LED Display Driving With PWM-Impulse Switching for Low Grayscale
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Solution Overview
Problem
Existing display technologies using light-emitting diodes (LEDs) face challenges in ensuring linearity of brightness and accurate color expression, particularly in low grayscale regions, due to nonlinearity of brightness characteristics and inefficiencies in PWM driving methods.
Innovation Solution
A display driving method that selectively uses PWM signals and impulse signals based on image data characteristics, where PWM is used for upper bits and impulse signals for lower bits when luminance data is below a threshold, adjusting the composition ratio of these signals based on the on-duty ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If PWM driving method is used for all grayscale levels, then the display can maintain consistent brightness control, but brightness linearity deteriorates in low grayscale regions
Solution Approach 1:
The patent segments the grayscale control into two distinct methods: PWM driving for upper bits (higher grayscale levels) and impulse signal driving for lower bits (lower grayscale levels). This segmentation allows each method to be applied in its optimal range, resolving the contradiction between consistency and linearity by ensuring that low grayscale regions use impulse signals for improved linearity while higher regions use PWM for consistent control.
2Manufacturing precision
If impulse signal is used for low grayscale regions, then brightness linearity is improved, but color expression accuracy deteriorates
Solution Approach 1:
The patent applies local quality by using different driving methods for different parts of the grayscale range. Specifically, impulse signals are applied locally to the lower bit regions (lower grayscale levels) where linearity is needed, while PWM is applied to upper bit regions where color accuracy is maintained. This localized application of different driving characteristics resolves the contradiction between linearity and color accuracy.
3Adaptability or versatility
If threshold value is adjusted based on on-duty ratio, then adaptability to different display conditions is improved, but system complexity increases
Solution Approach 1:
The patent implements dynamics by making the threshold value adjustable based on the on-duty ratio of the display. The threshold is not fixed but dynamically determined according to the display's operating conditions, allowing the system to adapt to different refresh rates and duty cycles. This dynamic adjustment resolves the contradiction between adaptability and complexity by using a relatively simple on-duty ratio parameter to control the switching behavior.
Data Source
AI summary
Display driving method and device capable of selecting driving pulse types. The display device includes a plurality of pixels, each of the plurality of pixels including a luminous element and a pixel circuit connected to the luminous element; and a data driver configured to provide image data and luminance data of the pixels to the pixel circuit, wherein the image data comprises multi-bit values including a Most Significant Bit (MSB) and a Least Significant Bit (LSB); and a processor configured to generate a Pulse Width Modulation (PWM) signal based on the multi-bit values when the luminance data is greater than a threshold value, and control light-emission and non-emission of the luminous element through the PWM signal, and drive the LSB using an impulse signal when the luminance data is less than the threshold value.