Converting ATX psu to provide 19V output.

[avitsur]

I have an ATX power supply with a 2005Z ic. I would like to convert it so that it will provide 19V instead of the 12V. from what I've learnt so far (from amyk's response) that the voltage can be increased by disconnecting the V12 (pin6) to the ic but in that case, to which value the voltage will be increased? what will set/limit it?

[magic]

If it's forward topology, you may not have enough output voltage to make it to 19V even at 100% duty cycle.
If it's flyback topology found in junk PSUs, you will run a risk of blowing primary switches due to 58% increased primary voltage.

Are there any common topologies in ATX where this has a chance of working?

[strawberry]

-5 and +12 is 17V
or use boost converter

[magic]

-5V is no longer available on most PSUs.
Even if it is, permissible load is unlikely to exceed 1A.

The opposite could work, i.e. -12V and +5V, but very low current again.

[elektryk]

Are there any common topologies in ATX where this has a chance of working?

Old ATX power supplies mainly from "black list" used TL494 and BJTs in half bridge, after removing NFB there was about 24V on 12V line without load.

[TERRA Operative]

Does it have to be an ATX PSU? Many laptop chargers run at 19V

[CaptDon]

What about the 16vdc rated capacitors on the 12vdc output line? They will probably convert themselves to missiles after a couple of hours.

[avitsur]

What about the 16vdc rated capacitors on the 12vdc output line? They will probably convert themselves to missiles after a couple of hours.

I'm aware that they have to be replaced, say 25V.

[MathWizard]

One thing to consider (if money is no problem) is adding an step-up DC-DC converter. IDK what your current needs to be, but a lot of ATX PSU's these days only make the 12V output from the main SMPS, and then have other buck-type stages for 12V to 5 and 3V3. So if the the parts where choosen correctly, or the correct addon PSU was added, it should be easy to get 19V and whatever current  (within power limits/etc).

As for doing it by modding the original, yeah IDK what the max output voltage might be. The main coupled inductor/transformer has some turns ratio, raising the input voltage to that from say 340VDC, gets into pretty dangerous levels, for me anyways, and then some parts like caps would need higher voltage ratings, etc.

Whatever was done, all the over/under protection circuits would have to be altered, and the feedback loops, and more than I can probably imagine to get it to work right.

Personally IDK enough yet do make any big changes to ATX PSU's, but I have a box of them, some I fixed, some I'll look at again soon. But they are too old to sell, they are just for fun and backup's, although IDK how much I trust any of them.