The Design And Research Of Quasi Resonant Flyback Power

Under the trend of the rapid expansion of the electric vehicle industry,the contradiction between the sharp increase in the number of electric vehicles and the insufficient number of charging piles is getting more and more obvious.Apart from charging piles superior performance and high efficiency,what's more important is to have higher reliability and stability.In this paper,an auxiliary power supply is designed for the power module in the charging pile with the flyback circuit as the basic topology.The quasi-resonant control is used to achieve high-efficiency operation of the power supply.For the flyback power supply,the turn-on time and demagnetization time in the switch tube decrease as the load decrease s,and the oscillation time does not change,so the switching frequency increases as the load decreases.The increase of power supply operating frequency will result in the increase of the power consumption of the switch,reduce the efficiency and cause more electromagnetic interference.Therefore,the switching frequency of the power supply under various operating conditions must be controlled within a certain range.The hysteresis valley jump control circuit is designed during heavy load,which mainly includes the valley detection technology and the hysteresis control.Valley jump control actually controls the switch tube to conduct when the drain-source voltage fluctuates to the bottom of the valley,and with the load decreases,the number of valleys that are turned on continuously increases to reduce the switching frequency.The efficiency of the power supply can be improved because the voltage is lower when the valley bottom is turned on.The introduction of the hysteresis control can prevent the error jump caused by circuit fluctuations,which thereby improves the fault tolerance and stability of the power supply.The fixed peak current is designed to control circuit during light load.When the input voltage is constant,the on-time of the switch is fixed by fixing the peak current.The off-time is determined by the feedback voltage and the voltage on the charging capacitor.The feedback voltage reduces when the load decreases,and the voltage of the capacitance needs to be higher to enable the drive signal,so it takes longer time to reduce the switching frequency and improve the efficiency of the power supply at light loads.After the flyback power supply small signal modeling of the peak current control mode and the compensation network of the flyback p ower supply design,the loop analyzer is adopted to debug the loop parameters of the hardware circuit.In this paper,a transformer for flyback power supply and overvoltage protection circuit and clamp circuit for power supply is designed.Using the simulation software SIMPLIS,a simple simulation verification was performed after the model was built.Based on the simulation,the construction of the prototype was completed,and related test verification was built.The hardware power output diode overvoltage was debugged.The feasibility of the design was verified by experiments.The result shows that the designed power supply has the advantages of low ripple,high efficiency and high stability.