High precision switched mode amplifier with an auxiliary bias circuit

Blanking time, also referred to as dead-time, is one of the dominant sources of output current and voltage distortion in pulse-width modulated power amplifiers. Extensive studies are known on elimination, minimization, and compensation of the effect. Most techniques achieve a reduction of the distortion but are not capable of completely removing it. Topologies like the opposed current converter do not require dead-time and therefore do not suffer from this nonlinear effect. In order to ensure continuous conduction mode, opposed current converters require bias current that normally flows through the output filter inductors. This paper presents an alternative approach where the bias current is supplied from additional current controlled switching legs. A modulation strategy is proposed and guidelines are given for the design of the inductive components. Finally the inductor volume of the proposed topology is compared to the opposed current converter equal showing that both topologies are comparable with respect to volume of the passive components.