JP2751179B2 - Gate circuit of power switching element - Google Patents

Description

Description: Object of the Invention (Industrial Application Field) The present invention relates to a gate circuit for switchingly driving a power switching element.

(Prior Art) Conventionally, a drive circuit for switchingly driving various electric devices uses, for example, an electrostatic induction transistor (hereinafter referred to as SIT) as a power switching element as shown in FIG. When the ON signal SG4 is input to the base terminal of the transistor Tr3
Is turned on, and when a gate current in the direction of arrow A flows through the power switching element SIT based on the collector current, the power switching element SIT is turned on. On the other hand, turning off the power switching element SIT in such an ON state is performed by flowing a gate current in the opposite direction to the power switching element SIT. That is,
Off signal S is applied to the base terminal of off-gate transistor Tr4.
When G5 is input, the transistor Tr4 is turned on based on the off-gate power supply E5, a gate current flows in the power switching element SIT in the direction of arrow B based on the collector current, and the power switching element SIT is turned off.

According to the gate circuit as described above, the gate current to the power switching element SIT by the on-gate transistor Tr3 is always constant based on the collector resistance R8 of the transistor Tr3. The saturation drain current flowing through the device SIT changes depending on the load provided. Therefore, when the drain current becomes small due to a large load resistance, the gate current becomes unnecessarily large and consumes unnecessary power. With a small load resistance, the drain current becomes large, and in some cases, the gate current becomes large. However, there is a problem that the power switching element becomes unsaturated and the power loss increases.

In addition, as shown by the characteristic curve C in FIG. 4, in the saturation state of the power switching element SIT, the turn-off time of the power switching element SIT becomes longer as the drain current becomes smaller when the gate current is constant, that is, as the supersaturation occurs. There is a property that. Therefore, when the drain-in current changes due to a change in the load resistance of the power switching element SIT, there is a problem that the turn-off time of the power switching element SIT changes and the control operation of the device becomes unstable. An object of the present invention is to keep the drain-source voltage constant even when the drain current changes with a change in the load resistance of the power switching element, to perform the switching operation reliably, to prevent the fluctuation of the turn-off time, and to uselessly. It is an object of the present invention to provide a gate circuit of a power switching element capable of preventing power consumption.

SUMMARY OF THE INVENTION (Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a method of making a drain-source voltage of an ON state of a power switching element equal to a preset reference voltage. A gate current adjusting circuit that supplies a pulse-like gate current by controlling the transistor connected to the gate of the power switching element on and off based on the comparison result between the gate voltage of the power switching element and the reference voltage. The configuration is connected.

(Operation) By the above means, the transistor is turned on / off to the power switching element, and a pulse-like gate current is supplied, the drain-source voltage of the power switching element is held substantially at the reference voltage, and the power consumption in the power switching element is reduced. Is reduced, and the transistor that supplies the gate current to the power switching element is turned on and off, so that the power consumption of the transistor is reduced.

(Embodiment) An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. The power switching element SIT
Is connected to the emitter of the first transistor Tr1 for on-gate, the collector of the first transistor Tr1 is connected to the power supply E1 for on-gate via the resistor R1, and the resistor R2 is connected between the base and the collector. Is connected.

The non-inverting input terminal of the comparator 2 is connected to the drain of the power switching element SIT.
Is connected to the source of the power switching element SIT via the reference power supply E2. Comparator 2
The first transistor Tr1 through the output terminal resistance R5 of
Connected to the base. The comparator 2 is a power switching element SIT input to the non-inverting input terminal.
Drain-source voltage Vds and reference power supply voltage Vs (second
(See Fig. (C)) and compare the drain-source voltage Vd
If s is higher than the reference power supply voltage Vs, the H level signal SG3
By outputting the signal SG3 at the L level when the signal is low, a pulse-like output signal SG3 is output as shown in FIG. 2 (d). Then, when an H level signal SG3 is output from the comparator 2, the first transistor Tr1 is turned on and the power switching element SIT is supplied to the power switching element SIT as shown in FIG.
And the drain-source voltage V
When ds falls and the signal SG3 at L level is output, the first transistor Tr1 is turned off and the power switching element S
Since the gate current Ig2 of IT is cut off, the drain-source voltage Vds increases. Therefore, a gate current adjusting circuit that adjusts the gate current Ig2 of the power switching element SIT by the comparator 2, the reference power supply E2, and the first transistor Tr1 is configured.

The collector of the second transistor for off-gate Tr2 is connected to the gate of the power switching element SIT via a resistor R6, and an off-gate power supply E3 is connected between the emitter of the transistor Tr2 and the source of the power switching element SIT. It is connected. And the second transistor
When the off signal SG1 shown in FIG. 2 (a) is input to the base of Tr2, the transistor Tr2 is turned on, and a collector current flows from the power supply E3 for off gate via the power switching element SIT.
SIT is turned off.

The collector of the second transistor Tr2 is connected to the base of the first transistor Tr1 via the resistor R7.

By the way, in the above-described gate circuit, the power switching element SIT is always on when the off signal SG1 is not input to the second transistor Tr2. That is, from the on-gate power supply E1 through the resistor R2, the first transistor
A base current flows through Tr1, and as shown in FIG.
Based on the base current, the collector current flowing through the transistor Tr1 becomes the gate current Ig2 for the power switching element SIT, and the power switching element SIT is kept on. At this time, the power switching element SI
When the load resistance of T is small and the drain current Id shown in FIG. 2B increases, the drain-source voltage Vds shown in FIG. 2C becomes higher than the reference power supply voltage Vs. The level output signal SG3 is output to the base of the first transistor Tr1. Then, the first transistor Tr1 turns on and the power switching element SIT
Then, the gate current Ig2 shown in FIG. 2 (e) flows, and the drain-source voltage Vds decreases.

On the other hand, the drain-source voltage Vds is equal to the reference power supply voltage Vs
If lower, the comparator 2 outputs an L level signal SG
Outputs 3. Then, the first transistor Tr1 is turned off and the gate current Ig2 of the power switching element SIT is cut off, so that the drain-source voltage Vds increases.
Accordingly, as shown in FIG. 2C, the drain-source voltage Vds of the power switching element SIT is equal to the drain current Id.
Irrespective of the magnitude of the reference power supply voltage Vs.

On the other hand, when the off signal SG1 is input to the base of the second transistor Tr2 from the state where the power switching element SIT is on, the second transistor Tr2 is turned on,
The base current flowing to the first transistor Tr1 from the on-gate power supply E1 via the resistor R2 is cut off as the collector current of the second transistor Tr2 via the resistor R7, so that the first transistor Tr1 is turned off. . At the same time, a collector current flows from the off-gate power supply E3 to the second transistor Tr2 via the power switching element SIT and the resistor R6, and the collector current flows to the power switching element SI.
For T, the gate current becomes a direction opposite to the gate current in the ON state, and the power switching element SIT is turned off.

As described above, in this gate circuit, the pulse-like gate current Ig2 is supplied to the power switching element SIT, and the drain-source voltage Vds of the power switching element SIT is substantially maintained at the reference power supply voltage Vs. Therefore, power consumption can be reduced, and the turn-off time can be kept constant even if the load resistance changes. Also, the first
Transistor Tr1 is used as a switch for supplying a pulsed gate current Ig1 to the power switching element SIT, so that the power consumption of the first transistor Tr1 can be reduced.

The power switching element may use a bipolar transistor BPT or the like in addition to the above-described electrostatic induction transistor SIT.

Effect of the Invention As described in detail above, the gate circuit of the present invention controls the transistor connected to the gate to on / off so that the voltage between the drain and the source of the power switching element matches the reference voltage to generate a pulse-like gate current. An excellent effect of reducing power consumption in the power switching element and reducing power consumption in the transistor while performing the switching operation by the supply is achieved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a gate circuit according to an embodiment of the present invention, FIG. 2 is a waveform diagram showing its operation, FIG. 3 is a circuit diagram of a conventional gate circuit according to the present invention, and FIG. FIG. 4 is an explanatory diagram showing turn-off characteristics of a power switching element. 2 ... Comparator (gate current control circuit), E2 ... Reference power supply, SIT ... Power switching element, Tr1 ... Transistor.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yuichi Mizutani 2-1-1, Toyota-cho, Kariya-shi, Aichi Pref. Sho 62-207021 (JP, A)

Claims (1)

(57) [Claims] 1. A method for comparing a drain-source voltage with a reference voltage so that a drain-source voltage of an on-state of a power switching element matches a preset reference voltage, and based on the comparison result, the power switching A gate circuit for a power switching element, characterized in that a gate current adjusting circuit for supplying a pulse-like gate current by turning on / off a transistor connected to the gate of the element is connected to the gate of the power switching element.