JP4284575B2 - Gate drive circuit for power semiconductor device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gate drive circuit for driving a gate of a power semiconductor element constituting a power conversion device such as an inverter.
[0002]
[Prior art]
FIG. 9 shows a general example of an inverter using an IGBT (insulated gate bipolar transistor) as a power semiconductor element.
In the figure, 1 is a DC power supply circuit, 2 is an inverter circuit composed of an IGBT and a diode for converting DC to AC, 3 is a drive circuit of the IGBT, and 4 is a load such as a motor. The drive circuit 3 is provided for each element.
[0003]
FIG. 10 shows a specific example of the drive circuit used in FIG.
A circuit 6 generates an on / off signal according to a control signal 7 from a control circuit (not shown), 8 (SW1) is a switch element for turning on the IGBT, and 9 is a gate resistor for turning on. Further, 10 (SW2) and 11 (SW3) are switch elements for turning off the IGBT, and 12 and 13 are gate resistors for turn-off.
[0004]
FIG. 11 shows an operation waveform when the IGBT is turned off.
In order to reduce the turn-off loss at the time of turn-off, by turning on both SW2 and SW3 during the storage period at the time of IGBT turn-off, driving is performed with a low resistance gate resistance in which resistors 12 and 13 are paralleled. Is. This shortens the storage period and reduces turn-off loss.
On the other hand, during the fall period, in order to suppress the surge voltage generated by the wiring inductance and IGBT di / dt (realized by suppressing IGBT di / dt), SW3 is turned off and a high resistance gate resistance (resistance 12) Drive with. Thereby, di / dt of the IGBT is suppressed, and as a result, the surge voltage is reduced.
[0005]
FIG. 12 shows operation waveforms when driving with only a low resistance. Since di / dt of IGBT becomes large, the surge voltage becomes high like a dotted line.
FIG. 13 shows operation waveforms when driving with only a high resistance. Since the IGBT storage period becomes longer as indicated by the dotted line, the turn-off loss increases.
FIG. 14 is an explanatory diagram of switching timing from low resistance to high resistance.
Normally, as a timing for switching from low resistance to high resistance (timing for turning off SW3), for example, as shown in FIG. 14A, the voltage between the collector and emitter of the IGBT is detected by a circuit 14, and the detected value is a comparator. It is after the time T1 set by the delay circuit 16 after detecting that the circuit 15 has reached a certain set value (Vth). Thereafter, SW3 is turned off for a certain set period (T2) by the one-shot circuit 17 and the logic circuits 18 and 19.
[0006]
[Problems to be solved by the invention]
By the way, there are characteristic variations and temperature characteristics in the parts and elements constituting the gate drive circuit. Therefore, for example, the delay time (T1) of the delay circuit 16 is not exactly equal to T1 because the design value varies in an actual circuit. When the actual circuit becomes shorter by Δt than the design value (T1) of the delay time due to this variation, for example, as shown in FIG. Therefore, there is a problem that the turn-off loss increases as compared with the case where the device operates at the design value.
Accordingly, an object of the present invention is to prevent an increase in turn-off loss even if component and element characteristics vary.
[0007]
[Means for Solving the Problems]
In order to solve such a problem, in the invention of claim 1, in the gate drive circuit for driving the power semiconductor element constituting the power converter,
A first detection circuit for detecting that the gate-emitter voltage of the power semiconductor element has reached a set voltage; and a second detection for detecting a time equivalent amount from a predetermined set time to the set voltage. A circuit, a determination circuit that compares the detected time equivalent amount with a set time equivalent amount to determine its magnitude, and a resistance value change circuit that changes the gate resistance value based on the output signal of the determination circuit It is characterized by.
[0008]
In the invention of claim 2, in the gate drive circuit for driving the power semiconductor element constituting the power converter,
A first detection circuit for detecting that the gate-emitter voltage of the power semiconductor element has reached a set voltage; and a second detection for detecting a time equivalent amount from a predetermined set time to the set voltage. A circuit, a third detection circuit that compares the detected time equivalent amount with a set time equivalent amount and detects the difference, and a resistance value change circuit that changes the gate resistance value according to the difference are provided. It is characterized by.
[0009]
In the invention of claim 3, in the gate drive circuit for driving the power semiconductor element constituting the power converter,
A first detection circuit for detecting that the gate-emitter voltage of the power semiconductor element has reached a set voltage; and a second detection for detecting a time equivalent amount from a predetermined set time to the set voltage. A circuit, a determination circuit for comparing the detected time equivalent amount with a set time equivalent amount, and determining the magnitude thereof, and based on an output signal of the determination circuit, from a certain set time at turn-off, from a low resistance And a time changing circuit for changing a time until switching to a high resistance gate resistance.
[0010]
In the invention of claim 4, in the gate drive circuit for driving the power semiconductor element constituting the power conversion device,
A first detection circuit for detecting that the gate-emitter voltage of the power semiconductor element has reached a set voltage; and a second detection for detecting a time equivalent amount from a predetermined set time to the set voltage. A circuit, a third detection circuit that compares the detected time equivalent amount with a set time equivalent amount and detects a difference thereof, and according to the difference, from a certain set time at turn-off, from a low resistance And a time changing circuit for changing a time until switching to a high resistance gate resistance.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a block diagram showing a first embodiment of the present invention. Only the differences from the conventional example of FIG. 10 will be mainly described below.
Compared with the conventional example of FIG. 10, the comparator circuit 20 detects that the gate-emitter voltage (Vge) of the IGBT has reached a certain threshold value (Vthge), the output of this circuit 20 and the output of the delay circuit 16 A logical product circuit (logic circuit) 21 that takes the logical product of the above, a one-shot circuit 22 that outputs a signal of a certain time width triggered by the rise of the output signal of the delay circuit 16, the output of the logical circuit 21 to the D terminal, A D-type flip-flop (DFF) 23 or the like, to which the output of the one-shot circuit 22 is input to a clock terminal, is added.
[0012]
Therefore, if the signal output time of the circuit 21 is longer than the signal output time of the circuit 22 (for example, the case where the delay time T1 is shorter than the design value), the output of the DFF 23 becomes high (H) and passes through the logic circuit 24. SW4 is turned on. As a result, the resistor 25 is added as a gate resistor, so that the resistance value decreases, the turn-off operation is accelerated, and the increase in loss is suppressed.
FIG. 2 shows the operation at this time, and shows how the turn-off operation is accelerated by shifting the broken line waveform of Vce, ic shown at the top of FIG. 2 to a thick line waveform. If the signal output time of the circuit 21 is shorter than the signal output time of the circuit 22, SW4 is turned off and driven with a turn-off loss as designed (or less than the designed value).
[0013]
FIG. 3 is a block diagram showing a second embodiment of the present invention.
This is configured by adding logic circuits 26 and 27, an integration circuit 28, a comparator group circuit 29 and the like to the circuit shown in FIG. That is, a signal corresponding to the difference between the output times of the circuits 21 and 22 is generated by the logic circuits 26 and 27, and the difference time is converted into a voltage by the integrating circuit 28. Then, the converted voltage signal is input to the comparator group circuit 29, the switches (SW5 to SW7) are turned on according to the difference time, and the IGBT is driven with an appropriate gate resistance value. As for the relationship between the difference time and the switch, for example, the switch (SW5 to SW7) is selected so that the degree of low resistance increases as the difference time increases, and the degree of low resistance decreases as the difference time decreases. And Although three switches SW5, SW6, and SW7 are used here, the number of switches is not limited to this number.
[0014]
FIG. 4 shows a modification of FIG. It is characterized in that a voltage-resistance conversion circuit 30 is provided instead of the comparator group circuit 29 of FIG. The circuit 30 has a high resistance when the input voltage is small and a low resistance when the input voltage is large. Specifically, the circuit 30 can be easily realized by using an on-voltage characteristic with respect to the gate voltage of the MOSFET. It is.
[0015]
FIG. 5 is a block diagram showing a third embodiment of the present invention.
This is characterized in that a switch circuit 31 and a delay circuit 32 are added to that shown in FIG. That is, when the output of the circuit 24 is “H”, the switching timing of the gate resistor (the timing at which the SW3 is turned off) is switched from the delay circuit 16 to the delay circuit 32 in which the delay time is set longer than that of the circuit 16. ) To reduce the increase in loss. Note that if the signal output time of the circuit 21 is shorter than that of the circuit 22, the circuit 16 operates, so that the element can be driven with a turn-off loss as designed (or below).
[0016]
FIG. 6 is a block diagram showing a fourth embodiment of the present invention.
This is configured by adding a decoder circuit 33, a switch circuit 34, delay circuits 35, 36, and the like to that shown in FIG. That is, by inputting the output signal of the comparator group circuit 29 to the decoder circuit 33 and operating the switch circuit 34 in accordance with the decoded signal, an appropriate value corresponding to the magnitude of the difference time between the output signals of the circuit 21 and the circuit 22 is obtained. The gate resistance is switched by a delay time (a switch is selected to increase the delay time if the difference time is large, and to decrease the delay time if the difference time is small). Although three delay circuits 16, 34, and 35 are provided here, it is needless to say that the number is not limited to this number.
[0017]
FIG. 7 shows a modification of FIG.
This has one delay circuit, and the delay time can be adjusted. That is, the delay circuit is normally configured using an RC time constant as shown in FIG. 8A. Here, for example, as shown in FIG. 8B, the delay circuit shown in FIG. A voltage-resistance conversion circuit 38 similar to that used in the above is connected. As a result, the delay circuit 37 can have a higher resistance (longer delay time) as its input voltage is larger (delay time is shorter). The voltage-resistance conversion circuit 38 can be realized by using an on-voltage characteristic with respect to the gate voltage of the MOSFET as in the case of FIG.
In the above description, the IGBT has been mainly described as an example. However, the present invention can be applied to a power semiconductor element such as a field effect transistor (FET) similar to the IGBT.
[0018]
【The invention's effect】
According to the present invention, the time until the IGBT gate-emitter voltage reaches the set voltage is detected, and the gate resistance value or the internal circuit constant is adjusted according to the time. It is possible to reduce the increase in turn-off loss.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a first embodiment of the present invention;
FIG. 2 is a waveform diagram for explaining the operation of FIG. 1;
FIG. 3 is a block diagram showing a second embodiment of the present invention.
4 is a configuration diagram showing a modification of FIG. 3; FIG.
FIG. 5 is a block diagram showing a third embodiment of the present invention.
FIG. 6 is a block diagram showing a fourth embodiment of the present invention.
7 is a configuration diagram showing a modification of FIG. 6;
FIG. 8 is a circuit diagram showing a specific example of a delay circuit used in FIG. 7;
FIG. 9 is a schematic diagram showing a conventional example of an inverter main circuit.
FIG. 10 is a circuit diagram showing a specific example of a general IGBT drive circuit.
11 is an operation explanatory diagram at the time of turn-off in FIG. 10;
12 is an operation explanatory diagram of FIG. 10 when driven by only a low resistance.
13 is an operation explanatory diagram of FIG. 10 when driven by only a high resistance.
14 is an explanatory diagram of a switching timing example from a low resistance to a high resistance in FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... DC power supply circuit, 2 ... Inverter circuit, 3 ... Drive circuit, 4 ... Load, 5 ... Power supply, 6 ... ON, OFF signal generation circuit, 8, 10, 11 ... Switch element, 9, 12, 13, 25 ... Gate resistor, 14 ... voltage detection circuit, 15, 20 ... comparator circuit, 16, 32, 35, 36, 37 ... delay circuit, 17, 22 ... one-shot circuit, 18, 19, 21, 24, 26, 27 ... logic Reference numeral 23: D-type flip-flop circuit (DFF) 28: Integration circuit 29: Comparator group circuit 30, 38: Voltage-resistance conversion circuit 31, 34: Switch circuit 33: Decoder circuit

Claims (4)

In a gate drive circuit for driving a power semiconductor element constituting a power converter,
A first detection circuit for detecting that the gate-emitter voltage of the power semiconductor element has reached a set voltage; and a second detection for detecting a time equivalent amount from a predetermined set time to the set voltage. A circuit, a determination circuit that compares the detected time equivalent amount with a set time equivalent amount to determine its magnitude, and a resistance value change circuit that changes the gate resistance value based on the output signal of the determination circuit A gate drive circuit for a power semiconductor element. In a gate drive circuit for driving a power semiconductor element constituting a power converter,
A first detection circuit for detecting that the gate-emitter voltage of the power semiconductor element has reached a set voltage; and a second detection for detecting a time equivalent amount from a predetermined set time to the set voltage. A circuit, a third detection circuit that compares the detected time equivalent amount with a set time equivalent amount and detects the difference, and a resistance value change circuit that changes the gate resistance value according to the difference are provided. A gate drive circuit for a power semiconductor element. In a gate drive circuit for driving a power semiconductor element constituting a power converter,
A first detection circuit for detecting that the gate-emitter voltage of the power semiconductor element has reached a set voltage; and a second detection for detecting a time equivalent amount from a predetermined set time to the set voltage. A circuit, a determination circuit for comparing the detected time equivalent amount with a set time equivalent amount, and determining the magnitude thereof, and based on an output signal of the determination circuit, from a certain set time at turn-off, from a low resistance A gate drive circuit for a power semiconductor element, comprising: a time change circuit for changing a time until switching to a high resistance gate resistance. In a gate drive circuit for driving a power semiconductor element constituting a power converter,
A first detection circuit for detecting that the gate-emitter voltage of the power semiconductor element has reached a set voltage; and a second detection for detecting a time equivalent amount from a predetermined set time to the set voltage. A circuit, a third detection circuit that compares the detected time equivalent amount with a set time equivalent amount and detects a difference thereof, and according to the difference, from a certain set time at turn-off, from a low resistance A gate drive circuit for a power semiconductor element, comprising: a time change circuit for changing a time until switching to a high resistance gate resistance.

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