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How to convert a HP HSTNS-PL18 psu to 13.8V ?

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rjmusto:
Thanks eblc1388 for that. Really nice to see a schematic.

Reading through that other post, it seems my experience with the PL18 is just the same. Staying at 13.4v or lower gives no problems, going higher does.

The pot I have tweaked to get rid of the issue for me is shown in the photo.  With no values on the schematic and no component designations on the board, it is hard to be sure what I'm looking at. Could it be this pot is VR120?  In which case, what is 'IAC Detecting'? (The schematic does not say what IC160 is.)

eblc1388:

--- Quote from: rjmusto on October 17, 2021, 12:24:05 pm ---The pot I have tweaked to get rid of the issue for me is shown in the photo.  With no values on the schematic and no component designations on the board, it is hard to be sure what I'm looking at. Could it be this pot is VR120?  In which case, what is 'IAC Detecting'? (The schematic does not say what IC160 is.)

--- End quote ---

No. IC160 is UCC3818, which is responsible for PFC function at the primary side. On the schematic, if you look carefully at the ground pin of that IC, you will see a small letter 'p' inside the triangle symbol. This side is HOT, has no isolation to the mains, means it can electrocute if one touches it.

This ground on the low voltage side is a different one, which has a normal ground symbol without 'p'.

IAC detecting is the detection of line current signal after the PFC inductor used by IC160 to provide the PFC function.
 

jbuszkie:
Hello!  I've got a bunch of these supplies that I've modded with an external pot to adjust the voltage.
I'm using 4 in series to make a 48V charger.  I have to keep fiddling with the pots to make the the current "constant".
I was hoping to use some digital pots instead to have it be MCU controlled.  The problem is the  200ohm digital pot.
Has anyone played with other solutions?  Maybe a isolated voltage source to fool the feedback pin?

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