Deciding between PWM and DC case fans can be confusing, but it’s important for the optimal performance of your computer.
In general, PWM fans are quieter, more controllable, and more durable than DC fans. However, if you have a limited budget or are building a PC where constant fan speeds are necessary, DC fans work just as well as PWM fans. We’ll explain what all that means, and the key differences between the two fan types below.
A DC fan is a computer fan that is operated with direct current from the PC power supply or via your motherboard. This type of fan uses a three-pin connector with a supply pin as well as a ground pin and a signal output.
The first two pins supply power, while the signal output reads information about the speed of the fan blades (it’s often referred to as the tachometer pin). This allows your PC to monitor fan speeds and warn you when a fan stops running.
DC fans can run either at a constant speed or at a changing speed. The motherboard takes over the control. At lower speeds, the motherboard sends less voltage to the fan. The typical voltage for DC fans is 12 volts, but there are also models with voltages ranging from 5 to 48 volts.
A PWM fan is essentially a DC fan with an additional pin, but one that fundamentally changes the way the fan works. This fourth pin transmits what is known as a pulse width modulation (PWM) signal, which switches the fan on and off quickly.
While DC fans use different currents to control the fan speeds, PWM models only use a constant voltage, usually 12 volts. To control the speed of the fan, the PWM signal turns the fan on and off several thousand times per second. This may not sound efficient. However, PWM fans offer much more precise control over the exact speed of the fan.
As mentioned above, both DC and PWM fans can vary their speed. However, a PWM fan can be controlled more precisely.
PWM vs. DC case fans
Significant differences between the two types of fans lie less in their performance than in their mode of operation: DC fans have a minimum speed. If the voltage is too low, this type of fan can stall. With PWM fans, on the other hand, the voltage remains constant because PWM directly controls the fan motor. Here you don’t need to worry about a stop.
This also means that PWM fans can generally spin slower than their DC counterparts. If a computer does not need much cooling, the slower spinning of the fans results in less noise. So overall, PWM fans are quieter than DC fans. Because they can spin down more easily, PWM fans also generally wear out less. Of course, this varies depending on the manufacturer and the application, but PWM fans usually last longer than DC variants.
Another area where the varying voltage of DC fans is problematic is the aforementioned noise levels. DC fans operating at less than their normal voltage of 12 volts produce electrical noise. If you use your computer for audio production, this noise can be a big problem.
So which type of fan is better? Despite the clear advantages of PWM fans, DC fans are included in most pre-built PCs. Even cases with integrated fans usually use DC fans instead of PWM. This is mainly due to cost, as DC fans are cheaper. However, DC fans are not just the cheaper option. If you are building a PC that has a regular workload, constant speed DC fans provide sufficient cooling performance as well as a relatively long life.
For those seeking as much control over the PC as possible, PWM is generally the way to go. Although you have to invest a little more, you save in the long run thanks to the long life of PWM fans. They are also the better choice for quiet PC configurations.
Nevertheless, you can only use the respective fan type if your PC’s motherboard offers the appropriate connections. Therefore, always keep an eye on your motherboard’s connections to make sure you buy the right fan for your computer.