Got a LED driver circuit with a resistor and diode in parrallel on the feedback line, just wondering what the diode is for?

XLSemi XL6005E1


Cheers

 

Got a LED driver circuit with a resistor and diode in parrallel on the feedback line, just wondering what the diode is for?

Pin 2 should be connected to pin 4 (VIN).
Resistor and diode, connected by circuit below are used for PWM:

See datasheet https://www.lcsc.com/datasheet/lcsc_datasheet_1810151812_XLSEMI-XL6005E1_C73345.pdf

 

This circuit board has pin 2 left floating for a "default high" as far as I can tell by the data sheet.
I'm not sure the diode is for PWM in this case. But I dont know.

 

The IC boosts the volage up. If the diode fails open. (broken wire or LED not soldered well) The voltage will get very very high. The output capacitors may fail. The supply diode may fail and the IC probably will fail. The simple answer is to add a Zener diode that, under overvoltage conditions, will pull up on the FB pin.

The circuit will work just fine without the Zener diode.

 

Thanks Ron.