JPH09182275A - Circuit for protecting semiconductor transistor for power from overcurrent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect an element by detecting the current flowing to an insulated gate bipolar transistor(IGBT), making use of the voltage between the collector and the emitter of IGBT, and judging an overcurrent and a short circuit current by the detected current thereby executing the operation of protecting it from the overcurrent and the short circuit current. SOLUTION: In case of protection form an overcurrent, the collector current ic of an IGBT increases, and voltage Vs increases, and the voltage at the junction A between a resistor R3 and a diode D1 goes up, and the voltages of noninverted input + terminals of CM1 and CM2 go up. Then, in case the voltage of the noninverted input + terminal of the comparator CM1 is lower than the reference voltage Vr2 of the comparator CM2, the output of the comparator CM1 is outputted as high signal, and when detecting an overcurrent, IGBT is turned off. On the other hand, in case of a short circuit current, when the detected voltage V1 of a current detector 12 goes higher than the reference voltage Vr2 of the comparator CM2, high signals are outputted from the comparators CM1 and CM2, and at the time of detection of a short circuit current, it is turned off completely after lowering the voltage of the gate G of the IGBT by one stage. As a result, proper element protection can be made.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power semiconductor transistor (for example, an insulated gate bipolar transistor as a typical one).
sistor: IGBT). ) Overcurrent protection circuit of the power semiconductor transistor (IGBT) that can protect the IGBT element against overcurrent and short circuit current without using a separate current sensing means. It is about.

[0002]

2. Description of the Related Art Generally, for driving an IGBT, an AC power supply (AC) is converted into a pulse signal by a photocoupler (PC1), and the pulse signal is used as an input signal (Vin) by an input signal (Vin).
Generates a gate signal (VGE) for driving the IGBT in response to
It is designed to drive T.

FIG. 1 is a conventional IGBT overcurrent protection circuit diagram. As shown here, the collector of a transistor (Q1) to which an input signal (Vin) is applied is replaced by a transistor (Q2).
And the PNP transistor (Q3) are commonly connected to the base, and connected to the power supply terminal (VD) through the resistor (R1), and the commonly connected emitters of the transistors (Q2) and (Q3) are connected through the resistor (R2). It is connected to the gate of the IGBT.

In addition, an overcurrent comparator (C
M1) and the inverting input (-) terminal of the short-circuit current comparator (CM2) are respectively connected, and the output of the overcurrent comparator (CM1) that compares the emitter detection voltage of the IGBT with the overcurrent reference voltage (Vrl). The terminal is connected to the base of the transistor (Q4) through the delay device (1), the collector output terminal of the transistor (Q4) is connected to the base common terminal of the transistors (Q2) and (Q3),
The emitter detection voltage of the above IGBT and the short-circuit current reference voltage (Vr
The output terminal of the short-circuit current comparator (CM2) for comparing 2) is connected to the base of the transistor (Q5), and the collector of the transistor (Q5) is connected to the gate terminal of the IGBT through the resistor (R4). .

In the conventional IGBT drive circuit having the above-described structure, when the input signal (Vin) is high ("H") when the signal is normal as shown in FIG. Q1) is turned on, which turns off the transistor (Q2), PNP
The transistor (Q3) is turned on, and the low ("L") signal (VGE) is applied to the gate of the IGBT as shown in FIG. 2B, so that the IGBT is turned off.

On the contrary, when the input signal (Vin) is low, the transistor (Q1) is off, the transistor (Q2) is on, the PNP transistor (Q3) is off, and the high signal (VG
Since E) is applied to the gate of the IGBT, that IGBT is turned on.

On the other hand, in the case of overcurrent (OC) protection, the IGBT
Collector current ic increases and the voltage (VS) across the resistor (R5) for current detection increases. If the voltage across the current detection resistor (R5) (VS) is higher than the reference voltage (Vr1) of the overcurrent comparator (CM1) or lower than the reference voltage (Vr2) of the short-circuit current comparator (VM2) In this case, the output of the overcurrent comparator (CM1) is output as a high signal, the transistor (Q4) is turned on after the delay time of the delay device (1), and the PNP transistor (Q3) is turned on. When the overcurrent is detected as shown in, the PNP transistor (Q3) is turned on and the IGBT is turned off after the delay time.

In case of short circuit current (SC) protection, the voltage (VS) across the current detecting resistor (R5) is the short circuit current comparator (CM2).
Higher than the reference voltage (Vr2; Vr2> Vr1) of
All the two comparators (CM1) and (CM2) will output a high signal.

As described above, when the short-circuit current comparator (CM2) outputs a high signal, the transistor (Q5) is immediately turned on to lower the gate voltage of the IGBT by one step, and the delay device
After the delay time of (1), the transistor (Q4) and the PNP transistor (Q3) are turned on to turn off the IGBT. That is, when a short circuit current is detected, the IGBT is turned off by controlling in two stages as shown in FIG.

However, according to such a conventional IGBT drive circuit, two types of IGBT emitter currents are required. That is, without using an IGBT with multiple emitters,
The overcurrent and short-circuit current cannot be detected, and the junction temperature of the IGBT (j
There is a problem that the overcurrent (OC) and short-circuit current (SC) protection operations are performed regardless of the junction temperature.

[0011]

In consideration of this, the present invention detects the current flowing in the IGBT by utilizing the voltage between the collector and the emitter (CE) of the IGBT, and detects the overcurrent and short-circuit current. It is an object of the present invention to provide an IGBT overcurrent protection circuit that can protect an IGBT element by performing an overcurrent and short-circuit current protection operation based on the judgment.

[0012]

In order to achieve the above object, the invention of claim 1 is a drive means for outputting a drive gate voltage of an IGBT in response to an input signal (Vin) which is a pulse signal. And; current detecting means for detecting the current between the collector and emitter of the IGBT; and comparing the detected voltage of the current detecting means with a reference voltage for overcurrent to control the output of the driving means to turn off to a low level It is characterized in that it is constituted by an overcurrent control means; and a short circuit current control means for comparing the detection voltage of the current detection means with a reference voltage for the short circuit current to reduce the gate voltage of the IGBT.

[0013]

FIG. 3 is an IGBT overcurrent protection circuit diagram according to the present invention. As shown in FIG. 3, an IGBT drive gate voltage is output in response to an input signal (Vin) which is a pulse signal. The drive unit (11) that makes the current and the current detection unit (12) that detects the collector-emitter current of the IGBT compare the detection voltage of the current detection unit and the reference voltage for overcurrent to set the output of the drive unit to the low level. It is composed of an overcurrent control unit (13) that controls to turn it off and a short-circuit current control unit (14) that compares the detection voltage of the current detection unit with a reference voltage for the short-circuit current to reduce the gate voltage of the IGBT. .

The current detecting section (12) is composed of a resistor (R3) and a diode (D1) for detecting the current between the collector and the emitter of the IGBT.

The operation and effect of this embodiment having the above-described structure will be described below. First, in this embodiment, the collector-emitter current of the IGBT is detected by using the resistor (R3) and the diode (D1) respectively connected to the gate and collector of the IGBT (power semiconductor transistor) to detect overcurrent and short circuit. The current is determined and controlled.

First, in a normal case, when the input signal (Vin) is low, the transistor (Q1) in the driver (11) is off, the transistor (Q2) is on, and the PNP transistor (Q2) is on.
3) is turned off and the high signal is applied to the gate (G) of the IGBT, so that the IGBT is turned on. On the contrary, when the input signal (Vin) is high ("H"), the transistor (Q1) is on, the transistor (Q2) is off, the PNP transistor (Q3) is on and the IGBT is off.

On the other hand, in the case of overcurrent (OC) protection, the IGBT
The collector (C) current ic of the IGBT increases and the collector-emitter (CE) voltage of the IGBT (VCE (sat) see Fig. 4) increases,
As a result, the voltage at the connection point (A) between the resistor (R3) and the diode (D1) rises.

Then, the voltage (V1) at the non-inverting input (+) terminals of the comparators (CM1) and (CM2) rises.

If the voltage of the non-inverting input (+) terminal of the comparator (CM1) is lower than the reference voltage (Vr2) of the short circuit current comparator (CM2), the output of the overcurrent comparator (CM1) will be Therefore, the transistor (Q4) is turned on after the delay time of the delay device (1) is turned on and the PNP transistor (Q3) is turned on to turn off the IGBT when an overcurrent is detected.

On the other hand, in the case of short-circuit current (SC) protection, if the detection voltage (V1) of the current detector (12) becomes higher than the reference voltage (Vr2; Vr2> Vr1) of the short-circuit current comparator (CM2), The high signal is output from the two comparators (CM1, CM2). When the short-circuit current comparator (CM2) outputs a high signal as described above, the transistor (Q5) is immediately turned on to lower the gate (G) voltage of the IGBT by one stage, and after the delay time of the delay device (1), the transistor (Q5) is turned on. Q4) and PNP transistor (Q3) are turned on and turn off the IGBT. That is, when a short circuit current is detected, the gate (G) voltage of the IGBT is immediately lowered by one step and then completely turned off.

Thus, the voltage between the CEs of the IGBT (VCE (sat) (see FIG. 4) varies depending on the junction temperature. The higher the temperature, the higher VCE (sat). The voltage between CE and VCE of IGBT by resistance (R3) and diode (D1)
Since (sat) is sensed and is controlled by comparing it with the overcurrent reference voltage and the short-circuit current reference voltage, it is possible to automatically respond to changes due to temperature.

[0022]

As described above, according to the present invention, since a separate emitter for current detection of the IGBT is unnecessary, overcurrent protection and short-circuit current protection operations can be performed using a general IGBT. In addition, when the junction temperature of the IGBT is high, it becomes possible to perform overcurrent and short-circuit current protection operations with a lower current value, and perform an appropriate element protection function against temperature changes. There is an effect that can be.

[Brief description of the drawings]

FIG. 1 is a conventional IGBT drive protection circuit diagram.

2A to 2D are operation waveform diagrams according to FIG.

FIG. 3 is an IGBT drive protection circuit diagram according to the present invention.

FIG. 4 is a characteristic diagram showing the relationship between the collector-emitter voltage of the IGBT and the temperature.

[Explanation of symbols]

 11: drive part 12: current detection part 13: overcurrent control part 14: short-circuit current control part R3: resistance D1: diode CM1, CM2: comparator Q1-Q5: transistor

Claims (3)

[Claims] 1. A drive means for outputting a drive gate voltage of a power semiconductor transistor in response to an input signal (Vin) which is a pulse signal; a current between a collector and an emitter of the power semiconductor transistor is detected by a voltage. Current detection means; overcurrent control means for comparing the detection voltage of the current detection means with a reference voltage for overcurrent and, after a delay of a predetermined time, controlling the output of the drive means to turn off to a low level; An overcurrent protection circuit for a power semiconductor transistor, comprising: short-circuit current control means for comparing the detection voltage of the current detection means with a reference voltage for the short-circuit current to reduce the gate voltage of the power semiconductor transistor. . 2. The power detecting device according to claim 1, wherein the current detecting means comprises a resistor for detecting a current between the collector and the emitter of the power semiconductor transistor and a diode. Overcurrent protection circuit for semiconductor transistors. 3. A resistor is connected between the gate of the power semiconductor transistor and the comparator, and a diode is connected between the collector of the power semiconductor transistor and the connection point between the resistor and the comparator. The overcurrent protection circuit for a power semiconductor transistor according to claim 2, wherein the overcurrent protection circuit is configured as follows.