OLED PWM Controller Gray Level Duty Cycle
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Solution Overview
Problem
Consumer expectations for digital display performance, particularly in maintaining accurate and consistent image quality, are not met due to noticeable variations at low gray levels, especially in multi-display setups, where current PWM selection is based on peak luminance rather than varying gray portions over time.
Innovation Solution
A computing device with a PWM controller that calculates the gray portion of an input display signal and selects a PWM duty ratio based on this calculation to output a pulse-modulated display signal, independently of peak luminance, ensuring improved image quality for low-luminance features.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If PWM is selected based on peak luminance, then power consumption is reduced, but image quality at low gray levels deteriorates
Solution Approach 1:
The patent changes the selection parameter for PWM from peak luminance to average gray level. By calculating the average gray level of the entire frame and comparing it against a threshold, the system dynamically adjusts PWM duty cycle based on overall image brightness characteristics rather than peak values, thereby improving low gray level image quality while managing power consumption effectively
Solution Approach 2:
The patent implements a feedback mechanism where the average gray level of the display content is continuously calculated and used to adjust the PWM duty cycle. This closed-loop approach allows the system to respond to actual image content characteristics and optimize both power consumption and image quality based on real-time conditions
2Manufacturing precision
If PWM duty cycle is increased to improve low luminance image quality, then mura defects are reduced, but power consumption increases
Solution Approach 1:
The patent makes the PWM duty cycle dynamic by base it on the calculated average gray level of the frame. Rather than using a fixed duty cycle, the system adjusts the PWM parameters dynamically according to the actual image content, increasing duty cycle when gray levels are low (to reduce mura) and decreasing it when overall brightness is high (to save power)
3Manufacturing precision
If PWM is applied to all frames, then image quality consistency improves, but processing complexity increases
Solution Approach 1:
The patent simplifies the PWM selection process by changing from complex peak luminance analysis to a simpler average gray level calculation. This parameter change reduces processing complexity while still achieving consistent image quality across different frames by applying PWM based on overall image brightness characteristics
Data Source
AI summary
Varying electrical currents are selectively applied to each pixel within an OLED display to create desired images. High applied electrical currents to groupings of nearby pixels create high luminance features, while low applied electrical currents to groupings of nearby pixels create low luminance features. A combination of a high luminance and low luminance features may be present on the OLED display. Pulse-width modulation (PWM) is often used to increase the current applied to the OLED display by modulating the applied current, particularly when creating low luminance features. The presently disclosed systems and methods detect a gray portion of an image to be presented, and select PWM independently of peak luminance based on the detected gray portion. The allows the OLED display to display low-luminance features at high quality, even when high-luminance features are also present within a frame.