LED Controller Compensation for Die-to-Die Variation and Temperature Drift
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Solution Overview
Problem
LED-based displays face challenges in maintaining consistent luminosity due to die-to-die variations and temperature drift, which can result in unacceptable light output variations, especially in commercial applications.
Innovation Solution
A system comprising a calibration module, selection module, and control module that generates and uses calibration data to adjust the current through LEDs based on temperature, voltage, and current characteristics, employing a PTAT module to determine junction temperature and adjust the current to maintain predetermined luminosity levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If LEDs are used without compensation for die-to-die variation and temperature drift, then device complexity is reduced, but luminosity consistency deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-characterizing each LED die during manufacturing to create unique lookup tables (LUTs) that store the relationship between forward voltage, temperature, and luminosity. This pre-characterization allows the control system to compensate for die-to-die variations and temperature drift without requiring complex real-time calculations, thereby maintaining luminosity consistency while keeping the control system relatively simple.
Solution Approach 2:
The patent introduces an intermediary element in the form of a lookup table (LUT) that mediates between the LED's electrical characteristics and its luminosity output. The LUT serves as a pre-computed reference that translates forward voltage and temperature measurements into appropriate current adjustment factors, eliminating the need for complex real-time mathematical models while maintaining accurate compensation for variations.
2Stability of the object's composition
If compensation for temperature drift is implemented, then luminosity consistency improves, but device complexity increases
Solution Approach 1:
The patent performs preliminary temperature compensation characterization during manufacturing, storing pre-computed compensation data in lookup tables. This allows the control system to implement temperature drift compensation by simple table lookups and interpolation rather than complex real-time thermal modeling, thereby improving luminosity consistency while minimizing the increase in device complexity.
Solution Approach 2:
The patent implements feedback by continuously monitoring the forward voltage of LEDs and using this information to adjust drive currents based on pre-stored compensation data. The system measures actual LED characteristics, compares them against reference data in the LUT, and applies corrective current adjustments to maintain consistent luminosity despite temperature variations.
3Stability of the object's composition
If strict tolerance specifications are enforced on LEDs, then luminosity consistency improves, but manufacturing cost increases
Solution Approach 1:
The patent changes the approach from selecting LEDs based on strict manufacturing tolerances to characterizing each LED's actual performance parameters and creating individualized compensation profiles. Instead of discarding LEDs that fall outside tight tolerance ranges, the system measures their actual forward voltage-luminosity-temperature relationships and stores correction factors in lookup tables, allowing LEDs with wider tolerances to be used while maintaining luminosity consistency through software compensation.
Solution Approach 2:
The patent creates a digital copy or model of each LED's characteristics by measuring and storing its forward voltage, temperature, and luminosity relationships in lookup tables. This digital twin allows the control system to predict and compensate for each LED's behavior under various conditions, enabling the use of lower-cost LEDs with wider tolerances while achieving the same luminosity consistency that would otherwise require expensive precision-matched components.
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 system effectively compensates for die-to-die variations and temperature drift, ensuring consistent luminosity across a range of temperatures by adjusting the current through LEDs, thereby maintaining desired light output levels.
Implementation Method 1
employing a PTAT module to determine junction temperature
Implementation Method 2
A PN junction of a light emitting diode (LED) emits light when the PN junction is forward-biased
Data Source
AI summary
A system including a calibration module, a selection module, and a control module. The calibration module is configured to generate calibration data for a plurality of light emitting diodes (LEDs). The calibration data include current through the LEDs and corresponding luminosities of the LEDs. The selection module is configured to select one of a plurality of templates corresponding to the LEDs. The selected template includes at least one of temperature, current, and voltage characteristics of the LEDs. The control module is configured to determine a temperature of the LEDs and adjust current through the LEDs based on the temperature, the selected template, and the calibration data to maintain a luminosity of the LEDs at a predetermined luminosity.