摘 要
放大器對一個音響系統扮演著很重要角色. 在目前音響系統中市場仍以AB類放大器為主要設計. 若以功率效益方面來比較, D類放大器有較優越的輸出功率表現. 主要是因為D類放大器是以切換的方式來完全導通或是完全關閉電晶體. 因此D類放大器可以擁有較少的功率消耗.

本論文重心著重於發展一種高功率效益D類放大器的調變方法. 本電路是使用TSMC 製程0.35 2P4M(混合訊號)來模擬與設計. 整個系統架構包括 “二個誤差放大器”, “二個比較器”, “三角波產生器”, “緩衝器”, “閘極驅動級”, “H-橋”等電路方塊.

經由各種調變設計結果與模擬, 可明白比較出四種調變方法的優缺點. 若欲使THD < 1 %, 則最好選擇輸入訊號振幅為載波訊號振幅的0.7倍以內會有較佳結果. 實際上, 一般D類放大器功率效益大約是在85 % ~ 95 %. 若要再提高D類放大器的功率效益則必須用較大的晶片面積來換取.

Abstract
Amplifiers play an important role in audio system. Class-AB amplifiers seem to be the dominative design in recent market. Compared to power efficiency, class-D amplifiers have better performance than class-AB amplifiers. It is based on the fact that class-D amplifiers use the switching operation to fully turn on or off the transistors. Class-D amplifiers have less power dissipation than class-AB amplifiers.
The focus on this thesis is to develop the modulation of class-D amplifier with high power efficiency. This circuit uses TSMC 0.35 2P4M (Mixed-Signal) process to design and simulate. It includes two error amplifiers, two comparators, triangular wave generator, buffer, gate-driver, and H-bridge.
All the modulation simulations are shown in this thesis, and we can obviously compare their advantages and disadvantages. If THD < 1 % is desired, then it’s better to choose the amplitude of the input signal to be within 0.7 times of the carrier wave. In fact, the power efficiency of class-D is about 85 % to 95 % generally. If we still want to increase the power efficiency, then we must make our mind to balance the power efficiency against the chip size.

[1] T. F. Chen, Plano, M. Corsi, Parker, R.C. Jones, Dallas, M. D. Score, Richarson, “Modulation scheme for filterless switching amplifiers,” Texas Instruments Incorporated, Dallas, United States Patent
NO. 6,211,728, Apr.3, 2001
[2] MAX9712 Datasheet, “500mW, Low EMI, Filterless, Class D Audio Amplifier,” Maxim, Aug. 2003
[3] Chiew Tiam Boon, “Switch Mode Multilevel(Class D) Power Amplifier,” University of Queensland, Department of Electrical and Computing Engineering, Oct,2001
[4] M. Corsi, Allen, T. F. Chen, Plano, R.C. Jones, D. Mavencamp, Brandon, K. Arcudia, Ridgeland, “Concept and method to enable filterless, efficient operation of class-D amplifiers,” Texas Instruments Incorporated, Dallas, United States Patent NO. 6,262,632, Jul.17, 2001
[5] W. Marshall Leach, Jr., “Introduction to Electroacoustics and Audio Amplifier Design, Second Edition,” published by Kendall / Hunt, 2001
[6] Don Dapkus, Robin Chen Texas Instruments, Inc, “High-Efficiency Audio Amplification Using Class-D Audio Power Amplifiers,” Texas Instruments, Inc, 1999

[7] Jeffrey D. Sherman, “Class D amplifiers provides high efficiency for audio systems,” Harris Semiconductor, May 25, 1995
http://archives.e-insite.net/archives/ednmag/reg/1995/052595/11df3.htm#pic1
[8] Don Dapkus, Kenny Han, Texas Instruments, Inc, ”Utilizing class-D audio power amplifier for high efficiency,” Texas Instruments, Inc , 2000
[9] TNG CHEE WAN, “Multi-level Switch Mode Class D Amplifier,” University of Queensland, Department of Electrical and Computing Engineering, Oct, 1998
[10] Texas Instruments, “Reducing and Eliminating the Class-D Output Filter,” Aug. 1999
[11] Mellor, P.H. & leigh, S.P. & cheetham, BMG, Reduction of spectral distortion in a Class D amplifiers by an enhanced Pulse width modulation sampling process, IEEE proceedings-G, Vol. 138, No. 4, August 1991
[12] P. H. Mellor, S. P. Leigh and B. M. G. Cheetham, “Digital sampling process for audio class-D, pulse width modulated, power amplifier,” Electronics Letters 2nd January Vol. 28 NO. 1
[13] Ronan A. R. van der Cee, Ed (A. J. M.) van Tuiji, “A Power-Efficient Audio Amplifier Combining Switching and Linear Techniques,” IEEE J. Solid-State Circuits, vol. 34, Jul. 1999

[14] Black, H.S. Modulation Theory, Princeton, NJ, Van Nostrand, 1953, pp.261-281
[15] Soo-chang Choi, Jun-woo Lee, Woo-kang Jin, Suki Kim, “10-W Single-Chip Class D Power Amplifier With Very High Efficiency For Audio Applications,” Department of Electronics Engineering. Korea University, 1999
[16] Eugene Blanchard, “MOSFET H-bridge schematic and theory of operation,” http://www.cs.uwa.edu.au/~mafm/robot/blanch-h-bridge.html, Dec. 19 1995
[17] Sayed-amr El-Hamasy, Design of high efficiency RF Class D power amplifier, IEEE transcaton on power electroincs, Vol9, No.3, 1994, pp.298-301
[18] Texas Instruments, Application report for “Design Consideration for Class-D Audio Power Amplifiers,” http://www-s.ti.com/sc/psheets/sloa031/sloa031.pdf, August 1999
[19] Michael D. Score, Richardson, Paras M. Dagli, Roy C. Jones, III, Plano, Wayne T. Chen, “Modulation scheme for filterless switching amplifiers with reduced EMI,” Texas Instruments Incorporated, Dallas, TX(US), United States Patent NO. 6,614,297, Sep. 2 2003
[20] Christopher N. Hemmings, “Improving Class D Audio Power Amplifiers,” University of Queensland, St Lucia, Department of Computer Science and Electrical Engineering, 1999
[21] Cheng, Z, Analysis and design of a micropower low voltage Class D audio amplifier, Master thesis, Nanyang Technology university, Singapore 1995
[22] Texas Instruments, “Application report for Design Consideration for Class-D Audio Power Amplifiers,” http://www-s.ti.com/sc/psheets/sloa031/sloa031.pdf, August 1999
[23] Brain E.Attwood, .Design Parameters Important for the Optimization of Very High-Fidelity PWM (Class D) Audio Amplifiers., Journal of Audio Engineering Society, vol.31, no.1, November 1983, pp.842-853
[24] Charles L. Philips & Royce d. Harbor, “Feedback control system (3rd edition ),” pp.128-129
[25] Zheren lai and keyue M. smedley, “A low distortion switching audio power amplifier,” IEEE transaction on industrial Electronics and under control instrument, June 1995, pp.174-180
[26] John M. Murray, “Design consideration on Class D MOS power amplifier,” IEEE transaction on electronic and control instrumentation, Vol. EECI-26, NO. 4, Nov 1979
[27] National Semiconductor, Data sheet for LM4651 & LM4652 OverureTM Audio Power Amplifier170W Class D Audio Amplifier Solution, http:// www.national.com/pf/LM/LM4651.html#Datasheet, August 2000
[28] Brain E.Attwood, “Design Parameters Important for the Optimization of Very High-Fidelity PWM (Class D) Audio Amplifiers,” Journal of Audio Engineering Society, vol.31, no.1, November 1983, pp.842-853
[29] Duncan McDonald, Class D audio-power amplifiers: Interactive simulations assess device and filter performance, http://www.e-
insite.net/ednmag/index.asp?layout=article&articleId=CA60948&stt=001, April 2001
[30] Harris Semiconductor, Data sheet for HIP4082 H-Bridge FET driver, http://www.farnell.com/datasheets/4477.pdf, March 1995
[31] National Semiconductor, Data Sheet for LM361 High Speed DifferentialComparator, http://www.national.com/ds/LM/LM161.pdf, August 2000