Adjusting SMPS output voltage (discuss.tchncs.de)

submitted 9 months ago by Rolive@discuss.tchncs.de to c/askelectronics@discuss.tchncs.de

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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.

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[-] Rolive@discuss.tchncs.de 1 points 9 months ago

Replying to myself for informational reason. Modifying voltage was more or less successful. Both optocouplers transmit a reference voltage, so both need to be adjusted simultaneously.

This can be done by changing the value of R19, a 23.2k smd resistor close to the output terminals.

I've attached a 10k pot with a 10k and 6.8k resistor in series and successfully modified the voltage down to 22.5.

The power supply itself is a piece of crap though. It claims to handle 400W but anything over 150W causes the short circuit protection to activate, never mind overheating at 150W very quickly.

this post was submitted on 03 Nov 2023

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