Display Device Green LED Chromaticity Stabilization
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Solution Overview
Problem
Conventional display devices experience instability in chromaticity and luminance at low gradation values, leading to deviations in desired pixel colors due to the inherent properties of LEDs, particularly those emitting green light, which results in unstable lighting control.
Innovation Solution
The display device incorporates a control unit that adjusts the lighting control of first LEDs emitting green light using a corrected gradation value lower than the original value, while maintaining the original gradation value for second LEDs, ensuring a steady-state period occupies less than 50% of the lighting period, thereby stabilizing chromaticity and luminance across pixels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If lighting control is exerted on the first LED (green) using the original gradation value, then the luminance output matches the desired level, but the chromaticity becomes unstable and deviates from the desired chromaticity at low gradation values
Solution Approach 1:
The patent changes the gradation value parameter for the first LED (green) from its original value to a corrected lower value. Specifically, when the original gradation value is 1 or lower, it is corrected to 0, preventing the LED from operating in the unstable low-luminance region where chromaticity varies significantly with small current changes.
2Reliability
If the steady-state period occupies a large proportion of the lighting period, then the chromaticity stability improves, but the luminance output becomes insufficient at low gradation values
Solution Approach 1:
The patent employs periodic pulse-width modulation (PWM) lighting control where the lighting period is divided into sub-frames with different duty ratios. By controlling the proportion of the steady-state period within each lighting period and adjusting the duty ratio, the system achieves both chromaticity stability and adequate luminance output even at low gradation values.
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 maintains or approximates desired chromaticity and luminance at low gradation values, reducing deviations and stabilizing the overall pixel color output, even at very low luminance levels.
Implementation Method 1
a first LED emitting light in a green color and a second LED emitting light in a color other than green
Data Source
AI summary
In a predetermined main frame, a display device exerts lighting control on a first LED in a predetermined pixel with a corrected first LED gradation value lower than a first LED gradation value according to gradation data, and exerts lighting control on a second LED included in the predetermined pixel with a second LED gradation value according to gradation data. The predetermined main frame is at least one main frame included in the plurality of main frames. In the predetermined main frame, the first LED gradation value is lower than a first reference value, the second LED gradation value is lower than a second reference value, and a rate of a steady-state period to a whole lighting period in at least one lighting period is smaller than a predetermined value of less than 50% in at least one sub-frame in which lighting control is exerted over the first LED.