LED Dimming Circuit Noise Suppression and Response Speed
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Solution Overview
Problem
Existing LED lamps face challenges in retrofitting into low-voltage lighting systems, as reducing the RMS voltage to dim them leads to inefficient dimming due to exponential voltage behavior, causing noise and flicker, especially when using phase-cut dimmers, resulting in unstable light output.
Innovation Solution
A circuit arrangement with a signal processor that operates in noise suppression and dimming modes, receiving a phase-cut operating voltage, and adjusts its mode based on voltage variations to provide a dimming signal for the LED unit, reducing noise and ensuring quick brightness adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If noise suppression mode is used to filter operating voltage, then noise and flicker are reduced, but response speed to user operations becomes slow
Solution Approach 1:
The patent applies dynamics by making the filter characteristics adjustable between two modes: noise suppression mode with high-pass filtering to eliminate flicker and noise, and dimming mode with lower-pass filtering to respond quickly to user operations. The system dynamically switches between these modes based on operational requirements, resolving the contradiction between noise reduction and response speed.
Solution Approach 2:
The patent changes the filtering parameters dynamically by switching between different cutoff frequencies. In noise suppression mode, a first cutoff frequency is used to heavily filter noise, while in dimming mode, a second (lower) cutoff frequency is used to allow faster response. This parameter change enables the system to optimize performance for different operational states.
2Ease of operation
If phase-cut dimming is used to control LED brightness, then brightness adjustment is achieved, but noise and flicker increase due to exponential voltage behavior
Solution Approach 1:
The patent introduces an intermediary high-pass filter between the phase-cut dimming circuit and the LED driver. This filter acts as a mediator that blocks the noise and flicker components generated by phase-cut dimming while allowing the useful dimming signal to pass through. The filter transfers only the relevant frequency components to the LED driver, eliminating harmful effects.
Solution Approach 2:
The patent extracts and removes the harmful noise and flicker components from the operating voltage using high-pass filtering. By taking out these unwanted frequency components before they reach the LED driver, the system achieves clean brightness control without the exponential voltage behavior problems associated with direct phase-cut dimming.
3Object-affected harmful factors
If low-pass filter is used for noise suppression, then noise is reduced, but substantial phase-shift or time lag occurs
Solution Approach 1:
The patent applies dynamics by switching between two filtering modes: noise suppression mode with high-pass filtering that eliminates noise without significant time lag, and dimming mode with lower-pass filtering that accepts some noise but maintains faster response. This dynamic approach avoids the permanent time lag problem of continuous low-pass filtering.
Solution Approach 2:
The system periodically switches between filtering modes based on operational state. During normal operation, noise suppression mode is active. When user interaction is detected, the system transitions to dimming mode for rapid response. This periodic switching between modes optimizes both noise reduction and response time.
Data Source
AI summary
A circuit arrangement for controlling the brightness of at least one LED unit is described by the disclosure. The circuit arrangement, in one example, includes an input for receiving a phase-cut operating voltage from a power supply, a signal processor, connected with the input and adapted to provide a dimming signal for the at least one LED unit from the operating voltage. To allow an efficient reduction of noise in the dimming signal but simultaneously to allow an improved dimming of the LED unit, the signal processor are configured to operate at least in a noise suppression mode and a dimming mode. A control device is provided, connected with the signal processor and configured to set the mode of the signal processor in dependence of the variation in the operating voltage.