Figure above shows a simple buck-boost converter, operating in open loop with no output feedback, being used as a constant current LED driver. The circuit relies on the internal current limiting function of the LNK302PN, which ensures constant current is supplied to the load. Typical uses include night-lights, neon sign replacements,emergency exit signs or any application utilizing LEDs for lighting.The AC input is rectified and filtered by D1, C1, C2, and RF2. For safety, resistor RF1 should be a fusible fl ameproof type, whereas RF2 can be fl ameproof only.
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