Isolated LED Load Control for Accurate Dimming Feedback
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Solution Overview
Problem
Existing LED light sources face challenges in efficiently controlling power delivery and intensity across a wide range, particularly in transitioning between continuous and discontinuous modes of operation, which affects the consistency and accuracy of light output.
Innovation Solution
A load control device comprising a load regulation circuit, a load sense circuit, and a control circuit that uses sense signals to generate feedback signals for adjusting the load current, employing techniques such as integration, filtering, and blending to determine the average load current, allowing for precise control of LED light source intensity from low to high levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If pulse-width modulation (PWM) dimming is used to control LED light source intensity, then the light output can be dimmed across a wide range, but the average current supplied to the LED light source varies with duty cycle which may affect current regulation precision
Solution Approach 1:
The patent employs feedback control by measuring the actual current through the LED light source and comparing it to the target current. The controller adjusts the PWM duty cycle based on the feedback signal to maintain precise current regulation while enabling wide dimming range. This resolves the contradiction by using feedback to compensate for the varying average current effect.
2Productivity
If LED light source transitions between continuous and discontinuous modes of operation, then power delivery can be adjusted, but the consistency and accuracy of light output may be affected
Solution Approach 1:
The patent implements dynamic mode switching capability that allows the LED driver to operate in continuous conduction mode (CCM) or discontinuous conduction mode (DCM) based on the dimming level and load conditions. The controller dynamically adjusts operating parameters to maintain stable light output across mode transitions, resolving the contradiction between power adjustment flexibility and output consistency.
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
The solution enables precise control of LED light source intensity across a wide range, ensuring consistent and accurate light output by effectively managing the transition between continuous and discontinuous modes of operation, thereby improving the overall performance and efficiency of the LED driver.
Implementation Method 1
a transformer and an output inductor located on a secondary side of the transformer
Implementation Method 2
an output inductor located on a secondary side of the transformer
Implementation Method 3
a winding magnetically coupled to and electrically isolated from the output inductor. The load regulation circuit may be configured to generate a sense signal via the winding and the sense signal may be indicative of a voltage developed across the output inductor
Data Source
AI summary
A load control device may utilize a feedback signal representative of an average magnitude of the load current conducted through an electrical load to control the amount of power delivered to the electrical load. The feedback signal may be generated based on a sense signal that is electrically isolated from the line voltage input of the load control device. Depending on the operational characteristics of the electrical load, the feedback signal may be generated using different techniques. In one example technique, the sense signal may be integrated and filtered to derive the feedback signal. In another example technique, the sense signal may be used in conjunction with an input power of the load control device and an efficiency parameter of the load control device to derive the feedback signal. In yet another example technique, values derived from the foregoing two techniques may be blended together to obtain the feedback signal.