JPS6412195B2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention relates to a drive circuit that is simply and inexpensively configured to drive the base (gate) of a power transistor that repeatedly opens and closes current to a load. .

[Prior art and its problems]

In the following description of each figure, the same reference numerals indicate the same or corresponding parts.

FIG. 1 shows, as an example, a conventional power transistor drive circuit in a so-called DC chopper circuit. In the figure, 1 is a DC main power supply, 2 is a drive power supply that supplies base current Ib1 to the main transistor 6 as a power transistor, 3 is a resistor that limits the base current Ib1, 4 is a drive transistor,
7 is a load, in this case a motor. Reference numeral 8 denotes a freewheeling diode that absorbs the induced voltage based on the inductance of the motor when the current of the motor is interrupted.

Next, to describe the operation of this circuit, a control signal, as shown in the adjacent waveform, is repeatedly applied to the base of the drive transistor 4 from a control circuit (not shown).
When the drive transistor 4 is repeatedly opened and closed by applying the base current Ib2 as CS, when the drive transistor 4 is ON, the base current Ib1 of the main transistor 6 is applied to the collector of the drive transistor 4.
Short-circuited by the emitter, the main transistor 6
When the driving transistor 4 is OFF, the base current Ib1 is supplied to the main transistor 6, the main transistor 6 is turned ON, and the voltage of the main power supply 1 is applied to the motor 7. By varying the time ratio of on/off of the base current Ib2 in this manner, the average voltage applied from the main power source 1 to the load 7 can be varied and the motor can be controlled.

As in the above example, the drive power supply 2 for driving the main transistor 6 has conventionally been provided independently of the main power supply 1, and the main circuit configuration of a so-called three-phase inverter as shown in FIG. In a circuit that requires such a large number of main transistors 6-1, .

One method for eliminating this drawback is to drive the base of the main transistor using the voltage of the main power supply, and an example of this circuit is shown in FIG. In this circuit, when the drive transistor 4 is OFF, the base current Ib1 of the main transistor 6 is supplied from the main power supply 1 through the resistor 3 to turn the main transistor 6 ON, and when the drive transistor 4 is ON, the base current Ib1 are short-circuited by the collector and emitter of drive transistor 4 to turn off the main transistor. However, as shown in the figure, this circuit has a limitation in circuit configuration, such as the need to place a load on the collector side of the main transistor 6, and has the disadvantage that it cannot be applied to various circuit configurations.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and provide a main transistor drive circuit that utilizes the voltage of the main power supply and is applicable to many types of main circuit configurations. The object of the present invention is to make the drive circuit simple and low-cost, and to enable the drive circuit to be easily built into an individual semiconductor product commonly called a power transistor module.

[Key points of the invention]

The gist of the present invention is to include a main semiconductor element and a drive semiconductor element each having at least a first and a second main terminal and one control terminal, and a first or second main terminal of the main semiconductor element and a control terminal. The first and second main terminals of the drive semiconductor element are connected between the drive semiconductor element and the drive semiconductor element, and the first and second main terminals of the main semiconductor element are connected in series between the DC power source and the load. In a circuit that operates the driving semiconductor element and the main semiconductor element in response to a control signal to a control terminal of a semiconductor element to open and close a current supplied to a load, the voltage is applied to the main semiconductor element when the main semiconductor element is in an OFF state. A capacitor that is charged by the voltage of the DC power source through a series connection of a diode and a first resistor is connected in parallel with the main semiconductor element, and when the main semiconductor element is in an on state, the capacitor is charged by the voltage of the DC power supply. The second resistor for applying the voltage or current of the capacitor to the control terminal is connected to the control terminal of the main semiconductor element and one end of the capacitor.

[Embodiments of the invention]

The present invention will be explained below based on FIGS. 4 to 9. FIG. 4 is a circuit configuration diagram corresponding to FIG. 1 as an embodiment of the present invention. In Figure 4A, the first
The difference from the figure is the base current Ib1 of the main transistor 6.
A capacitor 9, a resistor 10, a Zener diode 11, and a diode 12 are used instead of the drive power supply 2 that supplies
is added. To explain the operation in FIG. 4A in correspondence with the waveforms in FIG. 8, when the base current Ib2 as the control signal CS is applied to the drive transistor 4 and the drive transistor 4 is ON (period T1 in FIG. 8), Base of main transistor 6
The emitter is short-circuited by the drive transistor 4, and the main transistor 6 is OFF.Therefore, the voltage of the main power supply 1 is applied between the collector and emitter of the main transistor 6, and the capacitor 9 is connected to the main power supply 1 → diode 12 → resistor 10 → The capacitor 9 is rapidly charged in the closed circuit of the load 7. Note that a part of the current passing through the resistor 10 is shunted from the resistor 3 to the collector/emitter of the drive transistor 4, and then joins again. At this time, the Zener diode 11 limits the charging voltage ec of the capacitor 9 from becoming excessive, but it can be omitted depending on the circuit conditions.

Next, the inflow of the base current Ib2 is stopped and the drive transistor 4 is turned off (period T2 in Fig. 8).
Then, the base current Ib1 is supplied from the capacitor 9 to the main transistor 6 via the resistor 3, and the main transistor 6 is turned on. At this time, the collector-emitter voltage of the main transistor 6 drops to the collector saturation voltage, but the discharge of the capacitor 9 to the collector-emitter of the main transistor 6 is blocked by the diode 12, and the charging voltage ec of the capacitor 9 gradually drops. do.

Currently, in the application of this type of power transistor, it is common to switch the main transistor 6 on and off at high frequencies, and the resistance 1
Values such as 0, 3 and capacitor 9 can be selected.

In FIG. 4B, a phototransistor 41 in a photocoupler PC is connected in place of the drive transistor 4 in FIG.
This is achieved by switching on and off the forward current IF as the control signal CS flowing through the control signal CS, making it possible to realize an extremely simple circuit that is isolated from the control circuit that outputs the control signal CS.

FIG. 5A shows a circuit configuration as another embodiment of the present invention. The difference from FIG. 4 is that the main transistor 6 is connected to Darlington, and the auxiliary transistor 6 is
This is the point where A is added.

In this circuit, when the main transistor 6 is turned on, by supplying the base current IbA from the capacitor 9 to the auxiliary transistor 6A via the resistor 3,
Base current Ib1 as amplified emitter current
is supplied to the main transistor 6 from the main power supply 1 side via the collector and emitter of the auxiliary transistor 6A. Therefore, since the base current IbA can be made smaller than the base current Ib1 in the case of FIG. 4, it is possible to reduce the capacitance of the capacitor 9 and increase the values of the resistors 10 and 3, that is, to downsize the drive circuit of the main transistor 6. can.

The main difference in FIG. 5B is that a field effect transistor (hereinafter abbreviated as FET) is used instead of a bipolar transistor as the auxiliary transistor 6A, and a phototransistor 41 in the photocoupler PC is used as the drive transistor 4. It is. In this case, there is an extremely high impedance between the gate G1 and the source S1 of the auxiliary transistor 6A, and therefore the values of the resistors 3 and 10 are also smaller than in the case of FIG. 5A.
It is possible to make the value even higher, and the capacitance of the capacitor 9 can be made even smaller. The circuit operation in this case is similar to that shown in Fig. 4B. When the forward current IF is passed through the photodiode PD in the photocoupler PC to turn on the phototransistor 41, the base and emitter of the main transistor 6 are rapidly changed through the speed-up diode SD. Short-circuited and turned OFF. At this time, the gate G1 and source S1 of the auxiliary transistor 6A are also reverse biased, and the drain D1 and source S1 of the auxiliary transistor 6A are turned OFF. Note that the speed up diode SD is connected to the main transistor 6.
The charge at the junction within the phototransistor 41 is rapidly
to turn main transistor 6 from ON to OFF.
It has the role of shortening the switching time to
It may be omitted depending on the circuit conditions. Also
PR is a resistor added between the base and emitter of the phototransistor 41, and has the role of stabilizing the characteristics and breakdown voltage of the phototransistor 41, but can be omitted depending on the circuit conditions.

Next, when the forward current IF is cut off and the phototransistor 41 is turned off, the voltage of the gate G1 with respect to the source S1 of the auxiliary transistor 6A increases, and the voltage between the drain D1 and the source S1 of the auxiliary transistor 6A increases.
During this period, the main transistor 6 is turned on.

6 and 7 also show different embodiments of the present invention, in which the main power source 1 and load 7 are omitted for simplicity. FIG. 6 shows a modified circuit of FIG. 5B, in which FETs are used as the drive transistor 4, the newly added drive auxiliary transistor 4A, and the auxiliary transistor 6A. The operation shown in FIG. 6 is such that when the potential of the gate G2 of the drive transistor 4 with respect to the source S2 is raised to a potential higher than the potential at which the drive transistor 4 can conduct by inputting the control signal CS, the voltage between the drain D2 and the source S2 of the drive transistor 4 is increased.
ON, lowering the potential between the gate G1 and source S1 of the auxiliary transistor 6A, and turning OFF the voltage between the drain D1 and source S1 of the auxiliary transistor 6A, and at the same time receiving the same control signal CS, the drain D3 and source S3 of the drive auxiliary transistor 4A. Pause ON
The base and emitter of the main transistor 6 are then short-circuited. In this circuit, instead of the base and emitter of the transistor 6 being short-circuited by the phototransistor 41 via the speed-up diode SD as shown in FIG. 5B, they are short-circuited by the direct drive auxiliary transistor 4A, which turns off the main transistor The time can be further shortened, and the frequency and withstand voltage of ON/OFF operation, as well as the voltage of the main power supply 1, can be increased. However, the drive auxiliary transistor 4A is the fifth transistor.
Similar to the speed-up diode SD in Figure B, it can be omitted depending on the circuit conditions.

Next, in FIG. 7, the main transistor 6 in FIG. 4B is replaced with an FET, and the positions of the resistor 3 and the phototransistor 41 of the photocoupler PC are exchanged. In this circuit, the forward current IF is applied to the photodiode PD of the photocoupler PC by the control signal CS.
When current flows and the phototransistor 41 turns on, the voltage between the gate GO and the source SO of the main transistor 6 rises, turning on the drain DO and source SO of the main transistor 6. On the other hand, when the forward current IF becomes 0, the phototransistor 41 turns on. OFF, therefore, there is a short-circuit resistor GR between the gate GO and source SO of the main transistor 6.
The drain of the main transistor 6 is short-circuited by
The connection between DO and source SO is OFF. In this case, the relationship between the interruption/continuation of the forward current IF and the ON/OFF of the main transistor 6 is opposite to that shown in FIG. 4B.

Figure 9 shows how the power transistor module TM in Figure 5B is replaced with the power transistor module TM in the main circuit configuration of the three-phase inverter in Figure 2.
An example of application as TM-1, ~, and TM-6 is shown below. In this case, for example, if we look at the power transistor module (hereinafter simply referred to as module) TM-1, initially all modules TM-1 to TM
-6 is OFF, between the collector and emitter of the main transistor 6 in module TM-1,
A voltage is applied in the form of dividing the voltage between the main transistor 6 in the module TM-4 and the main power supply 1, and the capacitor 9 in the module TM-1 is charged. Next, when each module enters ON/OFF operation, a control operation is performed such that when the main transistor 6 of module TM-1 is OFF, the main transistor 6 of module TM-4 is turned ON.
The full voltage of the main power supply 1 is applied to the main transistor 6 of the module TM-1, and the module
The capacitor 9 in TM-1 is charged.

〔Effect of the invention〕

As detailed above, according to the present invention, when the main transistor is in an OFF state, the base of the main transistor is driven using the voltage of the capacitor that is charged by the voltage of the main power supply applied between the collector and emitter of the main transistor. As a result, in application circuits that open and close the main transistor at high speed, the main transistor drive circuit can be extremely simplified, and the drive circuit can be easily built into the main transistor module, and cost reduction can be achieved.

The present invention can be widely applied to transistor modules for so-called power electronics circuits such as transistor inverters and transistor DC choppers.

[Brief explanation of drawings]

Figure 1 is a diagram showing an example of the configuration of a conventional power transistor drive circuit, Figure 2 is a diagram showing an example of the main circuit configuration in which power transistors are often used, and Figure 3 is another configuration of a conventional power transistor drive circuit. 4 to 7 are diagrams showing configuration examples of the power transistor drive circuit of the present invention. FIG. 8 is a diagram showing examples of operating waveforms corresponding to FIGS. 4 and 5. FIG. 9 is a diagram showing an example of the main circuit configuration corresponding to FIG. 2, using the present invention. 1... Main power supply, 3... Resistor, 4... Drive transistor, 6... Main transistor, 6A... Auxiliary transistor, 9... Capacitor, 10... Resistor,
12...Diode, 41...Phototransistor.

Claims (1)

[Scope of Claims] 1. A main semiconductor element and a drive semiconductor element each having at least a first and a second main terminal and one control terminal, the first or second main terminal of the main semiconductor element and The first and second main terminals of the drive semiconductor element are connected between the control terminal and the main semiconductor element, the first and second main terminals of the main semiconductor element are connected in series between a DC power supply and a load, and the In a circuit that operates the drive semiconductor element and the main semiconductor element by a control signal to a control terminal of the drive semiconductor element to open and close the current supplied to the load, when the main semiconductor element is in an OFF state, the main semiconductor element A capacitor that is charged by the applied DC power voltage through a series connection of a diode and a first resistor is connected in parallel with the main semiconductor element, and when the main semiconductor element is in an on state, the main semiconductor element A transistor drive circuit characterized in that a second resistor for applying a voltage or current of the capacitor to a control terminal of the main semiconductor element is connected to a control terminal of the main semiconductor element and one end of the capacitor. 2. The transistor drive circuit according to claim 1, wherein the main semiconductor element comprises one or a plurality of Darlington-connected transistors.