Inside be quiet!

23.05.2019
What is „PWM“?

The purpose of fans should be quite obvious: Their perpetual rotation keep the air in motion - which moves cool air to an object or hot air away from one. But what is a “PWM fan”? And what does it do differently than its “non-PWM” sibling?

“PWM” stems from electrical engineering and is short for “pulse width modulation”, which is also known as “pulse-duration modulation”. What it means is that you can use it to almost freely control the RPM of a fan. Regular fans work binary – either with full power or no power at all. PWM on the other hand lets it rotate faster or slower, depending on the situation. How does it work?
Simply put works by continually switching the power on and off, which in conjunction with the mass inertia of the fan’s motor makes it rotate faster or slower – depending on how long and frequent the “ON” phases of the power are. If they are rare then the fan will rotate slowly, and if they are frequent then it will spin fast. But the thing is: The fans have to be able to deal with the constant fluctuation! This means they have to be more complex inside, which of course makes them more expensive than their simpler counterparts. From the outside on the other hand you will be hard-pressed to find a difference – with the main exception of the connector: Regular fans have three pins, the PWM colleagues feature one more for the fan control. Which of course means that the motherboard, where these pins are connected to, must support them. Which can only cause problems on older models as PWM support has been standard in modern systems for quite some time now.


PWM fans can be used everywhere: For cooling the CPU and the case, or on top of a radiator. The control can be handled by using bespoke tools in the operating system or the BIOS/UEFI – or by using the switches on top of our cases. If you don’t care about manual control you can also let the system take care of itself – modern motherboards work within safe specifications which will cool your computer reliably at all times.