應用於面板之多工器與高可靠性之閘極驅動電路研究

行動裝置隨者科技日新月異而日漸普及，人們對於手機與平板等液晶顯示器(Liquid Crystal Display, LCD)的需求也日漸增加。在行動裝置上的顯示技術追求更高解析度以及顯示區的擴大也成為當今面板技術的核心。而伴隨者需求量的提升，如何在大量生產的同時降低成本才能使商品擁有更大的競爭力。液晶顯示器技術應用閘極驅動電路(Gate Driver)製程整合在面板顯示器周邊「閘極驅動電路陣列技術」為當今發展的趨勢。閘極驅動電路的基本原理為輸出序列式的訊號打開面板顯示區的電晶體，進一步使資料驅動電路(Data Driver)輸出對應電壓資料到液晶以及儲存電容中，產生序列式的連續畫面。在傳統的面板顯示器中，閘極端的訊號輸入會由閘極驅動IC晶片(由矽晶圓製程所製造)提供，為了將其與面板做連結，必須先封裝晶片再使用金屬線與顯示機板貼合，而在使用這些金屬線的同時會增加繞線的困難程度，金屬貼合時造成的誤差也會導致面板良率的下降。為了解決此等問題GOA(Gate On Array)技術因應而出。GOA技術的核心概念為將傳統面板側邊的閘極驅動電路取代，轉而製作到面板的玻璃基板上，使用GOA技術可以有效減縮面板兩側寬度使顯示區面積增加，並且降低IC的使用數量大幅減少製作成本，更可以減少由金屬繞線所產生的製程誤差。本論文除了提出閘極驅動陣列技術，更利用Source-Multiplexer源極端之多工器使面板製造成本降低。源極端解多工器核心概念與GOA技術相似，旨在減少源極端IC使用數量以及減少金屬繞線。為了使閘極與源極的電路皆能製作在玻璃基板上，元件上採用薄膜電晶體TFT(Thin-Film Transistor)，並選擇了非晶矽(a-Si)製成，使用此元件有成本便宜、製程簡單、高均勻性等優點。然而非晶矽薄膜電晶體(a-Si TFTs)擁有較低的電子遷移率以及較大的寄生電容(Parasitic Capacitance)，使得利用此元件設計電路時需考慮充電不足的問題，因此在設計解多工器時需要對輸入訊號以及架構上做調整並透過跑模擬以及量測分析評斷是否電路能正常的運作。本篇論文針對面板閘極端(Gate)以及源極端(Source)採用閘極驅動陣列技術以及解多工器應用針對不同解析度的面板做出設計，論文中分別對兩部分做出詳細的解說。對於解多工器而言，為了解決元件充電不足以及寄生電容所導致的電壓耦合效應(Feedthrough effect or Couple effect)，分別針對傳統的架構做調整利用補償技術並且引入輸入時序重疊(Timing Overlap)，達成預充電(Pre-Charge)的效果，此外為了保持液晶跨壓的不變我們採取Vcom調整的技術，而為了使電路壽命能夠延長導入了負偏壓(Negative Bias Voltage)以及並聯分時運作架構，使電路能夠分工合作並在休息時回復門檻電壓(Threshold Voltage Recovery)。對於閘極驅動陣列技術所設計的電路，本篇採用了全新的抗雜訊概念，有別於傳統GOA為了全時段抗雜訊(Full Time Noise-Free)而使抗雜訊節點(Q點)長期維持在工作狀態，此處採用了週期性的抗雜訊架構(Clock Controlled Noise-Free Structure)，使控制抗雜訊的開關元件(Noise-Free Block)擁有週期性(AC-Operation)。此外論文中還針對輸出元件以及抗雜訊區塊引入雙低準位(Multiple Level of VSS)，對開關元件做負偏壓回復門檻電壓偏移，透過兩者設計延長電路壽命。

關鍵字

LCD面板；多工器；閘極驅動電路

並列摘要

As technology process the popularity of mobile device has grown rapidly, liquid crystal panel such as mobile phone and Pad has been daily life needs. Developing high resolution and increasing the display area has become mainstream. In order to meet the huge needs of marketing, mass production and cost down are two factors to make company be more competitive. Nowadays, System-on-panel which integrated Gate Driver circuit in the surrounding of panel has been trend of display technology. The main function of Gate Driver is to generate sequential output signal to open the transistor in the display area of the panel. In order to make the panel having sequential picture on the display, letting Data Driver transfer correspond data voltage into the liquid crystal and storing capacitor of the pixel is necessary. In general liquid crystal display, the output of Gate Driver is produce by the Integrated Circuit which is made by Silicon. In order to connect the ICs with panel, there are several process to be done. First we need to package ICs and connect to panel with metal wire. However, there may have connection error while processing. At this moment, GOA (Gate On Array) born as a solution which not only can be manufactured on glass substrate making displays’ bezel thinner, but also can replace ICs. These two reasons make production have less cost and less error. In this thesis, we not only proposed GOA technology, but also proposed Multiplexer applying into Source Driver to reduce panels’ fabrication cost. The key concept of using Multiplexer has similar background with GOA, both of them are reducing ICs amount and signals. In order to let both circuit implant into glass substrate, we choose a-Si TFT (Amorphous –Silicon Thin Film Transistor) to design our circuits. A-Si TFT has several advantage compares to others. For example, it has low cost, most simple fabrication, and high uniformity. But still, it has disadvantages such as low electron mobility and large parasitic capacitance which caused low charging performance. During circuit design we should consider these challenges to make sure our circuit can function properly. In this thesis we use GOA technology and MUX structure, either of which focus on different resolution of panel display. We divide these designs into two topics. First, for the Multiplexer, in order to make sure we can make it charging to the request voltage level, we used the concept of Input Timing Overlap to pre-charge the component before its input, this idea can solve the issues of slow charging. As for feedthrough effect caused by large capacitance, we adjust conventional multiplexer structure and VCOM Modulation technology to maintain the voltage difference across the liquid crystal. In addition, to extend the circuit life time, we change the single component into parallel sharing half of the working time. Moreover, we introduce the idea of negative bias voltage to recover threshold-voltage shift. As for GOA, we adapt an innovative concept, using Clock Controlled Noise-Free Structure in replacement of traditional noise-free structure. While remaining the function of Full Time Noise-Free, we make the Noise-Free Node “AC-Operates”. Also we used multiple level of VSS to make several component has threshold voltage recovery. Through these two designs we expect the circuit life time could be extended.

並列關鍵字

LCD panel ； Multiplexer ； Gate Driver

參考文獻

[1] Acharya, V. H., Manchester, D. L., &Hunt, G. S. (1984). "Data transmission multiplexer control panel," US Patent Application No. 06/301,016, 1984.