Outdoor LED strings stay illuminated even when a single LED fails

CHICAGO, USA: Littelfuse, Inc., the global leader in circuit protection, has introduced the PLEDxUx Unidirectional Series Open LED Protector, the latest addition to the company's broad portfolio of PLED Open LED protection devices.

It provides a switching electronic shunt path when one LED in a string fails as an open circuit. PLED devices are connected in parallel with each LED in a series string. If one LED fails, the PLED connected to it turns on and carries the current that would have gone through the failed LED, so the remainder of the string continues to function.

PLEDxUX devices provide reverse battery/power polarity protection for greater LED reliability. Typical applications include street, subway, runway, and tunnel lighting, as well as headlights, roadside warning lights, and signage.

PLEDxUx Series devices are compatible with 1-watt LEDs, nominally 350mA@3V. Two different low-profile packages maximize heat dissipation and layout flexibility, so they're suitable for dense board applications. In contrast with earlier open LED protection solutions such as silicon controlled rectifiers (SCRs) and zener diodes, the PLEDxUx Series offers higher reliability and lower maintenance requirements.

For example, SCRs are usually large and require additional components like resistors to set the trigger or turn-on voltage, and their trigger voltage will vary widely over temperature. Zener diodes create additional power dissipation once the LEDs they're protecting fail open. They are also not rated for large DC currents, which can shorten life or lead to catastrophic failure.