LED PFC Control Using Phase-Modulated Dimming Signals
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Solution Overview
Problem
Conventional dimming systems for LED lighting suffer from inefficiencies, including increased power demand and reduced switching efficiency when dimming, due to the inability to effectively manage phase delays and maintain a constant effective resistance, leading to inefficient power use and added system 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 the link voltage when dimming, thereby minimizing the effective resistance perceived by the voltage source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional dimming systems are used for LED lighting, then dimming function is achieved, but switching efficiency decreases and power demand increases at lower dimming levels
Solution Approach 1:
The system dynamically adjusts the link voltage based on the dimming level. At full brightness, the link voltage is maintained at a higher level (e.g., 400V), but when dimming occurs, the link voltage is reduced to a lower level (e.g., 120V). This dynamic voltage adjustment allows the PFC controller to maintain optimal switching efficiency across different dimming levels by adapting the operating conditions to match the actual power requirements.
Solution Approach 2:
The patent changes the operating parameters of the PFC circuit by detecting phase delays in the phase-modulated signal and using these to control the link voltage. The system transitions from a fixed high-voltage operation to a variable voltage operation where the link voltage parameter is changed according to the dimming level, thereby maintaining switching efficiency while reducing power consumption at lower brightness levels.
2Illumination intensity
If conventional dimming systems are used for LED lighting, then dimming function is achieved, but effective resistance increases at lower dimming levels
Solution Approach 1:
The system dynamically adjusts the link voltage to maintain a relatively constant effective resistance. By reducing the link voltage when dimming occurs, the system compensates for the natural increase in effective resistance that would otherwise occur at lower power levels. This dynamic adjustment ensures more stable operation and reduces the need for additional damping circuitry.
3Reliability
If link voltage is maintained at high level during dimming, then power factor correction is maintained, but switching efficiency decreases
Solution Approach 1:
The system dynamically adapts the link voltage level based on the actual operating conditions. The PFC controller continuously monitors the phase delays and adjusts the link voltage accordingly. This allows the system to maintain adequate power factor correction while operating at lower voltages during dimming, thereby improving switching efficiency without completely sacrificing power factor correction performance.
Solution Approach 2:
The patent changes the link voltage parameter from a fixed high value to a variable value that adapts to the dimming level. This parameter change allows the system to optimize the trade-off between power factor correction and switching efficiency by operating at appropriate voltage levels for each dimming condition.
4Stability of the object's composition
If additional damping circuitry is added to manage phase delays, then system stability is improved, but device complexity and cost increase
Solution Approach 1:
The system uses the existing phase-modulated signal and its phase delays to control the link voltage adjustment. The phase delays, which are already present due to the dimming operation, are repurposed as control information for the PFC controller. This self-service approach eliminates the need for separate damping circuitry by making the system use its own operational characteristics for control.
Solution Approach 2:
The phase delays in the phase-modulated signal serve multiple functions: they indicate the dimming level to the control system and simultaneously serve as the control signal for adjusting the link voltage. This multi-functionality eliminates the need for additional dedicated damping or stabilization circuitry, as the same signal performs both dimming indication and PFC control.
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
The solution maintains switching efficiency and power factor correction without increasing the effective resistance, even at lower dimming levels, thus conserving power and reducing system costs by eliminating the need for additional damping circuitry.
Implementation Method 1
A power factor correction (PFC) controller utilizes a digital signal processor to determine PFC control parameters from phase delays in a phase modulated signal
Data Source
AI summary
A light emitting diode (LED) lighting system includes a power factor correction (PFC) controller that determines at least one power factor correction control parameter from phase delays of a phase modulated signal. In at least one embodiment, a peak voltage of the phase modulated signal is a PFC control parameter used by the PFC controller to control power factor correction and generation of a link voltage by a PFC LED driver circuit. The phase delays are related to a peak voltage of the phase modulated signal. Thus, in at least one embodiment, detecting the phase delay in one or more cycles of the phase modulated signal allows the PFC controller to determine the peak voltage of the phase modulated signal.