LED Lighting Circuit with Energy Storage for Flicker Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
AC-driven LED lighting systems often experience flicker and reduced power factor due to the minimum forward voltage requirement of LEDs, leading to inefficiencies and visible flickering, and existing solutions either require more LEDs or complex circuitry to mitigate these issues.
Innovation Solution
The use of a capacitor to store energy near peak voltage and discharge it when the input AC voltage is insufficient for LED forward conduction, combined with current control circuits to limit current and divert it to the capacitor, ensuring consistent illumination and reducing flicker.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If LEDs are driven using a rectified AC waveform, then the system can operate from AC power sources, but the LEDs may turn on for only part of the waveform causing visible flicker and lowering power factor
Solution Approach 1:
The patent applies preliminary action by storing energy in a capacitor during the peak voltage portions of the AC waveform before the LEDs need to operate. This stored energy is then released during the portions when the rectified voltage is insufficient, ensuring continuous LED operation and eliminating flicker. The capacitor is charged in advance during high-voltage periods to prepare for low-voltage periods.
Solution Approach 2:
The patent introduces a capacitor as an intermediary energy storage device between the rectified AC source and the LEDs. This intermediary component buffers the voltage fluctuations, absorbing excess energy during peak periods and releasing it during troughs, thereby mediating the connection between the AC source and LED requirements for stable operation.
2Duration of action of stationary object
If LEDs are placed in anti-parallel configuration to enable AC driving, then continuous operation is achieved, but twice as many LEDs are required to produce the same luminous flux
Solution Approach 1:
The patent achieves continuity of useful action by using a capacitor to maintain current flow through the LEDs throughout the entire AC cycle. The capacitor ensures that energy is continuously available to the LEDs, eliminating the need for anti-parallel configurations and allowing continuous operation with the same number of LEDs. The useful action of light production continues uninterrupted through both half-cycles of the AC waveform.
3Illumination intensity
If current is limited through LEDs to divert current to charge storage device, then uniform illumination is achieved, but circuit complexity increases
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the current distribution between the LEDs and the capacitor based on the instantaneous voltage conditions. The control circuit monitors the rectified voltage and adjusts the current splitting ratio accordingly, changing operational parameters to maintain uniform illumination while adapting to the varying AC waveform conditions.
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 approach provides more uniform illumination and reduces flicker in AC-driven LED systems by maintaining current through LEDs during reduced-magnitude portions of the AC waveform, improving power factor and efficiency without the need for additional LEDs or complex circuitry.
Implementation Method 1
The use of a capacitor to store energy near peak voltage and discharge it when the input AC voltage is insufficient for LED forward conduction
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
Some embodiments provide a lighting apparatus including a plurality of lighting circuits coupled in series. Each lighting circuit includes a control circuit configured to selectively provide current to at least one LED and at least one charge storage device coupled to the at least one LED. The control circuit may be configured to cause the at least one charge storage device to be selectively charged from a current source and to be discharged via the at least one LED responsive to a varying input. For example, the control circuit may be configured to limit current through the at least one LED to thereby divert current to the at least one charge storage device.