Mission Profile Based Optimization of a Synchronous-Buck DC-DC Converter for a Wearable Power System

A Wearable Power System (WPS) is a portable fuel-to-electrical energy converter that is carried on the body and is able to supply an average of 20 W for 4 days and has a total weight of less than 4 kg. Due to limited total weight of the system, each system part must have the highest efficiency to weight ratio. This paper presents the optimization of a synchronous buck DC-DC converter that is used to regulate the variable power source to a constant 14 VDC for the load. Higher switching frequency leads to smaller components and low weight, but at the same time, to higher losses that are compensated through additional fuel weight. If low switching frequency is applied, the weight of the converter will increase due to a larger inductor, but the power losses will be lower. Therefore, an optimal switching frequency should exist that results in the total weight of the DC-DC converter and additional fuel being a minimum. The paper first explains the proposed solution for WPS, the load pattern that is used to test the system and then the algorithm that decides on the number of converters to be used and how to find the optimal switching frequency. Additionally, two prototypes have been constructed. First prototype has nominal power of 20 W and is used in the analysis regarding the optimal number of converters. The second one has rated power of 200 W and it is built to support the conclusions based on the optimization process.