Research And Circuit Design Of 3.5kW Electric Vehicle Charger

With the development of economy and the improvement of people’s living standard,the conflict between the growing demand of electric vehicles and environment problem is more and more serious. Rapid development of electric vehicles not only meets the pursuit of convenient traffic but also do not pollute the environment, and our country has backed its development. As a rechargeable battery supplies with power for electric vehicle, battery technique is the key to the development of electric powered automobile. On-board charger is an equipment which can charge the battery.Therefore, the study of on-board chargers, which have good performance, has important practical significance.As an important component of EV power unit and an equipment in the link of EV and power grid, on-board charger must have high performance on these aspects, such as volume, efficiency, power factor, harmonic current and EMI. There are many types of power battery, while the parameter characteristic of each type of power battery is different. Battery charging and discharging processes are controlled by the corresponding battery management unit (BMS). Therefore, it is necessary to design of CAN bus communication between BMS and on-board charger based on DSP. In accordance with BMS instructions, battery charger completes the processes of charging the battery.According to the performance requirements of relevant national standards on electric vehicle, the dissertation finally designs an electric vehicle charger that input power is 3.5kW, under the premise of understanding technical index of the charger and protection level of the charger. On the basis of analyzing several existing topologies and their control modes, battery charger is proposed based on interleaved boost PFC and full bridge LLC topologies, front-end stage for rectification of ac input power and power factor correction (PFC), and second-stage dc/dc converter for voltage regulation and galvanic isolation. Front-end stage converter achieves PFC with the use of the UCC28070A interleaved PFC controller. Second-stage LLC converter adopts digital control technology with the use of the 32 Bit TriCoreTm micro controller TC1724, which can realize the CAN communication between BMS and on-board charger.As proposing detailed technical design indicators, first, the dissertation analyzes the principle and characteristic of interleaved boost PFC, and selects proper elements for the converter controlled by UCC28070A chip. Of course, the correctness of the parameters is verified by the simulation tool PSPICE. Then, the dissertation makes a thorough study of the principle and characteristic of full bridge LLC resonant converter both in time domain and in frequency domain. The vector model of currents is utilized to design parameters of full bridge resonant converter. The simulation software SIMPLIS is used to test main parameters about the converter. An on-board charger device prototype was constructed. Experimental results demonstrated that the system realized the constant-voltage limitary-current charge of batteries properly. The framework of this dissertation has feasibility and provides theoretical and experimental basis for on-board charger’s design optimization.