Research On LCC Resonant DC-DC Converter

Along with the development of information industry,the demand for power efficiency and power density is getting higher and higher.For example,full load efficiency of titanium gold power converters certified by American 80 PLUS project is higher than 90%,and half load efficiency is higher than 96%.High frequency resonant DC-DC converters have been widely used because of their advantages such as small electromagnetic interference and high efficiency.LCC resonant converter combines the characteristics of series resonant converter and parallel resonant converter,and has the advantages of light load high efficiency,small output ripple voltage,and has great application potential in server power supply field.SRC and PRC circuit structures are simple and theoretical research has been quite mature,but the resonant components of the LCC resonant converter are more,the modal analysis is complex,and the theoretical research is not clear up to now.Time domain analysis can not get analytical expression.The fundamental harmonic analysis method only considers the fundamental frequency,and simplifies the equivalent model of the rectifier bridge.Extended fundamental harmonic analysis method considers the fundamental frequency,and the accurate equivalent model of the bridge is established,so the error is small.High order harmonic analysis method is used to calculate the equivalent model of each harmonic.In theory,it is the exact analysis method,but the numerical solution is needed to get the final result.This paper studied four kinds of analysis methods.A detailed study of the process of derivation has been presented and contrasted to provide the reference for industry application.The operating characteristics of LCC resonant converter are determined by the resonant parameters and the transformer turns ratio.The expression is complicated,and the work areas are difficult to define,and the parameter design is complex.It is important to study the operating characteristics and the key index optimization strategy of LCC resonant converter.Extended fundamental harmonic analysis method is used to analyze the working areas of the LCC resonant converter on variable frequency control and phase-shifted control.The relationship between the characteristics and parameters of the converter is demonstrated by the MATLAB drawing.The phase-shifted LCC resonant converter has the advantages of fixed switching frequency,narrow noise spectrum and easy design of magnetic components.However,when the load is light,the lagging arm MOSFETs of the converter are easy to lose zero voltage turn-on characteristic.In order to solve this problem,ARCP LCC resonant converter is proposed by introducing auxiliary resonant commutated pole circuit.The LCC resonant converter can achieve ZVS on heavy load,so ARCP doesn't work.On light load ARCP has to put into operation to help the lagging arm MOSFETs to achieve ZVS with auxiliary current.Theoretical analysis shows that the efficiency of the ARCP LCC resonant converter is higher than that of the hard switching phase-shifted LCC resonant converter.Finally,the experimental results verify the correctness of the theoretical analysis.