具非線性控制迴路緩啟動技術之直流轉直流轉換器

Abstract

TFT-LCD面版和數位相機等等電子產品，在近幾年間受到廣大的消費者的歡迎。而電源管理系統的使用可以達到提供穩定的供應電壓源給予這些電子產品以及延長電池壽命的功用。 緩起動技術對於電源管理系統處在啟動狀況是很重要的，特別是對於直流轉直流穩壓器。緩啟動技術不但可以有效地降低初始的入侵電流以避免系統受到破壞，也具有確保轉換器啟動成功的功用。傳統的緩啟動技術是利用外掛大電容產生緩慢上升的控制訊號來完成啟動。然而，此大電容卻會增加系統的成本與面積。 本論文提出具非線性回路控制緩啟動技術產生從零到最大限制電流位準的步階電流限制訊號來完成轉換器的緩啟動。因為每一個特定的電流限制位準都會對應到相對的輸出電壓，因此我們可以藉此把輸出電壓升到所設計的位準。此技術在任何的負載條件下不但具有高度的限制固定電流能力，也利用著無電容緩啟動的設計來減少轉換器的輸入輸出接腳以達到降低系統成本的目標。 此提出的緩啟動技術是建構在電流模式控制的直流轉直流升壓轉換器。藉由電流模式的控制，使轉換器擁有很好的效能相對於電壓模式的控制。除此之外，所設計轉換器的實現是藉由聯電0.35-□m 製程技術。其效率表現可達90％在重負載的條件之下。

The electronic devices, such as TFT-LCD panel and digital camera, are great prevalent for customer market in the recent year. In order to provide the regulated supply voltage and extend the battery life, the power management system is utilized. The soft-start technique is an important feature for power management system especially for the power-on sequence of dc-dc converters. It not only diminishes the inrush current to protect the converter from occurring damage but also ensure the converter to start up successfully. The conventional soft-start technique uses a large off-chip capacitor to generate gently reference voltage. However, the large off-chip capacitor occupies an external I/O pin to increase the cost and footprint area of the power module. In this thesis, the proposed soft-start technique with nonlinear loop control provides the current-limit levels increased from zero up to the maximal current-limit value in design current steps. As a result, the specific output voltages can be raised up by characteristic current steps. The proposed technique not only has excellent constant peak current limiting capacity for any load conditions to diminish initial inrush current efficiently, but also reduces the numbers of the external I/O pins to decrease the cost of the converter without needing any external capacitors. The proposed soft-start technique is based on the current-mode controlled boost converter with better performances than those of voltage-mode controlled converter. The converter implementation is simulated and fabricated by UMC 0.35-□m CMOS technology and the efficiency is 90% in the heavy load condition.