Amoled Pixel Driver Circuit Threshold Voltage Drift Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing AMOLED pixel driver circuits face issues with threshold voltage drift in driving TFTs, leading to unstable current flow and non-uniform light emission due to the inability to effectively compensate for threshold voltage changes without adjusting the data signal, creating a vicious cycle of voltage stress and drift.
Innovation Solution
The proposed solution involves an AMOLED pixel driver circuit with a 6T1C structure, utilizing double-gate TFTs as the driving TFT, where the threshold voltage is compensated by pre-charging and threshold voltage programming phases, allowing the OLED to emit light independently of the threshold voltage, thereby stabilizing current flow and ensuring uniform luminance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the data signal is increased to compensate for positive threshold voltage drift in single-gate TFT, then the light-emitting uniformity is improved, but the voltage stress on the driving TFT increases which accelerates threshold voltage drift
Solution Approach 1:
The patent inverts the conventional compensation approach by not increasing the data signal to compensate for threshold voltage drift, but instead designing the circuit so that threshold voltage drift does not affect the OLED current. The dual-gate TFT structure allows the threshold voltage to be compensated through the gate structure itself rather than through signal adjustment, breaking the vicious cycle of increased stress and drift
Solution Approach 2:
The patent changes the electrical parameters of the TFT by using a dual-gate structure where the threshold voltage can be independently controlled through the second gate. This allows the threshold voltage to be set at a predefined value that compensates for drift without requiring changes to the data signal, thereby stabilizing the OLED current against threshold voltage variations
2Reliability
If new TFTs or compensation functions are introduced to relieve threshold voltage drift influence, then the current stability is improved, but the circuit complexity increases
Solution Approach 1:
The patent makes the driving TFT multi-functional by giving it dual gates: one gate controls the OLED current while the other gate compensates for threshold voltage drift. This allows a single TFT to perform both driving and compensation functions, eliminating the need for separate compensation TFTs and reducing overall circuit complexity while maintaining current stability
3Device complexity
If the threshold voltage of driving TFT is not compensated, then the circuit simplicity is maintained, but the light-emitting uniformity deteriorates due to current instability
Solution Approach 1:
The patent changes the threshold voltage parameter through the dual-gate TFT structure, where the second gate can set the threshold voltage to a predefined compensated value. This parameter change is achieved within the existing TFT without adding external compensation circuits, maintaining circuit simplicity while ensuring light-emitting uniformity through stable OLED current
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach effectively compensates for threshold voltage changes, reducing the impact of voltage and light stress on the double-gate TFTs, ensuring stable and uniform light emission by maintaining the threshold voltage at a predefined level, thus improving display results.
Implementation Method 1
the threshold voltage is compensated by pre-charging and threshold voltage programming phases, allowing the OLED to emit light independently of the threshold voltage
Data Source
AI summary
The invention provides an AMOLED pixel driver circuit and pixel driving method. The AMOLED pixel driver circuit has a 6T1C structure, comprising a first thin film transistor (TFT) (T1), a second TFT (T2) forming mirror relation with the first TFT (T1), a third TFT (T3), a fourth TFT (T4), a fifth TFT (T5), a sixth TFT (T6), a capacitor (c1), and an organic light-emitting diode (OLED) (D1), and receiving a first scan signal (Scan1), a second scan signal (Scan2), a third scan signal (Scan3), a data signal (Data), and a predefined voltage (Vpre). The circuit can effectively compensate the threshold voltage of the driving TFT to solve the problem of unstable current flowing through the OLED caused by the threshold voltage drift. Moreover, the use of double-gate TFT as driving TFT allows designating the threshold voltage of the driving TFT through inputting predefined voltage.