Differential Optical Sensor Circuit for Common-Mode Noise Rejection
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Solution Overview
Problem
Conventional optical sensors are unable to accurately sense light irradiated on them due to inefficiencies in converting light into electrical signals and processing these signals.
Innovation Solution
The optical sensor incorporates a photodiode and a differential current integrator, which includes two output terminals to generate positive and negative output voltage signals, effectively suppressing common-mode noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional optical sensors convert light into electrical signals, then light sensing function is achieved, but measurement precision deteriorates due to common-mode noise interference
Solution Approach 1:
The patent divides the single output signal into two separate output signals (first output voltage signal and second output voltage signal) from the differential current integrator. This segmentation allows the system to process and compare multiple signals to eliminate common-mode noise, thereby improving measurement precision while addressing the harmful noise interference.
Solution Approach 2:
The patent converts the harmful common-mode noise into a useful differential signal by using a differential current integrator. The noise that would normally degrade measurement precision is transformed into a measurable differential output that can be processed to extract the actual light sensing information, turning the harmful factor into a beneficial measurement mechanism.
2Measurement precision
If conventional optical sensors process electrical signals through single-ended configuration, then circuit simplicity is maintained, but measurement precision deteriorates due to noise susceptibility
Solution Approach 1:
The patent segments the signal processing into two parallel paths within the differential current integrator, generating two separate output voltage signals. This segmentation improves measurement precision by enabling differential processing while maintaining relatively simple circuit implementation through the use of standard operational amplifier configurations.
Solution Approach 2:
The patent inverts the conventional single-ended signal processing approach by adopting a differential output configuration. Instead of processing a single signal and rejecting noise, the system generates two complementary signals and uses their difference to inherently reject common-mode noise, improving precision without proportionally increasing complexity.
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
This configuration enables the optical sensor to accurately sense light intensity with higher immunity to common-mode noise, resulting in more precise light sensing compared to conventional optical sensors.
Implementation Method 1
Optical sensors such as proximity sensors and ambient light sensors sense a light and convert it into electrical signals
Data Source
AI summary
An optical sensor is provided. The optical sensor includes a photodiode and a differential current integrator. The differential current integrator includes a first input terminal, a second input terminal, a first output terminal and a second output terminal. The first input terminal of the differential current integrator is connected to the photodiode. The second input terminal of the differential current integrator is coupled to a first reference voltage.