LED Forward-Voltage Compensation for Aging Light Output
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Solution Overview
Problem
Existing optoelectronic modules suffer from age-related degradation in luminous intensity, which is not effectively addressed by current methods that require costly burn-in processes, temperature monitoring, and optical sensors, leading to inaccurate compensation for luminous intensity changes.
Innovation Solution
An optoelectronic module with an integrated circuit that measures the forward voltage of a light emitting diode to determine degradation, allowing for electronic compensation of luminous intensity changes by adjusting the operating current, thereby eliminating the need for burn-in and optical sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If burn-in processes and temperature monitoring are used to compensate for luminous intensity changes, then compensation accuracy is improved, but manufacturing cost and device complexity increase
Solution Approach 1:
The patent extracts the degradation information measurement from complex optical sensors and temperature monitoring systems, using only the forward voltage measurement of the LED itself to determine luminous intensity degradation. This simplifies the system while maintaining compensation accuracy.
Solution Approach 2:
The LED serves its own measurement function by providing forward voltage information that directly correlates with its degradation state. The same component that degrades also provides the measurement signal, eliminating the need for separate monitoring systems.
2Measurement precision
If optical sensors and complex monitoring systems are used to track luminous intensity changes, then measurement precision is improved, but manufacturing cost increases
Solution Approach 1:
The patent uses the forward voltage measurement capability that already exists in the LED driver circuitry, rather than adding expensive optical sensors. This leverages existing inexpensive components to achieve accurate degradation tracking.
Solution Approach 2:
The forward voltage measurement serves multiple functions: it characterizes the LED at manufacturing, monitors degradation during operation, and enables compensation. A single measurement provides multiple benefits without requiring separate measurement systems.
3Device complexity
If forward voltage measurement is used to determine degradation, then device complexity is reduced, but measurement precision may be compromised
Solution Approach 1:
The patent establishes a feedback relationship where the measured forward voltage directly controls the compensation current adjustment. The system continuously monitors forward voltage and adjusts the operating current to maintain constant luminous intensity, creating a closed-loop control system.
Solution Approach 2:
The patent changes the operating current parameter based on the measured forward voltage to compensate for degradation. By adjusting the current according to the voltage measurement, the system maintains optimal luminous output despite LED aging.
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
The solution provides accurate and cost-effective compensation for age-related luminous intensity changes, maintaining consistent light output without the need for expensive burn-in or complex monitoring systems, enhancing stability and reducing manufacturing costs.
Implementation Method 1
the light emitting diode comprises an epitaxial semiconductor layer stack comprising an active layer for converting the electrical operating current into electromagnetic radiation
Implementation Method 2
the integrated circuit comprises an electrical circuit for measuring the forward voltage of the light emitting diode. Here and in the following, the forward voltage refers in particular to an electrical voltage that drops across the semiconductor layer stack of the light emitting diode
Data Source
AI summary
An optoelectronic module includes at least one light emitting diode that emits light with a luminous intensity during operation. The optoelectronic module also includes an integrated circuit which sets an operating current of the light emitting diode and measures a value of the forward voltage of the light emitting diode during operation. The integrated circuit determines a degradation of the light emitting diode by measuring the value of the forward voltage and increases or decreases the electrical operating current as a function of the measured value of the forward voltage, such that a change in the luminous intensity due to the degradation is at least partially compensated. The integrated circuit or a measurement-control-unit for controlling the integrated circuit includes a memory in which calibration data is stored. The calibration data comprises a value of the forward voltage of the light emitting diode as a reference value for determining the degradation.