Reply by bitrex October 8, 20182018-10-08
On 10/08/2018 04:19 PM, Tim Williams wrote:
> Hahahah no, not if you want dirty automotive power roasting your board. > It's probably noisy as sin, too. > > It might be okay for what it is, but a real automotive version (say like > what would power an OEM's dash computer -- given that they aren't using > ITX mobos but something custom anyway) would wrap that thing in a metal > box (with thermal pads), maybe add output current limiting, add a 12V > buck-boost (notice the 12V rail is straight through), extra filtering, > and transient and load dump protection. > > ISTR there are small mobos with a plain 12V input (or 18V or whatever), > with the converters onboard (which would be what the OEM does).� Then > you would only need to add protection circuitry. > > Tim >
I didn't notice the 12V rail is straight thru on that model, for an automotive use PSU that's mad. At least these give current ratings for the various rails. And don't list automotive in the suggested applications: <http://www.itxpower.net/en/itx120wl.htm
Reply by Tim Williams October 8, 20182018-10-08
Hahahah no, not if you want dirty automotive power roasting your board. 
It's probably noisy as sin, too.

It might be okay for what it is, but a real automotive version (say like 
what would power an OEM's dash computer -- given that they aren't using ITX 
mobos but something custom anyway) would wrap that thing in a metal box 
(with thermal pads), maybe add output current limiting, add a 12V buck-boost 
(notice the 12V rail is straight through), extra filtering, and transient 
and load dump protection.

ISTR there are small mobos with a plain 12V input (or 18V or whatever), with 
the converters onboard (which would be what the OEM does).  Then you would 
only need to add protection circuitry.

Tim

-- 
Seven Transistor Labs, LLC
Electrical Engineering Consultation and Design
Website: https://www.seventransistorlabs.com/

"geos" <geos@SPAMPRECZ.autograf.pl> wrote in message 
news:5bbb8529$0$501$65785112@news.neostrada.pl...
> I'm looking for 200-250W ATX Pico-PSU power supply. I see on Chinese sites > that they sell such things rated at this wattage for 20-30$, 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
Reply by bitrex October 8, 20182018-10-08
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$, for >>> example: >>> >>> https://www.aliexpress.com/item/DC-12V-250W-Pico-ATX-switch-PSU-24pin- >> MINI-ITX-ATX-High-Power-Supply/32629921198.html? >> spm=a2g0s.8937460.0.0.4eb72e0ev6xyVU >>> >>> My questions is: when looking at the components used, general design >>> etc. -- do you, experienced in electronics, have a feeling that such >>> power supply can handle 200-250W with no issues? Does such product look >>> reliable/reasonable to you? Or better I should not trust this bold >>> marketing presented there and look for something else? >> >> I doubt the ratings.&nbsp; Assuming pedestrian technology at 90% efficiency, >> then it would need to get rid of 20 - 25 W of heat!&nbsp; Even assuming 95% >> eff. that would still produce 10 - 15 W.&nbsp; Does that tiny board look like >> it can get rid of even 15 W without a big fan blowing lots of air on it? >> >> Jon >> > > A buck converter controller that could only deliver 90% efficiency at > maximum load would be a terrible choice for a design like that; the > synchronous buck ICs used for the high power rails in those can likely > do 96, 97% at full load. > > 10 watts dissipation isn't that bad if it's distributed more or less > evenly across five or six MOSFET pairs on a board that size, the MOSFETs > are dpaks heat sunk to the copper plane. > > The problem is more that a real world, modern PC load that draws evenly > from all the circa 1990 ATX spec PSU rails is unlikely.
That is to say if you put like a real desktop-class processor on a mini-itx mobo and try to power it from that it's just going to overcurrent-protect and lock out/fall down immediately when you hit the power switch. An Atom or low-power Celeron will probably be OK.
Reply by bitrex October 8, 20182018-10-08
On 10/08/2018 02:33 PM, Jon Elson wrote:
> On Mon, 08 Oct 2018 18:26:17 +0200, geos wrote: > >> I'm looking for 200-250W ATX Pico-PSU power supply. I see on Chinese >> sites that they sell such things rated at this wattage for 20-30$, 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.
Reply by Jon Elson October 8, 20182018-10-08
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
Reply by Jon Elson October 8, 20182018-10-08
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$, for > example: > > https://www.aliexpress.com/item/DC-12V-250W-Pico-ATX-switch-PSU-24pin-
MINI-ITX-ATX-High-Power-Supply/32629921198.html? spm=a2g0s.8937460.0.0.4eb72e0ev6xyVU
> > My questions is: when looking at the components used, general design > etc. -- do you, experienced in electronics, have a feeling that such > power supply can handle 200-250W with no issues? Does such product look > reliable/reasonable to you? Or better I should not trust this bold > marketing presented there and look for something else?
I doubt the ratings. Assuming pedestrian technology at 90% efficiency, then it would need to get rid of 20 - 25 W of heat! Even assuming 95% eff. that would still produce 10 - 15 W. Does that tiny board look like it can get rid of even 15 W without a big fan blowing lots of air on it? Jon
Reply by Rob October 8, 20182018-10-08
bitrex <user@example.net> wrote:
> Each rail on those is provided by its own lil non-isolated > buck/buck-boost/inverter circuit capable of some max current per.
Are you sure? That is *very* unusual! The typical ATX supply has a single switcher for all the normal rails plus a small one for +5VSB. While it is true that you cannot re-calculate the +12V load back to the max power when you don't use the other rails at all, a typical supply has specs for the max current per rail that will be further limited by the max total power, but not by much.
Reply by bitrex October 8, 20182018-10-08
On 10/08/2018 01:13 PM, bitrex wrote:
> On 10/08/2018 12:26 PM, geos wrote: >> I'm looking for 200-250W ATX Pico-PSU power supply. I see on Chinese >> sites that they sell such things rated at this wattage for 20-30$, 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.
Reply by bitrex October 8, 20182018-10-08
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$, for >> example: >> >> https://www.aliexpress.com/item/DC-12V-250W-Pico-ATX-switch-PSU-24pin-MINI-ITX-ATX-High-Power-Supply/32629921198.html?spm=a2g0s.8937460.0.0.4eb72e0ev6xyVU >> >> >> My questions is: when looking at the components used, general design >> etc. -- do you, experienced in electronics, have a feeling that such >> power supply can handle 200-250W with no issues? Does such product >> look reliable/reasonable to you? Or better I should not trust this >> bold marketing presented there and look for something else? >> >> I would appreciate your opinion. >> >> thank you, >> geos > > Get one that is UL or CSA rated for safeties sake. There is a lot of > badly made stuff out there. Counterfeits abound! And there are > counterfeit CSA/UL labels too I expect, but it seems much rarer as I > hope those agencies chase fake labels down. > > John :-#)# >
The ones I got off AliExpress/eBay from sellers with good reviews seem okay and do what they say on the tin, they're just not "real" 250 watt PSUs in the way a flyback or forward bridge 250 watt PSU is. Aside from the (through hole in mine) capacitors being mystery meat the manufacturing quality doesn't seem much different than your average PC motherboard you'd get from NewEgg or something. Most of the converters on the board are "Richtech" chips like this with a couple of MC34063s looks like <https://www.richtek.com/Products/PC%20System%20Buck%20Controller/RT8223N?sc_lang=en>
Reply by bitrex October 8, 20182018-10-08
On 10/08/2018 12:26 PM, geos wrote:
> I'm looking for 200-250W ATX Pico-PSU power supply. I see on Chinese > sites that they sell such things rated at this wattage for 20-30$, 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.