Research On Topology Of Wide-input High Step-down Ratio DC-DC Converter Based On Tapped-inductor

With the rapid development of big data,artificial intelligence and 5G technology,the power consumption of data center servers has increased by more than 12% every year.Therefore,it is imperative to improve the energy efficiency of the data center power supply system and build a green and energy-saving data center.In the 48 V bus power supply architecture of the data center,the single-stage converter can effectively overcome the shortcomings of high line loss and component redundancy of the two-stage converter.Scholars at home and abroad have conducted extensive research on this,and proposed isolation and non-isolation.various DC/DC converter topologies.Although these topologies can achieve high efficiency in high step-down ratio applications,there are still problems such as low efficiency,limited voltage regulation capability,and large electromagnetic interference when the input voltage fluctuates in a wide range.Tapped-inductor converters have a simple step-down method and soft switching capability,while buck-boost converters are often used as front-end voltage pre-regulators to handle wide input voltages.In this thesis,a wide input-high step-down ratio buck-boost converter based on tapped-inductaor is proposed,which can combine the advantages of the above two converters to achieve high efficiency of single-stage converters under wide input voltage,and provides new research ideas for improving the energy efficiency of data center power supply.The main contents of this article are as follows:In order to construct a high-efficiency wide input-high step-down ratio tapped-inductor converter,based on previous work,this thesis firstly studies the structuring laws of the tapped-inductor buck converter topology with three characteristics of high step-down ratio,soft switching buffer,no DC bias.Based on the above research,starting from the buck-boost converter,this thesis constructs a wide input and high step-down ratio buck-boost converter topology based on tapped-inductor step by step.Its voltage gain characteristics show that the constructed topology can keep the duty cycle in a suitable range under wide input voltage to maintain the efficient operation of the converter.In order to study the steady-state characteristics of the proposed converter,this thesis analyzes and compares the two operating modes of the proposed converter in detail,CCM and CRM;derives and analyzes the voltage gain and steady-state capacitor voltage of the converter;then analyzes the excitation inductance and the DC component and AC ripple of the output inductor current;then the effects of leakage inductance on the step-down energy,freewheeling time and soft-switching performance of the converter are discussed.Through the above analysis,the wide input,high step-down ratio,soft switching buffer and no DC bias characteristics of the proposed converter are verified,and the nature of the converter is revealed.Finally,the performances of the proposed converter and the same type of converters are compared in terms of the number of components and soft-switching performance.The comparison results show that the converter proposed in this thesis has advantages in terms of component number and cost.In order to study the dynamic characteristics of the proposed converter,this thesis first discusses the applicability of the modeling method by analyzing the natural resonant frequency of the converter.A small signal model is established based on the state space averaging method.The PSIM frequency sweep curve shows that the state space averaging method is used.The method is fitted with the simulation results,which verifies the correctness of the modeling method;the closed-loop control model of the converter is established in the discrete domain,and the digital controller is designed based on this.The dynamic simulation results of PSIM show that the designed digital controller can be effectively guarantee the dynamic performance of the converter.Finally,an experimental prototype with an input of 36V～60V,an output of 3.3V and a load of 1～10A was made.The results show that the experimental waveforms are consistent with the theoretical analysis,the converter can maintain high efficiency under wide input voltage,the efficiency range remains above 90% under all operating conditions,and the highest efficiency is 95.8%.