Class D audio amplifier with hybrid control

R-modeled speaker fed by sliding mode(SM) controlled half bridged audio amplifier(HBA) show significant phase difference between reference voltage and speaker current. The causes of phase difference possibly are inaccurate speaker model and phase lead/lag introduced by the output filter. To investigate phase difference, the transfer function of HBA and approximated first order model of the speaker were considered. With the aim of eliminating the phase difference between reference voltage and speaker current, a hybrid approach comprising SM controlled amplifier with linear control technique is proposed in this paper. The prototype sliding mode controlled amplifier of 20 W, 20 Hz to 20 kHz with 4/8 Ω speaker load is developed. Frequency response and experimental results with the prototype are experimentally obtained which show excellent command following of the speaker current with minimal phase lag.