JPH05243943A - Drive circuit for current driven type semiconductor switch - Google Patents

Abstract

PURPOSE:To reduce power loss in respect of a drive circuit for a current driven type semiconductor switch. CONSTITUTION:An inductor 2 is connected between a switching element SW1 connected to power supply E1 and a grounded switching element SW2, and a diode 3 to make a reverse bias is connected to a junction (a) between the switching element SW1 and the inductor 2, and the base of an emitter-grounded main transistor Q is connected to the junction (b) between the inductor 2 and the switching element SW2, and a control part 4 to output a control signal which supplies a current based on energy stored in the inductor 2 to the base of the main transistor Q by turning off the switching elements SW1, SW2 after storing the energy in the inductor 2 by turning on the switching elements SW1, SW2, and after that, grounds the inductor 2 by turning on the switching element SW2, and turns on the switching element SW1 after the current IL based on the energy stored in the induct>or becomes zero is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive circuit for a current drive type semiconductor switch.

[0002]

2. Description of the Related Art Conventionally, a semiconductor switch capable of high-speed on / off control has been used for controlling power supply to a load. There is a circuit shown in FIG. 4 as a drive circuit when a current drive type semiconductor switch (for example, a bipolar transistor) is used as the semiconductor switch. That is, the switching transistor 31 whose emitter is grounded is connected to the load 3
It is connected via 2 to the power source EL for driving the load.
The base of the switching transistor 31 is a resistor R
1 and the switching element 33 to connect to the power supply E1.

On / off control of the switching element 33 is performed by a control signal from a driver (not shown), and when the switching element 33 is turned on, the power source E1.
From the switching transistor 31 via the resistor R1
A base current is supplied to the base of the switching transistor 31 and the switching transistor 31 is turned on. When the switching element 33 is turned off, the base current is not supplied to the base of the switching transistor 31 and the switching transistor 31 is turned off.
That is, the switching transistor 31 is turned on / off by the on / off control of the switching element 33.

[0004]

However, in the drive circuit, since the base current is supplied from the power source E1 to the base of the switching transistor 31 via the resistor R1, there is a problem that the power loss due to the resistor R1 is large. ..

The present invention has been made to solve the above problems, and an object of the present invention is to provide a drive circuit for a current drive type semiconductor switch capable of reducing power loss.

[0006]

In order to solve the above problems, the present invention provides an energy storage inductor between a first switching element connected to a power source and a second switching element grounded. And a diode that is reverse biased and grounded is connected to the connection point between the first switching element and the inductor, and the emitter or drain is grounded to the connection point between the inductor and the second switching element. Connected to the control electrode of the current-driven semiconductor switch, further turning on the first and second switching elements to store energy in the inductor, and then turning off the first and second switching elements. After supplying a current based on the energy stored in the control electrode of the current-driven semiconductor switch, the second switching element is turned on. Grounded inductor Te, current based on the energy stored in the inductor from becomes zero, and its gist in that a control unit for outputting a control signal for turning on the first switching element.

[0007]

When the control unit turns on the first and second switching elements, energy is stored in the inductor by the power supply. When the control unit turns off the first and second switching elements, the current based on the energy accumulated in the inductor becomes a loop current passing through the control electrode, the emitter or the drain of the current-driven semiconductor switch, the diode and the inductor, and the current The drive type semiconductor switch is turned on.

Next, when the control section turns on the second switching element, the inductor is grounded, so that the current based on the energy stored in the inductor is not supplied to the control electrode of the current-driven semiconductor switch, and the current is reduced. The drive type semiconductor switch is turned off. After that, the control unit turns on the first switching element after the current based on the energy of the inductor becomes zero.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is embodied in a bipolar transistor will be described below with reference to FIGS.

As shown in FIG. 1, the main transistor Q, which is a bipolar transistor, has its emitter grounded, and its collector is connected to a load driving power source EL via a load 1 such as a motor. A switching element SW1 is connected to the power source E1, and one end of an inductor 2 is connected to the switching element SW1. The other end of the inductor 2 has a switching element SW2 grounded.
Are connected.

A reverse-biased diode 3 is grounded and connected to a connection point a between the switching element SW1 and the inductor 2. In addition, the inductor 2
The base of the main transistor Q is connected to a connection point b between the switching element SW2 and the switching element SW2.

A control unit 4 is connected to the switching elements SW1 and SW2, and each switching element SW1 and SW2 is connected.
2 outputs an on / off control signal.
That is, the control unit 4 outputs the ON signal to each of the switching elements SW1 and SW2, and then simultaneously outputs the ON signal.
1, OFF signal is output to SW2. Then, the control unit 4 outputs the ON signal only to the switching element SW2, and after the current based on the energy accumulated in the inductor 2 becomes zero, the switching elements SW1 and SW2 are turned on again to turn them on. An ON signal is output to SW1.

Next, the operation of the drive circuit configured as described above will be described. In a state where the switching element SW2 is turned on based on the ON signal of the control section 4 and the switching element SW1 is turned off based on the OFF signal of the control section 4, current is supplied to the base of the main transistor Q. Therefore, the main transistor Q is off.

In this state, when the control section 4 outputs an ON signal to the switching element SW1, the switching element SW1 is turned on. Then, energy is accumulated in the inductor 2 by the power source E1. Then, after the energy is stored in the inductor 2, the control unit 4 outputs an ON signal to each of the switching elements SW1 and SW2. Therefore, the switching elements SW1 and SW2 are turned off.

Therefore, a current IL based on the energy stored in the inductor 2 flows along the loop of the inductor 2, the base and emitter of the main transistor Q and the diode 3. That is, the current IL flows in the loop shown in FIG. As a result, the main transistor Q is turned on and the load 1 is driven by the driving power source EL.

At this time, the energy stored in the inductor 2 is consumed by the junction resistance between the base and emitter of the main transistor Q and the internal resistance of the diode 3, and the drop rate of the current IL is determined by the combined resistance of these.

Then, to turn off the main transistor Q, the control section 4 outputs an ON signal only to the switching element SW2. Then, the switching element SW2
Turns on and grounds inductor 2. Therefore, the current IL based on the energy stored in the inductor 2 flows along the loop of the switching element SW2, the diode 3 and the inductor 2. That is, the current IL flows in the loop shown in FIG. As a result, no current is supplied to the base of the main transistor, so that the main transistor Q
Turns off and the load 1 stops.

At this time, the base-emitter of the main transistor Q is short-circuited, the internal accumulated charge is extracted, and the main transistor Q is turned off. Further, since energy is consumed only by the internal resistance of the diode 3, the rate of decrease of the current IL becomes gentler than when the main transistor Q is in the ON state.

After that, when energy is consumed and the current value becomes zero by the loop shown in, the control section 4 outputs an ON signal to the switching element SW1. Therefore, the switching element SW1 is turned on, and energy is stored in the inductor 2 again by the power source E1. Then, similarly to the above, the control unit 4 sends the OFF signal to the switching element SW.
1, SW2, both switching elements SW1,
When SW2 is turned off, a current IL based on the energy stored in the inductor 2 flows to the base of the main transistor Q,
The main transistor Q is turned on.

As a result, unlike the prior art, since the resistor R1 is not positively provided, the power loss can be suppressed to be small. The power loss of the driving circuit is compared with the conventional case as follows.

The conventional power loss P1 is expressed by the following equation.

[0022]

[Equation 1]

On the other hand, the waveform of the current IL based on the energy stored in the conductor 2 is shown in FIG.
The power loss P2 is expressed by the following equation based on this waveform.

[0024]

[Equation 2]

Then, in the equation and each term of the equation, E
= 12 [V], d = 0.25, IB = 1 [A], f = 5
Substituting the values of [kHz], L = 100 [μH], and VF = 1 [V] to obtain P1 and P2, P1 = 3 [W],
P2 = 1 [W]. Therefore, under this condition, the power loss is 1/3.

The present invention is not limited to the above-mentioned embodiment. For example, a detector for detecting the current IL is provided,
After the main transistor Q is turned off, the timing of outputting the on signal to the switching element SW1 may be set again based on the detection signal of the detection device. or,
In order to turn on the main transistor Q, the switching element SW1 may be turned off slightly faster instead of turning off both switching elements SW1 and SW2 at the same time. or,
Semiconductor switches such as bipolar transistors and MOS transistors are used as the switching elements SW1 and SW2.

Although the main transistor Q is a bipolar transistor in this embodiment, it is also possible to use a static induction type transistor.

As described in detail above, according to the present invention, there is an excellent effect that power loss can be reduced.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing a drive circuit of a current-driven semiconductor switch according to the present invention.

FIG. 2 is a time chart showing a relationship between ON / OFF of each switching element and a current and a base current flowing through an inductor.

FIG. 3 is a characteristic diagram showing a waveform of a current flowing through an inductor.

FIG. 4 is an electric circuit diagram showing a conventional drive circuit.

[Explanation of symbols]

2 ... Inductor, 3 ... Diode, 4 ... Control part, a, b
... connection point, E1 ... power supply, IL ... current, Q ... main transistor, SW1 ... first switching element, SW2 ... second switching element

Claims (1)

[Claims] 1. An energy storage inductor is connected between a first switching element connected to a power source and a second switching element grounded, and an inductor for energy storage is connected between the first switching element and the inductor. A diode, which is reverse biased and grounded, is connected to the connection point, and a control electrode of a current-driven semiconductor switch whose emitter or drain is grounded is connected to the connection point between the inductor and the second switching element. Turns on the first and second switching elements to store energy in the inductor,
After turning off the first and second switching elements and supplying a current based on the energy stored in the inductor to the control electrode of the current-driven semiconductor switch, the second switching element is turned on to ground the inductor, A drive circuit for a current-driven semiconductor switch, comprising a control unit that outputs a control signal for turning on the first switching element after the current based on the energy stored in the inductor becomes zero.