JPH07101575B2 - Switch failure detection device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an apparatus for detecting a failure state of a switch in combination with the switch.

[Conventional technology]

Conventionally, semiconductor devices such as thyristors, transistors, or diodes have been used for switches, and there is a tendency toward further computerization in the future.

[Problems to be solved by the invention]

However, a switch using a semiconductor is often in a conductive state when its element fails, and in this case, there is a problem that power is continuously supplied to the load even when a stop signal is generated and the load cannot be stopped. It was

On the contrary, there is a problem in that even if an operation signal is applied to the switch, the switch remains in a non-conducting state and the power cannot be supplied even if it is desired to supply power to the load.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a device capable of detecting whether the switch is in a conductive or non-conductive state.

[Means for solving problems]

A switch failure detection device according to the present invention includes a switching element that opens and closes a load by interposing a main circuit voltage and a load, and a control circuit that applies a control voltage to open and close the switching element. When the control voltage is applied to the control circuit,
A control circuit detecting circuit for detecting and outputting the control voltage;
Two signals are input: a load voltage detection circuit that detects and outputs the voltage of the load when the main circuit voltage is applied to the load, an output from the control circuit detection circuit, and an output from the load voltage detection circuit. And a mismatch detection circuit that outputs an output signal after a lapse of a certain time from the time when the mismatch state occurs, and the power supply of the mismatch detection circuit is output from the control circuit detection circuit and output from the load voltage detection circuit. It is characterized in that it is supplied from two outputs.

[Action]

The non-coincidence circuit of the present invention is supplied with power from two outputs from the control circuit detection circuit and the load voltage detection circuit, compares the load side voltage of the switch with the control voltage, and outputs an output signal if the above two do not match. Emit.

Example of Invention

An embodiment of the present invention will be described below with reference to the drawings. First
In the figure, (1) is a switch using semiconductor elements, (1a)
Is a TRIAC (trade name of GE company in the United States) element which is a current switching element, and (1b) is a gate to the TRIAC element (1a) by the operation of the control signal contact (3) for driving the switch (1). A control circuit for giving a signal, (2) a load device, (4) a diode having a three-phase bridge configuration for rectifying a three-phase voltage, (5) and (6) voltage dividing resistors for converting a signal voltage level, and a diode. (4), partial pressure resistance (5) (6)
Becomes a load voltage detection circuit. (7) is a non-coincidence circuit, which is composed of an exclusive OR circuit, and the two outputs of the level conversion circuit (12) and the load voltage detection circuit are connected to the inputs of the exclusive OR circuit and the power supply of this exclusive OR circuit is also connected. Also, the two outputs of the level conversion circuit (12) and the load voltage detection circuit are connected. (8) is a failure detection output, (9) is a three-phase power supply voltage of the main circuit, (10) is a control voltage for the switch drive and the input signal of the mismatch detection circuit (7), and (12) is a control voltage mismatch. Detecting circuit (7) A level converting circuit as a control circuit detecting circuit for converting to an input level.

Next, the operation will be described.

In FIG. 1, when the control signal contact (3) is turned on, a voltage is applied to the control circuit (1b) of the switch (1), the triac element (1a) becomes conductive, and power is supplied to the load (2). . At this time, a three-phase voltage is applied to the terminals of the load (2), which is full-wave rectified by the diode (4), passes through the voltage dividing resistors (5) and (6), and is input to the mismatch detection circuit (7). . At the same time, the drive voltage of the switch (1) is applied to the other input terminal of the mismatch detection circuit (7) via the level conversion circuit (12). At this time, the two input signals are both "H level", the mismatch detection circuit (7) does not operate, and the output becomes "L level". Similarly, when the load is stopped, the input signals of the mismatch detection circuit (7) both become "L level" and their outputs also become "L level".

Output (8) when the switch (1) is normal as described above
Goes to the “L” state. Also, if two triac elements (1a) in the main circuit fail and only two phases are conductive, even if the control signal contact (3) is in the off state, the load (2) passes through the conductive elements. A single-phase power is applied to.

At this time, the signal level input from the main circuit side is "H level" and the signal from the control circuit (1b) is "L level", and this signal is input to the mismatch detection circuit (7) and output signal. Then, as a result, the failure of the switch (1) is detected.
Furthermore, even if the control signal (3) is in the ON state due to a failure of the control circuit (1b) of the switch (1) or the triac element (1a), the switch (1) does not conduct and the load cannot be started. Similarly, the signal from the main circuit is "L level", and the "H level" is applied from the control circuit (1b). In this case as well, the output of the mismatch detection circuit (7) is at "H level", so an output signal is issued to detect a failure. If either of the inputs of the exclusive OR circuit 7 is at “H level”, the exclusive OR circuit 7 is exclusive.
Power is supplied to the OR circuit 7. As described above, the malfunction of the switch (1) or the contact conduction failure can be detected.

Note that FIG. 2 is a circuit for outputting from the mismatch detection circuit (7) of the circuit of FIG. 1 via the time limit circuit (11). For example, in the load such as the motor (13), residual voltage is generated at the time of disconnection. In such a load, if mismatch detection is performed immediately after switching the load, voltage is generated at the load terminal of the switch (1) and erroneous detection occurs. Will be done. Therefore, in order to perform the fault output after the residual voltage is attenuated, the fault detection output is performed through the time limit circuit (11) whose time period is longer than the residual voltage duration.

As a result, even in the case of a load such as a motor (13) in which a residual voltage is generated, it is possible to detect a failure of the switch (1) without performing erroneous detection.

By the way, in the above-mentioned embodiment, the one using the semiconductor element for the switch is shown, but it goes without saying that the same effect can be obtained by combining with the electromagnetic switch.

〔The invention's effect〕

As described above, power is supplied from the two outputs from the control circuit detection circuit and the load voltage detection circuit, the load side voltage of the switch is compared with the control voltage, and if the above two do not match, the output signal is output. Since the disagreement detection circuit for generating the above is provided, there is an effect that a failure detection device for a switch which can detect a failure of a semiconductor element of the switch and prevent runaway of a load can be obtained.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing another embodiment of the present invention. In the figure, (1) is a switch, (2) is a load, (7) is a mismatch detection circuit, (8) is an output, (10) is a control voltage,
(11) is a time circuit. In the drawings, the same reference numerals indicate the same parts.

Claims (1)

[Claims] 1. A switching element which is interposed between a main circuit voltage and a load to open and close the load, a control circuit which applies a control voltage to open and close the switching element, and the control voltage is the control circuit. A control circuit detecting circuit for detecting and outputting the control voltage when applied to the load, a load voltage detecting circuit for detecting and outputting the voltage of the load when the main circuit voltage is applied to the load, and the control circuit The output signal from the detection circuit and the output signal from the load voltage detection circuit are used as inputs, and a mismatch detection circuit that outputs an output signal after a lapse of a fixed time from the time when the mismatched state is provided is provided. A switch failure detection device characterized in that power is supplied from two outputs, an output from the control circuit detection circuit and an output from the load voltage detection circuit.