搭載動態偏壓導通時間產生器之新型電荷幫浦式固定導通時間控制降壓型轉換器設計與實現

Design and Implementation of A Novel Charge-Pump Constant On-Time Controlled Buck Converter with Dynamic-Biased On-Time Generator

徐士傑(Shih-Chieh Hsu)

指導教授 ： 陳景然

國立臺灣大學/電機資訊學院/電機工程學研究所/碩士(2020年)

https://doi.org/10.6342/NTU202000925

摘要

近年來，漣波調變固定導通時間控制因為具有快速負載暫態響應、高輕載效率及架構簡單的特性，被廣泛應用於電源管理晶片。在電腦、智慧型手機等許多消費性電子產品中，為了縮小體積並且達到低輸出漣波電壓的需求，具低等效串聯電阻的積層陶瓷電容經常被使用於轉換器的輸出電容。然而，使用積層陶瓷電容之漣波調變固定導通時間控制降壓型電源轉換器可能會面臨到次斜波震盪的問題。
為了解決上述的次斜波問題，本論文提出了電荷幫浦式固定導通時間控制。此控制架構同時保有傳統漣波調變固定導通時間控制之快速負載暫態響應及高輕載效率的優點。除此之外，本論文也提出了動態偏壓導通時間產生器之技術，設法減低控制器之靜態電流消耗。
上述所提出之控制架構晶片使用台積電0.18 μm CMOS製程實現，可應用在切換頻率高達8百萬赫茲的降壓型電源轉換器中。此外，本論文利用描述函數的數學分析對電荷幫浦式固定導通時間控制架構推導小信號模型，進而分析系統穩定度及暫態響應。最後，透過模擬及實測結果驗證所提出的控制理論。量測結果顯示當輸入電壓為3.3伏特時，此降壓型轉換器可以操作在0.25安培至1.25安培的負載電流並可提供0.6伏特至1.3伏特的輸出電壓。當輸出電壓為1.0伏特，負載由0.25安培上升至1.25安培的暫態回復時間為1.5微秒，量測到的輸出壓降為60毫伏特。

關鍵字

降壓型電源轉換器 ； 電源管理晶片 ； 漣波調變固定導通時間控制 ； 電荷幫浦式固定導通時間控制 ； 描述函數 ； 小信號模型

並列摘要

Recently, ripple-based constant on-time (RBCOT) control has been widely used in power management integrated circuit (PMIC) due to features of fast load transient response, high light-load efficiency and simple implementation. In many applications such as personal computers, smartphones, and other consumer electronics, multilayer ceramic capacitors with low equivalent series resistance (ESR) are preferred because of compact size and small output voltage ripple requirement. However, a buck converter with RBCOT control may encounter the subharmonic oscillation, especially while low ESR ceramic capacitors are used as converter’s output capacitors.
In this thesis, a charge-pump constant on-time (CPCOT) control scheme is proposed to overcome the subharmonic issue. This control method can also achieve fast transient response and maintain high efficiency under the light-load condition, which are the inherent advantages of RBCOT control scheme. In addition, a dynamic-biased technique for on-time generator is introduced to reduce quiescent current of the controller.
The proposed control was implemented into a monolithic IC using Taiwan Semiconductor Manufacturing Company (TSMC) 0.18 μm CMOS process for a buck converter with switching frequency up to 8 MHz. Furthermore, small-signal model of the CPCOT control was derived based on the describing function (DF) technique to predict system stability and transient response. Finally, simulation and measurement results are given to verify the proposed concepts. The measurement results show that the buck converter can operate under load current between 0.25 A and 1.25 A and produce output voltage from 0.6 V to 1.3 V while the input voltage is 3.3 V. The measured undershoot is 60 mV with 1.5 μs settling time when the load current is increased from 0.25 A to 1.25 A under 1.0 V output voltage.

並列關鍵字

buck converter ； power management integrated circuit (PMIC) ； ripple-based constant on-time (RBCOT) control ； charge-pump constant on-time (CPCOT) control ； describing function (DF) ； small signal model

參考文獻

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