JPH027714A - Protection device for component when fault current flows - Google Patents

Abstract

PURPOSE:To improve the reliability of a component even at the time of flowing a faulty current such as short-circuiting a load by providing a circuit clamping a gate-emitter of the component in a way that the gate-emitter voltage does not exceed the absolute maximum rating of the component. CONSTITUTION:Constant voltage diodes ZD1, ZD2 are provided between the gate and emitter of an electrostatic induction type self extinction component 1 and a gate-emitter voltage VGE at fault current is clamped to the Zener voltage. The Zener voltage of the diode ZD1 is selected over the absolute maximum rating of the gate-emitter voltage of the component 1. Moreover, since the diode ZD2 is connected in series, it is required to select the Zener voltage of the diode ZD1 lower by the forward voltage drop of the diode ZD2. Thus, the gate-emitter voltage of the electrostatic induction type self extinction component is clamped to the specified voltage at fault current such short-circuit of load and the positive feedback effect of the component is prevented thereby suppressing the increase of current at the time of short-circuiting and improving the reliability of the component.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to the protection of electrostatic induction type self-extinguishing elements, and more particularly to a protection device for the element suitable for the occurrence of abnormal current in the element.

[Conventional technology]

VC between the gate and source of MOS-FET! Regarding inserting a Zener for the purpose of surge voltage protection, please refer to Mitsubishi MOS-FET/B1-MOS module) Li (H
B9756 B (January 1988) described in the PLO.

On the other hand, the Zener voltage (20V) is specified in P4/4 of a base amplifier for driving a MOS-FET module (TSM-203) published by Mitsubishi Electric Corporation. Current situation M
The absolute maximum rating of the gate voltage of elements such as O8-FET and Bi-MO5゜1GBT is 20V, so if you only want to protect the gate of the element from electrostatic damage and surge voltage, select the Zener voltage above 20V. It is a known technology to do this, and all MOS-ICs are designed to do this, but if an abnormal current such as a load short circuit flows.

For example, due to the dv/dt between the collector and emitter of a 1GBT, the voltage is divided according to the capacitance between each terminal, and the potential between the gate and emitter increases.

If the above increase is Δ■, the voltage between the gate and emitter becomes (15+Δv)■, which is apparently overdriven and exhibits a kind of positive feedback phenomenon, which causes the collector current to grow and threatens the reliability of the main element.

In other words, considering dynamic conditions such as short-circuiting of the main element, it is ideal to clamp the increase in gate voltage to below Ov.

As mentioned above, in order to improve the reliability of the main element even during abnormal currents such as load short circuits, Zener voltage (>absolute maximum rating of gate voltage) is used for the sole purpose of electrostatic damage and surge voltage protection. value) cannot achieve the purpose.

The purpose of the present invention is to select a Zener voltage so that the voltage rise between the gate and emitter that occurs during abnormal currents such as the above-mentioned load short circuit can be clamped to below the absolute maximum rated value of the gate voltage, and to suppress the abnormal current growth during short circuits. The purpose is to insert a constant voltage diode in parallel between the gate and emitter of a static induction type self-extinguishing element, and to make the Zener voltage of this constant voltage diode higher than the absolute maximum rated value between the gate and emitter of the element. This is achieved by controlling the voltage rise between the gate and emitter during current flow.

In other words, a circuit is installed between the gate and emitter of the device to clamp it so that the voltage between the gate and emitter does not exceed the absolute maximum rating of the device.

[Effect]

The constant voltage diode operates to clamp the rise between the gate and emitter of the electrostatic induction type self-extinguishing element to a preselected Zener voltage when an abnormal current occurs. This prevents the voltage between the gate and emitter from increasing more than necessary in the event of an abnormality, making it possible to significantly control abnormal current in the event of a short circuit, thereby strengthening the short circuit tolerance of the device and further improving the reliability of the device.

〔Example〕

Hereinafter, one embodiment of the present invention will be explained with reference to FIG.
R4 is a resistor, IC is an inverter, PH/CEL is a photocoupler that electrically isolates the low voltage side and high voltage side, Ql, Q2
is an npn transistor, Q3 is a pnp transistor,
1 is an electrostatic induction type self-extinguishing element which is a main switching element, El is a constant voltage power source for forward biasing the main element 1, and E2 is a constant voltage power source for forward biasing.

It is the simplest circuit configuration diagram for driving the main switching element 1 according to the input control signal of the inverter IC.

If the output of 1c above is “L”, the photocoupler PH
-CEL is turned on, transistors Q1 and Q3 are turned off, transistor Q2 is turned on, a positive gate voltage is applied to the main element 1, and the main element 1 is turned on. On the other hand, if the IC output is IIHFI, the photocoupler P
H-CEL is turned off, only transistor Q2 is turned off, transistors Q1 and Q3 are turned on, a negative gate voltage is applied to main element 1, and main element 1 is turned off.

In this manner, the electrostatic induction type self-extinguisher 1, which is the main element, can be switched between on and off states according to the input signal to the IC.

At this point, due to some reason, an abnormal current ■ as shown in FIG. 7(a) occurs.

flows, the capacitance Cc between the collector and the goo 80 due to the basic structure of the electrostatic induction type self-extinguishing element which is the main element,
, the gate-emitter voltage ■6 due to the capacitance CaE between the gate G and the emitter E, and the capacitance C0 between the collector C and the emitter.
．． rises.

As shown in FIG. 6, an electrostatic induction type self-extinguishing element can flow a collector current depending on the magnitude of the potential v6 between its gate and emitter. is determined. Also, the higher the vag, the larger this IC becomes.

As described above, in the case of an electrostatic induction type self-extinguishing element, when an abnormal current flows through the collector, the gate voltage V GH increases as described above.
becomes higher than the constant voltage power source E1 for forward bias, and positive feedback is applied, and the main element is overdriven, causing an abnormal current to grow and deteriorating the main element.

The present invention has been made in view of the above points, and by providing a constant voltage diode in parallel between the gate and emitter of the main element as shown in FIG. The purpose is to clamp the voltage (6) to this Zener voltage. In other words, the Zener voltage of ZDI is set to be equal to or higher than the absolute maximum rated value between the gate and emitter of element 1.

In the illustrated embodiment, since the Zener diode ZD2 is connected in series with ZDI, it is necessary to select the Zener voltage of ZDI as low as the forward voltage drop of ZD2.

According to the present invention, as shown in FIG. 7(b), it is possible to clamp the voltage between the gate and emitter when an abnormal current occurs, so it is possible to suppress the growth of the collector current of the main element, and the reliability of the main element is increased. You can further improve your sexuality. On the other hand, FIGS. 2 to 5 show other embodiments of the present invention, and the purpose thereof is the same as the implementation effect shown in FIG. 1 above.

FIG. 2 shows an example in which a diode D2 is used instead of ZD2 and clamped only during forward bias.

Figure 3 shows how the diode D1 provides gate control during abnormal current.
Clamping the emitter potential Vat to a constant voltage power supply E1,
This embodiment is configured to suppress the growth of current, and similar effects can be obtained.

Further, FIGS. 4 and 5 show embodiments for making the impedance between the gate and emitter low.

Even if the above-mentioned embodiments are appropriately combined and used together, the same effect as the object of the present invention is achieved.

Further, the present invention can be applied to MOS-F, ET, Bi-MOS.

Exactly the same effect can be obtained even if it is implemented in a module such as 1GBT.

[Effects of the Invention] According to the present invention, the voltage between the gate and emitter of the electrostatic induction type self-extinguishing element is clamped to a specified voltage at the time of an abnormal current such as a load short circuit, thereby preventing the positive feedback effect of the element. This has the effect of suppressing current growth during short circuits and further improving device reliability.

[Brief explanation of the drawing]

FIG. 1 shows a gate circuit of one embodiment of the present invention, FIGS. 2 to 5 show gate circuits of other embodiments of the invention, and FIG. 6 shows a VC! -I. FIG. 7(a) shows the short-circuit characteristics when the present invention is not implemented, and FIG. 7(b) shows the short-circuit characteristics when the present invention is implemented. R1-R5: Resistance: C1: Capacitor; i, c:
Inverter; PH-CEL: Photocoupler; Q1~Q3
: Transistor; El: Forward bias constant voltage power supply; Di
, D2: diode = E2: constant voltage power supply for reverse bias;
C: Collector terminal; ZDI, ZD2: Constant voltage positive; G: Gate terminal; 1: Electrostatic induction type self-extinguishing element; E: Emitter terminal; vC: Collector-emitter voltage; VeE: Gate-emitter voltage ; IC: Collector current; t: Time; Cca: Collector-emitter equivalent capacitance; Cca: Collector-gate equivalent capacitance; CGE: Gate-emitter equivalent capacitance '-1\do Figure 7 (b)

Claims (1)

[Claims] 1. The above-mentioned device is connected through an electrostatic induction type self-extinguishing element (hereinafter referred to as the main element), a constant voltage power supply for driving the main element, and a control element that opens and closes in response to an input control signal. A device comprising a gate circuit that applies a constant voltage to the gate of the main element, comprising a constant voltage diode connected in parallel and in anti-series between the gate and emitter of the main element, the Zener voltage of the constant voltage diode being A protection device for an element at the time of abnormal current, characterized in that the voltage is lower than the absolute maximum rated value between the gate and emitter of the element. 2. A diode D1 is connected between the gate terminal of the main element and the constant voltage power supply so that the main element gate terminal is on the anode side and the positive potential side of the power supply is on the cathode side. A protection device for an element at the time of abnormal current according to item 1. 3. The device for protecting elements during abnormal current according to claim 2, wherein the diode is a Schottky barrier diode with a low forward voltage drop. 4. A resistor R5 is connected in parallel between the gate and emitter of the above main element.
The device for protecting an element at the time of abnormal current according to any one of claims 1 and 2, characterized by comprising: 5. The protection device for an element at the time of abnormal current according to claim 4, characterized in that the parallel resistance R5 between the gate and emitter is constructed with a low resistance of several hundred ohms or less. 6. At the time of abnormal current according to any one of claims 1, 2, and 4, a low impedance capacitor C1 is provided in parallel between the gate and emitter of the element. Element protection device.