Saturday, December 18, 2010

Weak current College】 【solid state relay: its structure and composition】.

First, solid state relay structures and electrical parameters description

SSR's structure is generally in control circuits, power output component in the following. Control circuit is divided into discrete devices and SMT surface mount technology, power output components can be divided into plastic silicon technology and single-chip parallel process. General use plastic 10-40ASSR two-way silicon package, 50-100A of SSR adopts plastic one-way-parallel package, one-way-parallel connection of technical indicators are better than two-way silicon technology. Most advanced is the use of SCR chip connection of welding technology of SSR, it features a high blocking voltage, overload ability, good thermal conditions, impact resistance, current up to thousands of amps, so foreign industrial countries are adopting the technology.

2. solid state relay is mainly composed of input circuit, driving circuits and output circuit made up of three parts

Input circuit to the input control signal provides a loop, divided into DC input and AC input, DC input is divided into resistive input and constant current input. Resistive input circuit input control currents with input voltage linear positive change, constant input circuit, the input voltage reaches a preset value, enter the control current is no longer with the voltage rise significantly increases, wide input voltage range.

Driver circuit is included isolation coupled circuit, functional circuit and trigger circuit three parts. Isolation coupled circuit, at present, the use of optically coupled and transformer coupling the two circuits. Function circuit may include detection of rectifier, zero detection, zoom in acceleration, protection and other functional circuit. Trigger circuit's role is to provide the trigger signal output devices.

Output circuit is under the control of the trigger signal, realize load currents by on-off switch. Output circuit mainly by the output device and transient suppression effect of the absorbing circuit. At present, the main use of one-way exchange of SSR, Thyristor TRIAC devices. Main DC SSR uses MOS transistor, MOSFET, IGBT insulated-Gate-type double, and so on.

AC output by using SSR devices, divided into TRIAC (TRIAC) ordinary and one-way thyristors (SCR) for enhanced connection. Because SCR device than the devices for dv/dt TRIAC, high blocking voltage is high, and good thermal performance, are used to manufacture high-voltage, high current products and for inductive, capacitive load.

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