具適應性快速充放電技巧之電流模式直流-直流降壓轉換器

Abstract

在現今消費性電子產品中，尤以手持式產品的應用上，需求越來越廣泛。擁有高效能的電源轉換器日趨重要，而隨著製程的演進，信號擺幅及供應電壓持續降低。因此，今日的電源轉換器必需在負載變動時能做出快速的反應並且維持穩定的輸出電壓。 在傳統切換式轉換器中，由於電感的限制，電流無法立即改變。本論文提出新的架構，具適應性快速充放電技巧之脈衝寬度調變電流模式直流降壓轉換器，主要藉由增加額外提供之路徑，一條直接補償於輸出端，另外兩條補償於控制迴路。當負載發生變化時，此技巧會打開輸出端之補償路徑，來抽取或灌入電流，並補償至原本的控制迴路，藉此加速暫態反應。 這個架構被實現於TSMC 0.25μm CMOS製程。根據量測結果，本晶片暫態響應的回復時間約為6~7 μs。相較於傳統架構而言，回復時間減少了約40~50%。另外在轉換效率方面，由於快速充放電迴路僅在暫態時運作，本晶片在輸出電流100~500 mA時，轉換效率仍能介於78~85%之間。其他細節與量測結果包含在本論文內。

The switching regulators have been widely used in power supply systems and are becoming a common building block in modern VLSI systems, especially for the growing number of battery-operated portable devices. With the evolution of the process, the supply voltage and the signal level decrease. Therefore, fast load transient response to keep output voltage stable and clean becomes very critical for voltage regulators nowadays. The output current slew rate of the switching converter is restricted by the inductor in conventional architecture. In this thesis, we propose adaptive fast charging control technique for current mode dc-dc buck converters to improve this issue. In this architecture, we add adaptive fast charging control technique, which has some new paths connected to the output capacitance and the control loop. When the output load current becomes large or small instantly, the additional current path will source or sink current to the output and compensate the control loop to achieve fast transient response. This technique is implemented with TSMC 0.25μm CMOS process. Measurement results show that the recovery time is within 6~7μs. Compared with the conventional design, which typically gives 12μs, the recovery time is reduced by about 40-50%. In addition, since the adaptive fast charging control only works in transient response, the power conversion efficiency is still in a range of 78%~85% with load current between 100 mA and 500 mA in the proposed architecture.