Photosensor Circuit Reducing Noise in LCD Backlight Control
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Solution Overview
Problem
Conventional photosensors used in LCDs are prone to noise interference and require additional digital signal processing, which increases complexity and power consumption, especially in portable devices.
Innovation Solution
A photosensor design incorporating a light receiver, voltage selector, current generator, and output unit, with a selection transistor and current generating transistor, that generates a sensor current based on received light, and a display device that includes a voltage converter to control luminance, reducing noise interference and the need for expensive DSP chips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional photosensor with storage capacitor and switch TFT is used, then photocurrent can be stored and output, but the device is easily interrupted by noise and requires expensive DSP chip
Solution Approach 1:
The invention extracts and eliminates the storage capacitor and switch TFT from the photosensor circuit. By removing these components that are prone to noise interference, the patent achieves noise-free operation without requiring additional DSP processing, thus reducing both noise susceptibility and device complexity
Solution Approach 2:
The patent replaces the complex conventional photosensor structure with a simpler alternative using only two TFTs (sensor TFT and current generator TFT) without storage capacitor or switch TFT. This simpler structure achieves comparable functionality without the noise issues and expensive DSP requirements of the conventional design
2Power
If conventional photosensor with storage capacitor is used, then photovoltage can be generated, but additional components increase device complexity and power consumption
Solution Approach 1:
The invention merges the functions of the storage capacitor and switch TFT into the current generator TFT itself. The current generator TFT simultaneously performs the functions of charge storage and switching, eliminating the need for separate components and reducing overall device complexity while maintaining photodetection functionality
Solution Approach 2:
The current generator TFT serves multiple functions: it acts as the photosensitive element, stores the generated charge, and functions as the switching element for output control. This multi-functional design reduces the total component count and simplifies the circuit structure while maintaining all necessary operations
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 provides a stable and efficient method to control backlight luminance in LCDs, reducing noise interference and power consumption by directly converting sensor current into control voltage, enhancing the performance and energy efficiency of portable devices.
Implementation Method 1
a light receiver receiving an external light and generating a photovoltage corresponding to an amount of the received light
Data Source
AI summary
A photosensor is provided, which includes: a light receiver receiving an external light and generating a photovoltage corresponding to an amount of the received light; a voltage selector selectively outputting the photovoltage and a reference voltage; a current generator generating a sensor current depending on an output voltage of the voltage selector; and an output unit selectively outputting the sensor current from the current generator.