LED Driver Control Circuit for Power-On Current Overshoot
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Solution Overview
Problem
The existing control circuits in lighting devices experience current overshoot during power-on, leading to potential damage or breakdown of the light source load.
Innovation Solution
The control circuit incorporates a signal sampling module, constant power regulation module, and negative feedback regulation module to ensure that the current input to the light source load remains constant during power-on by correlating the output currents with the voltage limiting terminal, preventing current overshoot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a non-isolated constant current circuit is used to reduce component count, then device complexity is reduced, but switching noise increases and signal integrity deteriorates
Solution Approach 1:
The control circuit is divided into isolated and non-isolated sections. The isolated constant current circuit handles LED driving, while the non-isolated circuit handles dimming control. This segmentation allows noise-sensitive LED control to be electrically isolated from noise-generating dimming signals, reducing switching noise without requiring complete isolation of the entire system.
Solution Approach 2:
An optocoupler is introduced as an intermediary component between the isolated and non-isolated circuits. The optocoupler transfers control signals while providing electrical isolation, enabling the system to reduce overall component count while maintaining signal integrity and reducing switching noise in the LED driving portion.
2Object-affected harmful factors
If an isolated constant current circuit is used to reduce switching noise, then signal integrity is improved, but device complexity and component count increase
Solution Approach 1:
The control circuit is divided into isolated and non-isolated sections. The isolated constant current circuit handles LED driving, while the non-isolated circuit handles dimming control. This segmentation allows noise-sensitive LED control to be electrically isolated from noise-generating dimming signals, reducing switching noise without requiring complete isolation of the entire system.
3Adaptability or versatility
If input voltage range is expanded to accommodate varying mains voltage, then adaptability is improved, but circuit design complexity increases
Solution Approach 1:
The circuit uses parameter-changing components including NTCS thermistors for inrush current limiting and soft-start control, and switching elements that operate across a wide voltage range (90-264VAC). These components are selected and configured to automatically adapt to varying input voltage conditions without requiring complex voltage regulation circuitry.
Data Source
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Figure 3a~3e
AI summary
The invention disclose a control circuit and a lighting device, relates to a technical field of illumination. Compared with the prior art, in the power-on process of the control circuit, the voltage input to the driving input terminal of the constant current driving module rises slowly, resulting in the current overshoot phenomenon of the light source load. In the control circuit disclosed by the present invention, because the output current of the first regulation output terminal is positively correlated with the output voltage of the voltage limiting terminal, and the output current of the second regulation output terminal is negatively correlated with the output voltage of the voltage limiting terminal, during the power-on process of the control circuit, that is, during the voltage at the voltage limiting terminal is changed from zero to the first threshold value, the current input to the driving input terminal can be relatively constant, so that the working current on the light source load connected to the constant current driving module is also relatively constant, and the phenomenon of current overshoot generated on the light source load is avoided.