Abstract: In a switching type DC to AC power converter a plurality (A-D, FIG. 6) of pairs of switchers (S1 and S2) are connected through inductors (L.sub.A -L.sub.D) to a load. Each set of switchers is switched to produce a square wave shaped output voltage (FIGS. 5A-5D) at a switch frequency (f.sub.S) and at a modulation percentage to produce an output voltage (E.sub.O) to a load, at a selected frequency. The sets are switched at phased delays, so that the ripple currents through them, when summed up, result in a ripple current I.sub.T at a frequency f.sub.C, where f.sub.C =n.multidot.f.sub.S, n being the number of pairs of switchers. In another aspect of the invention, means are incorporated to prevent the flow of currents between parallel connected amplifiers, characterized by zero output impedances.

Abstract: An apparatus for increasing the power conversion efficiency of electronic amplifiers into both resistive and reactive loads by means of power supply driver bias level switching. The apparatus employs a multi-level direct current voltage supply to provide multi-level biasing to output power devices. Comparator circuits continuously monitor the output voltage and compare it with the direct current multi-level bias voltage of the bias power supply. In accordance with load voltage demands, a switching circuit associated with each comparator selectively connects one of the direct current multi-level power supply voltage to the power amplifying element of the amplifier whereby the minimum voltage of the available multi-level power supply voltage sufficient to maintain operation as a class B amplifier is applied across the output driver.