Electronics > Projects, Designs, and Technical Stuff
switching-PSUs: why can't you usually exceed the 50% of declared power?
bdunham7:
--- Quote from: 0db on May 23, 2020, 08:43:06 pm ---
What I cannot understand is why. Which are the technical reasons for this? And what one should look into the circuit to have some enlightenments about the quality of the product concerning its behavior under load?
Thanks
--- End quote ---
According to many internet teardown reviews, there are a lot of PSUs with shoddy build quality, even name brands. But that doesn't explain why they blow up, if indeed they do. I did some GPU BitCoin mining for a few years and of course doing that you need to do it as cheaply as possible. I had multiple rigs that used about 400W and I started with some cheapo 500W PSUs and they all failed in days or weeks. I didn't disassemble them, so IDK what killed them, but they didn't catch on fire or fry anything, they just stopped working. The helpful Microcenter guy suggested some generic 'PC Power and Cooling' 750W units and those worked for years. I still have one or two. The only two differences I'm certain of between the two PSU types are that the 500W units didn't have enough hold-up time to reliably allow my UPS to kick in, and that the larger units were significantly more efficient (as measured with a KillaWatt device) although I don't have a number offhand. It was something like 20 or 30W less at the wall.
My best guess is that cheap no-name brands will have the cheapest, smallest parts and will be optimistically rated. I suppose most people don't push the limits and if their overall warranty rate isn't too high things are good enough.
0db:
--- Quote from: chriva on May 24, 2020, 11:33:30 pm ---LTT is not the correct place to get that type of information.
--- End quote ---
Before buying I checked all the "customers reviews" on Amazon and on websites, including the eBay forum for consumers: 90% incorrect to what I personally measured.
I measured something like 15 units, of which 11 returned to Amazon.
The last three tests of yesterday
* sharkoon silentstorm coolzero 650 watt (120 euro)
* seasonic prime gold 750 watt (130 euro)
* asus rog thor 850 watt (240 euro)
The asus rog thor is really impressive! I will return it just because it's too expensive, but it's a truly great piece of technology :o
0db:
All tests concern
* the ripple under load (all rails have resistive loads)
* the operating voltages range (are ATX ranges respected?)
* the protection against overcurrent (does it turn off immediately?)
Next weekend, I will go ahead with tests on cheap PSUs in the range 50-60 euro.
I can open the metal frame to have a look, but I am not able to say a word about internal components. I don't have any scientific criteria to test the "visual" quality.
If you show me the pic of a very bad PSU, and the pic of a very good PSU, I am not able to distinguish them without putting them on the testbench, but this kind of "visual" test is very useful when you happen to buy "frameless PSUs", just the naked circuit without any metal, from China.
My next micro-business.
engrguy42:
--- Quote from: 0db on May 25, 2020, 09:59:27 am ---
--- Quote from: chriva on May 24, 2020, 11:33:30 pm ---LTT is not the correct place to get that type of information.
--- End quote ---
Before buying I checked all the "customers reviews" on Amazon and on websites, including the eBay forum for consumers: 90% incorrect to what I personally measured.
I measured something like 15 units, of which 11 returned to Amazon.
The last three tests of yesterday
* sharkoon silentstorm coolzero 650 watt (120 euro)
* seasonic prime gold 750 watt (130 euro)
* asus rog thor 850 watt (240 euro)
The asus rog thor is really impressive! I will return it just because it's too expensive, but it's a truly great piece of technology :o
--- End quote ---
So you bought 15 power supplies, ran them thru some tests including overloading them, performing tests on units you admit you don't understand, as well as the ATX specification which you don't understand (and apparently weren't aware of), and when they fail/blow up you return 11 of them?
TheUnnamedNewbie:
It's also important noting that you can't just draw all that current from one supply. If a supply says 600W, it usually means x W on the 12V CPU, y W on the 12V PCIe-additional cables, z W on the 5V/3.3V rails, etc. And in the end, x+y+z will end up adding to 600W.
A 600W supply can not provide 600W on its 3.3V line. If it could, it would come with chunky cables.
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