Research Of Wide Input Voltage DC/DC Converter For Vehicle

In recent years, China’s sustained and rapid growth of the economy greatly promote the development of the overall automotive sector. But at the same time,it also intensifies the speed of our energy consumption and has a negative impact on the environment, which restricts the sustainable development of the whole society. In this background, the electric vehicle has received a lot of attention because it can solve the energy crisis and environmental pollution effectively.Power battery as the core part of electric vehicle, completes the energy transmission to the motor through the high-voltage electrical system and stores up the regenerative braking energy. The DC/DC converter for vehicle will convert the energy of power battery to low voltage DC power to charge low voltage auxiliary battery. Besides, it can also provide the electrical energy for low voltage electrical apparatus such as the car’s lighting equipment, instrument system and refrigeration system. Therefore, the research of DC/DC converter with high efficiency, high reliability and high power density has important significance for further development of electric vehicles.The single DC/DC converter is classified and summarized, and the advantages and disadvantages of various topologies and their application are mentioned. According to the requirement of wide input voltage, the Boost+LLC with high efficiency features is used as the main topology, and the theoretical and experimental studies are carried out.In this paper, the steady state analysis of the pre-stage Boost converter is carried out, and the parameters of the pre-Boost converter working in the current continuous mode(CCM) are calculated. According to the characteristics of the control circuit and the requirements of the system’s dynamic characteristics and the stability of the loop, the design of the compensation link is accomplished to ensure the stability of the system. The rear-stage LLC resonant converter uses variable frequency control method to achieve the effect of soft switch. It derives for LLC resonant circuit’s voltage gain characteristics through the fundamental analysis method and then the resonant tank parameters is designed according to the voltage gain characteristics. It can promise the bridge arm’s switches of LLC zero voltage open(ZVS) in the full load, and the switches for the secondary rectification zero current shut down(ZCS) in wide range for the purpose of achieving the high efficiency.On the basis of theoretical research and the design of parameters,UCC25600 is used as the control chip of LLC, and an experimental sample is built with the parameters that input voltage of 100V-350 V, output voltage of 24 V and the power of 1200 W. The experimental results show that the two circuit can achieve high efficiency in the condition of wide input voltage.