OLED Pixel Circuit Timing for Color Cast Control
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Solution Overview
Problem
Existing OLED display panels suffer from display color cast due to differences in pixel capacitor charging times of light-emitting elements of different colors, leading to inconsistent luminescence efficiency and display quality.
Innovation Solution
The implementation of a cathode switch transistor connected in series between the cathode of the light-emitting element and a power signal line, with its gate controlled by a second light emission control signal that lags behind the first, ensuring all light-emitting elements charge and emit light simultaneously by adjusting the start times of their control signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If light emission control transistors are connected in series between the anode of light-emitting elements and power signal lines without cathode switch transistors, then the device structure is simpler, but light-emitting elements of different colors do not emit light simultaneously causing color cast
Solution Approach 1:
The patent divides the light emission control into two independent segments: a light emission control transistor connected to the anode and a cathode switch transistor connected to the cathode. This segmentation allows independent timing control of each segment, enabling the anode side to charge pixel capacitors first and the cathode side to switch on later, ensuring simultaneous light emission from different colored sub-pixels and eliminating color cast while maintaining structural clarity.
Solution Approach 2:
The patent implements preliminary action by having the light emission control transistor turn on before the cathode switch transistor. The light emission control transistor first charges the pixel capacitor to the required voltage level, and then the cathode switch transistor turns on to complete the circuit. This sequential preliminary action ensures that all light-emitting elements are ready to emit light simultaneously when the cathode switches on, resolving the color cast issue.
2Manufacturing precision
If the effective pulse of the second light emission control signal lags behind the first light emission control signal, then light-emitting elements of different colors emit light simultaneously improving display uniformity, but the control signal timing becomes more complex
Solution Approach 1:
The patent applies preliminary action by designing the control signal timing so that the first light emission control signal (controlling the anode side) is activated before the second light emission control signal (controlling the cathode side). This preliminary activation of the anode side allows pixel capacitors to charge in advance, and the subsequent cathode switch ensures simultaneous light emission, achieving display uniformity through controlled timing sequence.
Solution Approach 2:
The patent implements periodic action through the use of sequential pulse signals with specific timing relationships. The first light emission control signal and the second light emission control signal are periodic pulses with a controlled time delay between them. This periodic timing pattern ensures that all light-emitting elements undergo the same charging and emission cycle simultaneously, achieving uniform display while managing control complexity through regular timing patterns.
Data Source
AI summary
Provided are a display panel and a driving method thereof, and a display device. A light emission control transistor of a pixel driving circuit in the display panel is connected in series between the anode of a light-emitting element and a first power signal line. A cathode switch transistor is connected in series between the cathode of the light-emitting element and a second power signal line. In at least one light emission stage, the time when the cathode switch transistor is turned on lags behind the time when the light emission control transistor is turned on.