In LED Lighting applications, solid-state lighting luminaires are commonly configured with long strings of multiple series LEDs driven from a relatively high voltage compliance, constant current power supply.
This configuration has several benefits:
- Multiple LEDs can be arranged in series to simplify the power supply design.
- High voltage, low current power supply improves efficiency of the power supply.
- Modular design can allow easy scaling; for example, using 1 W LEDs - 8 W, 16 W, 24 W or 32 W designs can easily be created with multiple strings of 8 x 1 W LEDs.
- One LED streetlight design uses six strings of 15 LEDs for a total of 90 LEDs.
The LSP product is designed to make the open LED failure mode tolerable. An open LED will cause a complete LED string to go dark, rendering the application useless or markedly compromised. This can lead to warranty returns or maintenance calls.
To comply with Energy Star rating, LED lighting fixtures must:
- Have a 3 year warranty
- Produce >70 % of new light output for 35k hours (residential: 25k hours).
While low power LED string designs may have used zener diodes in this role, high power LEDs would require very large and expensive zeners. Placing a Bourns® LSP device across LEDs allows the remaining LEDs in a string to continue to work when an LED fails open circuit. LSP devices in active mode dissipate less power than the LED did.