I have a AC/DC adapter P-1650-22 (used to power a notebook) laying around. I would like to use it for other purposes, i.e. as a constant voltage source for LEDs.
The problem is, that the output voltage is set to 19 V, though I would like it to operate at 11 V - 12 V. The power rating would not exceed the actual rating of 65 W. It would be even less (45 W).
Currently I have no schematic, but I opened up the device already to take some measurements.
Simultaneously I searched the web and have already seen similar products and also some schematics and block diagrams. Please excuse the bad quality of the schematics, but I couldn't find a better one (relevant information is visible though).
From the information I have gathered so far I assume this is a flyback converter.
Would you say that it is worth to tweak some components in order to reduce the output voltage of this device?
For sure I would need to:
Adjust feedback resistive divider for the shunt voltage reference
What else to think of?
What about the need of adjusting the compensation loop (if there is one)?
Circuitry around the LNK6777E (the IC connected to the second winding)
Concerning point 3, I am not really sure what the LNK6777E exactly does and where to tweak (please see the block diagram):
What is the purpose of the "FB" pin? I am aware, that it serves for the regulation of the second winding. So the LNK regulates its own supply voltage. But how is the feedback coming via the optocoupler incorporated via pin "CP"?
So my question is:
What should I consider which I have not already written about?
1st edit: @Bimpelrekkie, why dou you not recommend changing anything? There are safe ways of working on circuitry connected to mains, i.e. isolation transformer, etc. BTW, reading your answer again I think you missunderstood me. My question about the "FB" pin relates to LNK6777. I am well aware this is the feedback niput but I wanted to know, relating to the block schematic I have posted above, how exactly the regulation works, etc.