Adaptive LED Voltage Control for Power Loss Reduction
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Solution Overview
Problem
Existing solid-state lighting systems face inefficiencies in controlling LEDs, particularly due to energy loss in linear control circuits, flickering issues, and thermal stress caused by suboptimal voltage and current management, which affect the overall energy efficiency and reliability of the lighting system.
Innovation Solution
An adaptive control method and apparatus that uses a voltage control device, feedback system, and computing device to independently control voltages supplied to groups of light-emitting elements, determining and maintaining the minimum required voltage to achieve a desired drive current, thereby reducing power losses and mitigating variations in LED performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a linear control circuit is used to control LEDs, then the LED brightness can be varied by changing electrical current, but the circuit dissipates large amounts of energy reducing system energy efficiency
Solution Approach 1:
The patent applies pulse width modulation (PWM) to control LED brightness by switching the LED on and off at high frequency. The average brightness is controlled by adjusting the duty cycle (ratio of on-time to total period), allowing efficient dimming without continuous current flow through linear control circuits, thus reducing energy dissipation.
Solution Approach 2:
The patent replaces the traditional linear resistive control mechanism with an electronic switching mechanism using PWM. Instead of using resistors to drop voltage and control current continuously (which dissipates energy as heat), the system uses a switching element that conducts current only during specific portions of each cycle, substituting the mechanical/resistive control approach with an electronic timing-based approach.
2Loss of energy
If drive current is reduced to dim LEDs, then energy consumption decreases, but LED flickering occurs and some LEDs may turn OFF while others remain ON
Solution Approach 1:
The patent uses PWM switching to control LED dimming, where the LED is switched on and off at high frequency. This periodic switching allows the LED to receive pulsed current rather than continuous reduced current, maintaining stable operation and preventing flickering while achieving dimming effect through duty cycle control.
Solution Approach 2:
The patent changes the control parameter from continuous current magnitude to temporal duty cycle. By controlling the ratio of on-time to off-time in each PWM cycle, the system achieves dimming without reducing the peak current level, thereby maintaining LED stability and preventing flickering that would occur with continuous low current operation.
3Loss of energy
If low switching frequencies are used for PWM control, then energy efficiency improves, but audible noise is generated and thermal stress increases within the LED
Solution Approach 1:
The patent optimizes the PWM switching frequency parameter to a specific range (above 20 kHz) that simultaneously achieves efficient power conversion while avoiding audible noise and excessive thermal stress. This parameter optimization balances the trade-off between energy efficiency and harmful effects by selecting an optimal operating point.
Solution Approach 2:
The patent converts the potentially harmful effect of high-frequency switching into a beneficial outcome by operating at frequencies above the audible range. The high-frequency PWM switching, which could cause noise and thermal stress at lower frequencies, is instead used to achieve efficient dimming without audible noise, as the human ear cannot perceive frequencies above 20 kHz.
Data Source
AI summary
The present invention provides a method and apparatus for adaptive control of a solid-state lighting system consisting of one or more groups of one or more light-emitting elements The invention comprises a voltage control device to provide each group with an independently controllable voltage A feedback system to detect and generate a signal representative of drive currents through the one or more groups A computing device then adaptively evaluates, based on the signal, a required voltage that achieves a desired respective drive current in each of the one or more groups.