AMOLED Pixel Driving Circuit Threshold Voltage Drift Compensation
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Solution Overview
Problem
The threshold voltage drift in the driving TFT of AMOLED display panels affects the light-emitting luminance and reduces the lifetime of the OLED display panel, leading to non-uniform luminance and shortened transistor and panel lifetimes.
Innovation Solution
A pixel driving circuit with a driving compensation unit that generates a predetermined voltage independent of the threshold voltage, ensuring consistent light-emitting current and extending the operational lifetime of the driving transistor and display panel by alternating the operation of two driving components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a 2T1C driving circuit is used to drive OLED, then the circuit structure is simple and easy to manufacture, but the threshold voltage drift of the driving TFT affects light-emitting luminance uniformity and reduces display panel lifetime
Solution Approach 1:
The pixel circuit is divided into two separate driving TFTs (first driving TFT and second driving TFT) that alternately drive the OLED. This segmentation allows one driving TFT to rest while the other is active, reducing cumulative stress and threshold voltage drift accumulation, thereby improving luminance uniformity and display panel lifetime while maintaining a relatively simple circuit structure
Solution Approach 2:
The first and second driving TFTs operate in alternating periodic cycles, with each driving TFT being activated for a certain period and then switched off for a rest period. This periodic action prevents continuous operation stress on a single driving TFT, reducing threshold voltage drift and extending display panel lifetime while maintaining simple circuit architecture
2Illumination intensity
If the driving TFT operates continuously to maintain OLED luminance, then the light-emitting luminance is maintained, but the lifetime of the driving TFT and display panel is reduced
Solution Approach 1:
The first driving TFT and second driving TFT alternately operate in periodic cycles, with each driving TFT being activated during its turn and then switched off for a rest period. This periodic operation maintains OLED luminance during active periods while allowing driving TFTs to recover during rest periods, thereby extending driving TFT and display panel lifetime
Solution Approach 2:
The circuit alternates between using the first driving TFT and the second driving TFT, effectively discarding one from active duty while the other works, and then recovering the discarded one for future use. This alternating use allows driving TFTs to recover from stress and threshold voltage drift, extending their operational lifetime while maintaining display performance
Data Source
AI summary
There is provided a pixel driving circuit, a driving method, an array substrate and a display device. The pixel driving circuit comprises: a first switching unit, being turned on or off according to a first scanning signal to control a transmission of a data signal; a first charging unit, having first terminal connected to a second terminal of the first switching unit; a first driving unit, having control terminal connected to a second terminal of the first charging unit, first terminal connected to a first power supply, and second terminal connected to a second power supply; a first driving compensation unit, for producing a predetermined voltage at the control terminal of the first driving unit, so that a current flowing through the light-emitting device is independent of threshold voltage of the first driving unit. Accordingly, the threshold voltage is prevented from affecting light-emitting luminance, luminance uniformity is ensured.