Display Backlight Calibration via Duty Cycle Lookup Tables
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Solution Overview
Problem
Conventional backlight modules in liquid crystal display devices face challenges in achieving consistent brightness levels due to process variations, despite using identical current magnitudes for light-emitting diodes.
Innovation Solution
A calibration method and circuit are introduced to drive light emitting units in a display device, utilizing a calibration lookup table to adjust parameters and duty cycles, and defining a brightness-duty-cycle response curve to achieve expected brightness levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If identical current magnitudes are used to drive light-emitting diodes, then the control method is simple, but brightness levels become inconsistent due to process variation
Solution Approach 1:
The patent applies preliminary action by pre-calibrating each light-emitting diode during manufacturing and storing its individual calibration parameters in a lookup table. This pre-characterization allows the system to compensate for process variations without adding complexity to the operational control, as the compensation data is prepared in advance rather than calculated in real-time during display operation.
Solution Approach 2:
The patent changes the control parameter from a single current magnitude to a combination of current magnitude and duty cycle. By introducing duty cycle modulation and using calibration lookup tables that map desired brightness levels to specific current-duty cycle pairs, the system achieves precise brightness control that compensates for LED variations while maintaining operational simplicity through pre-computed lookup tables.
2Measurement precision
If calibration lookup tables with multiple duty cycles are implemented, then brightness level precision is improved, but device complexity increases
Solution Approach 1:
The calibration lookup tables are pre-computed and stored during manufacturing, containing the relationship between duty cycles, current magnitudes, and resulting brightness levels for each LED. This preliminary action transfers the complexity from the operational phase to the manufacturing phase, allowing the runtime system to simply retrieve pre-determined values rather than perform complex calculations, thus achieving high precision without operational complexity.
Solution Approach 2:
The patent replaces complex real-time brightness calculation and adjustment mechanisms with a simplified lookup table retrieval system. Instead of using complex feedback loops or iterative algorithms during operation, the system substitutes these with direct table lookups based on desired brightness levels, significantly reducing computational complexity while maintaining precision through the pre-stored calibration data.
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 method ensures uniform brightness across regions of the display panel by calibrating the output duty cycles and current values for each light emitting unit, effectively addressing the inconsistency in brightness levels.
Implementation Method 1
the backlight module includes multiple light emitting units, and each of the regions corresponds to at least one of the light emitting units
Implementation Method 2
The brightness level of the light-emitting diodes is based on the magnitude of the current flowing through the corresponding the light-emitting diode
Data Source
AI summary
A display device includes a display panel, a backlight module and a circuit. The display panel includes multiple regions. The back light module includes multiple light emitting units, and each region corresponds to at least one of the light emitting units. The circuit includes a calibration lookup table corresponding to a first light emitting unit. The calibration lookup table records a parameter and multiple duty cycles. The circuit accesses the calibration lookup table and determines an output duty cycle according to the duty cycles. The circuit determines a current value of the first light emitting unit to drive the first light emitting unit according to the output duty cycle and the parameter.