JPH1042571A - Overcurrent indicating circuit for inverter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable identifying visually and definitely a switching element through which an overcurrent is passed, by providing a switching element IGBT drive circuit with an overcurrent detecting circuit and an overcurrent indicating circuit, and operating the overcurrent indicating circuit only according to control signals from two low-voltage systems. SOLUTION: If the value of current passed through IGBT exceeds a certain set values of overcurrent, the overcurrent detecting circuit built in an IGBT drive circuit 10 is actuated, which actuates an overcurrent indicating circuit 90 for indicating an overcurrent. That is, when a gate drive circuit 50 built in the IGBT drive circuit 10 is fed with a control signal from a terminal 40 for a certain time, the IGBT is turned on. When the certain set value for overcurrent is exceeded, the diode in a photocoupler 70 is brought into an on- state, and the energization of a photodiode 77 is also started. As a result, light emission is continued because of the electrical characteristics of the photodiode 77, as long as the energization lasts, which definitely indicates that an excessive current has passed through the IGBT.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an inverter circuit device for an electric vehicle, and more particularly to a control circuit for detecting and displaying an overcurrent.

[0002]

2. Description of the Related Art As disclosed in Japanese Patent Application Laid-Open No. 1-282921, a control circuit in a conventional inverter, for example, with respect to a circuit for detecting an overcurrent, particularly between a collector and an emitter electrode of an IGBT which is a switching element. It only discusses protection circuitry while monitoring voltage, but does not describe how to display the results.

[0003]

In the prior art, since the overcurrent detection circuit system uses one switching element, at least four switching elements (in the case of a two-phase inverter) are used in the multi-phase inverter drive control system of a plurality of phases. )
Is generally required, it is not clear which switching element of which phase activated the overcurrent protection circuit.

[0004] It is an object of the present invention to provide a display method as an inverter circuit device for an electric vehicle, in which a switching element portion in which an excessive current has flowed can be clearly and visually determined, and a stable operation of the detection circuit. Is to do.

[0005]

According to the present invention, a circuit for driving an IGBT, which is a switching element, is provided with a circuit for detecting an overcurrent and an overcurrent display circuit. The overcurrent display circuit is operated only by two low-voltage control signals.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG. In FIG. 1, reference numerals 1, 2, 3, 4, 5, and 6 denote IGBTs as switching elements, and an IGBT drive circuit 1
On, off switching operations are performed by 0, 11, 12, 13, 14, and 15, and the electric motor 7 is driven. Note that an element other than the IGBT can be used as the semiconductor element. Terminals 40, 41, 42, 43, 44,
A control signal from a main control circuit (not shown) is input to 45. A high-potential (+) voltage is input to the terminal 30,
A high-potential ground is input to the terminal 31.

FIG. 2 shows an internal circuit of the IGBT drive circuit 10 shown in FIG. 1. The overcurrent display circuit 90, the photocoupler 70, and the inverter gate elements 71, 72, 8
5, AND gate element 75, gate control circuit 50, transistor 76, resistors 78, 79, 80, 81, 82,
83, terminals 60, 61, 62, 63, 64, 65, 6
6, 67, 68, JK flip-flop elements 73, 7
4, a capacitor 84 and a photodiode 77.

An operation example of the overcurrent display circuit of the inverter having the above configuration will be described.

In FIG. 1, when the control signal A is input to the terminal 40 from the main control circuit and the control signal D is input to the terminal 43, the IGBT driving circuit 10 and the IGBT driving circuit 13
Is activated, and the (+) voltage of the high potential
T1 is energized and applied to the motor 7, and then the IGBT
4, the current flows to the high-potential system ground applied to the terminal 31. If the current flowing through the IGBT 1 through this path exceeds a certain overcurrent set value, the IGBT 1
The circuit for detecting an overcurrent built in the drive circuit 10 operates, and the circuit for displaying the overcurrent operates based on the result. Next, a detailed description will be given including FIG.
When the control signal A, which is a (+) potential ON voltage signal having a certain time (tentatively, time T1), is input from the terminal 40 to the gate drive circuit 50 incorporated in the IGBT drive circuit 10, the IGBT 1 is turned on. If any one of IGBT2, IGBT4 and IGBT6 is in the ON state in this state, a current will flow through IGBT1, but as this current value increases, IGBT1
Of the IGBT also rises from the electrical characteristics of the IGBT. This collector-emitter voltage is always detected by the gate drive circuit 50. When the voltage exceeds a certain overcurrent set value, the (+) voltage of the potential at the terminal 60 (for example, the voltage 1)
Is output, and the voltage 1 is applied to the resistor 78, thereby turning on the diode of the photocoupler 70. Here, it is assumed that a certain voltage (−) is input to the terminal 61.

When the diode of the photocoupler 70 is turned on, a certain potential (+) applied to the terminal 62 is applied.
A voltage (assuming that the voltage is 2 and the terminal 63 is applied with a low-voltage ground potential) causes a current supplied to the resistor 79 to flow through the transistor of the photocoupler 70, and the resistor 79, The terminal voltage of the capacitor 84 which has been charged to the potential of the voltage 2 by the resistor 83 is discharged, and the input voltage of the inverter gate element 85 is changed from the potential applied by the resistor 82 to the photocoupler 7.
Since the potential becomes almost the same as the saturation voltage of the transistor 0,
The (+) voltage of a certain potential generated at the output of the inverter gate element 85 is applied to the input of the inverter gate element 72, and the CK terminal of the JK flip-flop element 74 is generated at the output of the inverter gate element 72. Almost 0
A voltage of V potential is applied. As a result, in synchronization with the falling edge of the CK terminal of the JK flip-flop element 74 (however, a reset signal from the main control circuit is appropriately input from the terminal 66 to the CLR terminal), one input section of the AND gate element 75 The signal of (+) potential having a certain time (tentatively time T2) is applied to the JK flip-flop element 74.
The control signal A input from the terminal 40 is input to the input terminal of the inverter gate element 71 almost in synchronism with the other input portion, so that the input terminal J-
From the Q terminal of the K flip-flop 73, the CK
A period of time synchronized with the falling edge of the voltage input to the terminal (however, a reset signal from the main control circuit is appropriately input from the terminal 65 to the CLR terminal) (tentatively time T3)
(+) Potential signal is input. As a result, A
When a (+) potential voltage generated at the output of the ND gate element 75 is applied to the resistor 80, a sufficient current starts to flow through the base electrode of the transistor 76 to drive the element. Since a voltage having substantially the same potential as the voltage 2 is applied between the collector and the emitter of the element, energization of the resistor 81 and the photodiode 77 is started. The light emission is continued from the electrical characteristics of the photodiode 77, and as a result, it is clearly displayed that an excessive current has flowed through the IGBT1.

Here, the signal generated from the output of the AND gate element 75 and the JK flip-flop element 7
Signals generated from the Q terminal outputs of 3, 74 are transmitted to the main control circuit from terminals 64, 67, 68, respectively.

[0012]

According to the present invention, since the overcurrent detection point can be determined at a glance by the light emitting action of the photodiode, the investigation time is drastically shortened.
Also, the overcurrent display circuit has a circuit configuration for comparing and judging from two system signals of a low voltage system overcurrent detection signal from the drive circuit for operating the semiconductor element and a low voltage system control signal from the main control circuit. As a result, a stable control circuit in which malfunction of the circuit is suppressed can be configured.

[Brief description of the drawings]

FIG. 1 is a block diagram of a control system according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of the IGBT drive circuit 1 in FIG.

[Explanation of symbols]

1 to 6: IGBT, 7: electric motor, 10 to 15: IGBT
Drive circuit, 50: IGBT gate circuit, 90: Overcurrent display circuit.

Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical display location H03K 17/08 H03K 17/08 B

Claims (1)

[Claims] 1. An inverter device for driving the electric motor with an AC power supply obtained by switching a semiconductor element from a DC power supply of an electric vehicle, wherein the semiconductor elements are connected in pairs on a (+) side and a (-) side, A semiconductor drive circuit for switchingly driving the semiconductor element is provided in the inverter device, and the semiconductor drive circuit includes a detection circuit for detecting an excessive current flowing through the semiconductor element, and detects an excessive current generated by the detection circuit. A circuit for receiving a current detection signal is provided, and a control signal from a main control circuit for controlling the inverter device and an overcurrent detection signal from the semiconductor drive circuit are taken in, and overcurrent is displayed while comparing and judging the two control signals. An overcurrent display circuit for an inverter, characterized in that it is a circuit that performs the operation.