Low-end PSUs always dissipate the max rated power?

  • Thread starter Thread starter Grumble
  • Start date Start date
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Grumble

Hello everyone,

I'm rather confused over something I was told today.

Low-end PC power supply units always dissipate whatever power they are
rated for, e.g. a 400W PSU will always dissipate 400W whether the system
is idle or not. If the system does not need the power, then that power
is dissipated as heat (?!?). That would make the power saving features
on modern CPUs almost moot, no?

Is it true? Are PSUs, even cheap ones, able to provide whatever power is
needed up to the limit, or do they always crank out the max?
 
Hello everyone,

I'm rather confused over something I was told today.

Low-end PC power supply units always dissipate whatever power they are
rated for, e.g. a 400W PSU will always dissipate 400W whether the system
is idle or not. If the system does not need the power, then that power
is dissipated as heat (?!?). That would make the power saving features
on modern CPUs almost moot, no?

Is it true? Are PSUs, even cheap ones, able to provide whatever power is
needed up to the limit, or do they always crank out the max?
Click to expand...

What nitwit told you that? A salesdroid at Best-Buy?
 
Grumble said:
I'm rather confused over something I was told today.

Low-end PC power supply units always dissipate whatever
power they are rated for, e.g. a 400W PSU will always
dissipate 400W whether the system is idle or not. If
the system does not need the power, then that power
is dissipated as heat (?!?).
Click to expand...

The person who told that to you had absolutely no understanding of how
power supplies work because if it were true, then supplies would be
hottest at zero load. Try simulating this by installing lightbulbs
totalling 400W in a small ventilated metal box with a fan blowing air
through it, an it should become unbearably hot in a few minutes. Even
linear supplies, which regulate voltage by intentionally turning
unneeded power into heat (essentially like regulating the speed of the
car through the brakes), don't get hotter at lower loads. For an
explanation of how computer supplies work, try
http://computer.howstuffworks.com/power-supply.htm

Cheap and expensive computer supplies operate basically the same way,
only the cheap ones usually don't work as well (can't put out as much
power, voltages regulated worse, overload protection fails), major
exceptions being those from Fortron-Source, which are among the best
but often also among the cheapest.
 
Hello everyone,

I'm rather confused over something I was told today.

Low-end PC power supply units always dissipate whatever power they are
rated for, e.g. a 400W PSU will always dissipate 400W whether the system
is idle or not. If the system does not need the power, then that power
is dissipated as heat (?!?). That would make the power saving features
on modern CPUs almost moot, no?

Is it true? Are PSUs, even cheap ones, able to provide whatever power is
needed up to the limit, or do they always crank out the max?
Click to expand...

Don't tell us.... this guy has a tube amplifier in his home theater
system?:-)
 
dawg said:
Haven't been able to find any "cheap" Fortron PS's over 400W anywhere.
Click to expand...

They're relatively cheap, but a 350W Fortron will usually put out as
much as a typical major brand 400W.
 
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