| Electronics > Projects, Designs, and Technical Stuff |
| switching-PSUs: why can't you usually exceed the 50% of declared power? |
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| 0db:
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 |
| wraper:
Unless you buy cheapest garbage usually you can run them at 100% or nearly 100% load for prolonged time. --- Quote ---What I cannot understand is why. Which are the technical reasons for this? --- End quote --- Really, is it that hard to figure it out? It's cheaper to build lower quality PSU with fake ratings. More power/ higher efficiency = more expensive to produce. |
| 0db:
--- Quote from: wraper on May 23, 2020, 08:50:54 pm ---Really, is it that hard to figure it out? --- End quote --- I'd like to know details: is it for capacitors? if so, which is the difference between "good" capacitors and "bad" capacitors? And is there any table around telling which are good ones (vendor/models/etc)? Is it for the transformer? Filters? Protection chip? Oscillators? What does make a PSU a "bad" PSU? It's too easy to say "oh, because it's cheap". Cheap means all and nothing. |
| ejeffrey:
Not enough capacitance, not enough core material, not enough copper, not enough silicon, and not enough cooling. Too low temperature ratings and too much ripple current. Even if the PSU is designed correctly, if parts are substituted at manufacturer time that can cause any of the above issues. There are lots of ways to cheap out, not just one. |
| engrguy42:
--- 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 --- Where did you see this? Do you have an example of an ATX that can't operate over 50%? Are you sure you're not talking about efficiency dropping above 50% or something like that? |
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