LLC-Based Resonant Single-Stage PFC Converter

The traditional switching power supply uses a diode rectifier bridged bulk capacitor as the front stage,and the current drawn from the AC input side is non-sinusoidal due to the presence of large capacitance.Non-sinusoidal input currents generate a lot of undesired harmonic currents during the transmission of energy.The presence of these harmonic currents degrades the power quality of the AC grid side,while also reducing the reliability of the downstream equipment.Causing potential pitfalls.In order to ensure a safe power environment,a power factor correction link needs to be added to the switching power supply.Conventional solutions often have the disadvantages of large bus voltage stress,complicated circuit structure,and high operating frequency.In order to solve these problems,this thesis proposes a single-stage resonant PFC(Power Factor Correction,PFC)converter.The single-stage PFC converter proposed in this thesis is based on LLC resonant converter.The output voltage is regulated by the output voltage external loop compensation control.At the same time,the output of the outer loop is multiplied by the input voltage waveform to form the input current reference.The current inner loop compensation control implements input power factor correction.The converter proposed in this thesis does not have the Boost of the previous stage,and there is no problem of large bus voltage stress;the single-stage circuit structure is adopted,the circuit is simple and low in cost;and the soft switching characteristics of the LLC are retained,and the high frequency can be realized and thus reduced.The switching loss of the small system is beneficial to the further optimization of the system.This thesis firstly determines the theoretical basis of the LLC resonant converter as a PFC circuit by analyzing the gain characteristics of the LLC resonant converter.Then,through the modal analysis of the single-stage PFC,the steady-state analysis is carried out by the fundamental component model,and the dynamic characteristics of the circuit are analyzed by the small-signal model.Then the parameter optimization design steps are analyzed and verified by simulation.Finally,the modules of the proposed single-stage PFC converter are designed,including the design of magnetic components and the selection of power components,the design of DSP control system,the design of drive circuit,the design of sampling and conditioning circuit,and the design of protection circuit.Etc.,and made a prototype to verify the correctness of the theoretical analysis of the proposed converter.