Hello "again", good people.
Now, i've had this power brick made by FSP, with the intention of using it as a spare for my laptop. It's heftier than the "stock" one, but i wanna use it as the "home" PSU anyway. It says 19v / 10.53A max (200w).
Last time i tried it out (after a re-cap) and modded the feedback for a 12v output (about 2 years ago), it worked fine. Granted, i didn't have the chance to REALLY put it to work, but it powered a couple fans without a hitch.
But now, it seems to be oscillating from a certain load upwards.
With a 12w/21w bulb in series with two 2R2/5w resistors on the output, which comes out at about 1,7A / 33w load (19v out), the output looks like this.
With the same bulb, but only ONE 2R2/5w in series, which comes out at 1,95A / 38w, the output looks totally wrong (about 300mV ripple, and the "big" oscillation seems to be around 3.6kHz, with which my ears would agree, it just "sings").
The main PWM is an ST L5991D, and it uses a TSM101.
FWIW, on the output there are two Panasonic FR 470u/35v, a sort of "common mode choke", and an FC 470u/25v.
If needed, i've lifted the schematic of the secondary, so i can post that as well. It has two optocouplers; the one i figure is for the voltage feedback is a straight-ahead output->opto->zener->resistor->ground affair, so it does NOT use the TSM101 for voltage feedback. The other one is hooked up to the TSM101 and most definitely deals with the current limiting, in some manner.
I'd really appreciate some ideas how to stabilize this bugger
Now, i've had this power brick made by FSP, with the intention of using it as a spare for my laptop. It's heftier than the "stock" one, but i wanna use it as the "home" PSU anyway. It says 19v / 10.53A max (200w).
Last time i tried it out (after a re-cap) and modded the feedback for a 12v output (about 2 years ago), it worked fine. Granted, i didn't have the chance to REALLY put it to work, but it powered a couple fans without a hitch.
But now, it seems to be oscillating from a certain load upwards.
With a 12w/21w bulb in series with two 2R2/5w resistors on the output, which comes out at about 1,7A / 33w load (19v out), the output looks like this.
With the same bulb, but only ONE 2R2/5w in series, which comes out at 1,95A / 38w, the output looks totally wrong (about 300mV ripple, and the "big" oscillation seems to be around 3.6kHz, with which my ears would agree, it just "sings").
The main PWM is an ST L5991D, and it uses a TSM101.
FWIW, on the output there are two Panasonic FR 470u/35v, a sort of "common mode choke", and an FC 470u/25v.
If needed, i've lifted the schematic of the secondary, so i can post that as well. It has two optocouplers; the one i figure is for the voltage feedback is a straight-ahead output->opto->zener->resistor->ground affair, so it does NOT use the TSM101 for voltage feedback. The other one is hooked up to the TSM101 and most definitely deals with the current limiting, in some manner.
I'd really appreciate some ideas how to stabilize this bugger
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