TRIAC Based Isolated AC Load Drive Equivalent Circuit Design of Solid-State Relay

Abstract

Electronic main boards generally provide the supply and control functions of a system. All electronic main boards include inputs and outputs and are designed according to the design requirements. In this study, a safe and low-cost switching mode power supply (SMPS) board is designed using a flyback converter topology to drive the AC and DC outputs. The triode for alternating current (TRIAC)-based safe and low-cost main board includes a flyback configured transformer with additional winding for driving the TRIAC as an AC output switch in noise immune quadrants II and III. TRIAC is used to switch AC outputs instead of a relay, and the isolation distances of the safety criteria are provided by an optocoupler. In this way, the relay usage is over, and one TRIAC and one optocoupler do the same work that is done by one relay. In this way, the cost of the AC output switch decreases. In addition, the number of AC switches covering the area on the printed-circuit board (PCB) of the mainboard decreases. The flyback topology is designed with half-wave rectified and the transformer is designed with extra winding for producing negative voltage with respect to primer reference for providing negative gate current of TRIAC. TRIAC-based AC output switched, safe, and low-cost main boards can be used for white good main boards, automation (PLC) applications, and automotive electronic control systems. This study provides cost-effective solutions in these areas.