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Adjusting SMPS output voltage
(discuss.tchncs.de)
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.
indeed it looks like a Royer oscillator in there (because there are transistors before AND after the transformer).
TO220 package diodes are pretty common in SMPS applications, so I'm not sure that's a guarantee.
EDIT: Not sure what you're getting at here? Royer doesn't seem to need anything other than a rectifier on the secondary, and plenty of topologies use two power transistors on the primary.
The second smaller transformer below the main one does tend to suggest it could be a Royer, at least from my reading. I don't see the extra switches needed for it to be a PFC stage.
There's still a little SO-8 and optocouplers.
skipped reading the silkscreen … it says Q1 on the lowermost package but the other three are diodes. so could also be a forward converter or something similar.