A Low THD Class-D Audio Amplifier with Harmonic Reduction

In this prroject, a class-D audio amplifier which combines the merits of the phase shifted carrier and the multiple level carrier. The proposed closed-loop amplifier includes a 2nd order integrator and a DLDPC triangular wave generator. High quality audio amplifiers should exhibit high power efficiency, while maintaining satisfying high fidelity to the human ear at the same time. 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 feature a total harmonic distortion is lower than 0.01% with an output voltage swing of +or− 5V.