JP2012186937A - Circuit for driving switching element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem in which: a switching element S*# to be driven cannot be driven if there occur any anomalies in a constant current switching element 26 or a discharge switching element 30.SOLUTION: The constant current switching element 26 and the discharge switching element 30 are connected to a gate of the switching element S*# via a gate resistor 28. A voltage across the gate resistor 28 is converted to an output voltage Vgi by a differential amplifier circuit 70 and fed into an anomaly determination section 72. The anomaly determination section 72 determines whether or not there occur any anomalies in the constant current switching element 26 or discharge switching element 30 according to a current flowing through the gate resistor 28.

Description

  The present invention uses a voltage-controlled switching element as a driving target switching element, and performs a process of charging either the positive or negative charge to the open / close control terminal in order to switch the switching state of the driving target switching element. The present invention also relates to a drive circuit for a switching element that limits the charge rate of the charge by a limiting resistor.

  As this type of driving circuit, for example, as shown in Patent Document 1 below, a charging path for charging a positive charge to the gate of an IGBT as a driving target switching element, and a positive charge from the gate are discharged. It is well known that each of the discharge paths includes a series connection body of a gate resistor and a switching element.

JP 2003-284318 A

  By the way, when an abnormality occurs in the driving function of the IGBT, such as a short abnormality in which the switching element of the charging path or the discharging path is normally closed or an open abnormality in which the switching element is normally open, it is desired to deal with this.

  The present invention has been made in the process of solving the above-described problems, and an object of the present invention is to provide a new switching element drive circuit capable of determining whether there is an abnormality in the drive function of the drive target switching element. is there.

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

  According to the first aspect of the present invention, a voltage-controlled switching element is used as a driving target switching element, and the switching control terminal is charged with either a positive or negative charge so as to switch the switching state of the driving target switching element. In performing a process, in a switching element driving circuit that limits the charge rate of the charge by a limiting resistor, a detecting unit that detects a current flowing through the limiting resistor, and a current detected by the detecting unit And determining means for determining whether or not there is an abnormality in the function of driving the drive target switching element.

  The mode of charge movement during charge / discharge processing of the switching control terminal of the driving target switching element is determined by the parasitic capacitance of the switching control terminal of the driving target switching element, the specifications of the driving circuit, and the like. However, when an abnormality occurs in the function of driving the switching element to be driven, a situation different from that in which the charge movement mode is assumed may occur. In the above invention, in view of this point, the presence or absence of abnormality is determined based on the detection result of the current flowing through the limiting resistor.

  According to a second aspect of the present invention, in the first aspect of the invention, the detection means includes a differential amplifier circuit connected to both ends of the limiting resistor and detecting a potential difference between the two ends. To do.

  When noise is superimposed on the limiting resistor, it is highly possible that the potential difference between both ends of the pair of end portions changes, but the potential difference between both ends does not change. In the above invention, in view of this point, the influence of noise on the current detection result can be suitably suppressed by providing the differential amplifier circuit.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the limiting resistor includes a charging path for charging the open / close control terminal with the other charge and the charge of the other Is shared by both discharge paths for discharging from the open / close control terminal.

  In the above invention, since the limiting resistor constitutes both the charging path and the discharging path, the current flowing during the charging period of the other charge and the charge of the other using the single limiting resistor Both currents flowing during the discharge period (charging period of one of the charges) can be detected.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, when charging one of the other charges to the open / close control terminal of the drive target switching element, the constant current is controlled to be a constant value. It further has a current control means.

  In the above invention, since the constant current control is performed at the time of charging one of the other charges, the limiting resistor according to the request for the discharge speed at the time of discharging the other charge (charging one of the charges) When adjusting the resistance value, it is possible to suitably avoid being restricted by the charge of one of the other charges.

  The invention according to claim 5 is the invention according to claim 4, wherein the constant current control means includes a constant current resistor provided in the charging path separately from the limiting resistor, and the constant current resistor. A switching element for constant current connected in series to the body, and an operating means for operating an open / close control terminal of the switching element for constant current so that a voltage drop amount of the constant current resistor becomes a target value. It is characterized by.

  In the above invention, even if the resistance value of the constant current resistor changes, the voltage drop amount is considered to be controlled to the target value as long as it is not disconnected or short-circuited. For this reason, if the limiting resistor and the constant current resistor are the same, it is difficult to detect an abnormality in which the resistance value of the constant current resistor changes. In this respect, in the above invention, the constant current resistor and the limiting resistor are separated from each other, thereby detecting an abnormality in the resistance value of the constant current resistor as a change in the voltage drop of the limiting resistor, etc. can do.

  According to a sixth aspect of the present invention, in the fifth aspect of the invention, the constant current control means uses a DC voltage source that supplies the other charge to the open / close control terminal of the drive target switching element. The other charge is charged until the voltage between one end of the current flow path of the switching element to be driven and the open / close control terminal reaches the output voltage of the DC voltage source, The output voltage is set to a voltage capable of performing the constant current control up to a charging voltage of the switching control terminal having a saturation current that is a maximum current that normally flows in the driving target switching element. To do.

  The constant current control means is configured such that the voltage drop between the limiting resistor and the constant current resistor and the constant current switching are applied to the voltage between one end of the current flow path of the switching element to be driven and the switching control terminal. The constant current control cannot be performed after the value obtained by adding the voltage drop amount in the element becomes the output voltage of the DC voltage source. In this regard, according to the above-described invention, when the drive target switching element is normally driven, constant current control can be performed until the mirror period has passed.

  According to a seventh aspect of the present invention, in the first or second aspect of the present invention, a charging path for charging the other charge, a charging switching element for opening and closing the charging path, and the other charge. A discharge path for discharging and a discharging switching element for opening and closing the discharging path, wherein the charging switching element, the discharging switching element, the detecting means, and the determining means are configured in an integrated circuit The charging switching element and the discharging switching element are connected to the open / close control terminal of the drive target switching element via different terminals of the integrated circuit, and the limiting resistor Both ends of the integrated circuit connected to the charging switching element and the discharging switching element, respectively. Characterized in that it is connected to the detecting means via.

  In the above invention, both ends of the detection means and the limiting resistor are connected using a terminal for connecting the charging switching element and the switching control terminal and a terminal for connecting the discharging switching element and the switching control terminal. Therefore, an increase in the number of terminals of the integrated circuit can be avoided.

  According to an eighth aspect of the present invention, in the invention according to any one of the third to sixth aspects, the determination unit charges the opening / closing control terminal of the drive target switching element with the other charge. When the current flowing through the limiting resistor in the period exceeds a charging-side large current threshold, it is determined that there is an abnormality in the function of driving the drive target switching element.

  According to a ninth aspect of the present invention, in the invention according to any one of the third to sixth and eighth aspects, the determination means charges the one of the other charges to the open / close control terminal of the drive target switching element. When the current flowing through the limiting resistor is less than the charging-side small current threshold during the period to be determined, it is determined that there is an abnormality in the function of driving the drive target switching element.

  According to a tenth aspect of the present invention, in the invention according to any one of the third to ninth aspects, the determination means discharges the other charge from the open / close control terminal of the drive target switching element. When the current flowing through the limiting resistor during a period exceeds a discharge-side large current threshold, it is determined that there is an abnormality in the function of driving the drive target switching element.

  According to an eleventh aspect of the present invention, in the invention according to any one of the third to tenth aspects, the determination means discharges the other charge from the open / close control terminal of the drive target switching element. When the current flowing through the limiting resistor during the period is less than the discharge-side small current threshold, it is determined that there is an abnormality in the function of driving the drive target switching element.

  The invention according to claim 12 is the invention according to any one of claims 3 to 11, wherein the discharge path is between one end of the current flow path of the drive target switching element and the switching control terminal. A discharge switching element connected in series to the limiting resistor, and the discharge between the one end of the current flow path of the driving target switching element and the open / close control terminal. A low resistance path connected by a path having a resistance value smaller than the path, an off-holding switching element that opens and closes the low resistance path, and a function for driving the switching target switching element by the determination unit. A fail-safe means for turning on the off-holding switching element.

  In the above-described invention, by using the off-holding switching element, it is possible to reliably discharge the other charge charged to the opening / closing control terminal of the driving target switching element. This eliminates the potential difference between one end of the current flow path of the driving target switching element and the open / close control terminal, so that the driving target switching element can be turned off.

  A thirteenth aspect of the present invention is the invention according to any one of the third to twelfth aspects, wherein the discharge path is between one end of a current flow path of the drive target switching element and the open / close control terminal. A discharge switching element connected in series to the limiting resistor, and the discharge between the one end of the current flow path of the driving target switching element and the open / close control terminal. It is determined that there is an abnormality in the function of driving the driving target switching element by the determination means and the high resistance path connected by a path having a resistance value larger than the path, the soft cutoff switching element that opens and closes the high resistance path. A fail-safe means for turning on the soft-blocking switching element.

  In the above-described invention, by using the soft cutoff switching element, it is possible to reliably discharge the other charge charged to the open / close control terminal of the drive target switching element. This eliminates the potential difference between one end of the current flow path of the driving target switching element and the open / close control terminal, so that the driving target switching element can be turned off.

  According to a fourteenth aspect of the present invention, in the invention according to any one of the first to thirteenth aspects, when the determination means determines that there is an abnormality in the function of driving the driving target switching element, the driving target It further comprises a blocking means for blocking the input of the on / off command signal of the switching element.

  In the above invention, when it is determined that there is an abnormality in the function of driving the drive target switching element, it is possible to reliably avoid the situation where the drive target switching element is turned on by the on operation command.

  In the invention of claim 15, in the invention of any one of claims 1 to 14, when it is judged by the judging means that there is an abnormality in the function of driving the switching element to be driven, that fact It further comprises a notification means for notifying outside.

1 is a system configuration diagram according to a first embodiment. FIG. The circuit diagram which shows the circuit structure of the drive unit concerning the embodiment. The flowchart which shows the procedure of the abnormality determination process concerning the embodiment. The flowchart which shows the procedure of the abnormality determination process concerning 2nd Embodiment. The circuit diagram which shows the circuit structure of the drive unit concerning 3rd Embodiment.

<First Embodiment>
Hereinafter, a first embodiment in which a drive circuit for a switching element according to the present invention is applied to a drive circuit for a power conversion circuit connected to a rotating machine as an in-vehicle main machine will be described with reference to the drawings.

  FIG. 1 shows an overall configuration of a control system according to the present embodiment. The motor generator 10 is an in-vehicle main machine and is mechanically coupled to drive wheels (not shown). Motor generator 10 is connected to high voltage battery 12 via inverter INV and boost converter CNV. Here, boost converter CNV includes a capacitor C, a pair of switching elements Scp and Scn connected in parallel to capacitor C, and a reactor that connects a connection point between the pair of switching elements Scp and Scn and the positive electrode of high-voltage battery 12. L. The voltage of the high voltage battery 12 (for example, 100 V or more) is boosted up to a predetermined voltage (for example, “666 V”) by turning on / off the switching elements Scp, Scn. On the other hand, the inverter INV includes a series connection body of the switching elements Sup and Sun, a series connection body of the switching elements Svp and Svn, and a series connection body of the switching elements Swp and Swn. The points are connected to the U, V, and W phases of the motor generator 10, respectively. In the present embodiment, an insulated gate bipolar transistor (IGBT) is used as these switching elements S * # (* = u, v, w, c; # = p, n). In addition, a diode D * # is connected in antiparallel to each of these.

  The control device 18 is a control device that uses the low-voltage battery 16 as a power source. The control device 18 controls the motor generator 10 and operates the inverter INV and the boost converter CNV to control the control amount as desired. Specifically, operation signals gcp and gcn are output to drive unit DU in order to operate switching elements Scp and Scn of boost converter CNV. Further, in order to operate the switching elements Sup, Sun, Svp, Svn, Swp, Swn of the inverter INV, operation signals gup, gun, gvp, gvn, gwp, gwn are output to the drive unit DU. Here, the high-potential side operation signal g * p and the corresponding low-potential side operation signal g * n are complementary to each other. In other words, the high-potential side switching element S * p and the corresponding low-potential side switching element S * n are alternately turned on.

  Here, the high-voltage system including the high-voltage battery 12 and the low-voltage system including the low-voltage battery 16 are insulated from each other, and transmission and reception of signals between them is an interface including an insulating element such as a photocoupler. 14 is performed.

  FIG. 2 shows the configuration of the drive unit DU.

  As shown in the figure, the drive unit DU includes a drive IC 20 that is a one-chip semiconductor integrated circuit. The drive IC 20 includes a power source 22 having a terminal voltage Vom, which is connected to the terminal T1 via a constant current resistor 24 and a P-channel MOS field effect transistor (constant current switching element 26). The gate of the switching element S * # is connected to the terminal T1 through the gate resistor 28.

  On the other hand, the terminal T1 is connected to the terminal T2 through the discharging switching element 30. The terminal T2 is connected to the output terminal (emitter) of the switching element S * #.

  An inverting input terminal of an operational amplifier 32 is connected between the constant current resistor 24 and the constant current switching element 26, and the reference voltage Vref of the reference power supply 31 is connected to the non-inverting input terminal of the operational amplifier 32. Applied. The output terminal of the operational amplifier 32 is connected to the gate of the constant current switching element 26 via the switching element 34. Thus, when the output terminal of the operational amplifier 32 and the gate of the constant current switching element 26 are connected, the constant current switching element is set so that the voltages at the inverting input terminal and the non-inverting input terminal of the operational amplifier 32 are the same. 26 gate voltages are manipulated. As a result, the voltage drop amount of the constant current resistor 24 is manipulated to the target value (Vom−Vref), and as a result, the charging current of the gate of the switching element S * # can be controlled to a constant value.

  Thus, in the present embodiment, the charging process of the gate of the switching element S * # is performed by constant current control. On the other hand, the gate discharge process is performed while limiting the discharge current by the gate resistor 28 by connecting the gate and the emitter via the gate resistor 28. Here, the resistance value R2 of the gate resistor 28 is adjusted to an appropriate value for limiting the discharge current, but is not limited by the charging process. This is because the charging process is performed by constant current control.

Incidentally, the controllability of the constant current control decreases as the gate-emitter voltage (gate voltage Vge) of the switching element S * # increases. This is because the sum of the voltage drop amount at the gate resistor 28 due to a constant current, the minimum value of the voltage drop amount at the constant current switching element 26 (source-drain voltage Vds), and the gate voltage Vge is the reference voltage. This is because when the voltage is Vref or higher, the current value cannot be controlled to a constant value depending on the operation of the gate voltage of the constant current switching element 26. Therefore, in the present embodiment, the controllability of the constant current control does not deteriorate until the gate voltage (maximum voltage Vmax) in which the maximum value Imax of the current Ic when the switching element S * # is normally driven is a saturation current. In addition, the setting of the voltage Vom of the power source 22 is as follows.
R2 · (Vom−Vref) / R1 + Vmax + Vds ≦ Vref
In the above equation, the resistance value R1 of the constant current resistor 24 is used. The first term is the voltage drop amount of the gate resistor 28.

  The discharge switching element 30 and the switching element 34 are operated by a drive control unit 36 in the drive IC 20. That is, in the drive control unit 36, switching is performed by complementarily turning on and off the switching element 34 and the discharging switching element 30 based on the operation signal g * # input via the terminal T3 and the three-state buffer 38. Drive element S * #. That is, when the operation signal g * # becomes an on operation command, the switching element 34 is turned on and the discharge switching element 30 is turned off, and when the operation signal g * # becomes an off operation command, the switching element 34 And the discharge switching element 30 is turned on.

  The gate of the switching element S * # is connected to the terminal T4 via the soft cutoff resistor 40, and the terminal T4 is connected to the terminal T2 via the soft cutoff switching element.

  The terminal T1 is connected to the terminal T2 via a series connection body of the Zener diode 44 and the clamping switching element 46. Here, the breakdown voltage of the Zener diode 44 limits the gate voltage of the switching element S * # to such an extent that an excessive current does not flow through the switching element S * #.

  On the other hand, the switching element S * # includes a sense terminal St that outputs a minute current having a correlation with a current (collector current) flowing between its input terminal (collector) and output terminal (emitter). The sense terminal St is electrically connected to the emitter via a series connection body of resistors 50 and 51. As a result, a voltage drop occurs in the resistor 51 due to the current output from the sense terminal St. Therefore, the voltage drop amount due to the resistor 51 has a correlation with the current flowing between the input terminal and the output terminal of the switching element S * #. It can be an electrical state quantity.

  The amount of voltage drop due to the resistor 51 is taken into the non-inverting input terminal of the comparator 52 via the terminal T5. On the other hand, the threshold voltage Vth of the threshold power supply 54 is applied to the inverting input terminal of the comparator 52. Accordingly, when the collector current becomes equal to or greater than the threshold current, the output signal of the comparator 52 is inverted from the logic “L” to the logic “H”. The logic “H” signal output from the comparator 52 is applied to the clamp switching element 46 and is taken into the delay 56. The delay 56 outputs a fail signal FL when the input signal becomes logic “H” for a predetermined time. The fail signal FL turns on the soft shut-off switching element 42 via the OR circuit 58 to force the switching element S * # to be in the OFF state, or the constant current switching element 26 and the discharge switching element 30. The drive control unit 36 is instructed to stop the drive.

  According to such a configuration, when an overcurrent flows through the switching element S * #, first, the Zener diode 44 is turned on in accordance with the ON operation of the clamping switching element 46, so that the switching element S * # The gate voltage decreases. Thereby, the electric current which flows through switching element S * # can be restrict | limited. After that, when the overcurrent continues for a predetermined time, the switching element S * # is forcibly turned off because the soft cutoff switching element 42 is turned on.

  As a result, the state where the collector current is equal to or greater than the threshold value continues for a predetermined time or longer, so that the soft cutoff switching element 42 is turned on, and the charge of the gate of the switching element S * # is transferred via the soft cutoff resistor 40. Discharged. Here, the soft-blocking resistor 40 is used to increase the resistance value of the discharge path. This is because, under a situation where the collector current is excessive, if the speed at which the switching element S * # is switched from the on state to the off state, in other words, the cutoff speed between the collector and the emitter is increased, the surge will be excessive. This is in view of the possibility of becoming. For this reason, under the situation where the collector current is determined to be equal to or greater than the threshold value, the gate of the switching element S * # is connected by a path having a larger resistance value than the discharge path including the gate resistor 28 and the discharge switching element 30. Discharge.

  The fail signal FL is output to the low voltage system (control device 18) via the terminal T8. In addition, the fail signal FL shuts down the inverter INV and the converter CNV in the fail processing unit 14a shown in FIG. Incidentally, the configuration of the fail processing unit 14a may be, for example, as shown in FIG. 3 of Japanese Patent Laid-Open No. 2009-60358.

  The drive unit DU further includes an N-channel MOS field effect transistor (off-holding switching element 62) for short-circuiting between the gate and emitter of the switching element S * #. The off-holding switching element 62 is provided as close as possible to the switching element S * # in order to connect the gate and emitter of the switching element S * # with a low resistance. Of the paths connecting the gate and the emitter of the switching element S * #, the impedance of the path including the off-holding switching element 62 is set to be lower than the impedance of the path including the gate resistor 28. Yes. This is because when the switching element S * # is turned off in response to the operation signal g * #, the parasitic between the input terminal (collector) or output terminal (emitter) of the switching element S * # and the gate. This is to prevent the switching element S * # from being erroneously turned on due to the high frequency noise superimposed on the gate through the capacitor.

  The gate of the off-holding switching element 62 is connected to an off-holding circuit 64 in the drive IC 20 via a terminal T6. The off hold circuit 64 monitors the gate voltage of the switching element S * # based on the voltage applied to the terminal T1, and performs a process of turning on the off hold switching element 62 when this voltage becomes a predetermined voltage. Is what you do. Further, a signal output from the drive control unit 36 to the gate of the discharge switching element 30 is monitored, and a process for turning off the off-holding switching element 62 in synchronization with the discharge switching element 30 being turned off. It is also something to do.

  The drive IC 20 further includes an abnormality determination unit 72 that determines whether there is an abnormality (driving abnormality) in which the switching element S * # cannot be normally driven. The abnormality determination unit 72 determines the presence or absence of drive abnormality based on the current flowing through the gate resistor 28. Specifically, the end of the gate element 28 on the gate side of the switching element S * # is connected to the terminal T7. Thereby, the potential difference between the terminals T1 and T7 becomes the voltage drop amount of the gate resistor 28. This is converted into the output voltage Vgi of the differential amplifier circuit 70 and input to the abnormality determination unit 72. The abnormality determination unit 72 determines whether there is a drive abnormality based on the output voltage Vgi.

  If it is determined that there is a drive abnormality, the inverter INV and the converter CNV are shut down by outputting the fail signal FL to the fail processing unit 14a shown in FIG. 1 via the OR circuit 60 and the terminal T8. . Further, by outputting the fail signal FL to the three-state buffer 38, the input of the operation signal g * # is blocked. In addition, the switching element 34 is turned off by outputting the fail signal FL to the drive control unit 36. Further, the fail signal FL is output to the OR circuit 58, whereby the soft cutoff switching element 42 is turned on.

  FIG. 3 shows a procedure of abnormality determination processing by the abnormality determination unit 72. This process is repeatedly executed at a predetermined cycle, for example.

  In this series of processes, first, in step S10, it is determined whether or not the operation signal g * # has been switched from an on operation command to an off operation command. If the determination in step S10 is affirmative, in step S12, the timer T counts the period during which the current flowing through the gate resistor 28 is detected by the gate charging process. In a succeeding step S14, it is determined whether or not the timer T is equal to or longer than a threshold time Tth1. This process is for determining whether or not to end the process for determining whether there is a drive abnormality based on the detection of the current flowing through the gate resistor 28 during the charging process. Here, the threshold time Tth1 is set to a time that is less than or equal to the time when the charging of the gate is expected to be completed, and is particularly set to be less than or equal to the time required until the controllability of the constant current control is assumed to deteriorate. It is desirable.

  When a negative determination is made in step S14, it is determined in step S16 whether or not the output voltage Vgi of the differential amplifier circuit 70 is equal to or higher than the charging side small current threshold VthL1 and equal to or lower than the charging side large current threshold VthH1. To do. This process is for determining the presence or absence of drive abnormality. Here, the charging-side small current threshold VthL1 is for determining that the actual amount of current flowing through the gate resistor 28 during the charging process is excessively smaller than the assumed current value. Such a situation may be caused by, for example, an open abnormality in which the constant current switching element 26 is normally open. On the other hand, the charging-side large current threshold VthH1 is for determining that the actual amount of current flowing through the gate resistor 28 during the charging process is excessively larger than the assumed current value. Such a situation can occur, for example, due to a short circuit abnormality in which the constant current switching element 26 is normally closed. If a positive determination is made in step S16, the process returns to step S12.

  On the other hand, if a positive determination is made in step S14, the timer T is initialized in step S18.

  When the process of step S18 is completed or when a negative determination is made in step S10, it is determined in step S20 whether or not the operation signal g * # has been switched from the off operation command to the on operation command. To do. If the determination in step S20 is affirmative, in step S22, the timer T counts the period during which the current flowing through the gate resistor 28 is detected by the gate discharge process, and the timing operation is performed. In a succeeding step S24, it is determined whether or not the timer T is equal to or longer than a threshold time Tth2. This process is for determining whether or not to end the process of determining whether there is a drive abnormality based on the detection of the current flowing through the gate resistor 28 during the discharge process. Here, the threshold time Tth2 is set to be equal to or shorter than the time required for completing the gate discharge process.

  If a negative determination is made in step S24, the result of inverting the sign of the output voltage Vgi of the differential amplifier circuit 70 in step S26 is equal to or greater than the discharge side small current threshold VthL2 and equal to or less than the discharge side large current threshold VthH2. It is determined whether or not. This process is for determining the presence or absence of drive abnormality. Here, the discharge-side small current threshold VthL2 is for determining that the actual amount of current flowing through the gate resistor 28 during the discharge process is excessively smaller than the assumed current value. Such a situation may be caused by, for example, an open abnormality in which the discharge switching element 30 is normally open. On the other hand, the discharge-side large current threshold VthH2 is for determining that the actual amount of current flowing through the gate resistor 28 during the discharge process is excessively larger than the assumed current value. Such a situation may occur, for example, due to a short circuit between the power supply 22 and the terminal T1. If a positive determination is made in step S26, the process returns to step S22.

  On the other hand, when a positive determination is made in step S24, the timer T is initialized in step S28. When a negative determination is made in steps S16 and S26, it is determined in step S30 that there is a drive abnormality and a fail safe process is performed. That is, first, after the switching element 34 is turned off, the soft cutoff switching element 42 is turned on. Secondly, by operating the three-state buffer 38, the input of the operation signal g * # is blocked. Third, a fail signal FL is output. By this fail signal FL, the logical value of the operation signal g * # input to the drive unit DU corresponds to the always-off operation command in the interface 14 regardless of the value of the operation signal g * # output from the control device 18. It is fixed to what you did. Thereby, the inverter INV and the converter CNV are shut down. Further, it is possible to grasp that a drive abnormality has occurred on the control device 18 side, and as a result, the control device 18 can notify the user to that effect.

  In addition, when the process of said step S28, S30 is completed, or when negative determination is made in step S20, this series of processes is once complete | finished.

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

  (1) By using the current flowing through the gate resistor 28, it can be determined whether or not there is an abnormality in the function of driving the switching element S * #.

  (2) Based on the output voltage Vgi of the differential amplifier circuit 70 connected to both ends of the gate resistor 28, the presence / absence of drive abnormality was determined. Thereby, the influence of the noise with respect to the detection result of an electric current can be suppressed suitably.

  (3) The gate resistor 28 is shared by both the charging path for charging positive charges to the gate of the switching element S * # and the discharging path for discharging positive charges from the gate. Thereby, both the current flowing during the charging period and the current flowing during the discharging period can be detected as a voltage drop amount of a single resistor.

  (4) By performing the charging process as constant current control, the resistance value R2 of the gate resistor 28 can be set only for adjusting the discharge rate.

  (5) A constant current resistor 24 is provided separately from the gate resistor 28. Thereby, depending on the setting of the charging side small current threshold VthL1 and the charging side large current threshold VthH1, it is possible to detect an abnormality in the resistance value R1 of the constant current resistor 24. On the other hand, when the gate resistor 28 and the constant current resistor 24 are shared, the voltage drop amount is controlled to the target value even if the resistance value of the constant current resistor 24 changes. May not be detected.

  (6) The constant current control can be performed up to the gate voltage (maximum voltage Vmax) in which the maximum value Imax of the current that normally flows through the switching element S * # is the saturation current. Thereby, when the switching element S * # is normally driven, constant current control can be performed until the mirror period is passed, and thus switching loss can be reduced.

  (7) When it is determined that there is an abnormality in the function of driving the switching element S * #, the soft cutoff switching element 42 is turned on. Thereby, even when the switching element S * # is in the on state, it is possible to suitably suppress a surge when the switching element S * # is forcibly turned off.

(8) When it is determined that there is an abnormality in the function of driving the switching element S * #, the input of the operation signal g * # to the drive control unit 36 is blocked by the three-state buffer 38. Thus, it is possible to reliably avoid the situation where the switching element S * # is turned on by the on operation command.
<Second Embodiment>
Hereinafter, the second embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  FIG. 4 shows a procedure of abnormality determination processing by the abnormality determination unit 72 according to the present embodiment. This process is repeatedly executed at a predetermined cycle, for example. 4 that correspond to the processes shown in FIG. 3 are given the same step numbers for the sake of convenience.

As shown in the figure, in the present embodiment, when a drive abnormality occurs, the off-holding switching element 62 is turned on in step S30a. This process is particularly effective when the fail processing unit 14a is configured not to shut down the inverter INV and the converter CNV. In other words, in this case, the switching element S * # that does not have a driving abnormality can be continuously driven by fail-safe processing or the like. In this case, the malfunction of the switching element S * # to be driven may be induced by noise mixed in the drive unit DU in which the drive abnormality has occurred. Such a situation can be suitably avoided by maintaining the off-holding switching element 62 in the on state.
<Third Embodiment>
Hereinafter, the third embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  FIG. 5 shows the configuration of the drive unit DU. In FIG. 5, the same reference numerals are given for the sake of convenience corresponding to the members shown in FIG.

  As shown in the figure, in this embodiment, the constant current switching element 26 is connected to the terminal T1, and the discharge switching element 30 is connected to the terminal T7, so that the terminal of the drive IC 20 is connected to the charging path and the discharging path. Are different from each other.

  Even in this case, for example, the presence or absence of drive abnormality can be determined based on the current flowing through the gate resistor 28 during the discharge process. That is, it is considered that when the current flowing through the gate resistor 28 is excessively small during the discharge process, an open abnormality or the like in which the discharge switching element 30 or the constant current switching element 26 is normally open occurs. Further, if the current flowing through the gate resistor 28 is excessively large during the discharge process, it is considered that a short circuit abnormality has occurred in which the constant current switching element 26 is normally closed.

  Such a process may be performed in a period in which a current flows in a period in which the discharge switching element 30 is in an on state. However, the present invention is not limited to this. For example, the discharge switching element 30 may be performed after a period during which a current is expected to flow out of a period in which the discharge switching element 30 is in an on state. That is, for example, when the current at this time is not zero, it is considered that a short circuit abnormality in which the constant current switching element 26 is normally closed has occurred.

However, not only during the period in which the discharge switching element 30 is in the on state, but when a current flows through the gate resistor 28 when the discharge switching element 30 is being turned off, there is a short circuit abnormality in which the discharge switching element 30 is normally closed. It may be determined that it has occurred.
<Other embodiments>
Each of the above embodiments may be modified as follows.

About judgment means
In each of the above embodiments, not only the voltage Vgi at the threshold times Tth1 and Tth2, but also the period from switching to the on operation command to switching to the off operation command, or from switching to the off operation command to switching to the on operation command. The presence or absence of abnormality may be determined based on the voltage Vgi during the period.

  In each of the above embodiments, the presence / absence of an abnormality may be determined based on the time during which current flows through the gate resistor 28. Thereby, for example, it can be determined that a short circuit abnormality or the like has occurred in the constant current switching element 26 based on the current flowing through the gate resistor 28 over the entire period in which the discharge switching element 30 is in the ON state.

About detection means
The present invention is not limited to the one provided with a differential amplifier circuit that detects a potential difference between both ends of the limiting resistor. For example, in the third embodiment (above FIG. 5), if it is determined whether or not there is an abnormality only when the discharge switching element 30 is in the ON state, the potential of the terminal T1 and the predetermined potential with respect to the terminal T2 are You may comprise with the means to compare the magnitude of.

  Note that the detection means is not limited to one configured in the drive IC 20.

"Constant current resistor"
In the first embodiment, the constant current resistor may be shared with the gate resistor 28. In this case, even if the resistance value changes even if the gate resistor 28 is not short-circuited or disconnected, the voltage drop amount is controlled to the target value, so that an abnormality cannot be detected for the change in resistance value. However, even in this case, it is possible to detect the disconnection or short circuit of the gate resistor and the abnormality of the constant current switching element 26 and the discharge switching element 30.

  A constant current resistor may be externally attached to the drive IC 20.

"Constant current control means"
The constant current switching element is not limited to a MOS field effect transistor, and may be, for example, a bipolar transistor.

  The present invention is not limited to the one provided with the constant current switching element and the operation means for operating the switching control terminal of the constant current switching element to control the voltage drop amount of the constant current resistor to the target value. For example, you may provide a constant current diode and the switching element connected in series with this.

  In addition, it is good also as what discharges a positive charge (charges a negative charge), not only what charges a positive charge to a gate by a constant current control means.

About constant current control
In each of the above embodiments, instead of the constant current control, the switching element that opens and closes between the power source 22 and the gate of the switching element S * # is operated in a binary manner, so that the gate is positively controlled by so-called constant voltage control. You may perform the process which charges an electric charge.

"About fail-safe measures"
In the second embodiment, the soft-breaking switching element 42 is forcibly turned on and after a predetermined time has elapsed, the off-holding switching element 62 is switched to the on state, and this state is subjected to fail-safe processing. It may be held throughout.

  For example, if the configuration is such that the input of the operation signal g * # of all the switching elements S * # is an OFF operation command by the output of the fail signal FL as in the first embodiment, the three-state buffer 38 is omitted. Also, the input of the operation signal g * # is cut off.

"About switching elements to be driven"
The switching element to be driven is not limited to the IGBT but may be a power MOS field effect transistor, for example. At this time, not only the N channel but also the P channel may be used. However, in this case, since the gate potential is lowered with respect to the source potential, the on-state is turned on. Therefore, the driving target switching element is turned on by charging the gate with “negative” charge.

"others"
The motor generator 10 is not limited to the in-vehicle main unit, but may be a generator mounted on a series hybrid vehicle, for example.

  22 ... Power supply (one embodiment of DC voltage source), 26 ... Constant current switching element, 28 ... Gate resistor (one embodiment of limiting resistor), S * # ... Switching element.

Claims (15)

When a voltage-controlled switching element is used as a driving target switching element, and a process for charging either the positive or negative charge to the switching control terminal in order to switch the switching state of the driving target switching element, In the drive circuit of the switching element that limits the charge rate of the charge by the body,
Detecting means for detecting a current flowing through the limiting resistor;
A switching element drive circuit comprising: a determination unit that determines whether there is an abnormality in a function of driving the drive target switching element based on the current detected by the detection unit.   2. The switching element drive circuit according to claim 1, wherein the detection means includes a differential amplifier circuit connected to both ends of the limiting resistor and detecting a potential difference between the both ends.   The limiting resistor is shared by both a charging path for charging the other charge to the open / close control terminal and a discharge path for discharging the other charge from the open / close control terminal. 3. The switching element drive circuit according to claim 1, wherein the drive circuit is a switching element drive circuit.   The constant current control means which controls the electric current in the charge path | route to the constant value when charging the said other charge to the switching control terminal of the said drive object switching element is characterized by the above-mentioned. Switching element drive circuit. The constant current control means includes
A constant current resistor provided in the charging path separately from the limiting resistor,
A constant current switching element connected in series to the constant current resistor;
Operating means for operating the switching control terminal of the constant current switching element so that the voltage drop amount of the constant current resistor becomes a target value;
The switching element drive circuit according to claim 4, further comprising: The constant current control means uses a DC voltage source that supplies the other charge to the open / close control terminal of the drive target switching element, and opens and closes one end of the current flow path of the drive target switching element Charging one of the other charges until the voltage between the control terminals becomes the output voltage of the DC voltage source,
The output voltage of the DC voltage source is set to a voltage capable of performing the constant current control until the charging voltage of the switching control terminal having a saturation current that is the maximum current that normally flows through the drive target switching element. 6. The switching element drive circuit according to claim 5, wherein: A charging path for charging one of the other charges;
A charging switching element for opening and closing the charging path;
A discharge path for discharging one of the other charges;
A discharge switching element for opening and closing the discharge path;
The charging switching element, the discharging switching element, the detection means and the determination means are configured in an integrated circuit,
The charging switching element and the discharging switching element are connected to the open / close control terminal of the driving target switching element via different terminals of the integrated circuit,
The both ends of the limiting resistor are connected to the detection means via a pair of terminals of the integrated circuit connected to the charging switching element and the discharging switching element, respectively. Item 3. A driving circuit for a switching element according to Item 1 or 2.   When the current flowing through the limiting resistor exceeds a charging-side large current threshold during a period in which the other charge is charged to the switching control terminal of the driving target switching element, the determination unit switches the driving target switching 7. The switching element drive circuit according to claim 3, wherein it is determined that there is an abnormality in a function of driving the element.   When the current flowing through the limiting resistor is less than a charging side small current threshold during a period in which the other charge is charged to the switching control terminal of the driving target switching element, 9. The switching element drive circuit according to claim 3, wherein it is determined that the function of driving the switching element is abnormal.   When the current flowing through the limiting resistor exceeds the discharge-side large current threshold during the period in which the other charge is discharged from the switching control terminal of the driving target switching element, the determination unit switches the driving target switching. The switching element drive circuit according to claim 3, wherein an abnormality is determined in a function of driving the element.   When the current flowing through the limiting resistor is less than the discharge-side small current threshold during the period in which the other charge is discharged from the switching control terminal of the driving target switching element, The switching element drive circuit according to any one of claims 3 to 10, wherein it is determined that there is an abnormality in a function of driving the switching element. The discharge path includes a discharge switching element connected in series between the one end of the current flow path of the switching element to be driven and the open / close control terminal and connected in series to the limiting resistor. Configured,
A low resistance path that connects one end of the current flow path of the switching element to be driven and the open / close control terminal with a path having a smaller resistance value than the discharge path;
An off-holding switching element for opening and closing the low-resistance path;
The fail-safe means for turning on the off-holding switching element when the judgment means judges that there is an abnormality in the function of driving the drive target switching element. The drive circuit of the switching element of any one of Claims 1. The discharge path includes a discharge switching element connected in series between the one end of the current flow path of the switching element to be driven and the open / close control terminal and connected in series to the limiting resistor. Configured,
A high resistance path that connects between one end of the current flow path of the switching element to be driven and the open / close control terminal via a path having a resistance value larger than that of the discharge path;
A switching element for soft cutoff that opens and closes the high-resistance path;
The fail-safe means for turning on the soft shut-off switching element when the determination means determines that there is an abnormality in the function of driving the drive target switching element. The drive circuit of the switching element of any one of Claims 1.   When the determination means determines that there is an abnormality in the function of driving the drive target switching element, the determination means further comprises a blocking means for blocking input of an on / off command signal of the drive target switching element. Item 14. The switching element drive circuit according to any one of Items 1 to 13.   15. The information processing apparatus according to claim 1, further comprising notification means for notifying the outside when the determination means determines that there is an abnormality in the function of driving the switching element to be driven. A switching element driving circuit according to claim 1.

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