The diodes and transistors in the cooling fan are circuit components used to control and regulate the fan, and their roles are as follows:

Diode: A diode is an electronic component. In the circuit of the cooling fan, the diode is usually used in the bridge rectifier circuit. When the AC signal is input, the diode converts it into a DC signal for use by the DC fan. By using diodes for rectification, you can ensure that the fan motor will work properly and that the power transfer is more efficient.

Triode: A triode is a commonly used semiconductor device. In cooling fans, triodes are usually used to control the speed of the fan or to regulate the voltage of the fan. By changing the working state of the transistor, the speed of the fan can be adjusted, so as to control the air volume and noise level of the fan.

All in all, the diodes and transistors in the cooling fan play a key role in the circuit. The diode is used to rectify the current and ensure the normal operation of the fan and motor; The triode is used to control the fan speed, regulate the voltage and provide protection, so as to achieve the control and safe operation of the fan.