LED Driver PFC Control for Stable DALI Bus Power
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Solution Overview
Problem
Existing LED drivers experience output voltage fluctuations due to tapping off the DC link voltage during DALI bus activities, which affect the light output of connected lighting means, and current solutions either reduce dim level fluctuations at the cost of worsening total harmonic distortion (THD) performance.
Innovation Solution
An LED driver with actively switched PFC circuitry and a bus interface, where the voltage supply for the bus interface is tapped off from the output voltage of the active PFC circuitry, with a control circuitry that adjusts its feedback control time constant faster during DALI bus activities to minimize fluctuations, and additional features like EMI filters and optocouplers for isolation and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the voltage supply for the bus interface is tapped off from the output voltage of the active PFC circuitry, then the bus interface can be powered conveniently, but voltage fluctuations occur during DALI bus activities which affect light output stability
Solution Approach 1:
The patent segments the power supply system by introducing a separate DC-DC converter that isolates the bus interface power supply from the PFC output voltage fluctuations. This converter takes the tapped voltage and converts it to a stable bus voltage, effectively separating the power tapping function from the voltage stabilization function.
Solution Approach 2:
The DC-DC converter acts as an intermediary between the PFC output voltage and the bus interface power supply. It mediates the voltage fluctuations by converting the unstable tapped voltage into a stable bus voltage, preventing direct transmission of fluctuations to the bus interface and light output.
2Stability of the object's composition
If the PFC controller is switched to fast operation to reduce DALI frame disturbance on V bus, then voltage fluctuations are reduced, but total harmonic distortion (THD) performance worsens
Solution Approach 1:
The DC-DC converter serves as an intermediary that decouples the PFC controller operation mode from the bus voltage stability. It absorbs the voltage fluctuations regardless of PFC switching speed and provides stable bus voltage, allowing the PFC to operate in fast mode without compromising voltage stability or incurring THD penalties.
Solution Approach 2:
The system dynamically adapts by using the DC-DC converter's regulation capability to maintain stable bus voltage under varying PFC operation conditions. The converter adjusts its conversion ratio to compensate for voltage variations caused by different PFC switching speeds, enabling optimal performance without THD compromise.
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 effectively reduces voltage fluctuations during DALI bus activities, improving light output stability while maintaining efficient power factor correction and minimizing harmonic distortion.
Implementation Method 1
further comprising an optocoupler configured to isolate the control circuitry from the bus interface
Data Source
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AI summary
The invention relates to an LED-driver, comprising an actively switched PFC circuitry and a bus interface for a wire-bound bus, wherein a voltage supply for the bus interface for powering the bus is tapped off the output voltage of the active PFC circuitry, further comprising a control circuitry for a feedback control of an output voltage of the actively switched PFC by controlling a switch of the PFC, wherein the time constant of the feedback control of the control circuitry is faster during time periods in which the bus interface is transmitting or receiving signals, compared to time periods without activity.