JP2001352748A - Gate drive circuit for semiconductor switching element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a switching loss while suppressing occurrence of a current surge and a noise at a turning on time of an insulated gate type semiconductor switching element and to prolong a lifetime of the element. SOLUTION: A control circuit 23 turns on a switching element 18 for turning on an IGBT 11 when the IGBT 11 is turned on based on a gate timing signal from a gate signal generator 24, outputs an on-voltage from a first output terminal 12a of a DC voltage source 12, lowers a level of the on-voltage from the first output terminal 12a thereafter when the gate voltage of the IGBT 11 for detecting a gate voltage detector 22 arrives at a first set value and further resets the level of the on-voltage to an original state when the gate voltage to be detected by the gate voltage detector 22 arrives at a second set value (> the first set value).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an IGBT or MOS
The present invention relates to a gate drive circuit for an insulated gate semiconductor switching device such as an FET.

[0002]

FIG. 5 shows an example of a basic circuit configuration of an inverter device for driving an AC motor at a variable speed. In FIG. 5, an inverter main circuit 1 is configured by connecting a total of six semiconductor switching elements 2a to 2f, for example, IGBTs in a three-phase bridge, and outputs an output of a DC power supply 4 supplied through a smoothing capacitor 3. To generate an AC output of a variable voltage and a variable frequency to switch the AC motor 5
To supply. These semiconductor switching elements 2a to 2f
Are turned on / off in a predetermined mode by a gate control signal from the gate control circuit 6, and
Reflux diodes 7a to 7f are connected in parallel with the semiconductor switching elements 2a to 2f, respectively.

In such a circuit configuration, for example, FIG.
From the state where the current flows in the direction indicated by the arrow A (the state where the semiconductor switching elements 2a and 2d are turned on),
When switching the semiconductor switching elements 2a and 2d to the off state in order to switch to the state in which current flows in the direction indicated by the arrow B, and when switching the semiconductor switching elements 2b and 2e to the on state, the semiconductor switching elements 2b and 2e and the freewheeling diode are used. A phenomenon in which a current suddenly flows through 7a and 7d occurs. However, such a suddenly flowing current causes current surge and noise, increases switching loss, and in some cases, causes destruction or deterioration of the semiconductor switching element or free-wheeling diode.

On the other hand, for example, Japanese Unexamined Patent Publication No. Hei 10-23743 discloses a drive voltage for applying a gate voltage to an IGBT element for the purpose of suppressing voltage surge and reducing switching loss during switching of the IGBT element. In addition to providing a plurality of (for example, two) sources,
A driving circuit for a semiconductor device having a configuration in which switching means for switching between these driving voltage sources is provided when the BT device is turned off is disclosed. However, since the driving circuit of the semiconductor element functions only when the semiconductor element is turned off, it cannot solve the above-described problem that occurs in the circuit configuration shown in FIG.

The present invention has been made in view of the above circumstances, and an object of the present invention is to suppress the occurrence of current surge and noise at the time of turning on an insulated gate semiconductor switching element, to reduce switching loss,
It is an object of the present invention to provide a gate drive circuit of a semiconductor switching element which can extend the life of the element.

[0006]

To achieve the above object, the means described in claim 1 can be adopted. According to this means, the gate control means (23) controls the turn-on switching element (1) based on the gate control timing signal.
8) and the turn-off switching element (20) are selectively turned on. When the turn-on switching element (18) is turned on, the DC voltage source (1) is turned on.
2) The first output terminal (12a) and the gate electrode of the insulated gate semiconductor switching element (11) are connected via a turn-on gate resistor (19), and the semiconductor switching element (11) is turned on. ) Is turned on by receiving an ON voltage at the gate electrode. When the turn-off switching element (20) is turned on,
A state is established in which the second output terminal (12b) of the DC voltage source (12) and the gate electrode of the insulated gate semiconductor switching element (11) are connected via a turn-off gate resistor (21). Switching element (1
1) is turned off by receiving an off-voltage at the gate electrode.

In this case, when the turn-on switching element (18) is turned on, the gate control means (23) particularly controls the gate voltage of the insulated gate type semiconductor switching element (11) detected by the voltage detection means (22). Control for changing the level of the on-voltage output from the first output terminal (12a) of the DC voltage source (12) according to the level is performed. Therefore, for example, in the process of turning on the insulated gate type semiconductor switching element (11), it is possible to control the gate voltage level to be switched to a low state for a predetermined period. The charging current flowing through the gate capacitance of the switching element (11) is limited. As a result, in the above-mentioned period, since the rise of the gate voltage of the semiconductor switching element (11) is suppressed, the di / dt (that is, the rising speed) of the load current flowing through the semiconductor switching element (11) becomes slow. As a result, the load current does not suddenly flow when the insulated gate semiconductor switching element (11) is turned on, so that the switching loss can be reduced while suppressing the occurrence of current surge and noise, and the semiconductor switching element can be reduced. This is useful in extending the life of (11).

According to the second aspect of the present invention, the gate control means (23) includes the turn-on switching element (1).
8) When the insulated gate semiconductor switching element (1) is detected by the voltage detecting means (22) when it is turned on.
The level of the ON voltage supplied to the gate electrode of the semiconductor switching element (11) is temporarily reduced only during the period in which the level of the gate voltage of 1) is between the first set value and the second set value. Control will be performed. For this reason,
During the above period, an increase in the gate voltage of the insulated gate semiconductor switching element (11) can be suppressed. Further, when the semiconductor switching element (11) is turned on, the control for switching the gate voltage level to a low state can be reliably performed for a preset period.

According to the third and fourth aspects, the detection as to whether or not the gate voltage of the insulated gate type semiconductor switching element (11) has reached the second set value is made by the semiconductor switching element (11). This can be easily performed by detecting the gate voltage at the point in time when the gate voltage or the rate of change of the gate voltage temporarily drops due to the Miller effect in the turn-on process of ()).

According to a fifth aspect of the present invention, the gate control means (23) includes the turn-on switching element (1).
8) When the insulated gate semiconductor switching element (1) is detected by the voltage detecting means (22) when it is turned on.
The semiconductor switching element (1) for a predetermined time from the time when the level of the gate voltage of (1) reaches the first set value.
The control of (1) for temporarily lowering the level of the on-voltage supplied to the gate electrode is performed. Therefore, control for switching the gate voltage level to a low state when the insulated gate semiconductor switching element (11) is turned on can be reliably performed for a preset period.

According to the means described in claim 6, the gate control means (23) is provided with a turn-on switching element (1).
When 8) is turned on, the control for temporarily lowering the level of the on-voltage supplied to the gate electrode of the insulated gate semiconductor switching element (11) is performed by controlling the load current flowing through the semiconductor switching element (11). Since the operation is terminated after reaching the peak value, the occurrence of surge can be effectively suppressed.

According to the seventh aspect, the control for temporarily lowering the level of the ON voltage supplied to the gate electrode of the insulated gate semiconductor switching element (11) is performed by controlling the gate of the semiconductor switching element (11). This is performed only when the voltage rises to the gate threshold voltage, that is, when the load current starts flowing through the semiconductor switching element (11). Therefore, the time when the load current starts flowing can be accurately grasped. For this reason, it is possible to reliably prevent a situation in which the load current suddenly flows when the insulated gate semiconductor switching element (11) is turned on.

According to the invention, the gate control means (25) selectively turns on the turn-on switching element (18) and the turn-off switching element (20) based on the gate control timing signal. When the turn-on switching element (18) is turned on, the first output terminal (12a) of the DC voltage source (12) and the insulated gate semiconductor switching element (1)
A turn-on gate resistor (1) is connected to the gate electrode of (1).
9), and the semiconductor switching element (11) is turned on by receiving an ON voltage at the gate electrode. When the turn-off switching element (20) is turned on, a turn-off gate is provided between the second output terminal (12b) of the DC voltage source (12) and the gate electrode of the insulated gate semiconductor switching element (11). The semiconductor switching element (11) is turned off by receiving an off-voltage at the gate electrode, by being connected via the resistor (21).

In this case, especially when turning on the turn-on switching element (18), the gate control means (25) outputs the first output of the DC voltage source (12) after a lapse of a predetermined time from the turning-on time. Control for changing the level of the on-voltage output from the terminal (12a) for a predetermined period is performed. Therefore, for example, when the insulated gate semiconductor switching element (11) is turned on, it is possible to perform control such that the gate voltage level is switched to a low state for a predetermined period, and when such control is performed, the above-described control is performed. The charging current flowing through the gate capacitance of the semiconductor switching element (11) is limited. As a result,
In the above period, the semiconductor switching element (11)
Is suppressed, the di / dt (that is, the rising speed) of the load current flowing through the gate voltage becomes slow. As a result, the load current does not suddenly flow when the insulated gate semiconductor switching element (11) is turned on, so that the switching loss can be reduced while suppressing the occurrence of current surge and noise, and the semiconductor switching element can be reduced. This is useful in extending the life of (11). In addition, since the ON voltage level change control is performed only by time control, the entire circuit configuration can be simplified.

According to the ninth aspect, the gate control means (25) includes the turn-on switching element (1).
8) When the transistor is turned on, the level of the on-voltage supplied to the gate electrode of the insulated gate semiconductor switching element (11) is temporarily reduced for a predetermined period after a predetermined time has elapsed from the time when the transistor is turned on. Control will be performed.
For this reason, in the above-mentioned period, an increase in the gate voltage of the semiconductor switching element (11) can be suppressed.

According to each of the means, the level of the on-voltage output from the first output terminal (12a) can be easily controlled by controlling the voltage switching switching elements (16, 17). Can be changed to

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment A first embodiment of the present invention will be described below with reference to FIGS. In FIG. 1 showing the entire electrical configuration, IG
The BT11 is an insulated gate semiconductor switching element in which the conduction state between the collector and the emitter is controlled by the gate voltage applied to the gate electrode. In the figure, the gate-collector capacitance Cgc and the gate-emitter capacitance Cge are equivalent circuits. Is shown in

The DC voltage source 12 is for generating a positive ON voltage for turning on the IGBT 11 and a negative OFF voltage for turning off the IGBT 11, and has a first output terminal 12a for outputting an ON voltage. , And a second output terminal 12b for outputting an off-voltage. In this case, the DC voltage source 12 is configured so that the level of the on-voltage output from the first output terminal 12a can be changed in two stages.
For example, the circuit configuration is as shown in FIG.

That is, in FIG. 2, the DC voltage source 12
Three voltage sources 13, 14 and 15, and voltage switching switching elements 16 and 17 in which only one is selectively turned on
, And at least the voltage sources 13 and 14 have different output voltage levels from each other.
The voltage sources 13 and 14 have their respective positive terminals connected to the first output terminal 12a via the voltage switching switching elements 16 and 17 individually, and their negative terminals connected to the ground terminal. In the voltage source 15, the negative terminal is connected to the second output terminal 12b, and the positive terminal is connected to the ground terminal. Each of the switching elements 13 and 15 is a semiconductor switching element (FET,
A bipolar transistor).

In the DC voltage source 12 configured as described above, for example, when the voltages between the terminals of the voltage sources 13, 14, and 15 are respectively V13, V14, and V15 (V13> V14), the first Output terminal 12a outputs one of the positive ON voltages + V13 and + V14 in accordance with the ON state of the voltage switching switching elements 16 and 17, and outputs the negative OFF voltage from the second output terminal 12b. The voltage -V15 is output.

Referring back to FIG. 1, between the first output terminal 12a of the DC voltage source 12 and the gate electrode of the IGBT 11,
A turn-on switching element 18 and a turn-on gate resistor 19 are connected in series, and a turn-off switching element 20 and a turn-off gate resistor 21 are provided between the second output terminal 12 b of the DC voltage source 12 and the gate electrode of the IGBT 11. Are connected in series. Each of the switching elements 18 and 20 is also constituted by a semiconductor switching element (FET, bipolar transistor, etc.). Further, the turn-on gate resistor 19 and the turn-off gate resistor 21 can be shared by one resistor.

The gate voltage detecting circuit 22 (corresponding to the voltage detecting means in the present invention) is provided for detecting the gate voltage of the IGBT 11, and uses the detected voltage in the control circuit 23 (the gate controlling means in the present invention). ). The gate signal generation circuit 24 is an IGBT
A gate control timing signal for controlling the on / off state of the switch 11 is generated in a predetermined mode, and the gate control timing signal is supplied to the control circuit 23.

The control circuit 23 includes a gate signal generation circuit 24
When the turn-on switching element 18 and the turn-off switching element 20 are selectively turned on on the basis of the gate timing signal from the switch, and particularly when the turn-on switching element 18 is turned on, the detection voltage level of the gate voltage detection circuit 22 By selectively turning on one of the voltage switching switching elements 16 and 17 in the DC voltage source 12 based on the
The control for changing the level of the on-voltage output from the first output terminal 12a of the DC voltage source 12 is performed.

In the following, a specific example of the contents of control by the control circuit 23 and an operation related to the control will be described with reference to a characteristic curve of FIG. FIG. 3 schematically shows the change characteristics of the gate voltage Vge, the collector-emitter voltage Vce, and the collector current Ic (load current) of the IGBT 11.

The control circuit 23 includes a gate signal generation circuit 24
Is turned on, the turn-on switching element 18 is turned on. At this time, the DC voltage source 1
The switching element 16 for voltage switching in 2 is previously turned on. Therefore, the first output terminal 1 of the DC voltage source 12
An ON voltage (= + V13) corresponding to the terminal voltage of the voltage source 13 is output from 2a, and the ON voltage is started to be applied to the gate electrode of the IGBT 11 via the turn-on gate resistor 19 ( Timing t1 in FIG. 3). When the gate voltage Vge becomes equal to or higher than the gate threshold voltage Vth of the IGBT 11 in response to the application of the ON voltage (timing t2), the collector current Ic starts to flow and the collector-emitter voltage Vce starts to decrease.

Thereafter, the control circuit 23 controls the gate voltage Vge
Is determined based on the voltage detected by the gate voltage detection circuit 22 at a timing (timing t3) when the voltage reaches the first set value Vs1 set in advance, the voltage switching switching element 16 in the DC voltage source 12 is turned off, and Then, the voltage switching device 17 is turned on. As a result, an ON voltage (= + V14 <+ V13) corresponding to the terminal voltage of the voltage source 14 is output from the first output terminal 12a of the DC voltage source 12, and the ON voltage applied to the gate electrode of the IGBT 11 The state is switched to the state where the voltage level is lowered.

After the switching of the ON voltage, the control circuit 23 sets the time when the gate voltage Vge reaches the second preset value Vs2 (timing t4) to the detection voltage of the gate voltage detection circuit 22. Judge based on. In this case, the second set value Vs2 can be set as an absolute value. However, when the IGBT 11 is turned on, the state where the rate of change of the gate voltage Vge is temporarily reduced by the Miller effect is changed to the gate voltage. It is also possible to adopt a configuration in which detection is performed based on the detection voltage by the detection circuit 22, and when such a detection state is established, it is determined that the gate voltage Vge has reached the second set value Vs2.

The control circuit 23 controls the gate voltage Vge
Is determined to have reached the second set value Vs2, the voltage switching switching element 16 in the DC voltage source 12 is returned to the ON state, and the first output terminal 12a is
Switching is performed such that an ON voltage (= V13) corresponding to the terminal voltage of the voltage source 13 is output. Thereby, the IGBT 11
From the state where the level of the on-voltage applied to the gate electrode is lowered to the original state, and finally the state where the IGBT 11 is completely turned on (the collector-emitter voltage Vce is substantially reduced). (Zero state).

Thereafter, in the control circuit 23, when a gate control timing signal for instructing the IGBT 11 to be turned off is input from the gate signal generation circuit 24, the turn-off switching element 20 is used instead of the turn-on switching element 18. Turn on. As a result, the negative output voltage (= −V15) is output from the second output terminal 12a of the DC voltage source 12, and the off voltage is applied to the gate electrode 21 of the IGBT 11 by the turn-off gate resistor 21. Is started (timing t5 in FIG. 3). In response to such an off-voltage application, the IGBT
11 will eventually be turned off.

In short, according to the configuration of the present embodiment described above, the following effects can be obtained. That is,
When the IGBT 11 is turned on, control is performed such that the gate voltage level is switched to a low state for a predetermined period, so that the charging current flowing through the gate-emitter capacitance Cge of the IGBT 11 is limited. As a result, during the period in which the gate voltage level is switched as described above, the rise of the gate voltage Vge of the IGBT 11 is suppressed, so that the collector current Ic (load current) flowing through the IGBT 11 is di / dt (that is, the rising speed). ) Becomes loose. As a result, the collector current Ic does not suddenly flow when the IGBT 11 is turned on, so that the switching loss can be reduced while the occurrence of current surge and noise can be suppressed, and the destruction and deterioration of the IGBT 11 can be prevented. It is useful for extending the life. If a freewheeling diode is provided in association with the IGBT 11, the freewheeling diode can be prevented from being broken or deteriorated.

When the IGBT 11 is turned on as described above, the control for switching the level of the gate voltage Vge to a low state is performed by controlling the detection voltage of the gate voltage detection circuit 22 and the first set value Vs1 and the preset first set value Vs1. Since the control is performed based on the second set value Vs2, the control can be reliably performed for a predetermined period. in this case,
Since the second set value VS2 is set to the gate voltage Vge at the time when the rate of change of the gate voltage Vge temporarily decreases due to the Miller effect during the turn-on process of the IGBT 11, for example, the gate voltage Vge is set to the second set value. It is possible to easily detect whether or not the value has reached the value Vs2.

The DC voltage source 12 for generating the ON voltage applied to the gate of the IGBT 11 includes a plurality of voltage sources 13 and 14 for generating the ON voltage, and these voltage sources 13 and 14
Are selectively enabled to output the first output terminal 12a.
Is provided with the voltage switching switching elements 16 and 17 for switching the level of the on-voltage output from the controller. By controlling the voltage switching switching elements 16 and 17, the level of the on-voltage can be reduced. It can be easily changed.

(Second Embodiment) FIG. 4 shows a second embodiment of the present invention, and only the portions different from the first embodiment will be described below. That is, in the second embodiment, the gate voltage detection circuit 22 (see FIG. 1) in the first embodiment is omitted, and a control circuit 25 (gate control means according to the present invention) is used instead of the control circuit 23 in the same embodiment. ) Is provided. The control circuit 25 selectively turns on the turn-on switching element 18 and the turn-off switching element 20 based on the gate timing signal from the gate signal generation circuit 24, and particularly when the turn-on switching element 18 is turned on. A first output terminal 12a of the DC voltage source 12 after a lapse of a predetermined time from the ON time.
The control is performed such that the level of the on-voltage output from is reduced for a predetermined period.

The control for reducing the level of the ON voltage for a predetermined period as described above is performed by switching the ON state of the voltage switching switching elements 16 and 17 (see FIG. 2) in the DC voltage source 12 in time series. It is something to be done. Specifically, the ON voltage + V13 is output by the voltage switching switching element 16 already turned on at the time when the turn-on switching element 18 is turned on, and after a lapse of a predetermined time, the voltage switching switching element 16 is turned on.
Instead, the switching element 17 for voltage switching is turned on to output the on-voltage + V14, and when a predetermined time has elapsed thereafter, the switching element 16 for voltage switching is returned to the on state to output the on-voltage + V13. It is in the state where it was done.

According to the second embodiment constructed as described above, the same effects as those of the first embodiment can be obtained.
According to the second embodiment, since the ON voltage level change control is performed only by time control, the simplification of the entire circuit configuration can be realized, for example, the gate voltage detection circuit 22 becomes unnecessary. .

(Other Embodiments) In addition, the present invention is not limited to the above embodiments, and the following modifications or expansions are possible. In the first embodiment, the control circuit 23 controls the control to temporarily lower the level of the on-voltage output from the first output terminal 12a of the DC voltage source 12 by the gate voltage V
Although ge is performed during a period between the first set value Vs1 and the second set value Vs2, the gate voltage Vge detected by the gate voltage detection circuit 22 is changed to the first set value Vs1.
, The control for temporarily lowering the level of the on-voltage for a predetermined period of time from the time point when the power supply voltage has reached may be employed. According to this configuration, when the IGBT 11 is turned on, control for switching the gate voltage level to a low state can be reliably performed for a preset period.

In each of the first and second embodiments,
The control for temporarily lowering the level of the on-voltage output from the first output terminal 12a of the DC voltage
The configuration may be such that the load current (collector current Ic) flowing through T11 ends after reaching the peak value, and according to this configuration, the occurrence of surge can be effectively suppressed.

In the first embodiment, the first set value Vs1
May be set to a value equal to the gate threshold voltage Vth of the IGBT 11.
The control for temporarily lowering the level of the ON voltage supplied to the gate electrode of the BT11 is performed when the gate threshold voltage Vth of the IGBT11 is increased, that is, when the load current (collector current Ic) starts flowing through the IGBT11. Since it is performed for the first time, it becomes possible to accurately grasp the time when the load current starts to flow. As a result, the IGBT
At the time of turn-on of 11, it is possible to reliably prevent the load current from flowing rapidly.

In the first embodiment, as an example, the configuration in which the state in which the change rate of the gate voltage Vge of the IGBT 11 is temporarily reduced due to the Miller effect is detected based on the detection voltage of the gate voltage detection circuit 22 is described. However, a configuration may be adopted in which the detection is performed based on a differential value of the detection voltage (gate voltage of the IGBT 11).

The configuration of the DC voltage source 12 is not limited to the above-described embodiment. For example, by selecting a series-parallel state of a plurality of voltage sources by a voltage switching switching element, the first output terminal 12a A configuration may be employed in which the level of the on-voltage output from is switched. Further, the off-voltage output from the second output terminal 12b of the DC voltage source 12 may be at the ground potential level. In this case, the voltage source 15 in the DC voltage source 12 can be omitted. It is needless to say that the present invention can be applied to a drive circuit of an insulated gate semiconductor switching element (for example, a MOSFET) other than the IGBT.

[Brief description of the drawings]

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

FIG. 2 is a circuit diagram of a main part.

FIG. 3 is a characteristic curve diagram for explaining operation.

FIG. 4 is a view corresponding to FIG. 1 showing a second embodiment of the present invention.

FIG. 5 is a circuit configuration diagram of an inverter device for explaining a conventional configuration.

[Explanation of symbols]

11 is an IGBT (insulated gate type semiconductor switching element), 12 is a DC voltage source, 12a is a first output terminal, 1
2b is a second output terminal, 13 to 15 are voltage sources, 16, 1
7 is a switching element for voltage switching, 18 is a switching element for turn-on, 19 is a gate resistor for turn-on,
Reference numeral 0 denotes a switching element for turning off, 21 denotes a gate resistor for turning off, 22 denotes a gate voltage detecting circuit (voltage detecting means), and 23 and 25 denote control circuits (gate controlling means).

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference)

Claims (11)

[Claims] 1. A gate drive circuit for an insulated gate semiconductor switching element (11), comprising: a turn-on switching element (18) that is turned on when the insulated gate semiconductor switching element (11) is turned on; A turn-off switching element (20) that is turned on when the insulated gate semiconductor switching element (11) is turned off, and a first for supplying an on-voltage to a gate electrode of the insulated gate semiconductor switching element (11). An output terminal (12a) and a second output terminal (12b) for supplying an off-voltage to the gate electrode;
A DC voltage source (12) configured to be able to change the level of an ON voltage output from an output terminal (12a) of the DC voltage source; and the DC voltage source (12) in a state where the turn-on switching element (18) is turned on. Of the first output terminal (1
2a) and the insulated gate semiconductor switching element (1
1) a turn-on gate resistor (19) connected to the gate electrode, and a second output of the DC voltage source (12) with the turn-off switching element (20) turned on. Terminal (1
2b) and the insulated gate semiconductor switching element (1
A gate resistor for turn-off (21) connected to the gate electrode of (1), voltage detecting means (22) for detecting a gate voltage of the insulated gate semiconductor switching element (11), and gate control. A turn-on switching element (18) and a turn-off switching element (20) are provided to selectively turn on based on a timing signal;
When the turn-on switching element (18) is turned on, the first output terminal (12) of the DC voltage source (12) depends on the detected voltage level of the voltage detecting means (22).
A gate drive circuit for a semiconductor switching element, comprising: a gate control means (23) for controlling a level of an on-voltage output from a). 2. The gate drive circuit for a semiconductor switching element according to claim 1, wherein said gate control means (23) is said voltage detection means (22) when said turn-on switching element (18) is turned on. During a period in which the gate voltage detected by the first set value is between the first set value and a second set value higher than the first set value,
A gate drive circuit for a semiconductor switching element, which performs control to temporarily lower the level of an on-voltage output from a first output terminal (12a) of the DC voltage source (12). 3. The gate drive circuit of a semiconductor switching element according to claim 2, wherein said voltage detection means (22) temporarily changes a gate voltage change rate of said insulated gate semiconductor switching element (11) by a Miller effect. The second set value is set to a gate voltage at the time when the voltage detecting means (22) detects a temporary decrease in the gate voltage change rate. A gate drive circuit for a semiconductor switching element. 4. The gate drive circuit for a semiconductor switching element according to claim 3, wherein said voltage detecting means (22) temporarily changes a gate voltage change rate of said insulated gate semiconductor switching element (11) by a Miller effect. A gate drive circuit for a semiconductor switching element, wherein a state of decrease is detected based on a differential value of the gate voltage. 5. The gate drive circuit for a semiconductor switching element according to claim 1, wherein said gate control means (23) is said voltage detection means (22) when said turn-on switching element (18) is turned on. From the DC voltage source (1) for a predetermined time from when the gate voltage detected by the DC voltage reaches the first set value.
2) A gate drive circuit for a semiconductor switching element, which performs control to temporarily lower the level of the on-voltage output from the first output terminal (12a). 6. The gate drive circuit for a semiconductor switching element according to claim 5, wherein said gate control means (23) is configured to control said DC voltage source (1).
The control of 2) for temporarily lowering the level of the ON voltage output from the first output terminal (12a) is terminated after the load current flowing through the insulated gate semiconductor switching element (11) reaches a peak value. A gate drive circuit for a semiconductor switching element. 7. The gate drive circuit for a semiconductor switching element according to claim 2, wherein said first set value is a gate threshold voltage of said insulated gate semiconductor switching element (11). A gate drive circuit for a semiconductor switching element, which is set to be equal. 8. A gate drive circuit for an insulated gate semiconductor switching element (11), comprising: a turn-on switching element (18) that is turned on when the insulated gate semiconductor switching element (11) is turned on; A turn-off switching element (20) that is turned on when the insulated gate semiconductor switching element (11) is turned off, and a first for supplying an on-voltage to a gate electrode of the insulated gate semiconductor switching element (11). An output terminal (12a) and a second output terminal (12b) for supplying an off-voltage to the gate electrode;
A DC voltage source (12) configured to be able to change the level of an ON voltage output from an output terminal (12a) of the DC voltage source; and the DC voltage source (12) in a state where the turn-on switching element (18) is turned on. Of the first output terminal (1
2a) and the insulated gate semiconductor switching element (1
1) a turn-on gate resistor (19) connected to the gate electrode, and a second output of the DC voltage source (12) with the turn-off switching element (20) turned on. Terminal (1
2b) and the insulated gate semiconductor switching element (1
A turn-off gate resistor (21) connected to the gate electrode of (1), and the turn-on switching element (18) and the turn-off switching element (20) based on a gate control timing signal; To be turned on,
When the turn-on switching element (18) is turned on, the level of the on-voltage output from the first output terminal (12a) of the DC voltage source (12) after a lapse of a predetermined time from the on-time is changed for a predetermined period. A gate drive circuit for a semiconductor switching element, comprising: a gate control means (25) for performing a control for changing only the threshold value. 9. The gate drive circuit for a semiconductor switching element according to claim 8, wherein said gate control means (25) keeps said turn-on switching element (18) turned on for a predetermined time from the on time. And performing a control for temporarily lowering a level of an on-voltage output from a first output terminal (12a) of the DC voltage source (12) for a predetermined period after the lapse of time. Gate drive circuit. 10. The DC voltage source (12) includes a plurality of voltage sources (13, 14) for generating the ON voltage.
A voltage switching switching element (16, 17) for selectively enabling these voltage sources (13, 14) to switch the level of the on-voltage output from the first output terminal (12a); 10. The gate drive circuit for a semiconductor switching element according to claim 1, wherein the gate drive circuit comprises: 11. The gate drive circuit for a semiconductor switching element according to claim 10, wherein the plurality of on-voltage generating voltage sources have different output voltage levels from each other, and A switching element (16, 17) switches the level of the on-voltage by connecting one of the plurality of voltage sources (13, 14) to the first output terminal (12a). A gate drive circuit for a semiconductor switching element.