A Class D Amplifier with High Efficiency and Low Distortion for Audio Application

• Main Authors: Pang-Chan Hung, 洪邦楨
• Other Authors: Po-Chiun Huang
• Format: Others
• Language: en_US
• Published: 2007
• Online Access: http://ndltd.ncl.edu.tw/handle/41325713491922204721

碩士 === 國立清華大學 === 電機工程學系 === 95 === Abstract Instead of traditional class-AB amplifier, class-D amplifier is gradually used in audio application. Class-D amplifier itself is high efficient but non-linear structure. Many feedback solutions to reduce analog-input class-D amplifier non-linearity are revealed in recent years. However, the feedback system is hard to be used at digital-input class-D amplifier. In this thesis a modified class-D amplifier topology is proposed to solve the total harmonic distortion problem of digitalinput class-D amplifier. The basic operation of class-D amplifier is introduced in the first part. Several modulation methods are discussed and compared. The theoretic and practical views, especially on non-linear effects are discussed in the following. Based on these analysis, a hybrid modulation scheme is proposed. It uses the hysteresis concept to solve the pulse timing and amplitude error. To verify the availability of the proposed structure. a digital PWM inputted output stage is prototyped using TSMC 0.35 2P4M (Mixed-Signal) process. Simulation results show the nonlinearity can be improved by pulse width delta modulation. Measured data indicates that the improvement in nonlinearity issue. Although there are some non-ideality like blanking delay error to be solved, the experiment result has demonstrated that the proposed pulse width delta modulation analytical and technique can efficiently reduce the non-linearity of output loading and timing error. The total harmonic distortion can be improved from 35dB to 55dB. The full system can work on a 8ohm 2watt general speaker.