A LLC Resonant Converter With Multi-Magnetic Paths Used In Wide Gain Range Applications

The research of the power electronics has always been towards high frequency,small volume,modularization,and general applicability.A lot of application challenge the operating range of the power electronics.For example,in solar energy harvesting and wind power generation application,the wide range of the input voltage and stable output voltage challenge the converter to be able to operate effectively in a wide range of the gain ability.In data center application,converter should be able to provide rapidly changing load and still be able to maintain the stable output.In electric vehicle charging application,the converter should be able to charge the battery load however its large scale voltage change.These application all need converter not only perform well in one particular wording status,but should be able to operate efficiently in all scales of the wide operation area.LLC resonant converter has high efficiency,high power density,and can work to provide large gain variation due to its ZVS operation and on reverse loss characteristics.In this paper,the LLC time domain current waves are analyzed,common mode of the LLC converter has been established,gain ability of each mode has been quantified.Also,the transition of different mode has been analyzed,and the gain-frequency cure is drawn.At last,the peak mode operation has been spotted which leads to the optimal design of the LLC converter in wide gain variation.In one particular application,an optimal setting of the LLC converter is given,yet only find its high circulated energy,high operating loss,difficulties in magnetic design,and poor linearity of the control curve.A new multi-magnetic path LLC converter is given to solve them all.The operating mode of the new topology has been analyzed,the electrical characteristics been optimized and control method been provided.In the paper,the different modulation methods are analyzed and compared,different modulation methods have been chosen to fit different mode.Through the time domain modeling,the transient states of the converter while load changes are analyzed and a optimal trajectory control method is given to minimize the transient current and accelerate the stabilization of the output voltage.In the paper,a new magnetic design procedure based on time domain model is brought out.The inductor of the LLC converter has larger ac current and the transformer of it has special need for magnetizing inductance which leads to different design operations than the normal kind.In paper,the different characteristics of the magnetic core are calculated and a new index of the core profitability for the setting application is provided.The design procedure to ensure minimum power loss has been given and the minimum windings are analyzed.In compare,the new topology of multi-path LLC converter has less power loss and smaller volume.Last but not least,the Mosfet switches are chosen and more detailed loss has been calculated,the efficiency of the whole operation area is provided.Several exams have been done to prove the practicability of the topology and the Gain-Frequency plot has been provided to meet the design standard.