Dual Gate AMOLED Pixel Driving Circuit Threshold Voltage Compensation
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Solution Overview
Problem
The AMOLED pixel driving circuit faces challenges due to threshold voltage drift in thin film transistors and organic light emitting diodes, leading to inconsistent current flow and brightness issues, which existing solutions fail to adequately address without complicating the data signal and increasing stress on the drive thin film transistor.
Innovation Solution
The proposed solution involves a 5T2C AMOLED pixel driving circuit with a dual gate thin film transistor as the drive transistor, utilizing a pre-charge stage, threshold voltage programming stage, and drive stage to stabilize the threshold voltage at Vth=Vpre−VOLED, ensuring the current flowing through the organic light emitting diode is independent of the threshold voltage, thereby simplifying the data signal and maintaining consistent brightness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the data signal is increased to compensate for threshold voltage drift in single gate thin film transistor, then the threshold voltage drift influence is weakened, but the voltage stress on the drive thin film transistor increases and accelerates threshold voltage drift
Solution Approach 1:
The patent changes the electrical parameters by introducing a preset voltage (different from traditional data signal voltage) to the bottom gate of the dual gate thin film transistor. This parameter change allows the threshold voltage to be adjusted without proportionally increasing the voltage stress on the transistor, as the top gate voltage can be independently controlled to compensate for drift while maintaining safer operating conditions.
Solution Approach 2:
The patent segments the gate control into two independent gates (bottom gate and top gate) of the thin film transistor. The bottom gate receives the preset voltage for threshold voltage compensation, while the top gate receives the data signal for current control. This segmentation allows independent optimization of threshold voltage stability and voltage stress management, resolving the contradiction between compensating for drift and avoiding accelerated degradation.
2Reliability
If traditional single gate thin film transistor is used with threshold voltage compensation, then the compensation function is achieved, but the data signal complexity increases and voltage stress accelerates drift
Solution Approach 1:
The patent segments the gate control into two independent gates, where the bottom gate handles threshold voltage compensation with a simple preset voltage signal, and the top gate handles data signaling. This segmentation simplifies the overall data signal requirements compared to single gate designs that must encode both compensation and data information, while achieving robust compensation functionality.
Solution Approach 2:
The bottom gate of the dual gate thin film transistor acts as an intermediary that receives a simple preset voltage signal to establish the threshold voltage compensation. This intermediary structure separates the compensation function from the data signal path, reducing data signal complexity while maintaining effective compensation capability.
3Reliability
If dual gate thin film transistor is used with preset voltage, then the threshold voltage drift is compensated and current becomes independent of threshold voltage, but the circuit structure becomes more complex
Solution Approach 1:
The patent segments the transistor into dual gate structure where the bottom gate handles threshold voltage compensation and the top gate handles data signaling. This segmentation enables the current through the organic light emitting diode to be independent of threshold voltage variations, achieving consistent current output while the additional gate structure provides the compensation mechanism.
Solution Approach 2:
The dual gate thin film transistor structure provides multiple functions: the bottom gate handles threshold voltage compensation, the top gate handles data signaling, and together they ensure current consistency independent of threshold voltage drift. This multi-functionality justifies the increased structural complexity by delivering superior current consistency and reliability.
Data Source
AI summary
The present invention provides an AMOLED pixel driving circuit and a pixel driving method. By utilizing the dual gate thin film transistor to be the drive thin film transistor, in the pre-charge stage, the preset voltage (Vpre) is written to the bottom gate (BG) of the first thin film transistor (T1), and the power source voltage (VDD) is written to the top gate; in the threshold voltage programming stage, the voltage of the top gate (TG) of the first thin film transistor (T1) drops, and the threshold voltage is raised until the threshold voltage is lifted up to Vth=Vpre−VOLED; in the drive stage, the voltage of the top gate (TG) is kept unchanged to keep the threshold voltage remaining to be Vth=Vpre−VOLED, and the data signal Data drives the first thin film transistor (T1) to be activated to make the organic light emitting diode (D1) emit light.