JPH0883906A - Semiconductor device - Google Patents

Abstract

PURPOSE: To prevent generation of latch-up even if gate voltage is heightened to drive IGBT by almost equalizing voltage to be impressed between a gate and a source of IGBT to a difference between gate voltage of IGBT to be impressed from outside and voltage between the in and output terminals of a nonlinear element. CONSTITUTION: High voltage is impressed on a gate 1 of IGBT so as to perform low loss drive. Further, MOSFET 2 as nonlinear elements are in series connected to a source of IGBT 1 so as to make the same current flow. When an overcurrent flow to IGBT 1, voltage between a drain and a source of MOSFET 2 increases suddenly. At this time, voltage between a drain and a source of IGBT 1 becomes that where voltage between a drain and a source of MOSFET 2 is substructed from gate voltage of IGBT 1. Accordingly, even if the overcurrent flows to IGBT 1, voltage between the gate and the source of IGBT 1 automatically lowers so as to prevent generation of latch-up.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device for protecting an IGBT from overcurrent.

[0002]

2. Description of the Related Art An IGBT (Insulated Gate Bipolar Transistor) is one of the insulated gate high withstand voltage semiconductor elements.
). The IGBT is a new high breakdown voltage semiconductor device having both the high speed switching characteristics of a power MOSFET and the high output characteristics of a bipolar transistor.
It is widely used in the field of power electronics such as inverters and switching power supplies.

By the way, the characteristic (VI characteristic) between the drain-source voltage and the drain-source current of the IGBT is greatly influenced by the gate voltage, and the on-voltage decreases as the gate voltage increases. Therefore, when the IGBT is driven by increasing the gate voltage, low loss driving becomes possible.

However, in this case, the saturation current of the IGBT becomes high, and a large current (overcurrent) exceeding the latch-up current flows. Therefore, increase the gate voltage to increase the IG
When an overcurrent flows through the IGBT when the BT is driven,
There is a problem that the IGBT latches up and, in the worst case, the IGBT is destroyed.

[0005]

As described above, when the gate voltage is increased and the IGBT is driven with low loss, the IGBT is
There is a problem that the IGBT latches up when an overcurrent flows through the IGBT. The present invention has been made in consideration of the above circumstances, and an object thereof is to provide a semiconductor provided with an IGBT that can effectively prevent latch-up even if the IGBT is driven by increasing the gate voltage. To provide a device.

[0006]

In order to achieve the above object, a semiconductor device of the present invention comprises an IGBT and an IGBT.
A non-linear element having an input terminal connected to the source of T and serially connected to the IGBT, wherein the non-linear element causes the voltage between the input and output terminals to become non-linear as the current flowing between the input and output terminals increases. It is an increasing element, and the voltage applied between the gate and the source of the IGBT is substantially equal to the difference between the gate voltage of the IGBT applied from the outside and the voltage between the input and output ends of the nonlinear element. It is characterized by having done.

[0007]

According to the present invention, since the non-linear element is connected in series to the IGBT, the same current flows through the IGBT and the non-linear element, and the gate-source voltage of the IGBT at this time is the gate of the IGBT. It is the voltage minus the voltage between the input and output ends of the nonlinear element.

Therefore, even if an overcurrent flows, the gate
Since the source-to-source voltage is reduced by the voltage between the input and output ends of the non-linear element, the latch-up of the IGBT is prevented.

Here, if a non-linear element having a characteristic in which the voltage between the input and output ends sharply increases when an overcurrent flows, the occurrence of latch-up of the IGBT can be effectively prevented.

[0010]

Embodiments will be described below with reference to the drawings. 1 is a diagram showing a semiconductor device according to a first embodiment of the present invention. This semiconductor device protects the IGBT from overcurrent.

In the figure, reference numeral 1 denotes an IGBT.
A high voltage (for example, 20 V) is applied to the gate of the GBT to drive it with low loss. Further, the source of the IGBT 1 has a MOS as a non-linear element.
FET2 is connected, and MOS is connected to IGBT1.
FET2 is connected in series, IGBT1 and MOSFET
The same current as 2 flows.

A power supply 5 is connected to the gate of the MOSFET 2.
Is provided, and a predetermined gate voltage is applied to the gate, as described later. The MOSFET 2 may have a low breakdown voltage. In the figure, 3 indicates a power source and 4 indicates a load.

FIG. 2 is a characteristic diagram showing the relationship between the drain-source current I _DS and the drain-source voltage V _DS of the MOSFET 2. As can be seen from FIG.
The drain-source voltage V _DS increases non-linearly as the source current I _DS increases. That is, when the drain-source current _IDS exceeds a certain value (saturation current),
The drain-source voltage V _DS rapidly increases.

This saturation current depends on the voltage (gate voltage) applied to the gate of the MOSFET 2. In this embodiment, the saturation current is an overcurrent of the IGBT,
A gate voltage (predetermined gate voltage) is set by the power supply 5. For example, if the overcurrent is 10 A, the gate voltage is set so that the saturation current is 10 A.

According to the semiconductor device having such a structure, when an overcurrent flows in the IGBT 1, the drain-source voltage V _{DS of the} MOSFET 2 rapidly increases. At this time, since the IGBT1 and the MOSFET2 are connected in series, the gate-source voltage of the IGBT1 is IG
It is the gate voltage of BT1 minus the drain-source voltage V _DS of MOSFET2.

Therefore, even if an overcurrent flows through the IGBT1, the voltage between the gate and the source of the IGBT1 automatically decreases and the saturation current of the IGBT decreases, so that latch-up can be prevented.

Further, according to the above operation principle, when an overcurrent flows, the saturation current of the IGBT becomes small, so that most of the power supply voltage is shared by the load and the IGBT, and the overvoltage is not applied to the MOSFET of the nonlinear element. Absent. Therefore, the non-linear element may be a low breakdown voltage element having a lower breakdown voltage than the IGBT 1.

FIG. 3 is a diagram showing a semiconductor device according to the second embodiment of the present invention. The parts corresponding to those of the semiconductor device of FIG. 1 are designated by the same reference numerals as those of FIG. 1, and detailed description thereof is omitted.

The semiconductor device of this embodiment is different from that of the previous embodiment in that a bipolar transistor 6 is used as a non-linear element. According to the present embodiment, by setting the base current of the bipolar transistor 6 so that the saturation current of the collector-emitter current becomes the overcurrent of the IGBT 2, the same effect as the previous embodiment can be obtained.

FIG. 4 is a diagram showing a semiconductor device (voltage type three-phase inverter) according to a third embodiment of the present invention. The voltage-type three-phase inverter of this embodiment is characterized in that the IGBT 1 is used as a main switching element and one nonlinear element is connected to the three IGBTs in the lower stage. In addition,
In the figure, 7 indicates a feedback diode connected in anti-parallel with the IGBT 1.

In this embodiment, as the non-linear element,
Although the MOSFET is used, a bipolar transistor may be used as in the second embodiment. Also, all IG
The present invention may be applied to BT. In the first to third embodiments, the IGBT and the non-linear element may be formed on different substrates, or may be formed on the same substrate and integrated.

[0022]

As described above in detail, according to the present invention, it is possible to realize a semiconductor device capable of effectively preventing the occurrence of latch-up even when the IGBT is driven by increasing the gate voltage.

[Brief description of drawings]

FIG. 1 is a diagram showing a semiconductor device according to a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing the relationship between the drain-source current and the drain-source voltage of a MOSFET (non-linear element).

FIG. 3 is a diagram showing a semiconductor device according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a semiconductor device according to a third embodiment of the present invention.

[Explanation of symbols]

 1 ... IGBT 2 ... MOSFET (non-linear element) 3 ... Power source 4 ... Load 5 ... Power source 6 ... Bipolar transistor (non-linear element) 7 ... Feedback diode

Claims (2)

[Claims] 1. An IGBT and a nonlinear element having an input end connected to a source of the IGBT and connected in series to the IGBT, wherein the nonlinear element increases with an increase in current flowing between input and output ends. An element in which the voltage between the input and output ends increases non-linearly, and the voltage applied between the gate and source of the IGBT is between the gate voltage of the IGBT applied from the outside and the input and output end of the non-linear element. The semiconductor device is characterized in that the difference between the voltage and the voltage is substantially equal. 2. The semiconductor device according to claim 1, wherein the non-linear element is an element having a lower breakdown voltage than an IGBT.