Research On Topology And Current Sharing Of Coupled Resonant Tank Multi-phase LLC Resonant Converter

With the continuous changes in modern lifestyles,the rapid development of the digital economy has led to a rapid increase in the power consumption of data center,and the development of the new energy vehicle industry has promoted the rapid growth of electric vehicle power consumption.DC/DC converters are widely used in data center power supply systems,electric vehicle charging and other fields.In order to fully improve energy utilization,the DC/DC converters require higher efficiency,high power density,and miniaturization.The LLC resonant converter can achieve zero voltage turn-on(ZVS)on the primary side switch in the full load range,and the secondary side rectifier diode can achieve zero current turn-on(ZCS),so it has higher efficiency and power density,so it is widely used.For low-voltage and high-current applications,the input-parallel-output parallel(IPOP)structure has unique advantages.Research on the parallel technology of multi-module LLC resonant converters is the key to system expansion,which is of great significance.Due to the deviation of the manufacturing process of inductors and capacitors,the resonance frequency of each module is different,which causes the current of each module to be unbalanced,thereby reducing system reliability.This paper proposes a way of achieving automatic current balance.The main research contents are as follows:Firstly,this paper proposes a series of coupled resonant tank(Coupled Resonant Tank,CRT)multi-module LLC resonant converter topologies that can achieve autonomous current sharing,including shared resonant capacitor CRT topologies and shared resonant inductor CRT topologies.To establish the coupling relationship of each module,there are three coupling methods,including short-circuit coupling,inductive coupling and capacitive coupling.The concept of coupling index is proposed,and the influence of the change of coupling factor on the current balance error is studied.Secondly,the current sharing error analysis methods of two types of CRT topologies are proposed,and the equivalent circuit based on First Harmonic Approximation Analysis (FHA)which load is decoupled and resonant tank is decoupled is established.From this, the current sharing error mathematical model of various topologies is established,and the difference in resonance parameters is studied.The influence of different coupling factors on the current sharing characteristics is discussed.Finally,in order to verified the current sharing performance of the proposed topologies,a IPOP two-phase LLC converter prototype with 48V/30 A built.The proposed topologies can achieve current sharing performance automatically without any additional circuit and control strategy.The current sharing performance is different under different coupled impedance,for the common capacitor CRT topologies the best coupled impedance is inductor.And for the common inductor CRT topologies,the best coupled impedance is capacitor.The dynamic performance of the proposed topologies under best coupled impedance is also verified,as the parallel system is steady when the load changes abruptly.