搭載動態導通時間產生器之新穎電容電流定導通時間控制降壓型轉換器

A Novel Capacitor Current Constant On-Time Controlled Buck Converter with a Dynamic On-Time Generator

潘聖翔(Sheng-Hsiang Pan)

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(2018年)

https://doi.org/10.6342/NTU201804396

摘要

電壓平方定導通時間控制降壓型轉換器廣泛用於微處理器和數位負載之供電，但它對於使用陶瓷電容作為其輸出電容存在不穩定性。為了解決此不穩定性，各種定導通時間控制在文獻中相繼被提出，然而，這些架構也都有其自身的問題，並在穩定性和暫態響應之間產生權衡。

為了解決這些問題，本論文提出了電容電流定導通時間控制架構之降壓型轉換器。此架構不僅沒有因使用陶瓷電容作為輸出電容所產生的不穩定性且也解離了穩定性及暫態響應之間的關係。在建立的小訊號模型中，從理論上證實了上述說法，並透過模擬作驗證。所提出的控制架構沒有因使用輸出陶瓷電容之不穩定性;而且，可以在不進行權衡的情況下實現穩定性和快速暫態響應。本論文也提出了一種動態導通時間產生器，進一步改善暫態響應並在高開關切換頻率下實現準確的導通時間。

所提出的控制架構採用0.18微米互補式金屬氧化物半導體製程來實現，開關切換頻率為四百萬赫茲，量測波型顯示了輸出電壓為1伏特及近似最佳負載暫態響應，其中電流負載抽載及卸載分別為800奈秒回穩時間及零響應。整個晶片包括墊片環之尺寸為1140.87*993.08微米平方。

關鍵字

電壓平方定導通時間控制 ； 電壓調節器 ； 電容電流定導通時間控制 ； 動態導通時間產生器 ； 近似最佳負載暫態響應

並列摘要

V2 constant on-time (V2COT) controlled buck converter is widely used to power microprocessors and digital loads, but there is an instability issue when ceramic capacitors are used as the converter’s output capacitors. Various COT control schemes have been reported in the literature to address the instability issue. However, these reported schemes have problems of needing trade-off between stability and transient response.

To these issues, a capacitor current constant on-time (C2COT) scheme is proposed in this thesis for buck converters. This scheme not only does not have the instability issue when using ceramic output capacitors but also allowing the decoupling of the stability and the transient response of the converters. A small-signal model was developed to theoretical prove the above statements, and are proved in simulation. The proposed scheme has no instability issue with the ceramic output capacitor; also, stability and fast transient response can be achieved without trade-off. A dynamic on-time generator is also proposed to further improve transient response and achieve accurate on-time at the high switching frequency.

The proposed control scheme was implemented in a monolithic IC using 0.18μm CMOS process with 4-MHz switching frequency. The experiment shows that output voltage equaling to 1-Volt and near-optimal load transient responses with 800ns settling time and null-response for both load current step-up and step-down, respectively. Total chip size is only 1140.87 μm by 993.08 μm with pad ring.

並列關鍵字

V2 constant on-time control ； voltage regulators (VRs) ； capacitor current constant on-time (C2COT) control ； dynamic on-time generator ； near-optimal load transient response

參考文獻

[1] Jian Li, “Current-mode control: modeling and its digital application,” Ph.D Dissertation of Virginia Polytechnic Institute and State University, Commonwealth of Virginia, Apr. 2009.

[2] D. Goder and W. R. Pelletier, “V2 architecture provides ultra-fast transient response in switch mode power supplies”, in Proc. HFPC, 1996, pp.19-23.

[3] K. Y. Cheng, F. Yu, P. Mattavelli, and F. C. Lee, “Characterization and performance comparison of digital V2 -type constant on-time control for buck converters,” in Proc. IEEE 12th Workshop on Control and Modeling for Power Electronics, 2010, pp. 1–6.

[4] R. Redl and J. Sun, "Ripple-based control of switching regulators—an overview," IEEE Trans. Power Electron., vol. 24, no. 12, pp. 2669-2680, Dec. 2009.

[5] Jian Li; Lee, F.C., "Modeling of V2 current-mode control," IEEE Trans. Circuits and Systems I: Regular Papers, vol.57, no.9, pp. 2552-2563, Sept. 2010