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.
The 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.
Triacs
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
Our ACS™ AC switches ensure the interface between a gate and an MCU with an integrated over-voltage protection (OVP) function.
SCRs
Silicon-controlled rectifiers (SCR) are the most immune switch to voltage spikes and their load commutation capability is very high.
ASD
ASDs (Application-Specific Discretes) are a collection of gas and fuel ignitors integrating SCR building blocks.
Featured Videos
The STEVAL-SCR002V1 introduces a simple and innovative AC-DC front-end circuit that allows the designer to perform an inrush current limitation in any converter with input rectifier bridge topologies.
ST’s 8H Triacs have been designed for Industrial, Building, Residential, Appliances. Based on the new ST’s technology, the 8H Triacs are able to work at 800V & 150°C without compromise. It makes 8H Triacs the right choice to run in very hot confined electronic environment and improve the reliability of your system. Thanks to 8H Triacs robust dynamic turn-off commutation and high noise immunity at high temperature you can reduce your system size while increasing functional safety.
eDesignSuite
eDesignSuite is a comprehensive set of easy-to-use design-aid utilities ready to help you streamline the system development process with a wide range of ST products.
Power Management Design Center
Thermal-electrical Simulators for Components
Signal Conditioning Design Tool
NFC/RFID Calculators
Power Supply Design Tool
SMPS design, by topology, by type and by product PFC design with analog and digitial control Supports various PCB configurations 
LED Lighting Design Tool
Handles AC-DC and DC-DC design in common topologies Displays interactive and annotated schematic Provides current/voltage graphs, Bode plots, efficiency curves and power-loss data 
Digital Power Workbench
Provides a step-by-step optimized design of power section and control loop Generates the STM32Cube embedded software package for custom applications and allows firmware project generation, compatible with multiple STM32 IDEs 
Power Tree Designer
Specify input/output power for each node in the tree Check for consistency Design each individual node 
AC Switches Simulator
Select ratings and application waveforms Get junction temperature and blocking voltage graphs Search and sort suitable devices 
Rectifier Diodes Simulator
Select ratings and application waveforms Estimate power losses Search and sort suitable devices 
STPOWER Studio
Supports long mission profiles Provides power loss and temperature graphs Helps define heatsink thermal properties 
Twister Sim
Help select the right ViPOWER Automotive power device Supports load-compatibility, wiring harness optimization, fault condition impact and diagnostic analysis Supports various PCB configurations 
TVS Simulator
Specify system ratings and surge waveform Search and sort suitable devices 
Estimate
Build simple schematics and firmware inputs in minutes Quickly generate reliable estimates of: Battery life System power consumption Bill of materials costs 
Active Filters
Handles multi-stage-designs and common topologies Returns circuit component values Provides gain, phase and group delay graphs Low Pass, High Pass and Band Pass 
Comparators
Handles most common configurations Returns circuit components values Provides I/O signal waveforms Inverting, Non Inverting, Window 
Low side Current Sensing
Returns circuit component values Provides current error graphs 
High side Current Sensing
Provides current error graphs. Help to select the right High side current sensing and shunt devices. 
NFC Inductance
Input geometry and substrate properties Get antenna impedance 
UHF Link Budget
Enter forward and reverse link characteristics The tool returns link budget estimate 
NFC Tuning Circuit
Enter antenna parameter and matching target Select the topology of the matching network The tool returns component values for the desired design targets