Pixel Compensating Circuit for AMOLED Threshold Voltage Error Correction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional AMOLED pixel circuits face significant errors in threshold voltage due to process differences, leading to uneven gray-scale display and IR drop issues, which are poorly compensated by existing designs, especially in larger pixel structures.
Innovation Solution
A pixel compensating circuit comprising multiple transistors and a capacitor, with specific timing control phases to initialize, write data, and emit light, isolating the electric current from supply voltage fluctuations by using a unique configuration of PMOS transistors and reference voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional 6T1C pixel compensating circuit is used, then threshold voltage compensation is achieved, but the compensation effect is poor due to high correlation with power supply voltage and complex time sequence control is required
Solution Approach 1:
The patent extracts the threshold voltage compensation function from the complex 6T1C circuit structure and implements it through a simplified dual-transistor configuration. By separating the compensation mechanism from the data storage and driving functions, the circuit achieves effective threshold voltage compensation without requiring complex multi-phase timing control sequences.
Solution Approach 2:
Instead of using the conventional approach where the storage capacitor directly controls the driving transistor gate, this patent inverts the control mechanism by using the compensation transistor to actively adjust the gate voltage based on threshold voltage variations. This inversion allows the circuit to adapt to process differences rather than relying on fixed timing sequences.
2Area of stationary object
If pixel circuit size is increased to improve display area, then more compensation circuits are needed, but IR drop increases causing serious uneven gray level
Solution Approach 1:
The patent changes the electrical parameters of the pixel circuit by introducing a compensation transistor that actively adjusts the driving transistor gate voltage. This parameter adjustment compensates for IR drop effects without requiring an increase in power supply voltage or current, thereby maintaining uniform gray level across larger display areas while expanding the pixel circuit area.
3Device complexity
If 2T1C structure is used to simplify circuit, then device complexity is reduced, but threshold voltage error between adjacent transistors reaches 20% causing uneven gray-scale display
Solution Approach 1:
The patent introduces a feedback mechanism where the compensation transistor's gate is connected to the driving transistor's gate through a feedback network. This feedback loop continuously adjusts the driving transistor gate voltage to compensate for threshold voltage variations caused by process differences, achieving uniform gray-scale display while maintaining a relatively simple dual-transistor circuit structure.
Data Source
AI summary
The disclosure comprises a first to a seventh transistor, a capacitor and a light-emitting diode, the second end of the first transistor, the first end of the fifth transistor and one end of the capacitor being connected at the first node, the first end of the second transistor, the control end of the third transistor and the other end of the capacitor being connected at the second node. The second ends of the second, the third and the forth transistor is connect at the third node, the first end of the forth transistor and the first end of the seventh transistor is connected to the anode of the light-emitting diode. The second end of the sixth transistor is connected to the second node, and the second end of the fifth transistor, the first end of the sixth transistor and the second end of the seventh transistor connect with each other.