For the computer cooling fan , there is a rated voltage, but in practice, it cannot be fully guaranteed to work at the rated voltage, which is a range near the rated voltage and is generally required to be within 15 %. When the voltage is higher than + 15 %, it is " overvoltage" and the user needs to be reminded to quickly cut off the power supply of the computer cooling fan, otherwise, long-term overvoltage power supply will cause damage to electronic components in the computer cooling fan, especially the motor. However, at present, the computer cooling fan control circuit on the market does not provide a simple and reliable overvoltage protection circuit to protect the computer cooling fan.How to realize the automatic overvoltage protection of the computer cooling fan is a problem that needs to be solved at present.

          The overvoltage protection circuit for the computer cooling fan comprises a fan power supply, a switch SL, a relay JL, a transistor TL, a light emitting diode DL, and a protection diode D2. The positive pole of the fan power supply is connected in series with the switch sl, which is respectively connected with the positive pole of the light emitting diode dl, one end of the relay JL coil and the negative pole of the protection diode D2, the negative pole of the light emitting diode dl is connected with the negative pole of the fan power supply through the resistor rl, the negative pole of the light emitting diode dl is also connected with the base of the transistor TL through the resistor R2, a capacitor cl is connected in parallel between the positive pole and the negative pole of the light emitting diode dl, the collector of the transistor TL is connected with the other end of the relay JL coil and the positive pole of the protection diode D2, the emitter of the transistor TL is connected with the negative pole of the fan power supply, and the relay D2 is also connected in series

          When the power supply voltage for the fan of the computer cooling fan is too high, the protection of the computer cooling fan can be realized by controlling the relay to disconnect the power supply loop, the circuit is simple, the cost is low, and the computer cooling fan has a good application prospect.