LED Sensing Light Driving Circuit Hysteresis Control
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Solution Overview
Problem
Current LED sensing light circuits are prone to damage and precision degradation due to peak currents generated by rapid changes in surrounding luminance, leading to repeated triggering errors.
Innovation Solution
The proposed LED sensing light driving circuit incorporates a rectifying filter circuit, sensing signal generating circuit, buck power-supplying circuit, constant current driving circuit, and hysteresis comparator circuit, which includes a photo transistor and resistors to adjust threshold voltages, reducing peak currents and improving precision by controlling the pulse-width modulation signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Schmitt trigger is used to control MOSFET for sensing light, then the sensing function is achieved, but peak currents are generated when surrounding luminance changes rapidly causing LED damage
Solution Approach 1:
The patent applies dynamics by making the threshold voltage adaptive rather than fixed. The threshold voltage dynamically adjusts based on the output signal state (first threshold when off, second threshold when on), creating a hysteresis effect that prevents rapid oscillations during luminance transitions while maintaining accurate sensing capability
Solution Approach 2:
The patent changes the parameter of threshold voltage from a single fixed value to two different values (first and second thresholds) depending on the operational state. This parameter change creates hysteresis that filters out rapid luminance fluctuations, preventing peak currents while preserving triggering precision
2Productivity
If the LED sensing light circuit responds to rapid luminance changes, then light sensing capability is improved, but repeated damages to LEDs occur due to frequent peak currents
Solution Approach 1:
The patent applies beforehand cushioning by pre-establishing a hysteresis mechanism that cushions against rapid luminance changes. The different first and second thresholds create a buffer zone that absorbs sudden luminance variations, preventing the generation of damaging peak currents while maintaining responsive light sensing
Solution Approach 2:
The patent introduces an intermediary mechanism (hysteresis comparator with dual thresholds) between the luminance sensing element and the LED driving circuit. This intermediary filters out harmful rapid fluctuations while allowing legitimate light sensing signals to pass through, protecting LEDs from damage
3Device complexity
If a single threshold voltage is used in the comparator circuit, then circuit complexity is reduced, but triggering precision degrades under rapid luminance changes
Solution Approach 1:
The patent applies dynamics by implementing a dual-threshold system where the threshold voltage changes based on the operational state. The first threshold applies when the output is off, and the second threshold applies when the output is on, creating state-dependent threshold behavior that improves triggering precision without excessive complexity
Solution Approach 2:
The patent uses feedback by connecting the output terminal back to the non-inverting input terminal through a feedback resistor. This feedback mechanism enables the comparator to remember its previous state and maintain hysteresis, improving triggering precision while keeping the circuit relatively simple
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 reduces damage to LEDs and enhances precision by stabilizing the LED driving circuit's response to luminance changes, preventing repeated triggering errors and ensuring smoother on/off transitions.
Implementation Method 1
The sensing signal generating circuit comprises a photo transistor
Data Source
AI summary
A LED sensing light driving circuit includes a rectifying filter circuit, a buck power-supplying circuit, a constant current driving circuit, a sensing signal generating circuit, and a hysteresis comparator circuit. The rectifying filter circuit has a DC output terminal supplies power to the sensing signal generating circuit and the hysteresis comparator circuit via the buck power-supplying circuit. The sensing signal generating circuit reduces a voltage at a first input terminal of the hysteresis comparator circuit in response to increase or decrease of surrounding luminance.