JPH0295195A - Drive circuit for transistor - Google Patents

Abstract

PURPOSE:To simplify circuit constitution, and to miniaturize the whole circuit by directly driving a transistor by a pulse transformer and obtaining the continuous ON state of the transistor. CONSTITUTION:In a circuit driving a transistor 1 insulated from a main power supply, a pulse signal (an ON signal) having a fixed period input to the transistor 1 is insulated by a pulse transformer 31, and the period and duty of the signal are set properly, thus continuously turning the transistor 1 ON. Since there is surely the storage time until the transistor 1 is turned OFF actually after the ON signal is interrupted in the transistor 1, the time when the base input of the transistor 1 is cut off may be brought to the time less than the storage time. Accordingly, a power circuit and a photo-coupler need not be used completely, thus simplifying and miniaturizing the whole circuit.

Description

[Detailed Description of the Invention] [Summary] The present invention is aimed at realizing a transistor drive circuit that is isolated from the main power supply and has a simpler configuration and smaller size than the conventional one. By driving the transistor, a continuous ON state of the transistor is obtained.

[Industrial application field]

The present invention relates to a transistor drive circuit that needs to be insulated from a main power supply, such as a drive circuit for an upper arm transistor when the drive circuit for a DC motor is configured with a bridge circuit made of transistors.

[Conventional technology]

An example of a conventional DC motor drive circuit is shown in FIG.

In the figure, four transistors 1.2.3.4 and four diodes 5.6.7.8 connected between their collectors and emitters are bridge-connected to a DC motor 9. . The main power supply 10 is connected between the collector of the upper arm transistor 1.2 and the emitter of the lower arm transistor 3.4, and the emitter side of the lower arm transistor 3.4 is connected to the entire circuit. This is the ground (GND).

Further, for the upper arm transistor 1, an upper arm drive circuit 14 is provided which includes transistors 11 and 12 for turning on and turning off the transistor 1, a photocoupler 13 for switching these, and the like. Furthermore, in order to supply power to this drive circuit 14, the main power supply 1
A flyback type power supply circuit 15 insulated from zero is provided. This power supply circuit 15 has a series circuit consisting of a primary coil 17a of a transformer 17 and a transistor 18 connected in parallel to a DC power supply 16, and a secondary coil 17
A smoothing circuit consisting of a diode 19 and a capacitor 20 is connected in parallel to b.

Note that the power supply circuit 15 may be of another type, such as a forward type, instead of the flyback type described above.

The other upper arm transistor 2 is also provided with a drive circuit and a power supply circuit similar to those described above, but they are omitted here.

On the other hand, for the lower arm transistor 3, a lower arm drive circuit 21 having the same configuration as the upper arm drive circuit 14 except for the photocoupler 13 is provided. A similar drive circuit is also provided for the other lower arm transistor 4, but it is omitted here.

In the above configuration, in order to rotate the motor 9 in both forward and reverse directions, the four transistors 1.2.3.4 are connected to the motor 9 by giving a predetermined drive signal from the controller 22 to each drive circuit 14.21. On the other hand, turn it on and off in a lotus shape. That is, upper arm transistor 1.
With one of 2 turned on and the other turned off,
The motor 9 is rotated by chopping one of the lower arm transistors 3.4, which are diagonally positioned across the motor 9, from the on-state transistor.

[Problem to be solved by the invention]

In the circuit shown in FIG. 4, the GND of the lower arm drive circuit 21 is grounded to the GND of the entire circuit, while the GND potential of the upper arm drive circuit 14 is connected to the lower arm transistor 3. 4 and the operating state of the motor 9.

That is, for example, when the transistor 3 for the lower arm is in the on state, the GND on the upper arm side is short-circuited with the GND on the lower arm side, but on the other hand, when the transistor 3 for the lower arm is in the off state, current flows through the motor 9. , ``Along with this, the GND potential on the upper arm side fluctuates. Furthermore, when both lower arm transistors 3 and 4 are in the off state,
No current flows at all. For these reasons, the drive circuit 14 for the upper arm is different from the drive circuit 21 for the lower arm,
Completely different from the main power supply 10, that is, the main power supply 10
The power supply circuit 15 is required to be insulated from the power source.

Moreover, the GND of the drive signal from the controller 22
is equal to the GND of the entire circuit, and for the same reason as above, the upper arm drive circuit 14 requires a photocoupler 13 made of a combination of a light emitting diode and a phototransistor, for example.

In this way, in order to drive the upper arm transistor 1, a power supply circuit 15 isolated from the main power supply 10,
Since a drive circuit 14 with a complicated configuration including a photocoupler 13 is required, there is a problem that the entire circuit becomes complicated and large.

The present invention has been made in view of the above conventional problems, and an object of the present invention is to provide a transistor drive circuit that can be simplified in structure and miniaturized.

[Means to solve the problem]

(1) A pulse transformer is used in a transistor drive circuit that is insulated from the main power source, and the transistor is continuously turned on by a constant periodic pulse signal output from the pulse transformer.

(2) In the configuration of (1) above, the off time of the pulse signal output from the pulse transformer is set to be less than the storage time (t st9 ) of the transistor.

[For production]

A pulse signal (on signal) with a constant period inputted to the transistor is insulated by a pulse transformer, and the transistor can be turned on continuously by appropriately setting the period and duty. For example, since a transistor always has an accumulation time j st9 from when the on signal is turned off until it actually turns off, in order to turn the transistor on continuously with a pulse signal, the time during which the base input is turned off is the accumulation time f, It is sufficient to make it less than St9.

By using a pulse transformer in the transistor drive circuit and making it possible to turn on the transistor continuously, there is no need to use a conventional power supply circuit or photocoupler, thereby simplifying and downsizing the entire circuit. Realized.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a circuit diagram showing the overall configuration of a DC morph drive circuit to which an embodiment of the transistor drive circuit of the present invention is applied.

In the figure, similar to the conventional circuit shown in Figure 4,
four transistors 1.2.3.4 and their collectors;
4 diodes each connected between emitters5.
6.7.8 is bridge connected to the DC motor 9. The main power supply 10 is connected between the collector of the upper arm transistor 1.2 and the emitter of the lower arm transistor 3.4, and the emitter side of the lower arm transistor 3.4 is connected to the GN of the entire circuit.
It is D.

Furthermore, the drive circuit 30 of this embodiment is provided to drive the upper arm transistor l.

The drive circuit 30 has a pulse transformer 31 for turning on the upper arm transistor, and a transistor 33 is connected in series to a parallel circuit consisting of a primary coil 31a and a diode 32. DC power supplies 34 are connected in parallel. The secondary coil 31b of the pulse transformer 31 includes a diode 35 and a resistor 3.
The upper arm transistor 1 is connected in parallel between the base and emitter of the transistor 1 via the transistor 6 .

Further, a transistor 37 is connected between the base of the upper arm transistor 1 and the emitter for turning off the transistor 1, and another one for driving the transistor 37.
Two pulse transformers 38 are provided. A transistor 40 is connected in series to a parallel circuit consisting of a primary coil 38a and a diode 39 of this pulse transformer 38, and a DC power source 34 is connected in parallel to the series circuit. and is connected in parallel between the base and emitter of the OFF transistor 37 via a resistor 42. Note that a drive circuit similar to the drive circuit 30 is also provided for the other upper arm transistor 2, but is omitted here.

On the other hand, for the lower arm transistor 3, a drive circuit 21 having a configuration similar to that shown in FIG. 4 is provided. A similar drive circuit is also provided for the other lower arm transistor 4, but it is omitted here. Further, a controller 43 is provided for controlling the drive circuits 30.21 for the upper arm and the lower arm.

Next, the operation of the circuit having the above configuration will be explained.

In the above circuit, in order to rotate the motor 9 in both forward and reverse directions as in the conventional case, by applying a predetermined drive signal from the controller 43 to each drive circuit 30.21,
The four transistors 1.2.3.4 are turned on and off in a helical pattern with respect to the motor 9. That is, when one of the upper arm transistors l and 2 is turned on and the other is turned off, the transistor in the on state is the motor 9.
Transistor 3.4 for the lower arm located diagonally across the
By chopping on one side, the motor 9 is rotated.

At that time, a method for driving the upper arm transistor 1 by the driving circuit 30 of this embodiment will be specifically explained based on FIG. 2.

First, by inputting a pulse-like drive signal of 111 periods as shown in FIG. 2(a) to the transistor 33, an ON signal (
2(C)) is applied to the upper arm transistor 1. Since this on signal is insulated by the pulse transformer 31, the upper arm transistor 1 can be turned on continuously by appropriately setting the cycle and duty of this on signal.

For example, considering that a transistor always has an accumulation time L st9 from when the on signal is turned off until it actually turns off, in order to turn on transistor 1 continuously without continuous base input, the base power must be cut off. It may be set so that the time (indicated by Ll in FIG. 2(C)) is shorter than the accumulation time t□9, that is, t I < t st9. Furthermore, if the drive frequency of the transistor 33 is determined so that the time t during which the base power is cut off is less than 50% duty, the upper arm transistor 1 can be continuously turned on by inputting a duty of 50% (MAX). becomes possible.

On the other hand, by inputting a pulse-like drive signal with a constant period as shown in FIG. is turned on.

Then, during the on period, the heath and emitter of the upper arm transistor 1 are short-circuited (the second
(C)), the upper arm transistor 1 is turned off.

As described above, in the drive circuit 30 of this embodiment, the upper arm transistor 1 can be turned on and off by using the pulse transformers 31, 38, etc., so that the main power supply as shown in FIG. The power supply circuit 15 insulated from the power supply circuit 10 and the drive circuit 14 equipped with the photocoupler 13 can be almost replaced with the pulse transformer 31, 38, etc., thereby significantly reducing the number of circuit components and realizing miniaturization of the entire circuit. be able to. Furthermore, instead of turning on the upper arm transistor 1 manually on a continuous basis,
Since it is turned on by intermittent base input according to the pulse signal, it also leads to energy savings.

Note that the circuit consisting of the transistor 37, pulse transformer 38, transistor 40, etc. is for turning off the upper arm transistor 1, so if you do not particularly care about the off time, these circuits may not be used. may be omitted. In this way, the entire circuit can be further simplified and miniaturized.

Next, FIG. 3 is a circuit diagram showing the overall configuration of a DC motor drive circuit to which another embodiment of the transistor drive circuit of the present invention is applied.

In the figure, the drive circuit 50 of this embodiment is the same as the drive circuit 30 shown in FIG. 1, with the addition of a circuit 51 (shown surrounded by a broken line) for creating a negative power supply for off, and other configurations. is the same as the circuit shown in FIG. The above circuit 51
Here, a transistor 54 is connected in series to a parallel circuit consisting of the primary coil 52a of the pulse transformer 52 and a diode 53, and a DC power supply 34 is connected in parallel to the series circuit. 52b is connected in parallel to a capacitor 56 connected to the collector side of the OFF transistor 37 via a diode 55.

In the above configuration, by driving the transistor 54 at the same time as the transistor 40, the capacitor 56 can function as a negative power supply for turning off while the transistor 37 for turning off is on. This results in
Since a constant current can be drawn at all times when the upper arm transistor 1 is turned off, the turn-off time is shorter than in the embodiment described above, and high-speed off is therefore possible.

In addition, in FIG. 3 above, two pulse transformers 38
．． Instead of providing the 52 primary coils 38a, 52a separately, they may be shared by one coil.

Furthermore, although each of the above-described embodiments has been described as a drive circuit for an upper arm transistor, the present invention is not limited thereto, and is applicable to various transistor drive circuits that are insulated from a main power source. For example, a drive circuit that can be turned on and off at high speed as shown in FIG. 3 can be easily applied to power supply circuits such as inverters.

〔Effect of the invention〕

As explained above, according to the present invention, by using a pulse transformer to enable continuous ON of a transistor, there is no need to use a conventional power supply circuit isolated from the main power supply, a photocoupler, etc. Therefore, the circuit configuration can be simplified and the entire circuit can be miniaturized.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the overall configuration of a DC motor drive circuit to which an embodiment of the transistor drive circuit of the present invention is applied, and FIGS. 2(a) to (C) are main signal waveforms of the circuit in FIG. 1. 3 is a circuit diagram showing the overall configuration of a DC motor drive circuit to which another embodiment of the transistor drive circuit of the present invention is applied. FIG. 4 is a circuit diagram showing the overall configuration of a conventional DC motor drive circuit. It is a diagram. ■, 2... Transistor for upper arm, 30... Drive circuit for upper arm, 31... Pulse transformer,

Claims (1)

[Claims] 1) In a drive circuit for the transistor (1) that is insulated from the main power supply (10), the transistor (1) is continuously turned on by a pulse signal of a constant period output from a pulse transformer (31). A transistor drive circuit characterized in that: 2) The transistor drive circuit according to claim 1, wherein the off-time of the pulse signal output from the pulse transformer (31) is set to be less than the storage time of the transistor (1).