在現今的直流-直流電壓轉換器中，脈衝寬度調變技術仍是現在最常見的控制機制，它具有穩定度高及頻率固定等特點，這讓我們能夠很容易的決定晶片外濾波器之電感電容的規格，另外，由於切換頻率能夠準確的控制，因此切換雜訊並不會大幅的降低混合訊號系統的訊噪比。
但是脈衝寬度調變技術之直流-直流電壓轉換器的最大缺點在於較慢的暫態反應以及較大的晶片外補償電容，這些都限制了它在可攜式產品以及要求快速暫態反應之晶片上的應用，因此考量到快速的暫態反應以及不需要晶片外補償電容等需求，變頻率的控制方式則顯得相當吸引人。
由於變頻率控制直流-直流電壓轉換器之切換週期可以在暫態時瞬間改變，因此變頻率之控制方式具有快速暫態響應之優點。然而變頻率的控制方式通常會遇到穩態切換頻率隨輸入輸出電壓改變而變動的問題，這會使得設計輸入輸出濾波器變的複雜。因此，本論文提出ㄧ適應性開啟時間電流模式控制電路。此控制電路能夠在穩態操作時動態的隨著輸入輸出電壓改變調整功率晶體的開啟時間，並且能夠在暫態響應時瞬間改變切換週期。藉由所提出的控制電路，直流-直流轉換器可以同時做到快速暫態響應並且能夠有效抑制穩態頻率的變動。最後並提供完整晶片之模擬及量測結果以驗證所提出之架構，並且與其它架構做比較。

For controlling dc-dc converters, variable switching frequency controllers have the advantage of fast transient response since the switching cycles can instantaneously change during the transient condition. However, these control techniques generally suffer significant steady-state switching frequency variation when the input voltage and output voltage are varied. Such drawback complicates the design of input and output filters. Therefore, this thesis presents a current mode adaptive on-time control scheme. The proposed controller can dynamically adjust the turn-on time of power switches according to the changes of input voltage and output voltage in steady-state operation and can change switching cycles instantaneously in transient operation. Through the proposed control scheme, the dc-dc converters can accomplish fast transient response with the capability of mitigating the switching frequency variation. Full chip simulation and measurement results are provided to verify the proposed method. Comparisons with other control techniques are also presented.

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