近年來消費者對於顯示器的要求逐漸提升，由於次毫米發光二極體具有高亮度及長壽命等優點，使其被廣泛研究並應用於主動式矩陣液晶顯示器之直下式背光模組，藉由分區調光方式達到高動態範圍成像，提升螢幕對比度並使畫面更加細緻。然而次毫米發光二極體背光需高發光電流驅動以提升螢幕之對比度，驅動電路所需跨壓也得保持在較大範圍，因此背光模組之功率消耗依然是一大問題。此外次毫米發光二極體主動式矩陣背光會受到電晶體臨界電壓變異以及電壓源電流電阻效應影響導致發光電流的不均勻性進而影響驅動電流使畫面品質失真。
針對上述問題，本論文提出三個以低溫多晶矽薄膜電晶體設計並具備降低功率消耗架構之次毫米發光二極體背光驅動電路，且採用主動式矩陣架構使每顆次毫米發光二極體皆為獨立驅動，最後再透過模擬軟體驗證所提出電路之可行性。首先，本論文提出了具匹配驅動電晶體補償架構的背光驅動電路，透過減少發光路徑上之開關電晶體，藉此降低電路所需跨壓以達到節省功率消耗的效果，根據模擬結果驗證此電路能有效補償電晶體臨界電壓與電源地端變異，並具備降低功率消耗之效果。然而此電路採用類比式驅動法，因而使面板顯示中低灰階時之次毫米發光二極體發光效率降低，造成背光模組相較於數位式驅動法產生較多功率消耗。為改善上述問題，本論文則提出採用脈衝寬度調變法的背光驅動電路，其透過適當調節脈衝寬度調變的占空比，改變次毫米發光二極體的發光時間長短來區分背光源之灰階，達成數位式驅動，使背光矩陣中每顆次毫米發光二極體皆操作在最佳發光效率點，進一步降低面板整體之功率消耗，模擬結果顯示此電路在電晶體臨界電壓及電源地端皆有變異之下仍可輸出穩定發光電流，而在脈衝寬度調變法下的灰階控制也不受開關電晶體臨界電壓變異所影響，然而此電路所使用的三角波形訊號線仍未進入量產，以現行晶片產生之波形尚有缺陷。為了提升所設計的驅動電路導入於產品之可行性，本論文進一步提出一不需三角波形訊號線也可達到脈衝寬度調變控制的背光驅動電路，此電路特色是使用不同電流大小來控制發光的時間長短完成數位式驅動，其在實作上以現有生產技術便可達成，另外由模擬結果顯示在電晶體臨界電壓變異±0.3 V與電源地端抬升+0.5 V時，此電路仍可準確輸出發光電流，並能達到節省功率消耗及精準控制灰階之成效。由上述可知，提出之三個新式次毫米發光二極體背光驅動電路皆能減少功率消耗，並可輸出穩定之發光電流，經由模擬驗證其適用於次毫米發光二極體背光顯示應用。

In recent years, the demands of consumers on the image quality of displays have led to mini light-emitting diodes (mini-LEDs) being widely researched and applied to the direct-lit backlight module of active matrix liquid-crystal displays (AMLCDs) due to their positive features such as high brightness and long lifetime. With using backlight module to utilize multi-zone local dimming and accomplish high dynamic range (HDR), the contrast ratio and the image quality of display will be elevated. However, the high power consumption issue troubling mini-LED backlights still exists due to the need for the driving circuits to have high emission currents which increase image contrast ratio. Furthermore, the threshold voltage (V¬TH) of thin-film transistor (TFT) variation and the power line current-resistance drop/rise (I-R drop/rise) induce unstable mini-LED driving currents in AM mini-LED backlight circuits.
This thesis proposes three mini-LED backlight driving circuits using a low-temperature polycrystalline-silicon (LTPS) backplane with a power consumption reduction scheme. These circuits adopt the AM method to individually drive mini-LEDs, and the feasibility of them is verified by HSPICE simulation software. First, a proposed mini-LED backlight driving circuit with a matched-TFT compensation scheme can decrease the VDD-VSS voltage by removing switching TFTs along the emission path to achieve lower power consumption. Simulation results indicate that the circuit effectively compensates for variations in VTH and VSS I-R rise, while also reducing power consumption. However, circuits adopting the analog driving method, which decreases the luminous efficacy of mini-LEDs over lower gray levels, bring about high power consumption compared to the digital driving method. To solve the above-mentioned problem, a new mini-LED backlight driving circuit which adopts a pulse-width modulation (PWM) driving scheme is proposed. By changing the emission time of its mini-LEDs, the proposed circuit can differentiate gray levels, ensuring that each mini-LED operates at the best-luminous-efficacy point to reduce power consumption. Simulation results show that this proposed circuit outputs stable currents and precisely controls gray levels without the influence of VTH variation and VSS I-R rise. Nevertheless, the Vsweep signal used in this circuit has not yet reached the mass-production stage, as nowadays defects still exist in Vsweep signals outputted by off-the-shelf ICs. Next, a mini-LED backlight driving circuit with a PWM scheme which can decide upon different gray levels by utilizing distinct currents is proposed. Without the need for the Vsweep signal, the feasibility of producing this proposed mini-LED backlight circuit has been improving with the present production technology. According to simulation results, the proposed circuit can generate uniform currents while the VTH of driving TFT varies by ±0.3 V and VSS rises by 0.5 V, which can precisely control gray levels and reduce power consumption. In conclusion, this thesis proposes three mini-LED backlight driving circuits which can reduce power consumption and output stable emission currents. Simulation results show that the proposed circuit is suitable for use in mini-LED backlight applications.

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