Resonant Soft-Switching Constant Current Charging Power Supply

Storage battery has been widely used in mine electrical vehicle and uninterruptible power supply because of the large capacity and high power density in recent years. The charging power supply as the energy supply equipment is closely linked to storage battery and its performance affects the overall performance of storage battery. The conventional charging power supply has high switching losses, low efficiency and low power density. So it is very meaningful to research the charging power supply with the features of high efficiency and high power density.This paper analyzes the current status of charging power supply and identifies that soft-switching technique is the effective method to increase efficiency and power density. According to the advantages and disadvantages of common soft-switching topologies and the operating characteristics of constant current charging power supply, the main circuit of current charging power supply is identified to use series load resonant converter and half-bridge LLC resonant converter. This paper does a further research on the interleaved parallel technique of two series load resonant converter units.According to the condition of constant current output and the features under different operating modes of series load resonant converter, it is clear that resonant current of converter should be operated in discontinuous mode. The ZCS condition of switch is discussed through analyzing principle of the converter. The rectifier structure of series load resonant converter on low-voltage and high-current conditions is also analyzed. This paper also researches the interleaved parallel control mode of two series load resonant converter units. Fixing pulse width, adjusting frequency and shifting phase is used to the control method. Main circuit and control circuit are designed and the simulation of interleaved parallel converter with two series load resonant converter units is carried out.The working principle of the half-bridge LLC resonant converter in two different switching frequency ranges is analyzed. The equivalent model of the converter by the fundamental analysis method is built. The current transmission character and the voltage gain are analyzed based on the model of the half-bridge LLC resonant converter, and the condition to achieve ZVS soft-switching is analyzed combined with the input impedance character of the converter. The circuit parameters are designed based on the analysis results, and the simulation is carried out.The two units interleaved paralleled series load resonant converter and the half-bridge LLC resonant converter are verified by experiments through the experimental platform. The experimental results show that full-bridge rectifier is suitable for series load resonant converter , and both of the two series load resonant converter units working at the interleaved paralleled state can achieve ZCS soft-switching, and the effect of the two interleaved paralleled units is well, the ripple of the total output current is improved. And the ZVS soft-switching can be realized throughout the whole process of the half-bridge LLC resonant converter. The efficiency with constant current charging of the two circuit topologies is high.