Dual mode control of tri-state boost converter for improved performance

Abstract

A tri-state boost converter with an additional boost-inductor free-wheeling interval was proposed earlier to eliminate the Right-Half-Plane (RHP) zero that occurs in the control-to output transfer function of a classical boost converter under continuous-conduction mode of operation. A 'constant-Do' control scheme, in which the 'capacitor-charging' interval of the converter was kept constant, was employed. This resulted in a relatively large inductor current, especially under high line and load conditions, thereby causing high circuit losses. This paper proposes two variations of a novel dual-mode control (DMC) scheme that vary both the 'boost' and the 'capacitor charging' Intervals. Control analysis, design, and limitations of the proposed DMC schemes are presented. Through computer simulations and hardware experiments the performance of the tri-state boost converter with DMC schemes are compared with those of the tri-state boost converter with 'constant-Do' control scheme, and the classical PI-controlled boost converter. The DMC schemes achieve a significant (about 10%) improvement in converter's efficiency for a wide load range over the 'constant-Do' control scheme.