Thyristor Power Control Devices expand usable range of lighting.

Press Release Summary:

Alternistor Triac (Q6008LH1LED and Q6012LH1LED Series) and QUADRAC (Q6008LTH1LED and Q6012LTH1LED Series) Thyristor Power Control Devices are designed for use as switch in dimmer circuit to adjust light output of LED bulbs and strings. Products let designers of AC line-based dimmers for LED lighting accommodate range of operating parameters without reducing reliability or dimmer performance. Consequently, single control device can be used for LED-based dimmers or for combination dimmers.

Original Press Release:

Thyristor Power Control Devices from Littelfuse Expand Usable Range of Lighting Spectrum for LED, CFL, and Incandescent Loads

Ensures robust switching performance for AC line based LED dimmer applications

CHICAGO — Littelfuse, Inc., the global leader in circuit protection, has introduced two new Alternistor Triac and two new QUADRAC Thyristor Power Control Devices. These devices are designed for use as the switch in a dimmer circuit to adjust the light output of Light Emitting Diode (LED) bulbs and strings. They allow designers of AC line based dimmers for LED lighting to accommodate a wide range of operating parameters without sacrificing reliability and without degrading the performance of the dimmer. As a result, a single control device can be used for LED-based dimmers or for combination dimmers designed for incandescent, compact fluorescent lamp (CFL), and LED loads.

“For the designers of environmental or theme lighting, the introduction of LED lighting has created some significant technical challenges. For example, these new lamps and strings have extremely low current draw, which causes traditional thyristors to turn off early, making it impossible to access one range of the lighting spectrum,” said Corey Deyalsingh, Product Director of the Littelfuse Thyristor Power Control Devices product line. “The low load current capability of these new thyristors makes it possible to create a single dimmer design that will cover all dimmable lighting loads: LEDs, CFLs, and traditional incandescents. The high rate of rise of current through these thyristors (di/dt) during turn-on and high junction temperature rating ensure greater reliability and design flexibility. Our new QUADRAC devices further simplify circuit design and assembly by combining a diac and a triac in a single package.”

The Alternistor Triacs (Q6008LH1LED and Q6012LH1LED Series) and QUADRACs (Q6008LTH1LED and Q6012LTH1LED Series) Thyristor Power Control Devices offer these key features and benefits:


• Max holding current as low as 6mA

• UL recognized TO-220AB package

• 110°C rated junction temperature

• Static dv/dt performance of 35V/µs

• di/dt performance of 70A/µs

• QUADRAC version includes integrated DIAC

• Gated Triacs have 10mA gate sensitivity


• Full control of light output at the extreme low end of load conditions

• 2500VAC min isolation between mounting tab and active terminals

• Improves margin of safe operation with less heat sinking required

• Provides enhanced immunity from electrical noise

• Enables survivability of typical LED load operating characteristics

• Simplicity of circuit design and layout

• 600 Volts blocking capability


Littelfuse Alternistor Triacs (Q6008LH1LED and Q6012LH1LED Series) and QUADRACs (Q6008LTH1LED and Q6012LTH1LED Series) are available in quantities of 500 in bulk and in tube packaging. Samples are available now for bulk orders; sample requests can be placed through authorized Littelfuse distributors worldwide. For a listing of Littelfuse distributors, please visit

For More Information

Additional information is available on the following product pages, including datasheets: 

• Q6008LH1LED and Q6012LH1LED Series Alternistor Triacs

• Q6008LTH1LED and Q6012LTH1LED Series QUADRACs

If you have technical questions, please contact: Corey Deyalsingh, Product Director, Littelfuse Thyristor Power Control Devices,

About Littelfuse

Founded in 1927, Littelfuse, Inc., the worldwide leader in circuit protection, offers the industry’s broadest and deepest portfolio of circuit protection products and solutions. Littelfuse devices protect products in virtually every market that uses electrical energy, from consumer electronics to automobiles to industrial equipment. In addition to its Chicago, Illinois, world headquarters, Littelfuse has more than 30 sales, distribution, manufacturing and engineering facilities in the Americas, Europe and Asia. Technologies offered by Littelfuse include Fuses; Gas Discharge Tubes (GDTs); Positive Temperature Coefficient Devices (PTCs); PulseGuard® ESD Suppressors; SIDACtor® Devices; Silicon Protection Arrays (SPA®); Switching Thyristors; TVS Diodes and Varistors. The company also offers a comprehensive line of highly reliable Electromechanical and Electronic Switch and Control Devices for commercial and specialty vehicles and Sensors for automobile safety systems, as well as Protection Relays and underground Power Distribution Centers for the safe control and distribution of electricity.

For more information, please visit the Littelfuse website:


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