具緩啟動及快速暫態反應時間控制電容放大單晶片補償技術的直流-直流降壓電源轉換器應用

Abstract

本文提出的電流模式DC-DC降壓轉換器，它實現兩個電容放大補償技術。由於外部被動元件的減少‚因此達成了小尺寸和低成本的優點。此外，本文還提出了緩啟動電路，並建立控制電路以確保補償電路和緩啟動電路之間的正確操作程序。所述的控制電路改變脈衝寬度調變（PWM）使其運作在正常模式或緩啟動模式。當選擇緩啟動模式時，PWM的比較器的輸入信號可以由設計者設定。因此，設計者可以故意避免誤差放大器的過大輸出電壓。另外，如果控制電路可在適當的時間點切換到正常模式，功率轉換器的輸出電壓的過衝現象可以顯著減緩甚至消失。因此 ，監視電路被用來觀察功率變換器的輸出電壓‚當輸出電壓接近理想穩態電壓時，則是控制電路切換PWM為正常模式的最佳時機。另一項改良是補償電路的應用‚它運用了兩種電容放大器的技術，包括時間模式米勒（TMM）的補償器和電流模式米勒（CMM）的補償器，以串接方式組合成一個放大倍率相乘的電容補償效果。TMM是電容放大的第一級‚他使用開關元件將功率變換器控制在一個不連續的方式對電容充電。 CMM則是第二級放大‚它是以連續性的方式對電容充電，因此，CMM的反應速度快。由於CMM處理速度快，它適合被設計為一個自適應補償電路‚可根據電力變換器的輸出電壓的狀態作出最佳調整的電容補償。

This thesis presents two on-chip compensation techniques which implement on current mode DC-DC buck converter. Besides, it achieves the reduction of external passive components for compact size and low cost. Moreover, the thesis also proposed the soft start circuit and built a controller to ensure the correct operation among the on-chip compensation and the start-up procedure. The controller is based the pulse width modulation (PWM) control to select the normal mode or soft start mode. When selecting the soft start mode, the input signal of comparator of PWM can be set by designer. Thus, designer can deliberately avoid an excessive output voltage of the error amplifier. In addition, if PWM can be switched to the normal mode at the suitable time, the overshoot phenomenon of power converter output voltage can significantly slow down or even disappear. Therefore, a monitoring circuit is used to observe the power converter output voltage. When the output voltage is close to the ideal steady-state voltage, it is the optimum timing for switching. Another improvement is the application of the compensation circuit. Two useful capacitor multiplier techniques, including time-based mode Miller (TMM) compensator and current-mode Miller (CMM) compensator, are combined into one compensator. The TMM is the first stage of in the capacitor amplification. The use of switches controls suitable time for charging the capacitor in a discontinuous way. The CMM is the second stage. It charges the capacitor in a continuous way. Thus, the immediate processing speed is faster. Due to its fast response, it is suitable to be designed into an adaptive compensation circuit. The CMM compensator can make the best adjustment for the capacitor compensation according to the condition of the power converter output voltage.