A Low THD Class-D Audio Amplifier with Dual-Level Dual-Phase Carrier Pulse-Width Modulation

in this paper, a class-D audio amplifier which combines the advantages of the phase shifted carrier (PSC) PWM and the multiple level carrier (MLC) PWM is proposed with a dual-level dual-phase carrier (DLDPC) PWM. The proposed closed-loop amplifier includes a 2nd order integrator and a DLDPC triangular wave generator. Two sets of 180° out-of-phase triangular waves are used as carriers, and each set has its respectful offset voltage level with non-overlapping amplitude.

By performing the double Fourier analysis, it can be found that the linearity can be enhanced and the distortion can be reduced with the proposed modulation. Experimental results shows that the proposed fully differential DLDPC PWM class-D audio amplifier features a total harmonic distortion (THD) lower than 0.01% with an output voltage swing of +/− 5V.

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