Class D Audio Power Amplifier Design Based On The Bcd Process

In recent years, with the increasing popularity of portable multimedia products, product sizes become lighter and thiner. Therefore, in the choice of power amplifiers, the non-liner class D audio power amplifier is the most appropriate one, which has characteristics of high efficiency, low heat, low power consumption and long battery life. Based on the reserches of current domestic and international mainstream class D audio power amplifier system designs and implementation techniques, this paper designed a 6W stereo dual-channel filter-free class D audio power amplifier. In the design process, traditional PWM modulation method was improved. The improved modulation eliminated the disadvantage of low efficiency for the traditional modulation of system and achieved the design of class D power amplifier without filter. Filter-free design reduced the external components, greatly saved the size of system, can reduce system costs by about 40%.In circuit design, firstly introduced the class D audio power amplifier system composition and working principle. Then, separately designed the main circuit modules of class D audio amplifier. Useing fully differential input op-amps, fully differential integrator, reduced the common-mode voltage requirements, eliminated the need for external BYPASS capacitors and input coupling capacitors. For the PWM modulation, improved modulation scheme improved output efficiency, designed comparator circuit, level shift circuit, over temperature protection circuit.Finally completed the whole circuit function simulation, the typical electrical characteristic simulation, assisted to finish layout design, and manufactory. The test results shew that when load is 8Ωload and supply voltage is 12V, output power was 6W/CH, the output efficiency was up to 92%, voltage supply range was 8.5V ~ 18V, PSRR was -70dB (20~1kHz), CMRR was -50dB (20~1kHz), THD+N was 0.1% (1W, 1kHz, RL=8Ω).