Design and implementation of a buck converter for low-voltage battery charging applications with STM32 microcontroller

This thesis presents the complete design, implementation and validation of a 300W synchronous buck converter for low-voltage battery charging applications. The project is driven by system-level requirements and covers all aspects of the design. The work begins with the definition of the system and converter-level requirements, followed by the selection of the microcontroller. The power stage design is developed in detail: each component is selected according to the requirements and based on electrical and thermal considerations, supported by analytical calculations and simulations. A robust bi-directional over-current pro- tection circuit is designed to be completely independent from programmable logic and wrong connections. The measurement system is developed to ensure accurate voltage and current sens- ing, utilizing operational amplifiers and a shunt-resistor-based current sensing. A control system is then designed, featuring cascaded PI regulators for current and voltage control, enabling constant current (CC) and constant voltage (CV) func- tionalities. Models are derived analytically and validated through simulation using MATLAB, Simulink, and PLECS. Feed-forward techniques and anti-windup mech- anisms are introduced to enhance system responsiveness and stability. An active pre-charge algorithm is also developed to safely connect battery packs without cur- rent peaks. The system is implemented on a four-layer printed circuit board (PCB) with focus on signal integrity and thermal management. Detailed layout and component place- ment considerations are described. In the end, in order to validate different parts of the design, a series of preliminary tests were carried out with the assembled PCB.