Variable Turns-Ratio Matrix Transformer based LLC Converter for Two-Stage Electric Vehicle Auxiliary Power Module Applications
Zhengming Hou, Sheng Cheng Kao, Dong Jiao, Jih‐Sheng Lai
Abstract
An auxiliary power module (APM) is needed in electric vehicles, which converts traction battery voltage (270430V) to the low voltage auxiliary system (12.5∼15.5V). The single-stage design may achieve high power density but will suffer from poor efficiency and wide input voltage regulation capability. The design with two-stage can achieve wide-range regulation and good efficiency but will suffer from low power density. In order to achieve high efficiency while maintaining a good power density, a variable ratio matrix transformer based LLC is proposed to replace the fixed ratio transformer based LLC-DCX stage in two-stage AMP. The variable turns ratio matrix transformer reduces the low-side copper losses via the adaptive number of element transformers. Additionally, the buck stage achieves better efficiency with the variable intermediate bus voltage. As a result, it is potential for the system to reduce the cooling requirements with high-efficiency power conversion. A 1.6 kW prototype achieves 97.21% peak efficiency with 1.8 kW/L power density.