An AC solid-state relay and a fault detection method for the relay load circuit

Abstract

An AC solid-state relay, comprising a power supply circuit, an input circuit, a silicon controlled rectifier and an alarm output circuit, is characterized in that it also includes a single-chip microcomputer, the output terminal of the power supply circuit is connected with the power supply input terminal of the single-chip microcomputer, and the output terminal of the input circuit is connected with the single-chip microcomputer The signal input terminal is connected, the alarm output terminal of the single-chip microcomputer is connected with the input terminal of the alarm output circuit; the sampling terminals of the zero-crossing sampling circuit are respectively connected in parallel at both ends of the thyristor, and the zero-crossing signal output terminal is connected with the zero-crossing signal detection terminal of the single-chip microcomputer ; The control input terminal of the thyristor trigger circuit is connected to the trigger signal output terminal of the microcontroller, the first control output terminal is connected to the control terminal of the thyristor, and the second control output terminal is connected to the cathode or anode of the thyristor. The advantage of the present invention is that: adopting the method of directly paralleling the zero-crossing signal on the thyristor, without increasing the complexity of the circuit, it not only realizes the fault detection of the load circuit, but also realizes the detection of the internal open circuit fault of the thyristor. Detection; using single-chip microcomputer control to realize the intelligence of solid-state relays and improve product safety and reliability.

Description

technical field [0001] The invention relates to an AC solid state relay and a fault detection method for a load circuit (including relay fault and load fault) of the AC solid state relay. Background technique [0002] Solid state relay (SSR for short) is a commonly used control executive device in industrial automation control. It is a non-contact switch composed of microelectronic circuits, discrete electronic devices and power electronic power devices. The isolation device realizes the isolation between the control terminal and the load terminal. . Conventional AC solid state relay internal circuit such as figure 1 The dotted line box shown generally consists of three parts: input circuit, isolation (coupling) circuit and output circuit, wherein the output circuit is composed of switching elements (such as unidirectional thyristor, bidirectional thyristor, etc.) and control circuit. [0003] In the application of electrical automatic control, where the safety and reliabi...

AI Technical Summary

Problems solved by technology

However, the above-mentioned detection method cannot be used to make the solid-state relay into a standard conventional size, and the volume and size need to be enlarged or specially customized, which makes the overall circuit structure bulky, and at the same time increases the complexity of the internal circuit and the design and manufacturing cost; In addition, using the above-mentioned The detection method is generally unable to detect the thyristor failure inside the solid state relay itself, and cannot guarantee the reliability and safety of the solid state relay

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