LED Array Current Control via Switch Counting
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Solution Overview
Problem
Existing methods for setting a current source for large light-emitting diode arrays in motor vehicles are complex and inefficient, particularly when needing to achieve uniform brightness and individual switching for various lighting functions, as they require precise control of current fluctuations due to differences in forward voltages and large numbers of LEDs.
Innovation Solution
A system that includes an interface to convert image information into digital signals for controlling switches and a counter to track the number of switched LEDs, allowing the current source to be adjusted based on the counter reading, enabling precise control of current supply for uniform brightness and individual LED activation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If PWM control is used to achieve uniform brightness of individual LEDs, then brightness uniformity is improved, but device complexity increases due to the need for continuous current adjustment
Solution Approach 1:
The patent extracts the brightness control function from individual LED PWM control and implements it at the array level. Instead of controlling each LED individually, the system controls the entire array as a single unit, removing the complex individual control circuitry while maintaining uniform brightness through collective control.
Solution Approach 2:
The patent merges multiple individual LED control channels into a single array-level control mechanism. By combining the control of all LEDs in the array under one current source, the system reduces the number of control signals needed and simplifies the overall control architecture while achieving uniform brightness output.
2Adaptability or versatility
If individual LED switching is implemented for multiple lighting functions, then functionality is improved, but current control complexity increases due to varying numbers of active LEDs
Solution Approach 1:
The patent implements dynamic current adjustment based on the number of actively switched LEDs. The current source automatically adapts its output level according to how many LEDs are currently active, allowing the system to support multiple lighting functions (position lamp, turn indicator, brake light, etc.) without requiring complex manual calibration or fixed current settings.
Solution Approach 2:
The system uses feedback from the switching state of individual LEDs to automatically adjust the overall array current. By monitoring which LEDs are switched on or off for different lighting functions, the control system dynamically modifies the current source output to maintain optimal brightness and efficiency across all operating modes.
3Illumination intensity
If high current is used to achieve sufficient brightness, then illumination intensity is improved, but LED differential resistance increases causing greater voltage variations
Solution Approach 1:
The patent dynamically changes the current parameter supplied to the LED array based on operational requirements and the number of active LEDs. By adjusting the current level rather than using fixed high current, the system achieves sufficient brightness while maintaining more stable voltage conditions and reducing the negative effects of differential resistance variations.
Data Source
AI summary
An arrangement including a light-emitting diode array made up of light-emitting diodes, each light-emitting diode being switchable on and off with the aid of a controllable switch, and including a current source for supplying the light-emitting diode array with current. The arrangement including an interface, to which an input signal having image information for an image, which is displayable with the aid of the light-emitting diode array, may be applied, and the interface converting the input signal into digital signals in which information is contained for switching the controllable switches on and off. The arrangement including a counter, with the aid of which it is possible to detect how many switches are closed or are to be closed within a clock pulse. The current supplied by the current source is controllable as a function of the counter reading.