LED Bias Current Control for Display Aging Compensation
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Solution Overview
Problem
LED arrays in display technologies experience performance degradation over time due to aging, leading to diminished user experience, as the magnitude and wavelength of light emitted by LEDs change, affecting the stability and uniformity of light output.
Innovation Solution
A device with dedicated test LEDs and controllable current sources measures current-voltage performance characteristics at different times to determine bias current properties, allowing for adjustments to maintain consistent light output, including adjusting the duration, magnitude, or target brightness of the bias current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If LEDs are operated continuously over time, then the display can provide light output, but the LED performance degrades due to aging causing changes in light magnitude and wavelength
Solution Approach 1:
The patent applies preliminary action by measuring I-V characteristics at multiple predetermined time points (manufacturing completion, device turn-on, and periodic intervals thereafter) to detect LED aging trends before they cause noticeable performance degradation. This proactive measurement approach allows the system to characterize aging patterns and adjust operating parameters in advance to maintain light output stability throughout the operational lifetime.
Solution Approach 2:
The patent implements feedback by using measurement circuits to continuously monitor I-V characteristics of the LEDs and using this information to determine appropriate bias current adjustments. The system feeds back the measured performance data to the controllable current source, which automatically adjusts the bias current magnitude or duration to compensate for aging effects and maintain consistent light output over time.
2Reliability
If the bias current is adjusted to compensate for LED aging, then light output stability is maintained, but additional measurement and control circuitry is required
Solution Approach 1:
The patent applies universality by designing measurement circuits that can characterize I-V properties of multiple LEDs through selective activation, rather than requiring dedicated measurement circuits for each LED. The controllable current source serves multiple functions: it provides the primary display drive current and also functions as a test current source for aging characterization by switching between display mode and measurement mode. This multi-functionality reduces overall device complexity while maintaining light output stability.
Solution Approach 2:
The patent implements self-service by having the display device's own controllable current source and measurement circuits perform the aging characterization and compensation without requiring external testing equipment. The system uses its existing display drive infrastructure to conduct I-V measurements and automatically adjusts its own operating parameters, eliminating the need for separate external measurement and control systems.
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 ensures the stability and uniformity of light output over the lifetime of the display by compensating for changes in LED performance, maintaining the brightness and color consistency of the LEDs.
Implementation Method 1
an LED array may be used in various display technologies. As the display is operated, the LEDs within the LED array experience aging, which may cause the performance of some of all of the LEDs to decrease
Implementation Method 2
a plurality of measurement circuits, each of which is configured to measure a current-voltage (I-V) performance characteristic of at least one of the plurality of first LEDs
Data Source
AI summary
A device includes a plurality of first LEDs, a plurality of second LEDs, at least one controllable current source that is configured to generate at least one bias current for driving the plurality of first LEDs and the plurality of second LEDs, and a plurality of measurement circuits, each of which is configured to measure a current-voltage (I-V) performance characteristic of at least one of the plurality of first LEDs. A property of a first bias current of the at least one bias current is determined as a function of at least two measurements of the I-V performance characteristic of the at least one of the plurality of first LEDs, and the at least two measurements of the I-V performance characteristic are acquired while the first bias current is applied to the at least one of the plurality of first LEDs and the plurality of second LEDs.