LED Device Compensation Algorithms for Luminance Stability
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Solution Overview
Problem
Existing LED devices face challenges in maintaining constant luminance and power efficiency over their lifetime, as materials in light-emitting elements deteriorate at different rates, leading to differential color aging and varying white point, and prior compensation methods often result in noticeable changes that interfere with device operation.
Innovation Solution
A method involving two compensation algorithms applied over distinct periods to manage luminance changes, allowing the LED device to maintain a constant average luminance or gradually decrease it, with the option to adjust current, voltage, or power to extend the device's lifetime while minimizing perceptible changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a single compensation algorithm is used to maintain constant luminance, then luminance stability is improved, but device lifetime is reduced due to excessive current compensation
Solution Approach 1:
The patent divides the device operation into multiple time periods (first period, second period, third period) and applies different compensation algorithms to each period. During the first period, a first compensation algorithm maintains constant luminance. During the second period, a second compensation algorithm allows gradual luminance decrease. During the third period, a third compensation algorithm maintains constant average luminance. This segmentation resolves the contradiction by applying aggressive compensation only when necessary (first period) and using gentler compensation strategies later to extend device lifetime.
Solution Approach 2:
The patent dynamically adjusts the compensation strategy based on the device's age and operational state. The compensation algorithm transitions from maintaining constant luminance (first period) to allowing gradual decrease (second period) to maintaining constant average luminance (third period). This dynamic adaptation allows the system to optimize between luminance stability and device lifetime at different stages of operation.
2Illumination intensity
If current is increased to compensate for aging, then luminance is maintained, but power consumption increases
Solution Approach 1:
The patent applies partial compensation rather than full compensation throughout the device lifetime. During the second period, instead of fully compensating to maintain constant luminance (which would require excessive current and power), the system allows gradual luminance decrease with minimal compensation. This partial action approach reduces power consumption while still providing some compensation for aging effects.
Solution Approach 2:
The patent changes the compensation parameters over time, transitioning from aggressive current increase to maintain constant luminance (first period) to more conservative current adjustment allowing gradual luminance decrease (second period) to maintaining constant average luminance (third period). This parameter change strategy optimizes the balance between luminance maintenance and power consumption at different operational stages.
3Illumination intensity
If compensation is applied to maintain constant luminance, then display quality is improved, but noticeable changes occur that interfere with operation
Solution Approach 1:
The patent implements periodic compensation with distinct phases: first period with constant luminance maintenance, second period with gradual luminance decrease, and third period with constant average luminance. This periodic structure allows the system to apply compensation in a rhythm that is less perceptible to users, reducing noticeable changes while still maintaining display quality over the device lifetime.
4Adaptability or versatility
If different materials are used for color emission, then color diversity is improved, but differential aging occurs causing white point variation
Solution Approach 1:
The patent applies different compensation algorithms to different color sub-pixels (red, green, blue) based on their individual aging characteristics. Each color material ages at different rates, and the system compensates for each locally rather than applying a uniform compensation approach. This local quality approach maintains color diversity while addressing the differential aging of each material to preserve white point stability.
Data Source
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AI summary
A method for controlling and compensating aging in an LED device includes measuring a performance change in light output of the LED device. The LED device is controlled with a first compensation algorithm derived from the measured performance change, during a first period, to effect a luminance change over time in the light output of the LED device. Subsequently, a second compensation algorithm, derived from the measured performance change, and different from the first compensation algorithm, during a second period, effects a second luminance change over time in the LED device's light output. The second luminance change over time in the second period is different from the first luminance change over time in the first period. Furthermore, the first and second periods together are less than the lifetime of the LED device.