Research On Tri-state Quadratic Buck PFC Converter

In order to reduce the harmonic components of the input current of the switching converter,it is necessary to use Power Factor Correction(PFC)technology to make it meet the harmonic standards such as IEC61000-3-2,thereby reducing the pollution to the power grid.While controlling the phase and waveform of the input current following the input voltage,the PFC converter also needs to stabilize the output voltage of the converter to reduce the output voltage ripple as much as possible.The converter cascade technology can effectively reduce the output voltage ripple.Pseudo continuous conduction mode(PCCM)combines continuous conduction mode(CCM)and discontinuous conduction mode(DCM)to improve the load dynamic response speed of the converter.Therefore,this paper combines the cascade converter and PCCM to study the tri-state quadratic Buck PFC converter with low output voltage ripple and fast load dynamic response.In the first step,according to the different combinations of the two inductance working modes of the quadratic Buck converter,it is divided into four converters: CCM / DCM-CCM/ DCM quadratic Buck converter.The working principles of the four converters are introduced in detail.The state space average equivalent models are established respectively.The frequency domain characteristics of the control-output function are discussed,which provides a reference for the design of the converter control loop compensation network.In addition,the working area of the converter is further divided,which provides theoretical guidance for the parameter design of the quadratic Buck converter.In the second step,the four quadratic Buck converters mentioned in Chapter 2 are applied to PFC occasions,and four PFC converters are obtained: CCM / DCM-CCM / DCM quadratic Buck PFC converter.The theory derives the expressions of the input inductor current ripple of CCM-CCM / DCM quadratic Buck PFC converter and the output voltage ripple of DCM-CCM / DCM quadratic Buck PFC converter,using mean current control and the single voltage loop control strategy verified the correctness of theoretical analysis through simulation and experiment.Experimental results show that,compared with the traditional CCM Buck PFC converter,the input inductor current ripple of the CCM-CCM /DCM quadratic Buck PFC converter is significantly reduced,and the CCM-DCM quadratic Buck PFC converter is minimal;compared with the traditional DCM Buck PFC converter,the output current ripple of the DCM-CCM / DCM quadratic Buck PFC converter is significantly reduced.The final step,PCCM is introduced into the quadratic Buck converter,and the PCCM-CCM / DCM quadratic Buck converter is derived.The state space average equivalent models are established respectively,and the frequency domain characteristics of the control-output transfer function are discussed.The analysis results show that the system corresponding to the control-output transfer function of the tri-state quadratic Buck converter is the minimum phase system,and the design of the voltage control loop compensation network is simple.In addition,the above two tri-state converters are applied to PFC occasions.Using the sinusoidal current reference control strategy,the output voltage ripple is analyzed.By building a simulation model,the correctness of the theoretical analysis is verified.The simulation and experimental results show that,compared with CCM /DCM-CCM / DCM quadratic Buck PFC converter,the tri-state quadratic Buck PFC converter has smaller output voltage ripple and faster dynamic response speed of load.