Research On High Order Resonant Converter Based On Swtiched Capacitor Buck Front End

In the new era,China attaches great importance to ecological security,and has put forward a middle and lonterra aim of peaking carbon dioxide emissions by 2030 and carbon neutrality by 2060.In the field of energy applications,electrification is the best choice undoubtedly.Among so many DC-DC converters,the resonant DCDC converters represented by LLC have the advantage of wide range and high efficiency and has become one of the best choices in the medium and high power applications.However,during the design and application,Engineers gradually discovered that conventional LLC resonant converters still have many problems in terms of voltage gain,input range,and light-load efficiency.Based on LLC,this topic proposes a new solution of combinating switched capacitor converter with the highorder resonant network to design a high-frequency efficient DC-DC converter.For the switching loss caused by excessive switching frequencies and excessive reactive cycles when LLC under high input voltage or light load conditions,the switched capacitor is proposed as buck front end of the resonant network.Conventional LLC resonance converters need to increase the switching frequency to a very high frequency band in high input voltage or light load conditions,which not only increase the switch loss,but also makes the resonant network become strong inductive.This makes a large sensive reactive current on the line,causing greater pacing loss.The proposed switched capacitor buck front end circuit can achieve a ?step-down and reduce the buck ratio of resonant converter.So that the resonance network frequency does not need to rise to high,thereby increasing the efficiency of high input voltage and light load conditions.On the other hand,the cascade of the switch capacitor circuit and the resonant network are also effectively achieved soft charge and controllability of the switched capacitor circuit.Use the five-order resonant network instead of the conventional third-order network.High-order networks more excellent resonant characteristics to further address the wide range of frequencies in wide input and wide output applications,low adjustment resolution and pandid state and switching loss.Use the five-order resonant network instead of the conventional third-order network.Use a higher-order network which has a more excellent resonant characteristics further to solve questions of the frequency adjustment range in the wide input and wide output applications,low adjustment resolution,conduction loss and high switch loss.The five-order resonant network has three more distinctive resonance points.Three harmonic outputs can be superimposed on the output,and can greatly reduce the frequency adjustment range and have good soft start characteristics.For the switch capacitance link and the high-order resonant network adopted,the ultra-limit frequency method and the FHA base wave analysis method are separately used to studied it,and the switch capacitance equivalent output model and the direct current voltage gain characteristics of the high-order resonant network are obtained.The principle of high-order resonant converter efficiency improvement was then studied from two angles of reactive cyclic flow and rectification loss.The parameter design scheme of the converter is proposed according to the DC gain characteristics of the switch capacitance equivalent model and the high-order resonant network.The design of the plane transformer is completed by the AP method and is optimized for its winding structure.The parameter dispersion of the high-order resonant network was then studied.Then make up for the error brought about by ideal conditions and device parametric parameters in theoretical analysis,and provided a reference basis for the adjustment of the actual hardware circuit parameters.In order to achieve the output voltage closure,the small signal model of the switch capacitor circuit and the resonant change circuit is established by the limit frequency method and the extended description function method,and the high-order compensator is designed to improve system stability and control accuracy.According to the charging characteristics of the switch capacitor and the notch point in the gain curve,the corresponding soft start scheme is established,and the system has stable and reliable closed loop operation.Finally,by building an input range of 300-450 V,the constant voltage output 12 V,the rated power 100 W,the test prototype platform with 93.7% of the rated operating point efficiency can be realized to verify the correctness of the theoretical.