JPH05268034A - Drive circuit for current drive type semiconductor switch - Google Patents

Abstract

PURPOSE:To drive the current drive type semiconductor switch by the drive circuit employing a single power supply by reducing the power loss of the drive circuit for the current drive type semiconductor switch at switching. CONSTITUTION:Induction coils 2, 3 are connected in series between a switching element SW1 connecting to a power supply E1 and a switching element SW2 connecting to ground. A diode 5 reverse-biased is connected between the switching element SW1 and the induction coil 2. A gate of a source ground main transistor(TR) Q is connected between the induction coils 2, 3 via a switching element SW3. Moreover, the switching elements SW1, 2 are turned on to store energy in the induction coils 2, 3, the switching element SW3 is turned on after the switching element SW1 is turned off, and the switching element SW2 is turned off to supply a supply current IG to the gate of the main TR Q based on the energy stored in the induction coils 2, 3 and the switching element SW2 is turned on to supply an extract current -IG to the gate of the main TR Q through the operation of a control section 6.

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. Then, 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 driving power source EL via the load 32.
The base of the switching transistor 31 is a resistor R
1 and the first switching element 33 to be connected to the positive electrode of the power source E1, and the resistor R2 and the second switching element 34.
It is connected to the negative electrode of the power source E2 via. Then, ON / OFF control of both switching elements 33 and 34 is performed by a control signal from a driver (not shown), and when the first switching element 33 is turned on and the second switching element 34 is turned off, switching is performed from the power source E1. The base current (transfer current) IB is supplied to the base of the switching transistor 31, and the switching transistor 31 is turned on. In addition, the first switching element 33 is turned off and the second switching element 33 is turned off.
When the switching element 34 is turned on, the reverse base current (extraction current) -IB is supplied from the power source E2 to the base of the switching transistor 31, and the switching transistor 31 is turned off.

[0003]

However, the conventional drive circuit has a problem that the power loss due to the current flowing through the resistors R1 and R2 is large when the switching transistor 31 is turned on and off.

Further, in order to shorten the extraction time when the switching transistor 31 is turned off, a negative power source for supplying an extraction current to the base of the switching transistor 31 is required, and two positive and negative power sources are used as driving power sources. There is a problem that E1 and E2 are required.

The present invention has been made to solve the above problems, and an object thereof is to reduce the power loss at the time of switching and to drive a current drive type semiconductor switch which can be driven by a single power supply drive. To provide.

[0006]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides first and second induction devices between a first switching element connected to a power source and a second switching element grounded. A coil is connected in series, a diode that is reverse-biased and grounded is connected between the first switching element and the first induction coil, and the first induction coil and the second induction coil are connected. A gate or a base of a current-driven semiconductor switch whose source is grounded or whose emitter is grounded is connected through a third switching element, and the first and second switching elements are turned on to connect the first and second switching elements.
Energy is stored in the second induction coil, the first switching element is turned off, the third switching element is turned on, the second switching element is turned off, and the energy is stored in the first and second induction coils. Control for supplying the transfer current to the gate or the base of the current drive type semiconductor switch based on the energy, and then turning on the second switching element to supply the extraction current to the gate or the base of the current drive type semiconductor switch. The idea is to have a section.

[0007]

When the controller turns on the first and second switching elements, energy is stored in the first and second induction coils connected in series by the power source. Then, when the control unit turns off the first switching element, the current due to the energy accumulated in the first and second induction coils connected in series becomes a loop-shaped inertia current flowing through the second switching element and the diode. Become. After that, when the control unit turns on the third switching element and turns off the second switching element, the inertia current is supplied as a transfer current to the gate or the base of the current-driven semiconductor switch through the third switching element. Then, the current-driven semiconductor switch is turned on.

After that, when the control unit turns on the second switching element, the gate or base of the current-driven semiconductor switch is in the opposite direction to the above based on the energy stored in the second induction coil. The extraction current is supplied, and the current-driven semiconductor switch is turned off.

[0009]

EXAMPLES The present invention will be described below with reference to an electrostatic induction type transistor (S
An embodiment embodied in an IT (Static Induction Transistor) will be described with reference to FIGS.

As shown in FIG. 1, the main transistor Q, which is an electrostatic induction type transistor, has its source grounded, and its drain via a load 1 such as a motor.
Connected to L. The power source E1 has a first switching element SW1 composed of a P-type MOS transistor.
One end of the first induction coil 2 is connected via.
The other end of the induction coil 2 is connected to one end of a second induction coil 3, and the other end of the induction coil 3 is grounded via a second switching element SW2 composed of an N-type MOS transistor. .. The induction coils 2 and 3 have the same number of turns in this embodiment.

Therefore, the induction coils 2 and 3 are connected in series, and the induction coils 2 and 3 are wound around the iron core 4 in order to reduce mutual leakage inductance. Further, the switching elements SW1, SW
2 is turned on, and the induction coil 2,
The induction coils 2 and 3 are wound around the iron core 4 so that the point P is the N pole when the current flows to the coil 3.

A reverse-biased diode 5 is connected to the connection point a between the switching element SW1 and the induction coil 2 in a grounded state. Further, the gate of the main transistor Q is connected to the connection point b between the induction coils 2 and 3 via a third switching element SW3 composed of an N-type MOS transistor.

Each of the switching elements SW1 to SW3 is connected to a control section 6, which controls each switching element S.
An on / off control signal is output to W1 to SW3. That is, the control unit 6 controls each switching element SW.
After outputting an ON signal to SW1 and SW2, an OFF signal is output to the switching element SW1. Then, the control unit 6 outputs an ON signal to the switching element SW3 and then outputs an OFF signal to the switching element SW2. Further, after the ON signal is output to the switching element SW2 again, the OFF signal is output to the switching element SW3.

Next, the operation of the drive circuit configured as described above will be described with reference to FIGS. 3 shows a circuit in which each of the switching elements SW1 to SW3 is replaced with a switch, and FIGS. 2 and 4 show timing charts of the driving circuit. In FIG.
The ON voltage of SW3 is ignored.

When the switching element SW2 is turned on based on the ON signal of the control section 6 and the switching elements SW1 and SW3 are turned off based on the OFF signal of the control section 6, the main transistor Q is turned on. Since the gate current (transfer current) IG is not supplied to the gate, the main transistor Q is in the off state.

In this state, when the switching element SW1 is turned on based on the ON signal of the control section 6, a current ISW1 flows through the switching element SW1. Therefore, the currents IL1 and IL2 flow while increasing in the induction coils 2 and 3 connected in series by the power source E1, and the currents IL1 and IL2
L2 goes through the route shown in. Energy is stored in the induction coils 2 and 3 by the currents IL1 and IL2. At this time, the potential V1 at the connection point a becomes the same potential E as the power source E1, and the potential at the connection point b becomes E / 2 because it is half the total number of turns of the induction coils 2 and 3. Further, since the induction coils 2 and 3 have the same number of turns, the currents IL1 and IL2 are equal to each other.

After that, when the switching element SW1 is turned off based on the OFF signal of the control section 6, the current ISW1 flowing through the switching element SW1 is cut off. Therefore, the currents IL1 and IL2 flow as a loop current passing through the path shown in FIG. In addition, the current IDi flows through the diode 5. The currents IL1, IL2, and IDi are the diode 5
It gradually decreases due to the internal resistance of. At this time, at the connection point a, the voltage -VF corresponding to the voltage drop VF of the diode 5 is generated.
Occurs. Furthermore, since the number of turns of the induction coils 2 and 3 is half the total number of turns at the connection point b, a voltage -VF / 2 is generated.

Then, when the switching element SW3 is turned on based on the ON signal of the control section 6 and the switching element SW2 is turned off based on the OFF signal of the control section 6, the current IL1 causes the induction coils 2, 3 to flow. Since the number of turns is the same, a doubled current value is supplied to the gate of the main transistor Q as the gate current (transfer current) IG via the switching element SW3. At this time, since the switching element SW2 is turned off, the current IL2
Is zero.

Therefore, the main transistor Q is turned on. The transfer current IG flows as a current passing through the source of the main transistor Q, the diode 5, the induction coil 2 and the switching element SW3, that is, a loop current passing through the path shown in FIG. At this time, the current IDi flowing through the diode 5 also doubles. And the main transistor Q
Is on, the potential V2 at the connection point b is the voltage VGS applied between the gate and source of the main transistor Q.
Becomes The potential V1 at the connection point a is (induction coils 2, 3
Therefore, the voltage becomes 2VGS because it is twice the potential V2.

In this state, when the switching element SW2 is turned on based on the ON signal of the control section 6,
Switching element SW3, the gate of the main transistor Q,
The path of the source, the switching element SW2 and the induction coil 3, that is, the path shown in FIG. 3 is formed. At this time,
Currents IL1 and IDi flowing through the induction coil 2 and the diode 5
Is zero.

Then, the current IL2 based on the energy accumulated in the induction coil 3 flows in the path indicated by. At this time, since the turns ratios of the induction coils 2 and 3 are the same and the switching element SW2 side of the induction coil 3 is the N pole, a double extraction current -IG in the opposite direction to the transfer current IG flows. become. And the main transistor Q
Since the charge accumulated in the gate of is extracted,
The main transistor Q is turned off.

When the main transistor Q is turned off, the loop shown in FIG. 3 is formed, and currents IL1, IL2 and IDi flow through the induction coils 2 and 3 and the diode 5. After the main transistor Q is turned off, the swing element SW
In order to prepare for turning on 1, the switching element SW3 is turned off based on the off signal of the control unit 6.

After that, when the switching element SW1 is turned on again by the ON signal of the control section 6, the drive circuit performs the same operation as described above. As a result, unlike the prior art, since the resistors R1 and R2 are not positively provided, the power loss at the time of switching can be suppressed small and the heat generation can be reduced. Further, the drive circuit can be driven by a single power source drive.

In this embodiment, the static induction type transistor is used as the current driving type semiconductor switch, but it is also possible to use a bipolar transistor in addition to this.

Further, in the present embodiment, the switching elements SW1 to SW3 are composed of MOS transistors, but it is also possible to use bipolar transistors or the like.

Further, although the number of turns of the induction coils 2 and 3 is the same, the number of turns can be changed if necessary.

[0027]

As described in detail above, according to the present invention, the power loss at the time of switching can be reduced and the device can be driven by a single power source drive. is there.

[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 timing chart showing the operation of the drive circuit.

FIG. 3 is an explanatory diagram showing paths of currents flowing when the switching elements are on / off controlled.

FIG. 4 is a timing chart showing the operation of the drive circuit.

FIG. 5 is an electric circuit diagram showing a conventional drive circuit.

[Explanation of symbols]

2, 3 ... Induction coil, 5 ... Diode, 6 ... Control unit, E
1 ... Power supply, IG ... Transfer current, -IG ... Extraction current, S
W1 to SW3 ... Switching element, Q ... Main transistor as current-driven semiconductor switch

Claims (1)

[Claims] 1. A first and a second induction coil are connected in series between a first switching element connected to a power source and a second switching element grounded, and the first switching element and the second switching element are connected in series. A diode that is reverse-biased and grounded is connected between the first induction coil and the first induction coil, and a source is grounded between the first induction coil and the second induction coil through a third switching element. The gate or base of a current-driven semiconductor switch whose emitter is grounded is connected, and further, the first and second switching elements are turned on to store energy in the first and second induction coils, and the first switching element Is turned off and then the third switching element is turned on, the second switching element is turned off, and the current-driven semiconductor is conducted based on the energy stored in the first and second induction coils. After supplying a transfer current to the gate or base of the body switch, a current drive type semiconductor provided with a control unit for turning on the second switching element to supply the extraction current to the gate or base of the current drive type semiconductor switch Switch drive circuit.