A Practical Implementation of a Two-Stage 350-W Universal Charger for Power Mobility Device Charging Applications

A universal, two-stage (PFC+LLC) charger is developed for Power Mobility Device (PMD) charging applications (i.e., electric wheelchairs and scooters). A rectifier-boost PFC topology is used to interface with the AC grid, establishing a ≈386-VDC bus and maintaining around 96% efficiency for all loading conditions. A dual-loop controller for the LLC resonant converter with a wide operation region is designed to achieve CC-CV for different capacities of 24-V batteries. The LLC converter achieves a peak efficiency of 95.5%, making the two-stage charger 91.6% efficient. This paper presents a comprehensive design, implementation, and testing validation for major aspects of the charger. The charger is rigorously tested, passing all power factor (PF), total harmonic distortion (THD), and conducted EMI safety requirements set by IEC 61000-3-2 and CISPR 22 regulatory standards. The paper not only offers theoretical insights but also presents a comprehensive guide to the practical design and testing procedures of every facet of the charger.