Research On Wide Input Range DC-DC Converter Suitable For High Voltage And High Power Auxiliary Power Supply Applications

As a converter that can achieve a high DC step-down ratio,high-voltage wide-input-range low-power isolated step-down power supply has been widely used in high-voltage DC transmission systems,solid-state transformers,reactive power,and harmonic compensation as auxiliary power supply.At present,research on isolated step-down power supplies mainly focuses on how to reduce voltage stress,how to achieve voltage balance,and how to improve efficiency.This paper analyzes the research status of high-voltage wide-input-range low-power isolated step-down converters,focusing on analyzing the advantages and disadvantages of various topologies based on flyback,the adaptability of high-voltage applications and efficiency optimization.By comparing typical isolated step-down converters with high-voltage adaptability,an input series magnetically integrated active clamped flyback converter with advantages such as a simple topology,low power device stress,and high efficiency is proposed.Traditional active clamped flyback circuits usually use complementary drives.This paper analyzes the working principle of complementary active clamped flyback with bidirectional magnetizing current,and analyzes the working principle of non-complementary critical continuous active clamped flyback.The difference between continuous mode and discontinuous mode is compared,and non-complementary driving method with short on-time and small circulating current in the clamped circuit is finally adopted.The converter with input series magnetic integrated structure can realize self-balancing of series modules.This paper analyzes the voltage ratio of each module in the static state,and in-depth studies the self-balancing mechanism of the active clamped flyback in different modes when the input voltage of each module is different,and preliminary verification is performed through simulation.In order to explore the best control strategy for high voltage and low power applications,this paper first introduces the method of critical continuous realization under quasi-resonant control.The working principle of quasi-resonant control that can turn on the clamped switch at drain-source voltage valley is analyzed in depth,as well as characteristics of off-time control and fixed-frequency control.The advantages of the quasi-resonant control are preliminary verified through simulation.According to the given design indicators,the appendix gives the magnetic design results of the active clamped flyback,and an experimental platform with 200V～1000V input,± 15 V output,and45 W power is set up.The characteristics of different control methods are verified and compared through experiments,and the working principle of the converter is also verified.The peak efficiency is about 89%.The voltage sharing conditions of the converter under different control methods and different working conditions is verified,and voltage sharing characteristics when tolerance features of the key parameters are considered during different input voltage and load switching is also verified.The voltage sharing advantage of the magnetic integrated structure is illustrated.