Research On The Influence Of DC Bias On The Core Loss Of Switching Converter

Switching converters have high conversion efficiency and small size,and are widely used in industrial equipment,consumer electronics and other fields.With the development of electronic products in the direction of miniaturization,the operating frequency of switching converters continues to rise.The power magnetic element is one of the main components of the switching converter.The high frequency may cause excessive heating of the magnetic core and affect the reliability of the switching converter.Therefore,the study of power magnetic loss becomes very important.In this paper,a core loss prediction model with clear physical meaning and practical engineering significance is established to realize the prediction and calculation of the change trend of the core loss of the switching converter.Firstly,article introduces the physical mechanism of the three components of core loss:hysteresis loss,eddy current loss and residual loss.Aiming at the working characteristics of the magnetic elements in the switching converter,the separation equation of the core composition based on the core loss data under sinusoidal excitation is studied,and the method of separating the hysteresis loss and eddy current loss through two sets of sinusoidal magnetic loss data at different frequencies.Secondly,this paper analyzes the influence of DC bias on hysteresis loss and eddy current loss.It is proposed that DC bias mainly affects the hysteresis loss of power magnetic core in switching converter,and its influence mechanism and quantitative calculation method are given.Set the magnetic flux density as a variable,by measuring the hysteresis loss under several sets of DC bias,obtain the hysteresis loss slice data under the fixed magnetic flux density increment,which can effectively predict different DC bias,magnetic flux density and Hysteresis loss under frequency combination.This paper systematically sorts out the working characteristics of DC bias in magnetic components in common power converters,and takes the power inductors in Buck and Boost switching converters as examples to study the changing trend of rectangular wave and DC bias under different duty cycles.By combining the specific working principle of the converter,the corresponding core loss model characteristics are derived,and the macroscopic change trend of the core loss under different duty ratio conditions is given.Finally,this article compares the advantages and disadvantages of common magnetic loss measurement methods,and proposes a DC power difference method to measure the magnetic core loss in switching converters.Select Ferroxcube’s ferrite magnetic ring TX36/23/15(3F3)and TX25/15/10(3C90),take Buck and Boost circuits as examples to build a magnetic loss measurement platform,and compare the magnetic core loss of the switching converter The actual measured data is compared with the predicted value of the model to verify the correctness of the estimated model.