LED Drive Circuit Feedback for Balanced Dimming and Color Control
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Solution Overview
Problem
Existing LED lighting systems face challenges in efficiently adjusting light intensity and color temperature while maintaining optimal operating parameters, particularly in dimming scenarios, due to variations in load current and voltage regulation.
Innovation Solution
A controllable lighting device incorporating a drive circuit with a feedback mechanism that adjusts load current and bus voltage to achieve target intensity and color temperature by controlling the conductive state of a switching device, using pulse-width modulation and feedback loops to regulate current and voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If PWM dimming technique is used to adjust light intensity, then the average current supplied to LED light source can be varied to change intensity, but the peak current through the LED light source remains constant which may cause uneven current distribution in parallel strings
Solution Approach 1:
The patent employs feedback control by monitoring the actual current through each parallel string of LEDs and adjusting the PWM duty cycle or current reference accordingly. This ensures that current imbalance in parallel strings is detected and corrected, maintaining reliable operation while achieving the desired light intensity reduction through PWM dimming.
2Illumination intensity
If CCR dimming technique is used to adjust light intensity, then the DC magnitude of current can be varied continuously, but the LED light source may operate away from optimal operating points reducing efficiency
Solution Approach 1:
The patent dynamically adjusts the operating parameters of the LED driver circuit based on the dimming level and load conditions. By varying the current reference, PWM duty cycle, or switching frequency in response to feedback signals, the system maintains optimal operating points across different intensity levels, ensuring efficient energy utilization throughout the dimming range.
3Reliability
If voltage load control technique is used to regulate LED light source, then voltage across LED light source can be regulated to ensure proper operation, but current balance regulation elements are required for parallel strings increasing device complexity
Solution Approach 1:
The patent employs a universal control approach where a single feedback mechanism and control circuit serve multiple functions: regulating voltage across the LED light source, balancing current in parallel strings, and enabling dimming operations. By integrating these functions into one control system, the patent eliminates the need for separate current balance regulation elements while maintaining proper operation and reducing device complexity.
4Illumination intensity
If PWM dimming is used to reduce light intensity, then average current can be reduced, but the switching frequency and duty cycle control increase device complexity
Solution Approach 1:
The patent implements self-service control where the LED driver circuit automatically adjusts PWM duty cycle and switching frequency based on feedback from current sensing and dimming control signals. The control circuitry self-regulates to maintain optimal operation without requiring complex external control mechanisms, reducing overall device complexity while achieving precise intensity control.
Data Source
AI summary
A controllable lighting device may comprise a drive circuit characterized by one or more cycles and a control circuit configured to control the drive circuit to conduct a load current through a light source of the lighting device. The control circuit may be configured to determine one or more operating parameters of the lighting device during a present cycle of the drive circuit based on a feedback signal indicative of a peak magnitude of the load current conducted through the light source. The control circuit may be able to adjust an average magnitude of the load current conducted through the light source so as to adjust an intensity of the light source towards a target intensity based on the operating parameters.