Digital Voltage-mode Control Technique Of Switching Converter With Dual-edge Modulation

Pulse width modulation(PWM)of switching converter can be divided into single-edge modulation and dual-edge modulation.The majorities of PWM method are single-edge modulation in existing publications and make little use of dual-edge modulation.Dual-edge modulation not only possesses the merit of single-edge modulation,but also reduces the defect of single-edge modulation.Therefore,it is significant to research how various PWM methods affect performance of switching converter.Combining the dual-edge modulation and digital voltage-mode control,the stability of digital voltage-mode controlled switching converter with dual-edge modulation is investigated,taking buck converter as an example.Its discrete iterative-map model is established and nonlinear dynamic behavior is researched by numerical simulation.Through observing the bifurcation diagram,it is indicated that there are two kinds of similar but different Hopf bifurcation phenomenon in digital voltage-mode controlled switching converter with dual-edge modulation.The two kinds of Hopf bifurcation are analyzed by time-domain simulation and Poincare section.The Jacobian matrix is deduced,whose eigenvalues are acquired.The difference of two Hopf bifurcations is investigated in theory with the different location and direction of eigenvalues.In addition,it is observed that the odd period-doubling bifurcation phenomenon exists,which changes from period-1 to period-3,in digital voltage-mode controlled buck converter with dual-edge modulation.Through the simulation and experiment,the existence of odd period-doubling bifurcation is verified by time-domain waveform and phase portraits.Through unifying the different PWM methods,the stability of digital voltage-mode controlled switching converter with unified PWM methods is investigated,whose discrete iterative-map model is established.Through the numerical simulation and time-domain simulation,Hopf bifurcation and period-doubling bifurcation are observed and the stability effected by modulation method is analyzed.The closed-loop z-domain transfer function is established.The system eigenvalues are obtained by solving the characteristic equation of the transfer function.Furtherly,the existence of Hopf bifurcation and period-doubling bifurcation are examined.Mathematical formula of stability boundary is deduced,which is used to describe the state region distributions of the converter.Through the formula and the state region distributions,it analyses how modulation method affects the stability of converter from the theoretical view.The adjusting range of modulating wave parameter and compensator parameter are acquired.The derived formula and the plotted state region distributions are significant to provide guidance for circuit parameters.Finally,combining dual-edge modulation and double-loop voltage-mode control,digital average-voltage controlled switching converter with dual-edge modulation is investigated,whose operation principle is analyzed and duty ratio algorithm is deduced.The closed-loop z-domain transfer function is established and the eigenvalues are acquired by solving the transfer function.Comparing the location of eigenvalues and unit circle,it analyses how equivalent series resistance of capacitor affects the stability of digital average-voltage controlled buck converter.Through circuit simulation,comparing digital average voltage,digital peak voltage,digital average current and digital voltage-mode control methods,the digital average-voltage control possesses better load transient performance and steady accuracy of output voltage.In addition,there is no subharmonic oscillation in digital average-voltage controlled buck converter when the duty ratio D>0.5,which possesses better stability.