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Reference Design Report for a 5 W Dimmable Power Factor Corrected LED Driver (NonIsolated) Using LinkSwitchTM-PL LNK457DG

31st August 2011

Power Integrations

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This document is an engineering report describing a non-isolated LED driver (power supply) utilizing a LNK457DG from the LinkSwitch-PL family of devices. The RD-251 provides a single constant current output of 350 mA over an LED string voltage of 12 V and 18 V. The output current can be reduced using a standard AC mains TRIAC dimmer down to 1% (3 mA) without instability and flickering of the LED load. The board is compatible with both low cost leading edge and more sophisticated trailing edge dimmers.

The board was optimized to operate over the universal AC input voltage range (85 VAC to 265 VAC, 47 Hz to 63 Hz) but suffers no damage over an input range of 0 VAC to 300 VAC. This increases field reliability and lifetime during line sags and swells. LinkSwitchPL based designs provide a high power factor (>0.9) meeting current international requirements and enabling a single design to be used worldwide.

The form factor of the board was chosen to meet the requirements for standard pear shaped (A19) LED replacement lamps. The output is non-isolated and requires the mechanical design of the enclosure to isolate the output of the supply and the LED load from the user.

The document contains the power supply specification, schematic, bill of materials, transformer documentation, printed circuit layout, and performance data.