應用於音頻放大器之追蹤參考電壓功能的單電感正負壓雙極輸出轉換器

Abstract

功率放大器一直被廣泛應用在各種電子產品中，其中音頻放大器在電路中實現對音頻信號的驅動功能。傳統的音頻放大器其電源電壓採用5V，0V作為地準位，輸出的共模準位在2.5V，因此需要經由一個很大輸出的電容（~22uf）才能過濾雜訊驅動音響。大電容帶來面積的增大。 本論文提出的單電感正負壓雙極輸出轉換器可以有效的解決這個問題，因為採用多路複用技術同時產生正負電壓供給音頻放大器，使得音頻放大器的輸出共模準位為0，這樣就可以去掉大電容即節省耗材也節省了面積。並且此電源管理系統具有追蹤參考電壓的功能，可有效的提升音頻放大器的效率。此論文之轉換器架構通過模擬將電源電池電壓轉換成一組大小相等的正負電壓，并可以隨著參考電壓波形變動。 此外，此論文之轉換器因減少不必要的電流損耗可以達到最高88.9%的傳輸效率。 關鍵字 : 音頻放大器、共模準位、單電感正負壓雙極輸出、追蹤參考電壓功能

Power amplifier has been widely used in a variety of electronic products, including audio amplifier in the circuit to achieve the audio signal driver. The traditional audio amplifier has a supply voltage of 5V and 0V as ground, and the output common mode level is at 2.5V, so it needs a large output capacitor (~22uf) to filter noise. Large capacitor makes the area increase. This paper presents a single inductor bipolar output(SIBO) converter can effectively solve this problem, because the use of multiplexing technology to produce positive and negative voltage supply audio amplifier, making the audio amplifier output common mode at 0V, so it can remove the large capacitor saving area and decrease power consumption. This power management system has a reference voltage tracking function, can effectively enhance the efficiency of the audio amplifier. The converter architecture of this paper simulates the conversion of the power supply battery voltage into a set of equal positive and negative voltages and can change with reference voltage waveform. In addition, the converter of this paper achieves a maximum efficiency of 88.9% due to reduced unnecessary current losses. Keywords: audio amplifier, common mode level, single inductor bipolar-output, reference voltage tracking