JP6292585B2 - Short-circuit detection device and short-circuit detection method - Google Patents

Description

  The present invention relates to a short-circuit detection device and a short-circuit detection method, and more specifically, a vertical power transistor connected between a power source and a ground, a load connected between the power source and the power transistor, and a power transistor The present invention relates to a short-circuit detection device and a short-circuit detection method for detecting a short circuit between a power source and a power transistor in a power conversion device including a gate drive device that drives a gate.

  Conventionally, as this type of short-circuit detection device, in a power conversion device including an IGBT (Insulated Gate Bipolar Transistor) connected to a power source and a gate drive circuit that drives the gate of the IGBT, a short circuit between the power source and the IGBT is performed. What to detect is proposed (for example, refer nonpatent literature 1). In the IGBT, when the gate voltage is raised to turn on, the input capacitance to the gate increases near the voltage at which the current starts to flow through the IGBT due to the mirror capacitance when no short circuit occurs, and such an input when the short circuit occurs. Almost no change in capacity is seen. Therefore, when the short circuit occurs, the gate voltage rises more quickly than when the short circuit does not occur. In this device, based on such characteristics of the IGBT, the timing until reaching the threshold voltage higher than the voltage at which current starts to flow through the IGBT and lower than the voltage of the power supply is set as a threshold time in advance, and the timing at which the gate voltage reaches the threshold voltage. Is detected to be shorter than the threshold time, it is detected that a short circuit has occurred.

Rahul.s and two others, "A Discussion on IGBT Short-Circuit Behavior and Fault Protection Schemes", March 1995, IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS, VOL 31, NO.2, p.256-263.

  However, in the short-circuit detection device described above, the gate capacity of the IGBT varies depending on temperature, manufacturing variation, and the like. Therefore, if the threshold time for detecting a short-circuit is a constant value, for example, if the gate capacity increases, the short-circuit is short-circuited. Even if this occurs, the timing at which the gate voltage reaches the threshold voltage is delayed, and if the short circuit does not occur, it will be erroneously detected. Therefore, what can detect a short circuit more appropriately is desired.

  The main object of the short circuit detection device and the short circuit detection method of the present invention is to detect a short circuit between a power supply and a power transistor more appropriately.

  The short-circuit detection device of the present invention employs the following means in order to achieve the main object described above.

The short circuit detection device of the present invention is
A power conversion device comprising: a vertical power transistor connected between a power source and a ground; a load connected between the power source and the power transistor; and a gate driving device that drives a gate of the power transistor. A short-circuit detection device that detects a short circuit between the power source and the power transistor in the device,
A first reference time from a start timing at which the gate voltage of the power transistor is started to rise by the gate driving device to a first reference voltage lower than a predetermined voltage at which the gate voltage starts to flow through the power transistor. Threshold time generation means for generating a threshold time multiplied by a predetermined coefficient;
A reference time detecting means for detecting a second reference time from the start timing to a second reference voltage in which the gate voltage is higher than the predetermined voltage and lower than the voltage of the power supply;
When the second reference time is shorter than the threshold time, short-circuit detecting means for detecting that the short-circuit has occurred,
It is a summary to provide.

  In this short-circuit detection device of the present invention, the gate voltage becomes a first reference voltage lower than a predetermined voltage at which current starts to flow through the power transistor from the start timing when the gate drive device starts to raise the gate voltage of the vertical power transistor. Generating a threshold time obtained by multiplying the first reference time until the first reference time by a predetermined coefficient, and detecting a second reference time from the start timing to the second reference voltage where the gate voltage is higher than the predetermined voltage and lower than the power supply voltage; When the second reference time is shorter than the threshold time, it is detected that a short circuit has occurred. In a vertical power transistor, when there is no short circuit, the input capacitance of the gate increases near the predetermined voltage at which current starts to flow through the power transistor due to the mirror capacitance, and when the short circuit occurs, the input capacitance changes near the predetermined voltage. Can hardly be seen. For this reason, when the short circuit occurs, the gate voltage rises more quickly than when the short circuit does not occur, and the second reference time becomes shorter. Therefore, it is possible to detect that a short circuit has occurred when the second reference time is shorter than the threshold time. The first reference time from the start timing until the gate voltage reaches the first reference voltage changes according to manufacturing variations of the power transistors, temperature changes, and the like. Accordingly, the threshold time is generated by multiplying the first reference time by a predetermined coefficient, and the occurrence of a short circuit is detected using the threshold time thus generated, so that the power transistor can be manufactured regardless of manufacturing variations or temperature changes. Compared with the case where a short circuit is detected using the same threshold time, it is possible to detect that a short circuit has occurred more appropriately.

  In such a short-circuit detection device according to the present invention, the threshold time generation means includes a first constant current source for supplying a second current obtained by multiplying the first current by the predetermined coefficient, and a first constant current source connected to the first constant current source. And charging the first capacitor by the first constant current source at the start timing, and the first capacitor by the first constant current source when the gate voltage reaches the first reference voltage. And a first charge start / stop circuit for stopping the charging of the first capacitor, and a means for outputting the voltage of the first capacitor charged by the first constant current source by the first charge start / stop circuit as the threshold time. And the reference time detection means includes a second constant current source for supplying the first current, a second capacitor connected to the second constant current source, and the second constant current source at the start timing. First A second charging start / stop circuit that starts charging a capacitor and stops charging the second capacitor by the second constant current source when the gate voltage reaches the second reference voltage, and The second reference time is a means for outputting the voltage of the second capacitor charged by the second constant current source by the second charge start / stop circuit, and the short circuit detecting means is outputted as the second reference time. In addition, when the voltage of the second capacitor is lower than the voltage of the first capacitor output as the threshold time, it may be means for detecting that the short circuit has occurred. The first capacitor and the second capacitor have the same capacity, the first capacitor is charged with a second current obtained by multiplying the first current by a predetermined coefficient, and the second capacitor is charged with the first current. Therefore, since the voltage of the first capacitor rises by a predetermined coefficient times the voltage of the second capacitor with respect to time, the voltage of the first capacitor is output as the threshold time, and the voltage of the second capacitor is used as the second reference time. Is output, the short circuit can be detected using the voltage of the first capacitor and the voltage of the second capacitor. In this case, the first constant current source may include a current changing unit that changes the first current. If it carries out like this, the 2nd electric current at the time of charging a 1st capacitor | condenser can be changed by changing a 1st electric current, and the voltage of the 1st capacitor | condenser produced | generated as a threshold time can be changed. Thereby, it can detect that the short circuit has arisen more appropriately.

  Further, in the short circuit detection device of the present invention, the reference time detection means detects a decrease in the gate voltage when the gate voltage becomes equal to or lower than the second reference voltage after detecting the second reference time, The short-circuit detection means has the short circuit when a decrease in the gate voltage is detected within a predetermined time after the second reference time is detected even when the second reference time is shorter than the threshold time. The absence may be detected. Even when no short circuit occurs, the gate voltage may temporarily exceed the second reference voltage due to pulse noise or the like. In this case, since the gate time decreases within a predetermined time, even when the gate voltage exceeds the second reference voltage and the second reference time is detected, when a decrease in the gate voltage is detected within the predetermined time, By determining that no short circuit has occurred, erroneous detection of a short circuit can be suppressed. Here, the “predetermined time” may be a time during which pulse noise or the like occurs.

The short circuit detection method of the present invention
A power conversion device comprising: a vertical power transistor connected between a power source and a ground; a load connected between the power source and the power transistor; and a gate driving device that drives a gate of the power transistor. A short-circuit detection method for detecting a short-circuit between the power source and the power transistor in an apparatus,
A first reference time from a start timing at which the gate voltage of the power transistor is started to rise by the gate driving device to a first reference voltage lower than a predetermined voltage at which the gate voltage starts to flow through the power transistor. Generate a threshold time multiplied by a predetermined coefficient,
Detecting a second reference time from the start timing until the gate voltage reaches a second reference voltage higher than the predetermined voltage and lower than the voltage of the power source;
When the second reference time is shorter than the threshold time, it is detected that the short circuit has occurred.
This is the gist.

  In this short circuit detection method of the present invention, the gate voltage is set to a first reference voltage lower than a predetermined voltage at which the gate voltage starts to flow through the power transistor from the start timing when the gate voltage of the vertical power transistor is started to rise. Generating a threshold time obtained by multiplying the first reference time until the first reference time by a predetermined coefficient, and detecting a second reference time from the start timing to the second reference voltage where the gate voltage is higher than the predetermined voltage and lower than the power supply voltage; When the second reference time is shorter than the threshold time, it is detected that a short circuit has occurred. In a vertical power transistor, when a short circuit does not occur, the input capacitance of the gate increases near a predetermined voltage at which current starts to flow through the power transistor due to the mirror capacitance, and when a short circuit occurs, the input capacitance of the gate near the predetermined voltage occurs. Almost no change can be seen. For this reason, when a short circuit occurs, the gate voltage rises to the second reference voltage more quickly than when the short circuit does not occur, and the second reference time becomes shorter. Therefore, it is possible to detect that a short circuit has occurred when the second reference time is shorter than the threshold time. The first reference time from the start timing until the gate voltage reaches the first reference voltage changes according to manufacturing variations of the power transistors, temperature changes, and the like. Accordingly, the threshold time is generated by multiplying the first reference time by a predetermined coefficient, and the occurrence of a short circuit is detected using the threshold time thus generated, so that the power transistor can be manufactured regardless of manufacturing variations or temperature changes. Compared with the case where a short circuit is detected using the same threshold time, it is possible to detect that a short circuit has occurred more appropriately.

It is a block diagram which shows the outline of a structure of the power converter device 10 provided with the short circuit detection apparatus 20 as one Example of this invention. 3 is a circuit diagram illustrating an outline of a circuit configuration of a short circuit detection device 20. FIG. FIG. 10 is an explanatory diagram showing an example of a time change of the gate voltage Vg when the gate G is driven by the gate driving device 16 when the power supply voltage VDC and the IGBT 12 are not short-circuited. It is explanatory drawing which shows an example of the time change of gate voltage Vg and voltage VT1, VT2. It is explanatory drawing for demonstrating the conventional short circuit detection method. It is explanatory drawing for demonstrating the short circuit detection method of an Example. It is a circuit diagram which shows the outline of the circuit structure of the short circuit detection apparatus 120 of a modification. It is explanatory drawing which shows an example of the time change of voltage VT1, VT2, and short circuit detection signal Error when the short-time noise pulse has generate | occur | produced in the gate voltage Vg.

  Next, the form for implementing this invention is demonstrated using an Example.

  FIG. 1 is a configuration diagram showing an outline of a configuration of a power conversion device 10 including a short circuit detection device 20 as an embodiment of the present invention. The power converter 10 includes an insulated gate bipolar transistor (hereinafter referred to as “IGBT”) 12 connected between a power source VDC and the ground, a diode D1 connected in parallel to the IGBT 12, and a power source VDC. And the IGBT 12, the gate drive device 16 that drives the gate G of the IGBT 12, and the short-circuit detection device 20 that detects a short circuit between the power supply VDC and the IGBT 12. Note that the voltage of the power source VDC may be 450 V, 500 V, 550 V, or the like, for example.

  The load 14 includes a reactor L and a diode D2 connected in parallel to the reactor L.

  The gate driving device 16 receives the ON signal ON for turning on the gate G, and drives the gate G by raising the voltage Vg of the gate G of the IGBT 12 when the ON signal ON is rising.

  FIG. 2 is a circuit diagram illustrating an outline of a circuit configuration of the short-circuit detection device 20. The short circuit detection device 20 includes a threshold time generation unit 22, a reference time detection unit 30, and a short circuit detection unit 40.

  The threshold time generator 22 supplies a constant current source IS1 that supplies a current I2 obtained by multiplying the current I1 by a predetermined coefficient α, a capacitor C1 having a capacitance Ct connected to the constant current source IS1, and a capacitor C1 by the constant current source IS1. And a charge start / stop circuit 24 for starting or stopping charging.

  The charge start / stop circuit 24 includes a switching element SW1 configured by a PMOS transistor connected between the constant current source IS1 and the capacitor C1, and a control circuit 26 for turning on / off the switching element SW1. The control circuit 26 compares the gate voltage Vg with the reference voltage Vref1, a NAND circuit that calculates a negative logical product of the output of the comparator CMP1 and the ON signal ON, and outputs the result to the gate GSW1 of the switching element SW1. 28. FIG. 3 shows the time change of the gate voltage Vg when the gate G is driven by the gate driving device 16 when the power supply voltage VDC and the IGBT 12 are not short-circuited (hereinafter, this case is referred to as “normal time”). It is explanatory drawing which shows an example. As shown in the figure, the gate voltage Vg becomes substantially constant for a predetermined time due to the mirror capacitance at a voltage Vs (for example, 5 V) at which current starts to flow between the collector and emitter of the IGBT 12. The reference voltage Vref1 is a voltage lower than the voltage Vs (eg, 3V, 3.5V, 4V, etc.). The control circuit 26 turns off the switching element SW1 when the ON signal ON is not raised, that is, when the gate voltage Vg is not raised. The control circuit 26 turns on the switching element SW1 when the ON signal ON rises, that is, at the start timing when the rise of the gate voltage Vg is started, and starts charging the capacitor C1 by the constant current source IS1. When Vg reaches the reference voltage Vref1, the switching element SW1 is turned off to stop the charging of the capacitor C1 by the constant current source IS1.

  The switching element SW3 is connected to the capacitor C1 in parallel, and is configured as an NMOS transistor in which a signal having a phase opposite to the ON signal ON is input to the gate. The switching element SW3 is turned on to discharge the capacitor C1 when the ON signal ON does not rise, that is, when the gate voltage Vg is not raised.

  With this configuration, the threshold time generation unit 22 outputs the voltage Vc1 of the capacitor C1 charged with the current I2 (= I1 · α) by the constant current source IS1 by the charge start / stop circuit 24 as the threshold time Tth. The threshold time Tth will be described later.

  The reference time detector 30 starts or stops charging the constant current source IS2 that supplies the current I1, the capacitor C2 having the capacitance Ct connected to the constant current source IS2, and the capacitor C2 by the constant current source IS2. And a charging start / stop circuit 34.

  The charge start / stop circuit 34 includes a switching element SW2 formed of a PMOS transistor connected between the constant current source IS2 and the capacitor C2, and a control circuit 36 for turning on / off the switching element SW2. The control circuit 36 compares the gate voltage Vg and the reference voltage Vref2, and calculates the negative logical product of the output of the comparator CMP2 and the ON signal ON, and outputs the result to the gate GSW2 of the switching element SW2. 38. As shown in FIG. 3, the reference voltage Vref2 is higher than the voltage Vs and lower than the voltage of the power supply VDC (for example, 10V, 11V, 12V, etc.). The control circuit 36 turns off the switching element SW2 when the ON signal ON is not raised, that is, when the gate voltage Vg is not raised. The control circuit 26 turns on the switching element SW2 when the ON signal ON rises, that is, at the start timing at which the rise of the gate voltage Vg is started, and starts charging the capacitor C2 by the constant current source IS2. When Vg reaches the reference voltage Vref2, the switching element SW1 is turned off to stop the charging of the capacitor C1 by the constant current source IS2.

  The switching element SW4 is connected in parallel to the capacitor C2, and is configured as an NMOS transistor in which a signal having a phase opposite to the ON signal ON is input to the gate. The switching element SW4 is turned on when the ON signal ON does not rise, that is, when the gate voltage Vg is not raised, and discharges the capacitor C2.

  With this configuration, the reference time detection unit 30 outputs the voltage Vc2 of the capacitor C2 charged with the current I1 by the constant current source IS2 as the reference time Tref2. The reference time Tref2 will be described later.

  The short circuit detector 40 includes a comparator CMP3 that compares the voltage VT1 of the capacitor C1 with the voltage VT2 of the capacitor C2, an inverter INV1 that inverts a signal for turning on and off the switching element SW2 from the control circuit 36, and an output of the inverter INV1. And a NAND circuit 42 that calculates and outputs a negative AND of the output of the comparator CMP3. When the gate voltage Vg reaches the reference voltage Vref2, the short-circuit detection unit 40 determines that the power supply voltage VDC when the voltage VT1 of the capacitor C1 is lower than the voltage VT2 of the capacitor C2, that is, when the voltage Vc2 is smaller than the voltage Vc1. And a short circuit detection signal Verror indicating a short circuit between the IGBT 12 and the IGBT 12.

  FIG. 4 is an explanatory diagram showing an example of temporal changes in the gate voltage Vg and the voltages VT1 and VT2. In the figure, in the gate voltage Vg, a solid line indicates a normal time, and a broken line indicates a time when the power supply voltage VDC and the IGBT 12 are short-circuited (hereinafter, this case is also referred to as “short-circuit time”). Under normal conditions, as shown in the figure, when the gate voltage Vg rises, the voltages VT1 and VT2 of the capacitors C1 and C2 rise due to charging from the charge start / stop circuits 24 and 34. The capacitors C1 and C2 have the same capacity, the capacitor C1 is charged with the current I2 (= current I1 × α) by the charge start / stop circuit 24, and the capacitor C2 is charged with the current I1 by the charge start / stop circuit 34. Therefore, voltage VT1 rises α times faster than voltage VT2 with respect to time. Then, at the reference time Tref1 when the gate voltage Vg reaches the reference voltage Vref1, charging by the charging start / stop circuit 24 is stopped, and the voltage VT1 of the capacitor C1 is held at the voltage Vc1. When the gate voltage Vg reaches the voltage Vs, it is held at the voltage Vs for a while by the mirror capacitance and then rises again. Then, at the reference time Tref2 when the gate voltage Vg reaches the reference voltage Vref2, the charging of the capacitor C2 by the charging start / stop circuit 34 is stopped, and the voltage VT1 of the capacitor C2 is held at the voltage Vc2. As described above, during normal operation, the capacitor C2 is charged while the voltage Vg is held at the voltage Vs, so that the voltage Vc2 is higher than the voltage Vc1. When a short circuit occurs, the gate voltage Vg rises without being held at the voltage Vs, and reaches the reference voltage Vref2 earlier than normal. Therefore, the charging of the capacitor C2 is stopped earlier than normal, and the voltage Vc2 becomes lower than the voltage Vc1 as illustrated. Therefore, a short circuit can be detected by comparing the voltage Vc2 with the voltage Vc1. Since the short circuit detection unit 40 outputs the short circuit detection signal Verror when the voltage Vc2 is lower than the voltage Vc1 at the reference time Tref2, it can detect the occurrence of a short circuit. In order to detect such a short circuit, the current I2 (= I1 · α) of the constant current source IS1 in the charging start / stop circuit 24 that charges the capacitor C1 is adjusted so that the voltage Vc2 at the time of the short circuit is lower than the voltage Vc1. Has been.

  The rise of the gate voltage Vg of the IGBT 12 varies depending on the temperature of the IGBT 12 and manufacturing variations. FIG. 5 is an explanatory diagram for explaining a conventional short-circuit detection method. FIG. 6 is an explanatory diagram for explaining a short circuit detection method according to the embodiment. In the figure, the alternate long and short dash line indicates the time change of the gate voltage Vg when a short circuit occurs between the power supply VDC and the IGBT 12. In the figure, the thick line and the thin line show an example of the time change of the gate voltage Vg before and after such a change occurs. In the conventional short-circuit detection method, as shown in FIG. 5, a reference voltage Vref and a threshold time Tth are determined in advance, and as shown by a thick line in the figure, a time Tref when the gate voltage Vg reaches the reference voltage Vref. The threshold time Tth is compared, and it is detected that a short circuit has occurred when the time Tref is smaller than the threshold time Tth. In this case, as indicated by a thin line in the figure, when the rise of the gate voltage Vg is delayed due to a temperature change of the IGBT 12, the time Tref becomes larger than the threshold time Tth even when a short circuit occurs, and it is erroneous that a short circuit does not occur. I will judge. As described above, the method of determining the threshold time Tth and the reference voltage Vref in advance may cause an erroneous determination. Accordingly, as shown in FIG. 6, when the threshold time Tth is obtained by multiplying the reference time Tref1 from the start timing until the gate voltage Vg reaches the reference voltage Vref1 by α, and the reference time Tref2 is shorter than the threshold time Tth. To detect short circuit. Since the reference time Tref1 changes according to the rise of the gate voltage Vg, the threshold time Tth also changes according to the rise of the gate voltage Vg. Thereby, the erroneous determination of a short circuit can be suppressed. In the embodiment, as described above, the voltage VT1 of the capacitor C1 rises by a predetermined coefficient times the voltage VT2 of the capacitor C2 with respect to time, so that the capacitor voltage Vc1 is output from the threshold time generator 22 as the threshold time Tth. Then, the voltage Vc2 of the capacitor C2 is output as the reference time Tref2 from the reference time detection unit 30, and when the voltage Vc2 is smaller than the voltage Vc1 as the threshold value, the short circuit detection unit 40 outputs the short circuit detection signal Verror. To detect. As described above, the reference time Tref1 changes in response to the rise of the gate voltage Vg, so that the threshold time Tth obtained by multiplying the reference time Tref1 by the value α, that is, the voltage Vc1 also changes. As described above, in the embodiment, since the short circuit is detected using the voltage Vc1 that changes according to the rising change of the gate voltage Vg as a threshold value, the same threshold time Tth is used regardless of the manufacturing variation of the IGBT 12 or the temperature change. Compared with the conventional one that detects a short circuit, it is possible to detect that a short circuit has occurred more appropriately.

  According to the power conversion device 10 of the embodiment described above, the threshold time generation unit 22 outputs the voltage Vc1 as the value α · Tref1, the reference time detection unit 30 outputs the voltage Vc2 as the reference time Tref2, and the short circuit detection unit. When the voltage Vc2 is smaller than the voltage Vc1 as the threshold value at 40, it is detected that a short circuit has occurred, so that it is possible to detect that a short circuit has occurred more appropriately.

  In the power conversion device 10 of the embodiment, the constant current source IS1 and the constant current source IS2 supply currents I2 and I1, but the constant current sources IS1 and IS2 are configured as constant current sources whose current values can be switched. May be. In this way, a short circuit can be detected more appropriately by appropriately switching the currents of the constant current sources IS1 and IS2 according to the characteristics of the IGBT 12.

  In the power conversion device 10 of the embodiment, the short circuit detection unit 40 includes the comparator CMP3, the inverter INV1, and the NAND circuit 42. However, the short circuit detection device 120 of the modification of FIG. As described above, the delay circuit 150 that delays the output of the NAND circuit 42 by the delay time Td, the AND circuit 152 that calculates a logical product of the output of the NAND circuit 42 and the output of the delay circuit 150, and outputs the logical product as the short circuit detection signal Verror, May be provided. FIG. 8 is an explanatory diagram showing an example of temporal changes in the voltages VT1, VT2, and the short circuit detection signal Verror when a short-time noise pulse is generated in the gate voltage Vg. In the figure, the solid line indicates the time variation of various voltages and signals in the power conversion device including the short-circuit detection device 120 of the modification, and the broken line indicates the short-circuit detection signal Verror in the short-circuit detection device 20 of the embodiment. When a short-time noise pulse is generated in the gate voltage Vg, the gate voltage Vg instantaneously rises at a relatively early time due to the noise pulse and exceeds the reference voltage Vref2, and then the gate voltage Vg falls below the reference voltage Vref2. Since the short circuit detection device 20 determines that a short circuit occurs when the voltage Vc2 is lower than the voltage Vc1 when the gate voltage Vg exceeds the reference voltage Vref2, the short circuit detection signal “Error” is output. In the short-circuit detection device 120 according to the modified example, the gate voltage Vg is obtained as a reference voltage by outputting the logical product of the output of the NAND circuit 42 and the output of the NAND circuit 42 delayed by the time Td by the delay circuit 150 as the output Error. When the time exceeding Vref2 continues for the time Td or longer, the short circuit detection signal Verror is output. Therefore, by making the delay time Td in the delay circuit 150 longer than the time when the expected noise pulse is generated, it is possible to suppress erroneous detection of a short circuit due to the noise pulse.

  In the power conversion device 10 of the embodiment, the short-circuit detection unit 40 outputs the voltage VT1 with the threshold time generation unit 22 as the threshold time Tth, outputs the voltage VT2 with the reference time detection unit 30 as the reference time Tref2, and the voltage VT2 is When the voltage is lower than VT1, it is detected that a short circuit has occurred. The threshold time generation unit 22 detects the reference time Tref1 from the gate voltage Vg from the voltage sensor that detects the gate voltage Vg, multiplies the reference time Tref1 by α to generate the threshold time Tth, and sets the reference time detection unit 30 as the voltage sensor. The reference time Tref2 may be detected from the time until the gate voltage Vg from the reference voltage Vref2 reaches the reference voltage Vref2, and the short circuit may be detected when the reference time Tref2 is smaller than the threshold time Tth.

  The power conversion device 10 of the embodiment is provided with the IGBT 12, but any device may be provided as long as it is a so-called vertical power transistor. For example, a vertical MOSFET may be provided.

  In the embodiment, the case where the present invention is applied to a short-circuit detection device that detects a short-circuit between the power supply VDC and the IGBT 12 is illustrated, but the present invention may be used as a method for detecting such a short-circuit.

  As mentioned above, although the form for implementing this invention was demonstrated using the Example, this invention is not limited at all to such an Example, In the range which does not deviate from the summary of this invention, it is with various forms. Of course, it can be implemented.

  The present invention can be used in the manufacturing industry of short-circuit detection devices.

  DESCRIPTION OF SYMBOLS 10 Power converter device, 12 IGBT, 14 Load, 16 Gate drive device, 20, 120 Short circuit detection device, 22 Threshold time generation part, 24, 34 Charge start stop circuit, 26 Control circuit, 28, 38, 42 NAND circuit, 30 Reference time detection unit, 36 control circuit, 40 short circuit detection unit, 150 delay circuit, 152 AND circuit, C1, C2 capacitor, CMP1 to CMP3 comparator, D1, D2 diode, G, GSW1, GSW2 gate, INV1 inverter, IS1, IS2 Constant current source, L reactor, SW1 to SW4 switching element.

Claims (5)

A power conversion device comprising: a vertical power transistor connected between a power source and a ground; a load connected between the power source and the power transistor; and a gate driving device that drives a gate of the power transistor. A short-circuit detection device that detects a short circuit between the power source and the power transistor in the device,
A first reference time from a start timing at which the gate voltage of the power transistor is started to rise by the gate driving device to a first reference voltage lower than a predetermined voltage at which the gate voltage starts to flow through the power transistor. Threshold time generation means for generating a threshold time multiplied by a predetermined coefficient;
A reference time detecting means for detecting a second reference time from the start timing to a second reference voltage in which the gate voltage is higher than the predetermined voltage and lower than the voltage of the power supply;
When the second reference time is shorter than the threshold time, short-circuit detecting means for detecting that the short-circuit has occurred,
A short-circuit detection device comprising: The short-circuit detection device according to claim 1,
The threshold time generation means includes
A first constant current source for supplying a second current obtained by multiplying the first current by the predetermined coefficient;
A first capacitor connected to the first constant current source;
The charging of the first capacitor by the first constant current source is started at the start timing, and the charging of the first capacitor by the first constant current source is stopped when the gate voltage reaches the first reference voltage. A first charge start / stop circuit to perform,
Have
Means for outputting the voltage of the first capacitor charged by the first constant current source by the first charge start / stop circuit as the threshold time;
The reference time detecting means is
A second constant current source for supplying the first current;
A second capacitor connected to the second constant current source;
The charging of the second capacitor by the second constant current source is started at the start timing, and the charging of the second capacitor by the second constant current source is stopped when the gate voltage reaches the second reference voltage. A second charge start / stop circuit that
Have
Means for outputting the voltage of the second capacitor charged by the second constant current source by the second charge start / stop circuit as the second reference time;
The short circuit detection means detects that the short circuit has occurred when the voltage of the second capacitor output as the second reference time is lower than the voltage of the first capacitor output as the threshold time. Is,
Short-circuit detection device. The short-circuit detection device according to claim 2,
The first constant current source includes a current changing unit that changes the first current.
Short-circuit detection device. The short-circuit detection device according to any one of claims 1 to 3,
The reference time detection means detects a decrease in the gate voltage when the gate voltage becomes equal to or lower than the second reference voltage after detecting the second reference time,
The short-circuit detection means has the short circuit when a decrease in the gate voltage is detected within a predetermined time after the second reference time is detected even when the second reference time is shorter than the threshold time. To detect that,
Short-circuit detection device. A power conversion device comprising: a vertical power transistor connected between a power source and a ground; a load connected between the power source and the power transistor; and a gate driving device that drives a gate of the power transistor. A short-circuit detection method for detecting a short-circuit between the power source and the power transistor in an apparatus,
A first reference time from a start timing at which the gate voltage of the power transistor is started to rise by the gate driving device to a first reference voltage lower than a predetermined voltage at which the gate voltage starts to flow through the power transistor. Generate a threshold time multiplied by a predetermined coefficient,
Detecting a second reference time from the start timing until the gate voltage reaches a second reference voltage higher than the predetermined voltage and lower than the voltage of the power source;
When the second reference time is shorter than the threshold time, it is detected that the short circuit has occurred.
Short circuit detection method.

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