Types of cooling fans: 2-Pin, 3-Pin, 4-Pin

There are many classification methods for cooling fans, including DC and AC, brush and brushless cooling fan, sleeve bearing and ball bearing cooling fan. We are mainly talking about the power line connectors of cooling fans, which can be divided into 2-pin, 3-pin, and 4-pin.

2-Pin fan: simple structure, but can't measure speed

Generally, if there are only 2-pin in the fan interface, there are only two red and black power cables. The structure of this fan is very simple, one is used for power supply and the other is used for grounding. The structure is simple, but it has few functions and cannot measure the speed. If you want to adjust the speed, you need to use other schemes.

3-Pin fan: VC voltage speed measurement and speed regulation, poor flexibility

As the name suggests, a 3-pin fan has one more wire than a 2-pin fan. When the temperature is not high, reducing the fan speed can bring lower noise, while the 2-pin fan can not adjust the speed, so it can not meet the customer's demand for silence, so there is a 3-pin fan interface that can adjust the speed.

The 3-pin fan wire adds a yellow line (some of which are black-yellow-green) to the original red-black wires, which is mainly responsible for speed measurement. Through it, the motherboard can detect the current state of the fan, whether it is rotating or not, and how much the speed is. However, the speed regulation of the 3-pin fan is realized by adjusting the fan voltage. The temperature detection comes from the motherboard, which can not reflect the CPU status information in real time. Besides, the motherboard BIOS is required to set various parameters, so whether the speed can be adjusted depends on the motherboard support or not.

More importantly, different fans have different starting voltages, and the voltage speed regulation is not linear. Controlling the speed by voltage may lead to problems such as not reaching the required starting voltage of the fan at low voltage and stalling of the fan.

4-Pin fan: more flexible and intelligent speed regulation

4-pin fan, that is, a PWM line (pulse width modulation) is added on the basis of 3-pin. The wire color of 4-pin fan is not fixed (common blue and purple). The extra PWM line is to use PWM mechanism to adjust the fan speed, and the fan voltage is constant, which better avoids a series of disadvantages of controlling the voltage to change speed.

In addition, the PWM pulse signal can output different Duty Cycles, and the duty cycle between 0-100% can adjust different fan speeds, so that accurate and flexible control can be achieved, and the PWM fan can be independent of the motherboard BIOS, which is convenient to use.

In PWM speed regulation, it is also divided into low-frequency PWM and high-frequency PWM. The measurement speed of low-frequency PWM has a wider range, but there will be fan commutation noise. In contrast, the overall performance of high-frequency PWM will be better.

Of course, there are still some old motherboards whose 4-pin connectors do not support PWM, so even if the high rpm exhaust fan is controlled by 4-pin PWM, it can not realize intelligent speed control. These old motherboards can only control the speed by adjusting the voltage.