JP2000323974A - Semiconductor element short-circuit protection circuit - Google Patents

Abstract

(57) Abstract: When a short-circuit current is rapidly suppressed by a short-circuit protection circuit for a semiconductor element with a current detection emitter, an excessive induced voltage is generated due to a floating inductance of the circuit, and the semiconductor element may be destroyed. A plurality of current detection resistors (51, 52) and a plurality of protection semiconductor elements (41, 42) are connected, and the protection semiconductor elements (41, 42) are sequentially turned on to narrow down a short-circuit current in multiple stages. By suppressing a sudden current change, generation of an induced voltage is suppressed, and destruction of the semiconductor element 1 is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a short-circuit protection circuit for a semiconductor device such as an insulated gate bipolar transistor (IGBT).

[0002]

2. Description of the Related Art A conventional short-circuit protection circuit for a semiconductor device having a current detecting emitter is disclosed, for example, in Japanese Patent Application Laid-Open No. 2-13 / 1990.
No. 0951 is disclosed. FIG. 3 shows a conventional example of such a short-circuit protection circuit. In the circuit of FIG. 3, when the circuit to which the semiconductor element 1 is connected is short-circuited, an excessive current exceeding the rating of the semiconductor element 1 is prevented from flowing into the semiconductor element 1 and destroyed. A current flowing from the collector to the emitter of the semiconductor element 1 is detected by the current detection emitter 3 and the current detection resistor 5 which are partially separated, and protection is performed when an excessive current that leads to element destruction is detected. Semiconductor element 4
Is conducted, the gate input voltage is divided by the gate resistor 6 and the protection semiconductor element 4, and the voltage applied between the gate and the emitter of the semiconductor element 1 is suppressed to suppress the short-circuit current. Although not shown, the semiconductor element 1 has a common P-type collector region and is dispersed on a surface in a P-base region formed on the surface of the N-type layer on the P-type collector region. In the IGBT having the formed N emitter region, the semiconductor element 1 having the current detecting emitter is formed by connecting a part of the P base region and the N emitter region to the detecting emitter electrode separated from the main emitter electrode. Is formed.

[0003]

When short-circuit protection is performed in the circuit of FIG. 3, depending on the selected constants of the current detecting resistor 5 and the protective semiconductor element 4, the semiconductor element is turned on at the moment when the protective semiconductor element 4 becomes conductive. Thus, the gate voltage of the semiconductor device 1 is sharply reduced, and accordingly, the short-circuit current flowing through the semiconductor element 1 is rapidly suppressed. Due to the di / dt caused by the rapid narrowing of the short-circuit current and the inductance L floating in the circuit, an excessive induced voltage V (V = L · di /
dt), which may exceed the rated withstand voltage of the semiconductor element 1 and lead to destruction.

[0004]

In order to solve this problem, a plurality of current detecting resistors and a plurality of protective semiconductor elements are connected, and the protective semiconductor elements are sequentially turned on to narrow the short-circuit current. This step is performed in multiple stages to suppress the abrupt current change, thereby suppressing the induced voltage V to a small value and preventing the semiconductor element from being destroyed.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment according to claim 1, and FIG. 2 shows an embodiment according to claim 2. In FIG. 1, two current detection resistors 51 and 52 are connected in series and connected to a current detection emitter. And
The gate of the protection semiconductor element 41 is the emitter 3 for current detection.
And the current detection resistor 51, and the gate of the protection semiconductor element 42 is connected between the current detection resistors 51 and 52. The protection semiconductor elements 41 and 42 are connected in parallel between the gate and the emitter of the semiconductor element 1. The protection semiconductor elements 41 and 42 may have different characteristics. However, if the protection semiconductor elements 41 and 42 have the same characteristic, when a short-circuit current flows, the protection semiconductor element 41 is first turned on, and then the protection semiconductor element 41 is turned on. Semiconductor element 42 becomes conductive.
When the protective semiconductor element is turned on stepwise, the gate voltage of the semiconductor element 1 can be narrowed down stepwise, and the short-circuit current can be suppressed stepwise accordingly.

In FIG. 2, current detecting resistors 53, 5
4 are connected to different current detecting emitters 33 and 34, respectively.
Forty-four gates are connected. For this reason, the constants of the current detecting resistors 53 and 54 connected to the protective semiconductor elements 43 and 44, respectively, are selected so that the protective semiconductor elements 43 and 44 are not simultaneously turned on. By conducting the elements 43 and 44 stepwise, the same effect as in the case of FIG. 1 can be obtained.

FIG. 4 shows an example of waveforms in the embodiment shown in FIGS. 4A shows the collector current, FIG. 4B shows the voltage between the collector and the emitter, FIG. 4C shows the voltage between the gate and the emitter, and the solid lines in FIGS. In the case of the circuit, the dotted line is shown in FIG.
This is the case of the circuit of FIG.

[0008]

According to the present invention, when a circuit to which a semiconductor element is connected is short-circuited, the short-circuit current is narrowed down stepwise to prevent element destruction due to an excessive current and to prevent generation of an induced voltage due to circuit inductance. It is possible to provide an effect of preventing the element breakdown caused by the pressing and the voltage.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

FIG. 2 is a circuit diagram showing another embodiment of the present invention.

FIG. 3 is a circuit diagram showing an example of conventional short-circuit protection.

FIG. 4 is a diagram showing an operation waveform (solid line) in FIGS. 1 and 2 and an operation waveform (dotted line) in FIG. 3;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Semiconductor element, 2 ... Emitter, 3, 33, 34 ... Emitter for current detection, 4, 41, 42, 43, 44 ... Semiconductor element for protection, 5, 51, 52, 53, 54 ... Resistance for current detection, 6 ... Gate resistance.

Claims (2)

[Claims] In a short-circuit protection circuit for a semiconductor device in which a gate and a collector are used in common and a part of an emitter is separated and used as a current detection emitter, a plurality of current detection resistors are connected in series to the current detection emitter. The gates of the plurality of protection semiconductor elements are connected to one ends of the current detection resistors, respectively, and the drains (collectors) of the protection semiconductor elements are connected.
A short-circuit protection circuit for a semiconductor element, wherein a circuit is connected to a gate of the semiconductor element, and a source (emitter) of the semiconductor element for protection is connected to an emitter of the semiconductor element. 2. A short-circuit protection circuit for a semiconductor device in which a gate and a collector are used in common and a part of an emitter is separated to be used as a plurality of emitters for current detection. The gates of the plurality of protective semiconductor elements are connected to one end of the current detection resistor, the drain (collector) of the protective semiconductor element is connected to the gate of the semiconductor element, and the source (emitter) of the protective semiconductor element is connected to the emitter. A short-circuit protection circuit for a semiconductor device, wherein the short-circuit protection circuit is connected to an emitter of the semiconductor device.