LED Drive Voltage Adjustment Circuit for Luminance Uniformity
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Solution Overview
Problem
In light-emitting devices with LEDs, voltage drops in drive voltage wiring lines cause luminance unevenness across LEDs, especially when a large number of LEDs are turned on, leading to inconsistent lighting luminance, which existing techniques struggle to fully address, particularly in display devices using local dimming and organic EL displays.
Innovation Solution
A light-emitting device configuration that includes a drive voltage generation circuit, a drive voltage adjustment circuit, and a feedback wiring line to adjust the drive voltage dynamically based on the difference between the voltage supplied by the drive voltage generation circuit and the feedback voltage, ensuring consistent luminance across LEDs by maintaining the voltage at the voltage detection target node equal to the drive voltage output from the generation circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If drive voltage wiring lines are used to supply voltage to multiple LEDs, then the device complexity is reduced, but voltage drops cause luminance unevenness among LEDs
Solution Approach 1:
The patent segments the drive voltage supply system by providing separate drive voltage wiring lines for different groups of LEDs (first plurality and second plurality). This segmentation allows independent voltage compensation for each group, resolving the luminance uniformity issue while maintaining reasonable device complexity.
Solution Approach 2:
The patent changes the voltage parameter by generating different drive voltages (first drive voltage and second drive voltage) for different LED groups based on their respective voltage drops. This parameter adjustment compensates for the voltage drop variations caused by different wiring line lengths, ensuring uniform luminance across all LEDs.
2Ease of operation
If a single drive voltage is supplied to all LEDs, then the ease of operation is improved, but luminance unevenness occurs due to varying wiring line lengths
Solution Approach 1:
The patent implements dynamic voltage adjustment by generating different drive voltages for different LED groups based on their actual voltage drop conditions. This dynamic adaptation allows the system to maintain uniform luminance while keeping the operation simple, as the voltage differences are automatically adjusted based on wiring characteristics.
3Manufacturing precision
If wiring line resistance is reduced to minimize voltage drop, then the luminance uniformity is improved, but the device complexity and cost increase
Solution Approach 1:
Instead of changing the physical wiring line parameters (resistance, cross-section), the patent changes the electrical parameter (drive voltage) to compensate for the voltage drops. This approach achieves luminance uniformity without increasing device complexity or requiring expensive low-resistance wiring materials.
Data Source
AI summary
A light-emitting device is provided with a drive voltage adjustment circuit configured to adjust a voltage value of a drive voltage for driving a plurality of LEDs, and a feedback wiring line for supplying the drive voltage adjustment circuit with a voltage of a voltage detection target node while taking, as the voltage detection target node, a position before a position where a drive voltage wiring line branches on the LED substrate. In accordance with a difference between a voltage supplied from a drive voltage generation circuit and a voltage supplied from the feedback wiring line, the drive voltage adjustment circuit outputs, as the drive voltage, a voltage higher than the voltage supplied from the drive voltage generation circuit.