Pixel Driving Circuit Retards OLED Aging via Reverse Voltage
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Solution Overview
Problem
Conventional pixel driving circuits for active matrix organic light-emitting diodes (AMOLEDs) lack the capability to effectively retard the aging process of OLED devices, leading to a decline in luminance and lifespan.
Innovation Solution
A pixel driving circuit design that includes a driving transistor, storage capacitor, data writing unit, reverse control unit, and switch control unit, which applies a reverse voltage across the OLED at the end of each frame to retard aging, extending the OLED's lifespan without adding new control signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pixel driving circuits are used to drive OLED, then the display function is achieved, but the OLED aging process cannot be retarded and lifespan is reduced
Solution Approach 1:
The existing scanning signals are made to serve dual purposes: their primary function of row selection is maintained, while additionally they trigger reverse voltage application for OLED protection. The (n-2)th scanning signal that originally only selected a row now also activates the reverse control transistor to apply reverse voltage to the OLED, making the scanning signal system multi-functional without adding external control signals.
Solution Approach 2:
The pixel driving circuit uses its own internal scanning signals to automatically control the reverse voltage application timing. The circuit self-regulates by detecting the (n-2)th scanning signal and automatically activating the reverse control transistor, eliminating the need for external control systems and making the protection mechanism self-contained within the existing circuit architecture.
2Reliability
If reverse voltage is applied to OLED to extend lifespan, then aging is retarded, but additional control signals are required
Solution Approach 1:
The existing scanning signals are made to serve dual purposes: their primary function of row selection is maintained, while additionally they trigger reverse voltage application for OLED protection. The (n-2)th scanning signal that originally only selected a row now also activates the reverse control transistor to apply reverse voltage to the OLED, making the scanning signal system multi-functional without adding external control signals.
Solution Approach 2:
The pixel driving circuit uses its own internal scanning signals to automatically control the reverse voltage application timing. The circuit self-regulates by detecting the (n-2)th scanning signal and automatically activating the reverse control transistor, eliminating the need for external control systems and making the protection mechanism self-contained within the existing circuit architecture.
3Reliability
If reverse voltage is applied to OLED, then aging process is retarded, but display performance may be affected
Solution Approach 1:
The reverse voltage is applied periodically only during specific timing intervals (when the (n-2)th scanning signal is active) rather than continuously. This periodic application allows the OLED to receive protective reverse voltage during non-display intervals while maintaining normal forward voltage operation during active display periods, thus protecting the OLED without compromising display brightness or performance.
Solution Approach 2:
The reverse voltage application is timed to occur during the (n-2)th row scanning period, which is before the actual data writing and display periods for subsequent rows. This preliminary protective action retards aging before the OLED undergoes stress during normal operation, preventing cumulative damage without interfering with the actual display output.
Data Source
AI summary
A pixel driving circuit is provided. The pixel driving circuit includes a driving transistor (M1), a storage capacitor (Cs) and a data writing unit. The data writing unit is configured to receive an nth-row scanning signal (Vscan (n)) and apply the data voltage (Vdata) to the gate electrode of the driving transistor (M1) in the case that the nth-row scanning signal (Vscan (n)) is valid. The pixel driving circuit further includes: a reverse control unit, receiving an (n−2)th-row scanning signal (Vscan (n−2)) and connected to the cathode of the OLED, and configured to control the cathode of the OLED to receive the (n−2)th-row scanning signal (Vscan (n−2)) in the case that the (n−2)th-row scanning signal (Vscan (n−2)) is valid. A voltage of the (n−2)th-row scanning signal (Vscan (n−2)) is greater than the driving voltage (Vdd), and n is an integer greater than 2.