit.

  As this type of discharge control device, for example, as shown in Patent Document 1 below, the switching element on the high potential side and the switching element on the low potential side of the inverter are simultaneously turned on, so that the input terminal of the inverter There has also been proposed one in which both electrodes of a connected capacitor are short-circuited to discharge the capacitor. In this control device, in order to avoid an excessive increase in current flowing when both electrodes of the capacitor are short-circuited, the voltage at the gate of the IGBT, which is a switching element, is reduced at the time of discharge control compared to the normal time. Yes.

JP 2009-232620 A

  By the way, when the switching element is operated in a mode different from the normal time at the time of discharge control as described above, the function of performing the discharge control is not used at the normal time. For this reason, being able to drive the inverter during normal time does not mean that the discharge control can be performed normally. For this reason, when a request to perform discharge control occurs, there is a possibility that the discharge control cannot actually be performed.

  It should be noted that not only the high-potential side switching element and the low-potential side switching element are turned on at the same time, but generally those that perform discharge control, discharge control is required when a request to perform discharge control occurs. These facts that are not necessarily guaranteed whether or not can actually be carried out are generally common.

  The present invention has been made to solve the above-described problems, and its object is to operate a power conversion circuit to prevent abnormalities in discharge control by a discharge control means that controls discharge of a capacitor to a specified voltage or less. An object of the present invention is to provide a discharge control device for a power conversion system that can appropriately diagnose the presence or absence.

  Hereinafter, means for solving the above-described problems and the operation and effect thereof will be described.

  According to a first aspect of the present invention, there is provided a power conversion circuit that converts power of a DC power source into a predetermined value, a capacitor interposed between the power conversion circuit and the DC power source, the power conversion circuit, the capacitor, and the DC power source. Applied to a power conversion system including an opening / closing means for opening and closing an electrical path between the capacitors, and operating the power conversion circuit under a condition in which the opening / closing means is in an open state, the charging voltage of the capacitor is reduced to a specified voltage or less. In a discharge control device of a power conversion system including a discharge control means for controlling discharge, the charge voltage of the capacitor is for diagnosis lower than a normal voltage that is a charge voltage when the power conversion circuit is operated for an original purpose. On the condition that the voltage is a voltage, the discharge control is executed to confirm whether the capacitor is actually discharged or not. Characterized in that it comprises an abnormality diagnosing means for diagnosing the presence or absence of control abnormality.

  In the above invention, the discharge control is performed to diagnose the presence or absence of abnormality in the discharge control on the condition that the voltage is a diagnostic voltage, so that the amount of heat energy generated during the diagnosis can be reduced. Moreover, since the time required for discharge control can be shortened, the time required for diagnosis can also be shortened. Furthermore, when there is an abnormality in the discharge control, it is possible to avoid maintaining a high charge voltage of the capacitor by limiting the voltage of the capacitor to the diagnostic voltage.

  The invention according to claim 2 further comprises determination means for determining whether or not an abnormality has occurred in a member on which the power conversion system is mounted, according to the invention according to claim 1, wherein the power conversion circuit has a high potential side. A switching element on the low-potential side and a series connection body connected in parallel to the capacitor, wherein the discharge control means determines that an abnormality has occurred by the determination means. An abnormal discharge control means for performing a process of short-circuiting both electrodes of the capacitor by turning on both the high-potential side switching element and the low-potential side switching element, and the opening / closing means is in an open state And discharging the capacitor without performing the short-circuiting process when it is not determined that the abnormality has occurred. And further comprising a stage.

  Since the above abnormal discharge control means is not used in normal time, how to guarantee before the occurrence of abnormality whether the abnormal discharge control means actually operates when the determination means determines that an abnormality has occurred. It becomes a problem. In this regard, in the above-described invention, by setting the diagnosis target of the abnormality diagnosis unit to the abnormality discharge control unit, it is possible to guarantee the operation of the abnormality discharge control unit when a diagnosis of normality is made.

  The invention according to claim 3 is the invention according to claim 2, wherein the high-potential side switching element and the low-potential side switching element are voltage-controlled switching elements, and the abnormal-time discharge control means includes: At least one switching element such that a current in a non-saturation region of at least one of the high-potential side switching element and the low-potential side switching element is smaller than that when the power conversion circuit is used for an original purpose. The voltage applied to the conduction control terminal is set.

  In the above invention, since the voltage applied to the conduction control terminal is different between the time of discharge control by the abnormal time discharge control means and the time when the power conversion circuit is used for the original purpose, at least the driving means of the switching element is the discharge control. It differs depending on the time of use and the original purpose. For this reason, it is particularly significant to diagnose the means peculiar to the discharge control.

  According to a fourth aspect of the present invention, in the invention of the second or third aspect, when the power conversion circuit is used for an original purpose, any one of the high-potential side switching element and the low-potential side switching element. When one is in an on state, one of the other is always in an off state.

  In the above invention, both the high-potential side switching element and the low-potential side switching element are not turned on at the time of use for the original purpose. And when used for its original purpose. For this reason, it is particularly significant to diagnose the means peculiar to the discharge control.

  According to a fifth aspect of the present invention, in the invention according to any one of the second to fourth aspects, the power conversion circuit converts the power of the DC power source into an alternating current and outputs the alternating current to a rotating machine. The original purpose of the power conversion circuit is to mediate transfer of electric power between the rotating machine and the DC power source in order to operate the rotating machine.

  The invention according to claim 6 is the invention according to any one of claims 1 to 5, wherein the diagnostic voltage is set to 60 V or less.

  The invention according to claim 7 is the invention according to any one of claims 1 to 6, further comprising charging means for charging the capacitor in a situation where the opening / closing means is in an open state. To do.

  In the said invention, it becomes possible to control the charging voltage of a capacitor to the voltage for a diagnosis by providing a charging means.

  The invention according to claim 8 is the invention according to claim 7, further comprising a pre-diagnosis processing means for controlling the voltage of the capacitor to a diagnostic voltage by operating the charging means.

  The invention according to claim 9 is the invention according to claim 8, wherein the power conversion circuit constitutes an in-vehicle high voltage system that is insulated from the in-vehicle low voltage system, and the charging means is connected to the capacitor in a secondary manner. The transformer further includes a transformer to which a side coil is connected, and the diagnostic pre-processing means charges the capacitor to the diagnostic voltage by energization control on the primary side of the transformer.

  The invention according to claim 10 is the invention according to claim 7, wherein the power conversion circuit constitutes an in-vehicle high-voltage system insulated from the in-vehicle low-voltage system, and the potential on the negative electrode side of the capacitor Potential setting means for setting the electric power of the power supply means in the in-vehicle low voltage system to the positive electrode side of the capacitor via the rectification means and the resistor. It is what outputs.

  In the above-described invention, the potential difference on the positive electrode side with respect to the negative electrode side of the capacitor can be charged to a level corresponding to the terminal voltage of the power feeding means.

  The invention according to claim 11 is the invention according to any one of claims 1 to 10, wherein the power conversion system is mounted on a vehicle, and the vehicle is predicted to start in the near future. Predicting means is further provided, wherein the diagnosing means performs the diagnosis when it is predicted that the start is predicted by the start predicting means.

  In the above invention, since diagnosis can be performed prior to starting, it is possible to surely perform this when there is an abnormality during the traveling of the vehicle and it is necessary to perform discharge control by the abnormal-time discharge control means. It becomes possible.

  A twelfth aspect of the invention is the invention according to any one of the first to eleventh aspects, wherein the diagnosing means includes means for detecting a charging voltage of the capacitor, and a decrease in the detected charging voltage is detected. The presence or absence of the abnormality is diagnosed based on the presence or absence.

  The invention according to claim 13 is the invention according to any one of claims 1 to 11, wherein the diagnosis means is based on the presence or absence of a current flowing through the discharge path of the capacitor during discharge control by the discharge control means. The presence or absence of the abnormality is diagnosed.

  It is considered that the current flowing through the discharge path of the capacitor is not significantly different between the original use of the power conversion circuit and the discharge control. For this reason, in the said invention, even if the means which detects the electric current of a discharge path at the time of use for the original purpose of a power converter circuit is diverted, the presence or absence of an electric current can be determined with high precision.

  The invention according to claim 14 is the invention according to claim 13, wherein the power conversion circuit is a series connection body of a switching element on a high potential side and a switching element on a low potential side, and is connected in parallel to the capacitor. The discharge control means includes means for short-circuiting both electrodes of the capacitor by turning on both the high-potential side switching element and the low-potential side switching element. And at least one of the high-potential side switching element and the low-potential side switching element includes a sense terminal that outputs a minute current having a correlation with a current flowing between the input terminal and the output terminal. The means indirectly grasps the current of the discharge path from the detected value of the minute current of the sense terminal. That.

  The invention according to claim 15 is the invention according to claim 13, wherein the power conversion circuit includes a boost converter that boosts the voltage of the DC power supply, and a DC / AC conversion circuit connected to the boost converter, The boost converter includes: a first capacitor as the capacitor; a high-potential side switching element and a low-potential side switching element connected in parallel to the first capacitor; a connection point between the pair of switching elements; And a second capacitor connected in parallel to the DC power supply, wherein the DC / AC converter circuit includes a high potential side switching element and a low potential side switching connected in parallel to the first capacitor. The discharge control means includes the switching element on the high potential side of the DC / AC converter circuit and the Means for short-circuiting both electrodes of the first capacitor by turning on both of the potential-side switching elements, and the high-potential-side switching element of the boost converter is connected in reverse parallel thereto The free wheel diode is provided on the same semiconductor substrate, and the semiconductor device including the switching element and the free wheel diode provided on the same semiconductor substrate has a small current correlated with a forward current flowing through the free wheel diode. , And the diagnostic means indirectly grasps the current of the discharge path from the detected value of the minute current of the sense terminal.

  The invention according to claim 16 is the invention according to any one of claims 1 to 11, wherein the power conversion circuit is a series connection body of a switching element on a high potential side and a switching element on a low potential side. And the discharge control means sets both electrodes of the capacitor by turning on both the high-potential side switching element and the low-potential side switching element. A means for performing a short-circuiting process, wherein the diagnosis means determines whether the abnormality has occurred based on the presence or absence of heat generation in at least one of the high-potential side switching element and the low-potential side switching element during discharge control by the discharge control means. The presence or absence is diagnosed.

1 is a system configuration diagram according to a first embodiment. FIG. A circuit diagram showing composition of drive unit DU concerning the embodiment. The time chart which shows the discharge control at the time of abnormality concerning the embodiment. The time chart which shows the application method of the gate voltage at the time of abnormality concerning the embodiment. The flowchart which shows the process sequence of the normal time discharge control concerning the embodiment. The flowchart which shows the process sequence of the discharge control at the time of abnormality concerning the embodiment. The circuit diagram which shows the circuit structure which performs the diagnosis of the discharge control function at the time of abnormality concerning the embodiment. The flowchart which shows the procedure of the diagnostic process of the discharge control function at the time of abnormality concerning the embodiment. The circuit diagram which shows the circuit structure which diagnoses the discharge control function at the time of abnormality concerning 2nd Embodiment. The system block diagram concerning 3rd Embodiment. The circuit diagram which shows the circuit structure which diagnoses the discharge control function at the time of abnormality concerning 4th Embodiment. The circuit diagram which shows the circuit structure which diagnoses the discharge control function at the time of abnormality concerning 5th Embodiment. The figure which shows the semiconductor device concerning the embodiment. The circuit diagram which shows the structure of the charging means concerning the modification of each said embodiment. The circuit diagram which shows the structure of the charging means concerning the modification of each said embodiment. The system block diagram concerning the modification of each said embodiment.

(First embodiment)
Hereinafter, a first embodiment in which a discharge control device of a power conversion system according to the present invention is applied to a hybrid vehicle will be described with reference to the drawings.

  FIG. 1 shows the system configuration of this embodiment. The illustrated motor generator 10 is an in-vehicle main machine and is mechanically coupled to drive wheels. Motor generator 10 is connected to high-voltage battery 12 via inverter IV and a parallel connection body of relay SMR2 and resistor 14 and relay SMR1. Here, the high voltage battery 12 has a terminal voltage of, for example, a high voltage of 100 V or higher. Further, among the input terminals of the inverter IV1, the capacitor 16 and the discharge resistor 18 are connected in parallel to the inverter IV side of the relays SMR1 and SMR2.

  The inverter IV is configured by connecting three series connection bodies of a high-potential side switching element Swp and a low-potential side switching element Swn as power elements in parallel. The connection points of the high-potential side switching element Swp and the low-potential side switching element Swn are connected to the respective phases of the motor generator 10.

  Between the input / output terminals (between the collector and the emitter) of the switching element Swp on the high potential side and the switching element Swn on the low potential side, the free wheel diode FDp on the high potential side and the free wheel diode FDn on the low potential side are connected. The cathode and anode are connected. The switching elements Swp and Swn are both formed of insulated gate bipolar transistors (IGBT). The switching elements Swp and Swn include a sense terminal St that outputs a minute current having a correlation with a current flowing between the input terminal and the output terminal.

  The minute current output from the sense terminal St flows through the shunt resistor 19, and the voltage drop due to this flows into the drive unit DU for driving the switching element Sw # (# = p, n). The drive unit DU forcibly turns off the switching element Sw # when it is determined that the current flowing between the input terminal and the output terminal of the switching element Sw # is equal to or greater than the threshold current Ith based on the voltage drop amount in the shunt resistor 19. It has a function to make a state.

  On the other hand, the control device 30 is an electronic control device that uses the low-voltage battery 20 as a power source. Specifically, the control device 30 converts the voltage of the low-voltage battery 20 into a predetermined voltage, or the power circuit 32 as a direct power source. And a central processing unit (CPU 34). The control device 30 operates the inverter IV in order to control the control amount of the motor generator 10 as a control target. Specifically, the control device 30 operates based on detection values of various sensors (not shown) and the like, operation signals gup, gvp, gwp for operating the switching elements Swp for the U phase, the V phase, and the W phase of the inverter IV, Operation signals gun, gvn, and gwn for operating the switching element Swn are generated and output. Thereby, the switching elements Swp and Swn are operated by the control device 30 via the drive unit DU connected to their conduction control terminals (gates). Further, the control device 30 detects a vehicle collision based on the detection value of the acceleration detection means (G sensor 22) that detects acceleration based on the force acting on the device, and forcibly forces the capacitor 16 when a collision is detected. In order to perform the discharge process automatically, the abnormal-time discharge command dis is output to the U-phase switching elements Swp and Swn.

  Incidentally, the high voltage system including the inverter IV and the low voltage system including the control device 30 are insulated by an insulating means such as a photocoupler (not shown), and the operation signal g * # (* = u, v, w , # = P, n) and the abnormal-time discharge command dis are output to the high voltage system via the insulating means.

  FIG. 2 shows a configuration of a drive circuit unit that turns on / off switching element Sw # among drive units DU of switching element Sw #.

  As shown in the figure, the drive unit DU includes a power supply 40 having a terminal voltage VH, and the voltage of the power supply 40 is applied to the conduction control terminal (gate) of the switching element Sw # via the charging switching element 42 and the gate resistor 44. The The gate of the switching element Sw # is connected to the output terminal (emitter) of the switching element via the gate resistor 44 and the discharge switching element 46, and this becomes a gate discharge path. The charging switching element 42 and the discharging switching element 46 are turned on / off by the normal-time drive control unit 48 according to the operation signal g * #. As a result, the switching element Sw # is turned on / off by the normal-time drive control unit 48. Incidentally, the operation signal g * p (* = u, v, w) and the operation signal g * n are complementary signals that are alternately turned on.

  Here, the drive unit DU of the U-phase upper arm further includes a circuit surrounded by a broken line in the drawing. As a result, the voltage of the power supply 50 having the terminal voltage VL lower than the terminal voltage VH is applied to the gate of the switching element Swp via the charging switching element 52 and the gate resistor 44. The gate is connected to the emitter of the switching element Swp via the gate resistor 44 and the discharge switching element 54. Then, the charging switching element 52 and the discharging switching element 54 are turned on / off by the abnormal-time drive control unit 56 according to the abnormal-time discharge command dis. Accordingly, the switching element Swp is turned on / off according to the abnormal-time discharge command dis.

  Note that the drive unit DU of the U-phase lower arm also has a function of turning on / off the switching element Swn in accordance with the abnormal-time discharge command dis. However, the voltage applied to the gate at this time is set equal to the terminal voltage VH of the power supply 40. This can be realized, for example, by mounting a power source having a terminal voltage VH instead of the power source 50. Further, for example, it can be realized by providing an OR circuit so that a logical sum signal of the operation signal gun and the abnormal-time discharge command dis can be input to the normal-time drive control unit 48. Furthermore, the propagation path of the abnormal-time discharge command dis for the lower arm of the U phase may be the same as the propagation path of the operation signal gun.

  FIG. 3 shows an aspect of discharge control based on the abnormal-time discharge command dis. Specifically, FIG. 3A shows the transition of the state of the switching element Swp on the U-phase high potential side, and FIG. 3B shows the transition of the state of the switching element Swn on the low potential side of the U-phase. FIG. 3C shows the transition of the charging voltage of the capacitor 16. As illustrated, in the present embodiment, the switching element Swn on the high potential side is periodically switched between the on state and the off state while the switching element Swn on the low potential side of the U phase is maintained in the on state. As a result, there is a period in which both the high-potential side switching element Swp and the low-potential side switching element Swn are turned on at the same time. During this period, the two electrodes of the capacitor 16 are connected via the switching elements Swp and Swn. As a result, the capacitor 16 is discharged. Incidentally, the abnormal-time discharge command dis differs between the high-potential-side switching element Swp and the low-potential-side switching element Swn, but here, the same alphabet is used for convenience.

  At this time, because of the configuration of the drive unit DU shown in FIG. 2, the gate applied voltage of the switching element Swp on the high potential side is higher than the gate applied voltage of the switching element Swn on the low potential side as shown in FIG. Lower. Here, FIG. 4A shows a transition of the abnormal discharge command dis for the U-phase high-potential side switching element Swp, and FIG. 4B shows the relationship between the gate and the emitter of the high-potential side switching element Swp. The transition of the voltage Vge is shown. FIG. 4C shows the transition of the abnormal discharge command dis for the U-phase low potential side switching element Swn, and FIG. 4D shows the gate-emitter voltage of the low potential side switching element Swn. The transition of Vge is shown.

  According to such a configuration, the switching element Swp on the high potential side is driven in the non-saturation region, and the switching element Swn on the low potential side is driven in the saturation region. This is because the gate application voltage of the low-potential side switching element Swn is lower than that of the high-potential side switching element Swp, so that the high-potential side switching element Swp is less saturated than the low-potential side switching element Swn. This is because the current becomes smaller. Accordingly, the current flowing through the high-potential side switching element Swp and the low-potential side switching element Swn is limited to the non-saturation current of the high-potential side switching element Swp by the discharge control. Also, the high-potential side switching element Swp and the low-potential side can be reduced by turning on / off the high-potential side switching element Swp a plurality of times to limit the on-time of the high-potential side switching element Swp. The current flowing through the switching element Swn can be limited. Note that it is desirable that the current in the non-saturation region of the switching element Swp on the high potential side is set to be less than the threshold current Ith defined by the drive unit DU. Incidentally, the terminal voltage VH is such that the threshold current Ith is in the saturation region. That is, when controlling the control amount of motor generator 10, switching elements Swp and Swn are driven in the saturation region.

  The discharge control is performed at the time of a vehicle collision or the like. In the present embodiment, the inverter IV is operated even when the vehicle is stopped during normal times and the relay SMR1 is switched to the open state. Discharge control is performed. However, the discharge control at this time is executed by passing a reactive current to the motor generator 10. Thereby, the capacitor 16 can be discharged more rapidly than the discharge of the capacitor 16 by the discharge resistor 18. Incidentally, the discharge resistor 18 is provided for an unexpected situation such as when the motor generator 10 is in a power generation state due to traction of the vehicle or the like and the capacitor 16 is charged.

  FIG. 5 shows a procedure for normal discharge control in the present embodiment. This process is repeatedly executed by the control device 30 at a predetermined cycle, for example.

  In this series of processes, first, in step S10, it is determined whether or not the relay SMR1 is switched from the closed state to the open state by turning off the start switch of the vehicle. Here, the vehicle activation switch is a means for allowing the user to activate the vehicle. The activation switch is not necessarily required to be mechanically operated. For example, even if the activation switch is a wireless device carried by the user and is close to the vehicle, the activation permission signal can be received by the vehicle side. Good. When an affirmative determination is made in step S10, in step S12, the operation signal g * # is set so as to flow a reactive current, and is output to each switching element Sw #. Here, for example, when the motor generator 10 is IPMSM or SPM, the operation signal g * # may be set so that the q-axis current is zero and the absolute value of the d-axis current is larger than zero.

  When the process of step S12 is completed or when a negative determination is made in step S10, this series of processes is temporarily terminated.

  FIG. 6 shows a processing procedure of abnormal discharge control in the present embodiment. This process is repeatedly executed by the control device 30 at a predetermined cycle, for example.

  In this series of processes, first, in step S20, a detection value of the G sensor 22 is input. In a succeeding step S22, it is determined whether or not the vehicle has collided based on the input detection value. Here, if the detected acceleration is equal to or greater than a predetermined value, it may be determined that a collision has occurred. If it is determined that the vehicle has collided, the relays SMR1 and SMR2 are opened in step S24. Further, in step S26, an abnormal discharge command dis is output. When the process of step S26 is completed or when a negative determination is made in step S22, this series of processes is temporarily terminated.

  By the way, the abnormal discharge control is not used unless an abnormal situation such as a vehicle collision occurs. Whether or not the abnormal-time discharge control is surely performed in an abnormal state cannot be determined by whether or not the motor generator 10 can be normally controlled. This is different from the case where the abnormal-time discharge command dis is a signal different from the operation signals gup and gun, and the case where the drive circuit used in the abnormal-time discharge control is used to control the control amount of the motor generator 10. It is for things.

  Therefore, in the present embodiment, as shown in FIG. 1, the diagnosis unit 70 determines whether or not the capacitor 16 is discharged by performing the abnormality discharge control after charging the capacitor 16 with the diagnosis charging unit 60. To do. Thereby, it can be diagnosed whether discharge control at the time of abnormality can be performed reliably.

  FIG. 7 shows specific configurations of the diagnostic charging unit 60 and the diagnostic unit 70.

  As shown in the figure, the diagnostic charging unit 60 includes a flyback converter and charges the capacitor 16 with the electric power of the low voltage battery 20. Specifically, the primary coil of the transformer 62 and the low voltage battery 20 are connected via an energy storage switch 64. The energy stored in the primary coil when the energy storage switch 64 is turned on is charged to the capacitor 16 via the secondary coil and the diode 66 when the energy storage switch 64 is turned off. The

  On the other hand, the diagnosis unit 70 determines whether or not the capacitor 16 is discharged by detecting the current flowing through the switching element Swn based on the voltage drop amount of the shunt resistor 19. Specifically, a comparator 72 that determines whether or not the potential difference between both ends of the shunt resistor 19 is equal to or higher than the voltage of the power supply 73, and an AND circuit 74 that generates a logical product signal of the discharge period signal DT from the CPU 34. The CPU 34 determines whether the capacitor 16 is discharged based on the logical product signal. The discharge period signal DT is a signal indicating the output period of the abnormal-time discharge command dis. Here, the discharge period signal DT is input to the AND circuit 74 via the buffer 79 and the insulating unit 76, and the output of the AND circuit 74 is input to the CPU 34 via the insulating unit 78. Here, the insulation parts 76 and 78 are means for transmitting signals while maintaining insulation between the high voltage system and the low voltage system, such as a photocoupler.

  FIG. 8 shows a procedure of abnormality diagnosis processing according to the present embodiment. This process is repeatedly executed by the control device 30 at a predetermined cycle, for example.

  In this series of processing, first, in step S30, it is determined whether or not the start switch is turned on. This process is for predicting whether the vehicle will start in the near future. That is, when the start switch is turned on, the vehicle is predicted to start in the near future. The start switch has been described in step S10 of FIG. When an affirmative determination is made in step S30, in step S32, the voltage of the capacitor 16 is charged to a diagnostic voltage Vdg lower than the terminal voltage of the high-voltage battery 12 by repeatedly turning on and off the energy storage switch 64. . Here, the diagnostic voltage Vdg is set to “60 V” or less. This is a setting for limiting the charging voltage of the capacitor 16 to a voltage that is assumed not to cause danger to the human body.

  In the subsequent step S34, an abnormal discharge command dis is output. In step S36, it is determined whether or not the abnormal discharge control is normal based on whether or not the capacitor 16 is discharged. When a positive determination is made in step S36, the capacitor 16 is charged by closing the relays SMR1 and SMR2 in step S38, and preparation for control of the control amount of the motor generator 10 is made. Specifically, first, the relay SMR2 is closed while the relay SMR1 is opened, and then the capacitor 16 is charged through a high resistance electric path including the resistor 14, and then the relay SMR2 is opened and the relay SMR1 is closed. By setting the state, the high voltage battery 12 and the capacitor 16 are connected by a low resistance electric path. On the other hand, when a negative determination is made in step S36, a process of notifying the user of the fact is performed by notifying the outside of the fact in step S40. In addition, when the process of step S38, S40 is completed, or when negative determination is made in step S30, this series of processes is once complete | finished.

  According to the embodiment described in detail above, the following effects can be obtained.

  (1) The diagnostic voltage Vdg was set to “60 V” or less. Thereby, the amount of thermal energy generated during diagnosis can be reduced. Moreover, since the time required for discharge control can be shortened, the time required for diagnosis can also be shortened.

  (2) When no abnormality occurred, discharge control during abnormality was performed to diagnose the presence or absence of the abnormality. As a result, when a diagnosis of normality is made, it is possible to guarantee the operation of the abnormal-time discharge control when an abnormality actually occurs.

  (3) The high-potential-side switching element Swp is set so that the current in the non-saturated region of the high-potential-side switching element Swp is smaller during abnormal discharge control than when the control amount of the motor generator 10 is controlled. The voltage applied to the gate (terminal voltage VL) was set. As a result, the means for driving the switching element Swp is different between the control amount control and the abnormal discharge control, so that it is particularly significant to diagnose the means specific to the abnormal discharge control.

  (4) At the time of abnormal discharge control, a high voltage (terminal voltage VH) is applied to the gate of the switching element Swn on the low potential side and kept on, and the gate of the switching element Swp on the high potential side is low. Discharge control during abnormalities was performed by intermittently applying a voltage (terminal voltage VL) and repeating the on / off operation. Thereby, abnormal discharge control can be suitably performed, for example, the potential between the gate and the emitter on the side where the on / off operation is repeated can be stabilized.

  (5) The voltage of the capacitor 16 is charged to the diagnostic voltage Vdg by the diagnostic charging unit 60. Thereby, a diagnosis can be performed appropriately.

  (6) A diagnosis was made when the vehicle was predicted to start in the near future. As a result, diagnosis can be performed prior to start of the vehicle, so that it is possible to reliably perform an abnormality when the vehicle is running and it is necessary to perform discharge control during an abnormality.

  (7) Based on whether or not current flows through the discharge path of the capacitor 16, diagnosis of discharge control during abnormality was performed. Since the current in the discharge path is not significantly different between the normal time and the discharge control, it is possible to determine with high accuracy whether or not the current flows during the abnormal time discharge control by means for detecting the current in the discharge path in the normal time. .

(Second Embodiment)
Hereinafter, the second embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  FIG. 9 shows specific configurations of the diagnostic charging unit 60 and the diagnostic unit 70 according to the present embodiment. In FIG. 9, members corresponding to those shown in FIG. 7 are given the same reference numerals for convenience.

  As shown in the figure, in the present embodiment, the presence or absence of discharge of the capacitor 16 is confirmed based on the detection value of the voltage sensor 80 that detects the voltage of the capacitor 16. Here, the voltage sensor 80 includes a voltage dividing resistor and a differential amplifier circuit, and uses a high-resistance resistor as the voltage dividing resistor to insulate the high voltage system. For this reason, the insulating parts 76 and 78 shown in FIG. Since the output voltage region of the voltage sensor 80 is a region that covers the voltage range of the capacitor 16, the interval of the entire region of the output voltage is several times the diagnostic voltage Vdg or more. Therefore, in order for the comparator 72 to grasp the discharge of the capacitor 16 with high accuracy, it is desirable to increase the diagnostic voltage Vdg to some extent, for example, “30 to 60 V”.

(Third embodiment)
Hereinafter, the third embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  FIG. 10 shows a system configuration according to the present embodiment. In FIG. 10, members corresponding to those shown in FIG. 1 are given the same reference numerals for convenience.

  As illustrated, in the present embodiment, a boost converter CV is provided between the inverter IV and the high voltage battery 12. Boost converter CV includes capacitor 17, a series connection body of high-potential side switching element Swp and low-potential side switching element Swn connected in parallel, high-potential side switching element Swp and low-potential side switching element. The reactor L which connects the connection point of Swn and the capacitor | condenser 16 is provided.

  In this case, the capacitors 16 and 17 are to be discharged. Here, by discharging the capacitor 17 using the U-phase high-potential side switching element Swp and the low-potential side switching element Swn of the inverter IV, the voltage of the capacitor 16 is also discharged. This is because when the voltage of the capacitor 17 becomes lower than the voltage of the capacitor 16, a current flows from the capacitor 16 to the capacitor 17 via the reactor L and the free wheel diode FDp of the boost converter CV.

(Fourth embodiment)
Hereinafter, the fourth embodiment will be described with reference to the drawings, focusing on differences from the first embodiment.

  FIG. 11 shows specific configurations of the diagnostic charging unit 60 and the diagnostic unit 70 according to the present embodiment. In FIG. 11, members corresponding to those shown in FIG. 7 and the like are given the same reference numerals for convenience.

  In the present embodiment, whether or not the capacitors 16 and 17 are discharged is confirmed using a current sensor 82 that detects a current flowing through the reactor L. Here, the current sensor 82 includes a Hall element, and is a means capable of detecting the current while being insulated from the current path including the reactor L. For this reason, the insulating parts 76 and 78 shown in FIG.

(Fifth embodiment)
Hereinafter, the fifth embodiment will be described with reference to the drawings, centering on differences from the first embodiment.

  FIG. 12 shows specific configurations of the diagnostic charging unit 60 and the diagnostic unit 70 according to the present embodiment. In FIG. 12, members corresponding to those shown in FIG. 7 and the like are given the same reference numerals for the sake of convenience.

  In the present embodiment, whether or not the capacitors 16 and 17 are discharged is confirmed based on the minute current from the sense terminal St that outputs a minute current having a correlation with the current flowing through the free wheel diode FDp of the boost converter CV. That is, it is determined that the capacitors 16 and 17 are discharged because the amount of voltage drop in the shunt resistor 84 due to the minute current output from the sense terminal St is equal to or greater than the threshold due to the forward current flowing through the freewheeling diode FDp. To do. The forward current flowing through the freewheeling diode FDp can be detected using the sense terminal St as described above, because the switching element Sw # and the freewheeling diode FD # according to the present embodiment are as shown in FIG. This is because they are provided on the same semiconductor substrate.

  That is, as illustrated, the semiconductor substrate 100 is formed with an IGBT region and a diode region. A region extending from the main surface side to the back surface side of the semiconductor substrate 100 is an N-type region 102 whose conductivity type is N-type. Further, a P-type region 104 having a P-type conductivity is formed in the surface layer portion on the main surface side of the semiconductor substrate 100, and the N-type having a concentration higher than that of the N-type region 102 in the P-type region 104. An N type region 106 having the following conductivity type is formed. The P-type region 104 and the N-type region 106 are connected to an IGBT emitter terminal E and a diode anode terminal. A gate electrode 110 is formed on the P-type region 104 and the N-type region 106 with a gate oxide film 108 interposed therebetween.

  On the other hand, an N-type region 106 and a P-type region 104 having a concentration higher than that of the N-type region 102 are provided on the surface layer portion on the back side of the semiconductor substrate 100. Here, the P-type region 104 constitutes a collector region of the IGBT, and the N-type region 106 constitutes a cathode region of the diode. Note that an N-type region 102 having a lower concentration than the N-type region 102 is formed between the P-type region 104 and the N-type region 106 and the N-type region 102.

  FIG. 13B is a plan view schematically showing the main surface side of the semiconductor substrate 100. As shown in the drawing, most of the main surface side is an emitter region, and a gate region and a sense electrode 118 are formed as a region smaller than this. Here, the actual area of the sense electrode 118 is about one-thousandth of the area of the emitter region, so that a very small current is correlated with the current flowing through the IGBT and the free wheel diode. Can be output. FIG. 13C shows the relationship between the current flowing through the switching element Sw # or the free wheel diode FD # and the amount of voltage drop at the shunt resistor 84.

  As shown in FIG. 12, whether or not the voltage drop amount in the shunt resistor 84 is equal to or greater than the threshold value depends on the voltage drop amount in the shunt resistor 84 converted by the level shift circuit 77 and the voltage of the power source 73. Is performed by comparison by the comparator 72. Here, the level shift circuit 77 includes the comparator 72 regardless of the polarity of the voltage drop of the shunt resistor 84 between the case where the forward current flows through the free wheel diode FDp and the case where the current flows through the switching element Swp. This is a technique for fixing the polarity of the voltage applied to the non-inverting input terminal.

(Other embodiments)
Each of the above embodiments may be modified as follows.
<Start prediction means>
The start prediction means is not limited to the one that predicts that the vehicle will start when the start switch is turned on. For example, it may be predicted to start by turning on an accessory switch operated by a user to turn on the power source of the in-vehicle electronic device. Further, for example, it may be predicted that the vehicle will start when a brake operation is performed.
<About abnormality diagnosis means>
The abnormality diagnosing means is not limited to that which diagnoses when the start predicting means predicts that the vehicle will start. For example, the presence or absence of an abnormality may be diagnosed after the start switch is turned off and the relays SMR1 and SMR2 are opened. Specifically, for example, when the relays SMR1 and SMR2 are opened, the voltages of the capacitors 16 and 17 are reduced to a specified voltage via the discharge resistor 18, so that the switching element Swp on the high potential side and the low potential side What is necessary is just to diagnose the presence or absence of abnormality by performing discharge control to turn on the switching element Swn. Alternatively, for example, after the relays SMR1 and SMR2 are opened, the voltage of the capacitors 16 and 17 is lowered to a specified voltage by energizing the reactive current to the motor generator 10, and then the switching element on the high potential side. The presence or absence of abnormality may be diagnosed by performing discharge control for turning on the Swp and the switching element Swn on the low potential side.
<About diagnostic voltage>
The diagnostic voltage is not limited to a specified voltage of 60 V or less. For example, the specified voltage may be “42V” or less.
<About judgment means>
As a determination means for determining whether or not an abnormality has occurred in a member on which the power conversion system is mounted, a control device 30 that is mounted in the low voltage system and generates the operation signals gup, gun, gvp, gvn, gwp, gwn. Not limited to. For example, a dedicated unit that is mounted in the high-voltage system and that generates the abnormal-time discharge command dis may be used. However, even in this case, it is desirable that the control device 30 can also output the abnormal-time discharge command dis for diagnosis. This can be realized, for example, by setting the input signal of the drive unit DU as the logical sum of the signal of the dedicated means and the signal from the control device 30. However, even if the control device 30 does not have a function of generating the abnormal discharge command dis, diagnosis can be executed if the abnormal discharge command dis is output to the same means by operating the dedicated means. .

Further, the determination means is not limited to determining that an abnormality has occurred based on the detection value of the G sensor 22. For example, it may be based on a diagnosis result of a diagnosis means for determining whether there is an abnormality in a power conversion system including a motor generator, an inverter IV, a boost converter CV, and the like.
<About drive unit DU>
The drive unit DU for the U-phase upper arm is not limited to one provided with the charging switching element 42 and the discharging switching element 46 in the normal state, and the charging switching element 52 and the discharging switching element 54 in the abnormal state. . For example, instead of sharing them, the means for applying a voltage to the input terminal of the charging switching element may be different between the normal time and the abnormal time.
<Regarding normal discharge means>
The normal-time discharging means is not limited to the one that causes the reactive current to flow through the motor generator 10. For example, a means for discharging the capacitors 16 and 17 by the discharge resistor 18 may be used. Further, for example, a means for operating a relay by providing a discharge circuit including a relay and a resistor between a positive input terminal and a negative input terminal of the inverter IV may be used.

Further, the means for performing the abnormal discharge control in each of the above embodiments may be a normal discharge means.
<Regarding discharge control means during abnormal conditions>
As the discharge control means at the time of abnormality, both the electrodes of the capacitors 16 and 17 are switched by repeating the ON state and the OFF state of the high potential side switching element Swp a plurality of times while keeping the low potential side switching element Swn in the on state. It is not restricted to what performs the process which produces | generates a short circuit state in multiple times. For example, the short-circuited state of both electrodes of the capacitors 16 and 17 is generated a plurality of times by repeating the on-state and the off-state of the low-potential side switching device Swn a plurality of times while the high-potential side switching device Swp is kept on. It is also possible to perform the processing to be performed. However, even in this case, it is desirable to set the gate applied voltage on the side where the on state and the off state are repeated a plurality of times to be lower and operate in the non-saturated region. Further, for example, the short-circuit state of both electrodes of the capacitors 16 and 17 is generated a plurality of times by repeating the simultaneous ON state and the simultaneous OFF state of the high potential side switching element Swp and the low potential side switching element Swn a plurality of times. Processing may be performed. Here, the gate applied voltage may be adjusted so that at least one of the high-potential side switching element Swp and the low-potential side switching element Swn is operated in the non-saturation region, but both are operated in the non-saturation region. It may be. Further, both the high-potential side switching element Swp and the low-potential side switching element Swn may be turned on only once in the discharge control period.

  Further, the discharge control is not limited to using only the combination of the switching element Swp on the high potential side and the switching element Swn on the low potential side that applies a voltage to one phase of the motor generator 10. For example, the switching element Swp on the high potential side and the switching element Swn on the low potential side in all phases may be turned on simultaneously. Further, for example, the switching element Swp on the high potential side and the switching element Swn on the low potential side of each phase may be switched so as to be sequentially turned on.

  Further, the discharge control is not limited to using only the set of the switching element Swp on the high potential side and the switching element Swn on the low potential side of the inverter IV. For example, the discharge control may be performed using a set of the switching element Swp on the high potential side and the switching element Swn on the low potential side of the boost converter CV.

In addition, the high-potential side switching element Swp and the low-potential side switching element Swn are simultaneously turned on, so that the electrodes of the capacitors 16 and 17 are not short-circuited. For example, a means for causing a reactive current to flow through the motor generator 10 may be used. In this case, for example, the normal-time discharging means may be a means for discharging by the discharge resistor 18.
<About charging means>
The charging means is not limited to one provided with a flyback converter, and may be provided with a forward converter, for example. Further, the charging means is not limited to the one having a transformer. For example, as shown in FIGS. 14 (a) and 14 (b), the voltage of the low-voltage battery 20 may be charged via a rectifier (diode 86) and a resistor 88. Here, the resistor 88 has a high resistance (for example, several MΩ or more) for insulating the low voltage system from the high voltage system. In order to enable charging by such means, the reference potential of the low voltage system (the negative potential of the low voltage battery 20) is set to be higher than the reference potential of the high voltage system (the negative potential of the high voltage battery 12). It is necessary to provide a potential setting means. Here, an example is shown in which a series connection of capacitors 90 and 92 is provided to divide the potential between the positive electrode and the negative electrode of the capacitor 16 into two, and the potential at the connection point of these capacitors 90 and 92 is used as the reference potential of the low voltage system. Has been. Thereby, when relays SMR1 and SMR2 are opened, the positive electrode potential of capacitor 16 becomes equal to or lower than the positive electrode potential of low voltage battery 20, and capacitor 16 can be charged with electric power of low voltage battery 20. Incidentally, when the relays SMR1 and SMR2 are closed, the positive potential of the capacitor 16 is higher than the positive potential of the low-voltage battery 20, so that the power of the low-voltage battery 20 is charged in the capacitor 16. There is nothing. The rectifying means is not limited to the diode 86, and may be a thyristor, a transistor, or the like.

  Further, as shown in FIGS. 15A and 15B, in the configuration including the converter CV, the charging target of the charging unit may be a capacitor 17.

<About DC / AC converter circuit>
As a DC / AC converter circuit (inverter IV) in which both the high-potential side switching element and the low-potential side switching element are turned on during the discharge control, the circuit between the rotating machine as the in-vehicle main unit and the high-voltage battery 12 is used. It is not limited to mediating power transfer. For example, the transfer of electric power between the high voltage battery 12 and a rotary machine other than the main machine such as a rotary machine provided in the air conditioner may be used.
<Method to confirm whether the capacitor is actually discharged>
In the fourth embodiment, instead of the current sensor 82 using a Hall element, a current transformer may be provided to detect current. Moreover, it is good also as a means which provides a shunt resistance and detects an electric current. In the case of means for detecting current with a shunt resistor, since the shunt resistor is in the high voltage system, the comparator 72 and the like for comparing the voltage at both ends with the threshold value are in the high voltage system. Insulating portions 76 and 78 are provided between the 72 and the buffer 79 and the CPU 34.

  Further, as a method for confirming whether or not the capacitor is actually discharged, in discharging control in which both the high-potential side switching element and the low-potential side switching element are turned on, at least one of these switching elements It may be determined whether or not heat is generated. FIG. 16 shows an example in which the diagnosis unit 70 determines whether or not the temperature of the switching element Swn is increased by the temperature detection means (temperature sensitive diode SD) as the presence or absence of heat generation of the switching element Swn on the low potential side. In FIG. 16, members corresponding to those shown in FIG. 1 are given the same reference numerals for convenience.

<Other>
The high-potential side switching element Swp and the low-potential side switching element Swn used for discharge control are not limited to IGBTs, and may be field effect transistors such as power MOS field effect transistors.

  The vehicle is not limited to a hybrid vehicle, and may be, for example, an electric vehicle that includes only a rotating machine as an in-vehicle main unit.

  -As a discharge control apparatus, not only what is mounted in a vehicle, For example, you may apply to the power conversion system which converts the electric power of the direct-current power source provided in a house into alternating current. In this case, the abnormal time may be a case where, for example, an earthquake is detected.

  DESCRIPTION OF SYMBOLS 10 ... Motor generator, 12 ... High voltage battery (one embodiment of DC power supply), 16, 17 ... Capacitor, 30 ... Control device, 60 ... Diagnosis charging unit, 70 ... Diagnosis unit, Swp ... High potential side switching element , Swn... Switching element Swn on the low potential side.

Claims (16)

A power conversion circuit for converting the power of the DC power supply to a predetermined value, a capacitor interposed between the power conversion circuit and the DC power supply, and an opening / closing operation for opening and closing an electric path between the power conversion circuit and the capacitor and the DC power supply And a discharge control means for controlling the charge voltage of the capacitor to a specified voltage or less by operating the power conversion circuit in a state where the open / close means is opened. In the discharge control device of the power conversion system,
On the condition that the charging voltage of the capacitor is a diagnostic voltage lower than a normal voltage which is a charging voltage when the power conversion circuit is operated for an original purpose, the discharging control is executed and the capacitor is executed. A discharge control device for a power conversion system, comprising: an abnormality diagnosis means for diagnosing whether there is an abnormality in discharge control by the discharge control means by confirming whether or not the battery is actually discharged. A judgment means for judging whether or not an abnormality has occurred in a member on which the power conversion system is mounted;
The power conversion circuit includes a series connection body of a switching element on a high potential side and a switching element on a low potential side and connected in parallel to the capacitor,
The discharge control unit short-circuits both electrodes of the capacitor by turning on both the high-potential side switching element and the low-potential side switching element when the determination unit determines that an abnormality has occurred. An abnormal discharge control means for performing the process of
A normal-time discharging unit that discharges the capacitor without performing the short-circuiting process when the opening / closing unit is in an open state and it is not determined that the abnormality has occurred. Item 2. A discharge control device for a power conversion system according to Item 1. The high-potential side switching element and the low-potential side switching element are voltage-controlled switching elements,
In the abnormal discharge control means, the current in the non-saturation region of at least one of the high-potential side switching element and the low-potential side switching element is smaller than when the power conversion circuit is used for its original purpose. The voltage applied to the conduction control terminal of the at least one switching element is set as described above.   When the power conversion circuit is used for its original purpose, when one of the high-potential side switching element and the low-potential side switching element is in an on state, the other is always in an off state. The discharge control device for a power conversion system according to claim 2 or 3. The power conversion circuit includes a direct current alternating current conversion circuit that converts electric power of the direct current power source into alternating current and outputs the alternating current to a rotating machine,
The original purpose of the power conversion circuit is to mediate transfer of power between the rotating machine and the DC power source in order to operate the rotating machine. The discharge control apparatus of the power conversion system of any one of Claims.   The discharge control device for a power conversion system according to any one of claims 1 to 5, wherein the diagnostic voltage is set to 60 V or less.   The discharge control device for a power conversion system according to any one of claims 1 to 6, further comprising charging means for charging the capacitor in a state where the opening / closing means is in an open state.   8. The discharge control device for a power conversion system according to claim 7, further comprising pre-diagnosis processing means for controlling the voltage of the capacitor to a diagnostic voltage by operating the charging means. The power conversion circuit constitutes an in-vehicle high voltage system that is insulated from the in-vehicle low voltage system,
The charging means further includes a transformer having a secondary coil connected to a capacitor,
9. The discharge control device for a power conversion system according to claim 8, wherein the pre-diagnosis processing unit charges the capacitor with the diagnostic voltage by energization control on a primary side of the transformer. The power conversion circuit constitutes an in-vehicle high voltage system that is insulated from the in-vehicle low voltage system, and sets a potential on the negative side of the capacitor to a reference potential or less on the low voltage system side. With
8. The power conversion system according to claim 7, wherein the charging unit outputs power of a power feeding unit in the in-vehicle low voltage system to a positive side of the capacitor via a rectifying unit and a resistor. Discharge control device. The power conversion system is mounted on a vehicle,
It further comprises a start prediction means for predicting that the vehicle will start in the near future,
The discharge control device for a power conversion system according to any one of claims 1 to 10, wherein the diagnosis unit performs the diagnosis when it is predicted that the start is predicted by the start prediction unit.   The diagnostic means comprises means for detecting a charging voltage of the capacitor, and diagnoses the presence or absence of the abnormality based on the presence or absence of a decrease in the detected charging voltage. The discharge control device of the power conversion system according to the item.   12. The diagnosis according to claim 1, wherein the diagnosis unit diagnoses the presence / absence of the abnormality based on the presence / absence of a current flowing through a discharge path of the capacitor during discharge control by the discharge control unit. Discharge control device for power conversion system. The power conversion circuit includes a series connection body of a switching element on a high potential side and a switching element on a low potential side and connected in parallel to the capacitor,
The discharge control means includes means for short-circuiting both electrodes of the capacitor by turning on both the high-potential side switching element and the low-potential side switching element,
At least one of the high-potential side switching element and the low-potential side switching element includes a sense terminal that outputs a minute current having a correlation with a current flowing between the input terminal and the output terminal.
14. The discharge control device for a power conversion system according to claim 13, wherein the diagnosis means indirectly grasps the current of the discharge path from the detected value of the minute current of the sense terminal. The power conversion circuit includes a boost converter that boosts the voltage of the DC power supply, and a DC / AC conversion circuit connected to the boost converter,
The step-up converter includes a first capacitor as the capacitor, a high-potential side switching element and a low-potential side switching element connected in parallel to the first capacitor, a connection point between the pair of switching elements, and the direct current A reactor for connecting a power source, and a second capacitor connected in parallel to the DC power source,
The DC / AC conversion circuit includes a high-potential side switching element and a low-potential side switching element connected in parallel to the first capacitor,
The discharge control means performs a process of short-circuiting both electrodes of the first capacitor by turning on both the high-potential side switching element and the low-potential side switching element of the DC-AC converter circuit. With
The switching element on the high potential side of the boost converter is provided with a free wheel diode connected in reverse parallel thereto on the same semiconductor substrate,
A semiconductor device including a switching element and a freewheel diode provided on the same semiconductor substrate includes a sense terminal that outputs a minute current having a correlation with a forward current flowing through the freewheel diode,
14. The discharge control device for a power conversion system according to claim 13, wherein the diagnosis means indirectly grasps the current of the discharge path from the detected value of the minute current of the sense terminal. The power conversion circuit includes a series connection body of a switching element on a high potential side and a switching element on a low potential side and connected in parallel to the capacitor,
The discharge control means includes means for short-circuiting both electrodes of the capacitor by turning on both the high-potential side switching element and the low-potential side switching element,
The diagnosis means diagnoses the presence or absence of the abnormality based on the presence or absence of heat generation of at least one of the high potential side switching element and the low potential side switching element during discharge control by the discharge control means. The discharge control apparatus of the power conversion system of any one of Claims 1-11.

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