An air-breathing fuel cell was investigated as an alternate power source for a laptop computer application. An empirical model was developed to include the phenomena of activation and ohmic polarisation as well as mass transport effects in order to simulate the behaviour of an air-breathing fuel cell. The model was used as the input source for a quadratic buck converter, which is used to power the central processing unit (CPU) core at 1 V. To achieve tight voltage regulation and good dynamic performance, the quadratic buck converter was implemented with average current mode control. The quadratic buck converter hardware setup has been developed with a fabricated fuel cell module in order to validate the model of the air-breathing fuel cell as well as the voltage regulator module.