Design And Implementation Of DC/DC Power Supply Module For Locomotive Signal On-board Equipment

With the improvement of the reliability of locomotive signal on-board equipment,locomotive signal plays a more and more important role in railway operation.The power supply system of locomotive signal on-board equipment is an important part.The power supply system is mainly composed of DC / DC power module to supply power for host circuit and dynamic safety signal lamp.Based on the power supply technology of locomotive signal on-board equipment and the characteristics of wide input voltage range of on-board equipment,this paper studies the topology and control mode of wide input and isolated switching power supply.According to the development goal,carry out the design and Simulation of key parameters and functions of power supply,and complete the design of experimental prototype.Select the appropriate DC / DC power supply topology based on the input and output indexes of the power supply system of on-board equipment.In this paper,two mainstream isolated DC / DC power supply topologies are selected for analysis,namely LLC resonant converter and phase-shifting full bridge converter.By comparing the working characteristics of the two topologies,LLC resonant converter is selected as the main topology of DC / DC power module,and the hybrid control method of phase-shifting control and frequency conversion control is adopted to meet the requirements of wide range input voltage.In this paper,the working principle and working state of LLC resonant converter are analyzed,the soft switching characteristics of LLC are studied,the voltage gain characteristics of LLC are analyzed by fundamental wave approximation method,and the resonant current and device loss of LLC are calculated by simplified time domain analysis method.The relationship between LLC device loss,transformer area product,resonator current under phase-shifting condition,soft switching condition and LLC resonator parameters is analyzed.The parameter design flow of LLC hybrid control is given,and the LLC efficiency of the designed parameters is analyzed.The device selection of LLC main circuit is carried out,and the minimum system circuit,driving circuit,sampling circuit and auxiliary power supply circuit are designed.The control circuit is designed with stm32f302rct6 single chip microcomputer as the digital control chip.The LLC small signal model is obtained by using the extended description function method.According to the small signal model,the effects of LLC input voltage and load on the stability margin and zero pole distribution of the control loop are analyzed,LLC controller is designed.LLC magnetic components adopt magnetic integration technology and use the leakage inductance of transformer as the resonant inductance of LLC resonant converter.A magnetic integration transformer model is built in ANSYS Maxwell software.The effects of the distance between the original and secondary windings and the size of air gap on the excitation inductance and leakage inductance of transformer are simulated and analyzed,and the magnetic integration transformer is wound.Based on the above design,the LLC resonant converter was simulated and analyzed by PSIM software to verify the rationality of the parameter design,and a 100 W DC/DC power module experimental prototype was produced.