無濾波器D類音訊放大器

Design of Filterless Class D Audio Amplifier

蔡俊豪(Chun-Hao Tsai)

指導教授 ： 陳怡然

國立臺灣大學/電機資訊學院/電機工程學研究所/碩士(2007年)

https://doi.org/10.6342/NTU.2007.10079

摘要

近些年來，商業用音訊放大器之應用以AB類放大器為主。然而AB類放大器之功率效能最大不會超過70%，功率損耗大都以熱散逸的型式進而降低電池之使用時間。由於D類放大器擁有高效能之特性，也因此近年廣範的被研究與討論。
傳統脈波寬度調變技術運用在D類放大器時，在輸出級必須要有一組濾波器，這會造成整體面積和成本上的增加。因此，我們利用單極性切換脈波寬度調變技術去實現無濾波器之D類放大器。本論文著重於使整個D類放大器電路皆可以積體電路之方式實現。我們注意到由於三角波邊緣線性度不夠而造成總諧波失真上升的情形。可藉由利用負回授的機制來抑制總諧波失真過高的問題。
放大器電路的設計是由台積電2P4M 0.35uｍ的CMOS製程進行模擬，其操作電壓為3.3V。整個無濾波器D類音訊放大器電路包含一個誤差放大器、兩個遲滯比較器、一個三角波產生器、閘級驅動電路和H橋輸出級電路。整個內部電路的細節在本論文中都會有敘述與討論。當我們給予一個振幅為0.4V且操作頻率在1KHz之正弦波為輸入信號時，我們可以得到最大的總諧波失真為0.13%以及功率效能為88.5%。

關鍵字

D類放大器 ； 脈波寬度調變 ； 音訊放大器

並列摘要

Over the years, the commercial audio amplifiers are dominated by Class AB amplifier. However, most of Class AB amplifier power efficiency is below 70%, which reduces the overall system battery lifetime and increases the heat dissipation. Therefore, the Class D amplifier with the advantages of high efficiency has been widely investigated recently comparing to the Class AB amplifier.
A Class-D amplifier with conventional PWM modulation requires an output filter which needs large area and increasing cost. Therefore, we use unipolar switching pulse width modulation scheme to realize a filterless Class-D power amplifier. In this thesis, we focus on the implementation of Class D amplifier on a monolithic integrated circuit. We observed that the total harmonic distortion (THD) increases due to non-linearity in the triangular wave. To overcome this problem, negative feedback is applied to reduce the harmonic distortion.
The circuit is designed using TSMC (2P4M) 0.35um 3.3V CMOS process. The entire circuit contains an error amplifier, two hysteresis comparators, a triangular wave generator, gate-driver circuits, and the H-bridge. The details of the entire circuit will be described thoroughly in this thesis. When a 0.4V, 1KHz input sine wave is applied, the maximum THD is 0.13% and the efficiency is 88.5%.

並列關鍵字

Class-D Amplifier ； PWM ； Audio Amplifier

參考文獻

[6]陳勝彥, ”無線通訊射頻功率放大器的線性化技術-LINC” 國立台灣大學電信工程學研究所, 2006.

[1]Helmnt Bresch , Martin Strcitenberger and Wolfgang Mathis, “About The Demodulation of PWM Signals with Application to Audio Amplifiers,“ IEEE International Circuits and Systems Conference, Vol 1, pp. 205 – 208, June 1998.

[4]Adel S. Sedra and Kenneth C. Smith, “Microelectronic Circuits” Fifth Edition, Oxford University Press, 2004.

[7]D.Dapkus, “Class-D Audio Power Amplifiers: An Overview,” Consumer Electronics, ICCE, pp.400-401, June 2000.

[12]M. T. Tan, H. C. Chua, B. H. Gwee and J. S. Chang,”An Investigation on the Parameter Affecting Total Harmonic Distortion in Class D Amplifier,” IEEE International Circuits and Systems Conference, vol.4, pp.193-196, May 2000.