The Design Of 3W Class D Filter-free Audio Power Amplifier

In this thesis, the design of class-D audio power amplifier is based on the original in the laboratory, according to the audio amplifier principle, the specific module circuit structure and parameter optimization of the design.Class D audio power amplifier compared with other types of power amplifier has significant advantages in terms of efficiency. In today’s era of highly developed mobile devices, battery capacity has become a bottleneck in the development of mobile devices, so Class D audio power amplifier under the background of the rapid development of mobile devices has a broad space for development.This thesis firstly introduces the research background and current status of the audio amplifier, then describes the principle and characteristics of various types of audio power amplifier, highlighting the great advantage of Class D audio amplifier in terms of efficiency and studied filterless Class D audio power amplifier principle, and applied in this paper.This thesis adopts smic0.18 um technology to design the audio amplifier amplifiers, comparators, PWM modulator, reference circuit and over temperature protection circuit, describes the principles and circuit-level analysis and design,and functional verification using the spectre software.The amplifier uses a two sleeve-type structure, and use the stable frequency characteristics of Miller compensation principle, this amplifier has a high gain the advantages of high-swing to meet the requirements of the pre-amplifier; comparators introduced a large prevention latched comparator,taking the transmission characteristics of per-amplifier advantages and the transmission characteristics of latches advantages, to design a high-speed comparator structure.Designed a 250 KHZ oscillation for PWM modulation,, this oscillator by a control circuit and control the charging and discharging of the capacitor to get the shock of the triangular wave; designed a new type of benchmark circuits to ensure temperature characteristics of stable output at the same time increasing the driving capability of the output voltage, taking into account the frequency stability characteristics; over-temperature protection circuit is designed to ensure that the chip under abnormal operating conditions of reliability.Finally, this thesis introduce the considerations when draws the layout,mainly analyzes the issues of matching, noise, isolation protection, layout,etc., and gives specific design methods.In this thesis, after the completion of the above work,through these modules careful simulation, results show that at 3.3V supply voltage, load 2Ω, operating temperature of 25 °, the chip efficiency reached 82%, power is 3W, harmonic distortion is less than 1.4%,meet the performance requirements.