Tapped Linear LED Driver Degradation Compensation
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Solution Overview
Problem
Tapped linear driver (TLD) systems for LED lighting face challenges in maintaining performance when LED chips degrade, leading to reduced light output, increased total harmonic distortion (THD), and flicker due to failed or degraded components, which existing solutions do not adequately address.
Innovation Solution
A controller-based current modulation scheme that detects component degradation and adjusts the current amplitude and switching timing to maintain desired light output, THD, and power factor by implementing a second current modulation scheme with a higher voltage threshold for bypassing LED segments, ensuring continuous current flow and compensating for degrading components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard current modulation scheme is used without degradation detection, then the circuit is simple and cost-effective, but the light output and performance degrade when LED components fail or age
Solution Approach 1:
The controller monitors the forward voltage of LED segments and uses this feedback to detect degradation. When degradation is detected (forward voltage exceeds threshold), the controller automatically switches from a first current modulation scheme to a second current modulation scheme, maintaining light output despite component aging or failure
Solution Approach 2:
The system dynamically adapts the current modulation scheme based on real-time degradation detection. The controller can switch between different modulation schemes and adjust switching timing and current amplitude dynamically to compensate for degraded components, transforming a static system into an adaptive one
2Reliability
If LED segments are bypassed when degradation occurs, then the light output is maintained, but total harmonic distortion increases and flicker appears due to discontinuous current flow
Solution Approach 1:
The system changes the voltage threshold parameter for bypass switching when degradation is detected. Instead of bypassing at the original voltage threshold, the controller uses a higher threshold that accounts for the increased forward voltage of degraded LEDs, ensuring continuous current flow and eliminating THD and flicker issues
Solution Approach 2:
The controller proactively adjusts the bypass switching timing before current discontinuity occurs. By detecting forward voltage changes and pre-adjusting the switching parameters, the system prevents THD and flicker from occurring in the first place, rather than correcting them after they appear
3Reliability
If the forward voltage threshold for bypass switching is increased to compensate for degradation, then continuous current flow is maintained, but the switching timing must be precisely adjusted to avoid blank out durations
Solution Approach 1:
The controller continuously monitors the forward voltage of each LED segment and uses this real-time feedback to precisely determine when to adjust the bypass switching threshold. This feedback mechanism enables accurate timing adjustment without manual calibration, solving the precision requirement
Solution Approach 2:
The system automatically detects its own degradation state through forward voltage monitoring and self-adjusts the switching parameters without external intervention. The controller performs both detection and correction functions, making the system self-sufficient in maintaining optimal performance
Data Source
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AI summary
A LED lighting circuit has a plurality of LED segments connected in series. A switching arrangement is used to selectively bypass at least one LED segment to implement a tapped linear driver approach. Degrading of a component in the LED lighting circuit is detected, so that a first TLD current modulation scheme is implemented when no such degrading is detected whereas a second current modulation scheme, different from the first current modulation scheme, is implemented to compensate for said degrading. Said degrading is leading to an increase in a turning on voltage of one LED segment, and compared to said first current modulation scheme, said second current modulation scheme has a higher voltage threshold at which said LED segment is switched. In this way, protection may be provided for circuit components and the light output may be maintained at the desired level in the event of component degrading, such as LED chip failure or contact resistance changes.