Thyristors (SCR) and AC Switches

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Designed for high immunity against glitches on mains and high load supplies, the Thyristors, also known as silicon-controlled rectifiers (SCR), triacs and logic-level gate ACS circuits are switches working on 120, 240 and 480 V AC power lines for appliances, tools, converters and drive systems. Thyristors (SCR) and AC Switches belong to our STPOWER family.

ThyristorsThe most energy efficient, simplest gate drive, Thyristors, are also the toughest 200 to 1400 V bidirectional switch for controlling alternating current mains power.

With a current range from 0.2 to 80 A, Thyristors are used in home and office appliances, as well as industrial automation. More concretely, AC switch circuits are included in compressor drives, water heater, power tools, static relays, roller shutters, motorbike regulators and more recently, circuit breakers and electrical vehicle chargers.

Smart-building connected objects powered by AC mains is the latest innovation where Thyristors are contributing to climate and energy controls.

To meet the wide variety of assembly automation requirements, ST's portfolio offers a full range of surface-mount SMD packages from the tiniest 0.8 A SMB Flat ACS to the power-carrier 80 A D3PAK SCRs. Our through-hole packages include the thermally excellent 2500 V ceramic-insulated TO-220 and the new full resin-molded TO-220 package.

Explore our large choice of packages for our thyristors (SCR), Triacs and ACS switches.

Quickly find the thyristor or AC switch that best fits your design by simply entering the main I/O and gate parameters in our AC Switch Simulator.



Today’s triacs are perfected with low gate current drive, high immunity and commutation at temperature (see our T series and H series).

AC Switches

AC Switches

Our ACS™ AC switches ensure the interface between a gate and an MCU with an integrated over-voltage protection (OVP) function.



Silicon-controlled rectifiers (SCR) are the most immune switch to voltage spikes and their load commutation capability is very high.


Application-Specific Discretes

ASDs (Application-Specific Discretes) are a collection of gas and fuel ignitors integrating SCR building blocks.

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