Author Topic: What's wrong with my led driver circuit?  (Read 3500 times)

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What's wrong with my led driver circuit?
« on: May 11, 2017, 02:51:36 AM »
Excuse me if my question is too specific. I'm trying to get an LED driver using PT4115 work. I've spent hours but no success. I've created exactly the circuit depicted in the datasheet.

I have used 0.33ohm resistor (0.300mA), 95uH inductor, 100uF capacitor and 1N5819 diode. I've checked all parts a hundred times. When I power the circuit with 12V DC I measure 4.3V at the DIM pin, I think this is a good sign the chip is working. But when I put a resistor as the load it seems as if this is short circuit and I get no constant current, for example with 22ohms I get 520 mA instead of expected 300 mA. I have no experience with buck convertors, what can be wrong?