JPH08116681A - Voltage type inverter - Google Patents

Abstract

PURPOSE: To prevent the short circuit of arms even when a gate signal becomes abnormal. CONSTITUTION: The title voltage type inverter concerns an inverter having a main circuit 1 with U- and X-phase arms composed of IGBTs, and a gate circuit 3 whose gate signals on-off-drive both arms. And a short-circuit preventing circuit 5 detects the on operation of the gate signal for the U-phase arm, and makes the gate signal for the X-phase off forcedly. As a result of this, it becomes possible to prevent the simultaneous on operation (short circuit) of the upper and lower arms even in the case of malfunctioning of the control circuit and the gate circuit 3, and in the case of noise entry into the gate signals.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage source inverter, and more particularly to a gate control circuit.

[0002]

2. Description of the Related Art A voltage type inverter is illustrated in FIG. The main circuit 1 has a bridge configuration of arms U, V, X and Y having free wheeling diodes in antiparallel with an IGBT which is a semiconductor switch. The control device 2 generates an on / off control signal for each arm U, V, X, Y of the main circuit 1 according to the output frequency / voltage command. The gate circuits 3 and 4 amplify the on / off control signal to individually gate drive the arms U, V, X, and Y.

The semiconductor switches of the main circuit 1 are replaced with various ones such as power transistors, FETs, GTOs and thyristors.

As a control method by the control device 2, there are various methods such as PWM control and a combination of this and vector control according to the demand of a load and a power supply.

In addition to an overvoltage protection circuit and an overcurrent protection circuit, as a protection circuit, in order to prevent a short circuit (simultaneous ON) of the upper and lower arms of the main circuit 1, control is performed so that ON signals are not simultaneously generated in the upper and lower arms. The gate signal is processed on the device 2 side.

[0006]

The conventional short-circuit prevention method for the upper and lower arms cannot prevent the arm short-circuit when an abnormality occurs in the gate signal as in the following cases.

(1) When an abnormality occurs in the control device 2.

(2) Between the control device 2 and the gate circuits 3 and 4,
Or when noise enters the gate circuits 3 and 4 and the gate signal lines of the main circuit.

(3) When an abnormality occurs in the gate circuits 3 and 4.

It is an object of the present invention to provide a voltage source inverter capable of preventing arm short circuit even when an abnormality occurs in a gate signal.

[0011]

In order to solve the above-mentioned problems, the present invention provides a voltage source inverter in which a semiconductor switch is used as upper and lower arms and the upper and lower arms are turned on and off by a gate signal of a gate circuit. It is characterized in that a short circuit prevention circuit for detecting ON of the gate signal of one arm and forcing the gate signal of the other arm to OFF is provided.

[0012]

The on / off of the gate signals of the upper and lower arms is detected and the gate signals of the other arms are forced to be off, thereby preventing the upper and lower arms from being simultaneously turned on.

[0013]

1 is a circuit diagram of an essential part showing an embodiment of the present invention, which is a part for applying a gate signal from a gate circuit 3 to arms of U and X phases of a main circuit 1.

Arms U and X of U and X phases to be IGBT
Short-circuit prevention circuits 5 and 6 are provided between the gate and the source of the circuit, respectively.

The short-circuit prevention circuit 5 takes in the gate signal of the U-phase arm U, detects the ON signal of the arm U, and forcibly turns off the gate signal of the X-phase arm X. Similarly, the short-circuit prevention circuit 6 takes in the gate signal of the X-phase arm X, detects the ON signal of the arm X, and forces the gate signal of the U-phase arm U to OFF.

Specifically, as shown in the short circuit prevention circuit 5, the input light emitting diode of the photocoupler PC for insulation is driven at a high level of the U-phase gate signal through the current limiting resistor R, and the output transistor of the photocoupler PC is driven. The X-phase gate signal line is short-circuited through the diode D3 by the ON operation of The diodes D1, D2 and D3 are photocouplers P
Protect the input / output device of C from reverse voltage. A current limiting resistor may be provided in series with the diode D3.

In this embodiment, the gate circuit 3 includes U,
The waveforms are such that the X-phase gate signals are phase-controlled so that they do not turn on at the same time. If the gate signals are normal, the upper and lower arms U and X will not turn on at the same time, but an abnormality will occur in the control device 2 or the gate circuit 3. In this case or when noise occurs in the gate signal line, the short circuit prevention circuits 5 and 6 prevent short circuits.

For example, when an erroneous ON signal is generated in the U-phase gate signal line during the ON period of the X-phase gate signal, the short-circuit prevention circuit 5 detects this ON signal and forcibly turns OFF the X-phase gate signal, so that the arm The simultaneous turn-on of U and X is suppressed.

On the contrary, when an erroneous ON signal is generated in the X-phase gate signal line during the ON period of the U-phase gate signal, the short-circuit prevention circuit 6 detects this ON signal and forces the U-phase gate signal to OFF, The simultaneous turn-on of arms U and X is suppressed.

In the embodiment, the semiconductor switch of the main circuit 1 is a voltage driven IGBT.
The same effect can be obtained by applying the present invention to an inverter having a current-driven semiconductor switch element such as a transistor. In the case of this current-driven semiconductor switch, it is configured as a short-circuit prevention circuit capable of interrupting or bypassing the base current and the gate current.

In the embodiment, the case of a single-phase inverter is shown, but also in a three-phase inverter or a multi-phase inverter, short-circuit prevention circuits can be provided in the upper and lower arms of each phase unit to prevent the same short-circuit.

[0022]

As described above, according to the present invention, in the voltage type inverter, the short-circuit prevention circuit for detecting the ON state of the gate signal of one of the upper and lower arms and forcing the gate signal of the other arm to OFF is provided. Since it is provided, even if an abnormality occurs in the gate signal, it is possible to reliably prevent the upper and lower arms from being turned on at the same time.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a main part showing an embodiment of the present invention.

FIG. 2 is a circuit example of a voltage source inverter.

[Explanation of symbols]

 1 ... Main circuit 2 ... Control device 3, 4 ... Gate circuit 5, 6 ... Short circuit prevention circuit

Claims (1)

[Claims] 1. A voltage-type inverter that uses a semiconductor switch as an upper and lower arm and drives the upper and lower arms on / off by a gate signal of a gate circuit, wherein the gate signal of one of the upper and lower arms is detected to be on and the other arm is detected. Voltage source inverter characterized by having a short circuit prevention circuit for forcing the gate signal of the device to turn off.