Sweep Driver PWM Control for Color-Stable Display Luminance
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Solution Overview
Problem
Display devices using pulse width modulation (PWM) for light emitting elements like μLEDs or OLEDs face issues with color shift phenomena due to wavelength shifts caused by varying driving currents, leading to image distortion.
Innovation Solution
A display device with a sweep driver that generates sweep signals with varying slopes and time lengths in different modes to improve luminous efficiency and image quality, utilizing a data driver, scan driver, and sweep driver to control pixel luminance through pulse width modulation circuits and current generation circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the light emitting element is driven in the PAM method to adjust gray level by driving current amplitude, then the image brightness can be controlled, but color shift phenomenon occurs due to wavelength shift caused by varying driving current
Solution Approach 1:
The patent changes the driving method from PAM (varying current amplitude) to PWM (varying current duration), where the sweep signal duration is adjusted to represent different gray levels while maintaining constant current amplitude, thereby preventing wavelength shift and color distortion
Solution Approach 2:
The patent introduces a sweep signal that periodically varies in duration to control the light emitting element's on-time, using pulse width modulation where each gray level corresponds to a specific pulse duration within a fixed frequency cycle
2Productivity
If the sweep signal slope is increased to improve luminous efficiency in low luminance modes, then the response speed improves, but the sweep period time length decreases which may affect precision
Solution Approach 1:
The patent dynamically adjusts the sweep signal characteristics (slope and duration) based on the operating mode (high brightness, normal, or always-on display mode), optimizing the balance between response speed and precision for each specific application scenario
Solution Approach 2:
The patent applies different sweep signal parameters to different operating modes, where each mode receives optimized signal characteristics tailored to its specific luminance requirements, rather than using a fixed uniform approach
Data Source
AI summary
Provided is a display device including a display panel including a plurality of pixels, a data driver which provides a data voltage to each of the plurality of pixels, a scan driver which provides a scan signal to each of the plurality of pixels, a sweep driver which provides a sweep signal to each of the plurality of pixels, and a controller. Each pixel includes a light emitting element, a pulse width modulation circuit which receives the data voltage in response to the scan signal, and generates a pulse width modulation signal based on the data voltage and the sweep signal, and a current generation circuit which provides a current to the light emitting element based on the pulse width modulation signal. A slope of the sweep signal is changed in a plurality of modes having different maximum luminances.