Isolated LED Load Control Using Blended Current Feedback
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Solution Overview
Problem
Existing LED light sources require precise control of current or voltage to maintain proper illumination, and existing dimming methods like PWM and CCR have limitations in efficiently controlling the intensity of LED light sources across varying power ranges.
Innovation Solution
A load control device comprising a load regulation circuit, a load sense circuit, and a control circuit that adjusts the average magnitude of the load current through the LED light source across a power range, using techniques such as integrating and filtering sense signals, and blending different measurement techniques to determine the load current feedback signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If PWM dimming is used to control LED intensity, then the light output can be dimmed across a wide range, but the peak current must be kept constant which limits control flexibility
Solution Approach 1:
The patent implements dynamic control by switching between PWM mode (for high intensity ranges) and CCR mode (for low intensity ranges). The system dynamically adjusts the control method based on the desired output level, allowing flexible intensity control without being constrained by the limitations of a single dimming technique. This dynamic approach enables the LED driver to adapt its behavior to different operating conditions.
2Illumination intensity
If CCR dimming is used to control LED intensity, then the DC magnitude of current can be varied to adjust light output, but it is only applicable when the LED light source is controlled using current load control technique
Solution Approach 1:
The patent creates a universal LED driver capable of supporting both current load control and voltage load control techniques. By integrating both PWM and CCR dimming methods within a single control system, the driver can adapt to different LED light source types and control requirements. This multi-functional approach eliminates the limitation where CCR could only be used with current-controlled LEDs, making the system compatible with a broader range of LED configurations.
3Power
If voltage load control technique is used with LED light sources, then the voltage can be regulated to a particular value, but current balance regulation elements are required to ensure equal current distribution
Solution Approach 1:
The patent replaces physical current balance regulation elements with electronic control mechanisms. By using the control circuit to actively monitor and adjust current distribution through PWM or CCR dimming, the system achieves current balance without requiring additional passive components. This substitution reduces device complexity while maintaining precise voltage and current control capabilities.
4Reliability
If precise control of current or voltage is maintained to ensure proper illumination, then the LED light source operates correctly, but the control system complexity increases
Solution Approach 1:
The patent merges PWM and CCR dimming control methods into a unified control system that can operate in either mode depending on requirements. By combining these techniques within a single integrated driver, the system maintains precise current and voltage control for reliable LED operation while avoiding the need for separate control circuits for each dimming method. This consolidation reduces overall system complexity compared to implementing multiple independent control systems.
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 load control device effectively regulates the power delivered to the LED light source, enabling precise control of intensity from low-end to high-end levels, thereby improving the efficiency and reliability of LED lighting systems.
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
The load regulation circuit may further comprise 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.