Abstract: In order to improve driver efficiency,a high power supply in the design of class-D audio power amplifiers is needed to drive the high-side LDNMOS of H-bridges.A novel driver circuit is presented to solve this problem.A charge pump circuit is used in the design.With the operation of the chip,the power supply for the low-side LDNMOS transistor of the H-bridge is clamped at 5.5V by a charge pump capacitor,and the power supply for the high-side LDNMOS transistor of the H-bridge reaches 18.8V by a bootstrap capacitor.The bootstrapped power supply minimizes the number of high-voltage power-supply levels externally supplied to the system and improves the efficiency.A stereo class-D audio power amplifier with this circuit is implemented in a TSMC06BCD process.The results indicate that its efficiency could be as high as 89.67%,and the high-side and low-side RDSON is 320mΩ,PSRR is -62dB,and its THD is as low as 0.1%.This shows that the circuit works effectively.

Key words: class-D APA, H-bridge, charge pump, bootstrapped capacitor, efficiency