LED Current Driving with Brightness Division for Linear Dimming
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Solution Overview
Problem
Conventional LED driving devices face limitations in enhancing brightness resolution due to transient response characteristics and the need to combine pulse and magnitude dimming signals, which can degrade brightness correlation and increase electromagnetic interference.
Innovation Solution
A current driving device with a brightness divider that adjusts magnitude and pulse width values based on brightness values, using a switch and current generator to modulate the drive current, independent of clock signal frequency, thereby enhancing brightness resolution and reducing electromagnetic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the frequency of the clock signal is increased to enhance the average brightness resolution of the LED string, then the brightness resolution is improved, but the linear correlation between the pulse width of the control signal and the average brightness of the LED string is degraded due to transient response characteristics
Solution Approach 1:
The patent uses periodic pulse signals with variable pulse widths to control the LED string brightness. By adjusting the pulse width within each period while maintaining a fixed frequency, the system achieves brightness resolution enhancement without relying on frequency increases, thus preserving the linear correlation between pulse width and average brightness.
Solution Approach 2:
The patent changes the pulse width parameter of the control signal to modulate the average brightness of the LED string. This parameter change approach allows for fine-grained brightness control while avoiding the transient response issues that arise from frequency changes, thereby maintaining linear correlation.
2Measurement precision
If the magnitude of the drive current is modulated to enhance the average brightness resolution of the LED string, then the brightness resolution is improved, but the pulse dimming signal and the magnitude dimming signal have to be combined into the control signal
Solution Approach 1:
The patent extracts the brightness control function into a separate brightness divider module that independently processes the dimming signal. This module generates control signals with adjusted pulse widths without requiring combination with magnitude dimming signals, thereby simplifying the overall system architecture while maintaining enhanced brightness resolution.
Solution Approach 2:
The patent segments the dimming control into independent functional modules: a brightness divider that processes dimming signals separately and generates control signals for the switch. This segmentation eliminates the need for signal combination and reduces system complexity while achieving fine brightness resolution.
Data Source
AI summary
A dimming method is to be implemented by a brightness divider, and includes steps of: (A) determining whether a brightness value is smaller than or equal to a predetermined reference value; (B) when it is determined in step (A) that the brightness value is smaller than or equal to the predetermined reference value, setting a magnitude value that is related to a current generator, and setting a pulse width value that is related to a switch based on the brightness value; and (C) when it is determined in step (A) that the brightness value is not smaller than or equal to the predetermined reference value, setting the magnitude value based on the brightness value, the predetermined reference value and a predetermined order setting, and setting the pulse width value based on the predetermined reference value.