| Electronics > Projects, Designs, and Technical Stuff |
| switching-PSUs: why can't you usually exceed the 50% of declared power? |
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| 0db:
--- Quote from: engrguy42 on May 23, 2020, 11:52:05 pm ---You're really worried about it taking 1 second to trip? --- End quote --- I am more worried about the AEROCOOL VX PLUS 550W, because it didn't even shutdown; at 250Watt of load it made smoke until it exploded, and at this point the lifesaver in my appartment interrupted the energy, but before it happened, the measured p-p ripple was over 300mV on the 12V line, and this for sure can damage things like harddrives and VRMs. The Superflower Leadex costs 120 euro. As soon as I tried to connect a 650 Watt load it immediately cut of the power, and during all the tests the p-p ripple over the 12V line was a flat line, always about 30mV! - Fast OVP! - flat line p-p ripple! - fair rating on the the label It's a true 650Watt PSU! Now you have two examples. One very bad PSU, one very good PSU. |
| wizard69:
Scam artist and ethics problems from manufactures in China. If you are going to buy hardware form China you need to know the ins and outs of the industry and who the reliable manufactures are. Obviously there are a lot of good manufactures in China but there are also many that are nothing but scam artist out to make a quick buck. The big problem for the rest of us is separating the ethical manufactures from the dealers in Junk. There is also no legal structure in China that effectively polices the manufactures there. There has to be a massive public outrage for the Chinese government to take action. Look up the problems they recently had with vaccines for Children. --- Quote from: 0db on May 23, 2020, 08:43:06 pm ---The Superflower Leadex is a great series of Switching-Mode PSUs, and if you buy a 650 Watt unit, you can be sure the unit will serve you up to 650 Watt without dropping voltage, or increasing the voltage ripple. But let's talk about cheaper PSUs. I have recently seen a lot of 500 Watt units where you cannot exceed th 50% of the declared power, thereore if you buy a 500 Watt, it will serve you only up to 250 Watt, and beyound it might get damaged. 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 --- |
| tautech:
You cannot assess a PSU with light bulb loads OR its capability if loading only one rail ! Each output can only be loaded to its rated output and several output loads may be necessary to reach its full rated output in watts.....but specs may be only in watts consumption NOT total output. Further, tungsten bulbs have high initial current draw until the filament reaches operating temp where its resistance is much lower higher than when cold. This inrush current could send the SMPS into shutdown. All ^^^ traps for the unwary ! Edit to correct brain fart. |O |
| rsjsouza:
--- Quote from: tautech on May 24, 2020, 01:55:10 am ---You cannot assess a PSU with light bulb loads OR its capability if loading only one rail ! --- End quote --- 100% agree, but an exploding power supply is totally unacceptable. So, the lightbulbs are not necessarily useles as you can still separate the wheat from the chaff. |
| engrguy42:
I know folks just LOVE to make sweeping generalizations and dismissals about stuff, but usually they are incorrect. Anyway, as I said, decent power supplies don't blow up, for many reasons. Look at the ATX requirements. And realize those are MINIMUMS. Decent manufacturers add to those to make sure they don't provide crap and thereby ruin their reputations. Nobody here knows why your power supplies failed. Nor can we since we don't know the internals of the power supplies or what you did to test them and so on. If you want to believe that all power supplies that aren't the Superflower are junk, and can't be loaded past 50%, go right ahead. If you want to believe that if it was manufactured in China it's probably junk, go ahead. You'll get a lot of fanboys here agreeing. And you'll certainly get a lot of anti-ATX fanboys agreeing with anything that anyone says that's negative towards ATX supplies. You'll even get people saying they're bad because a bug can crawl in and zap it. But if you're interested in the truth, do some research. Look inside the failed power supplies and see what happened. And see what the supervisor circuit is, and what it's designed for. Without that it's all just vague speculation about stuff nobody understands. |
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