PSU holdup time vs UPS switching time

[minitt]

hi,

i have a 1.2 year old PSU, which i want to modify to increase it's Hold up time.

Because my PC (even during less intensive usage) sometimes restarts during AC brownout/Blackout.

The UPS is rated at 800 va (24V system 2 X 12V@ 8amp each.Both batteries are new) which holds the PC fine most of the time except recently.

So my guess is the Secondary Filtering stage capacitor (on 12v rail) within the PSU could be bad or need a bigger one Or may be the solution lies somewhere else.

Thanx in advance for ur help.

(English is not my native lang so excuse me if i gave u a hardtime )

[kc8adu]

Re: PSU holdup time vs UPS switching time

replace the primary caps with larger uf.
had an industrial pc that would glitch at ups switchover.
had 470uf x2 in the primary.used 1000uf.
fixed the issue.i then discovered that the original caps were high esr and read a bit over 100uf on a tester.
so new 470's would have likely fixed it too.
nothing else on this ups glitched either.

[goodpsusearch]

Re: PSU holdup time vs UPS switching time

Increase capacitance at output and input big caps is what I would try to do at first.

[minitt]

Re: PSU holdup time vs UPS switching time

Just looked in to PSU and the model is DLP 50 W/Actv. PFC by Delux that uses a Single Primary capacitor with 100uf @400v - Teapo.

So, please advice proper replacement for this specific CAP.

thanx.

[minitt]

Re: PSU holdup time vs UPS switching time

i just found something interesting.

PSU with Active PFS has problem with UPS that gives output in modified Sine Wave.

is this true???

[Colt45ws]

Re: PSU holdup time vs UPS switching time

Yes, though Ive read its only a problem if input voltage is 240. I didnt quite understand the technicalities, but a Modified Sine Wave causes the PFC to output a higher voltage on the primary side than it should, sometimes causing it to over volt the primary input cap(s). For some reason 120 does not affect it like this or does not make it over volt. I went though the thread with all this; Ill see if I can find it.

Edit Heres one: https://www.badcaps.net/forum/showthread.php?t=5181

[minitt]

Re: PSU holdup time vs UPS switching time

dats some nice info....

Btw the place where i live has a 220V system ....

So, replacing the Single primary Cap (100uf @400v ) to something bigger should shoot the problem???

if so, can someone tell me the spec for replacement capacitor?

thnx.

[goodpsusearch]

Re: PSU holdup time vs UPS switching time

Post us some pics of the psu

[gonzo0815]

Re: PSU holdup time vs UPS switching time

Active pfc circuit`s are in most cases voltage regulated step up converter. So as long as the A-PFC circuits output voltage is higher then the input voltage, i do not see any problems there.
The charging voltage for the capacitor is always around 400v to near 450v, regardless of the input voltage.