Two-Wire LED Dimming Circuit With Pre-Charge Inrush Control
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Solution Overview
Problem
Existing dimming solutions for light sources, particularly those using LEDs, face challenges in managing inrush currents during power switching, which can lead to potential damage and trigger overloads, especially in two-wire systems where the absence of a continuous power supply can result in high peak currents.
Innovation Solution
A pre-charge stage is interposed between the switch and capacitance to limit the inrush current, using a control module that senses the current intensity and adjusts the switching to maintain it within a safe peak value, thereby preventing excessive current flow and ensuring stable power delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a two-wire system with PWM-controlled switch is used for dimming, then circuit simplicity and cost are improved, but inrush current peaks occur when the switch closes causing potential damage and overloads
Solution Approach 1:
The patent applies preliminary action by introducing a pre-charge stage that activates before the main switch closes. This stage gradually charges the capacitance C through a controlled current path, ensuring the capacitor is partially or fully charged before the main power connection is made. This prevents the sudden inrush current that would otherwise occur when the switch closes, while maintaining the simplicity of the two-wire dimming system.
Solution Approach 2:
The patent uses an intermediary element (pre-charge circuit) between the power source and the main capacitance. This intermediary stage provides a controlled current path that limits the charge current to a safe maximum value, acting as a buffer that protects the main switch and other components from damaging inrush currents while still enabling the two-wire dimming functionality.
2Speed
If the switch opens and closes rapidly for PWM dimming control, then dimming responsiveness is improved, but the voltage step and inrush current peak increase
Solution Approach 1:
The pre-charge stage performs preliminary charging of the capacitance before the main switch operates. This ensures that when the switch closes rapidly for PWM dimming control, the voltage step across the capacitor is reduced because the capacitor already holds some charge. This maintains fast switching response while reducing the inrush current peak proportional to the reduced voltage step.
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 limits inrush currents, preventing damage to components and ensuring reliable operation by maintaining the current intensity within safe limits, thus stabilizing the power flow and reducing losses in two-wire dimming systems.
Implementation Method 1
a capacitance located downstream of said switch being traversed by a charge current as said switch is switched on
Data Source
AI summary
In various embodiments, a device for dimming a light source is provided. The device may include a two-wire power supply line having interposed therein a switch for controlling transfer of the power supply towards the light source; a capacitance located downstream of the switch being traversed by a charge current as the switch is switched on; and a pre-charge stage interposed between the switch and the capacitance; the pre-charge stage being configured to limit to a given value the charge current.