A high efficiency single-stage switching amplifier based on high-frequency link inverter is proposed. Bipolar phase shift modulation is adopted in the proposed switching amplifier. Auxiliary circuits including freewheeling diodes, clamp capacitors and active clamp bridge (ACB) are added to provide a current flowing path for the inductor current during the dead time of the bidirectional switches. The ACB is synchronised with primary-side switches to absorb the leakage inductor energy and clamp the secondary-side transformer voltages. With single-stage conversion and leakage inductor energy recycle, high efficiency of the proposed switching amplifier is achieved. A 5 V/25 W prototype is presented to verify the analysis results of the proposed switching amplifier.

A novel soft-switching step-up/down DC-DC converter is proposed, which generates symmetric bipolar outputs while maintaining the grounded capability. The proposed converter consists of a zeta converter cell and a buck-boost converter cell, sharing an inductor and a power switch. High efficiency is achieved by zero voltage switching for all switches. Meanwhile, by connecting one load between positive and negative output terminals, high voltage gain can be achieved. Experimental results of a 3.7 V battery input and ±10 VDC/10 W outputs prototype are presented to verify the analysis results of the proposed converter.

A novel full-range soft-switching full-bridge (FSFB) cycloconvertertype high-frequency-link inverter (CHFLI) with active snubber network is proposed. By adding an auxiliary inductor in primaryside DC/AC converter and adopting centre-tapped transformer structure, the proposed FSFB-CHFLI achieves zero voltage switching (ZVS) for all switches under different operating conditions from light load to rated load, which benefits with high efficiency and high switching frequency. The secondary-side active snubber network is utilised to recycle leakage inductor energy and suppress voltage spikes caused by the resonance of the leakage inductor and the parasitic capacitance of switch. The commutation overlap strategy is adopted to guarantee complete ZVS turn-on and ZVS turn-off of bidirectional switches. Experimental results of a high efficient and high switching frequency (200 kHZ) prototype are presented to verify the analysis results of the proposed FSFB-CHFLI.

A two-channel single-stage switching amplifier (SSA) based on highfrequency link inverter is proposed. The audio input signals are modulated by phase shift between primary-side switches and secondary-side switches, thus independent amplifications of two channels can be obtained. Benefiting from multiplexing of primary-side power switches for two channels, only a half bridge inverter is utilised at primary side. Clamp circuits at the secondary side of transformer eliminate spike voltages across the secondary-side switches during the current commutation of the cycloconverters. Zero voltage switching of primary-side switches and clamp switches are achieved by utilising magnetising inductor current. A 320 V/250W prototype is presented to verify the analysis results of the proposed two-channel SSA.