JPH11356035A - Gate driving device for voltage-driven self-arc-extinguishing element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the safety and reliability of a power conversion device, by detecting a failure in an element even when on-gate voltage or off-gate voltage is not regularly applied. SOLUTION: When an upper arm IGBT 5 is on and a lower arm IGBT 6 is off, in a gate pulse logic portion 1 a light emitter 11 for upper arm gate pulse emits light. The light receiver 15 for upper arm gate pulse in a driving circuit 2 is turned on, and a first-stage transistor 31 is turned on to bring the base of a next-stage transistor 33 at 'L'. Meanwhile, a comparator 36 for judging feedback signals from the upper arm outputs 'L' which means the on-state of the IGBT, and a light emitter 12 for upper arm feedback does not emit light. In the gate pulse logic portion 1, the light emitter 16 for upper arm feedback outputs 'L', and an AND gate 53 is brought in 'L' output. Thus, gate pulses of the lower arm are blocked. As a result, the safety and reliability can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gate drive device of a power conversion device using a voltage-driven self-extinguishing device as a switching device of a main circuit of the device, and particularly to an on / off state of the device. And a technology for determining a failure of an element.

[0002]

2. Description of the Related Art Conventionally, as a semiconductor switching element of a large-capacity power converter, a GTO (gate turn-off thyristor), which is a current-driven element, has been mainly used. The capacity of IGBTs (insulated gate bipolar transistors), which is one of them, is increasing, and the applicable range is expanding. The gate current of the voltage-driven switching element only flows at the time of turn-on / turn-off, and the drive power can be easily reduced with a small power. Therefore, a circuit having a small power capacity is required and the device is downsized. For this reason, it has come to be used frequently in order to meet the recent demand for miniaturization and weight reduction.

Meanwhile, as a method of detecting a failure of an IGBT of a power converter using an IGBT, there is disclosed in FIG.
Publication No. 8-298786 can be mentioned. The publication also states that IGBT
Monitoring the gate-emitter voltage of the IGBT
With respect to a reference value set to a value lower than the gate threshold voltage of the IGBT, a feedback signal for determining that the IGBT is on when the gate-emitter voltage is high, and determining that the IGBT is off when the gate-emitter voltage is low is used. It has been shown that the safety and reliability of the power conversion device are improved by providing an interlock function to the generation logic of the gate pulse of the IGBTs connected in series to the same arm so as to prevent an arm short circuit. .

[0004]

In the above-described IGBT gate drive device, it is determined whether the voltage between the gate and the emitter is higher or lower than the gate threshold voltage of the IGBT, thereby turning on / off the IGBT. The off state can be determined. However, even when the normal on-gate voltage or off-gate voltage is not applied between the gate and the emitter, for example, because the insulation of the gate of the IGBT deteriorates and the leakage current between the gate and the emitter increases, Could not be detected.

The present invention adds a function of detecting a failure of an element even when such an on-gate voltage or off-gate voltage is not properly applied, and further improves the safety and reliability of the power converter. It is an object of the present invention to provide a gate driving device for a self-extinguishing element.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to provide a gate drive device for controlling on / off of a voltage-driven self-extinguishing element connected in series to the same arm as a switching element of a main circuit of a power conversion circuit, Pulse generating means for generating a gate pulse signal; means for driving the element based on the gate pulse signal; and means for determining a gate-emitter voltage of the element. There is a means for switching according to an off state, and a structure having a gate drive means for issuing a feedback signal indicating a result of on / off determination, wherein both a gate pulse signal and a feedback signal of one of the elements of the same arm are off. When the block of the gate pulse signal of the other element of the same arm is unblocked, Blocking the gate pulse signal of another element of the same arm when the gate pulse signal and / or the feedback signal of the element are on, and further, the on / off state of the gate pulse signal and the feedback signal This is achieved by detecting that the ON / OFF state is not consistent for a certain period of time or more and issuing a failure signal of the element.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. In this embodiment, an explanation will be made assuming that an IGBT is used for the voltage-driven self-extinguishing element.

FIG. 1 shows a configuration of a gate drive device for one arm of a main circuit of a power conversion circuit according to an embodiment of the present invention. In FIG. 1, an upper arm IGBT5 and a lower arm IGBT6 are connected in series as one arm of a main circuit of the power conversion circuit, both ends of both arms are connected to a DC power supply, and an upper arm IGBT5 and a lower arm IGBT6 are provided. The upper arm gate drive circuit 2 and the lower arm gate drive circuit 3 are respectively connected between the gate and the emitter of the IGBT.

On the other hand, in the gate pulse logic section 1, the gate pulse generation circuit 4 has a function of generating a gate pulse signal, and emits light for an upper arm gate pulse via AND gates 51 and 52 which block the gate pulse signal. The device 11 is connected to the lower arm gate pulse light emitting device 13. Further, a signal obtained by inverting the polarity of the gate pulse from the gate pulse generation circuit 4 and the upper arm gate drive circuit 2
The output of the photodetector 16 of the feedback signal from the input device and the output of the photodetector 18 of the feedback signal from the lower arm gate drive circuit 3 are input to the ADN gates 53 and 54, and the outputs of the AND gates 53 and 54 are respectively AND gates 51, 52 are connected.

The signals output from the AND gates 51 and 52 and the signal obtained by inverting the polarity of the output of the photodetectors 16 and 17 of the feedback signal are connected to EX-OR gates 61 and 62, respectively. Outputs of 61 and 62 are connected to on-delay circuits 63 and 64, respectively.

Signal transmission between the gate pulse logic unit 1 and the upper arm gate drive circuit 2 and the lower arm gate drive circuit 3 is connected by an optical fiber for electrical insulation. The gate pulse light emitters 11 and 12 of the gate pulse logic unit 1 and the gate pulse light receivers 15 and 15 of the upper arm gate drive circuit 2 and the lower arm gate drive circuit 3
16 are connected by gate signal optical fibers 19 and 20, and feedback signal light emitters 12 and 14 of the upper arm gate drive circuit 2 and the lower arm gate drive circuit 3.
And the feedback signal receivers 16 and 18 of the gate pulse logic unit 1 are connected by feedback signal optical fibers 20 and 22.

Next, the operation of this embodiment will be described below.

First, consider a normal state in which the upper arm IGBT 5 is on and the lower arm IGBT 6 is off.

In the gate pulse logic section 1, the upper arm gate pulse light emitting device 11 emits light, the upper arm gate drive circuit 2 upper arm gate pulse light receiving device 15 turns on, the first stage transistor 31 turns on, The base of the next-stage transistor 33 is set to “L”. The collector of the next-stage transistor 33 is pulled up by a pull-up resistor 43,
The last-stage transistor 34 (npn junction type) is turned on, and a positive voltage is applied between the gate and emitter of the upper arm IGBT 5 via the on-gate resistor 44 and the gate resistor 49.

On the other hand, the comparator 36 for determining the feedback signal of the upper arm has a negative-side input to the comparator 36 for determining the feedback signal.
The gate voltage of the IGBT is input. In addition, the series voltage of the DC power supplies 37, 38 is applied to the positive side input, and the voltage dividing resistors 42, 4
6, a reference voltage switching resistor 45 and a reference voltage switching transistor 32 input a reference voltage. At this time, since the first-stage transistor 31 is on,
The reference voltage switching transistor 32 is turned off, and as a result, the reference voltage of the comparator 36 is determined by the voltage dividing resistors 42 and 46.

The reference voltage input to the positive side of the comparator 36 is equal to the gate voltage when the upper arm IGBT 5 is turned on.
It is set about 3 V lower than the voltage between the emitters. Thereby, it is determined that a normal ON voltage is applied between the gate and the emitter of the upper arm IGBT 5 and the comparator 3
Numeral 6 outputs "L" indicating the ON state of the IGBT, and the upper arm feedback light emitter 12 does not emit light.

At this time, in the gate pulse logic section 1, the upper arm feedback light receiver 16 outputs "L", and the AND gate 53 outputs the "L" signal of the upper arm feedback light receiver 16 and the gate. Since the inverted signal of the gate pulse of the pulse generation circuit 4 is input, the AND gate 53 outputs “L”, and the output of the AND gate 52 that blocks the lower arm gate pulse becomes “L”, and the lower arm gate pulse is output. Is blocked.

Next, consider a normal state in which the upper arm IGBT 5 is off.

In the gate pulse logic section 1, the upper arm gate pulse light emitter 11 is turned off, the upper arm gate pulse light receiver 15 is turned off, and the upper arm gate pulse light receiver 15 is turned off.
The first-stage transistor 31 is turned off, and the base of the next-stage transistor 33 is set to “H” by the pull-up resistor 41 to be turned on. Therefore, the last-stage transistor 35 (pnp junction type) is turned on, and the off-gate resistor 48 and the gate resistor 49 are connected. A negative voltage is applied between the gate and the emitter of the upper arm IGBT5 through the gate.

On the other hand, at this time, since the reference voltage switching transistor 32 is turned on, the reference voltage input to the positive side of the comparator 36 is a parallel resistance composed of the voltage dividing resistor 42, the voltage dividing resistor 46 and the reference voltage switching resistor 45. , And the reference voltage is switched to a lower reference voltage than when the IGBT is turned on. The reference voltage at this time is the upper arm IGB
It is set to be about 3 V higher than the gate-emitter voltage when T5 is off. Thereby, it is determined that the normal off voltage is applied between the gate and the emitter of the upper arm IGBT 5, and the comparator 36 outputs “H” indicating the off state of the IGBT. 12 is caused to emit light.

At this time, in the gate pulse logic section 1, the upper arm feedback light receiver 16 outputs "H", and the AND gate 53 outputs the "H" signal of the upper arm feedback light receiver 16 and the gate. Since the inverted signal of the gate pulse of the pulse generation circuit 4 is input, the AND gate 53 outputs “H” and the gate pulse of the lower arm is unlocked.

The function of blocking the upper-arm gate pulse by the lower-arm gate pulse signal and the lower-arm feedback signal operates in a similar manner.

In this way, one of the upper and lower arms I
When the GBT is on, by locking the gate pulse of the other arm, a short circuit accident of the upper and lower arms is prevented beforehand, and a highly reliable gate drive device is realized.

Next, a specific setting method of the reference voltage input to the comparator 36 will be described.

The comparator 36 is connected to the gate of the IGBT 5
The ON / OFF state of the IGBT 5 is determined by determining whether the emitter-to-emitter voltage is a regular ON voltage or OFF voltage. Therefore, the reference voltage of the comparator 36 needs to be set to a reference voltage that can determine that the gate-emitter voltage is a regular on-voltage or off-voltage.

As an example, a case will be described in which the gate-emitter voltage of the IGBT is driven at +15 V in the on state and -9 V in the off state.

First, the voltages of the on power supply 37 and the off power supply 38 for driving the gate of the IGBT are determined. Assuming that the voltage drop due to the on-gate resistor 44, the last-stage transistor 34 (npn junction type) and the gate resistor 49 is 3 V, an on-power supply 37 for determining the gate-emitter voltage in the on-state.
Is 18V. Similarly, off-gate resistors 48,
Assuming that the voltage drop due to the last-stage transistor 35 (pnp junction type) and the gate resistor 49 is 3 V, the voltage of the off power supply 38 that determines the gate-emitter voltage in the off state is 12
V.

Next, the comparator 36 sets the gate-emitter voltage for determining that the IGBT 5 is in the on state to 12 V, which is 3 V lower than the on-gate voltage of 15 V, and sets the gate-emitter voltage for determining the off state to the off-gate voltage.
A voltage dividing resistor 42 which is set to −9V which is higher by 3V than 12V,
46 and the value of the reference voltage switching resistor 45 are obtained.

When the IGBT is determined to be on, the gate-emitter voltage +12 V is determined by adding the gate-emitter voltage +12 V and the voltage 12 V of the off power supply 38 to 24 V with respect to the minus terminal of the off power supply 38. Is the reference voltage when the comparator 36 is on. Therefore, the series voltage of 30 V between the ON power supply 37 and the OFF power supply 38 is divided by the voltage dividing resistors 42 and 46, and the potential of the positive input of the comparator 36 is set to 24V. Here, the voltage dividing resistor 42 is 6 kΩ and the voltage dividing resistor 46 is 24 kΩ.

Next, a gate for determining that the IGBT is turned off
The voltage -6V between the emitters becomes 6V with reference to the negative terminal of the off power supply 38.
6 becomes the reference voltage in the off state. In the off state, the reference voltage switching transistor 32 is on, and the voltage dividing resistor 46 and the reference voltage switching resistor 45 are connected in parallel. Here, since the voltage dividing resistor 42 is 6 kΩ first, if the reference voltage switching resistor 45 is set to 1.6 kΩ, the parallel resistance value of the reference voltage switching resistor 45 and the voltage dividing resistor 46 becomes 1.5 kΩ. The potential of the positive input of the comparator 36 can be set to 6 V by the resistance value of 1.5 kΩ and the voltage division of the voltage dividing resistor 42 of 6 kΩ.

With such a circuit configuration, the ON / OFF state of the IGBT is determined, and the ON / OFF state of the IGBT is transmitted to the gate pulse logic unit as a feedback signal. Here, consider the case where the IGBT has failed.

Since the IGBT has an insulated gate structure, a normal state between the gate and the emitter is in a high impedance state.

In general, when the IGBT is destroyed due to an overcurrent accident or the like, the semiconductor chip is burned, the conduction between the gate and the emitter is reduced, or the impedance is reduced to about several thousand ohms or less, and the gate current supplied from the on power supply 37 and the off power supply 38 is reduced. Because of the increase, the voltage drop due to the on-gate resistance 44, the off-gate resistance 48 and the like becomes large, and it becomes impossible to apply the regular on-gate voltage and off-gate voltage. In such a state, although the gate pulse is output from the gate pulse logic unit 1, the feedback signal outputs “H” indicating the off state of the IGBT. Although no pulse is output, the feedback signal is I
"L" indicating the ON state of the GBT is output.

In the gate pulse logic section, the AND gate 5
1 and 52 and the feedback light receivers 16 and 18
Is input to the EX-OR, EX-OR is output when the ON / OFF state of the gate pulse and the ON / OFF state of the feedback signal do not match, and the EX-OR is output.
The signal is output as a failure detection signal via the delays 63 and 64. Here, through the on-delays 63 and 64, I
When the GBT shifts from on to off or from off to on, the EX-OR temporarily transitions to "H" even in a normal state.
Is output.

The gate pulse light emitters 11 and 13 are set to emit light when a gate pulse is output (when the IGBT is turned on), and the feedback light emitters 12 and 1 are turned on.
Reference numeral 4 means that the light emitting state is set when the off state of the IGBT is detected.

In general, there are many failure modes of a light emitter that do not emit light despite an input, and failure modes of the optical fibers 19 to 22 include a disconnection or incomplete insertion of a connector portion. In any case, a failure mode in which no signal is transmitted occurs.

Therefore, by setting the meanings of the light emission states of the gate pulse and the feedback signal as described above, when a failure occurs in the light emitting device or the optical fiber, the IGBT is not turned on in the gate pulse and the operation to the safe side is performed. ,
In the feedback signal, even if the gate pulse is in the OFF state, the feedback signal indicates the ON state, so that the failure of the IGBT can be detected by the above-described EX-OR mismatch detection. With these functions, more safety and reliability can be achieved. An IGBT gate drive device with high reliability can be configured.

FIG. 3 shows another embodiment of the gate drive circuit in the gate drive device of the present invention. The embodiment of FIG. 3 is different from the embodiment of FIG. 1 in that the voltage for judging ON / OFF of the IGBT is used as the emitter voltage of the final-stage transistors 34 and 35, and the other is the same.

FIG. 4 shows another embodiment of the gate drive circuit in the gate drive device of the present invention. The embodiment of FIG. 4 differs from the embodiment of FIG. 1 in that the voltage for judging ON / OFF of the IGBT is used as the base voltage of the final-stage transistors 34 and 35, and the other is the same.

In each of the embodiments shown in FIGS. 3 and 4, the operation of the voltage for judging ON / OFF is the same as the operation of the gate voltage of the IGBT, so that the same functions, functions and effects as those of the embodiment of FIG. 1 are exhibited. Will do.

[0041]

As described above, according to the present invention,
Since the on / off state of the voltage-driven self-extinguishing element such as an IGBT can be accurately determined based on the gate voltage of the element, a failure of the element can be detected quickly. Based on this, the power conversion circuit having the function of interlocking the gate voltages of the elements connected in series to the same arm with each other can prevent the short-circuit of the arm beforehand, so that more safety and reliability can be achieved. It is possible to realize a gate drive device for a high voltage drive type self-extinguishing element.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a gate driving device for a voltage-driven self-extinguishing element according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a conventional technique.

FIG. 3 is a configuration diagram of a gate drive circuit showing another embodiment of the present invention.

FIG. 4 is a configuration diagram of a gate drive circuit showing another embodiment of the present invention.

[Explanation of symbols]

1: gate pulse logic section, 2, 3: gate drive circuit, 4
... Gate pulse generation circuit, 5, 6 IGBT, 11, 1
2, 13, 14 ... light-emitting device, 15, 16, 17, 18 ... light-receiving device, 19, 20, 21, 22, ... optical fiber, 31 ... initial stage transistor, 32 ... reference voltage switching transistor, 3
3: next stage transistor, 34, 35 ... last stage transistor, 36 ... comparator, 37, 38 ... positive / negative drive power supply,
41, 43 ... pull-up resistors, 42, 46 ... voltage dividing resistors,
44 on-gate resistance, 45 reference voltage switching resistance, 47
... Emitter resistance, 48 ... Off gate resistance, 49 ... Gate resistance, 51,52,53,54 ... AND gate, 61,
62: EX-OR gate; 63, 64: ON delay.

Claims (5)

[Claims] 1. A power conversion circuit comprising: a switching element of a main circuit of a power conversion circuit;
A gate drive circuit for controlling off, and a gate of the element
Means for determining the on / off state of the element from an emitter-to-emitter voltage, wherein the means for determining the on / off state of the element includes an on / off state of the element from a power supply for operating the gate drive circuit. And a means for generating a reference voltage for discriminating the off state and a means for comparing the reference voltage with the gate-emitter voltage or a voltage equivalent thereto and outputting a signal indicating the on / off state of the element. A gate driving device for a voltage-driven self-extinguishing element, comprising: 2. The device according to claim 1, wherein the reference voltage for judging the on-state of the element is set lower than a gate-emitter voltage when the element is turned on in a normal state, and the gate-emitter is set to a value lower than the set value. When the emitter-to-emitter voltage is high, the element outputs a signal that determines that the element is in an on state, and the reference voltage that determines the off state of the element is based on a gate-emitter voltage when the element is off in a normal state. A gate drive device for a voltage-driven self-extinguishing device, wherein the device outputs a signal indicating that the device is in an off state when the gate-emitter voltage is lower than the set value. 3. A gate drive device for controlling on / off of a voltage-driven self-extinguishing element connected in series to the same arm as a switching element of a main circuit of a power conversion circuit, wherein a pulse generator for generating a gate pulse signal is provided. Means, gate driving means for driving the element based on the gate pulse signal, and determining the magnitude of a gate-emitter voltage of the element or a voltage equivalent thereto to determine whether the element is turned on or off.
Means for outputting a feedback signal indicating an off state, wherein when the gate pulse signal and the feedback signal of one of the elements of the same arm are both off, a block of the gate pulse signal of the other element of the same arm In a gate drive device for a voltage-driven self-extinguishing element having means for canceling, means for respectively generating a reference voltage for judging an on / off state of the element from a power supply for operating the gate drive means, Means for comparing the reference voltage with the gate-emitter voltage or a voltage equivalent thereto, and using the comparison result as the feedback signal indicating the on / off state of the element. Gate drive for arc elements. 4. A gate drive device for controlling on / off of a voltage-driven self-extinguishing element connected in series to the same arm as a switching element of a main circuit of a power conversion circuit, wherein a pulse generator for generating a gate pulse signal is provided. Means, gate driving means for driving the element based on the gate pulse signal, and determining the magnitude of a gate-emitter voltage of the element or a voltage equivalent thereto to determine whether the element is turned on or off.
Means for outputting a feedback signal indicating an off state, and when both or one of the gate pulse signal and the feedback signal of the one element of the same arm is on, the other element of the same arm has In a gate driving device for a voltage-driven self-extinguishing element having a means for blocking a gate pulse signal, a reference voltage for determining whether the element is on or off is generated from a power supply for operating the gate driving means. Means for comparing the reference voltage with the gate-emitter voltage or a voltage equivalent thereto, and using the comparison result as the feedback signal indicating the on / off state of the element. Drive device for self-extinguishing type die. 5. The device according to claim 3, wherein the on / off state of the gate pulse signal and the on / off state of the feedback signal do not match for a predetermined time or more, and a failure signal of the element is detected. A gate driving device for a voltage-driven self-extinguishing element, comprising a means for outputting.