High Efficient Design Of Auxiliary Power Supply Of Vehicle Charger For Electric Vehicle

As the energy and environmental issues become increasingly prominent, electric vehicles (EVs), which is energy-saving and green to environment, has received great development potential. At present, there are still some constraints on EV battery technology, which becomes the barrier for wider EV uptake. Other than the need of improvement for EV battery, an on board charger (OBC) with perfect performance is required to realize complete replacement of gasoline by rechargeable battery packs.Generally, an OBC consists of the front-end AC/DC converter with power factor correction, the back-end DC/DC converter, auxiliary power supply module and control block, etc. The required power supply for each module is not exactly the same, and thus multiple output power supplies with different specifications are required. An auxiliary power supply is designed to provide a stable DC voltage for each function module of OBC. Therefore the high efficient design of auxiliary power supply is of great importance in theoretical research and engineering application.Two auxiliary power supplies are designed for 2KW and 3KW OBCs respectively. To meet requirements of small size, stable output voltage and high efficiency, several topologies are compared and finally the flyback converter is chosen as the main circuit topology of the auxiliary power supply. Taking into account different design specifications of the two auxiliary power supplies, critical components of the main circuits including transformers, RCD circuits and output capacitors, etc. are designed firstly. The traditional PWM current mode control strategy is adopted in the design case for 2KW OBC. In order to achieve an improvement of system efficiency, adaptive multi mode control and valley current mode are introduced to reduce switching losses. Considering the low efficiency of the diode rectifier, synchronous rectifier technique is applied in the auxiliary power supply for 3KW OBC to reduce the conduction loss caused by conventional rectifiers. In the last part of the dissertation, simulation tests are conducted based on Saber software for the auxiliary power supplies in 2KW and 3KW OBCs respectively. PCBs are designed based on Cadence software and the prototypes of the two auxiliary power supplies are built. Experimental results of the two hardware prototypes show that the auxiliary power supplies can achieve high efficiency which confirms the feasibility of the design.