Loud click when shuting down : PSU protection?

[electropical]

Hi,
When the computer is shutting down (I turn off the computer using Start>Power>Shut down), a somewhat loud click can be heard (loud enough for me not to be able to locate the origin of the sound) ;
At first, I felt like it was the power supply that was making the sound (Inrush Current Protection?), but now I'm wondering if that's not some other component that's doing it ;
Other than that, the PSU (RM750x) is working fine (at start the fan starts spinning and then stops after a while (passive mode), doesn't make a sound), nothing to complain about.

Any thoughts on what could be causing that click?

[manikyath]

is it *while* shutting down, or is it the absolutely last thing the computer does before going completely dark?

if it's the last thing, i assume that it's a relay clicking off.

[skimmilk5]

That is normal. Your PSU has a lot of intricate electronics that operate at much lower voltages, while other components operate at 120VAC, 12VDC, 5VDC, and 3.3VDC. So, power supply manufacturers often put something called a relay in their unit, which uses a series of electromagnets to open and close a switch using electricity. You can think of it like a messenger that's delivering a message saying "turn on" or "turn off". When a relay is actuated, you can hear a small "click" come from the unit (unless the unit uses a solid-state relay, which are much more expensive, so they're not typically found in PC power supplies).

 

You probably don't need to worry about the click.

[mariushm]

The power supply has a mechanical relay which is turned on a  few seconds after power supply starts and disconnects after shut down. 

 

When you start the power supply, it wants to "suck" up a lot of energy and fill up its internal capacitors, so that while your computer runs, if there's fluctuations in the power quality, the power supply can use those reserves.  The problem is the power supply sucks so much energy so fast your electrical panel may think it's a faulty device which could damage the wires in your house and normally the breaker fuses would trip to protect the house wiring. 

 

To avoid that,  there's a component in the power supply which has the role to act as a break, to slow down the start up of the power supply, because otherwise your mains fuses could blow up.  Once the power supply charges up with energy, after around a few seconds, this "break" is no longer needed so it's removed from circuit to increase the power supply efficiency and reduce the amount of heat produced by the power supply.

A mechanical relay is used to do that..  when the power supply is turned off, in turn that mechanical relay is turned off so that the psu's "break" is ready for the next startup. 

 

[electropical]

@manikyath @kimsejin5 @mariushm Thanks a lot guys !
 

1 hour ago, manikyath said:

is it *while* shutting down, or is it the absolutely last thing the computer does before going completely dark?

if it's the last thing, i assume that it's a relay clicking off.

Yes, the very last thing ;

--------------------------------

I think you guys solved it for me, thanks again !

[Guest]

1 hour ago, electropical said:

Hi,
When the computer is shutting down (I turn off the computer using Start>Power>Shut down), a somewhat loud click can be heard (loud enough for me not to be able to locate the origin of the sound) ;
At first, I felt like it was the power supply that was making the sound (Inrush Current Protection?), but now I'm wondering if that's not some other component that's doing it ;
Other than that, the PSU (RM750x) is working fine (at start the fan starts spinning and then stops after a while (passive mode), doesn't make a sound), nothing to complain about.

Any thoughts on what could be causing that click?

It's a relay.

 

[electropical]

8 minutes ago, jonnyGURU said:

It's a relay.

Thank you very much, Sir !