LED DESIGN FORUM: Coordinated schemes provide circuit protection for LED lighting (MAGAZINE)

Utilizing a coordinated circuit protection scheme based on several device types can help designers reduce component count, provide a safe and reliable product, comply with regulatory agency requirements, and reduce warranty and repair costs, writes FARAZ HASAN.

LED technology has advanced rapidly, with improved chip designs and materials facilitating the development of brighter, more energy efficient, and longer-lasting light sources that can be used in a wide spectrum of applications. In spite of the technology’s growing popularity, LED light manufacturers continue to wrestle with the fact that LED luminaires are extremely heat-sensitive. Without adequate thermal management, heat can degrade the LED’s lifespan and affect color output. Also, because LED drivers are silicon devices, they can fail short. This means fail-safe back-up overcurrent protection may be required.

Resettable polymeric positive temperature coefficient (PPTC) devices have demonstrated their effectiveness in a variety of LED lighting applications. Like traditional fuses, they limit current after specified limits are exceeded. However, unlike fuses, PPTC devices have the ability to reset after the fault is cleared and the power is cycled. A variety of overvoltage protection devices—including metal oxide varistors (MOVs), electrostatic-discharge (ESD) surge protection devices, and polymer-enhanced Zener diodes—can be used in a coordinated scheme with PPTC devices to help improve LED performance and reliability.

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This article was published in the Jan/Feb 2010 issue of LEDs Magazine. To read the full version of this article, please visit our magazine page, where you can download FREE electronic PDF versions of all issues of LEDs Magazine. You can also request a print copy of LEDs Magazine (available by paid subscription) and sign up for our free weekly email newsletter.

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