Bypass and reverse polarity protection
LEDs are fragile solid-state devices. An LED is essentially a diode, structured as a P-N junction that emits light when forward biased. One of the major causes of an electrical open in an LED is thermo-mechanical stress on the wire bonds. Other causes of LED open circuits are electrostatic discharge (ESD) events or surges induced by nearby lightning events. These threats are especially high in outdoor applications.
Open LED protection is designed as an electronic shunt which provides a current bypass in the case of an open circuit caused by a single LED failure. It is an internally triggered two-terminal device which automatically resets if the LED heals itself or is replaced. The protector is a voltage-triggered switch with low leakage on the order of microamps that becomes a low-impedance switch when it is triggered on, which minimizes power consumption. An LED in the on-state drops approximately 3.0V, which is not sufficient to turn on the protector device. Once an LED fails open, there is sufficient circuit voltage to trigger the protector to the on-state when it is placed in parallel with the LED.
PLED5 Series Devices Solution:
The PLED5 Series provides three methods for increasing the reliability of LEDs
Open LED bypass
ESD protection up to +/-8kV contact; +/-15kV air (IEC61000-4-2, Level 4)
Reverse polarity protection in case
If ESD is a concern, the IEC 61000-4-2 can be consulted to find information on the test method and transient waveform that should be used.