Seamless Switching Technology for Low Voltage Charging in 800V Electric Vehicle Systems

In response to the high voltage stress issue in the secondary components of the DC/DC converter caused by increasing the electric vehicle charging system from 400V to 800V, a low-voltage seamless charging switching technique is proposed. Building upon the optimized design of the 400V DC/DC converter, this technique utilizes the Battery Selection Circuit (BSC) to enable charging of 800V high-voltage batteries. The topology is described, along with a simple modulation scheme, providing a detailed explanation of how the BSC circuit achieves seamless and dead-time-free charging for two 400V batteries. This enhances the reliability of the converter, reducing grid load fluctuations caused by a large number of electric vehicles charging. The lower voltage stress on the converter components and the separate design of the BSC circuit's switching frequency result in overall lower losses and improved efficiency and energy utilization on the load side of the system. Finally, an experimental prototype is built to further validate the feasibility of the proposed technique.