Light-Sensing LED Drive Circuit for Inrush and Self-Illumination Control
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Solution Overview
Problem
Conventional light sensing lamps using visible light are prone to self-illumination interference and have poor circuit reliability due to large inrush currents when ambient light changes.
Innovation Solution
A light sensing drive circuit comprising a filtering and rectifying module, power module, light sensing module, sampling module, and main control module, which generates a control signal to adjust the driving voltage and duty cycle, reducing inrush currents and eliminating self-illumination effects by sampling light when the LED is off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a MOS transistor is connected in series at the output light source to control light sensing, then the light sensing function is achieved, but large inrush current occurs when the MOS transistor is turned on, reducing circuit reliability
Solution Approach 1:
The patent applies preliminary action by controlling the MOS transistor to be turned off during the light sensing period and only turned on after sampling is complete. This prevents inrush current during normal operation while still allowing the transistor to function when needed. The controller manages the timing sequence to avoid simultaneous activation of the LED module and sampling circuitry.
2Measurement precision
If visible light is used for light sensing, then the light sensing lamp can detect ambient light, but it is easily affected by self-illuminating light sources, making light intensity detection inaccurate
Solution Approach 1:
The patent implements periodic action by alternately switching between the LED module operation and the light sensing sampling. The controller periodically turns off the LED module to create a dark period during which ambient light can be accurately sampled without interference from self-illumination. This periodic switching enables precise measurement of ambient light intensity while eliminating the harmful effect of the lamp's own light.
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
Improves circuit reliability by preventing large inrush currents and accurately detecting ambient light intensity, eliminating stroboflash and self-illumination interference.
Implementation Method 1
a light sensing module, configured to connect with the power module, and to detect ambient light intensity according to the supply voltage to generate a light sensing signal
Data Source
AI summary
A light sensing drive circuit and a lamp are provided. The light sensing drive circuit includes a filtering and rectifying module configured to generate a rectified voltage according to the commercial power; a power module configured to generate a supply voltage according to the rectified voltage; a light sensing module configured to generate a light sensing signal according to ambient light intensity and the supply voltage; a sampling module configured to generate a sampling signal according to the rectified voltage; a main control module configured to generate a control signal of a preset duty cycle according to the light sensing signal and the sampling signal when the drive module is turned off by the control signal; a drive module configured to generate a driving voltage according to the control signal and the rectified voltage so as to drive the internal LED module to emit light.