LED PFC Control Using Phase-Delay Dimming Feedback
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Solution Overview
Problem
Conventional dimmers, particularly those designed for incandescent light bulbs, are inefficient when used with LED light sources, as they fail to accurately generate phase delays, leading to increased power consumption and efficiency losses during dimming due to increased effective resistance and added circuitry costs.
Innovation Solution
A power factor correction (PFC) controller that utilizes a digital signal processor to determine PFC control parameters from phase delays in a phase modulated signal, generating a PFC switch control signal to maintain efficient power factor correction and reduce effective resistance during dimming, thereby attenuating ripple and optimizing power usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional dimmers are used with LED light sources, then dimming functionality is achieved, but switching efficiency decreases and power factor correction deteriorates
Solution Approach 1:
The controller measures the actual phase delay from the phase modulated signal and uses this feedback to dynamically adjust the PWM duty cycle, ensuring optimal switching efficiency at each dimming level. This closed-loop control prevents the efficiency losses that occur with fixed-parameter conventional dimmers.
Solution Approach 2:
The system dynamically adjusts the PWM duty cycle based on the measured phase delay, transforming the static control approach into a dynamic one. As the phase delay changes with dimming level, the duty cycle adapts in real-time to maintain high switching efficiency throughout the entire dimming range.
2Illumination intensity
If phase delay is increased for dimming, then light intensity is reduced, but effective resistance increases causing power loss
Solution Approach 1:
The system changes the PWM duty cycle parameter in response to phase delay variations. By adjusting this control parameter dynamically, the system compensates for the increased effective resistance that occurs at higher phase delays, maintaining optimal power factor correction across all dimming levels.
3Power
If duty cycle is decreased for dimming, then power demand is reduced, but switching efficiency decreases
Solution Approach 1:
The controller uses feedback from the measured phase delay to determine the optimal PWM duty cycle, creating a closed-loop system that prevents switching efficiency degradation. This feedback mechanism ensures that the duty cycle is adjusted in the most efficient manner possible for each dimming level.
Solution Approach 2:
Rather than simply decreasing the duty cycle linearly with dimming level, the system optimizes the duty cycle parameter based on the measured phase delay, achieving non-linear parameter changes that maintain switching efficiency while still reducing power demand appropriately.
4Reliability
If conventional PFC control is used, then power factor correction is attempted, but additional damping circuitry is required
Solution Approach 1:
The invention extracts and eliminates the need for separate damping circuitry by integrating the ripple attenuation function directly into the PWM control mechanism. The optimized duty cycle control inherently provides the damping effect that would otherwise require additional external components.
Solution Approach 2:
The PWM control system performs multiple functions simultaneously: it controls light output dimming, maintains switching efficiency, and provides power factor correction with inherent ripple attenuation. This multi-functionality eliminates the need for dedicated damping circuitry that would be required in conventional single-function designs.
Data Source
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AI summary
The invention relates to a light emitting diode lighting system comprising a power factor correction controller characterized in that the power factor correction controller comprises an input to receive a phase delay signal indicating a phase delay of a phase modulated dimmer signal and a digital signal processor, coupled to the input, to receive the phase delay signal and determine a control operating parameter from the phase delay signal and to generate a switch control signal using the determined operating parameter to vary an input current to a switching power converter with a phase modulated voltage, wherein the digital signal processor is further arranged to determine start and stop times of each half cycle of a cycle of the phase modulated dimmer signal.