大尺寸之脈衝重疊偵測主動觸控面板的實作研究

Abstract

在本篇論文當中，我們運用之前所提出的新型主動式觸控電路，其架構為兩個TFT （一個為開關用，一個為電阻用)以及一個電容，並藉由兩個閘極脈波輸入此觸控電路。 當手指觸碰面板之感應區塊時，造成觸控電路之RC 延遲時間增加，使開關TFT 得以短 暫地開啟。此開關TFT 於開啟期間會有電流訊號通過，藉著外部之偵測電路，來加以判 別手指是否已觸碰到面板之感應區塊。 此外，以該主動式觸控電路為基礎，分別加以探討實際應用之時，小尺寸面板以及 大尺寸面板之負載效應，對於近端感應區塊以及遠端感應區塊之偵測影響程度為何。依 據該主動式觸控電路之設計理念，面板當中感應區塊之RC 延遲時間必須小於面板之掃 描線RC 延遲時間，也必須小於手指觸碰面板之感應區塊的RC 延遲時間，面板未觸碰、 面板延遲、及面板觸碰三者之時間關係為遞增。因此，當面板尺寸越大時，掃描線之負 載也隨著增加，進而導致近端輸入之閘極脈波，到達遠端感應區塊時，已是失真之波形。 在手指未觸碰面板之情況下，此失真波形也使得遠端感應區塊之RC 延遲時間隨之增加， 亦造成開關TFT 進行了不必要之開啟動作，而讓外部之偵測電路誤判。 最後，進一步探討，若是將所有閘極脈波之高頻成份予以濾除，而得到失真波形。 利用此失真波形輸入至觸控面板之中，理論上遠端之感應區塊的RC 延遲時間，即不會 受到掃描線之負載影響，不僅可避免遠端誤動作之情事，甚至可更精簡面板設計之準則。

In this thesis, we use the previous theory that the new active touch circuit is proposed. Its structure is composed of two TFTs (one is switch, another is resistor), one capacitor and then the two scan pulses transmit to this touch circuit. When the touch pad is touched by finger, there will be a rise in the RC delay time of touch circuit. The TFT will be opened in a transient time and pass through current. We can check whether the touch pad is touched by detection circuit during the period. Besides, we have based on the new active touch circuit and discussed the influence between the loading effects of touch panel and the touch pad at near-end and far-end. According to the concept of design, we defined that the RC delay time is t1untouched when the touch pad is untouched, the RC delay time is t3touched when the touch pad is touched, and the RC delay time is t2loading for scan loading. Their relationships are shown as t1untouched < t2loading < t3touched. Therefore, when the touch panel size is increased, the scan loading is also increased. The scan loading will cause the scan pulse is a distorted waveform at far-end. When the touch pad is untouched, the RC delay time of far-end (t1untouched) is increased by the distorted scan pulse. It isn't necessary to open the TFT and will cause the mal-operation for the external detection circuit. Finally, to be more precisely, if we filter out the high frequency harmonics of all scan pulse and then feed the distorted scan pulses in touch panel. Theoretically, the scan loadings can't influence the RC delay time of touch pad at far-end. It did not only avoid the mal-operation at far-end but also make the design rule of touch panel very simple.