PSU clicks once when turned off

[TheNaitsyrk]

I bought new PSU, switched from HX1200 to EVGA SuperNova P2 1200W.

 

There is an audible click when I turn the PC off. Is it normal? No PSU I had did this before. I read it's relays in the fan, but just wanted to confirm.

[rEkmAInc1csBnlM6C85H]

Yes it is a relay, you are fine; good ones are loud because if the action is not quick and solid they wear out faster.

[TheNaitsyrk]

4 minutes ago, Andrew 1337 said:

Yes it is a relay, you are fine; good ones are loud because if the action is not quick and solid they wear out faster.

Yea it's a bit weird to me. Never had that happen, I had RM1000, 2x HX1200i and they didn't do it. This one is same rating as HX1200i but it does the click every time I turn off.

 

You think it will go away with time? It's just super annoying having it there that's all haha

[rEkmAInc1csBnlM6C85H]

1 minute ago, TheNaitsyrk said:

Yea it's a bit weird to me. Never had that happen, I had RM1000, 2x HX1200i and they didn't do it. This one is same rating as HX1200i but it does the click every time I turn off.

 

You think it will go away with time? It's just super annoying having it there that's all haha

If it is anything like most consumer electronics relays after a couple hundred throws it will not be as pronounced, unless they used a proper commercial grade one; then we are talking thousands of throws.

[TheNaitsyrk]

5 minutes ago, Andrew 1337 said:

If it is anything like most consumer electronics relays after a couple hundred throws it will not be as pronounced, unless they used a proper commercial grade one; then we are talking thousands of throws.

Well said. Thank you very much for explaining!

[mariushm]

There's all kinds of mechanical relays, some sound more muffled than others.

 

Basically what happens inside the psu is this: a high wattage power supply has some components that suck up energy at a very high rate when you power up the unit. Basically for a few millisecond, the power supply behaves like a black hole sucking up "juice" from the mains. 

This can cause your mains fuse to trip, you have 16-20A fuses for your outlets but the power supply has this burst of up to 80-100A of currents for that very small time.

 

So to counteract this, manufacturers of power supplies place a component on the input of the power supply called NTC thermistor (negative temperature coefficient) , which is designed to restrict the flow of electricity when it's cold, and lets more energy as it warms up (from the electricity flowing through it).  So when the psu is turned on, that component is cold and restricts the electricity to let's say 10% of maximum possible ... and right away it starts warming up and it gradually goes up to near 100%... this happens within seconds.

 

However, no matter how well the component is chosen, it will still restrict some (let's say less than 5%) and will be hot and basically consume something like 1 watt of electricity constantly and this can make the power supply not pass Platinum or Titanium ratings (where psu must be over 94% efficient or something like that)

 

So a few seconds after the psu starts, a relay is turned on and the relay connects a wire between the terminals of this component, basically removing it from the circuit.

That's your click, the relay engaging in the power supply.

 

Some power supplies may not even click at all when you shut down the PC. A lot of power supplies don't have latching relays (latching= like the button on a ball point pen) - as soon as there's no more energy sent to the relay, it "relaxes" and disconnects and the disconnect is often silent. With latching relays, you don't have to keep the relay energized once it's set to a position, but ou do have to actually send a pulse to turn off the relay and put that component back in the circuit.

 

[TheNaitsyrk]

3 minutes ago, mariushm said:

There's all kinds of mechanical relays, some sound more muffled than others.

 

Basically what happens inside the psu is this: a high wattage power supply has some components that suck up energy at a very high rate when you power up the unit. Basically for a few millisecond, the power supply behaves like a black hole sucking up "juice" from the mains. 

This can cause your mains fuse to trip, you have 16-20A fuses for your outlets but the power supply has this burst of up to 80-100A of currents for that very small time.

 

So to counteract this, manufacturers of power supplies place a component on the input of the power supply called NTC thermistor (negative temperature coefficient) , which is designed to restrict the flow of electricity when it's cold, and lets more energy as it warms up.  So when the psu is turned on, that component is cold and restricts the electricity to let's say 10% ... and right away it starts warming up and it gradually goes up to near 100%.

However, no matter how well it's chosen, it will still restrict some (let's say less than 5% and will be hot and basically consume something like 1 watt of electricity) and this can make the power supply not pass Platinum or Titanium ratings (where psu must be over 94% efficient or something like that)

 

So a few seconds after the psu starts, a relay is turned on and the relay connects a wire between the terminals of this component, basically removing it from the circuit.

That's your click, the relay engaging in the power supply.

 

Some power supplies may not even click at all when you shut down the PC. A lot of power supplies don't have latching relays (latching= like the button on a ball point pen) - as soon as there's no more energy sent to the relay, it "relaxes" and disconnects and the disconnect is often silent. With latching relays, you don't have to keep the relay energized once it's set to a position, but ou do have to actually send a pulse to turn off the relay and put that component back in the circuit.

 

Thank you!