LED Driver Circuit Minimizing Flicker and Heat
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Solution Overview
Problem
Semiconductor light sources, such as LEDs, experience flicker due to output current ripple from rectified mains AC voltage, and existing solutions like linear regulator type output stages generate waste heat and are inefficient.
Innovation Solution
A driver device with a controllable linear regulator, such as a MOSFET, is used to regulate the voltage in proportion to the pulsating component of the rectified AC, minimizing waste heat and flicker by dissipating only the pulsating DC component.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a linear regulator type output stage is used to reduce flicker, then flicker is reduced, but waste heat increases and energy efficiency deteriorates
Solution Approach 1:
The patent applies dynamics by making the linear regulator's regulation action variable rather than constant. The control circuit dynamically adjusts the regulation strength based on the instantaneous ripple voltage, applying strong regulation only when ripple is present and reducing or eliminating regulation when ripple is absent, thereby minimizing waste heat while maintaining flicker reduction effectiveness
Solution Approach 2:
The patent changes the operational parameters of the linear regulator by controlling it to operate in different modes (full regulation, partial regulation, or bypass) based on the detected ripple conditions. This parameter change allows the system to optimize between flicker reduction and energy efficiency by adjusting the regulator's action according to real-time electrical conditions
2Stability of the object's composition
If sufficiently large capacitors are used to reduce flicker, then flicker is reduced, but cost and space requirements increase
Solution Approach 1:
The patent introduces a control circuit as an intermediary between the power conversion stage and the output. This control circuit actively manages the ripple by dynamically controlling the linear regulator, replacing the need for large passive filtering capacitors with an active control mechanism that achieves the same flicker reduction effect with smaller, less expensive components
Solution Approach 2:
The patent replaces the passive mechanical filtering approach (large capacitors) with an active electronic control system. The control circuit uses electronic switching and regulation to filter ripple, substituting the bulky passive filtering mechanism with a compact active system that achieves superior performance
3Stability of the object's composition
If a linear regulator operates in linear mode to reduce ripple, then flicker is reduced, but the regulator generates excessive heat that accelerates capacitor aging
Solution Approach 1:
The patent applies periodic action by having the linear regulator operate intermittently rather than continuously. The control circuit enables the regulator to act strongly during ripple peaks and then disengage or reduce action during troughs, creating a periodic operation pattern that reduces average heat generation while maintaining ripple suppression effectiveness
Solution Approach 2:
The patent uses partial action by applying linear regulation only to the extent necessary to suppress ripple, rather than maintaining constant full regulation. The control circuit modulates the regulator's action to provide just enough correction to eliminate flicker, avoiding the excessive heat generation that would result from continuous full-strength regulation
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
This approach effectively reduces flicker and minimizes waste heat, maintaining optimal performance even as capacitors age, while incorporating protective functions like overcurrent and short circuit protection.
Implementation Method 1
A controllable linear regulator is coupled between a second node of the output and the second rail. The controllable linear regulator is configured to dissipate a pulsating DC component of the voltage between the first and second rails as heat
Data Source
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AI summary
A driver device for semiconductor light sources comprises a switched-mode power supply receiving rectified AC and converting it into DC between a first rail and a second rail. An output is provided for coupling the one or more semiconductor light sources. A first node of said output is coupled to the first rail. A controllable linear regulator is coupled between a second node of the output and the second rail. A control circuit produces a control signal to a control input of the controllable linear regulator, controlling the amount of current passed by the controllable linear regulator. The control circuit is configured to produce said control signal in proportion to the potential of the second node of the output.