應用於薄膜電晶體液晶顯示器之以脈衝頻率調變的單電感雙極性多輸出直流升壓電路

Abstract

本篇論文提出了一單電感雙極性多輸出直流轉直流升壓電路，應用於液晶顯示器驅動電路中。近年來液晶顯示器技術快速成長，以玻璃為基版之製程技術也趨近成熟與廣泛使用於各種顯示器應用中，此論文設計之電壓轉換電路是用於提供玻璃基板上的類比或數位電路直流偏壓點，而此類電路通常需要較高之雙極性偏壓點來進行驅動。 本論文設計之電壓轉換器僅需使用一外接電感，便可將2.8伏特之輸入電壓轉換成四個雙極性輸出電壓，包含了+12伏特、-12伏特、+6伏特和-6伏特。有別於傳統使用脈衝寬度調變(Pulse Width Modulation, PWM)的控制方法，本論文採用的控制方法為脈衝頻率調變(Pulse Frequency Modulation, PFM)中的固定導通時間(Constant On-time, COT)控制方法並採用動態充電演算法來根據輸出負載輕重自動調整操作頻率來達成，透過自適應操作頻率調變功能本電路可以在非對稱負載情況下仍然維持高轉換效率，並使用輸出電壓漣波感測方式來達成較簡單之數位回授控制網路，透過直接提取輸出電壓資訊的方式，本電路可以提供極快速之暫態響應。 本論文設計之單電感雙極性多輸出直流轉直流電壓轉換器透過台灣積體電路公司點二五微米製程來實現並驗證，所提出之電路在模擬中所能提供最高輸出功率為340微瓦，操作頻率從650千赫茲到零赫茲，最大轉換效率為83.1%。

A constant on-time (COT) single-inductor bipolar multiple-output (SIBMO) on-chip boost converter is proposed for LCD drivers in this thesis. The converter is designed for biasing some analog and digital circuits fabricated on glass substrates for benefits of higher carrier mobility and lower thresholds. These circuits on glass require bipolar high voltages for drive LCDs. The converter boosts the input of 2.8V to two positive outputs and two negative outputs, +12V, +6V, -12V and -6V, respectively. Different from the commonly-used pulse width modulation (PWM), the pulse frequency modulation (PFM) is adopted herein by a dynamic charging algorithm whose frequency is adapted to the varied output voltage level, thus enjoying the merit of less circuit complexity and a smaller chip area. The constant on-time (COT) which belongs to PFM control method is in this study further developed to a ripple-based one for achieving applicability even with unbalanced output loads with high efficiency. While total maximum output power is 340mw and the switching frequency varies from 650 kHz to zero, the maximum efficiency reaches 83.1% by simulation. The converter is fabricated by TSMC 0.25μm 1P3M high voltage CMOS technology for verification.