Filterless Class-D Audio Amplifier with Multi-Level Converter

[[abstract]]本論文提出了兩種不同的音頻放大器架構，以得到較好的訊號雜訊比(SNR)及總諧波失真(THD)為研究目標，研究主題主要分成兩部分： 第一部分，我們利用台積電 0.18μm CMOS製程設計，設計一免時脈產生器之 D類音頻放大器，在電路架構方面，運用一簡單二階放大器作為比較器，產生脈波寬度調變(PWM)，使類比訊號轉換成數位訊號，以減少失真情形，再經由功率放大電路，增加電流量，使脈波寬度調變訊號增加功率，最後一部分是由電感、電容、喇叭組成的低通濾波器，使脈波寬度調變訊號還原成原始的類比訊號，用以驅動後級的喇叭負載。 第二部分，此電路也是利用台積電0.18μm CMOS製程設計，設計一無濾波器 D類音頻放大器設計，其基礎架構為多階信號，多階結構略分為五個架構：1.比較器2.移位暫存器3.組合全加器4.解碼器5.多階轉換器。在這個方法中，信號經過脈波寬度調變後分割成多個時間分段之後再整合成二進位形式，二進位形式被編碼成並列控制信號給多階轉換器，多階轉換器將會轉換多階信號到喇叭上，取代傳統二階信號，因此改善總諧波失真和訊號雜訊比，效果較好而不用犧牲功率消耗，所以我們可以提出一個方法應用到很多的 Class D音頻放大器，只要在調變器後插入移位暫存器和加法器，並搭配多階轉換器即可取代傳統的輸出架構。[[abstract]]In this thesis, we implement two different audio amplifiers architecture, research target is purpose to improve better SNR and THD. This thesis can be divided two part： The first part, we use 0.18μm CMOS technology provided by TSMC, design a clock free class-D audio amplifier. In circuit architecture, we use a simple two-stage operation amplifier as a comparator, generating pulse width modulation. Make analog signal convert to digital signal, and reduce distortion situation, and through the power amplification circuit to increase the current, purpose to increase power of pulse width modulation. The last part is a low pass filter composition of inductance, capacitance and speaker. It can revert pulse width modulation to original analog signal, and drive to latter stage speaker load. The second part, this circuit is also use 0.18μm CMOS technology provided by TSMC, design a filterless class-D audio amplifier with multi-level converter. The basic architecture is multi-level signal. Multi-level architecture can roughly divided to five parts：1. Comparator 2.Shift registers 3.Combined full adder 4.Decoder 5.Multi-level converter. In this method, pulse width modulation signal is arrange too many time divisions and integrate into a binary form. Binary form is decoded to control signal for multi-level converter. Multi-level converter will convert multi-level signal to speaker, replace traditional two-stage signal. So improve THD and SNR without sacrificing power efficiency. Since, this work can be used in any class-D audio amplifier, designing by insert shift registers and adder behind modulator and replace output stage with multi-level converter.[[note]]碩