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This paper presents a simple methodology to convert a hard-switched pulse-width-modulated (PWM)-bridge converter used in a classical digital audio amplifier into a zero-voltage-switching (ZVS) converter. The ZVS is simply achieved by connecting an-series branch across the converter output. ZVS occurs during the dead time interval of the PWM signals, giving an effective improvement in the conversion efficiency, output frequency spectrum, and total harmonic distortion. A simplified design procedure is provided for choosing the value of the components. A prototype digital amplifier with an output power of 20 W and switching frequency of 705.6 kHz has been implemented. Experimental results are presented and favorably verified with theoretical predictions.

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This paper presents the derivation of a generic analytical solution for calculating the harmonic characteristics of multilevel sinusoidal pulse width modulation (SPW-M) inverter. This generic solution has advantages over previously published solution since the phase shifts of all the carriers can be made arbitrary. This feature gives a high degree of freedom for evaluating the harmonic structure of a multilevel SPWM inverter with different carrier phase combinations. A multilevel SPWM \vaveform is decomposed into a series of positive and negative DC biased PWM (DBPWM) waveform. A 3-dimensional modcl for describing each individual DRPWM is first derived. After applying the double Fourier series to each waveform, the multilevel SPWM output is then obtained by summing all the DBPWM outputs. The validity of the solution is verified using Pspice simulations.

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