How does power supply fan control work?

[crazyfrog]

How do PC power supplies control there fan speed like the corsair RM series? Is there just a basic switch or are thermistors and a digital circuit involved?

I've added a thermal switch to 3d printer power supplies before specifically a 'KSD9700 50 degree normally open'. The mod is really easy but involves draining the capacitors for electrical safety. The result of the mod was a perfectly silent printer when printing with a fan occasionally kicking in which is great for my ears and excellent for fan bearings.

 

PS I know talking about modding power supplies isn't ideal and receiving a shock from a charged power supply could be fatal so please dont fill the thread with condescending comments about electrical safety.

[LIGISTX]

19 minutes ago, crazyfrog said:

How do PC power supplies control there fan speed like the corsair RM series? Is there just a basic switch or are thermistors and a digital circuit involved?

I've added a thermal switch to 3d printer power supplies before specifically a 'KSD9700 50 degree normally open'. The mod is really easy but involves draining the capacitors for electrical safety. The result of the mod was a perfectly silent printer when printing with a fan occasionally kicking in which is great for my ears and excellent for fan bearings.

 

PS I know talking about modding power supplies isn't ideal and receiving a shock from a charged power supply could be fatal so please dont fill the thread with condescending comments about electrical safety.

I am not entirely sure how they are controlled, but if its an RM PSU, the fan won't kick on until its under load.... my RM850x is rarely on, only while I am gaming. I used to run a RM650i, still do in my server, and that you can control via software.

 

Why are you looking to control the fan seeing as its already silent while not being loaded?

[Guest]

16 minutes ago, crazyfrog said:

How do PC power supplies control there fan speed like the corsair RM series? Is there just a basic switch or are thermistors and a digital circuit involved?

I've added a thermal switch to 3d printer power supplies before specifically a 'KSD9700 50 degree normally open'. The mod is really easy but involves draining the capacitors for electrical safety. The result of the mod was a perfectly silent printer when printing with a fan occasionally kicking in which is great for my ears and excellent for fan bearings.

It depends on the PSU.

 

Many of them just use a thermistor.  But some PSUs, like the RM, use an MCU because the fan is controlled by temperature, load and then there's a hysteresis to prevent the fan from twitching off and on if it's on the precipice of turning on.

 

I don't recommend modding a PSU fan.  Not because you're going to shock yourself.    But because they already have a fan curve that's tailored to keep the components cool.  

 

If you slow down your CPU or GPU, what happens?  They throttle.  Or your PC crashes.  You slow down your PSU fan and it's not going to "throttle".  If you're lucky, OTP is sensitive enough to shut the PSU down.  But worst case is that your MOSFETs suffer thermal runaway and explode or worse, your transformer overheats and everything dies.

[crazyfrog]

3 minutes ago, jonnyGURU said:

It depends on the PSU.

 

Many of them just use a thermistor.  But some PSUs, like the RM, use an MCU because the fan is controlled by temperature, load and then there's a hysteresis to prevent the fan from twitching off and on if it's on the precipice of turning on.

 

I don't recommend modding a PSU fan.  Not because you're going to shock yourself.    But because they already have a fan curve that's tailored to keep the components cool.  

 

If you slow down your CPU or GPU, what happens?  They throttle.  Or your PC crashes.  You slow down your PSU fan and it's not going to "throttle".  If you're lucky, OTP is sensitive enough to shut the PSU down.  But worst case is that your MOSFETs suffer thermal runaway and explode or worse, your transformer overheats and everything dies.

The power supply in question is a delta dps-250ab-18 it’s about 52db and runs a i5 3470 with a SSD no other hardware.  I’m intending on putting the switch close the transformer using silicone glue.
 

I always look at Corsair as well made power supplies, can’t say I’ve ever had issues.

[Bitter]

As JG said, but you could change to a quieter fan or alter the grill on the case to install a wire grill for less noise.

[Bombastinator]

-deleted-  double post. 

[Bombastinator]

43 minutes ago, crazyfrog said:

The power supply in question is a delta dps-250ab-18 it’s about 52db and runs a i5 3470 with a SSD no other hardware.  I’m intending on putting the switch close the transformer using silicone glue.
 

I always look at Corsair as well made power supplies, can’t say I’ve ever had issues.

As a rule messing with the insides of PSUs is considered a bad idea.  There are some really big capacitors in there that are large enough to kill.  One needs to be really sure they are drained of electricity and harmless, or one can fry oneself with an errant tool or simply by touching the wrong thing.

 

This thread makes me wonder if there is a photo somewhere of a screwdriver sticking straight out the top of an opened PSU after it was inadvertently and spontaneously arc welded in place.

[Guest]

42 minutes ago, crazyfrog said:

The power supply in question is a delta dps-250ab-18 it’s about 52db and runs a i5 3470 with a SSD no other hardware.  I’m intending on putting the switch close the transformer using silicone glue.
 

I always look at Corsair as well made power supplies, can’t say I’ve ever had issues.

The transformer typically isn't the hottest component.  It's typically the bridge rectifier, especially at lower mains voltages, or the PFC MOSFETs.  You might want to put some thermistors on the BD, PFC FETs, PWM FETs, T1 and the SR to make sure none of them exceed 100°C.

 

 

 

[crazyfrog]

 

18 hours ago, Bombastinator said:

As a rule messing with the insides of PSUs is considered a bad idea.  There are some really big capacitors in there that are large enough to kill.  One needs to be really sure they are drained of electricity and harmless, or one can fry oneself with an errant tool or simply by touching the wrong thing.

 

This thread makes me wonder if there is a photo somewhere of a screwdriver sticking straight out the top of an opened PSU after it was inadvertently and spontaneously arc welded in place.

Condescending

 

18 hours ago, jonnyGURU said:

The transformer typically isn't the hottest component.  It's typically the bridge rectifier, especially at lower mains voltages, or the PFC MOSFETs.  You might want to put some thermistors on the BD, PFC FETs, PWM FETs, T1 and the SR to make sure none of them exceed 100°C.

 

 

 

My thinking was using a 45C temperature switch near a known hot component would be a safe bet.

 

[Guest]

1 hour ago, crazyfrog said:

 

Condescending

 

My thinking was using a 45C temperature switch near a known hot component would be a safe bet.

 

So the fan really doesn't ramp up with temperature already?  It's just always on, always max temperature?

 

Yeah.  You should be safe with having the fan off as long as the BD1 temperature doesn't exceed 80°C.

 

[Bombastinator]

4 hours ago, crazyfrog said:

 

Condescending

 

My thinking was using a 45C temperature switch near a known hot component would be a safe bet.

 

Nope.  I’d take cowardly though.  The insides of PSUs scare me.  PSUs are not ATX on the inside.  The box as a whole has to comply with a standard but the inside doesn’t.  The whole “how dare you warn me.  Do you think I would do something so foolish?” Nope I got no idea who you are.  For all I know you’re a 13 year old who doesn’t know what they don’t know.  You might not be.  In which case you know to do make the thing safe already.  Many don’t.   The thing implied by that word has its own issues.  Do as you will.  I couldn’t stop you anyway.

[Bitter]

4 hours ago, jonnyGURU said:

So the fan really doesn't ramp up with temperature already?  It's just always on, always max temperature?

 

Yeah.  You should be safe with having the fan off as long as the BD1 temperature doesn't exceed 80°C.

 

I've had a few like that and have one like that currently in my mining PC. Not sure of it's max speed but it's the loudest thing in the box lol and doesn't change speed at idle or at 300W on it. 

[Guest]

2 hours ago, Bitter said:

I've had a few like that and have one like that currently in my mining PC. Not sure of it's max speed but it's the loudest thing in the box lol and doesn't change speed at idle or at 300W on it. 

What makes a mining PSU a mining PSU is that the fan spins at 100% RPM 100% of the time so they can sell 850W PSUs as 1500W PSUs.

 

[Bitter]

9 hours ago, jonnyGURU said:

What makes a mining PSU a mining PSU is that the fan spins at 100% RPM 100% of the time so they can sell 850W PSUs as 1500W PSUs.

 

It's not a mining PSU, it's just not a very good PSU. It's 'good enough' to run at 1/2 it's capacity for a few years without catching fire...maybe. It's in the basement on cement in a metal box so risk is minimized. I'd be more angry about it killing hardware, if I keep mining I'll probably replace it with something like a SuperFlower Leadex3 next time one is on sale since they seem to be decent units at a decent price where as this Apevia is more like a Little Caesars Hot n Ready pizza, it was inexpensive and readily available when I needed one quickly.

https://www.amazon.com/gp/product/B07NWZQX1J/

[crazyfrog]

On 10/23/2021 at 2:39 AM, Bombastinator said:

Nope.  I’d take cowardly though.  The insides of PSUs scare me.  PSUs are not ATX on the inside.  The box as a whole has to comply with a standard but the inside doesn’t.  The whole “how dare you warn me.  Do you think I would do something so foolish?” Nope I got no idea who you are.  For all I know you’re a 13 year old who doesn’t know what they don’t know.  You might not be.  In which case you know to do make the thing safe already.  Many don’t.   The thing implied by that word has its own issues.  Do as you will.  I couldn’t stop you anyway.

I haven’t called anyone and wouldn’t call anyone cowardly. Hope you’re done ranting.

 

On 10/23/2021 at 5:58 AM, jonnyGURU said:

What makes a mining PSU a mining PSU is that the fan spins at 100% RPM 100% of the time so they can sell 850W PSUs as 1500W PSUs.

 

That’s hilarious but I’ve had a few older OCZ power supplies where the fan control system has failed all together and that’s what they do 100% speed.

[Bombastinator]

1 hour ago, crazyfrog said:

I haven’t called anyone and wouldn’t call anyone cowardly. Hope you’re done ranting.

 

That’s hilarious but I’ve had a few older OCZ power supplies where the fan control system has failed all together and that’s what they do 100% speed.

You do seem to do a lot of judgement passing on my behavior. “Condescending” “ranting”.  I am getting that you don’t like the concept that opening a PSU can be dangerous so you are dismissing it, and by extension me.  I am a bit worried that you are dismissing me and by extension it.  I am merely attempting to exhort caution.  Dismissing me I can deal with.  Dismissing it can be reasonable if one is already being careful. 

[crazyfrog]

4 hours ago, Bombastinator said:

You do seem to do a lot of judgement passing on my behavior. “Condescending” “ranting”.  I am getting that you don’t like the concept that opening a PSU can be dangerous so you are dismissing it, and by extension me.  I am a bit worried that you are dismissing me and by extension it.  I am merely attempting to exhort caution.  Dismissing me I can deal with.  Dismissing it can be reasonable if one is already being careful. 

Thanks for another post about things you don't understand.

[Guest]

6 hours ago, crazyfrog said:

I haven’t called anyone and wouldn’t call anyone cowardly. Hope you’re done ranting.

 

That’s hilarious but I’ve had a few older OCZ power supplies where the fan control system has failed all together and that’s what they do 100% speed.

That's good. 

 

If the fan controller fails, you would rather the fan stopped working altogether as opposed to going full speed?

 

If the fan speed goes 100% when the controller fails, that does two things:  

 

1.  Keeps the PSU cool regardless of operating condition

2.  Alerts the user that there is a failure.

 

[Bombastinator]

6 hours ago, crazyfrog said:

Thanks for another post about things you don't understand.

I see no other way to take that other than the “dismissing me” choice. Do you mean I don’t understand how the innards of a PSU go together?  I can agree with that.  I do know a little bit about capacitors though.  I know they can dump all the electricity they contain very very quickly.  I know that the bigger they are the more expensive they are, so they generally don’t use large ones unless they actually need them.  Also the bigger they are the more juice they can hold and inside a PSU there can be capacitors the size of tomato paste cans.  I’ve seen a full capacitor the size of my thumb knuckle knock a dude over flat. The ones in PSUs can be a lot bigger. If they don’t have juice in them they’re not more dangerous than an empty can though.  They also don’t hold a charge indefinitely.  I don’t know how fast they drain.  Depends a lot on specifics I understand can be as little as seconds. Can be longer.  I don’t know how long.