OLED Pixel Circuit With Alternating Dual-Emitter Biasing
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Solution Overview
Problem
Organic Light-Emitting Diode (OLED) display panels experience brightness attenuation and afterimage issues due to long-term light emission, affecting their service life and brightness uniformity.
Innovation Solution
A pixel circuit design incorporating a capacitor to adjust node voltages, allowing two Organic Light-Emitting Diodes (OLEDs) to emit light at different times, with one OLED being reversely biased when the other emits, thereby compensating for threshold voltage non-uniformity and improving brightness uniformity and extending the OLED's service life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If OLEDs emit light continuously, then display function is maintained, but brightness attenuation and afterimage occur reducing service life
Solution Approach 1:
The patent implements periodic action by alternating the emission states of two OLEDs in a pixel. One OLED emits light during the first half of the frame period while the other is reversely biased, then they switch roles in the second half. This periodic alternation ensures that no single OLED emits continuously, thereby preventing brightness attenuation and afterimage effects while maintaining continuous display output.
Solution Approach 2:
The patent applies inversion by reversely biasing one OLED when the other is emitting light. Instead of both OLEDs being in the same state, one is forward-biased for light emission while the other is reverse-biased to recover from degradation. This inverted state assignment solves the contradiction by allowing the emitting OLED to maintain brightness while the reverse-biased OLED recovers, thus improving both service life and brightness uniformity.
2Device complexity
If a single OLED emits light, then pixel circuit is simple, but brightness uniformity deteriorates due to threshold voltage non-uniformity
Solution Approach 1:
The patent segments the single OLED into two separate OLEDs within each pixel. This segmentation allows independent control and biasing of each OLED, enabling one to emit light while the other is reverse-biased for threshold voltage compensation. The segmentation resolves the contradiction by providing the structural basis for implementing alternating emission and reverse biasing, thereby improving brightness uniformity without excessive complexity.
Solution Approach 2:
The patent changes the biasing parameters of the two OLEDs dynamically over time. During the first half of the frame, one OLED is forward-biased for emission while the other is reverse-biased; during the second half, their biasing states are swapped. This parameter change strategy allows the circuit to compensate for threshold voltage non-uniformity through reverse biasing while maintaining relatively simple circuit structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively reduces afterimage and prolongs the service life of OLEDs by ensuring that when one OLED emits light, the other is reversely biased, maintaining brightness uniformity and improving overall display performance.
Implementation Method 1
the driving control sub-circuit includes a capacitor; the driving control sub-circuit is connected with the first scanning signal terminal, a second scanning signal terminal, a second power supply signal terminal, the first node, a second node and a third node respectively, and configured to adjust voltages of the first node, the second node and the third node by controlling voltages at two ends of the capacitor
Implementation Method 2
drive the first light-emitting element to emit light in a first light-emitting time period and not emit light in a second light-emitting time period, and drive the second light-emitting element to emit light in the second light-emitting time period and not emit light in the first light-emitting time period
Data Source
AI summary
A pixel circuit, including: an input sub-circuit, a driving control sub-circuit, a light emission control sub-circuit, a driving sub-circuit, a first light-emitting element and a second light-emitting element, wherein the driving control sub-circuit comprises a capacitor; the input sub-circuit is used for providing a signal of a data signal end to a first node; the driving control sub-circuit adjusts the voltages of the first node, a second node and a third node by means of controlling the voltages at two ends of the capacitor; the light emission control sub-circuit is used for providing a signal of a first power supply signal end to the second node under the signal control of a light emission control signal end; and the driving sub-circuit is used for connecting or disconnecting the connection between the second node and the third node under the signal control of the first node.