Prototype Development of an Isolated DC/DC Converter for Modular Multi-Port E-Bike Charging

Sammanfattning

This thesis deals with the creation of a battery charging system for 48 V and 36 V batteries. The main objective was to create an efficient system with telemetry and protections against problems that can arise with current, voltage and temperature. To achieve this goal an active clamp forward converter was simulated in LTSpice and designed. Thereafter control systems and monitoring capabilities were designed on a printed circuit board. In the language C, functions to protect and monitor against current, voltage, and temperature were designed as well as a charging algorithm that ensured constant current constant voltage charging. The monitoring and protection functions for current, voltage, and temperature were successfully implemented. The charging system was successful in reaching voltage levels to charge 48 V and 36 V batteries. A 48 V battery was successfully charged using the charging system. It was however limited from reaching designed maximum output power. This was found to be due to unexpected voltage spikes over the MOSFETs that appeared with increased output power and current. Possibly unaccounted for parasitic trace inductance on the printed circuit board lead to this phenomenon and the inability to thus evaluate efficiency and it’s thermal tolerance. Thus an intelligent charging system with telemetry was successfully designed, although it could not reach the set power and efficiency targets.