Research On LCC Resonant Converter With Wide ZVS Range

Research on Switching Mode Power Supplies(SMPS)with high efficiency and power density is becoming the hotspot in the power electronics field.By increasing the switching frequency,the volume of magnetic elements could be obviously reduced.However,higher operation frequency will lead to higher switching loss in the traditional PWM converters.Resonant DC-DC converters have been widely used due to their advantages such as soft switching characteristics.LCC resonant converter has good voltage regulation feature and small circulating loss at light load by combining the virtues of series and parallel resonant converter.Therefore,it is taken as the studied converter in this paper.The range of switching frequency variation of variable frequency LCC resonant converter is wide,which is not beneficial to the design of magnetic elements.The magnetic elements of fixed frequency LCC resonant converter are easy to design,but it might lose ZVS condition.A detailed study of fixed frequency LCC resonant converter has been presented,which includes working mode,soft switching condition and resonant current.It is concluded that we should make trade-off between the range of ZVS and resonant current in parameter design process.The reason of the narrow ZVS range of fixed frequency LCC resonant converter is analysed and the methods to broaden ZVS range from topological structure and control strategy are summarized.To extend the ZVS range of fixed frequency LCC resonant converter,a passive auxiliary network which consists of inductor and capacitor is proposed.The working principle of LCC resonant converter with auxiliary network,including working mode,steady state model,soft switching condition and resonant current is analysed.The detailed parameter design of the converter is given,which can not only achieve ZVS operation in wide input voltage and/or load variation range,but also optimize the resonant current.An asymmetrical hybrid modulated Buck-Boost half-bridge LCC resonant converter which integrated a Buck-Boost converter and a half-bridge LCC resonant converter with switch integration technique is proposed.It is a single-stage converter,which avoids the shortcoming of traditional two-stage converter,such as enormous component number and large volume,and which has low conduction loss and high efficiency.Because the switching frequency is proportional to duty ratio by using asymmetrical hybrid modulated technology,the ZVS operation in wide input voltage and/or load variation range is realized and the effiency is improved.The integration process and working principle of the proposed converter are analyzed in detail.The realization scheme of asymmetrical hybrid modulation and the steady-state model and parameter design of the converter are researched.Finally,simulation and experimental results are given to verify the correctness of theoretical analysis all above.