LED light circuit protection diagram

Connect a PolySwitch device in series with the LED light power supply circuit to provide overcurrent protection. In addition to overcurrent protection, the PolySwitch device can provide overtemperature protection if it is thermally bonded to the metal core circuit board or LED heat sink.

A Tyco Electronics ROV Metal Oxide Varistor (MOV) placed across the input helps provide overvoltage protection in the LED modules.

Placing a PolyZen device on the input of the LED driver helps protect your driver from inadvertent exposure to overvoltage and reverse polarity events

In the event the driver circuit does not require input protection the driver output can still be protected from short circuit or other load anomalies. PolySwitch devices may be used to help protect driver outputs from inadvertent short circuits or other load anomalie.

If an LED does not have built-in ESD protection, a PESD protection device placed in parallel with the LED can help protect against ESD damage.

Inherently limited power sources - a transformer, power supply, or battery - may have protective devices as long as they are not relied upon to limit the output of the Class 2 supplies. Non-inherently limited power sources by definition, have a discrete protective device that automatically interrupts the output when the current and energy output reaches a prescribed limit. Tyco Electronics provides designerswith awide range of circuit protection devices that help ensure safe operation of Class 2 power sources for LED lighting applications. As an example, in Figure 7, the addition of an MOV in coordination with a PolySwitch device on an output circuit branch enables a power supply to meet the requirements of UL 1310 paragraph 35.1 overload test on switches and controls.

Problem: Thermal Runaway If the cooling vents in a monitor become blocked, the heat generated by the LED backlighting can increase and lead to thermal runaway if the LED driver circuit is a constant voltage or constant luminous flux type. Solution: PolySwitch Devices Careful consideration must be used to determine an appropriate location to thermally bond the PolySwitch device in the optimum location to interrupt the current in the event the LCD is operated when the vents are blocked in the LCD housing.

Source: 2Pro, PolySwitch, PolyZen, Raychem, SiBar, TE logo and Tyco Electronics are trademarks. www.circuitprotection.com