Sizing Up Circuit Protection for LED Strings

As light-emitting diodes (LEDs) find their way into more outdoor applications, they are at higher risk for electrostatic discharge (ESD) and other electrical transients. High-brightness (HB) LEDs — those with sapphire or silicone carbide (SiC) substrates and in the future aluminum nitride (AlN) and gallium nitride (GaN) substrates — are especially susceptible, and when the first LED in a string fails, the whole string goes dark. Few engineers know all the considerations of specifying circuit protection for LED strings. For example, a recent category of devices, called open LED protectors, are now available, and are not well understood. This article will discuss when to apply them, how to size them, and how to save cost by protecting multiple strings with a single device.