現今主動式有機發光二極體顯示器被廣泛應用於消費性電子產品中，具有高驅動能力的低溫多晶矽薄膜電晶體普遍被作為主動式有機發光二極體顯示器之背板使用，然而其臨界電壓變異及電壓源線上線阻所產生的壓降會導致有機發光二極體發光電流不均勻。隨著顯示器的解析度逐漸提高，當畫素電路以傳統的漸進式發光驅動法驅動時，每列的補償時間將會大幅度縮短以降低電路補償能力，進而劣化畫面品質。另一方面，低溫多晶氧化物薄膜電晶體同時具備低溫多晶矽薄膜電晶體之高電流驅動能力與氧化銦鎵鋅薄膜電晶體之低漏電特性，當智慧手錶顯示器以降低更新頻率之方式減少功率消耗時，所搭配之閘極驅動電路之設計需要考量漏電問題，使電路能在延長發光時間內維持高驅動能力，進而持續輸出穩定的面板控制訊號。此外，為了實現窄邊框智慧手錶顯示器，具備雙輸出之閘極驅動電路設計有助於縮減邊框面積，同時為了提高電路的相容性，提供雙向操作之電路也是一大議題。
本論文提出了一個應用於高解析度顯示器之畫素電路與兩個以低溫多晶氧化物薄膜電晶體為基板之雙向雙輸出閘極驅動電路。第一個電路是應用於高解析度顯示器的 4T2C 畫素電路，此電路使用同步式發光驅動法延長補償時間以提升臨界電壓變異補償準確度，為了確認其可行性，此電路在 4K (2160×3840) 顯示器解析度下經由模擬結果驗證，當驅動電晶體臨界電壓變異 ±0.5 V以及電源變異 0.5 V 時，相對電流誤差率分別小於 4.45% 與 3.06%，且電路操作過程無非預期閃爍現象，有利於提高畫面之對比度。第二個電路為具有雙輸出及雙向傳輸功能的低溫多晶氧化物薄膜電晶體閘極驅動電路，其能夠同時提供穩定且高驅動能力的正脈波與負脈波輸出波型，減少顯示器中所需的閘極驅動電路數量以縮減面板之邊框面積，模擬波型顯示此電路能夠成功地產生雙向且連續之輸出波型以增進其兼容性，此外此電路兩輸出波型的上升、下降時間分別皆小於 0.674 μs 及 0.840 μs，驗證此電路透過電容耦合架構抬升驅動電晶體閘極電壓以達到快速充放電的效果，另外在低溫多晶矽薄膜電晶體臨界電壓變異 ±0.5 V 及氧化銦鎵鋅薄膜電晶體臨界電壓飄移 5 V 的情況下，此電路仍能正確產生輸出波型。然而，此電路輸出的穩壓時間僅為半個幀週期，當受到面板雜訊影響時，可能導致輸出波型不穩定，因此本論文提出的第三個電路為具備高可靠度之低溫多晶氧化物薄膜電晶體閘極驅動電路。第三個電路除了能夠提供快速充放電之雙向雙輸出波型外，更可以在暫停時脈訊號進一步減少智慧手錶顯示器之功耗時仍然成功地產生輸出，模擬結果顯示在時脈訊號暫停 50 ms 後，驅動電晶體閘極電壓分別只下降 0.053 V 及 0.343 V，驗證了其能幾乎不受開關電晶體漏電流所影響以產生高穩定度之輸出波型，此外，即使在低溫多晶矽薄膜電晶體臨界電壓變異 ±0.5 V 與氧化銦鎵鋅薄膜電晶體臨界電壓飄移 5 V 時，輸出波型仍維持一致，驗證了所提出電路應用於低更新頻率智慧手錶顯示器之可行性。

Nowadays, active-matrix organic light-emitting diode (AMOLED) displays are extensively applied in consumer electronics. Low-temperature polycrystalline silicon thin-film transistors (LTPS TFTs) which have the high driving capability are commonly used as the backplane of AMOLED displays. However, the threshold voltage (VTH) variations of LTPS TFTs and the current-resistance drops (I-R drops) in power lines lead to nonuniform OLED driving currents. With the resolution of displays increasing, the compensation time of each row is greatly shortened under the conventional progressive emission method. Therefore, the compensation capability is degraded, worsening the image quality. In addition, low-temperature polycrystalline silicon and oxide (LTPO) TFTs are composed of LTPS TFTs with the high driving capability and amorphous indium-gallium-zinc-oxide (a-IGZO) TFTs with low leakage currents. When a lower frame rate is employed to reduce the power consumption in smartwatch displays, the driving capability of the gate driver circuit that may be affected by the leakage currents of TFTs must be maintained in the extended emission period to generate the stable control signals to the display panel. To implement the narrow-bezel smartwatch display, the gate driver circuit with dual output is beneficial to the reduction in the bezel area. Also, to enhance the compatibility of gate driver circuits, the bidirectional transmission is another important issue.
This thesis proposes one pixel circuit for high-resolution AMOLED displays and two bidirectional LTPO-TFT gate driver circuits with dual output. The first circuit is a 4T2C pixel circuit for use in high-resolution displays. This circuit adopts the simultaneous emission method to prolong the compensation time for enhancing the accuracy of the VTH compensation. To ensure the feasibility of this circuit, the simulation is conducted to meet the specification of a 4K (2160×3840) display. Simulation results reveal that the relative current error rates are respectively below 4.45% and 3.06% as the VTH of the driving TFT varies by ±0.5 V and VDD drops by 0.5 V. Also, no unexpected image flicker occurs in the programming period, increasing the contrast ratio of displays. The second circuit is a bidirectional LTPO-TFT gate driver circuit with dual output. Both the stable positive-pulse and negative-pulse output waveforms are generated with the high driving capability to decrease the number of gate driver circuits in a display system, shrinking the bezel area. Simulated waveforms show that the sequential output waveforms are transmitted bi-directionally to increase the circuit compatibility. In addition, the rise time and the fall time of the output waveforms are respectively less than 0.674 μs and 0.840 μs, proving that the fast charging and discharging are achieved by the capacitive coupling structure. Additionally, when the VTH varies by ±0.5 V in LTPS TFTs and the VTH shifts by 5 V in a-IGZO TFTs, the output waveforms are properly generated. However, the stabilization time only lasts for half of the frame period. When noise on the display panel interferes with this circuit, the output waveforms become unstable. Thus, the third proposed circuit is an LTPO-TFT gate driver circuit with high reliability. In addition to achieving fast charging and discharging and supporting the bidirectional operation, this circuit can successfully provide the stable output waveforms while the clock signals are paused to further reduce the power consumption. Simulation results show that the gate voltages of the driving TFTs only drop by 0.053 V and 0.343 V in the clock pause period, verifying that this circuit can generate the output waveforms without being affected by the leakage currents of the switching TFTs. Moreover, with the VTH variations of ±0.5 V in LTPS TFTs and the VTH shifts of 5 V in a-IGZO TFTs, the uniform output waveforms are still provided, confirming the feasibility of this circuit for use in low-frame-rate smartwatch displays.

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