LED Field Current Reduction via Staggered Group Activation
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Solution Overview
Problem
Current LED field control systems experience high pulse current loads during activation, leading to increased demands on the supply and EMC issues, particularly in large LED applications like headlamps with tens of thousands of LEDs, necessitating a reduction in maximum current and flattening of the current curve.
Innovation Solution
A control and regulating system that groups LEDs and allocates different reference times for activation and deactivation, distributing impulses over a clock cycle, allowing neighboring LEDs to be in different groups to reduce peak current and even out the current curve, with the number of groups determined based on pulse width mean values or simulation optimization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If all LEDs are activated simultaneously at time tein=0, then the luminance control is simple and uniform, but the maximum pulse current load increases significantly
Solution Approach 1:
The LED field is divided into multiple groups (k groups), where each group contains a subset of LEDs. By activating these groups at different times within the same clock cycle, the patent segments the simultaneous activation into staggered activations, thereby reducing the peak current load while maintaining luminance control capability.
Solution Approach 2:
The patent employs periodic activation patterns where different groups of LEDs are activated at different time periods within a clock cycle. This periodic staggering of activation times distributes the current demand over time, reducing the maximum pulse current while maintaining the overall luminance output through PWM control.
2Device complexity
If all LEDs are activated simultaneously, then the control system is simple, but the supply demands and EMC problems increase
Solution Approach 1:
The LED field is segmented into multiple groups with different activation times, which distributes the electromagnetic interference events over time rather than having them occur simultaneously. This temporal segmentation reduces the cumulative EMC impact on the power supply and surrounding electronics.
Solution Approach 2:
The control system pre-assigns different activation times to different LED groups within the clock cycle. This preliminary timing arrangement ensures that high current demands are distributed over time, preventing simultaneous electromagnetic interference peaks and improving EMC conditions before they occur.
3Device complexity
If neighboring LEDs are allocated to the same group, then the control is simplified, but the luminance distribution uniformity decreases
Solution Approach 1:
The patent applies different activation timing characteristics to different spatial locations by allocating neighboring LEDs to different groups. This creates local variations in activation timing that prevent synchronized switching of adjacent LEDs, thereby maintaining luminance uniformity while the overall control structure remains systematic and manageable.
Data Source
AI summary
A control/regulating system is provided for controlling/regulating an LED field with n LEDs, where n>2, with outputs at which control/regulating signals for controlling/regulating controllable switching elements can be tapped. Activation/deactivation times(teinjpj,tausjpj)of impulses can be defined by the control/regulating system through the control signals/regulating signals. One and/or several controllable switching elements can be actuated during the determined impulses for closing or opening. A number of k groups can be specified. Each LED is allocated to one of the k groups such that each of the k groups mj contains LEDs, where 1≤j≤k and Σj=1kmj=n apply, a reference time αj=α1 . . . αk can be determined for each group and the activation and deactivation time(teinjpj,tausjpj)of the impulse for each LED of every group can be determined as a factor of the reference time αj=α1 . . . αk, where 1≤pj≤mj applies.