Design Of Auxiliary Power Supply For High Efficiency Electric Vehicle Based On PSR

With a large number of energy consumption and air pollution becoming increasingly serious, the development of car industry has been transformed to electric vehicles. As an important equipment of electric vehicle, power system mainly composed of power battery and low voltage battery. Power battery provides energy for electric motor and stores braking energy by some way. Low voltage battery offers energy for vehicle lighting, instrumentation and control system, while vehicle's auxiliary DC/DC converter is considered as a bridge between the two groups of batteries. In order to adapt to the serious vehicles' working condition, higher request was put forward to the performance index of efficiency, precision, volume, stability and so on.Firstly, this paper introduces the research status of electric vehicle power supply, considering the auxiliary DC/DC converter's 12 V and 5V output applications, multiplexed output flyback topology is chosen to be studied after comparison, and then we discuss two kinds of feedback control method, where DCM mode of current control is finally chosen as the feedback control method, the primary side feedback and secondary side feedback principle is also introduced. In order to achieve the purpose of precise control on electrical circuit, we build the small signal equivalent model to obtain the transfer function of the circuit.Secondly, considering the limitation of electric vehicles working environment, on the basis of the analysis of the selected topology, we study the whole power system structure, which is divided into different functional units, and then according to each parameter design of each unit, we improve the efficiency of the converter.Then, this paper introduces a new primary side feedback sampling algorithm to improve the traditional secondary side feedback, and removing the volatile component to overcome weakness of the traditional primary side feedback, which makes the system realize miniaturization and improves the stability and efficiency. In the algorithm, on the basis of theoretical research, the software design of the system mainly includes the design of PID control algorithm, PSR accurate sampling algorithm design, system's process design of the main program and interrupt subprogram flow design, etc.Finally, this paper uses Saber, MathCAD and Simulink to establish the simulation model of electric vehicles auxiliary DC/DC power supply, and the experiment platform is built and simulation is carried out. The simulation results show that multiplex flyback DC/DC converter can realize the stability of the DC output. At the last, the performance test of proposed auxiliary power supply prototype is carried out, and its efficiency is relatively high which approximately reaches 90%, the voltage ripple and control accuracy can meet the design requirements, which illustrates accuracy of power circuit and control circuit design and the stability of system.