Research And Design Of Vehicle-mounted DC/DC Converter Based On Planar Transformer

With the operating frequency up to 1 MHz,the switching loss and on-loss of semiconductor devices are becoming more and more obvious,which seriously reduces the efficiency of DC converter.Therefore,high efficiency and high power density,as well as the miniaturization of the whole machine,have become the new development trend of the new low voltage and high current DC / DC converter.Transformers play an important role in DC converters.The larger core structure of traditional transformers and the traditional copper wires not only affect the volume of DC converters,but also the copper windings.It also restricts the power density of the converter.Therefore,with the trend of miniaturization and high efficiency and energy saving,plane transformers have more advantages than traditional transformers,such as low shape,low leakage inductance,good heat dissipation characteristics and so on.It is more suitable for high power density and high working frequency DC / DC converters.Efficiency is one of the important indexes to evaluate the performance of power supply in vehicle-mounted DC / DC converters with limited volume and bad working conditions.In this paper,the loss model of full-bridge converter is built according to the design of plane transformer,the choice of power device and the optimization design of main circuit parameters.The main loss source of DC converter is obtained by analyzing the loss model,which is convenient for the efficiency optimization of converter.This paper first introduces the development and present situation of DC converter and planar transformer,introduces the theory and design steps of planar transformer in detail,and then analyzes the topology and principle of the main circuit of full-bridge converter.The main circuit structure,parameter selection,loss calculation,control circuit design and drive circuit design of the working prototype are introduced in order to improve the efficiency of DC converter.In this paper,the two-dimensional model of planar transformer is established by using Maxwell eddy current field module,and the finite element analysis of computer is used to replace the theoretical calculation.The accurate calculation of winding loss is convenient to select the appropriate winding structure.The main circuit model of DC converter is built in the LTspice circuit simulation,the device parameters are set up,and the rationality of the parameter design is verified.Based on the theoretical design,an experimental model with 120 k Hz operating frequency and output 28V/130 A is made.The synchronous rectifier technology is used to reduce the loss of rectifier circuit,and the maximum efficiency of the prototype is up to 92%.