Need help with converting power on 650 watt atx psu - Page 1
Forum section: electronics / beginners

author: jamessinghal
author_rank: Contributor
timestamp: April 19, 2017, 09:39:22 pm
content: I am currently looking into options for my new higher current power supply for my workshop, andI came since I am into building computers, I found an ATX power supply to power it, as it has the higher quality than if it was froma non-name brand company in China.The link to the PSU is:https://www.newegg.com/Product/Product.aspx?item=N82E16817139200Since computers don't need a power rail above 12v, the highest there is, is a 12v 54a rail. This would be perfect if it was 54v and 12v, but I am not sure about how to do that.My main question is, how can I convert it to higher voltage, and lower amperage (with decent efficiency), and if this isn't possible, is there another money friendly way to get about 54v and 12a max on a power supply. (I will be turning it into a variable supply)Thanks!

author: rob77
author_rank: Super Contributor
timestamp: April 19, 2017, 09:50:05 pm
content: what you need is a boost converter. but a 600W boost converter with 12V input is not a trivial circuit. i would rather design a 600W mains input PSU than a 600W boost converter.

author: GoneTomorrow
author_rank: Regular Contributor
timestamp: April 20, 2017, 02:22:18 am
content: Converting mains down to 12V and then boosting it back up to 50V is dumb and will be expensive. You just need to buy/build a direct 50V PSU.

author: Kjelt
author_rank: Super Contributor
timestamp: April 20, 2017, 11:52:41 am
content: Common available voltage output for smps is 48VDC, there are plenty of smps with 250W (Take two parallel) and 48V available. Not cheap though.

author: orbanp
author_rank: Regular Contributor
timestamp: April 20, 2017, 12:52:00 pm
content: Hi James,Here is a site that shows how to modify a PC power supply:http://www.qrp4u.de/index_en.htmlI guess in your case you would also need to rewind the transformer for the higher output voltage, not just reconfigure the output and other circuits.On this site there are a number of PC PS schematics:http://danyk.cz/s_atx_en.htmlGood luck, Peter

author: wraper
author_rank: Unknown
timestamp: April 20, 2017, 12:57:08 pm
content: Double posting in different treads is not welcome.

author: wraper
author_rank: Unknown
timestamp: April 20, 2017, 01:00:48 pm
content: Quote from: orbanp on April 20, 2017, 12:52:00 pmRewind transformer, which is not trivial. Replace rectifier, prey it is just diodes, modify feedback and protection circuity, replace capacitors, yada, yada. Basically rebuild half of the PSU. Most of those cuircuits are for old crappy bottom of the range PSUs. Nothing to do with modern 650W PSU.

author: madires
author_rank: Super Contributor
timestamp: April 20, 2017, 01:10:30 pm
content: If 48V are ok for you, you could look for a used telco 48V PSU. Those are built to last usually.

author: rob77
author_rank: Super Contributor
timestamp: April 20, 2017, 01:23:19 pm
content: Quote from: wraper on April 20, 2017, 01:00:48 pmand what is so different in modern PSUs ?ok, they have active PFC on the input.. and probably replaced the mag-amp for 3.3V with a buck converter. and of course they have a modern control and supervisor IC... otherwise the modern PSU is the same as the old one , same concepts, same SMPS topologies..

author: wraper
author_rank: Unknown
timestamp: April 20, 2017, 03:52:03 pm
content: Quote from: rob77 on April 20, 2017, 01:23:19 pmAnd now try modifying it.Googling reveals that older (2016) version of it has forward converter and synchronous rectifier on the secondary side.http://www.tomshardware.com/reviews/corsair-cx650m-psu,4770-3.html

author: rob77
author_rank: Super Contributor
timestamp: April 22, 2017, 09:41:18 am
content: Quote from: wraper on April 20, 2017, 03:52:03 pmbtw... what's so special with forward converter ? that topology is here for ages... same for synchronous rectification.i'm not saying you can use the step by step mod how-to for a old ATX supply and mod a new suypply... i'm saying the concepts are the same and it's not a problem to mod a new supply.what i would do is to disconnect th 5V and 3V3 buck converters (they might not survive the increased input voltage).. install 2 small buck converters capable of 50V input. set them to 5V and 3V3 output and feed that back to the supervisor chip to make it happy and let us run the supply. then disassemble the transformer and wind it from scratch for the higher voltage, replace the secondary mosfets (those doing the synchronous rectification ) with ones for higher voltages (60V Vds mosfet wouldn't be happy switching 50V) and adjust the feedback to reflect the higher output voltage.

author: ebastler
author_rank: Super Contributor
timestamp: April 22, 2017, 11:20:49 am
content: Quote from: Kjelt on April 20, 2017, 11:52:41 amPlenty of 48V 12A power supplies are available too; $60 to $70 on AliExpress.Can you trust those? I dunno; probably at least as far as you could trust a homebrew, modified 650W PC power supply.