OLED Pixel Circuit Voltage Reset for Brightness Uniformity
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Solution Overview
Problem
OLED display pixel circuits face issues with non-uniform brightness due to parasitic capacitance between nodes, leading to inconsistent grayscale transitions and potential afterimages from drifting threshold voltages.
Innovation Solution
A pixel circuit design that includes a drive transistor, drive control module, node reset module, and light emitting control module, where the node reset module provides the drive transistor's gate with a first voltage terminal before light emission, and the light emitting control module provides the anode with the same voltage, ensuring consistent voltage levels and preventing threshold voltage deviations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional pixel circuit is used, then the display can operate, but non-uniform brightness occurs due to parasitic capacitance between nodes
Solution Approach 1:
The patent applies preliminary action by resetting the gate voltage to the first voltage terminal before the light emitting control module activates the drive transistor. This pre-reset operation eliminates the parasitic capacitance effect in advance, ensuring that when the transistor subsequently drives the light emitting device, the gate voltage is stable and uniform, thereby preventing non-uniform brightness without interfering with the light emission process
Solution Approach 2:
The patent segments the voltage control process into distinct stages: a reset stage where the gate is charged to the first voltage terminal, and a light emission stage where the drive transistor operates. This temporal segmentation allows the parasitic capacitance to be cleared during the reset stage before it can cause brightness non-uniformity during the light emission stage
2Duration of action of stationary object
If the drive transistor operates continuously, then light emission is maintained, but threshold voltage drifts causing afterimages
Solution Approach 1:
The patent implements periodic action by introducing a reset cycle where the gate voltage is periodically returned to the first voltage terminal. This periodic reset prevents continuous operation-induced threshold voltage drift by regularly clearing accumulated charges, thereby eliminating afterimages while maintaining the ability to sustain light emission over time through controlled cycles of operation and reset
3Adaptability or versatility
If grayscale transitions are performed, then display flexibility is achieved, but inconsistent brightness occurs due to voltage variations
Solution Approach 1:
The patent applies equipotentiality by ensuring the gate voltage is reset to a consistent first voltage terminal potential before each light emission cycle, regardless of the intended grayscale level. This establishes a uniform starting voltage condition that eliminates variations caused by residual charges from previous grayscale states, ensuring consistent and accurate grayscale transitions without brightness inconsistency
Data Source
AI summary
The disclosure discloses a pixel circuit, a method for driving the same, and a display panel. Before a drive control module controls a drive transistor to drive a light emitting device to emit light, a node reset module provides a gate of the drive transistor with a signal of a first voltage terminal; and also while the node reset module is providing the gate of the drive transistor with the signal of the first voltage terminal, a light emitting control module provides a first electrode of the drive transistor with the signal of the first voltage terminal.