5W dimmable LED driver design with power factor correction

First, the circuit characteristics description

The RD-251 provides a single 350 mA constant current output at 12 V and 18 V LED string voltages. Using a standard AC mains thyristor dimmer reduces the output current to 1% (3 mA), which does not cause LED load performance to be unstable or flicker. The circuit is compatible with both low cost leading edge dimmers and more complex trailing edge dimmers.

This circuit is designed to operate over a universal AC input voltage range (85 VAC to 265 VAC, 47 Hz to 63 Hz), but will not cause damage over an input voltage range of 0 VAC to 300 VAC. This improves field application reliability and extends the life of online voltage dips and surges. The LinkSwitch-PL-based design provides a high power factor (>0.9) to help meet the requirements of all current international standards, making a single design universal.

The power supply is designed to meet the requirements of a standard pear-shaped (A19) LED replacement lamp. The output is non-isolated and requires a mechanical design of the housing to isolate the power output and LED load from the user.

Second, the circuit schematic

5WLED driver circuit schematic
Circuit diagram (removing the highlighted frame for non-dimming applications)

Note: C1, R22 and C12 are not assembled.

For non-dimming applications, the active attenuation circuit and bleeder circuit can be removed to detect the following components: Q3, R20, R3, R4, R10, R11, C6, and C3. Replace R7, R8, and R20 with a 0 ohm resistor.

For high voltage applications only, to match a high leakage dimmer such as the REV 300 W, fine-tune the Busch 2250 (600 W) or similar components. Replace F1 with 47/ 2W fusible resistor, replace R7 and R8 with 20, replace C6 with 220 nF, replace R10 and R11 with a minimum of 510 /0.5 W, replace C3 with 150nF, and replace R16 with 1k/0.25 W.

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