Introduction

In today’s electronics, air moving fans provide a critical service in that they cool the system power electronics. However, just running the fan at full speed has a disadvantage in that it can produce significant audio noise. Therefore, most modern systems regulate the speed of the fan so they can balance the requirements of cooling and noise abatement.

Given that the fan speed is also significantly affected by restrictions on the airflow, both into (dirty air filter) and out of (blocked outlet ports) the fan, some form of fan speed regulation is typically needed to maintain consistent cooling. This application note will cover a relatively simple, low-cost solution for managing the fan speed, using a software-based Proportional Integral Differential (PID) fan speed control.