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Pico-PSU @ 200-250W?

Started by geos October 8, 2018
I'm looking for 200-250W ATX Pico-PSU power supply. I see on Chinese 
sites that they sell such things rated at this wattage for 20-30$, for 
example:

https://www.aliexpress.com/item/DC-12V-250W-Pico-ATX-switch-PSU-24pin-MINI-ITX-ATX-High-Power-Supply/32629921198.html?spm=a2g0s.8937460.0.0.4eb72e0ev6xyVU

My questions is: when looking at the components used, general design 
etc. -- do you, experienced in electronics, have a feeling that such 
power supply can handle 200-250W with no issues? Does such product look 
reliable/reasonable to you? Or better I should not trust this bold 
marketing presented there and look for something else?

I would appreciate your opinion.

thank you,
geos
On 2018/10/08 9:26 AM, geos wrote:
> I'm looking for 200-250W ATX Pico-PSU power supply. I see on Chinese > sites that they sell such things rated at this wattage for 20-30$, for > example: > > https://www.aliexpress.com/item/DC-12V-250W-Pico-ATX-switch-PSU-24pin-MINI-ITX-ATX-High-Power-Supply/32629921198.html?spm=a2g0s.8937460.0.0.4eb72e0ev6xyVU > > > My questions is: when looking at the components used, general design > etc. -- do you, experienced in electronics, have a feeling that such > power supply can handle 200-250W with no issues? Does such product look > reliable/reasonable to you? Or better I should not trust this bold > marketing presented there and look for something else? > > I would appreciate your opinion. > > thank you, > geos
Get one that is UL or CSA rated for safeties sake. There is a lot of badly made stuff out there. Counterfeits abound! And there are counterfeit CSA/UL labels too I expect, but it seems much rarer as I hope those agencies chase fake labels down. John :-#)# -- (Please post followups or tech inquiries to the USENET newsgroup) John's Jukes Ltd. MOVED to #7 - 3979 Marine Way, Burnaby, BC, Canada V5J 5E3 (604)872-5757 (Pinballs, Jukes, Video Games) www.flippers.com "Old pinballers never die, they just flip out."
On 10/08/2018 12:26 PM, geos wrote:
> I'm looking for 200-250W ATX Pico-PSU power supply. I see on Chinese > sites that they sell such things rated at this wattage for 20-30$, for > example: > > https://www.aliexpress.com/item/DC-12V-250W-Pico-ATX-switch-PSU-24pin-MINI-ITX-ATX-High-Power-Supply/32629921198.html?spm=a2g0s.8937460.0.0.4eb72e0ev6xyVU > > > My questions is: when looking at the components used, general design > etc. -- do you, experienced in electronics, have a feeling that such > power supply can handle 200-250W with no issues? Does such product look > reliable/reasonable to you? Or better I should not trust this bold > marketing presented there and look for something else? > > I would appreciate your opinion. > > thank you, > geos
I have a few of those the ~150 watt variant. The problem is that they're strict ATX-voltage-spec power supplies while being non-isolated, they have all the rails +3.3, +5, +12, -12 rated for some number of amps current per. They can probably do 250 watts if the load is evenly distributed among the rails, however for modern PCs the ATX spec is kinda obsolete, the bulk of the current in even a modern low-power media center PC with a discrete GPU is going to be coming off the 12 volt bus, while if you have solid state hard drives as is common nowatimes the -12 and +5 are going to be doing just about jack shit with maybe a little draw from the 3.3 rail for the GPU and memory. Each rail on those is provided by its own lil non-isolated buck/buck-boost/inverter circuit capable of some max current per. Check the spec for the 12 volt rail as that's the important one. it's usually kinda wimpy so you can't power nearly as beefy a system as you could as say from a 250 watt "box" PSU which is using a flyback or some kind of forward bridge topology, where all the outputs are tapped off the same transformer so the 12V rail can pull more if the other rails are lightly loaded. A possible solution such as it is I'm currently experimenting with is modding a 150 watt unit by beefing up the 5 volt rail, which is underutilized, and then using a ~50-100 watt boost from that up to 12 to give the 12 volt supply rail some more oomph while still keeping the total PSU size fairly compact and fanless.
On 10/08/2018 01:03 PM, John Robertson wrote:
> On 2018/10/08 9:26 AM, geos wrote: >> I'm looking for 200-250W ATX Pico-PSU power supply. I see on Chinese >> sites that they sell such things rated at this wattage for 20-30$, for >> example: >> >> https://www.aliexpress.com/item/DC-12V-250W-Pico-ATX-switch-PSU-24pin-MINI-ITX-ATX-High-Power-Supply/32629921198.html?spm=a2g0s.8937460.0.0.4eb72e0ev6xyVU >> >> >> My questions is: when looking at the components used, general design >> etc. -- do you, experienced in electronics, have a feeling that such >> power supply can handle 200-250W with no issues? Does such product >> look reliable/reasonable to you? Or better I should not trust this >> bold marketing presented there and look for something else? >> >> I would appreciate your opinion. >> >> thank you, >> geos > > Get one that is UL or CSA rated for safeties sake. There is a lot of > badly made stuff out there. Counterfeits abound! And there are > counterfeit CSA/UL labels too I expect, but it seems much rarer as I > hope those agencies chase fake labels down. > > John :-#)# >
The ones I got off AliExpress/eBay from sellers with good reviews seem okay and do what they say on the tin, they're just not "real" 250 watt PSUs in the way a flyback or forward bridge 250 watt PSU is. Aside from the (through hole in mine) capacitors being mystery meat the manufacturing quality doesn't seem much different than your average PC motherboard you'd get from NewEgg or something. Most of the converters on the board are "Richtech" chips like this with a couple of MC34063s looks like <https://www.richtek.com/Products/PC%20System%20Buck%20Controller/RT8223N?sc_lang=en>
On 10/08/2018 01:13 PM, bitrex wrote:
> On 10/08/2018 12:26 PM, geos wrote: >> I'm looking for 200-250W ATX Pico-PSU power supply. I see on Chinese >> sites that they sell such things rated at this wattage for 20-30$, for >> example: >> >> https://www.aliexpress.com/item/DC-12V-250W-Pico-ATX-switch-PSU-24pin-MINI-ITX-ATX-High-Power-Supply/32629921198.html?spm=a2g0s.8937460.0.0.4eb72e0ev6xyVU >> >> >> My questions is: when looking at the components used, general design >> etc. -- do you, experienced in electronics, have a feeling that such >> power supply can handle 200-250W with no issues? Does such product >> look reliable/reasonable to you? Or better I should not trust this >> bold marketing presented there and look for something else? >> >> I would appreciate your opinion. >> >> thank you, >> geos > > I have a few of those the ~150 watt variant. The problem is that they're > &#2013266080; strict ATX-voltage-spec power supplies while being non-isolated, they > have all the rails +3.3, +5, +12, -12 rated for some number of amps > current per. > > They can probably do 250 watts if the load is evenly distributed among > the rails, however for modern PCs the ATX spec is kinda obsolete, the > bulk of the current in even a modern low-power media center PC with a > discrete GPU is going to be coming off the 12 volt bus, while if you > have solid state hard drives as is common nowatimes the -12 and +5 are > going to be doing just about jack shit with maybe a little draw from the > 3.3 rail for the GPU and memory. > > Each rail on those is provided by its own lil non-isolated > buck/buck-boost/inverter circuit capable of some max current per. Check > the spec for the 12 volt rail as that's the important one. it's usually > kinda wimpy so you can't power nearly as beefy a system as you could as > say from a 250 watt "box" PSU which is using a flyback or some kind of > forward bridge topology, where all the outputs are tapped off the same > transformer so the 12V rail can pull more if the other rails are lightly > loaded. > > A possible solution such as it is I'm currently experimenting with is > modding a 150 watt unit by beefing up the 5 volt rail, which is > underutilized, and then using a ~50-100 watt boost from that up to 12 to > give the 12 volt supply rail some more oomph while still keeping the > total PSU size fairly compact and fanless.
You could probably run an Atom-based x86 system off a "200 watt" PSU like that, stock, maybe a low-power Celeron, but I don't think it'll power up something like even a dual core i3 Core-architecture machine successfully, fuggedaboutit.
bitrex <user@example.net> wrote:
> Each rail on those is provided by its own lil non-isolated > buck/buck-boost/inverter circuit capable of some max current per.
Are you sure? That is *very* unusual! The typical ATX supply has a single switcher for all the normal rails plus a small one for +5VSB. While it is true that you cannot re-calculate the +12V load back to the max power when you don't use the other rails at all, a typical supply has specs for the max current per rail that will be further limited by the max total power, but not by much.
On Mon, 08 Oct 2018 18:26:17 +0200, geos wrote:

> I'm looking for 200-250W ATX Pico-PSU power supply. I see on Chinese > sites that they sell such things rated at this wattage for 20-30$, for > example: > > https://www.aliexpress.com/item/DC-12V-250W-Pico-ATX-switch-PSU-24pin-
MINI-ITX-ATX-High-Power-Supply/32629921198.html? spm=a2g0s.8937460.0.0.4eb72e0ev6xyVU
> > My questions is: when looking at the components used, general design > etc. -- do you, experienced in electronics, have a feeling that such > power supply can handle 200-250W with no issues? Does such product look > reliable/reasonable to you? Or better I should not trust this bold > marketing presented there and look for something else?
I doubt the ratings. Assuming pedestrian technology at 90% efficiency, then it would need to get rid of 20 - 25 W of heat! Even assuming 95% eff. that would still produce 10 - 15 W. Does that tiny board look like it can get rid of even 15 W without a big fan blowing lots of air on it? Jon
On Mon, 08 Oct 2018 18:11:55 +0000, Rob wrote:

> bitrex <user@example.net> wrote: >> Each rail on those is provided by its own lil non-isolated >> buck/buck-boost/inverter circuit capable of some max current per. > > Are you sure? That is *very* unusual! The typical ATX supply has a > single switcher for all the normal rails plus a small one for +5VSB. >
PicoPSUs are NOT typical line-powered PC supplies. They generally run off a 12 V DC supply, so having individual converters for each output makes a lot of sense. They also do not NEED isolation, so my guess is they do NOT have isolation from the input ground. Jon
On 10/08/2018 02:33 PM, Jon Elson wrote:
> On Mon, 08 Oct 2018 18:26:17 +0200, geos wrote: > >> I'm looking for 200-250W ATX Pico-PSU power supply. I see on Chinese >> sites that they sell such things rated at this wattage for 20-30$, for >> example: >> >> https://www.aliexpress.com/item/DC-12V-250W-Pico-ATX-switch-PSU-24pin- > MINI-ITX-ATX-High-Power-Supply/32629921198.html? > spm=a2g0s.8937460.0.0.4eb72e0ev6xyVU >> >> My questions is: when looking at the components used, general design >> etc. -- do you, experienced in electronics, have a feeling that such >> power supply can handle 200-250W with no issues? Does such product look >> reliable/reasonable to you? Or better I should not trust this bold >> marketing presented there and look for something else? > > I doubt the ratings. Assuming pedestrian technology at 90% efficiency, > then it would need to get rid of 20 - 25 W of heat! Even assuming 95% > eff. that would still produce 10 - 15 W. Does that tiny board look like > it can get rid of even 15 W without a big fan blowing lots of air on it? > > Jon >
A buck converter controller that could only deliver 90% efficiency at maximum load would be a terrible choice for a design like that; the synchronous buck ICs used for the high power rails in those can likely do 96, 97% at full load. 10 watts dissipation isn't that bad if it's distributed more or less evenly across five or six MOSFET pairs on a board that size, the MOSFETs are dpaks heat sunk to the copper plane. The problem is more that a real world, modern PC load that draws evenly from all the circa 1990 ATX spec PSU rails is unlikely.
On 10/08/2018 02:51 PM, bitrex wrote:
> On 10/08/2018 02:33 PM, Jon Elson wrote: >> On Mon, 08 Oct 2018 18:26:17 +0200, geos wrote: >> >>> I'm looking for 200-250W ATX Pico-PSU power supply. I see on Chinese >>> sites that they sell such things rated at this wattage for 20-30$, for >>> example: >>> >>> https://www.aliexpress.com/item/DC-12V-250W-Pico-ATX-switch-PSU-24pin- >> MINI-ITX-ATX-High-Power-Supply/32629921198.html? >> spm=a2g0s.8937460.0.0.4eb72e0ev6xyVU >>> >>> My questions is: when looking at the components used, general design >>> etc. -- do you, experienced in electronics, have a feeling that such >>> power supply can handle 200-250W with no issues? Does such product look >>> reliable/reasonable to you? Or better I should not trust this bold >>> marketing presented there and look for something else? >> >> I doubt the ratings.&nbsp; Assuming pedestrian technology at 90% efficiency, >> then it would need to get rid of 20 - 25 W of heat!&nbsp; Even assuming 95% >> eff. that would still produce 10 - 15 W.&nbsp; Does that tiny board look like >> it can get rid of even 15 W without a big fan blowing lots of air on it? >> >> Jon >> > > A buck converter controller that could only deliver 90% efficiency at > maximum load would be a terrible choice for a design like that; the > synchronous buck ICs used for the high power rails in those can likely > do 96, 97% at full load. > > 10 watts dissipation isn't that bad if it's distributed more or less > evenly across five or six MOSFET pairs on a board that size, the MOSFETs > are dpaks heat sunk to the copper plane. > > The problem is more that a real world, modern PC load that draws evenly > from all the circa 1990 ATX spec PSU rails is unlikely.
That is to say if you put like a real desktop-class processor on a mini-itx mobo and try to power it from that it's just going to overcurrent-protect and lock out/fall down immediately when you hit the power switch. An Atom or low-power Celeron will probably be OK.