What is the fan control mechanism for SPS with cooling fan?

Cooling fans have a relatively shorter lifetime (typical MTTF, Mean Time To Failure, of around 5000-10000 hours) as compared with other components of power supplies. As a result, changing operating method of cooling fans can extend the operation hours of the fans. The most common control methods are shown below:

1. Temperature control: if the internal temperature of a power supply detected by a temperature sensor is over the set threshold, the fan will start working at full speed, whereas, if the internal temperature is less than the set threshold, the fan will stop working or at half speed. In addition, cooling fans in some power supplies are controlled by a linear control method whereby fan speed can be changed with different internal temperatures synchronously.
2. Load control: if the loading of a power supply is over the set threshold, the fan will start working at fullspeed, whereas, if the loading is less than the set threshold, the fan will stop working or at half speed.