JPH08149853A - Current detector of power module - Google Patents

Abstract

PURPOSE: To provide an inexpensive and reliable current detector by providing a transistor bridge power module with a terminal which outputs the current value of a power transistor in analog. CONSTITUTION: A transistor bridge for driving an AC motor is composed of a diode and an IGBT2 fitted with a sense terminal. To the sense terminal 12 of each IGBT 12 is a sense resistor 5 connected, and the voltage 9 proportionate to the current flowing to the collector terminal is outputted to the end of the sense resistor 5. This voltage 9 is outputted to the terminal, being amplified with the inner amplifier 6 of a drive protective circuit 4. The voltage of this terminal is outputted to the terminal 9 through a high-linearity analog photocoupler 21. Dispersion exists in the current ratio of the current flowing to the sense terminal 12 to the current flowing to the collector terminal 11, so the ratio of the current values of the collector to the voltage value of the terminal 19 is adjusted with a resistor 20 so that it may be the same in each device. And, the control becomes possible by performing the comparison with a current command by this value, and amplifying the error, and issuing a voltage command.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power module for driving an AC motor by an inverter, and more particularly to a current detection device for a power module capable of detecting a transistor current value.

[0002]

2. Description of the Related Art Generally, in an AC servo driver, it is necessary to monitor each phase current and adjust it. By the way, conventionally, in order to servo-control the AC motor 1 as shown in FIG. 4, the power amplifier unit 15 is driven by the voltage command 17,
The AC motor 1 rotates. At this time, AC motor 1
Of each phase, that is, u-phase, v-phase, and w-phase current values are detected by the current sensor 14 such as a Hall element, the current values are fed back, compared with the current command 18, and the error is amplified by the amplifier. , Becomes a voltage command. Here, the power amplifier unit 15 is composed of a transistor bridge 16 as shown in the figure.

[0003]

By the way, in AC servo control, a current sensor is indispensable, and there is a drawback that this sensor component is expensive in the system and the set price is high.

An object of the present invention is to solve the drawbacks that the conventional current sensor is expensive and the servo driver of the AC servo control device is expensive, and to provide an inexpensive and highly reliable current detection device.

[0005]

In order to achieve the above object, the present invention comprises a power transistor for driving an AC motor by an inverter, a diode, a drive circuit for the power transistor, and a circuit having a current detection function for the power transistor. In the transistor bridge module, the current detection device of the power module is provided with a terminal that outputs the current value of the power transistor in analog.

[0006]

In the above structure, a voltage proportional to the collector current of the power transistor is taken out, this voltage is amplified by the amplifier circuit of the drive control circuit of the power transistor, and is analog-outputted to the outside of the module. The current detection device connected to v and w becomes unnecessary.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A current detecting device for a power module according to an embodiment of the present invention will be described below.

As shown in the block diagram of FIG. 1, the AC motor 1
Is driven by an inverter, that is, driven by AC voltages of u, v and w phases of a transistor bridge. In the transistor bridge, the diode 3 and the IGBT 2 with the sense terminal are composed of 6 devices each. Each I
As shown in FIGS. 2 and 3, the GBT 2 has collector terminals 11,
There are four terminals, an emitter terminal 13, a gate terminal 10 and a sense terminal 12. The sense resistor 5 is connected to the sense terminal 12, and a voltage 9 proportional to the current flowing through the collector terminal is output to the end of the sense resistor 5. This voltage 9 is amplified by the internal amplifier 6 of the drive protection circuit 4 and output to the terminal 8. The voltage at the terminal 8 is output to the terminal 19 via the high linearity analog photocoupler 21. There is variation in the ratio of the current flowing through the sense terminal 12 and the current flowing through the collector terminal 11, and the resistor 20 is adjusted so that the ratio of the collector current value and the voltage at the terminal 19 is the same in each device. Accordingly, the current of each phase is equal to the terminal voltage 19 of each phase of the transistor bridge 16, the upper arm, and the lower arm.
By adding, the analog value of (+) (-) is obtained.

With this value, similarly to the current sensor in the prior art, control can be performed by comparing with the current command, amplifying the error, and issuing the voltage command. In addition to the IGBT, the power transistor is a transistor,
It may be a MOSFET. Further, the analog output terminal is insulated via a photocoupler and serves as a common ground terminal for each device in the transistor bridge.

[0010]

In the prior art, since each phase current is monitored by the AC servo driver, three or two current sensors are required, which is expensive, but in the present invention, the power module is provided with a current detection terminal. Therefore, the current sensor is not necessary, and the current detection function can be added at a small cost, and an inexpensive and highly reliable AC servo system can be constructed.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a servo system using a current detection device of the present invention.

FIG. 2 is a block diagram showing an embodiment of the periphery of a power device in the current detection device of the present invention.

FIG. 3 is a block diagram of a main part of a current detection device of the present invention.

FIG. 4 is a block diagram of a conventional servo driver.

[Explanation of symbols]

 1 AC motor 2 IGBT with sense terminal 3 Diode 4 Drive protection circuit 5 Sense resistor 6 Internal amplifier 8 Terminal 9 Voltage proportional to current flowing in collector terminal 10 Gate terminal 11 Collector terminal 12 Sense terminal 13 Emitter terminal 19 Terminal 20 Resistor 21 Photocoupler

Claims (4)

[Claims] 1. A transistor bridge module comprising a power transistor for driving an AC motor by an inverter, a diode, a drive circuit for the power transistor, and a circuit having a current detection function for the power transistor. A current detection device for a power module, which has an output terminal. 2. The power transistor is a transistor, M
2. The current detecting device for a power module according to claim 1, wherein the current detecting function is made of one of OSFET and IGBT, and the current detecting function depends on the current value of the sense terminal. 3. The analog output terminal is insulated via a photocoupler, and is a common ground terminal for each device in the transistor bridge.
A current detection device for the power module described. 4. The current detection device for a power module according to claim 3, further comprising a circuit for correcting the relationship between the output voltage of the photocoupler and the transistor current value in each device.