Light-Emitting Module Current Profiling for Phosphor Afterglow
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Solution Overview
Problem
Light-emitting devices with multiple phosphors of different afterglow characteristics suffer from afterglow issues due to the varying persistence times of these phosphors, leading to color imbalances and visible afterglow effects.
Innovation Solution
A driving method for light-emitting devices that includes a maximum current supply period followed by a continuous or stepwise reduction in current to reduce afterglow, specifically controlling the current to minimize the emission luminance of phosphors with longer afterglow characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple phosphors with different afterglow characteristics are used in a light-emitting device, then color diversity and emission intensity are improved, but afterglow imbalance and color instability occur due to different persistence times of the phosphors
Solution Approach 1:
The patent applies dynamic current control by varying the driving current over time in two stages: initially applying a first current value and then applying a second current value that is smaller than the first. This dynamic adjustment compensates for the different afterglow characteristics of multiple phosphors, allowing the system to maintain color balance while utilizing the emission intensity benefits of multiple phosphor types.
Solution Approach 2:
The patent implements periodic driving cycles with distinct current phases. By periodically switching between a higher initial current and a reduced subsequent current, the system manages the afterglow decay of different phosphors in a controlled manner, preventing color instability while maintaining overall emission intensity.
2Object-generated harmful factors
If a large current is supplied to eliminate tailing phenomenon in phosphor backlights, then afterglow is reduced, but current instability and control complexity increase
Solution Approach 1:
The patent segments the current supply into distinct temporal phases: an initial phase with a first current value and a subsequent phase with a reduced second current value. This segmentation allows targeted management of phosphor afterglow characteristics without requiring complex continuous control, simplifying the overall control system while effectively reducing afterglow.
Solution Approach 2:
The patent changes the current parameter over time by transitioning from a higher first current value to a lower second current value. This parameter change strategy directly addresses afterglow reduction while maintaining simple control logic, avoiding the need for complex control mechanisms.
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 method effectively reduces afterglow and shortens its duration, maintaining color balance and brightness consistency in light-emitting devices.
Implementation Method 1
a light-emitting device including a light-emitting element and a light-emitting part that contain two or more types of phosphors with different afterglow characteristics adapted to be excited by the light-emitting element
Implementation Method 2
two or more types of phosphors with different afterglow characteristics adapted to be excited by the light-emitting element
Implementation Method 3
a light-emitting part that contain two or more types of phosphors with different afterglow characteristics adapted to be excited by the light-emitting element
Data Source
AI summary
A method of driving a light-emitting device includes driving the light-emitting device having a light-emitting element and a light-emitting part that contains two or more types of phosphors adapted to be excited by light emitted from the light-emitting element, the two or more types of phosphors having respectively different afterglow characteristics. The driving of the light-emitting device includes supplying a current to the light-emitting element during a conducting period including a maximum current supply period in which a maximum current in the conducting period is supplied to the light-emitting element, and subsequent to the maximum current supply period, a current reduction period in which the current supplied to the light-emitting element is reduced continuously or stepwise from the maximum current.