LED Circuit Assembly Adjusting Switch-On Times for Uniform Luminance
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Solution Overview
Problem
Existing circuit arrangements for LED lighting suffer from non-uniform luminance due to varying average currents through different LED cascades, leading to brighter and darker areas, and require complex circuitry and expensive LEDs to achieve uniform brightness, which increases costs and complexity.
Innovation Solution
The circuit arrangement adjusts the switch-on times of LED cascades by modifying the voltage at peak value detectors, allowing for identical average currents across all cascades, achieved by decoupling diodes from capacitors and adding voltage offsets, enabling the use of cost-effective LEDs and simplifying circuit design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If LED cascades are connected in series with different numbers of LEDs, then the circuit can operate with rectified AC supply voltage, but non-uniform luminance occurs due to varying average currents through different LED cascades
Solution Approach 1:
The patent applies preliminary action by pre-charging capacitors in parallel with each LED cascade before the switching operation. These capacitors store energy that will be released during the LED's conductive phase, ensuring that each cascade receives appropriate current regardless of its position in the series string. This preliminary energy storage compensates for the inherent current imbalance caused by different cascade configurations.
Solution Approach 2:
The patent implements periodic action through the use of switching elements that periodically connect and disconnect each LED cascade from the circuit. By controlling the switching timing and duration of each cascade, the system creates periodic current pulses that can be adjusted to achieve uniform average current distribution across all cascades, thereby eliminating non-uniform luminance while maintaining series connection operation.
2Illumination intensity
If complex circuitry is used to achieve uniform brightness, then luminance uniformity improves, but device complexity and cost increase
Solution Approach 1:
The patent applies self-service by using the LED cascades themselves as the control mechanism. Each cascade's inherent electrical characteristics (forward voltage, current requirements) are utilized to automatically determine its activation timing and current distribution. The series connection configuration combined with capacitor charging automatically balances the current across different cascades without requiring external complex control circuitry, making the system self-regulating and simplifying the overall design.
Solution Approach 2:
The patent implements parameter changes by modifying the electrical parameters (voltage, current, timing) of the LED cascades dynamically during operation. By adjusting the switching timing and duration of each cascade, and by pre-charging capacitors to specific voltage levels, the system changes the operational parameters of each LED group to achieve uniform luminance output. This approach achieves brightness uniformity through parameter optimization rather than complex circuit architecture.
3Illumination intensity
If expensive LEDs are used to achieve uniform brightness, then luminance uniformity improves, but cost increases
Solution Approach 1:
The patent applies self-service by using the LED cascades themselves as the control mechanism. Each cascade's inherent electrical characteristics (forward voltage, current requirements) are utilized to automatically determine its activation timing and current distribution. The series connection configuration combined with capacitor charging automatically balances the current across different cascades without requiring external complex control circuitry, making the system self-regulating and simplifying the overall design.
Solution Approach 2:
The patent implements parameter changes by modifying the electrical parameters (voltage, current, timing) of the LED cascades dynamically during operation. By adjusting the switching timing and duration of each cascade, and by pre-charging capacitors to specific voltage levels, the system changes the operational parameters of each LED group to achieve uniform luminance output. This approach achieves brightness uniformity through parameter optimization rather than complex circuit architecture.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution ensures nearly equal light emission from all LEDs, simplifies LED selection, and reduces costs by allowing the use of the same LED types across the circuit, while maintaining efficient energy distribution and minimizing power loss.
Implementation Method 1
a capacitor (C32, C22, C12) which is coupled in parallel with the LED cascade (D300 to D313, D200 to D227, D100 to D155)
Implementation Method 2
a diode (D33) which is coupled in series to the LED cascade (D300 to D313), the coupling point of the diode (D33) and the LED cascade (D300 to D313) representing a first node (N31)
Implementation Method 3
at least a first and a second cascade of LEDs, the LEDs forming an overall chain
Data Source
Figure 1a
Figure 1b
Figure 1c
AI summary
The following invention relates to a circuit assembly for operating at least a first (D200 to D227) and a second cascade (D300 to D313) of LEDs. The LED cascades have a different number of LEDs. These are alternately or simultaneously supplied with energy by means of suitable control logic in a manner adapted to the instantaneous value of the rectified alternating supply voltage (701). The LED cascades (D200 to D227; D300 to D313) are assigned to LED units (LE2, LE3), wherein each LED unit (LE2, LE3) comprises a control apparatus for controlling the particular LED cascade (D200 to D227; D300 to D313). The LED units (LE2, LE3) are coupled in series between the two input connections (703, 704), wherein the input connections (703, 704) are formed by the output of a rectifier. Each LED unit (LE2, LE3) comprises a peak value detector which determines the switch-on-time of the particular LED cascade (D200 to D227; D300 to D313). According to the invention, the voltage dropped across the peak detector is modified in order to adapt the average currents of the individual LED units (LE2, LE3), which flow through the LED cascades (D200 to D227; D300 to D313), to one another.