| Boost converter has been widely applied in power factor correction and photovoltaic power generation due to its advantages of continuous input current and easy to design drive circuit.With the advantages of less peripheral devices,higher reliability and more flexible design,digital control technology is increasingly applied in switching converters.Therefore,it is of significance to study the digital controlled boost converter with excellent performance.Based on the analysis of the operation principle and stability of the analog valley voltage controlled boost converter,a digital valley voltage(DVV)controlled boost converter with leading edge modulation is proposed.Its operation principle is analyzed in detail and the corresponding digital control algorithm is deduced.A sampled-data model is established to theoretically analyze the stability of the DVV controlled boost converter with lead-edge modulation.The results show that,when the equivalent series resistance(ESR)of the output capacitance is large enough,subharmonic phenomenon will appear in the system when the duty cycle D is less than 0.5.In the case of small ESR,low-frequency oscillation will occur in the full duty ratio(0< D < 1).Digital Slope Compensator(DSC)technology is introduced to eliminate the subharmonic oscillation phenomenon.The conditions that DSC should satisfy are analyzed in detail,and the digital control algorithm after adding DSC is derived.Finally,the correctness of the stability analysis is verified by simulation and experiment.Load transient response is compared with the digital voltage mode(DVM)controlled boost converter the DVV controlled boost converter with leading edge modulation has better load transient response performance.Aiming at the problem of subharmonic oscillation in the DVV controlled boost converter with the leading edge modulation,a DVV controlled boost converter with trailing edge modulation is proposed.Its operation principle is analyzed in detail,and the corresponding digital control algorithm is deduced.The sampled-data model is established and the critical conditions of the boost converter for stable operation are obtained.The system stability and load transient performance are verified by simulation and experiment.The results show that converter is in stability in full duty cycle when the ESR is large.However the low frequency oscillation phenomenon will occur when ESR is small.Compared with the DVM control,the DVV control with trailing edge modulation has better load transient performance.Based on the dual idea,the digital peak voltage control(DPV)controlled boost converter with leading edge modulation is proposed.The operation principle is studied,the digital algorithm is deduced,and the stability research is carried out.The results show that,like DVV control with trailing edge modulation,DPV control with leading edge modulation can work stably in the full duty cycle range when the ESR is large and low frequency oscillation phenomenon will occur when ESR is small.Aiming at the sampling problem in the previous three digital controls,a digital average voltage(DAV)controlled boost converter with leading-triangle modulation is proposed.The operation principle is analyzed in detail and the corresponding digital control algorithm is derived.Similarly,a sampled-data model is established and the stability condition for the system is derived.The stability analysis and load transient performance are verified by simulation and experiment.The results show that the DAV controlled boost converter can work stably in the full duty cycle range when ESR is large.Otherwise,low frequency oscillation phenomenon will occur.Compared with DVM control,the DAV control has better load transient response performance. |
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