LED Driver Dimmer Detection Using Low-Pass Filter Noise Removal
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Solution Overview
Problem
Conventional LED drivers with dimmer detection often introduce spurious noise causing flicker in LED lights, which can be mitigated by increasing the threshold voltage, but this decreases power factor and efficiency and increases harmonic distortion.
Innovation Solution
The implementation of a low-pass filter and AC detector configuration in the LED driver system, which filters out high-frequency noise and uses a transformer to manage voltage levels, preventing spurious pulses without affecting power factor or efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the threshold voltage is increased to filter out spurious noise, then flicker is reduced, but power factor decreases and efficiency is reduced and harmonic distortion increases
Solution Approach 1:
The patent introduces an intermediary low-pass filter between the AC detector and the pulse width modulation controller. This filter mediates the signal transmission by blocking high-frequency spurious noise while allowing the fundamental AC waveform to pass through, thereby eliminating flicker without requiring an increased threshold voltage that would harm power factor and efficiency.
2Object-affected harmful factors
If the threshold voltage is increased to filter out spurious noise, then flicker is reduced, but harmonic distortion increases
Solution Approach 1:
The low-pass filter acts as an intermediary that selectively attenuates high-frequency components (spurious noise) while preserving the fundamental frequency and its harmonics. This allows the system to eliminate flicker caused by high-frequency noise without introducing additional harmonic distortion, as the filter's cutoff frequency is carefully selected to pass relevant signal components.
3Ease of operation
If conventional dimmer detection is used, then LED brightness can be controlled, but spurious noise causes flicker
Solution Approach 1:
The low-pass filter serves as an intermediary in the dimmer detection circuit, cleaning the detected AC waveform by removing spurious high-frequency noise before it is processed by the pulse width modulation controller. This maintains the brightness control functionality while eliminating the flicker caused by noise-induced false dimmer detection signals.
Solution Approach 2:
The system uses feedback from the AC detector to monitor the actual AC waveform at the LED driver input. By comparing this feedback signal with the expected waveform and filtering out deviations (spurious noise), the system can accurately detect dimmer control signals while ignoring noise, thereby maintaining stable LED brightness without flicker.
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 solution effectively eliminates flicker in LED lights without reducing power factor or overall efficiency and increasing harmonic distortion, ensuring stable and efficient operation.
Implementation Method 1
The implementation of a low-pass filter and AC detector configuration in the LED driver system, which filters out high-frequency noise
Implementation Method 2
uses a transformer to manage voltage levels, preventing spurious pulses without affecting power factor or efficiency
Data Source
AI summary
An LED driver system including an input receiving a rectified AC conductive angle modulated voltage on a rectified node, a converter, a low-pass filter, and AC detector, and a driver network. The converter is coupled to the rectified node and includes a power switching device coupled to a switching node, in which the power switching device is controlled to convert the rectified AC conductive angle modulated voltage to an output voltage and output current. The low-pass filter is configured to filter voltage of the switching node to provide a filtered voltage. The AC detector receives the filtered voltage and provides a current sense signal indicative thereof. The driver network controls duty cycle of the power switching device based on the current sense signal.