OLED Pixel Drive Timing to Prevent Display Flashing
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Solution Overview
Problem
Self-luminous display devices using organic light-emitting diodes (OLEDs) suffer from a 'flashing phenomenon' where screen brightness changes instantaneously when switching between displays due to variations in transistor characteristics, particularly threshold voltage and mobility, leading to non-uniform brightness across the screen.
Innovation Solution
Implementing a drive circuit that applies a light emission enabling bias to the OLED after correcting the drive transistor and includes a light emission interruption period where the bias is temporarily changed to a non-light emission bias, with a constant light emission disabling process to reverse-bias the OLED, controlling the length of the light emission enabled period by adjusting the interruption period to maintain consistent bias voltage and prevent flashing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If threshold voltage correction is performed by reverse-biasing the OLED, then transistor characteristic variation is reduced, but instantaneous brightness change (flashing phenomenon) occurs when switching between displays
Solution Approach 1:
The patent applies preliminary action by performing threshold voltage correction before the actual light emission period. The OLED is reverse-biased during correction, then switched to forward bias before emission. This timing separation allows correction without affecting the displayed image brightness, resolving the flashing phenomenon while maintaining correction effectiveness
Solution Approach 2:
The patent segments the operation timeline into distinct phases: correction period (reverse bias) and light emission period (forward bias). By dividing these functions temporally, the system achieves both transistor correction and stable brightness display without interference, eliminating the flashing effect
2Illumination intensity
If light emission enabled period is extended to improve brightness, then display visibility improves, but reverse bias application time varies causing brightness non-uniformity
Solution Approach 1:
The patent performs threshold voltage correction as a preliminary action before the light emission period begins. By completing correction in advance during a separate reverse-bias phase, the system ensures consistent transistor characteristics across all pixels before emission starts, eliminating brightness non-uniformity even when emission period varies
Solution Approach 2:
The patent dynamically separates correction and emission operations in time. The correction phase can be adjusted independently from the emission phase duration, allowing flexible control of brightness without affecting correction consistency. This dynamic timing arrangement maintains brightness uniformity while accommodating different display brightness requirements
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
This approach effectively prevents or suppresses the flashing phenomenon by ensuring consistent light emission intensity across the screen, improving brightness uniformity and correcting for transistor characteristic variations, thereby enhancing display quality.
Implementation Method 1
a light-emitting diode adapted to emit light when applied with a bias voltage
Implementation Method 2
An organic electro-luminescence element is known as an electro-optical element used in a self-luminous display device
Implementation Method 3
a holding capacitor coupled to a control node of the drive transistor, wherein the holding capacitor holds a voltage corresponding to a data voltage written to the control node during a light emission interruption period
Data Source
AI summary
A self-luminous display device includes: pixel circuits; and a drive circuit, wherein each of the pixel circuits includes a light-emitting diode, a drive transistor connected to a drive current channel of the light-emitting diode, and a holding capacitor coupled to a control node of the drive transistor, the drive circuit applies a light emission enabling bias to the light-emitting diode after correcting the drive transistor and writing a data voltage to the control node, provides, during a light emission enabled period in which the light emission enabling bias is applied, a light emission interruption period adapted to change the light emission enabling bias to a non-light emission bias with the data voltage held by the holding capacitor, and performs a light emission disabling process, adapted to reverse-bias the light-emitting diode to stop the light emission, for a constant period after the light emission enabled period.