Xiaotian Liu’s research while affiliated with Beijing Jiaotong University and other places

To analyse the stable operation range with varied input and output voltages, bifurcation behaviours and operation region of current-mode-controlled single-inductor dual-output (SIDO) boost converter are investigated. The inductor current borders and one-dimensional discrete-mapping model are deduced firstly. On the basis of the model, the bifurcation diagram and corresponding Lyapunov exponent spectrum are analysed. Two transition conditions and boundary equations of the converter are derived, where its working state transits from stability to instability, and its operation mode shifts from continuous conduction mode (CCM) to discontinuous conduction mode (DCM). The operation region with different circuit parameters can be estimated and divided through the parameter space maps, which is significant for the design of circuit parameters and stability control. Time-domain simulations and experimental results are presented to verify the theoretical analysis results. The research results show that the three kinds of bifurcation behaviours including period-doubling bifurcation, border collision bifurcation, and tangential bifurcation exist in the current-mode-controlled SIDO boost converters. Different from the previous works, the SIDO boost converter has a particular bifurcation trend when border collisions occur. The trend includes that operation mode shifts from CCM to DCM and then backs to CCM, and system period increases or decreases doubly.

The discrete mapping model of current-mode controlled buck converter with constant current load, taking account of composite output capacitors (parallel connection of two different types of capacitor branches, i.e. electrolytic capacitors and ceramic capacitors), is established. Based on the model, dynamical effects of varying output capacitance and equivalent series resistance (ESR) are investigated by bifurcation behaviours. The period of low-frequency oscillation among coexisting fast-slow scale instability is derived by exploring the loci of eigenvalues, while the operating regions are estimated. Time-domain simulation and experimental waveforms are provided for verification of the theoretical analysis, indicating the existences of subharmonic oscillation and coexisting fast-slow scale instability in the converter with variation of output capacitance and ESR. Research results reveal that the low-frequency oscillation can be eventually eliminated due to a relatively large (or small) ESR and the capacitance in the same branch presents to identical tendency of dynamical effects on the converter. Moreover, the interaction effects between two parallel capacitor branches are demonstrated. It illustrates that the low-frequency oscillation can be removed with smaller (or larger) ESR or capacitance in one branch of the composite output capacitors while larger (or smaller) ESR or capacitance in the other branch.