JPH10145206A - Protective circuit for semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the vibration of current that flows through a semiconductor active element at the time of a protective operation. SOLUTION: Current flows to a main IGBT 10 and a detection IGBT 18 according to a gate voltage, the gate voltage turns on a transistor 24 and turns off a transistor 22 at the time of normal operation, and the transistor 24 short- circuits both ends of an auxiliary detecting resistance 28. When the current of the IGBT 10 is increased by load short circuit, etc., the current of the IGBT 18 is increased. When the detected voltage of a detective resistance 26 exceeds a threshold voltage of a transistor 22, the transistor 22 is turned on, a gate voltage of an A point falls and the current of the IGBTs 10 and 18 reduces. When a gate voltage of the A point becomes below the threshold voltage of the transistor 24, the transistor 24 is turned on and the resistance 28 is connected to the resistance 26. As a result, the resistance value of detection resistance is raised, the gate voltage of the transistor 22 rises and a drop of the gate voltage of the A point is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a protection circuit for a semiconductor device, and more particularly, to a semiconductor device adapted to an inverter used as a power converter in various electric products such as electric locomotives and home electric appliances. The present invention relates to a protection circuit for a semiconductor device having a protection function for protection.

[0002]

2. Description of the Related Art In recent years, as a semiconductor active element constituting an inverter, a power field effect transistor (hereinafter referred to as a voltage control element) has been replaced by a current control element such as a bipolar transistor or a gate turn-off thyristor (GTO thyristor). , MOSFETs) and insulated gate bipolar transistors (hereinafter, referred to as IGBTs) have been widely used. Voltage-controlled semiconductor active devices are rapidly being replaced by current-controlled semiconductor active devices because of their ease of driving and high-speed operation. Among them, IGBTs are being actively developed as new switching elements having both the large power controllability of bipolar transistors and the high-speed operation of MOSFETs.

When an IGBT is applied to an inverter,
Indispensable are various protection functions. As this protection function, protection functions such as overcurrent protection, overtemperature protection, and overvoltage protection have been proposed and put into practical use. Of these protection functions, particularly important is overcurrent protection. That is, when a load connected to the inverter is short-circuited, or when a so-called arm short-circuit occurs in which the IGBTs of the upper and lower arms of the inverter are simultaneously turned on, an excessive current flows through the IGBT and I
The GBT may be instantaneously destroyed, requiring an overcurrent protection circuit.

As a basic overcurrent protection circuit, for example, an overcurrent detection IGBT which is connected in parallel with the main IGBTs forming the upper and lower arms and detects an overcurrent of the main IGBT,
A detection resistor connected to the emitter of the overcurrent detection IGBT to detect an overcurrent; a MOSFET connected to the gate and the emitter of the overcurrent detection IGBT to limit a gate voltage according to the voltage of the emitter; an IGBT for overcurrent detection There is known a device provided with a gate resistor for applying a gate voltage to the gate. In this type of overcurrent protection circuit, during normal operation of the main IGBT, current flows through each IGBT in accordance with the gate voltage applied to the gate electrode. It is set so that a detection current of about 1/1000 to 1/10000 flows. During normal operation, since the detection voltage generated from the detection resistor by the detection current is small, the MOSFET is maintained in the off state, and each IGBT is turned off.
, The gate voltage is applied as it is.

On the other hand, when an accident such as a load short circuit or arm short circuit occurs and an excessive current flows through the main IGBT, the detection current flowing through the overcurrent detection IGBT also increases, and the detection voltage across the detection resistor increases. When this detection voltage exceeds the threshold voltage of the MOSFET, the MOSFET is turned on and the gate voltage is divided by the gate resistance and the MOSFET,
The voltage applied to the gate of each IGBT is reduced.
When the gate voltage of each IGBT decreases, the current of each IGBT decreases, and the main IGBT can be protected from destruction due to overcurrent. Japanese Patent Application Laid-Open No. 6-132354 is related to this type of technology.

[0006]

However, in the conventional overcurrent protection circuit, when the collector current of the main IGBT exceeds a certain current value, the protection circuit operates to suppress an increase in the collector current of the main IGBT. However, when the overcurrent protection circuit operates, the collector current of the main IGBT oscillates, and noise occurs with the oscillation of the collector current, causing a failure in peripheral devices or when the vibration is severe, the main IGBT is activated. It may be destroyed. That is, when the overcurrent protection circuit operates, the main current flowing through the main IGBT and the detection current flowing through the IGBT for overcurrent detection both decrease as the gate voltage of each IGBT decreases, but when the detection current decreases, the detection current decreases. The voltage also decreases, and the operation of the overcurrent protection circuit is weakened. When the operation of the overcurrent protection circuit is weakened, the operation of the overcurrent protection circuit is not stabilized due to feedback that the potential of the gate voltage of each IGBT increases and the main current and the detection current increase again. Oscillation occurs in the collector current.

SUMMARY OF THE INVENTION An object of the present invention is to provide a protection circuit for a semiconductor device capable of preventing a current flowing through a semiconductor active element to be protected from oscillating during a protection operation, and a power converter using the protection circuit. Is to do.

[0008]

In order to achieve the above object, the present invention provides a semiconductor device having a main semiconductor active element whose conduction current is controlled in accordance with a control voltage. A sub-semiconductor active element, the conduction current of which is controlled in accordance with a control voltage applied to the main semiconductor active element, and a current-to-voltage converter for detecting the current of the sub-semiconductor active element and converting the detected current into a voltage; An overcurrent protection means for reducing the current flowing through the master-slave semiconductor active element when the conversion voltage of the current-voltage conversion means exceeds a set value in accordance with an increase in the conversion voltage of the current-voltage conversion means; Conversion voltage control means for increasing the conversion voltage of the current-voltage conversion means in response to a decrease in the current flowing through the master and slave semiconductor active elements when the control voltage falls below the set value. It is obtained by the circuit.

In forming the protection circuit of the semiconductor device, a current-voltage conversion means for converting a current flowing through a slave semiconductor active element into a voltage corresponding to a resistance value may be used. When the control voltage applied to the semiconductor active element becomes equal to or less than the set value, the resistance value of the current-to-voltage conversion means is increased in accordance with the decrease in the current flowing through the master and slave semiconductor active elements. It is also possible to use a device that increases the resistance value of the current-to-voltage converter when the applied control voltage falls below the set value.

According to another aspect of the present invention, there is provided a semiconductor device having a main semiconductor active element whose conduction / non-conduction is controlled according to a control voltage, wherein the semiconductor device is connected in parallel with the main semiconductor active element and applied to the main semiconductor active element. A sub-semiconductor active element whose conduction / non-conduction is controlled according to the control voltage, current-to-voltage conversion means for detecting the current of the sub-semiconductor active element and converting the detected current to a voltage, and a conversion voltage of the current-to-voltage conversion means Voltage control means for decreasing the control voltage applied to the master-slave semiconductor active element when the voltage exceeds the value according to the increase of the conversion voltage of the current-voltage conversion means; and the control voltage applied to the slave semiconductor active element being equal to or less than a set value. And a conversion voltage control means for increasing the conversion voltage of the current-to-voltage conversion means in response to a decrease in the control voltage applied to the master-slave semiconductor active element when the semiconductor device becomes a protection circuit. Those were.

In forming the protection circuit of the semiconductor device, a current-voltage converting means for converting a current flowing through the active element of the slave semiconductor into a voltage corresponding to a resistance value may be used. When the control voltage applied to the active element becomes equal to or less than the set value, the resistance of the current-voltage conversion means is increased according to the decrease in the control voltage applied to the master-slave semiconductor active element, or
It is also possible to use a device that increases the resistance value of the current-voltage conversion means when the control voltage applied to the slave semiconductor active element falls below the set value.

In configuring the protection circuit of each of the semiconductor devices, the following elements can be added.

(1) At least the main semiconductor active element among the semiconductor active elements is constituted by an insulated gate semiconductor active element.

(2) The main semiconductor active element, the auxiliary semiconductor active element, the current-to-voltage conversion means, the voltage control means and the converted voltage control means are formed in the same semiconductor substrate.

[0015] The protection circuit of any one of the above semiconductor devices includes:
A plurality of main semiconductor active elements which are inserted between a pair of DC input terminals and the same number of AC output terminals as the number of phases to form upper and lower arms having the same number of phases, and anti-parallel to each main semiconductor active element The present invention can be applied to a power converter including a plurality of connected rectifiers.

According to the above-mentioned means, when the control voltage is applied to the main semiconductor active element and the sub semiconductor active element, the current flowing through the main semiconductor active element and the sub semiconductor active element is controlled according to the magnitude of the control voltage. Is done. Then, when an abnormality or the like occurs in a circuit connected to the main semiconductor active element and the current flowing through the main semiconductor active element increases, the current flowing through the slave semiconductor active element also increases, and the conversion voltage by the conversion of the current-voltage conversion means increases. . When the converted voltage exceeds a set value (threshold voltage), the overcurrent protection means or the voltage control means operates, and the current flowing through the master / slave semiconductor active element or the control voltage applied to the master / slave semiconductor active element decreases. The current flowing through the semiconductor active element and the slave semiconductor active element decreases, and the conversion voltage decreases. At this time, on condition that the conversion voltage of the current-voltage conversion means exceeds the set value, the conversion voltage control means functions, the conversion voltage or resistance value of the current-voltage conversion means is increased, and the current flowing through the slave semiconductor active element is increased. The conversion voltage of the current-voltage conversion means is prevented from lowering with the decrease in the voltage, and the operation state of the protection circuit is maintained. Therefore, it is possible to prevent the main current from oscillating due to a change in the main current during the operation of the protection circuit, and to enhance the reliability of the semiconductor device.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing a protection circuit of a semiconductor device according to an embodiment of the present invention. In FIG. 1, as a semiconductor device, for example, a main IGBT (insulated gate bipolar transistor) 10 forming an arm of an inverter is provided, and an emitter of the main IGBT 10 is connected to an emitter electrode 12 and a collector is connected to a collector electrode 14. ing. An overcurrent protection circuit 16 is provided to protect the main IGBT 10 from overcurrent. The overcurrent protection circuit 16 includes a detection IGBT 18, a gate resistor 20, transistors 22 and 24 formed of N-type MOSFETs, a detection resistor 26, and an auxiliary detection resistor 28. The detection IGBT 18 is connected in parallel with the main IGBT 10 which is the main semiconductor active element as a slave semiconductor active element, and has a collector connected to the collector electrode 14, a gate connected to the gate of the main IGBT 10, and a gate resistor 20. Through the gate electrode 30
And the emitter is connected to the detection resistor 26 and the transistor 2
2 gates. The transistor 22 has a drain connected to the gate of the detection IGBT 18 and a source connected to the emitter electrode 12. The transistor 22 is turned on only when the gate voltage exceeds a threshold voltage (set value), reduces the gate voltage (control voltage) at the point A, and detects the current (main current) flowing through the main IGBT 10 as the current. The IGBT 18 is configured as an overcurrent protection unit that reduces the conduction current (detection current) of the IGBT 18 and a voltage control unit that reduces the level of the gate voltage at the point A according to the gate voltage. The detection resistor 26 is connected in series to the emitter and the emitter electrode 12 of the detection IGBT 18 together with the auxiliary detection resistor 28, and constitutes a current-to-voltage conversion means for detecting a current flowing through the detection IGBT 18 and converting this detection voltage into a voltage. And a current-to-voltage converter for converting the detected current into a voltage corresponding to the resistance value. The transistor 24 has a drain connected to a connection point between the detection resistor 26 and the auxiliary detection resistor 28, a source connected to the emitter electrode 12, and a gate connected to the gate of the detection IGBT 18. This transistor 24 has a detection IG
When a gate voltage (a voltage exceeding the threshold voltage) at which the BT 18 is turned on is applied to the point A, the BT 18 is turned on to short-circuit both ends of the auxiliary detection resistor 28, and the gate voltage at the point A falls below the threshold voltage. It turns off when it becomes
A conversion voltage control means for increasing the emitter voltage (conversion voltage of the current-to-voltage conversion means) of the detection IGBT 18 by inserting the auxiliary detection resistor 28 into the emitter circuit of T18 and a conversion voltage control for increasing the resistance value of the current-to-voltage conversion means Means.

In the above structure, the gate electrode 30 has the main I
When a gate voltage for driving the GBT 10 is applied, the gate voltage is applied via the gate resistor 20 to the main IGB.
The main IG is applied to T10 and the gate of the detection IGBT 18.
A main current flows through the BT 10 and a detection current flows through the detection IGBT 18. This detected current is 1/1000 to 1/1 / the main current.
It is set to a value of about 10,000. And the main IGB
When the circuit connected to T10 is in a normal state, the voltage detected by the detection resistor 26 is smaller than the threshold voltage, and the transistor 22 is kept off. On the other hand, the transistor 24 is turned on because a voltage exceeding the threshold voltage is applied to the gate, and the auxiliary detection resistor 28 is short-circuited by the transistor 24.

Next, an accident such as a load short-circuit or an arm short-circuit occurs in a circuit to which the main IGBT 10 is connected, and
When an excessive main current flows through the GBT 10, the detection IGBT 1
8 also increases, and the detection voltage by the detection of the detection resistor 26 also increases. And the detection voltage is the transistor 22
When the threshold voltage is exceeded, the transistor 22 is turned on, and the gate voltage at the point A decreases. This gate voltage decreases according to the magnitude of the detection voltage applied to the gate of the transistor 22. When the gate voltage at the point A decreases, the main current of the main IGBT 10 and the current of the detection IGBT 18 also decrease as the gate voltage decreases. When the gate voltage at the point A decreases and the gate voltage falls below the threshold voltage of the transistor 24, the transistor 24 is turned off. When the transistor 24 is turned off, the detection IGB
The emitter resistance (detection resistance) of T18 becomes a value obtained by adding the resistance value of the auxiliary detection resistance 28 to the resistance value of the detection resistance 26, and the resistance value of the detection resistance is increased. Therefore, the gate voltage Vs applied to the gate of the transistor 22 is increased, and the gate voltage at the point A is prevented from sharply decreasing. As a result, the operation state of the protection circuit can be maintained during the operation of the overcurrent protection circuit 16, and the feedback of the reduction of the main current and the detection current, the slowdown of the operation of the overcurrent protection circuit 16, and the increase of the main current can be achieved. The vibration of the main current can be prevented, and the occurrence of noise due to the vibration of the main current can be prevented.

Next, a second embodiment of the present invention will be described with reference to FIG.

In this embodiment, the transistor 2 shown in FIG.
4, a bipolar transistor 32 is provided, and the other configuration is the same as that of FIG.

Transistor 2 composed of MOSFET
If the bipolar transistor 32 is used instead of 4, the impedance when the bipolar transistor 32 is on is smaller than the impedance when the MOSFET is on, so that the short-circuit effect of the auxiliary detection resistor 28 can be enhanced. That is, when both ends of the auxiliary detection resistor 28 are short-circuited by the bipolar transistor 32 in the steady state, both ends of the auxiliary detection resistor 28
This means that the impedance of the detection resistor is lower than T, which means that the detection resistor is short-circuited. Further, since the bipolar transistor 32 has a smaller element size than the transistor 24, the circuit can be downsized.

Next, a third embodiment of the present invention will be described with reference to FIG.

In this embodiment, the auxiliary detection resistor 2 shown in FIG.
8 is deleted, and the other configuration is the same as that of FIG.

In this embodiment, the transistor 24
Are connected in series with the detection resistor 26, the resistance value of the detection resistor 26 indicates a main resistance value as a detection resistor during a steady operation, and when the transistor 24 is turned off during a protection circuit operation, the detection resistor 26 The value obtained by adding the resistance value of the high impedance when the transistor 24 is turned off to the resistance value indicates the resistance value of the detection resistor. That is, when the overcurrent protection circuit 16 operates, the transistor 24 is turned off and the impedance becomes high, so that the operation is the same as that in which an auxiliary detection resistor 28 having a very high resistance value is added to the detection resistor 26. For this reason, when a resistor having a very high resistance value is required as the auxiliary detection resistor, it is desirable to use the circuit according to the present embodiment,
Since the auxiliary detection resistor can be omitted as compared with the configuration shown in FIG. 1, the circuit configuration can be simplified.

Overcurrent protection circuit 1 in each of the above embodiments
6 is mounted on the substrate of the semiconductor device.
It is desirable that the circuit except the GBT 18 be integrated into a single semiconductor chip to form a protection circuit chip, the detection IGBT 18 be a IGBT with a sense cell, and be implemented by a combination of the IGBT with a sense cell and the protection circuit chip. With this configuration, the number of components can be reduced as compared with the case where the protection circuit is configured by a combination of discrete elements, and cost reduction and miniaturization can be achieved. Further, a specific element of the protection circuit chip can be formed as a single element as required. For example, only the gate resistor 20 is formed as a single element, and other circuit elements are integrated on one semiconductor chip. By adopting such a configuration, the degree of freedom in design can be increased.

Next, FIG. 4 shows a layout of an IGBT chip in which the overcurrent protection circuit 16 according to the present invention is integrated.
FIG. 5 is a sectional view taken along line XY of FIG. In FIG. 4, one semiconductor chip includes a gate pad 701, an emitter pad 702, an overcurrent protection circuit formation region 703, a gate wiring 704, a current conduction region 705, and a breakdown voltage holding region 7.
06 is formed. The gate pad 701 is formed as a region for connecting a wire from a gate drive circuit outside the chip.
It is connected to the. The emitter pad 702 is formed as a region for connecting a wiring from a main circuit outside the chip, and this emitter pad 702 is connected to the emitters of the main IGBT 10 and the detection IGBT 18. Various elements constituting the overcurrent protection circuit 16 are formed in the overcurrent protection circuit formation area 703. Gate wiring 704
Are formed around the overcurrent protection circuit formation region 703 and around the current conduction region 705 in order to distribute the gate voltage applied to the gate pad 701 to the conduction region. The current conduction region 705 is formed as a region for passing a current of the main circuit, and a plurality of main IGBTs are formed in this region.
10 are formed. The withstand voltage holding region 706 is formed around the semiconductor chip as a region necessary for holding the withstand voltage of the element.

The collector electrode 14 connected to the collector of each of the IGBTs 10 and 18 is formed on the semiconductor substrate as a collector electrode 827 as shown in FIG. On the collector electrode 827, a collector layer 801, a buffer layer 802, and a drift layer 803 are formed. On the drift 803, electrodes and layers constituting the main IGBT 10, the detection IGBT 18, the gate resistor 20, the detection resistor 26, and the like are formed. Have been. Of the elements constituting each element, 805 is p +
806, an emitter layer; 807, a gate insulating film;
8 is a gate electrode, 809 is an oxide film, 810 is a blocking layer, 8
11 is a MOSFET base layer, and 812 is a MOSFETp.
+ Layer, 813 is a source layer, 814 is a drain layer, 815
Is a MOSFET gate electrode, 816 is a field oxide film, 817 is a well layer, 818 is a polycrystalline silicon resistance layer, 820 is an emitter electrode, and 821 is a detection IGBT 18
822 is a source electrode, 823 is a drain electrode, 824 and 825 are polycrystalline silicon resistance electrodes,
Reference numeral 826 denotes a gate pad connected to the gate pad 701. Each element is formed of a wiring made of metal or polycrystalline silicon, and forms an overcurrent protection circuit 16.

According to the present embodiment, the overcurrent protection circuit 16
By integrating each element in the IGBT chip, the overcurrent protection circuit 16 can be downsized. Further, since the distance between the main IGBT 10 to be protected and the overcurrent protection circuit 16 can be arranged close to each other, a signal transmission delay due to wiring can be reduced, and a quick and accurate overcurrent protection operation can be performed. Can be performed.

Next, the configuration of an inverter as a power converter to which the overcurrent protection circuit 16 according to the present invention is applied is shown in FIG.
It is explained according to.

In FIG. 6, the inverter includes a pair of DC input terminals 401 and 402, and AC output terminals 403, 404 and 405 as three-phase output terminals. The DC input terminals 401 and 402 and the AC output terminal 403 are provided. To 405, upper arm 410, 412, 414, lower arm 41
1, 413, 415 and return diodes 416 to 421 are provided. Upper arm 410-414 and lower arm 4
11 to 415 are connected in series, and the series connection points are connected to the AC output terminals 403, 404, and 405, respectively. The upper arm 410 and the lower arm 411 constitute an inverter unit, and the upper arm 412 and the lower arm 4
13 constitutes an inverter unit, and the upper arm 414 and the lower arm 415 constitute an inverter unit.
414 and the lower arms 411 to 415 are connected in reverse parallel to the return diodes 416 to 421. Upper arm 41
0 to 414 and the lower arms 411 to 415 are main IG
The IGBT 10 includes a BT 10 and an overcurrent protection circuit 16, and converts the DC power applied to the DC input terminals 401 and 402 into three-phase AC power when the main IGBT 10 of each arm conducts in a specified order. AC output terminal 40
3 to 405.

In the inverter according to the present embodiment, the overcurrent protection circuit 16 is provided in the main IGBT 10 of each arm. Therefore, even if the load of the inverter is short-circuited or the arm is short-circuited, the circuit element of the arm is replaced. It is possible to protect against overcurrent and to prevent noise from occurring during the protection operation. This prevents peripheral devices from malfunctioning due to noise generated by the inverter when the protection circuit operates, and eliminates the need to attach a filter circuit or shielding plate to the peripheral devices to reduce noise, thereby reducing costs. Can be contributed to.

In each of the above-described embodiments, the case where the IGBT is used as the main semiconductor active element and the slave semiconductor active element is described. However, the present invention is not limited to the IGBT, and other semiconductor active elements can be used. For example, a MOSFET or a bipolar transistor can be used instead of the IGBT.

As the overcurrent protection circuit 16, FIG.
In addition to the circuit configuration shown in FIG. 3, circuit elements such as resistors, diodes, and capacitors can be added to these circuits. For example, a resistor is inserted in series with the transistors 22 and 24 to adjust the gate voltage of each transistor 22 and 24, or to connect the gate of the main IGBT 10 and the detection IGB.
A resistor can be inserted between the gate of T18 and the operation of the gate to provide a time difference. Further, a diode can be used instead of the detection resistor 26. In this case, a configuration in which the voltage generated in the diode increases as the gate voltage decreases, for example, a configuration in which the number of series detection diodes is increased is desirable. Further, it is desirable to adopt a configuration in which the detection current increases as the gate voltage of the IGBT 18 decreases.

[0036]

As described above, according to the present invention,
When an overcurrent flows through the main semiconductor active device to be protected, the control voltage applied to the subordinate semiconductor active device is reduced, and the control voltage is gradually reduced so that the current of the main semiconductor active device is reduced from the overcurrent. The current of the main semiconductor active element can be prevented from oscillating when the protection circuit operates, and the circuit element can be prevented from being damaged by noise due to the oscillation. And contribute to improvement in reliability.

[Brief description of the drawings]

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

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

FIG. 3 is a circuit diagram showing a third embodiment of the present invention.

FIG. 4 is a layout configuration diagram of an IGBT chip when an overcurrent protection circuit according to the present invention is integrated.

FIG. 5 is a sectional view taken along the line XY in FIG. 4;

FIG. 6 is a block diagram of an inverter to which an overcurrent protection circuit according to the present invention is applied.

[Explanation of symbols]

 Reference Signs List 10 main IGBT 16 overcurrent protection circuit 18 detection IGBT 20 gate resistance 22, 24 transistor (MOSFET) 26 detection resistance 28 auxiliary detection resistance

Claims (9)

[Claims] 1. A semiconductor device having a main semiconductor active element whose conduction current is controlled in accordance with a control voltage, wherein the semiconductor device is connected in parallel with the main semiconductor active element and in accordance with a control voltage applied to the main semiconductor active element. A sub-semiconductor active element in which a conduction current is controlled, current-voltage conversion means for detecting the current of the sub-semiconductor active element and converting the detected current into a voltage, and a main-slave when the conversion voltage of the current-voltage conversion means exceeds a set value. Overcurrent protection means for reducing the current flowing through the semiconductor active element in accordance with an increase in the conversion voltage of the current-voltage conversion means; and a master-slave semiconductor active element when the control voltage applied to the slave semiconductor active element falls below a set value. And a conversion voltage control means for increasing the conversion voltage of the current-voltage conversion means in response to a decrease in the current flowing through the semiconductor device. 2. A semiconductor device comprising: a main semiconductor active element whose conduction current is controlled according to a control voltage;
A sub-semiconductor active element in which the conduction current is controlled according to a control voltage applied to the main semiconductor active element in parallel with the main semiconductor active element, and a current flowing in the sub-semiconductor active element is converted into a voltage according to a resistance value. Current-to-voltage conversion means, and overcurrent protection means for decreasing the conduction current of the master-slave semiconductor active element as the conversion voltage of the current-to-voltage conversion means increases when the conversion voltage of the current-to-voltage conversion means exceeds a set value, A conversion voltage control means for increasing the resistance value of the current-to-voltage conversion means in accordance with a decrease in the current flowing through the master-slave active element when the control voltage applied to the slave semiconductor active element falls below a set value; Equipment protection circuit. 3. A semiconductor device having a main semiconductor active element whose conduction current is controlled in accordance with a control voltage, wherein the semiconductor device is connected in parallel with the main semiconductor active element and in accordance with a control voltage applied to the main semiconductor active element. A sub-semiconductor active element whose energizing current is controlled, current-to-voltage conversion means for converting a current flowing through the sub-semiconductor active element to a voltage corresponding to a resistance value, and a conversion voltage of the current-to-voltage conversion means exceeding a set value. Overcurrent protection means for reducing the current flowing through the master-slave active element as the converted voltage of the current-voltage conversion means increases; and current-voltage conversion when the control voltage applied to the slave semiconductor active element falls below a set value. And a conversion voltage control means for increasing the resistance value of the means. 4. A semiconductor device having a main semiconductor active element and a child whose conduction / non-conduction is controlled in accordance with a control voltage, wherein a control applied in parallel to the main semiconductor active element and applied to the main semiconductor active element. A semiconductor active element whose conduction / non-conduction is controlled according to the voltage, current-voltage conversion means for detecting the current of the slave semiconductor active element and converting the detected current to a voltage, and a conversion voltage of the current-voltage conversion means having a set value. Voltage control means for decreasing the control voltage applied to the master-slave semiconductor active element when the conversion voltage of the current-voltage conversion means increases when the voltage exceeds the control voltage, and the control voltage applied to the slave semiconductor active element falls below a set value. A protection circuit for a semiconductor device, comprising: conversion voltage control means for increasing a conversion voltage of a current-voltage conversion means in response to a decrease in a control voltage applied to a master-slave semiconductor active element. 5. A semiconductor device having a main semiconductor active element whose conduction / non-conduction is controlled according to a control voltage, wherein a control voltage applied to the main semiconductor active element connected in parallel with the main semiconductor active element is controlled. A semiconductor active element whose conduction / non-conduction is controlled in response thereto, current-voltage conversion means for converting a current flowing through the slave semiconductor active element into a voltage corresponding to a resistance value, and a conversion voltage of the current-voltage conversion means having a set value. Voltage control means for decreasing the control voltage applied to the master-slave semiconductor active element when the voltage exceeds the control voltage according to the increase of the conversion voltage of the current-voltage conversion means; and the control voltage applied to the slave semiconductor active element becomes equal to or less than a set value. And a conversion voltage control means for increasing the resistance value of the current-to-voltage conversion means in response to a decrease in the control voltage applied to the master and slave semiconductor active elements. 6. A semiconductor device having a main semiconductor active element whose conduction / non-conduction is controlled according to a control voltage, wherein a control voltage applied to the main semiconductor active element connected in parallel with the main semiconductor active element is provided. A semiconductor active element whose conduction / non-conduction is controlled in response thereto, current-voltage conversion means for converting a current flowing through the slave semiconductor active element into a voltage corresponding to a resistance value, and a conversion voltage of the current-voltage conversion means having a set value. Voltage control means for decreasing the control voltage applied to the master-slave semiconductor active element when the voltage exceeds the control voltage according to the increase of the conversion voltage of the current-voltage conversion means; and the control voltage applied to the slave semiconductor active element becomes equal to or less than a set value. And a conversion voltage control means for increasing the resistance value of the current-to-voltage conversion means. 7. The protection circuit for a semiconductor device according to claim 1, wherein at least the main semiconductor active element of the semiconductor active elements is constituted by an insulated gate semiconductor active element. . 8. The semiconductor device according to claim 1, wherein the main semiconductor active element, the slave semiconductor active element, the current-voltage conversion means, the voltage control means and the converted voltage control means are formed in the same semiconductor substrate. 8. The protection circuit for a semiconductor device according to claim 7. 9. A plurality of main semiconductor active elements inserted between a pair of DC input terminals and an AC output terminal having the same number of phases to form upper arms and lower arms as the number of phases, and A power converter comprising a plurality of rectifiers connected in anti-parallel to an active element, comprising: the protection circuit for a semiconductor device according to claim 1. Conversion device.