JP6447207B2 - Driving device for switching element - Google Patents

Description

  The present invention relates to a driving device for a switching element.

  As a power conversion circuit connected to an AC motor, a configuration is known in which a plurality of switching elements provided in an upper arm and a lower arm and forming a serial connection body are provided, and power conversion is performed by switching the switching elements. . Moreover, as a failure determination method of the switching element in such a power conversion circuit, when a short circuit occurs in the upper and lower arm switching elements, the short circuit current is detected, and when the short circuit current exceeds a predetermined threshold, it is regarded as a short circuit occurrence, A technique for performing a protective operation (shutdown) of a switching element is known.

JP 2012-253202 A

  However, when the failure determination is performed based on the short-circuit current at the time of occurrence of the short-circuit as described above, it is necessary to instantaneously perform the short-circuit determination in order to protect the switching element, which may cause a malfunction or the like. . In particular, when the semiconductor switching element is thinned to reduce the loss, the short-circuit withstand capability is reduced. Therefore, it is considered that it is required to perform the short-circuit determination and the protection operation more quickly.

  The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide a driving device for a switching element that makes it possible to achieve appropriate protection when the switching element is on.

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

  A switching element driving apparatus according to the present invention includes a plurality of switching elements (21 to 26) provided in an upper arm and a lower arm to form a series connection body, and free wheel diodes connected in antiparallel to the plurality of switching elements, respectively. (31 to 36) and is applied to a power conversion circuit (11) electrically connected to the AC motor (10) to control the current flowing in the coil of the AC motor to a predetermined current command value. The plurality of switching elements are turned on and off. And in a period in which a forward current flows through the freewheel diode on either side of the switching element of the upper and lower arms, switch control means for turning off the switching element to which the freewheel diode is reversely connected, and And determining means for determining that the switching element is on-failed based on a difference between an actual value of the current flowing through the coil and the current command value.

  When controlling on / off of a plurality of switching elements so as to control the current flowing through the coil of the AC motor to a predetermined current command value, during the period when one of the switching elements of the upper and lower arms is turned on, a current is supplied to the coil through the switching element. Then, during the period in which the switching element is turned off, a current (forward current of the free wheel diode) flows to the coil through the free wheel diode of the opposite arm. In this case, when the switching element is intermittently turned on / off, current increases and decreases, and accordingly, the current flowing through the coil is controlled to the command value.

  Here, for example, when a positive output current flows through the coil due to on / off of the upper arm switching element, a case where an on failure occurs while the upper arm switching element is on is considered. In such a case, according to the above configuration, the switching element (here, the lower arm switching element) to which the free wheel diode is reversely connected is turned off during the period in which the forward current flows through the free wheel diode due to the upper arm switching element being turned off. It is in a state. Therefore, even if the upper arm switching element is on-failed, the occurrence of a short circuit between the upper and lower arms is suppressed. In addition, when the upper arm switching element is in the on-failure state, the output current does not decrease when the upper arm switching element is off, which is different from the normal state. Therefore, there is a divergence between the actual current value and the current command value. Based on the above, it can be determined that an ON failure of the switching element has occurred. At this time, it is possible to determine the occurrence of an on-failure of the switching element before the upper and lower arms are short-circuited, and it is possible to realize proper protection when the switching element is on-failure.

The system block diagram in embodiment. (A) is a figure which shows the structure of the upper-lower arm of W phase, (b) is a figure for demonstrating operation | movement of the upper-lower arm of W phase. (A) is a figure which shows the structure of the upper-lower arm of W phase, (b) is a figure for demonstrating operation | movement of the upper-lower arm of W phase. The figure which shows the relationship between the forward direction current If of a freewheel diode, and the voltage drop amount Vf. The figure for demonstrating the magnitude | size of an electric current vector, and the deviation of a phase angle. The figure which shows the difference in the current waveform with the case where a short circuit current flows, and the case where it does not flow. The figure for demonstrating the deviation of a detected current value. The time chart which shows the result of the simulation experiment regarding on failure determination. The figure for demonstrating the deviation of a detected current value.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings. This embodiment demonstrates embodiment applied to the vehicle (for example, a hybrid vehicle and an electric vehicle) provided with a rotary machine as a vehicle-mounted main machine.

  In FIG. 1, MG10 (motor generator) is a three-phase AC motor (multi-phase rotating machine) as an in-vehicle main machine, and is connected to driving wheels (not shown). Specifically, the MG 10 includes a permanent magnet synchronization including a stator having a U-phase coil 10u, a V-phase coil 10v, and a W-phase coil 10w, and a rotor (not shown) that has a permanent magnet and is mechanically coupled to a drive wheel. A motor (for example, SPMSM or IPMSM). The coils 10u, 10v, and 10w are Y-connected by connecting one end of each of the coils at a neutral point.

  The MG 10 is connected to a high voltage battery 12 serving as a DC power source via an inverter 11 serving as a power conversion circuit. The output voltage of the high voltage battery 12 is, for example, 100 V or more. As the high voltage battery 12, for example, a lithium ion storage battery or a nickel hydride storage battery can be used. A smoothing capacitor 13 that smoothes the input voltage of the inverter 11 is provided between the inverter 11 and the high voltage battery 12.

  The inverter 11 includes a plurality of switching elements 21 to 26 connected in series two by two for each phase of the MG 10. That is, the inverter 11 includes a series connection body of the switching elements 21 and 22, a series connection body of the switching elements 23 and 24, and a series connection body of the switching elements 25 and 26. A connection point of each series connection body is connected to one end of each of the U-phase coil 10u, the V-phase coil 10v, and the W-phase coil 10w.

  In the present embodiment, diode built-in reverse conducting IGBT (RC-IGBT) is used as the switching elements 21 to 26. Free wheel diodes 31 to 36 are connected in antiparallel to the switching elements 21 to 26, respectively. In this case, in the reverse conducting IGBT, the IGBT element and the diode element are provided on the same chip, the emitter of the IGBT element and the anode of the diode element are connected, and the collector of the IGBT element and the cathode of the diode element are connected to each other. Are connected.

  The control device 14 is configured with a low voltage battery 15 as a power source and a microcomputer as a main component. The control device 14 operates the inverter 11 so as to control the control amount (for example, torque or rotation speed) of the MG 10 to the command value. Specifically, the control device 14 controls the switching elements 21 to 26 that constitute the inverter 11, and the current sensors 17 a and 17 b that detect the currents Iv and Iw of the MG 10 and the rotation angle of the MG 10 ( A detection value of a rotation angle sensor 18 (for example, a resolver) for detecting the electrical angle θe) is captured. And the control apparatus 14 produces | generates the high / low binary operation signal S1-S6 for every switching element 21-26 by the well-known sine wave PWM control etc. based on the detected value etc. of the said various sensors, The operation signal S1-S6 Is output to the drive units 41 to 46 to turn on / off the switching elements 21 to 26. By operating the switching elements 21 to 26, the current flowing through the coil of the MG 10 is controlled to a predetermined current command value.

  Operation signals S1, S3, S5 for the switching elements 21, 23, 25 on the upper arm (high potential side) and operation signals S2, S4, S6 for the corresponding switching elements 22, 24, 26 on the lower arm (low potential side) Are complementary signals (inverted signals).

  Incidentally, the high voltage system including the high voltage battery 12 and the low voltage system including the low voltage battery 15 are electrically insulated from each other, and transmission / reception of signals between them includes an insulating element such as a photocoupler. This is done via the interface 16.

  The drive units 41 to 46 as drive circuits have a configuration including a drive IC which is a one-chip semiconductor integrated circuit. The drive units 41 to 46 are provided in the respective switching elements 21 to 26 and are output from the control device 14. The switching elements 21 to 26 are turned on and off based on the signals S1 to S6. That is, the drive units 41 to 46 turn on the switching elements 21 to 26 in response to the rising edges of the operation signals S1 to S6, and turn off the switching elements 21 to 26 in response to the falling edges of the operation signals S1 to S6. Let

  In addition, the drive units 41 to 46 perform gate charge / discharge processing in order to suppress surge voltage when the switching elements 21 to 26 are turned on and off. That is, when the switching elements 21 to 26 are turned on, the gate charging process is performed by controlling the charging current of the gates of the switching elements 21 to 26 to a predetermined value. Further, when the switching elements 21 to 26 are turned off, the gate discharge process is performed by controlling the discharge currents of the gates of the switching elements 21 to 26 to a predetermined value. At this time, the gate discharge process may be configured such that the discharge current is variably set, for example, based on the energization current in the ON state of the switching elements 21 to 26. By making the discharge current variable in this way, it becomes possible to appropriately adjust the breaking speed of the switching elements 21 to 26 according to the magnitude of the surge voltage in each case.

  The basic operation of the inverter 11 will be described. Here, with reference to FIGS. 2A and 2B, the switching element 25, as an example in which a current in a positive direction (a direction from the high voltage battery 12 toward the coil 10 w) is passed through the W-phase coil 10 w, The switching operation 26 will be described. FIG. 2B shows an operation signal S5 for the switching element 25 for the upper arm and an operation signal S6 for the switching element 26 for the lower arm, and also shows changes in the output current associated with the switching operation of the switching elements 25 and 26. These operation signals S5 and S6 are turned on complementarily. In FIG. 2B, the period during which the output current flows through the switching element 25 of the upper arm as indicated by A1 in FIG. 2A is indicated as “IGBT”, and as indicated by A2 in FIG. A period during which an output current flows through the free wheel diode 36 of the lower arm is indicated as “FWD”.

  2A and 2B, in the ON period of the switching element 25 of the upper arm, an output current flows like A1 through the switching element 25, and the output current gradually increases (IGBT period). When the upper arm switching element 25 is turned off and the lower arm switching element 26 is turned on, the output current of the coil 10w continuously flows through the freewheel diode 36 as in A2, and the output The current gradually decreases (FWD period). That is, in the FWD period, a forward current (return current) flows through the free wheel diode 36, and the output current decreases accordingly.

  Here, consider a case where an on-failure occurs in the switching element 25 of the upper arm. In such a case, if the upper arm switching element 25 is turned off and the lower arm switching element 26 is turned on after the occurrence of an on-failure, a short circuit occurs in the upper and lower arms, and the switching element may be damaged due to the short circuit current. . Therefore, in the prior art, the presence / absence of a short circuit is determined based on whether or not the output current exceeds the short circuit threshold value, and protection processing such as shutting down energization is performed when a short circuit occurs.

  When a current in a negative direction (a direction from the coil 10w toward the high voltage battery 12) is supplied to the W-phase coil 10w, as shown in FIGS. 3A and 3B, the switching element of the lower arm During the ON period 26, an output current flows like A3 through the switching element 26, and the output current gradually increases (IGBT period). When the lower arm switching element 26 is turned off and the upper arm switching element 25 is turned on, the output current of the coil 10w continuously flows like the A4 via the freewheel diode 35, and the output The current gradually decreases (FWD period). That is, in the FWD period, a forward current (return current) flows through the freewheel diode 35, and the output current decreases accordingly.

  In the prior art, when an on-failure occurs in the switching element 26 of the lower arm, whether or not a short circuit has occurred is determined based on whether or not the output current exceeds the short circuit threshold value. The protection process is implemented.

  In order to reliably protect the switching elements 21 to 26, it is necessary to detect the short-circuit current as soon as possible and to perform the protection process as soon as possible. However, after the occurrence of a short circuit, it is necessary to wait for a current change to determine the short circuit, and there is a limit to the responsiveness in performing protection processing. In particular, when the short-circuit tolerance is reduced due to thinning of the switching element, it is considered that there is less time margin for performing the short-circuit determination and the protection process.

  Therefore, in the present embodiment, the free wheel diode is reversely connected during the period in which the forward current flows through the free wheel diode on either side of the switching elements 21 to 26 of the upper and lower arms (the FWD period in FIGS. 2 and 3). The switching element is forcibly turned off, and the switching element is on-failed based on the difference between the actual value of the current flowing through the coils 10u, 10v, and 10w and the current command value. Is going to be judged. In such a case, even if any one of the switching elements of the upper and lower arms is turned on, the upper and lower arms are prevented from being short-circuited after the switching elements are turned off. In addition, when one of the switching elements is in an on-failure state, the output current does not decrease when the switch is off unlike normal operation. Therefore, there is a divergence between the actual current value and the current command value. Based on the above, it can be determined that an ON failure of the switching element has occurred. At this time, it is possible to determine the occurrence of the ON failure of the switching element before the upper and lower arms are short-circuited.

  In the reverse conducting IGBT (RC-IGBT) provided with the switching elements 21 to 26 and the free wheel diodes 31 to 36 connected in antiparallel with the switching elements 21 to 26 on the same chip, as shown in FIG. When a voltage is applied to the gates of the switching elements 21 to 26 under a situation where a forward current If flows through .about.36, the voltage drop amount Vf in the freewheel diodes 31 to 36 is larger than when no voltage is applied. Become. When the voltage drop amount Vf increases, the power loss in the free wheel diode increases. Therefore, during the period in which the forward current If flows through the freewheel diodes 31 to 36 on either side of the switching elements of the upper and lower arms (the FWD period in FIGS. 2 and 3), the power in the freewheel diodes 31 to 36 In order to suppress loss, current feedback control is performed.

  In the current feedback control, the gate charges of the switching elements 21 to 26 provided on the same chip as the free wheel diodes 31 to 36 in which the forward current flows are charged during the period in which the forward current flows in the free wheel diodes 31 to 36. It is a control that prohibits being performed. Thereby, the operation signals of the switching elements 21 to 26 provided on the same chip as the free wheel diodes 31 to 36 through which the forward current flows are invalidated.

  In this embodiment, each drive unit 41-46 has a function of current feedback control, and the switching elements 21-26 are forcibly turned off by invalidating the operation signals S1-S6 in each drive unit 41-46. I try to make it. Specifically, in each of the drive units 41 to 46, it is determined whether or not a forward current is flowing through the free wheel diode connected to the unit. This process is performed based on the sense voltage of the switching elements 21 to 26, for example. And when it determines with the forward current flowing, the process which changes the operation signal input into the own unit into an OFF operation command as current feedback control is performed. Thereby, charging of the gate charge is prohibited, and the switching element is maintained in the off state.

  Next, a procedure for determining an on failure of the switching elements 21 to 26 will be described. The on failure determination of the switching elements 21 to 26 is performed in the control device 14 based on the difference between the current detection value (actual current) of the phase current of each of the coils 10u, 10v, and 10w and the current command value. Is done.

  Specifically, the control device 14 calculates a current command vector based on the current command value of each phase, and calculates an actual current vector based on the detected current value of each phase detected by the current sensors 17a and 17b. Based on the current command vector and the actual current vector, it is determined whether or not each of the switching elements 21 to 26 has an on-failure.

  An example of a current vector calculation method is shown below. Based on the V-phase current Iv and W-phase current Iw detected by the current sensors 17 a and 17 b and the electrical angle θe detected by the rotation angle sensor 18, the control device 14 uses the U-phase current in the three-phase fixed coordinate system. Iu, V-phase current Iv, and W-phase current Iw are converted into d-axis current Idr and q-axis current Iqr in a two-phase rotational coordinate system (dq coordinate system). Here, the two-phase rotation coordinate system is a coordinate system that rotates at the same angular velocity as the fluctuation angular velocity of the fundamental wave component of the phase current in the three-phase fixed coordinate system. The U-phase current Iu may be calculated from the V-phase current Iv and the W-phase current Iw based on Kirchhoff's law.

  Further, the control device 14 calculates a current amplitude Iar, which is the magnitude of the actual current vector, from the d-axis current Idr and the q-axis current Iqr by the three-square theorem, and uses the inverse trigonometric function to calculate the q An angle between the axis and the current vector (energization phase angle βr) is calculated. On the other hand, the control device 14 calculates a current command vector based on the current command value of each phase and the corresponding electrical angle. And the control apparatus 14 determines the presence or absence of the ON failure of the switching elements 21-26 based on the deviation | shift amount of the actual current vector with respect to a current command vector.

  Specifically, as shown in FIG. 5A, a normal range K1 having a predetermined width is determined based on the current amplitude (magnitude) of the current command vector I *. Then, the control device 14 determines whether or not the current amplitude Iar of the actual current vector is within the normal range K1, and if not, the detected current value (actual value) of the phase current of each of the coils 10u, 10v, and 10w is determined. Current) and the current command value are different from each other by a predetermined amount or more, it is determined that an ON failure has occurred in the switching elements 21 to 26.

  Alternatively, as shown in FIG. 5B, a normal range K2 having a predetermined width is determined based on the energization phase angle of the current command vector I *. Then, the control device 14 determines whether or not the energization phase angle βr of the actual current vector is within the normal range K2, and if not, the detected current value of the phase current of each coil 10u, 10v, 10w ( It is determined that the ON failure of the switching elements 21 to 26 has occurred, assuming that the actual current) and the current command value are different from each other by a predetermined amount or more.

  When the current vector divergence occurs, the control device 14 may determine that there is an on-failure when the current vector divergence continues for a predetermined time. Moreover, it is good to determine the effect of an on failure by the timing at which the coil to be energized (that is, the direction of energization of each coil) is switched. Note that it is determined that an on-failure of the switching elements 21 to 26 has occurred based on both that the current amplitude Iar is not in the normal range K1 and that the energization phase angle βr is not in the normal range K2. It is also possible to do.

  When it is determined that the on failure of the switching elements 21 to 26 has occurred, the control device 14 immediately shuts down the switching elements 21 to 26. In this case, the control device 14 turns off the switching elements 21 to 26 at a cut-off speed (normal cut-off speed) that assumes the same surge voltage suppression as when the switching elements 21 to 26 are normally off. In the system according to the present embodiment, even when the switching elements 21 to 26 are turned on, a short circuit does not occur in the upper and lower arms, and a short circuit current exceeding the specification range (current range assuming normal operation) occurs. Absent. That is, as shown in FIG. 6A, when the upper and lower arms are short-circuited, a short-circuit current of about several thousand A flows, whereas in the configuration of this embodiment, the upper and lower arms can be prevented from being short-circuited. As shown in b), even if an ON failure occurs in the switching elements 21 to 26, the current is suppressed to about several hundred A. For this reason, it is not necessary to perform special interruption processing assuming that a short-circuit current flows, and there is no inconvenience that the interruption processing becomes complicated.

  Further, instead of the determination method based on the current vector described above, the switching elements 21 to 26 are turned on based on a direct comparison between the detected current value of each phase detected by the current sensors 17a and 17b and the current command value. It is also possible to determine the presence or absence of a failure. This will be described with reference to FIG. FIG. 7 shows changes in the phase currents Iu to Iw in the MG 10. Each of the phase currents Iu to Iw fluctuates in a sine wave shape with 360 ° as one cycle, and the phase is shifted by 120 ° for each phase. In FIG. 7, the current command value is indicated by a broken line, the current detection value is indicated by a solid line, and the current is compared with the current command value before the timing t1 when the switching elements 21 to 26 perform the switching operation in a normal state. The phase and amplitude of the detected value (actual current) match. In addition, when an on-failure occurs in any of the switching elements 21 to 26 at timing t1, the phase and amplitude of the current detection value (actual current) do not match the current command value.

  Here, the control device 14 calculates the amplitude of the current command value and the amplitude of the current detection value for any phase current, and the amplitude of the current detection value deviates by more than a predetermined value from the amplitude of the current command value. If there is, it is determined that the on failure of the switching elements 21 to 26 has occurred. At this time, if an on failure has occurred in any of the switching elements 21 to 26, the amplitude of the current detection value is based on the amplitude of the current command value as shown after t1 in FIG. It deviates from the normal range K3 having a predetermined width. Thereby, the on failure of the switching elements 21 to 26 is determined.

  Alternatively, the control device 14 calculates the phase of the current command value and the phase of the current detection value for any of the phase currents, and the phase of the current detection value deviates from the phase of the current command value by a predetermined value or more. In this case, it is determined that an ON failure has occurred in the switching elements 21 to 26. At this time, if an on-failure has occurred in any of the switching elements 21 to 26, as shown after t1 in FIG. 7B, the phase of the current detection value is based on the phase of the current command value. It deviates from the normal range K4 having a predetermined width. Thereby, the on failure of the switching elements 21 to 26 is determined.

  Both the amplitude of the current detection value deviates from the current command value amplitude by a predetermined value or more, and the current detection value phase deviates from the current command value phase by a predetermined value or more. Based on the above, it is also possible to determine that an ON failure has occurred in the switching elements 21 to 26.

  FIG. 8 is a time chart showing the result of a simulation experiment regarding on-failure determination. In FIG. 8, in order from the top, the ON failure timing of the switching element of the W-phase upper arm, the current detection value of each phase, the gate input of the W-phase upper arm, the gate input of the W-phase lower arm, and the IGBT current of the W-phase upper arm , W-phase upper arm FWD current, W-phase lower arm FWD current, W-phase lower arm IGBT current. In FIG. 8, it is assumed that the switching element continues to be turned on / off even after the on failure is determined.

  In FIG. 8, timings t11 to t12 are periods in which a W-phase current flows in a positive direction, and timings t12 to t13 are periods in which a W-phase current flows in a negative direction. During the period from timing t11 to t12, the gate input of the W-phase upper arm is turned on / off at a predetermined on / off ratio, and at that time, the gate input of the W-phase lower arm is held at 0 V (the fluctuation in the figure is noise). is there). At this time, according to the gate input of the W-phase upper arm, the IGBT current of the W-phase upper arm and the FWD current of the W-phase lower arm flow in a complementary manner, whereby the current detection value changes in a sine wave shape. In the W-phase lower arm, there is a period during which forward current flows in the freewheeling diode during the period from timing t11 to t12.

  In the period from timing t12 to t13, the gate input of the W-phase lower arm is turned on / off at a predetermined on / off ratio, and at that time, the gate input of the W-phase upper arm is held at 0 V (the fluctuation amount in the figure is Noise). At this time, in accordance with the gate input of the W-phase lower arm, the IGBT current of the W-phase lower arm and the FWD current of the W-phase upper arm flow in a complementary manner, whereby the current detection value changes in a sine wave shape. In the W-phase upper arm, there is a period during which forward current flows in the freewheeling diode during the period from timing t12 to t13.

  Then, when an on-failure occurs in the switching element of the W-phase upper arm at timing t14, the fact that the on-failure has occurred is determined since the amplitude and phase of the current detection value are subsequently shifted (see X in the figure). . At this time, in the state in which the switching element of the W-phase upper arm is on-failed, the FWD current of the W-phase lower arm does not flow unlike normal times, and therefore the IGBT current of the W-phase upper arm does not decrease. It has become. Therefore, a shift occurs in the change waveform of the current detection value, and it is possible to determine an on failure.

  In addition, when the switching element of the W-phase upper arm is turned on, a short circuit does not occur in the upper and lower arms, so that an excessive increase in the W-phase current is avoided.

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

  The switching elements 21 to 26 to which the free wheel diodes 31 to 36 are reversely connected are turned off during a period in which a forward current flows through the free wheel diodes 31 to 36. In addition to such a configuration, the switching elements 21 to 26 are on-failed based on the difference between the current detection value that is the actual value of the current flowing through the coils 10u, 10v, and 10w and the current command value. It was set as the structure which determines that. Accordingly, it is possible to determine the occurrence of an on-failure of the switching elements 21 to 26 before the short circuit between the upper and lower arms occurs, and it is possible to realize appropriate protection when the switching elements 21 to 26 are on-failure.

  Note that, as in the prior art, when a switching element on-failure occurs, a method of determining an on-failure of the switching element based on a short-circuit current associated with a short circuit between the upper and lower arms flows to protect the switching element. Therefore, it is necessary to detect the short-circuit current immediately after the occurrence of the short-circuit, and specifically, it is necessary to detect the short-circuit current within 200 ns after the short-circuit current starts to flow. In this case, there is a concern about the occurrence of malfunction. On the other hand, in the above configuration, it is possible to sufficiently secure the time required for the on-failure determination as compared with the prior art, and it is possible to prevent malfunction.

  Moreover, since this embodiment is a structure which does not perform the short circuit operation | movement of an upper and lower arm, even if the short circuit tolerance of the switching elements 21-26 is falling, the appropriate protection of the switching elements 21-26 is realizable.

  In the conventional method for detecting a short-circuit current associated with the occurrence of a short circuit between the upper and lower arms, a short-circuit current (a large current that is higher than the normal use level) flows. In addition, it may be necessary to take measures such as interruption after voltage clamping or change of the interruption order due to a difference in withstand voltage. On the other hand, in this embodiment, when the switching elements 21 to 26 are turned on, the switching elements 21 to 26 in the on state are turned off at the same cutoff speed (normal cutoff speed) as when the normal switching elements 21 to 26 are turned on and off. The configuration is to That is, in the method of the present embodiment, since a short-circuit current does not flow, it is only necessary to perform a cutoff process similar to the normal operation, and the configuration becomes complicated even assuming an ON failure of the switching elements 21 to 26. This can be suppressed.

  It is configured that it is determined that the current detection value and the current command value are different from each other by comparing the actual current vector calculated based on the current detection value and the current command vector calculated based on the current command value. In this case, it is possible to realize a configuration that is suitable for quickly detecting a phase current shift caused by an on-failure of the switching elements 21 to 26.

  Alternatively, when the on-failure of the switching elements 21 to 26 is determined by comparing at least one of the current amplitude and phase in the current detection value and current command value of each phase, the coordinate detection of the current detection value is performed. The processing for calculating the current vector need not be performed, and a desired on-failure determination can be realized while simplifying the arithmetic processing.

  In the present embodiment, a diode built-in reverse conducting IGBT (RC-IGBT) is used as the switching elements 21 to 26, and the above-described current feedback control is performed. As a result, an increase in the amount of voltage drop in the free wheel diodes 31 to 36 is avoided, and as a result, an increase in power loss of the free wheel diodes 31 to 36 is suppressed.

(Other embodiments)
You may change the said embodiment as follows, for example.

  In the configuration for determining the on-failure of the switching elements 21 to 26 based on the amplitude of the current detection value, the configuration for performing the on-failure determination based on the transition of the current detection value in a half cycle period from the zero cross point of the current waveform It is good. That is, the current flowing through the coils 10u, 10v, and 10w changes in an alternating manner in a sine wave shape. In such a case, as shown in FIG. 9, in the period TA of a half cycle from the zero cross point where the direction of the current is reversed, the amplitude of the current detection value from the amplitude center C of the AC change tends to decrease (in the figure). When (TB) is shorter than 1/4 period (1/4 of AC period), it is determined that the current detection value and the current command value are different.

  Here, a configuration in which the drive units 41 to 46 perform such current deviation determination is conceivable. In this case, the control device 14 transmits information on the electrical cycle of the MG 10 to the drive units 41 to 46 in addition to the operation signals S1 to S6 described above. In addition, the drive units 41 to 46 acquire, for example, sense currents of the switching elements 21 to 26 as current detection values. Then, the drive units 41 to 46 determine the timing at which current starts to flow through the switching elements 21 to 26 as the zero cross point based on the electrical cycle information, and the current detection value and the current command in the half cycle period from the zero cross point. Judgment that the value deviates.

  In such a configuration, since the failure determination is performed in the drive units 41 to 46, the calculation load in the control device 14 can be reduced. Further, in this case, when determining the failure of the switching elements 21 to 26, the failure determination can be performed without causing a delay in signal transmission between the control device 14 and the drive units 41 to 46. Therefore, the time from the occurrence of the failure to the determination is reduced. It can be shortened. However, it is also possible for the control device 14 to perform the failure determination process that is performed based on the transition of the current detection value with the zero cross point as a reference.

  When failure determination is performed in the drive units 41 to 46 as described above, the drive units 41 to 46 may perform shutdown processing (protection processing) of the switching elements based on the result of the failure determination. In this case, the drive units 41 to 46 may perform the shutdown process for at least the corresponding switching element having an on failure, and the control device 14 may perform the shutdown process for the other switching elements. Alternatively, the drive units 41 to 46 may perform a shutdown process individually by enabling mutual signal transmission in the drive units 41 to 46.

  In the above embodiment, the current feedback control execution entity is the drive units 41 to 46, but is not limited thereto. For example, the control device 14 may be the execution subject. In this case, current feedback control may be performed based on the phase current calculated from the output values of the current sensors 17a and 17b. Specifically, the control device 14 determines whether or not forward current flows through the free wheel diodes 31 to 36 based on the operation state of each of the switching elements 21 to 26 and the phase current. Further, when it is determined that the forward current flows, the control device 14 forces the operation signals S1 to S6 for the switching elements 21 to 26 corresponding to the free wheel diodes 31 to 36 determined to have the forward current flowing. To change to an off operation command. In such a case, instead of a configuration in which the operation signals for the upper and lower arms are output as complementary signals, an operation signal for outputting only one of the operation signals for the upper and lower arms is output. .

  The plurality of switching elements in the power conversion circuit are not limited to diode built-in reverse conducting IGBTs (RC-IGBTs). In short, any other switching element may be used as long as it has a plurality of switching elements and a freewheel diode connected in reverse parallel thereto.

  The power conversion circuit to which the present invention is applied is not limited to the inverter 11 but may be a DCDC converter. Further, the power conversion circuit is not limited to the power conversion circuit mounted on the vehicle, and may be mounted on a moving body other than the vehicle or mounted on a stationary device.

  DESCRIPTION OF SYMBOLS 10 ... MG (AC motor), 11 ... Inverter (power conversion circuit), 14 ... Control apparatus, 21-26 ... Switching element, 31-36 ... Free wheel diode, 41-46 ... Driver unit.

Claims (7)

A plurality of switching elements (21 to 26) provided in the upper arm and the lower arm to form a series connection body, and free wheel diodes (31 to 36) connected in reverse parallel to the plurality of switching elements, respectively. coil electrically connected to the power conversion circuit of an AC motor (10) (11) or is applied to the power conversion circuit composed of a DCDC converter comprising a coil for voltage conversion, before Kiko yl current flowing through a predetermined current A switching element drive device (14, 41 to 46) for turning on and off the plurality of switching elements to control to a command value,
One of the switching elements of the upper and lower arms is alternately switched between the on state and the off state, and the other switching element is turned off when the one switching element is turned off during the period in which the one switching element is alternately turned on and off. Switch control means for setting a forward current to flow through the freewheel diode on the side and turning off the other switching element;
It is determined, based on the fact that the actual value of the current flowing through the coil is different from the current command value , that the switching element is in an on-failure period during which the one switching element is alternately turned on / off. A determination means;
A drive device for a switching element, comprising: When the switching element for energizing the coil is turned on and off, a cutoff speed when the switching element is turned off is a normal cutoff speed, and the switching element is turned off at the normal cutoff speed,
The switching element drive device according to claim 1, wherein when the determination unit determines that the switching element is in an on-failure, the switching element in the on state is turned off by the normal cutoff speed. A driving device for detecting a current flowing through the coil by current detection means (17a, 17b) and calculating a current vector by coordinate conversion using the detected current value;
The determination means has a difference between the actual current value and the current command value by comparing the actual current vector calculated based on the detected current value and the current command vector calculated based on the current command value. The switching element driving device according to claim 1, wherein the determination is performed.   The determination means determines that the actual value of the current and the current command value are different from each other based on at least one of a magnitude and a phase in the actual current vector and the current command vector. The switching element driving device according to claim 3. A drive device for detecting a current flowing through the coil by current detection means (17a, 17b) and obtaining a current detection value thereof,
The determination means performs a determination that an actual value of the current is different from the current command value by comparing at least one of a current amplitude and a phase in the current detection value and the current command value. Item 3. The switching element drive device according to Item 1 or 2. A driving device for detecting a current flowing in the coil by current detection means (17a, 17b, 41 to 46) and obtaining a current detection value thereof;
The determination means is configured such that the amplitude of the detected current value from the center of the amplitude of the AC change is a half cycle period from the zero cross point where the direction of the current reverses between positive and negative when the current flowing through the coil is a sinusoidal AC change. 3. The switching element according to claim 1, wherein when the period of decreasing trend is shorter than ¼ period, it is determined that the actual value of the current flowing through the coil is deviated from the current command value. Drive device. A control unit (14) that generates and outputs an operation signal for turning on and off the plurality of switching elements, and is provided in each of the plurality of switching elements, and the switching element is turned on based on the operation signal output from the control unit. A drive circuit (41 to 46) for operating and turning off,
The control unit outputs an electric cycle of the AC motor to the drive circuit,
The drive circuit sets the timing at which current starts to flow to the switching element based on the electrical cycle of the AC motor as the zero cross point, and the actual value of the current as the determination means in a half cycle period from the zero cross point The switching element drive device according to claim 6, wherein it is determined that the current command value is deviated from the current command value.