JP2012191724A - Switching element driving circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide means for, when a pair of switching elements S*#a and S*#b are driven with the same driving signal, if an abnormality occurs to the driving, swiftly detecting a resultant situation where a deviation between temperatures of the switching elements increases.SOLUTION: Output voltages of temperature-sensitive diodes SDa and SDb that detect temperatures of switching element S*#a and S*#b are applied to terminals T6a and T6b. An electric potential difference between the terminals T6a and T6b is taken into a window comparator 52 through a differential amplifier circuit 50. At the window comparator 52, when the difference is large, it is determined that there occurs an abnormality.

Description

  The present invention relates to a switching element drive circuit that includes state detection means for detecting the states of a plurality of drive target switching elements, and drives the plurality of drive target switching elements with a single drive signal.

  In recent years, in power conversion circuits such as in-vehicle inverters, it has been proposed to double the amount of current that can be handled by providing a plurality of switching elements in parallel (para-connection) because of handling large currents. Has been put to practical use (Patent Document 1).

JP-A-10-243660

  As described above, when driving with a plurality of switching elements connected in parallel, if the driving is normal, it is considered that the same current flows through each of the switching elements connected in parallel and the temperature is substantially the same. When it occurs, it is considered that there is a difference in current and temperature. However, the state detection means for detecting the state of each of the plurality of switching elements is conventionally used to detect whether or not an abnormality that causes a decrease in reliability occurs in one target driving switching element. Therefore, the abnormalities peculiar to the paraconnection as described above cannot be detected quickly.

  The present invention has been made in the process of solving the above-mentioned problems, and its purpose is to change the state of each of the plurality of drive target switching elements when the plurality of drive target switching elements are driven by a single drive signal. It is an object of the present invention to provide a new switching element driving circuit including state detecting means for detecting.

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

  The invention according to claim 1 is provided with a state detecting means for detecting the respective states of the plurality of drive target switching elements, and the switching element drive circuit drives the plurality of drive target switching elements with a single drive signal. , It is determined that an abnormality has occurred in driving the switching target switching element based on a large degree of divergence between the detection results of the states by the state detecting means corresponding to at least two of the plurality of switching target switching elements. An abnormality determining means is provided.

  When the drive target switching element is driven based on a single drive signal, if the drive is normal, it is considered that the states of the plurality of drive target switching elements also approximate each other. In the above invention, in view of this point, it is determined that there is an abnormality when the degree of deviation between the detection results of the states is large.

  According to a second aspect of the present invention, in the first aspect of the invention, the detection result includes a detection result of a temperature of the drive target switching element, and the abnormality determination unit detects the temperature corresponding to the at least two. It is determined that the abnormality has occurred based on a large degree of divergence between results.

  If the switching elements to be driven are not driven identically, a temperature difference may occur between them. For this reason, when the degree of deviation between the temperature detection results is large, it can be determined that an abnormality in which the driving states are not aligned between the switching elements to be driven has occurred.

  According to a third aspect of the present invention, in the second aspect of the present invention, the abnormality determining means determines the threshold of the degree of divergence for determining that the abnormality has occurred according to the amount of current flowing through the driving target switching element. A variable means for variably setting is provided.

  Due to individual differences of driving target switching elements, differences in arrangement environment, and the like, temperature deviation may occur even if driving is normal. The temperature shift is considered to increase as the current flowing through the drive switching element increases. This is because the temperature of the drive target switching element increases as the current increases. In the above invention, in view of this point, the threshold value is variably set.

  According to a fourth aspect of the present invention, in the invention according to the second or third aspect, the driving target switching element is a voltage-controlled switching element, and the abnormality determining unit determines that the abnormality has occurred. The threshold of the degree of divergence is variable in accordance with at least one of a pair of ends of the current flow path of the switching element to be driven and the capacitance between the switching control terminals and the voltage value applied to the switching control terminal. It is characterized by comprising operable operation means.

  If the switching elements to be driven are not driven identically, a temperature difference may occur between them. For this reason, when the degree of deviation between the temperature detection results is large, it can be determined that an abnormality in which the driving states are not aligned between the switching elements to be driven has occurred. However, due to individual differences of driving target switching elements, differences in arrangement environment, and the like, temperature deviation may occur even when driving is normal. The temperature difference differs depending on the capacitance of the switching element to be driven and the voltage applied to the switching control terminal. In the above invention, in view of this point, the threshold value can be variably operated.

  According to a fifth aspect of the present invention, in the invention according to any one of the second to fourth aspects, the state detection unit includes a temperature-sensitive diode that detects a temperature in the vicinity of the drive target switching element, and the abnormality determination. The means is characterized by determining the presence or absence of the abnormality based on a degree of deviation between the output voltages corresponding to the at least two of the temperature sensitive diodes as the detection result.

  According to a sixth aspect of the present invention, in the invention according to any one of the second to fourth aspects, the driving target switching element is a voltage-controlled switching element, and the state detection means is the driving target switching. A voltage detection means for detecting a voltage between one of a pair of ends of the current flow path of the element and the switching control terminal; and a current detection means for detecting a current flowing through the drive target switching element, the abnormality The determination means is a value between the values corresponding to the at least two of the voltages detected by the voltage detection means when it is determined that a current starts to flow through the drive switching element based on the detection value of the current detection means. The presence or absence of the abnormality is judged based on the difference.

  The threshold voltage, which is a voltage between any one of the above and the switching control terminal when current starts to flow through the drive target switching element, changes according to the temperature of the drive target switching element. For this reason, the temperature can be detected by detecting the threshold voltage.

  The invention according to claim 7 is the invention according to any one of claims 2 to 4, wherein the state detection means includes current detection means for detecting a current flowing through the drive target switching element, and the abnormality determination is performed. The means determines the presence or absence of the abnormality based on a waveform detected by the current detection means with respect to a current flowing through the drive switching element.

  The threshold voltage of the drive target switching element changes depending on the temperature. For this reason, if the temperature is different between the switching elements to be driven, the timing at which the current starts to flow may be different even if the switching is turned on by the same drive signal. In the above invention, in view of this point, the temperature is detected based on the waveform of the current.

  The invention according to claim 8 is the invention according to claim 1, wherein the state detection means includes current detection means for detecting a current flowing through the drive target switching element, and the abnormality determination means includes at least two of the abnormality determination means. It is determined that an abnormality has occurred in driving the switching element to be driven based on a large degree of deviation between the values detected by the corresponding current detection means.

  When the switching elements to be driven are not driven identically, the currents flowing through them may be different. In the above invention, in view of this point, the presence or absence of abnormality is determined.

  According to a ninth aspect of the present invention, in the first aspect of the invention, the driving target switching element is a voltage-controlled switching element, and the state detection means is a pair of current flow paths of the driving target switching element. A voltage detecting means for detecting a voltage between any one of the end portions and the switching control terminal, wherein the abnormality determining means is a degree of divergence between the voltages detected by the voltage detecting means corresponding to the at least two It is determined that an abnormality has occurred in driving the switching element to be driven on the basis of the large value.

  When the switching elements to be driven are not driven identically, the voltages at these open / close control terminals may be different. In the above invention, in view of this point, the presence or absence of abnormality is determined.

  According to a tenth aspect of the present invention, in the invention according to the eighth or ninth aspect, the abnormality determination means sets the threshold of the degree of deviation for determining that the abnormality has occurred to an amount of current flowing through the drive target switching element. A variable means for variably setting according to this is provided.

  Even when the switching element to be driven is driven normally, a deviation may occur in the amount of current flowing through them and the voltage at the open / close control terminal due to these individual differences. The amount of current deviation is considered to increase as the amount of current increases. In addition, the voltage at the open / close control terminal before passing the mirror period changes in accordance with the amount of current flowing through the drive target switching element. In the above invention, in view of this point, variable setting according to the amount of current is performed.

  The invention described in claim 11 is the invention described in any one of claims 8-10, wherein the switching element to be driven is a voltage control type switching element, and the abnormality determination means generates the abnormality. The threshold of the degree of divergence for determining whether or not the difference between a capacitance between one of a pair of ends of the current flow path of the switching element to be driven and the switching control terminal and a voltage value applied to the switching control terminal An operation means that can be variably operated according to at least one of them is provided.

  Even when the switching element to be driven is driven normally, a deviation may occur in the amount of current flowing through them and the voltage at the open / close control terminal due to these individual differences. These deviation amounts are considered to change according to the magnitude of the applied voltage value and the capacitance. In view of this point, the above invention enables variable operation.

  A twelfth aspect of the invention is the invention according to any one of the first to eleventh aspects, wherein when the abnormality determination means determines that there is an abnormality, the restriction means restricts driving of the drive target switching element. Is further provided.

  In the said invention, it can suppress suitably that an abnormal condition deteriorates by carrying out drive restriction at the time of abnormality.

  A thirteenth aspect of the present invention is the information processing apparatus according to any one of the first to twelfth aspects of the present invention, further comprising notifying means for notifying the outside when the abnormality determining means determines that there is an abnormality. It is characterized by that.

  In the said invention, an abnormal condition can be grasped | ascertained by providing a notification means.

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 circuit diagram which shows the circuit structure of the drive unit concerning 2nd Embodiment. The circuit diagram which shows the circuit structure of the drive unit concerning 3rd Embodiment. The flowchart which shows the procedure of the abnormality diagnosis process concerning the embodiment. The flowchart which shows the procedure of the abnormality diagnosis process concerning 4th Embodiment. The flowchart which shows the procedure of the abnormality diagnosis process concerning 5th Embodiment. The flowchart which shows the procedure of the abnormality diagnosis process concerning 6th 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). The motor generator 10 is connected to a high voltage battery 12 having a terminal voltage of, for example, 100 V or more and a capacitor C through an inverter INV. The inverter INV includes a pair of series connections of a series connection of switching elements S * pa and S * na (* = u, v, w) and a series connection of switching elements S * pb and S * b. Each of the pairs is connected to the U, V, and W phases of the motor generator 10. In the present embodiment, insulated gate bipolar transistors (IGBTs) are used as the switching elements S * # a, S * # b (* = u, v, w; # = p, n). In addition, diodes D * # a and D * # b are respectively connected in antiparallel to these.

  The control device 18 is a control device that uses the low-voltage battery 16 as a power source. The control device 18 operates the inverter INV in order to control the motor generator 10 as a control target and to control the control amount as desired. Specifically, operation signals g * p and g * n are output to the drive unit DU in order to operate the switching elements S * pa, S * Pb, S * na, and S * nb of the inverter INV. 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 elements S * pa and S * pb and the corresponding low-potential side switching elements S * na and S * nb are alternately turned on.

  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 / reception of signals between them includes an interface 14 including an insulating element such as a photocoupler. Done through.

  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 DC voltage source 22 having a terminal voltage VH, which is connected to a terminal T3 via a terminal T1, a constant current resistor 24, a terminal T2, and a P-channel MOS field effect transistor (constant current switching element 26). It is connected. The gates of the switching elements S * # a and S * # b are connected to the terminal T3 via the gate resistor 28.

  On the other hand, the terminal T3 is connected to the terminal T4 through the discharging switching element 30. The terminal T4 is connected to one (emitter) of a pair of ends of the current flow path of the switching elements S * # a and S * # b.

  The constant current switching element 26 and the discharging switching element 30 are operated by a drive control unit 32 in the drive IC 20. That is, the drive control unit 32 alternately turns on and off the constant current switching element 26 and the discharge switching element 30 based on the operation signal g * # input via the terminal T5, thereby switching the switching element S. * # A and S * # b are driven. Specifically, when the operation signal g * # is an on operation command, the discharge switching element 30 is turned off and the constant current switching element 26 is turned on. On the other hand, when the operation signal g * # is an off operation command, the constant current switching element 26 is turned off and the discharge switching element 30 is turned on.

  Here, during a period during which the constant current switching element 26 is turned on, the voltage applied to the open / close control terminal (gate) is the voltage drop amount of the constant current resistor 24 (voltage Vm between the terminals T1 and T2). To control to the specified value. Thereby, the amount of current flowing through the constant current resistor 24 can be set as a target value, and the gate charging process of the switching elements S * # a and S * # b can be performed by constant current control. According to the constant current control using the constant current switching element 26, the gate voltages of the switching elements S * # a and S * # b converge to the terminal voltage VH. When the gate voltage approaches the convergence value, the controllability of constant current control is degraded. This is because the terminal voltage VH represents the voltage drop amount of the constant current resistor 24 and the gate resistor 28 and the minimum value of the voltage drop amount of the constant current switching element 26 when the target voltage of the gate voltage Vge flows. This is because the voltage drop amount of the constant current resistor 24 cannot be controlled to a specified value depending on the operation of the gate voltage of the constant current switching element 26 when the value becomes equal to or larger than the value subtracted from the above. For this reason, the terminal voltage VH does not reach the gate voltage in which the maximum value of the current flowing through the switching elements S * # a and S * # b is the saturation current when the switching elements S * # a and S * # b are normally driven. The constant current controllability is set to a value that does not deteriorate.

  A temperature sensitive diode SDa for detecting the temperature of the switching element S * # a is disposed in the vicinity of the switching element S * # a. A constant current source 42a having a DC voltage source 40a as a power source is connected to the anode of the temperature sensitive diode SDa through a terminal T6a. On the other hand, a temperature sensitive diode SDb for detecting the temperature of the switching element S * # b is arranged in the vicinity of the switching element S * # b. A constant current source 42b having a DC voltage source 40b as a power source is connected to the anode of the temperature sensitive diode SDb via a terminal T6b.

  The voltage at the terminal T6a is connected to the inverting input terminal of the comparator 44a, and the reference voltage Vref of the reference power supply 46 is applied to the non-inverting input terminal of the comparator 44a. As a result, the output of the comparator 44a is inverted to logic “H” when the temperature detected by the temperature sensitive diode SDa is equal to or higher than the threshold temperature. Incidentally, the reason why the anode of the temperature sensitive diode SDa is connected to the inverting input terminal of the comparator 44a is that there is a negative correlation between the anode voltage of the temperature sensitive diode SDa and the temperature.

  Similarly, the voltage at the terminal T6b is connected to the inverting input terminal of the comparator 44b, and the reference voltage Vref of the reference power supply 46 is applied to the non-inverting input terminal of the comparator 44b. As a result, the output of the comparator 44b is inverted to logic “H” when the temperature detected by the temperature sensitive diode SDb is equal to or higher than the threshold temperature.

  When at least one of the comparators 44 a and 44 b is inverted to logic “H”, a fail signal FL (logic “H” signal) is output to the drive control unit 32 via the OR circuit 58. As a result, the drive control unit 32 stops driving the constant current switching element 26 and the discharge switching element 30. The fail signal FL is also output to the low voltage system (control device 18) via the terminal T7. Furthermore, the fail signal FL shuts down the inverter INV 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.

  In the present embodiment, in addition to the process of determining that an abnormality has occurred in the driving of the switching elements S * # a and S * # b when the temperature of the switching elements S * # a and S * # b is equal to or higher than the threshold temperature. Thus, a process for determining whether there is an abnormality in which the states of the switching elements S * # a and S * # b deviate from each other is also performed. That is, the pair of switching elements S * # a and S * # b are driven by the same operation signal g * #. More specifically, it is charged by the charge output through the common terminal T3, and the gate charge is extracted through the common terminal T3. For this reason, it is considered that the state of the pair of switching elements S * # a and S * # b is equal to each other if these drive states are normal. For this reason, the presence or absence of drive abnormality can be determined based on the difference in state.

  Specifically, in this embodiment, temperature is adopted as a state that is a target for determining the degree of deviation. This is considered that when the driving states of the pair of switching elements are not the same, such as the currents flowing through the pair of switching elements S * # a and S * # b are different, these temperatures are different. In view of that.

  Specifically, the potential difference between the terminals T6a and T6b is converted into a predetermined value by the differential amplifier circuit 50, and then the converted analog voltage signal is taken into the window comparator 52. The window comparator 52 receives the determination voltage VthL (<0) of the determination power supply 54 and the determination voltage VthH (> 0) of the determination power supply 56. Thus, the window comparator 52 outputs a logic “H” signal to the OR circuit 58 when the output voltage of the differential amplifier circuit 50 is not between the determination voltage VthL and the determination voltage VthH. Note that the window comparator 52 can be configured to include a pair of comparators, for example.

  According to such a configuration, when the degree of deviation between the temperature of the switching element S * # a detected by the temperature sensitive diode SDa and the temperature of the switching element S * # b detected by the temperature sensitive diode SDb is large, the window The comparator 52 outputs a signal indicating abnormality (logic “H” signal). Here, the pair of determination voltages VthL and VthH is used because it is determined that the difference between the pair of output voltages is large regardless of which output voltage of the temperature sensitive diodes SDa and SDb is high. It is to do.

  Further, in the present embodiment, the determination voltages VthL and VthH are variably set according to the current flowing through the switching elements S * # a and S * # b. This is because the higher the current flowing through the pair of switching elements S * # a and S * # b, the higher their temperature tends to increase, and the higher the current, the greater the variation in these temperatures during normal operation. Because. Specifically, in this embodiment, the determination voltages VthL and VthH are variably set according to the current flowing through the switching element S * # a. That is, the switching element S * # a includes a sense terminal St that outputs a minute current having a correlation with a current flowing therethrough, and the sense terminal St is connected to the emitter via the resistors 60a and 62a. . Then, the voltage drop amount of the resistor 62a (voltage between the resistors 60a and 62a) is taken into the determination power sources 54 and 56 via the terminal T8. The determination power sources 54 and 56 variably set the determination voltages VthL and VthH according to the voltage at the terminal T8. Specifically, the higher the voltage at the terminal T8, the wider the interval between the pair of determination voltages VthL and VthH.

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

  (1) When the degree of deviation between the temperature detection results of the pair of switching elements S * # a and S * # b is large, the drive of the pair of switching elements S * # a and S * # b is abnormal. It was judged. This makes it possible to determine whether or not an abnormality has occurred in which the driving state does not match between the pair of switching elements S * # a and S * # b.

  (2) A threshold (determination voltage VthL, VthH) of a temperature divergence degree between the pair of switching elements S * # a and S * # b is set according to the amount of current flowing through the switching elements S * # a and S * # b. Variable setting. Thereby, the presence or absence of abnormality can be determined with higher accuracy. That is, since the temperature tends to increase as the amount of current increases, the temperature variation increases even during normal operation. Here, in the case where the threshold is set based on when the amount of current is large, it is difficult to detect an abnormality when the amount of current is small. Further, when the threshold value is set based on when the amount of current is small, there is a possibility that it is erroneously determined that it is abnormal although it is normal when the amount of current is large.

  (3) When there is an abnormality in which the temperature difference between the pair of switching elements S * # a and S * # b is large, the driving of the pair of switching elements S * # a and S * # b is stopped. Thereby, it can suppress suitably that an abnormal condition worsens.

(4) When there is an abnormality in which the degree of temperature deviation between the pair of switching elements S * # a and S * # b is large, the controller 18 is notified of this. Thereby, an abnormal situation can be grasped.
<Second Embodiment>
Hereinafter, the second embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  In the present embodiment, the determination voltages VthL and VthH are variably set according to the specifications of the switching elements S * # a and S * # b and the specifications of the drive unit DU. Specifically, it is variably set according to the gate-emitter capacitances of the switching elements S * # a and S * # b and the gate applied voltage (voltage VH of the DC voltage source 22). Here, the gate-emitter capacitances of the switching elements S * # a, S * # b are parameters that determine the on-resistance (collector-emitter voltage) of the switching elements S * # a, S * # b. The gate applied voltage is also a parameter that determines the on-resistance (collector-emitter voltage) of the switching elements S * # a and S * # b. For this reason, even if the currents flowing through the switching elements S * # a and S * # b are the same, these temperatures change according to the above parameters.

  FIG. 3 shows a circuit configuration of the drive unit DU according to the present embodiment. In FIG. 3, the same reference numerals are assigned for convenience to those corresponding to the members shown in FIG.

  As illustrated, the determination voltage VthL is generated by dividing the voltage of the power source 73 by the resistors 70 and 72. The resistor 72 is externally attached to the drive IC 20 via terminals T9 and T10. On the other hand, the determination voltage VthH is generated by dividing the voltage of the power supply 77 by the resistors 74 and 76. The resistor 74 is externally attached to the drive IC 20 via terminals T11 and T12.

  According to such a configuration, the determination voltages VthL and VthH can be varied by adjusting the resistance values of the resistors 72 and 76 in accordance with the specifications of the switching elements S * # a and S * # b connected to the drive IC 20. Can be set. Similarly, the determination voltages VthL and VthH are variably set by adjusting the resistance values of the resistors 72 and 76 in accordance with the gate applied voltage (the voltage VH of the DC voltage source 22 externally attached to the drive IC 20). can do.

  According to the present embodiment described above, the following effects can be obtained in addition to the effects (1), (3), and (4) of the first embodiment.

(5) The determination voltages VthL and VthH can be operated by adjusting the resistance values of the resistors 72 and 76 externally attached to the drive IC 20. Thereby, the determination voltages VthL and VthH can be variably set according to the specifications of the switching elements S * # a and S * # b and the gate application voltage.
<Third Embodiment>
Hereinafter, the third embodiment will be described with reference to the drawings with a focus on differences from the first embodiment.

  FIG. 4 shows a circuit configuration of the drive unit DU according to the present embodiment. In FIG. 4, components corresponding to those shown in FIG. 2 are given the same reference numerals for convenience.

  In the present embodiment, the terminal T4 is connected to the above-described terminal T3 of the drive IC 20 through a series connection body of the Zener diode 80 and the clamp switching element 82. Here, the breakdown voltage of the Zener diode 80 limits the gate voltage of the switching elements S * # and S * # b to such an extent that excessive current does not flow through the switching elements S * # a and S * # b. is there.

  The terminal T3 is further connected to a terminal T4 via a soft cutoff resistor 84 and a soft cutoff switching element 86.

  On the other hand, the sense terminal St of the switching element S * # a is electrically connected to the emitter via a series connection body of the resistors 60a and 62a, and the voltage drop amount (resistor 60a) due to the resistors 60a and 62a. , 62a is taken in by the non-inverting input terminal of the comparator 88a through the terminal T8a. On the other hand, the reference voltage Vref of the reference power supply 90 is applied to the inverting input terminal of the comparator 88a. Accordingly, when the collector current becomes equal to or higher than the overcurrent threshold Ith, the output signal of the comparator 88a is inverted from the logic “L” to the logic “H”.

  Similarly, the sense terminal St of the switching element S * # b is electrically connected to the emitter through a series connection body of the resistors 60b and 62b, and the voltage drop amount (resistor 60b) due to the resistors 60b and 62b. , 62b is taken into the non-inverting input terminal of the comparator 88b through the terminal T8b. On the other hand, the reference voltage Vref of the reference power supply 90 is applied to the inverting input terminal of the comparator 88b. Accordingly, when the collector current becomes equal to or higher than the overcurrent threshold Ith, the output signal of the comparator 88b is inverted from logic “L” to logic “H”.

  The logic “H” signals output from the comparators 88 a and 88 b are applied to the clamping switching element 82 via the OR circuit 92 and are taken into the delay 94. The delay 94 outputs the fail signal FL to the OR circuit 58 when the input signal becomes logic “H” for a predetermined time.

  According to such a configuration, when an overcurrent flows through the switching elements S * # and S * # b, the Zener diode 80 is first turned on when the clamping switching element 82 is turned on. The gate voltages of the elements S * # a and S * # b are lowered. Thereby, the electric current which flows through switching element S * # a, S * # b can be restrict | limited. After that, when the overcurrent continues for a predetermined time, the switching element 86 for soft cutoff is turned on, so that the switching elements S * # a and S * # b are forcibly turned off.

  As a result, the state in which the collector current is equal to or higher than the overcurrent threshold Ith continues for a predetermined time or longer, so that the soft cutoff switching element 86 is turned on, and switching is performed via the soft cutoff resistor 84 and the gate resistor 28. The charges on the gates of the elements S * # a and S * # are discharged. Here, the soft blocking resistor 84 is used to increase the resistance value of the discharge path. This is because, under a situation where the collector current is excessive, the switching element S * # a, S * # b is switched from the on state to the off state, in other words, the cutoff speed between the collector and the emitter is increased. As a result, the surge may become excessive. Therefore, under a situation where the collector current is determined to be equal to or greater than the overcurrent threshold Ith, the switching element S * # is connected by a path having a resistance value larger than that of the discharge path including the gate resistor 28 and the discharge switching element 30. The gates of a and S * # b are discharged.

  In the present embodiment, the clamp voltage generated by the clamp circuit including the clamp switching element 82 and the Zener diode 80, and the current flowing through the switching elements S * # a and S * # b are specified values (≧ overcurrent threshold Ith). Set the value to the following limit.

  Here, in the present embodiment, in addition to determining whether or not an excessively large current flows through the switching elements S * # a and S * # b, the pair of switching elements S * # a and S * # b It is also determined whether the temperature deviation degree is large. The temperatures of the pair of switching elements S * # a and S * # b are indirectly detected based on the gate voltages Vge and Vgeb and the currents (voltages Vsda and Vsdb) flowing therethrough.

  Specifically, the abnormality determination unit 95 takes in the gate voltages Vgea and Vgeb of the switching elements S * # a and S * # b via the terminals T13a and T13b in addition to the voltages Vsda and Vsdb of the terminals T8a and T8b.

  FIG. 5 shows a procedure for determining whether there is an abnormality according to the present embodiment. This process is repeatedly executed in the abnormality determination unit 95, for example, at a predetermined cycle.

  In this series of processes, first, in step S10, it is determined whether or not it is time to switch the operation signal g * # from the OFF operation command to the ON operation command. When an affirmative determination is made in step S10, in step S12, processing is performed to acquire voltages (threshold voltages Vtha and Vthb) at which the switching elements S * # a and S * # b are turned on. Here, the threshold voltage Vtha is the gate voltage Vgea when the current starts to flow through the switching element S * # a (when the voltage Vsda becomes equal to or higher than the predetermined value ΔV), and the threshold voltage Vthb is the switching element S *. This is the gate voltage Vgeb when current starts to flow through #b (when the voltage Vsdb becomes equal to or higher than the predetermined value ΔV).

  In the subsequent step S14, it is determined whether or not the absolute value of the difference between the threshold voltages Vtha and Vthb is equal to or higher than the determination voltage Δth. In view of the fact that there is a correlation between the temperature of the switching element and the threshold voltage, this process determines whether or not the degree of deviation between the temperatures of the switching elements S * # a and S * # b is large. is there. Here, determination voltage ΔVth is variably set according to the current (voltage Vsda) flowing through switching element S * # a. In practice, the determination voltage ΔVth is variably set depending on the specifications of the switching elements S * # a and S * # b, the gate application voltage, and the like. This is performed by variably operating the voltage signal applied to the abnormality determination unit 95 according to the resistance value of the resistor 100 as shown in FIG. That is, the abnormality determination unit 95 is applied with the voltage of the DC voltage source 98 divided by the resistors 99 and 100. Since the resistor 100 is externally attached to the drive IC 20 via the terminals T14 and T15, the voltage dividing value applied to the abnormality determining unit 95 can be variably operated.

  If an affirmative determination is made in step S14 of FIG. 5, the fail signal FL is output in step S16.

  When the process of step S16 is completed or when a negative determination is made in steps S10 and S14, the series of processes is temporarily ended.

Also according to the present embodiment described above, an effect according to the first embodiment can be obtained.
<Fourth Embodiment>
Hereinafter, the fourth embodiment will be described with reference to the drawings with a focus on differences from the third embodiment.

  FIG. 6 shows a procedure for determining whether there is an abnormality according to the present embodiment. This process is repeatedly executed in the abnormality determination unit 95, for example, at a predetermined cycle.

  In this series of processes, first, in step S20, it is determined whether or not it is time to switch the operation signal g * # from the OFF operation command to the ON operation command. If the determination in step S20 is affirmative, in step S22, the timer T starts to count the time required for the current to start flowing through the switching elements S * # a and S * # b. In the following step S24, a time Ta required for the current to start flowing through the switching element S * # a (time required for the voltage Vsda to become equal to or greater than the predetermined value ΔV), and a current flowing through the switching element S * # b. A time Tb required until the flow starts (a time required until the voltage Vsdb becomes equal to or higher than the predetermined value ΔV) is acquired.

  In a succeeding step S26, it is determined whether or not the absolute value of the difference between the time Ta and the time Tb is equal to or longer than a specified time ΔT. In view of the fact that this process has a correlation between the temperature of the switching element and the threshold voltage, it is determined whether or not the degree of deviation between the temperatures of the switching elements S * # a and S * # b is large. Is. Here, the specified time ΔT is variably set according to the current (voltage Vsda) flowing through the switching element S * # a. In practice, the specified time ΔT is variably set depending on the specifications of the switching elements S * # a and S * # b, the gate applied voltage, and the like.

  If an affirmative determination is made in step S26, a fail signal FL is output in step S28. When the process of step S28 is completed or when a negative determination is made in steps S20 and S26, this series of processes is temporarily terminated.

Also according to the present embodiment described above, an effect according to the first embodiment can be obtained.
<Fifth Embodiment>
Hereinafter, the fifth embodiment will be described with reference to the drawings with a focus on differences from the third embodiment.

  FIG. 7 shows a procedure for determining whether there is an abnormality according to the present embodiment. This process is repeatedly executed in the abnormality determination unit 95, for example, at a predetermined cycle.

  In this series of processes, first, in step S30, it is determined whether or not it is time to switch the operation signal g * # from the OFF operation command to the ON operation command. If the determination in step S30 is affirmative, in step S32, the timer T starts a time measuring operation for measuring the time from the switching timing to the ON operation command. In a succeeding step S34, it is determined whether or not the value of the timer T is equal to or longer than a specified time Tth. Here, the specified time Tth is set to a time shorter than the gate voltage is assumed to be the voltage VH of the DC voltage source 22. More specifically, the time is assumed to be in the mirror period.

  If an affirmative determination is made in step S34, whether or not the absolute value of the difference between the gate voltage Vgea of the switching element S * # a and the gate voltage Vgeb of the switching element S * # b is greater than or equal to the determination voltage ΔVge in step S36. Judging. This process is for determining whether there is an abnormality in which the driving states of the pair of switching elements S * # a and S * # b are different. Here, as the factors that cause the gate voltage to differ in the period that is assumed to be the mirror period, there may be a large variation in the capacitance between the gate and the emitter, a difference in the gate charging speed, and the like. Note that the variation in the capacitance between the gate and the emitter is considered to be caused by temperature variation. The determination voltage ΔVge is variably set according to the specifications of the switching elements S * # a and S * # b, the gate application voltage, and the like.

  If an affirmative determination is made in step S36, a fail signal FL is output in step S38. When the process of step S38 is completed or when a negative determination is made in steps S30 and S36, this series of processes is temporarily terminated.

Also according to the present embodiment described above, an effect according to the first embodiment can be obtained.
<Sixth Embodiment>
Hereinafter, the sixth embodiment will be described with reference to the drawings with a focus on differences from the third embodiment.

  FIG. 8 shows a procedure for determining whether there is an abnormality according to the present embodiment. This process is repeatedly executed in the abnormality determination unit 95, for example, at a predetermined cycle.

  In this series of processes, first, in step S40, it is determined whether or not it is time to switch the operation signal g * # from the OFF operation command to the ON operation command. If an affirmative determination is made in step S40, whether or not the absolute value of the difference between the voltage Vsda applied to the terminal T8a in FIG. 4 and the voltage Vsdb applied to the terminal T8b is equal to or greater than the determination voltage ΔVsd in step S42 Determine whether. This process is for determining whether there is an abnormality in which the driving states of the pair of switching elements S * # a and S * # b are different. The determination voltage ΔVsd is variably set according to the specifications of the switching elements S * # a and S * # b, the gate application voltage, and the like.

  If an affirmative determination is made in step S42, a fail signal FL is output in step S44. When the process of step S44 is completed or when a negative determination is made in steps S40 and S42, this series of processes is temporarily terminated.

Also according to the present embodiment described above, an effect according to the first embodiment can be obtained.
<Other embodiments>
Each of the above embodiments may be modified as follows.

"Current as an input parameter of variable means"
The voltage Vsdb is not limited to the voltage Vsda. Further, it may be a voltage between a pair of ends of the current flow path of the switching element S * # (collector-emitter voltage). Furthermore, a signal corresponding to the command current for the motor generator 10 may be taken from the control device 18 and used.

"About operation means"
The operation means is not limited to the one in which the threshold value is variably operated according to the resistance value of the external resistor. For example, one of the pair of input terminals is pulled down and the other is pulled up, and one of them is pulled down. The threshold value may be variably operated internally depending on whether or not to do so.

“How to use gate voltage in abnormality judgment processing”
It is not limited to the determination of the presence or absence of an abnormality based on the degree of deviation between voltages at the timing assumed to be the mirror period. For example, it is determined that there is an abnormality in which the temperature difference between the switching elements S * # a and S * # b is large based on the large degree of deviation between the time until the detected value of the gate voltage reaches the threshold voltage Vth. May be.

"About state detection means"
The current detecting means is not limited to detecting the voltages Vsda and Vsdb, and for example, detects a voltage between a pair of ends of the current flow path of the switching element S * # (collector-emitter voltage). May be.

"Restriction measures"
The charging switching element (constant current switching element 26) is forcibly turned off and the discharging switching element 30 is forcibly turned on in an abnormal state where the driving states of the switching elements S * # a and S * # b are different. And means for shutting down the inverter INV using the fail signal FL. For example, even when the driving states of the switching elements S * # a and S * # b are different, even if the switching element S * # is forcibly turned off using the soft cutoff switching element 86. Good.

"Notification"
The notification means for notifying the abnormality related to the breaking of the symmetry of the driving state is not limited to the one that outputs the fail signal FL to the control device 18. For example, a signal different from a signal indicating an abnormality in which the temperature detected by the temperature sensitive diode SD is excessively large or an abnormality in which the current flowing through the switching element S * # is excessively large is output to the control device 18. Also good. In this case, the control device 18 can take measures different from the case where an abnormality in which the temperature flowing through the switching element S * # is excessively large occurs. For example, in the case where an abnormality relating to the breaking of symmetry of the driving state occurs, the operation is performed in a state where the absolute value of the torque (current) of the motor generator 10 is controlled to a value larger than zero and is limited. Can be realized.

“About the number of driving target switching elements driven by one integrated circuit”
The number of cases is not limited to one or two but may be three or more. In this case, the degree of deviation can be determined based on the difference between the average value of each state and each state without directly comparing the two states.

"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 potential of the switching control terminal (gate potential) is lowered with respect to the potential (source potential) of one of the pair of ends of the current flow path, the gate is turned on. By charging the “negative” charge, the switching element to be driven is turned on.

"others"
The process for switching the drive target switching element S * # to the ON state is not limited to the constant current process, and for example, the voltage of the DC voltage source 22 may be constantly applied via a gate resistor.

  The switching process of the drive target switching element S * # to the off state may be performed by constant current control.

  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.

  50 ... differential amplifier circuit, 52 ... window comparator, SDa, SDb ... temperature sensitive diode, 54, 56 ... power supply for determination.

Claims (13)

In a drive circuit for a switching element that includes state detection means for detecting the respective states of a plurality of drive target switching elements, and drives the plurality of drive target switching elements by a single drive signal,
An abnormality determination for determining that an abnormality has occurred in driving the driving target switching element, based on a large degree of deviation between the detection results of the states by the state detecting means corresponding to at least two of the plurality of driving target switching elements. A switching element drive circuit comprising: means. The detection result includes a detection result of the temperature of the drive target switching element,
2. The switching element drive according to claim 1, wherein the abnormality determination unit determines that the abnormality has occurred based on a large degree of deviation between detection results of temperatures corresponding to the at least two. circuit.   The said abnormality determination means is provided with the variable means which variably sets the threshold value of the said divergence degree for determining that the said abnormality has arisen according to the electric current amount which flows through the said drive object switching element. The switching element drive circuit. The driving target switching element is a voltage-controlled switching element,
The abnormality determination means sets the threshold value of the divergence degree for determining that the abnormality has occurred, the capacitance between one of a pair of ends of the current flow path of the drive target switching element and the switching control terminal, 4. The switching element drive circuit according to claim 2, further comprising operation means that can be variably operated according to at least one of a voltage value applied to the open / close control terminal. The state detection means includes a temperature sensitive diode that detects a temperature in the vicinity of the driving target switching element,
5. The abnormality determination unit according to claim 2, wherein the abnormality determination unit determines the presence or absence of the abnormality based on a degree of deviation between output voltages corresponding to the at least two of the temperature-sensitive diodes as the detection result. The drive circuit of the switching element of any one of Claims 1. The driving target switching element is a voltage-controlled switching element,
The state detecting means detects a voltage between one of a pair of ends of a current flow path of the driving target switching element and an open / close control terminal, and detects a current flowing through the driving target switching element. Current detecting means for
The abnormality determination means is a value corresponding to the at least two of the voltages detected by the voltage detection means when it is determined that a current starts to flow through the drive switching element based on the detection value of the current detection means. The switching element drive circuit according to claim 2, wherein the presence or absence of the abnormality is determined based on a difference between the switching elements. The state detection means includes a current detection means for detecting a current flowing through the drive target switching element,
The said abnormality determination means determines the presence or absence of the said abnormality based on the waveform detected by the said current detection means about the electric current which flows into the said drive object switching element, The any one of Claims 2-4 A switching element driving circuit according to claim 1. The state detection means includes a current detection means for detecting a current flowing through the drive target switching element,
The abnormality determining means determines that an abnormality has occurred in driving the drive target switching element based on a large degree of deviation between the values detected by the current detection means corresponding to the at least two. The switching element drive circuit according to claim 1. The driving target switching element is a voltage-controlled switching element,
The state detection means includes voltage detection means for detecting a voltage between any one of a pair of ends of a current flow path of the switching element to be driven and the open / close control terminal,
The abnormality determining means determines that an abnormality has occurred in driving the switching target switching element based on a large degree of deviation between the voltages detected by the voltage detecting means corresponding to the at least two. The drive circuit of the switching element according to claim 1.   9. The abnormality determination unit includes a variable unit configured to variably set a threshold value of the divergence degree for determining that the abnormality has occurred according to an amount of current flowing through the drive target switching element. A drive circuit for a switching element according to claim 9. The driving target switching element is a voltage-controlled switching element,
The abnormality determination means sets the threshold value of the divergence degree for determining that the abnormality has occurred, the capacitance between one of a pair of ends of the current flow path of the drive target switching element and the switching control terminal, 11. The switching element drive circuit according to claim 8, further comprising operation means that can be variably operated in accordance with at least one of a voltage value applied to the open / close control terminal.   The switching element according to claim 1, further comprising a limiting unit that limits driving of the drive target switching element when the abnormality determining unit determines that there is an abnormality. Driving circuit.   The switching element drive circuit according to claim 1, further comprising notification means for notifying the outside of the fact when the abnormality determination means determines that there is an abnormality.

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