CPU Smart FAN Mode - voltage vs pwm at Gigabyte board

[MOROZAW]

Hello, I am looking technical information how "voltage" mode works?
Somewhere I read in this option the 12V supply voltage connected to fan is in switching mode - PWM.
Is it true?

I mean when voltage option (for 3 pin fan) is checked, the fan is supplied with 12V PWM (without filtration to DC) instead of clear linear DC voltage.

In "PWM mode" (for 4 pin fan) voltage ofc is clear DC 12V (at "red" wire) and speed is varied by duty cycle of PWM 5V signal (at "blue" wire).

I found somewhere information that, in "voltage mode" (for 3 pin fan) voltage at "red wire" is not clear voltage mode, but avg from 0-12V PWM voltage.
I mean in "voltage mode" fan is supplied with short spikes (PWM) of 12V voltage, and avg voltage is 12V * Duty cycle of this PWM.

Unfortunately I can't find a source of this measurements - I found only post on other forum about this, so I would like to ask Yours opinion.
Maybe someone could check this at oscilloscope?

Cheers!

 

[trents]

I could be wrong but my understanding is that when fans are controlled by "voltage mode" the motherboard just varies the voltage but the current flow is constant. With PWM fan speed control, on the other hand, the voltage is constant but the frequency and/or the duration of the electrical pulses varies. PWM is the better technology because it allows for lower RPMs without stalling the fan. In some situations, however, PWM control creates noise that is annoying. Not sure if this is addressing your question.

 

[NiHaoMike]

Voltage control uses a buck converter to adjust the voltage. Adjustment range is limited. PWM provides better control but only works with PWM fans and controllers.