AMOLED Pixel Driving Circuit Threshold Voltage Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional AMOLED pixel driving circuits lack threshold voltage compensation, leading to non-uniformity in threshold voltage and light emission due to technique non-uniformity, especially when using depletion type TFTs where the threshold voltage is negative, causing the TFT to turn off prematurely and lose compensation function.
Innovation Solution
An AMOLED pixel driving circuit with a coupling capacitor between the discharging node and the gate of the driving TFT, which changes the precharging mode to charge the node to a high level and reduce the gate voltage through the coupling capacitor, ensuring sub-threshold saturation turn-off and compensating for the threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a traditional AMOLED pixel driving circuit is used with depletion type TFT, then the circuit can be simplified, but the TFT turns off prematurely and loses threshold voltage compensation function
Solution Approach 1:
The patent introduces a precharging phase before the normal operating phase. During the precharging phase, the coupling capacitor is charged to a high voltage level through a precharging transistor, which prepares the gate voltage to be at a level that prevents premature turn-off. This preliminary action ensures that when the depletion type TFT operates, its gate voltage remains sufficiently high to maintain conduction and enable proper threshold voltage compensation.
Solution Approach 2:
The patent introduces a coupling capacitor as an intermediary element between the driving TFT gate and the precharging circuit. This coupling capacitor transfers the high voltage level from the precharging phase to the normal operating phase, acting as a mediator that maintains the gate voltage at an appropriate level. The coupling capacitor enables the gate voltage to be reduced appropriately during operation while preventing premature turn-off, thus preserving the threshold voltage compensation function.
2Ease of manufacture
If depletion type TFT is used to reduce manufacturing complexity, then large-size AMOLED can be achieved, but non-uniformity of threshold voltage and light emission occurs
Solution Approach 1:
The patent implements a feedback mechanism through the coupling capacitor that automatically adjusts the gate voltage based on the TFT's operating state. The coupling capacitor receives the high voltage from the precharging phase and maintains it at the gate, creating a feedback loop that compensates for threshold voltage variations. This feedback mechanism ensures that even with manufacturing non-uniformities in depletion type TFTs, the threshold voltage compensation function remains effective and light emission uniformity is maintained.
3Reliability
If gate voltage is reduced through coupling capacitor, then sub-threshold saturation turn-off is achieved, but circuit complexity increases
Solution Approach 1:
The patent merges the precharging function and the gate voltage control function into a single integrated circuit structure. The precharging transistor and coupling capacitor work together as a unified mechanism that both charges the gate to a high level and maintains it during operation. By combining these functions, the patent achieves sub-threshold saturation turn-off without proportionally increasing circuit complexity, as the same components serve multiple purposes in the circuit operation.
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 solution enables effective threshold voltage compensation and stable light emission by maintaining the driving TFT in a sub-threshold saturation turn-off state, preventing premature turn-off and ensuring consistent performance.
Implementation Method 1
a coupling capacitor connected to a first terminal of the storage capacitor; a gate initial voltage writing module configured to write an initial voltage signal into a gate of the driving thin film transistor, the first terminal of the storage capacitor, and a second terminal of the coupling capacitor
Data Source
AI summary
There are disclosed an AMOLED pixel driving circuit and driving method thereof, and array substrate. The AMOLED pixel driving circuit comprises a driving thin film transistor (T1), and a gate initial voltage writing module (T2) configured to write an initial voltage signal into a gate of the driving thin film transistor (T1), a first terminal of a storage capacitor (C1), and a second terminal of the coupling capacitor (C2); a data voltage writing module (T3) configured to write a data voltage signal into a source of the driving thin film transistor (T1); a saturation discharging module (T4) configured to connect or disconnect a first terminal of a coupling capacitor (C2) with or from the drain of the driving thin film transistor (T1); an initializing module (T5) configured to connect or disconnect the source of the driving thin film transistor (T1) with or from the second power supply (Vss); and a light emitting control module (T6) configured to connect or disconnect one terminal of the organic light emitting diode (D1) with or from a drain of the driving thin film transistor (T1); the storage capacitor (C1); the coupling capacitor (C2); and an organic light emitting diode (D1). The AMOLED pixel driving circuit and driving method thereof can realize the purpose of sub-threshold saturation turn-off and compensating for threshold voltage of the driving TFT.