| dc.description.abstract | 本論文旨在探討一完整D類音頻擴大器的系統設計與電路實現。由於D類音頻擴大器是非線性系統，傳統設計方式是利用線性模型進行分析與設計，這種間接的設計方法無法對系統的穩定性直接進行分析。本文回顧數種文獻上具代表性的D類擴大器，並決定採用低成本、簡單、精確的Δ-Σ調變器(Delta-Sigma Modulators, DSMs)作為D類音頻擴大器的類比/數位 (Analog to Digital, A/D)轉換器。文中，應用順滑模態控制理論設計連續時間積分器的DSMs，有效解決傳統設計DSMs時，無法直接對系統進行穩定性分析的問題，並改善一般DSMs調變率只有50%、輸出資料速率(output data rates)高達1MHz的缺點。本文提出二階與三階DSMs的完整設計過程。本論文所設計的DSMs調變率可達75%以上、資料輸出速率約為100kHz〜250kHz。
此外，系統的數位/類比(Digital to Analog, D/A)轉換部分，包括DSMs輸出位準轉換、MOSFET的閘級驅動電路、功率開關輸出級與濾除高頻開關雜訊的低通濾波器，本文均依據實際需求分析、實作完成。
本研究提出一完整之D類音頻擴大器設計方法，所得D類音頻擴大器具有快速反應、穩固的強健性、易於實現，可直接由市售現成零件製作完成等特性。實驗結果証實本文所提的設計方法確實可行，在3.5歐姆負載上的方均根輸出功率為100瓦時，效率達80%、總諧波雜音失真(Total Harmonic Distortion plus Noise, THD+N)低於0.73%、訊噪比（Signal to Noise Ratio, SNR）為75dB。本製作可應用於一般音響需求，更適合用於需要高效率，大功率輸出的大眾廣播系統，如防空警報系統、災害預警系統、戶外活動擴音系統等。
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| dc.description.abstract | The purpose of this paper is to explore the design and implementation of class-D audio amplifier. It is known that class-D amplifier is a nonlinear system. Somehow, in conventional method, class-D amplifier is usually designed through linear model. This indirect method in class-D amplifier design could not analyze the stability of the system directly. In this study, several significant class-D amplifiers in the literatures have been reviewed, and DSMs (Delta-Sigma Modulators) was chosen to be the A/D (Analog to Digital) converter for the class-D audio amplifier due to the low cost, simple circuit and accuracy in A/D converting. The sliding mode control design methodology is developed for designing the continuous time integrator DSMs. It effectively solves the problem for not analyzing the system on the stability in conventional way of designing DSMs. Meanwhile it also improves the drawbacks of DSMs which could only reach up to 50% modulation in stable operation and output data rates are more than 1MHz. In this paper, the design of second and third order DSMs are presented. The proposed DSMs enables the modulation rate up to 75% in stable operation and output data rate are decreased to 100kHz〜250kHz.
Furthermore, some parts of the D/A(Digital to Analog) in the system, which includes the shift of DSMs output levels, power MOSFET gate driver, switching output stage, and lossless low-pass filter for filtering high frequency switching noise, are analyzed and implemented as the practical needs.
A completed design method of class-D audio amplifier is presented in this study. The proposed amplifier exhibits the features in fast response, strong robustness, easy to implement, and can be produced directly by the commercial electronic elements. Experimental result confirms that the proposed design approach is surely feasible. In the 3.5 ohm load with the RMS output power of 100 watts, the measured maximum power efficiency is 80%, and THD+N that is less than 0.73%, and SNR of 75dB.The proposed class-D audio amplifier can be applied to general audio needs, and is more suitable for the application of the public broadcasting systems that require high efficiency, high power output, such as the air defense alarm system, disaster warning system, outdoor public address system, etc.
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