It’s a 800watt 80 PLUS Gold PSU with active PFC — https://www.deepcool.com/products/PowerSupplyUnits/powersupplyunits/PM800D-80-PLUS-Gold-Power-Supply/2021/13084.shtml
Previously I’ve tuned output voltage to 13.5 volts replacing R68 in the divider for CM6901 controller:
It’s a feedback circuit to control output voltage:
Controller wants 2.5v on this pin and if it’s lower it tries to increase voltage to get 2.5v and vice versa with lower voltage, that’s how feedback works.
But I was unable to get more than 13,5 voltage because of overvoltage protection. In this PSU (and in lot’s others modern PSUs) there is a part named supervisor that monitors current, voltage, temperature (maybe) etc.
It’s IN1S313I-DAG in this case. I was unable to find datasheet for this supervisor exactly, but I figured out that is the full analog of PS113A.
It monitors voltage on 7th pin. So I’ve looked at PCB and figured out why it allows 13,5 volts — it has a diode between 12v line and supervisor pin (D18):
So with voltage drop on this diode we are getting around 12.8 volts on the monitoring pin when output is around 13.5v. So i’ve just added one more diode between J37 and D18 to decrease voltage more and it allowed me to increase voltage on around 0,6v on the 12v line:
And we have nothing to do with 3.3v and 5v outputs because they’re produced by separate DC-DC using main 12v line.
A bunch of photos of removing unused wires 🙂
