Single Stage Isolated AC/DC LLC Resonant Power Conversion Stage With Reduced Current/Voltage Stress for Portable Light EV Charger Development

Transformation efficiency and system power density are critical parameters in design of a portable, cost-effective EV charger. This results from conventionally adopted dual-stage power conversion for low and medium power processing, featuring a primary hard-switched stage. This paper presents a design for a single-stage direct AC/DC LLC resonant converter-based electric vehicle charger to address this issue. Converter employs an interleaved inductor principle at grid end and split grid link principle so that each interleaved phase realising only half of grid voltage. This implementation effectively reduces voltage stress across MOSFETs and facilitate inherent power factor correction with discontinuous interleaved inductor current mode (DIICM) operation. DIICM design encompasses compact passive footprints and facilitates straightforward control implementation. A time-weighted average design (TWAD) is adopted, which encourages elements design based on system constraints. Furthermore, DIICM of the interleaved state and TWAD design of LLC tank parameters enable a single charging current control loop, which offers DC link boost capability alongside charging current tracking. Proposed concept is validated through a 0.5 kW design for simulation purposes and a 1.5 kW practical laboratory prototype to enable efficient EV charging for 42-58 V output voltage range. Proposed design is validated with simulation and experimental results over grid and charging scenarios.