JPH08204526A - Gate drive circuit for switching element - Google Patents

Abstract

PURPOSE: To obtain high noise immunity in a steady-state by providing a 1st drive circuit providing a gate voltage to a gate electrode of a switching element via a resistor and a 2nd drive circuit providing a gate voltage to the gate electrode via a delay means to the switching element so as to suppress a surge voltage in a transient state. CONSTITUTION: When a gate voltage 5 transits to an On state, an auxiliary switching element 3a is conductive, the voltage of a positive gate voltage source 6p is impressed to the gate electrode of a switching element 1 via a resistor 2a. On the other hand, when the voltage 5 is switched from on OFF state to the On state, an auxiliary switching element 3c is conductive with the delay of a time constant specific to a 1st delay means 7a and the voltage from the positive gate voltage source 6p is impressed to the gate electrode of the element 1 via a resistor 2b. Thus, a surge voltage is suppressed in the transient state when the element 1 is nonconductive and a high noise immunity is obtained even in a steady state of ON and OFF states.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching element gate for controlling on / off of a switching element which constitutes a power converter for converting DC power into AC power, AC power into DC power, or DC power into DC power. Regarding a drive circuit.

[0002]

2. Description of the Related Art FIG. 7 shows a conventional gate drive circuit for switching elements. In FIG. 7, 1 is a switching element, 2 is a gate resistor, and 3a and 3b are switching elements 1.
Each of the auxiliary switching elements constituting the drive circuit for driving the gate of the auxiliary switching element 3a when the gate signal 5 given through the input resistor 4 is an ON command.
Is turned on, and the positive gate voltage source 6 is applied to the switching element 1.
A positive gate voltage is applied from p, and when the gate signal 5 is an OFF command, the auxiliary switching element 3b is turned on, and the negative gate voltage source 6n applies a negative gate voltage to the switching element 1.

In FIG. 7, when the gate signal 5 changes from on to off, the auxiliary switching element 3b becomes conductive, and the voltage of the negative gate voltage source 6n is applied to the gate electrode of the switching element 1 through the gate resistor 2. As a result, the switching element 1 is turned off.

At this time, an excessive surge voltage is applied between the anode and the cathode of the switching element 1 because of the amount of the reactor existing in the main circuit. This surge voltage is proportional to the switching speed, and increases with faster turn-off. Therefore, in general, a snubber circuit including a capacitor, a resistor and a capacitor is added to the switching element 1 to suppress the surge voltage.

However, if the turn-off itself of the switching element 1 is fast, the snubber circuit alone cannot suppress the increase of the surge voltage, and the size of the gate resistor 2 is adjusted so that the surge voltage at the turn-off is the maximum rating of the switching element 1. The switching speed is reduced so that it falls within the range.

That is, since there is an input electrostatic capacity (not shown) specific to the element between the gate and the cathode of the switching element 1, the gate of the switching element 1 has a time constant determined by the product of this input electrostatic capacity and the gate resistance 2. Since the potential of the electrode (hereinafter referred to as the gate voltage) changes, increasing the value of the gate resistance 2 causes the gate voltage to change slowly,
The smaller the value of, the faster the change. Therefore, in the conventional gate drive circuit, the value of the gate resistance 2 is increased to reduce the switching speed.

[0007]

In the conventional example of FIG. 7, when the switching element 1 is in a steady state and the noise current is superposed on the main circuit current, the value of the gate resistance 2 becomes large, so that the anode electrode of the switching element 1 becomes large. It becomes difficult for noise current to flow from the gate electrode to the gate electrode. Therefore, the noise current flows from the anode to the cathode, so that the voltage between the anode and the cathode of the switching element 1 fluctuates, and the switching element 1 is likely to be erroneously turned off. As a result, the noise immunity in the steady ON state becomes small.

In addition, when the switching element 1 is normally off, the main circuit voltage is applied between the anode and the cathode. When the main circuit voltage fluctuates, the noise current flowing through the stray capacitance between the anode and the gate due to the voltage fluctuation. It is difficult to flow to the gate resistance 2 side and charges the input capacitance of the gate and cathode. As a result, the gate voltage rises, and the switching element 1 is liable to be erroneously turned on, so that the noise immunity in the steady off state also decreases.

In order to increase the noise resistance, the value of the gate resistance 2 may be reduced, but since the switching speed is increased, a surge voltage is likely to be generated during the off switching transition.

As described above, if the value of the gate resistance 2 is large, the surge of the gate voltage during the switching transient of OFF can be suppressed, but the noise immunity in the steady state of ON or OFF becomes small. On the other hand, if the value of the gate resistance 2 is small, the noise immunity at the steady state of ON or OFF becomes large, but a surge voltage is easily generated during the switching transition of OFF, and it becomes a high frequency noise source.

As described above, the conventional gate resistance constant is set to a value at which the surge voltage falls within the rating of the switching element 1 with priority given to suppression of the surge voltage. Therefore, as long as the gate resistance 2 has a constant value, the surge voltage can be suppressed, but there is a problem that a large noise immunity cannot be obtained in the steady ON or OFF state.

An object of the present invention is to solve the above-mentioned problems, and suppresses a surge voltage during a transition of OFF switching and obtains a large noise immunity during a steady ON or OFF state. Another object of the present invention is to provide a gate drive circuit for a switching element that can be used.

[0013]

In order to achieve the above object, the invention according to claim 1 applies a positive gate voltage to a gate electrode of a switching element via a first resistor when an ON command is given. A first drive circuit that applies a negative gate voltage to the gate electrode of the switching element via the first resistor when an ON command is applied, and a first delay unit when the ON command is applied. A positive gate voltage that rises with a predetermined time constant is applied to the gate electrode of the switching element via the second resistor, and when the OFF command is given, a desired delay voltage is applied via the second delay means. A second drive circuit is provided for applying a negative gate voltage that decreases with a time constant to the gate electrode of the switching element via the second resistor.

According to a second aspect of the present invention, when an ON command is given, a positive gate voltage is applied to the gate electrode of the switching element through the first resistance, and when an OFF command is given, the gate voltage is applied. A first drive circuit for applying a negative gate voltage to the gate electrode of the switching element through the first resistor; and a positive gate that rises with a predetermined time constant through delay means when the ON command is given. A voltage is applied to the gate electrode of the switching element via the second resistor, and when the OFF command is given, a negative gate voltage that drops with a predetermined time constant via the delay means is applied to the gate of the switching element. A second drive circuit for applying voltage to the electrodes via the second resistor is provided.

Further, the invention described in claim 3 is the same as claim 1.
Alternatively, the voltage is applied to the gate electrode of the switching element via the second drive circuit from the voltage of the positive and negative gate voltage sources applied to the gate electrode of the switching element via the first drive circuit according to claim 2. It is characterized in that the voltages of the positive and negative gate voltage sources are increased.

According to a fourth aspect of the invention, when an ON command is given, a positive gate voltage is applied to the gate electrode of the switching element through the first resistor, and when an OFF command is given, the gate voltage is applied. A first drive circuit that applies a negative gate voltage to the gate electrode of the switching element via the first resistor, and a switch that closes when the switching element is normally on and off to the first resistor. It is characterized by having a second resistor connected in parallel.

Further, in the invention according to claim 5, a positive gate voltage is applied to the gate electrode of the switching element through the first resistor when an ON command is given, and the switching element is applied when an OFF command is given. The gate electrode of the first
A first drive circuit for applying a negative gate voltage via the resistor and a positive gate voltage that rises at a predetermined time constant via a delay means when the ON command is given to the gate electrode of the switching element. A second driving circuit for applying a voltage through a second resistor is provided.

According to a sixth aspect of the present invention, when an on command is given, a positive gate voltage is applied to the gate electrode of the switching element through the first resistor, and when an off command is given, the positive gate voltage is applied. A first drive circuit for applying a negative gate voltage to the gate electrode of the switching element via the first resistor; and a negative gate which falls with a predetermined time constant via a delay means when the off command is given. A second driving circuit for applying a voltage to the gate electrode of the switching element via a second resistor is provided.

Still further, according to the invention described in claim 7, the second driving is performed by the voltage of the positive gate voltage source applied to the gate electrode of the switching element through the first driving circuit described in claim 5. Increase the voltage of the positive gate voltage source applied to the gate electrode of the switching element through a circuit, or
The voltage of the negative gate voltage source applied to the gate electrode of the switching element via the first drive circuit according to claim 6, and the negative voltage applied to the gate electrode of the switching element via the second drive circuit. The feature is that the voltage of the gate voltage source is increased.

[0020]

According to the invention described in claim 1 configured as described above, at the transition of switching, the switching element is driven only by the first drive circuit via the first resistor, and the switching element In the steady state of on and off, the switching element is driven by both the first driving circuit and the second driving circuit via the second resistor, so that the gate of the switching element is driven by the first element when the switching transition occurs. The first resistance and the second resistance are connected in parallel to the gate of the switching element at the time of steady switching, so that the gate resistance is large at the transition of switching, and the gate resistance is small at the steady switching. Therefore, the surge voltage can be suppressed during the transition of switching off, and a large noise immunity can be obtained in the steady state.

According to a second aspect of the present invention, the first delay means and the second delay means are common delay means, and after the on command and the off command are given, the switching element is connected via the second resistor. The same timing of applying the positive gate voltage and the negative gate voltage to the gate of the gate is used, and as in the invention of claim 1, when the switching off transition occurs, the server is turned on.
It is possible to suppress the output voltage and obtain a large noise immunity in a steady state.

Further, the invention of claim 3 is based on the voltages of the positive and negative gate voltage sources applied to the gate electrode of the switching element through the first drive circuit in the invention of claim 1 or the invention of claim 2. By increasing the voltages of the positive and negative gate voltage sources applied to the gate electrode of the switching element via the second drive circuit, the surge voltage is suppressed during the switching off transition as in the invention of claim 1. However, a large noise immunity can be obtained in the steady state.

Further, in the invention of claim 4, the switching element is driven only by the first drive circuit via the first resistor during the transition of the switching, and the switching element is turned on and off in the steady state. The second resistor is connected to the
The gate resistance is reduced by connecting it in parallel with the resistance.

As a result, as in the first aspect of the invention, the surge voltage can be suppressed during the switching off transition, and a large noise immunity can be obtained in the steady state. Further, according to the invention of claim 5, when the switching transition occurs, the first
The switching element is driven only by the first drive circuit via the resistance of the second drive circuit, and when the switching element is in a steady ON state, both the first drive circuit and the second drive circuit via the second resistance are used together with the first drive circuit. By driving the switching element, only the first resistor is connected to the gate of the switching element at the transition of switching, and the first resistor and the second resistor are connected in parallel to the gate of the switching element when the switching element is on normally. Therefore, the gate resistance is large during the switching off transient, the gate resistance is small during the switching on steady state, the surge voltage is suppressed during the switching off transient, and the surge resistance is large during the switching on steady state. Noise tolerance can be obtained.

According to the invention of claim 6, the switching element is driven only by the first drive circuit via the first resistor during the switching transient, and when the switching element is in the steady off state, the first driving circuit drives the switching element. By driving the switching element with both the first drive circuit and the second drive circuit via the second resistor, during the transition of switching,
Since only the first resistor is connected to the gate of the switching element and the first resistor and the second resistor are connected in parallel to the gate of the switching element when the switching element is off, the gate is not connected when the switching is off. The resistance is large, the gate resistance is small when the switching element is off, and the surge voltage is suppressed during the switching off transition. A large noise immunity can be obtained when the switching element is off.

Further, according to a seventh aspect of the present invention, the voltage of the positive gate voltage source applied to the gate electrode of the switching element via the first drive circuit in the fifth aspect of the invention is used as the second
By increasing the voltage of the positive gate voltage source applied to the gate electrode of the switching element through the drive circuit of, the surge voltage is suppressed during the switching off transition, and a large noise immunity is maintained when the switching element is on. Can be obtained. According to the invention of claim 6, the voltage of the negative gate voltage source applied to the gate electrode of the switching element via the first drive circuit is changed to the negative voltage applied to the gate electrode of the switching element via the second drive circuit. It is possible to increase the voltage of the gate voltage source to suppress the surge voltage when the switching is off, and to obtain a large noise immunity when the switching element is off.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the invention described in claim 1 will be described below with reference to the configuration diagram of FIG. 1 in which the same parts as those in FIG. In FIG. 1, 1 is a switching element, 2a is a gate resistance (hereinafter referred to as a first resistance), 3a and 3b are respective auxiliary switching elements constituting a first drive circuit for driving the gate of the switching element 1, When the gate signal 5 given through the input resistor 4 is an on command, the auxiliary switching element 3a is turned on, and a positive gate voltage is given to the switching element 1 from the positive gate voltage source 6p. Is a turn-off command, the auxiliary switching element 3b is turned on, and a negative gate voltage is applied to the switching element 1 from the negative gate voltage source 6n.

Further, 2b is a gate resistor (hereinafter referred to as a second resistor), and 3c and 3d are auxiliary switching elements constituting a second drive circuit for driving the gate of the switching element 1, and an ON command 5 Is supplied to the gate electrode of the switching element 1, a positive gate voltage (supplied from the positive gate voltage source 6p) that drives the auxiliary switching element 3c by the first delay means 7a and rises with a predetermined time constant. When the OFF command 5 is applied by applying the voltage through the second resistor 2b, the auxiliary switching element 3d is driven by the second delay unit 7b, and the negative gate voltage (negative gate voltage source) is lowered with a desired time constant. 6n) is supplied to the gate electrode of the switching element 1 through the second resistor 2b.

When the gate signal 5 turns from off to on, the auxiliary switching element 3a becomes conductive and the positive gate voltage source 6
The voltage of p passes through the first resistor 2a and the switching element 1
Applied to the gate electrode of.

On the other hand, when the gate signal 5 turns from off to on, the auxiliary switching element 3c becomes conductive and the positive gate voltage source 6 is delayed by a time constant specific to the first delay means 7a.
The voltage of p is applied to the switching element 1 through the second resistor 2b.
Applied to the gate electrode of.

Therefore, since the auxiliary switching elements 3a and 3c are both conductive when the switching element 1 is normally turned on, the first resistor 2a and the second resistor 2b are connected in parallel, which is seen from the switching element 1. The gate resistance is low. At this time, even if the noise current is superimposed on the main circuit current, the noise current easily flows to the gate resistance side. Therefore, since the voltage fluctuation between the anode and the cathode of the switching element 1 is suppressed, the erroneous OFF operation is less likely to occur, and the noise immunity in the steady ON state is increased.

Similarly, when the gate signal 5 turns from on to off, the auxiliary switching element 3b becomes conductive, and the voltage of the negative gate voltage source 6n is applied to the gate electrode of the switching element 1 through the first resistor 2a.

On the other hand, when the gate signal 5 turns from ON to OFF, the gate signal 5 is delayed by the time constant peculiar to the second delay means 7b,
When the auxiliary switching element 3d becomes conductive, the voltage of the negative gate voltage source 6n is applied to the gate electrode of the switching element 1 through the second resistor 2b.

Therefore, only the auxiliary switching element 3b is conducting during the off-transition of the switching element 1,
At this time, the gate voltage slowly drops because the value of the first resistor 2a is large. Therefore, the surge voltage is less likely to be generated during the off-transition.

On the other hand, when the switching element 1 is normally off, the auxiliary switching elements 3b and 3d are both conductive, and the gate resistance seen from the switching element 1 is low. At this time, even if the main circuit voltage applied to the anode / cathode of the switching element 1 changes, the anode
A noise current flowing through the stray capacitance between the gates easily flows to the gate resistance side. Therefore, the voltage fluctuation between the anode and the cathode of the switching element 1 is also suppressed, so that the erroneous ON operation is less likely to occur, and the noise immunity in the steady OFF state is increased.

As described above, according to the present embodiment, it is possible to suppress the surge voltage when the switching element 1 is off, and to obtain a high noise immunity even when the switching element 1 is normally turned on and off.

Next, an embodiment of the invention described in claim 2 will be described with reference to the configuration diagram of FIG. 2 in which the same parts as those in FIG. In FIG. 2, the first delay means 7a and the second delay means 7b in FIG. 1 are used as common delay means. That is, reference numeral 11 in FIG. 2 is a capacitor which constitutes a delay means for delaying the rising and falling of the gate signal 5 for a fixed time.

When the gate signal 5 turns from off to on, a positive gate voltage 6p is first applied to the gate of the switching element 1 through the first resistor 2a, and then the capacitor 1
Because of 1, the gate voltage slowly rises to the positive gate power source 6p over a certain period of time. Therefore, when the switching element 1 is normally turned on, the first resistance and the second resistance are connected in parallel, so the gate resistance becomes small, and even if the noise current is superimposed on the main circuit current, the noise current is Therefore, the voltage fluctuation between the anode and the cathode of the switching element 1 is suppressed, so that an erroneous OFF operation is unlikely to occur, and the noise immunity in the steady ON state is increased.

In the steady state of OFF, the first resistor 2a and the second resistor 2b are connected in parallel, so that the gate resistance becomes small and the main circuit voltage applied to the anode / cathode of the switching element 1 may fluctuate. The noise current flowing through the floating capacitance between the anode and the gate easily flows to the gate resistance side due to the voltage fluctuation. Therefore, the voltage fluctuation between the anode and the cathode of the switching element 1 is also suppressed, so that the erroneous ON operation is less likely to occur, and the noise immunity in the steady OFF state is increased.

Further, when the gate signal 5 turns from ON to OFF, the negative gate voltage 6n is first applied to the gate of the switching element 1 via the first resistor 2a, and then the gate voltage for the capacitor 11 is applied. Slowly falls to the negative gate power source 6n over a certain period of time. Therefore, during the off-transition of the switching element 1, the voltage of the negative gate voltage source 6n is applied to the gate of the switching element 1 through only the first resistor 2a, and a surge voltage is generated during the off-transition. It will be difficult.

Next, an embodiment of the invention described in claim 3 will be described with reference to the block diagram of FIG. 3 in which the same parts as those in FIG. The difference between FIG. 3 and FIG. 1 is that the voltage of the positive and negative gate voltage sources 6p and 6n applied to the gate electrode of the switching element 1 via the first drive circuit is different from that of the second drive circuit. That is, the voltages of the positive and negative gate voltage sources 9p and 9n applied to the gate electrode of the switching element 1 are increased.

When the switching element 1 is turned off, the gate of the switching element 1 is driven only by the first drive circuit as in FIGS. 1 and 2, so that a surge voltage is generated when the switching element 1 is turned off. As mentioned above, it becomes difficult.

In a steady state in which the switching element 1 is turned from off to on, the auxiliary switching elements 3a and 3c are both turned on, and the gate of the switching element 1 is supplied with the positive gate voltage source 6p via the first resistor 2a. And the voltage of the positive gate voltage source 9p are applied via the second resistor 2c.

As described above, (the voltage of the positive gate voltage source 6p) <(the voltage of the positive gate voltage source 9p)
In the steady state in which the switching element 1 is turned from off to on, the gate voltage seen from the switching element 1 is increased to the positive side. Therefore, even if the noise current is superimposed on the main circuit current, the noise current easily flows to the second resistor 2c side, and the voltage fluctuation between the anode and the cathode of the switching element 1 is suppressed, so that it is erroneously turned off as described above. It becomes difficult and the noise immunity at the time of steady state of ON becomes high.

Similarly, in the steady state in which the switching element 1 is turned from ON to OFF, the auxiliary switching elements 3b and 3d are both conductive, and the gate of the switching element 1 is supplied with the negative gate voltage source via the first resistor 2a. 6n voltage,
The voltage of the negative gate voltage source 9n is applied via the second resistor 2c, but as described above, the (negative gate voltage source 6n
Voltage> of (the voltage of the negative gate voltage source 9n)>, the gate voltage seen from the switching element 1 increases to the negative side in a steady state where the switching element 1 is turned from ON to OFF. At this time, the anode of the switching element 1
Even if the main circuit voltage applied to the cathode fluctuates, the noise current flowing through the anode-gate stray capacitance easily flows to the second resistor 2c side due to the voltage fluctuation. Therefore, the voltage fluctuation between the anode and the cathode of the switching element 1 is also suppressed, so that the erroneous ON operation is less likely to occur, and the noise immunity in the steady OFF state is increased.

As described above, according to this embodiment, it is possible to suppress the surge voltage when the switching element 1 is off, and to obtain a high noise immunity when the switching element 1 is normally on and off.

Next, an embodiment of the invention described in claim 4 will be described with reference to the block diagram of FIG. 4 in which the same parts as those in FIG. In FIG. 4, reference numeral 10 denotes a switch that is closed when the switching element 1 is normally turned on and off. Therefore, when the switching element 1 is normally turned on and off, the second resistor 2b is connected in parallel to the first resistor 2a via the switch 10.

During the transition in which the gate signal 5 turns from on to off, the switching element 1 is driven by the first drive circuit via the first resistor 2a as described above,
As in the above, the surge voltage is less likely to occur.

On the other hand, when the switching element 1 is normally turned on and off, the second resistor 2b is connected in parallel to the first resistor 2a via the switch 10, so that the gate resistance seen from the switching element 1 is reduced. As a result, the noise immunity increases as described above.

Next, an embodiment of the invention described in claim 5 will be described with reference to the block diagram of FIG. 5 in which the same parts as those in FIG. In FIG. 5, 8 is an inverting circuit, 7b is a delay circuit, and this delay circuit is the second delay circuit 7b of FIG.
Equivalent to.

In the embodiment of FIG. 5, when the gate signal 5 transits from OFF to ON or from ON to OFF, the switching element 1 is driven by the first resistor 2a for the first drive as described above. Driven by the circuit,
Similar to the above, during the transition from on to off, surge voltage is less likely to occur.

On the other hand, even if the gate signal 5 turns from ON to OFF, the auxiliary switching element 3d is in the OFF state, so that the voltage of the positive gate voltage source 6p is applied to the gate of the switching element 1 via the second resistor 2b. There is no such thing.

However, when the gate signal 5 turns on from off, the gate potential of the auxiliary switching element 3d drops to the negative side with a predetermined time constant. Therefore, the first resistor 2a via the auxiliary switching element 3a, the second resistor 2b via the auxiliary switching element 3d, and the second resistor 2b via the auxiliary switching element 3a after a certain time after the gate signal 5 turns from off to on.
, The gate resistance seen from the switching element 1 is reduced, and as a result, the noise resistance in the steady ON state is increased as described above.

As described above, this embodiment can be applied to an application in which it is absolutely necessary to avoid the ON state priority, that is, the switching element in the ON state from being turned OFF. Next, an embodiment of the invention described in claim 6 will be described with reference to the configuration diagram of FIG. 6 in which the same parts as those in FIG.

In FIG. 6, reference numeral 8 is an inverting circuit and 7a is a delay circuit, which corresponds to the first delay circuit 7a in FIG. In the embodiment of FIG. 6, when the gate signal 5 transits from off to on or from on to off, the switching element 1 has the first resistor 2a as described above.
Driven by only the first drive circuit via
Similar to the above, during the transition from on to off, surge voltage is less likely to occur.

On the other hand, even if the gate signal 5 turns from off to on, the auxiliary switching element 3c is in the off state, so that the voltage of the negative gate voltage source 6n is applied to the gate of the switching element 1 via the second resistor 2b. There is no such thing.

However, when the gate signal 5 turns from ON to OFF, the gate potential of the auxiliary switching element 3c rises to the positive side with a predetermined time constant. Therefore, a certain time after the gate signal 5 turns from on to off, the first resistor 2a via the auxiliary switching element 3a and the second resistor 2b via the auxiliary switching element 3c become the gate of the switching element 1. Since each is connected, switching element 1
The gate resistance seen from
Similar to the above, the noise immunity in the steady off state is high.

As described above, the present embodiment can be applied to an application in which it is absolutely necessary to avoid the OFF state priority, that is, the ON state of the switching element in the OFF state. Next, the invention described in claim 7 will be described with reference to FIGS.

According to the seventh aspect of the invention, in FIG. 5, the voltage of the positive gate voltage source 6p is applied to the gate of the switching element 1 via the auxiliary switching element 3d. The gate voltage source 6p is set to 9p and (the voltage of the positive gate voltage source 6p) <(the voltage of the positive gate voltage source 9p), and in FIG. 6, the auxiliary switching element 3c is used. The voltage of the negative gate voltage source 6n is applied to the gate of the switching element 1.
And (the voltage of the negative gate voltage source 6n)> (the voltage of the negative gate voltage source 9n).

By doing so, when the switching element 1 is off, the gate of the switching element 1 is driven only by the first drive circuit as described above, so that a surge voltage is generated during the off transition. As mentioned above, it becomes difficult.

On the other hand, in the steady state in which the switching element 1 is turned from off to on, the auxiliary switching elements 3a and 3 are
d becomes conductive together, and the gate of the switching element 1 has the first
The voltage of the positive gate voltage source 6p is applied via the resistor 2a, and the voltage of the positive gate voltage source 9p is applied via the second resistor 2b.

As described above, since (the voltage of the positive gate voltage source 6p) <(the voltage of the positive gate voltage source 9p),
In the steady state in which the switching element 1 is turned from off to on, the gate voltage seen from the switching element 1 is high. At this time, even if the noise current is superimposed on the main circuit current, the noise current easily flows to the second resistor 2b side, and as described above, the noise immunity in the steady ON state becomes high.

Further, in the steady state in which the switching element 1 is turned from ON to OFF, the auxiliary switching elements 3b and 3c are provided.
Of the negative gate voltage source 6n and the second gate of the switching element 1 through the first resistor 2a
The voltage of the negative gate voltage source 9n is applied via the resistor 2b of 1. However, as described above, since (voltage of the negative gate voltage source 6n)> (voltage of the negative gate voltage source 9n), At the steady state when the switching element 1 is turned from ON to OFF,
The gate voltage seen from the switching element 1 increases to the negative side. At this time, even if the main circuit voltage applied to the anode / cathode of the switching element 1 fluctuates, the noise current flowing through the stray capacitance between the anode and the gate easily flows to the second resistor 2b side due to the voltage fluctuation. Therefore, the voltage fluctuation between the anode and the cathode of the switching element 1 is also suppressed, so that the erroneous ON operation is less likely to occur, and the noise immunity in the steady OFF state is increased.

As described above, according to the invention described in claim 7, it is possible to suppress the surge voltage when the switching element 1 is in the transient state of OFF, and to obtain a high noise immunity during the steady state of ON or the steady state of OFF.

In the above description, the magnitude relationship between the first gate resistance and the second gate resistance is not particularly limited, but the resistance value of the first gate resistance> the resistance value of the second gate resistance. It is preferable that the gate resistance is low in the steady state.

[0066]

As described above, according to the first aspect of the present invention, the gate voltage is applied to the gate of the switching element via the first resistor during the switching off transition, and the steady switching operation is performed. Sometimes, the gate voltage is applied to the gate of the switching element via the first resistor, and after the delay time of the first delay means after the ON command is given, or after the OFF command is given, the second voltage is applied. By applying the gate voltage to the gate of the switching element via the second resistor after the delay time of the delay means, the surge voltage can be suppressed during the switching off transition, and a large noise immunity can be obtained in the steady state.

The invention described in claim 2 is one in which the first delay means and the second delay means are one common delay means, and like the invention described in claim 1, A surge voltage can be suppressed during a switching off transition, and a large noise immunity can be obtained during a steady state.

Furthermore, the invention described in claim 3 is the same as claim 1.
In the invention according to claim 2 or the invention according to claim 2, the gate voltage applied to the gate of the switching element via the second resistor is higher than the gate voltage applied to the gate of the switching element via the first resistor. It is a higher one. As a result, similarly to the above, it is possible to suppress the surge voltage during a transition of switching off and obtain a large noise immunity during a steady state of on and off.

According to the invention described in claim 4, the first
A second resistor that is connected in parallel to the resistor is connected in parallel via a switch that closes when the switching element is normally on and off, and the gate resistance is increased during the transition of switching, and the gate resistance is decreased during the steady operation of switching. The surge voltage can be suppressed during the switching off transition, and a large noise immunity can be obtained during the steady state.

According to the invention described in claim 5, the gate voltage is applied to the gate of the switching element through the first resistor during the transition of the switching, and the gate voltage of the switching element is applied to the gate of the switching element during the steady state of the switching on. Applying the gate voltage via the first resistor, and applying the gate voltage to the gate of the switching element via the second resistor after the delay time of the delay means after the ON command is given. Thus, the surge voltage can be suppressed during the switching off transition, and a large noise immunity can be obtained during the on steady state.

According to the invention described in claim 6, the gate voltage is applied to the gate of the switching element via the first resistor during the transition of the switching, and the gate of the switching element is applied to the gate of the switching element when the switching is off. The first
By applying the gate voltage via the resistance of the switching element and applying the gate voltage to the gate of the switching element via the second resistance after the delay time of the delay means after the OFF command is given, the switching is turned off. The surge voltage can be suppressed during the transient of, and a large noise immunity can be obtained during the steady state of off.

Furthermore, according to the invention of claim 7,
In the invention according to claim 5 or the invention according to claim 6, the voltage applied to the gate of the switching element is higher than the gate voltage applied to the gate of the switching element via the first resistor. By increasing the gate voltage, the surge voltage can be suppressed in the transition of the switching off, and a large noise immunity can be obtained in the steady state of on or in the steady state of off, as described above.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the invention described in claim 1.

FIG. 2 is a configuration diagram showing an embodiment of the invention described in claim 2.

FIG. 3 is a configuration diagram showing an embodiment of the invention described in claim 3.

FIG. 4 is a configuration diagram showing an embodiment of the invention described in claim 4.

FIG. 5 is a configuration diagram showing an embodiment of the invention described in claim 5.

FIG. 6 is a configuration diagram showing an embodiment of the invention described in claim 6;

FIG. 7 is a configuration diagram showing a conventional embodiment.

[Explanation of symbols]

1 ... Switching element 2a ... 1st
2b ... Second resistances 3a to 3d ... Auxiliary switching element 4 ... Resistor 5 ... Gate signal 6p ... Positive gate voltage source 6n ... Negative gate voltage source 7a ... First delay means 7b ... Second
Means 8 ... Inversion circuit 9a ... Positive gate voltage source 9b ... Negative gate voltage source 10 ... Switch

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H03K 17/567

Claims (7)

[Claims] 1. When a turn-on command is given, a positive gate voltage is applied to the gate electrode of the switching element via a first resistance, and when a turn-off command is given, the first resistance is applied to the gate electrode of the switching element. A first drive circuit for applying a negative gate voltage through the gate electrode of the switching element, and a positive gate voltage that rises with a predetermined time constant through the first delay means when the ON command is given. To the gate electrode of the switching element by applying a negative resistance to the gate electrode of the switching element through a second delay means when the off command is given. A gate drive circuit for a switching element, which comprises a second drive circuit for applying a voltage via a resistor. 2. When a turn-on command is given, a positive gate voltage is applied to the gate electrode of the switching element via a first resistance, and when a turn-off command is given, the first resistance is applied to the gate electrode of the switching element. A first drive circuit for applying a negative gate voltage via a second gate, and a second gate circuit for applying a positive gate voltage to the gate electrode of the switching element, the positive gate voltage rising at a predetermined time constant via a delay means when the ON command is given. Is applied to the gate electrode of the switching element via the second resistor, and a negative gate voltage that decreases with a predetermined time constant is applied to the gate electrode of the switching element when the OFF command is given. A gate drive circuit for a switching element, which comprises a second drive circuit for applying the voltage as described above. 3. The gate electrode of the switching element is applied to the gate electrode of the switching element via the second drive circuit from the voltages of positive and negative gate voltage sources applied to the gate electrode of the switching element via the first drive circuit. 2. The voltage of the positive and negative gate voltage sources applied is increased.
Alternatively, the gate drive circuit of the switching element according to claim 2. 4. When a turn-on command is given, a positive gate voltage is applied to the gate electrode of the switching element through a first resistance, and when a turn-off command is given, the first resistance is applied to the gate electrode of the switching element. A first drive circuit for applying a negative gate voltage via a switch, and a second resistor connected in parallel to the first resistor via a switch that closes when the switching element is normally on and off. Device gate drive circuit. 5. When a turn-on command is given, a positive gate voltage is applied to the gate electrode of the switching element via a first resistance, and when a turn-off command is given, the first resistance is applied to the gate electrode of the switching element. A first drive circuit for applying a negative gate voltage via a gate, and a positive gate voltage rising at a predetermined time constant via a delay means to the gate electrode of the switching element when the ON command is given. A gate drive circuit for a switching element, comprising a second drive circuit for applying a voltage via a second resistor. 6. When a turn-on command is given, a positive gate voltage is applied to the gate electrode of the switching element via a first resistance, and when a turn-off command is given, the first resistance is applied to the gate electrode of the switching element. A first drive circuit for applying a negative gate voltage via a second gate circuit; and a second gate circuit for applying a negative gate voltage to the gate electrode of the switching element, the negative gate voltage decreasing with a predetermined time constant via a delay means when the off command is given. And a second drive circuit for applying the voltage via the resistance of the gate drive circuit of the switching element. 7. The voltage of a positive gate voltage source applied to the gate electrode of the switching element via the first drive circuit, or applied to the gate electrode of the switching element via the first drive circuit. From the voltage of the negative gate voltage source, the voltage of the positive gate voltage source applied to the gate electrode of the switching element via the second drive circuit, or the gate of the switching element via the second drive circuit. 7. The gate drive circuit for a switching element according to claim 5, wherein the voltage of the negative gate voltage source applied to the electrodes is increased.