Pixel Driving Circuit Threshold Voltage Compensation
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Solution Overview
Problem
The luminance non-uniformity in active matrix organic light emitting displays (AMOLED) due to threshold voltage drift and differences in electrical parameters of thin film transistors, leading to image sticking and reduced production yield, is a significant challenge.
Innovation Solution
A pixel driving circuit with a compensating unit that extracts and offsets the threshold voltage of the driving transistor, eliminating luminance non-uniformity by using a storage capacitor to control the current flowing into the light emitting device, independent of the threshold voltage, thereby avoiding image sticking and display luminance issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thin film transistors are used to construct pixel driving units, then mobility and characteristic stability are improved, but threshold voltage non-uniformity causes luminance non-uniformity and Mura color
Solution Approach 1:
The patent extracts the threshold voltage information from the driving transistor and stores it in a storage capacitor. By separating the threshold voltage storage function from the driving transistor, the circuit can compensate for threshold voltage variations and achieve uniform luminance across different pixels.
Solution Approach 2:
The patent implements a feedback mechanism where the storage capacitor stores the threshold voltage of the driving transistor and feeds it back to the gate terminal. This feedback loop continuously compensates for threshold voltage drift and non-uniformity, maintaining stable driving characteristics.
2Manufacturing precision
If threshold voltage drift is compensated by complex circuit configurations, then luminance uniformity is improved, but device complexity increases and production yield decreases
Solution Approach 1:
The patent merges the threshold voltage storage function with the existing pixel circuit structure by using a storage capacitor connected to the gate terminal. This integration approach compensates for threshold voltage drift without adding complex external circuit configurations, thereby maintaining simple circuit architecture while achieving uniform luminance.
Solution Approach 2:
The storage capacitor automatically stores and compensates for threshold voltage variations without requiring external control signals or complex compensation circuits. The circuit self-adjusts for threshold voltage drift using the stored threshold voltage information, eliminating the need for additional complex control mechanisms.
Data Source
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AI summary
A pixel driving circuit, driving method thereof, an array substrate and display apparatus, the pixel driving circuit comprises: a data line for providing a data voltage (Data); a gate line for providing a scanning voltage (Gate); a first power supply line for providing a first power supply voltage (ELVDD); a second power supply line for providing a second power supply voltage (ELVSS); a light emitting device (D) connected to the second power supply line (ELVSS); a driving transistor (T7) connected to the first power supply line (ELVDD); a storage capacitor (C1) having a first terminal (N1) connected to a gate of the driving transistor (T7) and configured to transfer information including the data voltage to the gate of the driving transistor (T7); a resetting unit configured to reset a voltage across the storage capacitor (C1) as a predetermined signal voltage; a data writing unit configured to write information including the data voltage into the second terminal (N2) of the storage capacitor (C1); a compensating unit configured to write information including a threshold voltage of the driving transistor (T7) and information of the first power supply voltage into the first terminal (N1) of the storage capacitor (C1); and a light emitting control unit configured to write the first power supply voltage into the second terminal (N2) of the storage capacitor (C1) and control the driving transistor (T7) to drive the light emitting device (D) to emit light. The solution can compensate for and eliminating the display non-uniformity caused by the threshold voltage difference of the driving transistor.