An Efficient And Low Distorded Class D Audio Power Amplifier Based On RWDM Control

Compared with traditional analog audio power amplifier(Class A、B、AB), digital class D audio amplifier have features of small size, high efficiency, low distortion, high-power, green energy-saving. Currently, Class D has been widely used in portable electronic products such as MP3, PDA, CD, DVD.A digital Class D power amplifier used in audio electronic products is designed. Firstly, a systematic description of the principles of audio power amplifier. Then, the mainstream modulation technique of the three audio amplifier are compared and their advantages and disadvantages are analyzed. The principle of RWDM(rectangular wave delta modulator) control modulation is in detailed analysis. A system-model is created and the system parameter formula such as system gain, switching frequency, PSRR( Power Supply Rejection Ratio). Considering the Circuit performance, pair modules are in detailed analysis and the main functional modules are simulated, which contains band-gap reference, RWDM controller, LDO(low dropout regulator), output stage driver circuit.The design was implemented with a 0.35μm BCD process under the environment of cadence. The circuit support a single power input range from 9 to 24 V with power input at 24 V, Load Resistance of 4Ω,the chip can achieve PSRR at 60 dB, output power of 20 W, power efficiency about 90%, total Harmonic Distortion+Noise(THD+N)less than 1%.