Does anyone recognise these power supplies? They’re cheap AliExpress led drivers and I want to change its output voltage to around 22V from 12V. I’ve read that the way to do this is to adjust the REF voltage on the IC that controls it. It’s a KA3845 but I don’t understand where that reference voltage is regulated. One voltage is feedback from the output where then other should be a reference.

What would be the best way to approach this? I can’t find any schematics on these boards unfortunately.

Thanks.

  • renormalizer@feddit.deEnglish
    4·
    8 months ago

    It’s probably not a good idea for actual use, but if you’d like to experiment: looks like the 3-pin devices U4 and U5 on the upper right provide feedback through the optocouplers next to the class Y cap north of the transformer. I bet those are LM431 voltage references (or similar). The passives around them provide filtering, but two of the resistors should form a resistor divider for the Ref pin (lower right pin if the single pin is on top). That divider sets the voltage.

    • Rolivers@discuss.tchncs.deOPEnglish
      2·
      8 months ago

      Thanks. I ordered the 24V model in hopes of adjusting it down to 22V. I will use that to keep a 7s Li-Ion battery at a minimum charge level whereas a solar panel array may increase that voltage higher. It looks like the 24V model’s capacitors need to be changed as well since they can’t handle the Li-Ion batterys’ max charge voltage.