Research On 3kW 28VDC/±135VDC Converter

With the rapid development of power electronics technology,high-frequency switching power supply is widely used in information,railway,energy,aviation,aerospace,national defense and other fields because of its advantages such as light weight and small volume.According to the requirements of an enterprise,we develop a DC/DC converter with rated 3kW output power,28 VDC input(input voltage range 24VDC-32VDC)and 270VDC(±135VDC)output.According to the high power density and high reliability requirements,the phase shifting full bridge circuit is selected.This paper firstly analyzes the working principle and several key problems of the phase shifted full bridge PWM converter,including duty loss,ZVS strategy and transformer DC bias.In order to improve the reliability of the converter,the primary current peak current control strategy is adopted.In this paper,a simple and effective primary side current magnetic isolation detection method,double magnetic loop detection circuit,which can be used for peak current control,is proposed.Secondly,this paper analyzes the necessity of slope compensation and design method,introduces the peak current control principle of phase shift full bridge converter and the calculation method of slope compensation,and a small signal model of the phase shifted full bridge converter under the peak current control is built.In this paper,the engineering realization method of 3kW principle prototype is given in detail,including the selection of power pipe and the design of magnetic element.Based on the above theoretical analysis and engineering design,a 3kW prototype is completed to carry out the experimental verification.The experimental results verify the correctness of theoretical analysis and engineering design.Especially for the problem of transformer DC bias,the experimental results show that the converter can suppress the transformer DC bias effectively by double magnetic loop current transformer.Finally,the loss of the phase shifted full bridge PWM converter is analyzed in detail,including main power transistor,magnetic element,rectifier diode and absorption circuit,and the transformation efficiency of the converter is calculated,the results are in agreement with the experiment.The analysis results show that the main loss main power transistor and the absorption circuit,and measures to further improve efficiency are pointed out.