LED Controller Dynamic Reference Voltage Adjustment
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Solution Overview
Problem
Conventional LED controllers experience variations in LED current and brightness due to changes in supply voltage and operating temperature, leading to unstable power factor and lumens output.
Innovation Solution
An LED controller that adjusts reference voltages based on the peak voltage of the rectified AC input and LED diode forward voltage to maintain constant current and brightness, ensuring the LED current remains in phase with the rectified AC input voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional LED controllers use fixed reference voltages to control linear regulators, then the device complexity is reduced and ease of manufacture is improved, but the LED current varies with supply voltage and temperature changes causing brightness instability
Solution Approach 1:
The patent implements dynamic reference voltage adjustment by monitoring the actual LED forward voltage and dynamically modifying the reference voltages applied to linear regulators. This ensures that as LED characteristics change with temperature or manufacturing variations, the reference voltages adapt accordingly to maintain constant LED current and brightness, resolving the contradiction between simple fixed-voltage design and stable brightness performance
Solution Approach 2:
The patent employs feedback mechanisms by continuously monitoring the LED forward voltage and using this information to adjust the reference voltages in real-time. The controller measures the actual voltage drop across LEDs and modifies the reference voltages to compensate for variations, creating a closed-loop control system that maintains stable brightness despite changes in supply voltage or temperature
2Use of energy by moving object
If LED controllers sequentially turn on LED strings based on fixed voltage thresholds to achieve high power factor, then the power factor is improved, but the total LED current varies with input voltage changes causing lumens output instability
Solution Approach 1:
The patent changes the reference voltage parameters dynamically based on the monitored LED forward voltage. By adjusting these parameters in response to actual LED characteristics rather than using fixed thresholds, the system maintains both high power factor through sequential LED string activation and stable lumens output by compensating for voltage variations
Solution Approach 2:
The system transitions from static fixed-voltage threshold control to dynamic reference voltage adjustment. The reference voltages are continuously adapted based on actual LED forward voltage measurements, allowing the controller to maintain optimal power factor while ensuring stable brightness output across varying input conditions
3Reliability
If the controller adjusts reference voltages dynamically to maintain constant LED current and brightness, then the brightness stability is improved, but the device complexity increases
Solution Approach 1:
The patent implements self-service by having the system monitor its own LED forward voltage and automatically adjust its reference voltages without external intervention. The controller uses built-in monitoring and adjustment circuitry that operates autonomously, reducing the need for complex external control systems while maintaining brightness stability
Data Source
AI summary
A controller for controlling a plurality of serially-connected LED strings includes a reference voltage generator configured to generate a plurality of reference voltages. The reference voltage generator is further configured to vary the plurality of reference voltages based on a sampled voltage signal. The sampled voltage signal can include one or both of a peak voltage of the rectified input AC voltage and a peak voltage of an LED diode forward voltage Vf. The controller further includes a plurality of linear regulators, each linear regulator coupled between a cathode of a corresponding LED string and a common current sense node, and each linear regulator is configured to regulate a current through a corresponding LED string according to a corresponding reference voltage.