Design Of Wide Range Input Two-Stage Vehicle Switching Power Supply

As the power conversion device,vehicle switching power supply needs to meet the normal working requirements of automotive electronic devices under any working conditions,such as sudden changes in vehicle load,instant start-up and braking of vehicles,or low power operation of electronic devices in standby mode under any working condition.It is required that the vehicle switching power supply can still operate normally and reliably when the input voltage varies within a wide range,which can not only ensure the normal operation of the electronic equipment in the vehicle,but also reduce the maintenance workload caused by the equipment damage to the power supply manufacturers.Therefore,it is of great significance to study a wide range of input switching power converters and control.Aiming at the problems such as wide fluctuation range of 24 V input voltage in vehicle power supply,large duty cycle and serious temperature rise in single-stage converter,a 18V-72 V input two-stage switching converter is designed in this thesis,which achieves the stability of output voltage in a wide voltage input range.The input voltage is converted from 18V-72 V to 57V-72 V by BOOST converter in the front stage,which can reduce the input voltage range and make the latter stage circuit work in the best working condition;considering the wide range input make duty cycle range of converter increase,intermittent work mode is introduced.The front stage is in the step-up state when the input range is 18V-57 V,and in the “dormant” state when the input range is 57V-72 V,which makes the per-stage boosting stress reduce greatly.In view of the effect of input voltage disturbance on the system,a single cycle control method is adopted to effectively improve the anti-interference ability of the system.Push-pull double forward topology is adopted in the back stage to step down the voltage from 57V-72 V to 24 V,which realizes the stable output of the back stage.And,the peak current double loop control is used to improve the transient response speed of the system and realize the function of limiting current by cycle.Aiming at the influence of transformer leakage inductance on the circuit,the 1:1 isolation transformer is designed by using the original and auxiliary muti-strandlines,which greatly reduces the leakage inductance and optimizes the circuit design.The IR1155 s control chip is used in the front stage and the UC3846 control chip is used in the back stage,which reduce the power supply volume and saves the cost.In order to solve the problem of extra loss in auxiliary power supply,the peak clamping power of the rear stage MOS transistor clamping power is used as the power supply of the auxiliary power supply,and the output rectifier diode clamping power is combined with the auxiliary power supply to supply the internal device of the two-stage topology which improves the utilization rate of electric energy and avoids unnecessary loss.Aiming at the problem of electromagnetic compatibility of vehicle switching power supply,the causes of interference and radiation caused by interference sources in the design are analyzed in this thesis.And,the corresponding suppression methods are proposed to make the design achieve the engineering effect.The experimental prototype of DC power supply is built,and the detailed parameter calculation process is given by using the debugging method of step by step and whole.The design of main circuit and control circuit is perfected by using SABER software to aid simulation.The experimental results analysis of the prototype is completed,which verifies the correctness and feasibility of the above principle design.