Bidirectional DC Voltage Conversion for Low Power Applications

Battery-powered mobile equipment is an important pillar of the electronic consumer market. Unfortunately, the batteries provide a limited operating time, which can only be increased by developing new battery chemistries with higher energy densities; or by using the energy more efficiently. This thesis focuses on the latter and describes the development of an intelligent power converter (IPC) combining the voltage conversion unit with the battery management, thus providing a regulated and adjustable voltage directly to the mobile equipment. The characteristics of the IPC are an operating voltage range between 1.2V-3.6V and an average load current up to 2A. Novel solutions were developed for the IPC, like a method for detecting automatically the connection of a battery charger in parallel to the load, a continuous regulation loop for enabling highly efficient step-up and step-down conversion in both directions and at high switching frequencies. A current sensing method has been developed for estimating the average inductor current at switching frequencies up to 10 MHz. The IPC enables battery upgrading (e.g., different chemistry) to extend the operating time of the mobile equipment.