LED Driving Circuit Grouping for Luminance Uniformity
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Solution Overview
Problem
Conventional LED arrays connected in series or parallel configurations face challenges in controlling current and voltage uniformly, leading to uneven luminance, color, and color temperature due to varying forward voltages of LEDs, resulting in complex and inefficient driving circuits.
Innovation Solution
The proposed solution involves grouping LEDs with a common cathode connected to a current source and individual anodes connected to constant voltage sources, allowing for precise control of current and voltage through switches controlled by PWM signals, ensuring even brightness and stable color output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LEDs are connected in series with one another in a string, then current can be regulated through the string, but light un-balance happens due to different forward voltages of LEDs
Solution Approach 1:
The patent segments the LED string into multiple parallel-connected LED groups instead of connecting all LEDs in series. Each group contains LEDs with similar forward voltage characteristics, and each group is equipped with its own current regulator. This segmentation allows independent control of current in each group, compensating for voltage variations and ensuring uniform luminance across all LEDs.
2Ease of operation
If multiple LEDs are connected in parallel with respective voltage and current control, then each LED receives proper control, but the circuit structure becomes complex
Solution Approach 1:
The patent merges the control functions by connecting multiple LED groups in parallel rather than providing separate control circuits for each individual LED. Each parallel group shares a common current regulator, which simplifies the overall circuit structure while still allowing independent control of each group. This approach reduces the number of control components needed compared to fully individual LED control.
3Adaptability or versatility
If LEDs with different rated voltages are connected in series, then they can be driven together, but uneven brightness occurs due to voltage variations
Solution Approach 1:
The patent applies local quality by grouping LEDs with similar forward voltage characteristics together in parallel branches. Each parallel group is designed with LEDs that have matched voltage ratings, and each group has its own current regulation capability. This local matching and independent regulation ensures that each group operates at optimal brightness, achieving overall uniform luminance across the entire LED array despite variations in LED voltage characteristics.
Data Source
AI summary
The present disclosure relates to a lighting apparatus, a driving circuit and driving method thereof. The lighting apparatus comprises a plurality groups of lighting elements and a driving circuit. Each group of lighting elements comprises at least one lighting element, each lighting element in a same group having a cathode connected to a common cathode node. The driving circuit comprises a plurality of voltage sources, each having a terminal connected to an anode of a respective lighting element in each group of lighting elements; and a plurality of current sources, each having a terminal connected to the common cathode node of a respective group of lighting elements.