Littlefuse offers new thyristor power control devices

USA: Littelfuse Inc. 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.”