Based on the difference close-loop feedback technique and the difference pre-amp, a high efficiency PWM CMOS class-D audio power amplifier is proposed. A rail-to-rail PWM comparator with window function has been embedded in the class-D audio power amplifier. Design results based on the CSMC 0.5μm CMOS process show that the max efficiency is 90%, the PSRR is -75 dB, the power supply voltage range is 2.5-5.5 V, the THD＋N in 1 kHz input frequency is less than 0.20%, the quiescent current in no load is 2.8 mA, and the shutdown current is 0.5 pA, The active area of the class-D audio power amplifier is about 1.47 × 1.52 mm^2. With the good performance, the class-D audio power amplifier can be applied to several audio power systems.
A buck DC/DC switching regulator is implemented by automatically altering the modulation mode according to the load current that ranges from 0.01 to 3A. The pseudo-PFM mode is applied when duty cycle is less than 20% ,and the PWM mode is selected in a range of duty cycle from 20% to 100%. The average conversion efficiency of the regulator is about 90% when the output current varies. The proposed dual-mode-control die is implemented in a 0.5μm DPDM CMOS mixed-signal process and a power p-MOSFET is used in the chip by hybrid integration.
