SCR Dimmer Circuit Signal Conversion for Stable LED Operation
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Solution Overview
Problem
Current LED dimming technologies using SCR dimmers face issues with unexpected shut-off and flashing/strobing due to low switch-off thresholds at bus line voltage troughs, leading to discontinuous current transitions and IC malfunction.
Innovation Solution
A dimming circuit incorporating a signal conversion circuit that converts input signals into sine-wave voltage signals, which are used in a power factor correction circuit to generate a biasing current correlated with the input signal, ensuring continuous operation and stable power factor correction, even at bus line voltage troughs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a SCR dimmer is used for LED dimming, then energy conservation and controllable lighting are achieved, but unexpected shut-off and flashing/strobing occur when bus line voltage is at wave trough
Solution Approach 1:
The patent introduces a signal conversion circuit as an intermediary between the input signal and the power factor correction circuit. This circuit converts the input signal into a sine-wave voltage signal that is proportional to the absolute value of the input signal, serving as a mediator to ensure the switch-off threshold remains above zero throughout the input signal cycle, thereby preventing unexpected shut-off and flashing while maintaining energy efficiency.
Solution Approach 2:
The patent changes the parameter of the voltage signal fed to the power factor correction circuit by converting it into a sine-wave voltage signal whose absolute value is proportional to the input signal. This parameter transformation ensures that the switch-off threshold remains positive even when the input signal approaches zero, resolving the reliability issue without sacrificing energy conservation.
2Measurement precision
If the switch-off threshold is made proportional to bus line voltage for power factor correction, then power factor correction is achieved, but the switch-off threshold becomes close to zero at voltage trough causing IC malfunction
Solution Approach 1:
The signal conversion circuit acts as an intermediary that transforms the bus line voltage into a sine-wave voltage signal with absolute value proportionality. This intermediary transformation ensures that the voltage signal fed to the power factor correction circuit never reaches zero, maintaining reliable IC operation while preserving accurate power factor correction capability.
Solution Approach 2:
The signal conversion circuit performs preliminary action by converting the input signal into a suitable sine-wave voltage signal before it reaches the power factor correction circuit. This pre-processing ensures that the voltage signal maintains appropriate characteristics (non-zero absolute value) before entering the correction circuit, preventing IC malfunction while enabling accurate power factor correction.
3Ease of operation
If the voltage offset value on the current sampling end exceeds the switch-off threshold, then the IC stops functioning, but continuous current transition is required for smooth dimming
Solution Approach 1:
The signal conversion circuit serves as an intermediary that processes the input signal into a sine-wave voltage signal with absolute value proportionality. This intermediary ensures that the voltage signal presented to the power factor correction circuit maintains a switch-off threshold always greater than zero, preventing the voltage offset from exceeding the threshold and causing IC failure, while enabling smooth continuous dimming operation.
Data Source
AI summary
The present disclosure provides a dimming circuit for SCR dimmer (silicon-controlled rectifier) circuit. The dimming circuit includes a signal conversion circuit for converting an input signal to a sine-wave voltage signal and output the sine-wave voltage signal to a current sampling end of a power factor correction circuit. The dimming circuit also includes the power factor correction circuit to receive the sine-wave voltage signal for correcting power factor. A biasing current is generated according to the input signal and is positively correlated to the input signal, and a sine-wave current signal corresponding to the sine-wave voltage signal is a sum of the biasing current and a primary current of a transformer in the power factor correction circuit.