JP2004023638A - Circuit for current controlled semiconductor switch element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit for a current controlled semiconductor switch element for realizing over-voltage protection and overcurrent protection without the need for a Zener diode. <P>SOLUTION: The circuit for a current controlled semiconductor switch element is provided with: a main power transistor 8; a mirror transistor 9 for the main power transistor 8; control means IN, 4, 5, 12, 13 for detecting an over-voltage applied to the main power transistor 8 on the basis of a leakage current supplied to the mirror transistor 9; over-voltage detection means 11, 12, 16 for detecting an over-voltage applied to the main power transistor 8; and overcurrent detection means 11, 12, 15 for detecting an overcurrent flowing through the main power transistor 8 on the basis of a current flowing through the mirror transistor 9, and the control means IN, 4, 5, 12, 13 turn on the main power transistor 8 when the over-voltage state of the main power transistor 8 is detected and turn off the main power transistor 8 when the over-current state of the main power transistor 8 is detected. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a circuit using a current control type semiconductor switching element, and more particularly to a circuit having an overvoltage protection function and an overcurrent protection function.
[0002]
[Prior art]
FIG. 4 shows a circuit for protecting a current control type power transistor from overvoltage or overcurrent. In the circuit shown in FIG. 4A, the control terminal IN, the OR gate 3, the transistor driving power supply 1, the P-type MOSFET 4, the N-type MOSFET 5, the Zener diode 6, the load 7, and the drive of the load 7 are driven. Power supply 2, a main power transistor 8, a mirror transistor 9, a resistor 10, an operation amplifier 11, and a level conversion circuit 12.
[0003]
The circuit shown in FIG. 4A has an overvoltage protection function when the transistor 8 is off and an overcurrent protection function when the transistor 8 is on in addition to the function of driving the transistor 8. In a normal operation in which neither the overcurrent state nor the overvoltage state occurs, when the control terminal IN for controlling the transistor 8 is at the L level (the MOSFET 4 is on and the MOSFET 5 is off), the transistor 8 is on and the control terminal IN is at the H level. In this case (the MOSFET 4 is off and the MOSFET 5 is on), the transistor 8 is turned off.
[0004]
The protection current function of the circuit shown in FIG. It is assumed that some problem occurs in the load 7 while the transistor 8 is on, for example, a short circuit occurs between the collector terminal of the transistor 8 and the power supply 2 and an excessive current flows in the transistor 8. In this case, a current Ices corresponding to the mirror ratio flows through the mirror transistor 9 which is a mirror element for the transistor 8. Therefore, the current Ices also flows through the resistor 10 connected to the emitter terminal of the mirror transistor 9, so that a voltage corresponding to the magnitude of the current Ices is generated at both ends of the resistor 10. The operation amplifier 11 amplifies the voltage applied to both ends of the resistor 10 and inputs the output S1 to the level conversion circuit 12.
[0005]
The voltage level of the overcurrent state is set in the level conversion circuit 12 in advance, and when the input voltage level of S1 exceeds the voltage level of the overcurrent state, an H-level signal S2 is output. When the signal S2 output from the level conversion circuit 12 goes high, the output of the OR gate 3 goes high, as shown in the truth table of FIG. 4B, so that the MOSFET 5 is turned on and the MOSFET 4 Is turned off. That is, even if the output of the control terminal IN is an on command (L level), the transistor 8 is forcibly turned off. Thus, it is possible to prevent the overcurrent from continuously flowing through the transistor 8.
[0006]
Next, the overvoltage protection function will be described. The technology related to the overvoltage protection function is disclosed in Japanese Patent Application Laid-Open No. H11-55937. It is assumed that a high voltage higher than the withstand voltage of the transistor 8 is applied to the collector terminal of the transistor 8 while the transistor 8 is off. When the Zener voltage of the Zener diode 6 is set in advance to be equal to or lower than the withstand voltage of the transistor 8 (referred to as a clamp voltage VceC), when a voltage equal to or higher than the clamp voltage VceC + the base-emitter voltage Vbe is applied to the collector terminal of the transistor 8. The current Id flows through the Zener diode 6 in the direction shown in FIG. Therefore, when the current Id flows through the base terminal of the transistor 8, the transistor 8 is turned on, and a current flows between the collector and the emitter. Thus, the energy of the overvoltage applied to the collector terminal can be consumed, so that the overvoltage can be prevented from being continuously applied to the transistor 8.
[0007]
[Problems to be solved by the invention]
However, when the above-described conventional technique is applied to a power transistor having a very large current capacity, a large current flows through the Zener diode 6 in order to realize an overvoltage protection function, so that the heat generated by the Zener diode 6 increases. There is a problem. In addition, it is very difficult to realize a high Zener voltage of, for example, 400 V from the viewpoints of heat radiation, cost, reliability, and the like.
[0008]
An object of the present invention is to provide a circuit for a current-driven semiconductor switching element that realizes overvoltage protection and overcurrent protection without using a Zener diode.
[0009]
[Means for Solving the Problems]
A current control type semiconductor switching element circuit according to the present invention includes a current control type semiconductor switching element, a mirror element of the current control type semiconductor switching element, a control unit for performing on / off control of the current control type semiconductor switching element, and a mirror. An overvoltage detecting means for detecting an overvoltage applied to the current control type semiconductor switching element based on a leak current flowing to the element; and an overcurrent detecting an overcurrent flowing to the current control type semiconductor switching element based on a current flowing to the mirror element. Control means for turning on the current control type semiconductor switching element when the overvoltage state of the current control type semiconductor switching element is detected by the overvoltage detection means, and controlling the current control type semiconductor switching element by the overcurrent detection means. If an overcurrent condition is detected in the By turning off the switching element, to achieve the above object.
[0010]
【The invention's effect】
According to the circuit for a current control type semiconductor switching element of the present invention, an overvoltage state and an overcurrent state are detected based on a current flowing through a mirror element of the current control type semiconductor switching element, and the current control is performed when the overvoltage state is detected. Since the type semiconductor switching element is turned on and the current control type semiconductor switching element is turned off when an overcurrent state is detected, an overvoltage protection function and an overcurrent protection function can be realized without using a Zener diode.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
First Embodiment FIG. 1A is a diagram showing a configuration of a first embodiment of a circuit for a current-driven semiconductor switching element according to the present invention. The circuit shown in FIG. 1A includes a control terminal IN, an XOR gate 3, a transistor driving power supply 1, a P-type MOSFET 4, N-type MOSFETs 5, 17, a load 7, and a circuit for driving the load 7. The power supply 2 includes a power supply 2, a bipolar transistor (main power transistor) 8, a mirror transistor 9, resistors 15 and 16, an operation amplifier 11, a level conversion circuit 12, and an INV gate 14.
[0012]
During a normal operation that is neither an overcurrent state nor an overvoltage state, when the control terminal IN for controlling the transistor 8 is at the L level, the MOSFET 4 is turned on and the MOSFET 5 is turned off, so that the transistor 8 is turned on. On the other hand, when the control terminal IN is at the H level, the MOSFET 4 is turned off and the MOSFET 5 is turned on, so that the transistor 8 is turned off. The mirror transistor 9 corresponding to the transistor 8 has the same device structure as the transistor 8, and has the same on / off characteristics as the transistor 8. A current corresponding to the mirror ratio flows through the transistor 9. For example, when the mirror ratio is 100: 1, when a current of 100 A flows through the transistor 8, a current of 1 A flows through the mirror transistor 9.
[0013]
FIG. 2 is a diagram showing a leakage current characteristic flowing from the collector terminal to the emitter terminal of the mirror transistor 9 with respect to the collector-emitter voltage Vce of the transistor 8 when the mirror transistor 9 is off. As shown in FIG. 2, the leak current increases as the voltage Vce increases, and when the voltage Vce reaches the breakdown voltage of the transistor 8, a so-called breakdown state occurs, and a large amount of current flows.
[0014]
The resistance values of the resistors 15 and 16, which are connected in parallel to the operational amplifier 11 and have one end connected to the emitter terminal of the mirror transistor 9 and the other end connected to the emitter terminal of the transistor 8, respectively, are expressed by the following equation The relationship holds.
Resistance value of resistance 16 / resistance value of resistance 15 ... (1)
Therefore, when the N-type MOSFET 17 connected in series between the resistor 15 and the emitter terminal of the transistor 8 is turned on, the current flowing through the mirror transistor 9 flows through the resistor 15 having a small resistance value. On the other hand, when the N-type MOSFET 17 is off, all the current flowing through the mirror transistor 9 flows through the resistor 16. Note that the emitter terminal of the transistor 8 is grounded.
[0015]
As will be described later, when an overvoltage state is detected, a voltage applied to both ends of the resistor 16 due to a leak current Ices flowing through the resistor 16 is detected by the operation amplifier 11, so that a sufficient voltage can be input even with the leak current. In addition, the resistance value of the resistor 16 needs to be large. The resistor 15 is used for detecting an excessive current state, as described later. However, it is necessary to use a resistor having an appropriate value so that an appropriate voltage is input to the operation amplifier 11. That is, it is necessary to set appropriate resistance values of the resistors 15 and 16 in consideration of the withstand voltage of the transistor 8 and the like.
[0016]
A signal whose signal level at the control terminal IN is inverted by the INV gate 14 is input to the gate of the N-type MOSFET 17. Therefore, when the control terminal IN is at the L level, the N-type MOSFET 17 is turned on, and when the control terminal IN is at the H level, the N-type MOSFET 17 is turned off.
[0017]
The operation amplifier 11 amplifies a voltage applied to both ends of the resistor 15 or the resistor 16 and outputs the amplified voltage to the level conversion circuit 12. When the N-type MOSFET 17 is off, the voltage applied to the resistor 16 is input to the operation amplifier 11. When the N-type MOSFET 17 is on, a voltage applied to both ends of the resistor 15 is input to the operation amplifier 11. The level conversion circuit 12 outputs an H level signal when the input voltage signal exceeds a preset clamp voltage VceC level.
[0018]
FIG. 1B is a truth table of the XOR gate 13. The XOR gate 13 receives the signal of the control terminal IN and the output signal S2 of the level conversion circuit 12, and outputs a logical sum S3. During a normal operation that is neither an overcurrent state nor an overvoltage state, the output signal S2 of the level conversion circuit 12 is at the L level. Therefore, as shown in FIG. 1B, when the control terminal IN is at the L level, the output S3 of the XOR gate 13 is at the L level and the transistor 8 is turned on. When the control terminal IN is at the H level, the XOR gate The output S3 of the transistor 13 goes high, turning off the transistor 8. Therefore, during normal operation, the transistor 8 turns on / off according to the signal level of the control terminal IN.
[0019]
On the other hand, in the case of an overcurrent state or an overvoltage state, as described later, the output signal S2 of the level conversion circuit 12 becomes H level. Therefore, when the control terminal IN is at the L level, the output S3 of the XOR gate is at the H level, and the transistor 8 is turned off. When the control terminal IN is at the H level, the output S3 of the XOR gate 13 is at the L level, so that the transistor 8 is turned on.
[0020]
−Overvoltage protection function−
In the circuit shown in FIG. 1A, an overvoltage protection function when the transistor 8 is off will be described. It is assumed that a high voltage higher than the withstand voltage of the transistor 8 is applied to the collector terminal of the transistor 8 in a state where the control terminal IN is at the H level and the transistor 8 is off. In this case, since the gate of the N-type MOSFET 17 is at the L level, the MOSFET 17 is off. A leak current Ices according to the collector-emitter voltage of the transistor 8 flows between the collector and the emitter of the mirror transistor 9, but all the leak current Ices flows to the resistor 16 because the MOSFET 17 is off. Note that the magnitude of the leak current Ices depends on the mirror ratio.
[0021]
The operation amplifier 11 amplifies the voltage applied to both ends of the resistor 16 and outputs the operation amplifier output S1 to the level conversion circuit 12. The level conversion circuit 12 outputs an H-level signal S2 when the input signal S1 exceeds a preset withstand voltage of the transistor 8, that is, the clamp voltage VceC level. Therefore, when a high voltage higher than the withstand voltage is applied to the collector terminal of the transistor 8, the output signal S2 of the level conversion circuit 12 becomes H level.
[0022]
Since the H-level signal of the control terminal IN and the H-level signal of the level conversion circuit 12 are input to the XOR gate 13, the gate output S3 is at the L level according to the truth table shown in FIG. It becomes. Therefore, the P-type MOSFET 4 is turned on, the N-type MOSFET 5 is turned off, and a base current flows through the transistor 8, so that a current flows between the collector and the emitter. As a result, the transistor 8 is turned on in spite of the control terminal IN being at the H level (a command to turn off the transistor 8), so that the overvoltage energy applied to the collector terminal of the transistor 8 can be consumed, and the overvoltage is applied to the transistor 8. You can prevent it from continuing.
[0023]
−Overcurrent protection function−
Next, an overcurrent protection function when the transistor 8 is on will be described. In a state where the control terminal IN is at the L level and the transistor 8 is on, a problem occurs in the load 7, for example, a short circuit occurs between the collector terminal of the transistor 8 and the power supply 2, and the current does not flow during normal operation. Suppose that an excessive current flows through the transistor 8. In this case, since the gate of the N-type MOSFET 17 is at the H level, the MOSFET 17 is on.
[0024]
A current Ices corresponding to the mirror ratio flows between the collector and the emitter of the mirror transistor 9. As described above, since the resistance value of the resistor 16 is larger than the resistance value of the resistor 15, the current Ices flows through the resistor 15 when the MOSFET 17 is on. The operation amplifier 11 amplifies the voltage applied to both ends of the resistor 15 and outputs the operation amplifier output S1 to the level conversion circuit 12. The level conversion circuit 12 outputs an H level signal S2 when the input signal S1 exceeds a preset clamp voltage VceC level. That is, when an excessive current flows through the transistor 8, the output signal S2 of the level conversion circuit 12 becomes H level.
[0025]
Since the L-level signal of the control terminal IN and the H-level signal of the level conversion circuit 12 are input to the XOR gate 13, the gate output S3 is at the H-level according to the truth table shown in FIG. It becomes. Therefore, the P-type MOSFET 4 is turned off and the N-type MOSFET 5 is turned on, so that the transistor 8 is forcibly turned off even though the control terminal IN is at the L level (on command of the transistor 8). Thus, it is possible to prevent the excess current from continuously flowing through the transistor 8.
[0026]
According to the circuit for the current-driven semiconductor switching element in the first embodiment, the overcurrent flowing in the transistor 8 is detected based on the current Ices flowing in the mirror transistor 9 and flows into the mirror transistor 9 when the transistor 8 is turned off. Since the overvoltage is detected based on the leak current Ices, a circuit element for detecting the overvoltage state and the overcurrent state can be shared. That is, the mirror transistor 9, the operational amplifier 11, and the level conversion circuit 12 can be shared to realize the overvoltage protection function and the overvoltage protection function of the circuit, so that the cost can be reduced. Further, when an overvoltage state or an overcurrent state is detected, the on / off control of the transistor 8 is performed regardless of the signal level of the control terminal IN, so that the transistor 8 can be protected from the overvoltage state and the overcurrent state.
[0027]
Since the value of the current flowing through the mirror transistor 9 greatly differs between the overcurrent state and the overvoltage state, two kinds of resistors having different resistance values are used as the resistors used for detecting the overcurrent and the overvoltage. Thus, the overvoltage state and the overcurrent state can be reliably detected. The overvoltage state and the overcurrent state are detected by comparing a voltage obtained by amplifying a voltage applied to both ends of the resistor 15 or the resistor 16 with a predetermined voltage. Therefore, the transistor 8 can be reliably protected from overvoltage and overcurrent.
[0028]
Further, since the Zener diode 6 as described in the related art becomes unnecessary, the problem of heat generation in the Zener diode 6 does not occur. Further, when the Zener diode 6 is used, as described above, there is a problem that the voltage range of the usable circuit is limited. However, in the present embodiment, the setting range of the clamp voltage is Since this can be handled by setting the value, the voltage range of the applicable circuit is widened.
[0029]
Second Embodiment FIG. 3 is a diagram showing the configuration of a second embodiment of a circuit for a current-driven semiconductor switching element according to the present invention. The same components as those in the circuit according to the first embodiment are denoted by the same reference numerals, and description thereof is omitted. In the circuit according to the second embodiment, the leakage current and the overcurrent are detected by using one resistor 20, and the amplification gain (amplification degree) of the detection voltage is switched by the gain variable operation amplifier 21.
[0030]
The variable gain operation amplifier 21 includes amplifiers 21a and 21b having different gains from the operation amplifier 11, and a switch 21c. The switch 21c switches the amplifiers 21a and 21b to be used according to the output signal S4 from the INV gate 14, that is, the signal level of the control terminal IN. The gain of the amplifier 21a is n, and the gain of the amplifier 21b is m (≫n). When the transistor 8 is turned on during normal operation, that is, when the control terminal IN is at the L level, the amplifier 21a is selected to detect an overcurrent state. On the other hand, when the transistor 8 is off during normal operation, that is, when the control terminal IN is at the H level, the amplifier 21b is selected to detect an overvoltage state. That is, in the overcurrent state, the current flowing through the resistor 20 becomes large. Therefore, the amplifier 21a having a small gain value is selected. When the leak current flows through the resistor 20 in the overvoltage state, the gain value is large. The amplifier 21b is selected.
[0031]
−Overvoltage protection function−
The overvoltage protection function of the circuit shown in FIG. 3 will be briefly described. It is assumed that a high voltage higher than the withstand voltage of the transistor 8 is applied to the collector terminal of the transistor 8 in a state where the control terminal IN is at the H level and the transistor 8 is off. In this case, a leak current Ices corresponding to the mirror ratio flows between the collector and the emitter of the mirror transistor 9, and thus a voltage corresponding to the magnitude of the leak current Ices is applied to both ends of the resistor 20.
[0032]
As described above, when the control terminal IN is at the H level, the amplifier 21b is selected. Therefore, the voltage applied to both ends of the resistor 20 is amplified by the operation amplifier 11, multiplied by m by the amplifier 21 b, and output to the level conversion circuit 12. As in the first embodiment, when the voltage level of the input signal S1 exceeds a preset clamp voltage VceC level, the level conversion circuit 12 outputs an H-level signal S2. As a result, the output S3 of the XOR gate 13 becomes L level, and a base current flows through the transistor 8, so that a current flows between the collector and the emitter, and the overvoltage energy applied to the collector terminal of the transistor 8 can be consumed. .
[0033]
−Overcurrent protection function−
The overcurrent protection function of the circuit shown in FIG. 3 will be briefly described. It is assumed that some problem occurs in the load 7 when the control terminal IN is at the L level and the transistor 8 is on, and an excessive current that does not flow during normal operation flows to the transistor 8. A leak current Ices according to the mirror ratio flows between the collector and the emitter of the mirror transistor 9. As described above, when the control terminal IN is at the L level, the amplifier 21a is selected. Therefore, the voltage applied to both ends of the resistor 20 is amplified by the operating amplifier 11 and then multiplied by n in the amplifier 21a. It is output to the level conversion circuit 12.
[0034]
The level conversion circuit 12 outputs an H level signal S2 when the input signal S1 exceeds a preset clamp voltage VceC level. As a result, the gate output S3 of the XOR gate 13 becomes H level, the P-type MOSFET 4 is turned off, and the N-type MOSFET 5 is turned on. 8 is forcibly turned off. Thus, it is possible to prevent the excess current from continuously flowing through the transistor 8.
[0035]
According to the circuit for the current-driven semiconductor switching element in the second embodiment, similarly to the first embodiment, there is an effect that it is not necessary to use a Zener diode, and the amplifiers 21a and 21b having different gains are used. By using this, the overvoltage protection function and the overcurrent protection function can be realized using one resistor 20. Since the states of overvoltage and overcurrent differ depending on the signal level (H / L) of the control terminal IN, the overvoltage state and the overcurrent state are reliably detected by switching the gain according to the signal level of the control terminal IN. be able to. Further, when detecting an overvoltage state, since the voltage applied to the resistor 20 is small, the amplifier 21b having a large gain (amplification degree) is selected, so that the overvoltage state can be reliably detected.
[0036]
The present invention is not limited to the above embodiment. For example, although the case where the bipolar transistor 8 is used as the current control type semiconductor switching element has been described, other switching elements can be used. Further, the current control type semiconductor switching element is not limited to a low-side switch configuration, and may be used as a high-side switch, or applied to various circuit configurations such as a half-bridge configuration, an H-bridge configuration, and an inverter configuration. can do.
[0037]
The correspondence between the components of the claims and the components of the embodiment is as follows. That is, the bipolar transistor 8 is a current control type semiconductor switching element, the mirror transistor 9 is a mirror element, the control terminal IN, MOSFETs 4 and 5, the level conversion circuit 12 and the XOR gate 13 control means, the resistor 16, the operating amplifier 11 and The level conversion circuit 12 serves as an overvoltage detecting means, the resistor 15, the operating amplifier 11 and the level converting circuit 12 serve as an overcurrent detecting means, the resistor 16 serves as a first resistor, the resistor 15 serves as a second resistor, Reference numeral 21 constitutes voltage amplifying means. Note that each component is not limited to the above configuration as long as the characteristic functions of the present invention are not impaired.
[Brief description of the drawings]
FIG. 1A is a diagram showing a configuration of a first embodiment of a current control type semiconductor switching element circuit according to the present invention, and FIG. 1B is a truth table of an XOR gate; Is shown.
FIG. 2 is a diagram showing a relationship between a voltage between an emitter and a collector of a transistor 8 and a leak current flowing through a mirror transistor 9; FIG. 3 is a second diagram of a circuit for a current-controlled semiconductor switching element according to the present invention; FIG. 4A is a diagram showing a circuit configuration of a conventional technology, and FIG. 4B is a truth table of an OR gate used in a circuit of the conventional technology. .
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Transistor drive power supply, 2 ... Load drive power supply, 3 ... OR gate, 4 ... P-type MOSFET, 5,17 ... N-type MOSFET, 6 ... Zener diode, 7 ... Load, 8 ... Bipolar transistor, 9 ... Mirror Transistors, 10, 15, 16, 20 resistors, 11 operating amplifiers, 12 level conversion circuits, 13 XOR gates, 14 INV gates, 21 variable gain operating amplifiers, 21a, 21b amplifiers, 21c switches

Claims (7)

A current-controlled semiconductor switching element;
A mirror element of the current control type semiconductor switching element,
Control means for performing on / off control of the current control type semiconductor switching element; overvoltage detection means for detecting an overvoltage applied to the current control type semiconductor switching element based on a leak current flowing through the mirror element;
An overcurrent detection unit configured to detect an overcurrent flowing through the current control type semiconductor switching element based on a current flowing through the mirror element,
The control means turns on the current control type semiconductor switching element when the overvoltage detection means detects an overvoltage state of the current control type semiconductor switching element, and the current control type semiconductor switching element by the overcurrent detection means. Wherein the current-controlled semiconductor switching element is turned off when the overcurrent state is detected. The circuit for a current control type semiconductor switching element according to claim 1,
The overvoltage detection means has a first resistor connected to the mirror element, and detects an overvoltage state of the current control type semiconductor switching element based on a voltage applied to both ends of the first resistor and a predetermined voltage. To detect
The overcurrent detection means has a second resistor connected to the mirror element in parallel with the first resistor, based on a voltage applied to both ends of the second resistor and the predetermined voltage. A current control type semiconductor switching element circuit for detecting an overcurrent state of the current control type semiconductor switching element. The circuit for a current control type semiconductor switching element according to claim 2,
A circuit for a current-controlled semiconductor switching element, wherein a resistance value of the first resistor is larger than a resistance value of the second resistor. The circuit for a current control type semiconductor switching element according to claim 1,
A resistor connected to the mirror element;
Voltage amplification means for amplifying a voltage applied to both ends of the resistor,
The overvoltage detection unit detects the overvoltage state by comparing a voltage applied to both ends of the resistor by the voltage amplification unit with a voltage amplified at a first amplification factor and a predetermined voltage,
The overcurrent detection unit detects the overcurrent state by comparing a voltage applied to both ends of the resistor by the voltage amplification unit with a voltage amplified at a second amplification factor and the predetermined voltage. Characteristic circuit for current control type semiconductor switching element. The circuit for a current control type semiconductor switching element according to claim 4,
The voltage amplifying means switches between the first amplification degree and the second amplification degree based on an on / off command of the current control type semiconductor switching element. circuit. The circuit for a current control type semiconductor switching element according to claim 4 or 5,
The circuit for a current control type semiconductor switching element, wherein the first amplification degree is larger than the second amplification degree. The circuit for a current control type semiconductor switching element according to any one of claims 2 to 6,
The circuit for a current control type semiconductor switching element, wherein the predetermined voltage is determined based on a clamp voltage of the current control type semiconductor switching element.

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