JPH11178320A - Power transistor drive - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To be used for a PWM (Pulse Width Modulation) system,
In the power transistor driving device, since the base current at the time of on, which is output to the power transistor, is always the maximum value required by the power transistor, there is a problem that a large amount of heat is generated, and dimensions and mass are large. SOLUTION: A base current corresponding to a collector current of a power transistor is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a power transistor driving device, and more particularly, to a driving device for functioning a power transistor for driving a load such as a motor.

[0002]

2. Description of the Related Art FIG. 5 is a diagram for explaining an application example of a conventional power transistor driving device.
Is a driving device for causing a plurality of power transistors 3a to 3d to drive the power transistors to function. This device uses an external power supply 4
Power supply circuit 5 for receiving electric power from outside, and external current command 6
And a current loop control circuit 7 receiving the
M (pulse-width-modulation)
A PWM conversion circuit 8 for converting the PWM signal into a signal and first to first on / off control of 3a to 3d by power-amplifying the PWM signal;
Fourth base drive circuits 9a to 9d and load device 2
And a current detection circuit 10 for detecting a current flowing through the control circuit 7 and outputting the detected current to the control circuit 7. The output of the power supply circuit 5 has four systems, and 11, 12, 13, and 14 each have 9 outputs.
a, 9b, 9c and 9d. Reference numeral 15 denotes a DC power supply that supplies power to the load device 2, and reference numeral 16 denotes a resistor that converts a current flowing through the load device 2 into a voltage.
7a to 17d are called fly-hole diodes, and P
A diode for continuing the current flowing to the load device 2 when 3a to 3d are turned off by the WM signal and the power supply from the DC power supply 15 is stopped. As described above, the current corresponding to the current command 6 is supplied to the load device 2. FIG. 6 shows the relationship between the switching of the power transistors 3a to 3d and the current flowing through the load device. In this case, the load device 2 in FIG. 5 shows a time when a current flows from left to right.

[0003] Here, the prior art will be described. FIG.
5 shows a portion for driving the power transistor 3a in FIG. The base drive circuit 19 in FIG. 7 is of a constant current control type in which a base current supplied when the power transistor 3a is turned on has a base current value required for a maximum collector current flowing through the transistor. The power supply circuit 20 that supplies DC power to the circuit 19 has a constant voltage output so that the circuit 19 can stably perform a constant current control operation.

[0004]

In the conventional power transistor driving device as described above, the output current when the base drive circuit is turned on is always the maximum base current required by the power transistor. Therefore, there is a problem that the power consumption of the power transistor driving device, that is, the calorific value increases, and the size and the mass increase.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and it is an object of the present invention to provide a power transistor drive device in which the amount of heat generated by a base drive circuit and a power supply circuit is reduced and the size is reduced.

[0006]

According to a first aspect of the present invention, there is provided a power transistor driving device which changes a system of a base drive and a power supply circuit and changes a value of a base current supplied to the power transistor according to a magnitude of a current command value. Let it.

Further, the power transistor driving device according to the second invention changes the method of the base drive and the power supply circuit to change the value of the base current supplied to the power transistor at the same time as changing the value of the current command value. The power supply for the base drive to the unnecessary power transistor is turned off depending on the polarity of the current command.

In the power transistor driving apparatus according to the third aspect of the present invention, the system of the base drive and the power supply circuit is changed, and the value of the base current supplied to the power transistor is changed according to the magnitude of the current flowing through the power transistor. .

The power transistor driving device according to a fourth aspect of the present invention changes the system of the base drive and the power supply circuit, and changes the value of the base current supplied to the power transistor according to the magnitude of the current flowing through the power transistor. At the same time, the power for unnecessary base drive to the power transistor is turned off depending on the polarity of the power transistor current.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a block diagram showing Embodiment 1 of the present invention.
Is a power transistor driving device according to the present invention,
Reference numeral 22 denotes a non-current control type base drive circuit that switches in accordance with the timing of a PWM signal. Reference numeral 23 denotes a power supply circuit that varies an output voltage using a current command as a reference. This is the same as FIG. According to this, since the base current value is varied by the load device, that is, the current flowing through the collector of the power transistor, the power consumption in this device becomes smaller than that in the conventional technology, and the size can be reduced. . In other words, in an extreme case, when the current flowing through the load device is almost zero, the same base current flows as when the current is maximum in the conventional technology. That is, the output current of this device is also substantially zero.

Embodiment 2 FIG. 2 is a block diagram showing a second embodiment of the present invention. In FIG. 2, reference numeral 24 denotes a power transistor driving device according to the present invention. Is a power supply circuit that can be turned on and off, and 26 is a circuit that determines the polarity of the current command.
Is a circuit for turning on and off 25 in response to a signal from 26, and the other components are the same as those in FIG. According to this, the base current is varied as in the first embodiment, and the base current is set to 0 according to the polarity of the current command. For example, when a current flows through the load device as shown in FIG. 6, the base drive circuit 3 shown in FIG.
The outputs of B and 3C become 0.

Embodiment 3 FIG. 3 is a block diagram showing a third embodiment of the present invention. In FIG. 3, reference numeral 28 denotes a power transistor driving device according to the present invention, and the components provided with other reference numerals are the same as those in FIG. According to this, the base current is varied as in the first embodiment, with the reference of the power supply circuit as the current flowing through the load device.

Embodiment 4 FIG. 4 is a block diagram showing a fourth embodiment of the present invention. In FIG. 4, reference numeral 29 denotes a power transistor driving device according to the present invention, and the other components denoted by the same reference numerals are the same as those in FIG. According to this, the base current is varied as in the second embodiment, and the base current is set to 0 according to the polarity of the current command.

[0014]

According to the first aspect, it is possible to reduce the size of the power transistor driving device.

Further, according to the second aspect, the power transistor driving device can be reduced in size more than the scale of the first aspect.

According to the third aspect of the present invention, although the method is different, the power transistor driving device can be downsized with the same scale as the first aspect of the invention.

According to the fourth aspect of the invention, although the system is different, the power transistor driving device can be downsized with the same scale as the second aspect of the invention.

[Brief description of the drawings]

FIG. 1 is a diagram showing Embodiment 1 of a power transistor driving device according to the present invention.

FIG. 2 is a diagram showing a power transistor driving device according to a second embodiment of the present invention;

FIG. 3 is a diagram showing a power transistor driving device according to a third embodiment of the present invention;

FIG. 4 is a diagram showing a fourth embodiment of the power transistor driving device according to the present invention;

FIG. 5 is a diagram showing an application example of the power transistor driving device.

6 is a diagram showing a relationship between switching of a power transistor and a current flowing through a load device in the application example of FIG. 5;

FIG. 7 is a diagram showing a conventional power transistor driving device.

[Explanation of symbols]

1 power transistor drive device, 2 load device, 3
Power transistor, 4 external power supply, 5 power supply circuit, 6
Current command, 7 current loop control circuit, 8 PWM conversion circuit, 9 base drive circuit, 10 current detection circuit, 11 power supply, 12 power supply, 13 power supply, 14 power supply, 15 DC power supply, 16 resistor, 17 diode,
18 power transistor device, 19 constant current control type base drive circuit, 20 constant voltage output power supply circuit, 21
Power transistor device, 22 non-current control type base
Drive circuit, 23 variable output voltage power supply circuit, 24 power transistor drive device, 25 variable output voltage power supply circuit, 26 polarity discrimination circuit, 27 power on / off control circuit.

Claims (4)

[Claims] 1. A power transistor driving device for operating a plurality of power transistors connected in a bridge shape for controlling a load of a motor or the like, wherein a non-current control type base drive circuit for operating the power transistor; A power transistor driving device, comprising: a power supply source that functions as a base drive circuit; and a power supply circuit that changes a supply voltage according to a current command externally applied to the load. 2. A power transistor driving device for operating a plurality of power transistors connected in a bridge shape for controlling a load of a motor or the like, wherein a non-current control type base drive circuit for operating the power transistor; A power source that functions as a base drive circuit, and whose supply voltage changes in response to an externally supplied current command to the load and that can be turned on and off in accordance with the polarity of the current command A power transistor driving device comprising a circuit. 3. A power transistor driving device for operating a plurality of power transistors connected in a bridge shape for controlling a load of a motor or the like, wherein said non-current control type base drive circuit for operating said power transistor; A power supply source for operating a base drive circuit, and a power supply circuit whose supply voltage changes according to a current flowing through the load. 4. A power transistor driving device for operating a plurality of power transistors connected in a bridge shape for controlling a load of a motor or the like, wherein a non-current control type base drive circuit for operating the power transistor; A power supply source for operating the base drive circuit, wherein a supply voltage changes according to a current flowing through the load, and can be turned on and off according to the polarity of the current flowing through the load. A power transistor driving device, comprising: