音頻功率放大器的損耗主要來自輸出功率電晶體上的導通損耗。傳統功率放大器多採用固定工作電壓架構，當放大器在低功率輸出時，工作於線性區的電晶體跨壓相對增大，效率也隨之降低。本論文研究一組能跟隨輸入聲音訊號大小來調整功率放大器電源電壓的高功率音頻放大系統。藉由動態調整電源電壓的功能，在低功率輸出時，降低放大器工作電壓，藉此降低功率電晶體所造成的導通損失，達到提升整體功率放大系統效率的效果。本論文中將由前級取得聲音訊號作為電源轉換器之參考訊號，以輸入之聲音訊號大小控制電源轉換器之輸出電壓。所研究放大器系統可分為功率放大器與可變電源供應器兩組區塊：功率放大級所採用的是新型積體電路驅動模組搭配AB類輸出級；而電源轉換器部份架構為全橋相移轉換器。
本論文實作完成一組輸出功率800 W，並搭載可變電源供應器之音頻放大系統，實驗結果顯示調壓功能可使放大器之效率上升至60 %以上，減少電能消耗。

Conventional audio power amplifiers are operating with fixed power supply. It means that the power losses caused by quiescent current are also fixed and regardless to output power. When power amplifier working in low power condition, the voltage across power devices will be larger than high power condition such that the losses on power devices increase.
This dissertation presents an audio power amplifier with variable power supply controlled by input audio signal. In low-power output condition, the power supply will provide low voltage to reduce the power loss on power transistors and improve circuit efficiency. The power supply voltage of power amplifier can be controlled by the audio input signal used as the reference of power converter. The amplifier system is divided into two parts: the audio power amplifier adopting an integrated amplifier driving circuit with class AB topology and the power supply implemented with a full-bridge phase-shifted converter.

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