Intel fan humming when powered through resistance

OK, I don't want to help.

Please install LTspice and some form of unzipper.

Thanks for simulating, yes the frequency does change with duty cycle but stays around the 18-30kHz range so should satisfy the fan's requirements of approx 25kHz.

piglet

amdx, the name of the supply is Sunny.

I pulled a intel CPU cooler fan out of my junkbox and can confirm that if you put a resistor in series with the supply it makes a noise

Increasing the voltage let the smoke out so I cant do more experiments

I expect that's the case.

piglet, is this a fan controller or a fan spoofer?

This is an attempt to limit fan current through bipolar beta limit. The larger the base resistor, the less current supplied.

Whether a resistor or some other means is used to reduce the fan terminal voltage, you'll find fan performance much more predictable if large electrolytics are used to decouple at the fan terminals.

This allows the fan to draw pulsating current in its normal operation.

RL

John, if you mean myn power adapter name and model, it's this

amdx

No, I was asking for his name.

Another anonymous googlegrooper.

The schematic I posted shows one way to generate variable width pulses at approximately 25kHz that mimic the signals generated by a PC motherboard to control the fan speed.

piglet

My pleasure. I like your circuits. Unlike many posted here, yours always work.

You're welcome. I can draw you even more that don't work :)

piglet