Can A 2-wire Fan Be Regulated By PWM?

Usually, the cooling fan needs to use a 3-wire or 4-wire control method to control the fan power supply voltage through PWM speed regulation, which includes an additional control line for receiving PWM signals. This additional control line allows the PWM signal to directly control the fan speed.
For a 2-wire fan, usually one is the positive pole of the power supply, and the other is the ground or negative pole of the power supply. Due to the lack of additional control lines to receive PWM signals, PWM speed regulation cannot be directly used. Instead, the speed can be changed by adjusting the power supply voltage. You can use a voltage regulator (such as a voltage resistor or voltage regulation module) to adjust the power supply voltage to different levels to change the turning speed of the fan.
However, this method may not be as precise and controllable as PWM speed regulation, and its results may be subject to certain limitations. If precise fan speed regulation is required, it is recommended to choose a 3-wire or 4-wire fan with PWM speed regulation function. These fans come with external control lines that can directly receive PWM signals and achieve precise speed regulation.
In addition, if you want to achieve PWM speed regulation for a 2-wire fan, you can also use some other hard components to achieve it. Here is a common method:
1. Using a microcontroller: Connect a 2-wire fan to the microcontroller, which can achieve PWM speed regulation by adjusting the smoothness and pulse width of the output pins. You can use microcontrollers with PWM output function, such as Arduino, Raspberry Pie, etc.
Connect the fan: Connect the positive pole (+) of the fan to the PWM output pin of the microcontroller, and connect the load pole (-) of the fan to the ground pin (GND) of the microcontroller.
Programming control: Use appropriate programming language and library functions, set PWM output pins on the microcontroller, and adjust the duty cycle (i.e. pulse width) to control the fan speed.
2. Using a PWM controller chip: Another method is to use a dedicated gate PWM controller chip. These chips can receive PWM inputs from microcontrollers or other controller based signal sources, and adjust the fan speed by controlling current or voltage.