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.
empireOfLove@lemmy.one 1 year ago
Considering there is a fixed-stepdown 12 volt AC transformer on the line side of that board, I’d be surprised if you will change anything via IC’s.
SomeoneSomewhere@lemmy.nz 1 year ago
That’s not a mains frequency transformer. Not enough steel. It’s a high-frequency all-switchmode supply.
However, that’s not to say you can simply adjust the feedback and have it safely deliver near twice the voltage. The secondary side diodes and capacitors probably won’t be up to it, or will have a very limited life.
The transformer does have a ratio, and the marking makes it clear that this is a specific part for the 12V model. How much leeway there is will depend on topology. Flyback are generally fairly flexible. Other types less so.
Starting with a 24V model and either adjusting the feedback resistors or adding a few diodes would be near trivial. Many will already have a potentiometer that provides that degree of adjustment. Starting with a 12V model is an uphill battle.
user134450@feddit.de 1 year ago
indeed it looks like a Royer oscillator in there (because there are transistors before AND after the tranformer).
Rolive@discuss.tchncs.de 1 year ago
Well there certainly is some regulation because attaching a load does not decrease the voltage by much. Increasing the voltage is indeed ambitious for the 12V model but lowering the voltage of the 12V model seems doable.