JPH0653796A - Drive circuit for switching element - Google Patents

Abstract

PURPOSE:To prevent mis-ignition of the switching element by connecting a capacitor and a diode between a base terminal and an emitter terminal of the switching element and adding a resistor in parallel with the diode. CONSTITUTION:When a voltage with a high dv/dt is applied between a collector and an emitter of a transistor(TR) 1 in the turn-off state, a current resulting from the dv/dt with a steep rising in the direction from the collector to the base flows through a junction capacitor 4 between the collector and the base of the TR 1. When a wiring distance between a reverse bias power supply 3 and the TR 1 is long and a wiring impedance 5 is in existence, the dv/dt current does not flow into the reverse bias power supply 3 but is absorbed by a capacitor 2 through a diode 6. Thus, no dv/dt current flows into the base of the TR 1 and the TR 1 is not turned on. Furthermore, even after the dv/dt current is absorbed by the capacitor 2 and the capacitor 2 is charged up, a resistor 7 is inserted in series to the capacitor 2 in the wiring path on the discharge side of the capacitor 2 and the vibration at the discharge side is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching element drive circuit for driving a switching element used in a power converter or the like.

[0002]

2. Description of the Related Art In a switching element, a base (B) -emitter (E) or a gate (G) -cathode (C) is reverse-biased, that is, a collector-emitter (or a turn-off state). When a high (dv / dt) is applied between the anode and the cathode (for example, when the fly-hole diode connected in anti-parallel with the switching element reversely recovers), the collector-
A current having a sharp rise (dv / dt) flows from the collector to the base (or the anode to the gate) through the junction capacitance between the bases (or between the anode and the gate).

When the wiring distance between the reverse bias power source and the switching element is long, the (dv / dt) current does not flow into the reverse bias power source but flows from the base (or gate) of the switching element toward the emitter (or cathode), It may turn on the switching element. If the switching element in the off state is turned on by mistake, the power converter may be broken due to a short circuit or the like.

FIG. 2 shows an example of a conventional circuit configuration. In FIG. 2, 1 is a transistor as an example of a switching element,
2 is a capacitor, 3 is a reverse bias power supply, 4 is a junction capacitance between the collector (C) and the base (B) of the transistor 1, 5
Is the wiring impedance between the reverse bias power source 3 and the transistor 1. In such a circuit example, (dv
/ Dt) so that the current does not flow into the base of the transistor 1, the base (B) to the emitter (E) of the transistor 1
The capacitor 2 was connected between them to absorb the (dv / dt) current.

[0005]

However, in such a conventional method, the (dv / dt) current is temporarily reduced to the capacitor 2
Will be absorbed by the
Resonance occurs between the wiring impedance 5 and the wiring impedance 5, and the voltage across the capacitor 2, that is, the base-emitter voltage of the transistor 1 becomes oscillating.

When the voltage across the capacitor 2 rises above the minimum base-emitter voltage required to turn on the transistor 1 in the course of this oscillation, the wiring impedance between the capacitor 2 and the transistor 1 is small, so that the capacitor 2 is connected to the silane transistor. A discharge current having a sharp rising and large peak value flows into the base of No. 1 and eventually turns on the transistor 1. Furthermore, the peak value of the oscillation voltage between the base and the emitter may exceed the reverse breakdown voltage between the base and the emitter of the transistor 1.

[0007]

In order to solve the above problems, the present invention provides a series circuit of a capacitor and a diode between a base and an emitter (or between a gate and a cathode) of a switching element, and a cathode of the diode is a switching element. Is connected so as to face the emitter side (or cathode side), and a resistor is connected in parallel with the diode.

[0008]

With this configuration, a resistor is inserted in series with the capacitor in the wiring path on the discharge side of the capacitor even after the capacitor is charged by absorbing the (dv / dt) current through the diode into the capacitor. Due to
Vibration on the discharge side is suppressed by the vibration control effect of this resistance.

Therefore, the base of the switching element
The emitter-to-emitter (or gate-to-assode) voltage is not oscillatory, and it is extremely unlikely to rise above the minimum base-to-emitter (or gate-to-cathode) voltage to turn on the switching element. Even if the voltage rises above the above voltage, the discharge current of the capacitor becomes a current with a gradual rise and a small peak value due to the action of the resistor, so the switching element is not turned on and is slowly drawn to the reverse bias power supply. .

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the essential structure of one embodiment of the present invention, in which 6 is a diode and 7 is a resistor. In the figure, the same reference numerals as those in FIG. 2 indicate parts having the same functions. That is, between the base (B) and the emitter (E) of the transistor 1, a diode 6 having the illustrated polarity is connected in series with the capacitor 2, and a resistor 7 is connected in parallel with the diode 6.

When a high (dv / dt) is applied between the collector and the emitter of the transistor 1 in the turned-off state, the junction capacitance 4 between the collector and the base of the transistor 1 is increased.
A current (dv / dt) having a steep rise flows from the collector to the base. Reverse bias power supply 3
If the wiring distance between the transistor 1 and the transistor 1 is long and the wiring impedance 5 exists, the (dv / dt) current will flow in the reverse bias power source 3
Does not flow into the capacitor 2 and is absorbed by the capacitor 2 through the diode 6. Therefore, the (dv / dt) current does not flow into the base of the transistor 1 and the transistor 1 is not turned on.

Further, even after the capacitor 2 is charged by absorbing the (dv / dt) current, the resistor 7 is inserted in series with the capacitor 2 in the wiring path on the discharge side of the capacitor 2. Therefore, the vibration suppressing effect of the resistor 7 suppresses the vibration on the discharge side. Therefore,
The base-emitter voltage of the transistor 1 is not oscillating and the possibility of rising above the minimum base-emitter voltage for turning on the transistor 1 can be very low. Even if the voltage rises above the above voltage, the discharge current of the capacitor 2 becomes a current with a gradual rise and a small peak value due to the action of the resistor 7. Therefore, the transistor 1 is not turned on and is slowly pulled to the reverse bias power source. It will be pulled out.

[0013]

As described above, according to the present invention, a simple circuit in which only a diode and a resistor are added can prevent false switching of a switching element, that is, a switching element in an off state is accidentally turned on. Can be prevented
This means that it is possible to prevent short-circuit breakdown of devices such as power converters. Further, since the vibration is suppressed by the action of the attached resistance, it is possible to eliminate the fear that the voltage between the base and the emitter exceeds the reverse breakdown voltage.

[Brief description of drawings]

[0014]

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

FIG. 2 is a circuit diagram showing a conventional configuration example.

[0015]

[Explanation of symbols]

 1 Switching element 2 Capacitor 3 Reverse bias power supply 4 Junction capacitance 5 Wiring impedance 6 Diode 7 Resistance

Claims (1)

[Claims] 1. A switching element drive circuit for driving a switching element used in a power converter or the like,
A series circuit of a capacitor and a diode is provided between the base terminal (or gate terminal) of the switching element and the emitter terminal (or cathode terminal) of the switching element, and the diode is oriented toward the emitter terminal side (or cathode terminal side) of the switching element. And a resistor connected in parallel to the diode.