Optical Signal Detection Circuit with DC Bias Adjustment
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Solution Overview
Problem
The existing optical signal detection circuits face challenges in accurately adjusting detection sensitivity due to non-linearity between load resistance adjustments and detection sensitivity, especially when temperature or power supply variations affect the photodiode and transimpedance amplifier characteristics, leading to erroneous noise detection or detection delays.
Innovation Solution
An optical signal detection circuit that includes a differential amplification circuit with a current addition mechanism to adjust DC load currents for load resistors, ensuring accurate adjustment of DC biases between positive and negative-phase signals, thereby maintaining detection sensitivity in line with temperature and power supply changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If load resistance is adjusted to change detection sensitivity, then detection sensitivity changes, but the relationship is non-linear making accurate adjustment difficult
Solution Approach 1:
The patent changes the adjustment parameter from resistance value to voltage value. By using a voltage adjustment unit that applies different voltages to the load resistor, the detection sensitivity can be adjusted in a linear and predictable manner. The control unit receives adjustment commands and converts them into corresponding voltage values, creating a direct linear relationship between the control input and detection sensitivity output.
2Reliability
If temperature or power supply variations occur, then photodiode and transimpedance amplifier characteristics change, but existing circuits cannot compensate, leading to detection errors
Solution Approach 1:
The patent implements a feedback mechanism where the control unit continuously monitors the detection output and adjusts the voltage applied to the load resistor accordingly. When temperature or power supply variations cause characteristic changes in the photodiode or transimpedance amplifier, the feedback system detects the resulting detection accuracy degradation and compensates by adjusting the voltage to restore proper detection sensitivity.
3Measurement precision
If detection sensitivity is increased to prevent noise detection, then false noise detection is reduced, but detection delays may occur
Solution Approach 1:
The patent makes the detection sensitivity dynamic rather than fixed. The control unit can adjust the voltage applied to the load resistor in real-time based on the detection conditions. This allows the system to optimize the balance between noise discrimination and detection speed by dynamically tuning the sensitivity parameter, preventing both false noise detection and detection delays.
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 approach allows for precise adjustment of detection sensitivity, preventing false noise detection and ensuring timely signal detection, even under varying conditions, with improved linearity and reduced chattering, thus enhancing the accuracy and reliability of optical signal detection.
Implementation Method 1
a photodiode PD photoelectrically converts an optical signal Pin formed from a pulse train into a photocurrent signal Iin
Data Source
AI summary
An optical signal detection circuit (10) includes an amplification circuit (11) that differentially amplifies an electrical signal (Tout) corresponding to the pulse train of an optical signal (Pin) and outputs a differential output signal (Aout), and a comparator (12) that compares the voltage value of the positive-phase signal of the differential output signal (Aout) with the voltage value of the negative-phase signal and outputs a pulsed comparison output signal (Cout) corresponding to the comparison result. The amplification circuit (11) includes a current addition circuit (11E) that adjusts a DC load current to generate a positive-phase signal (Aout+) and a negative-phase signal (Aout−) of the differential output signal (Aout) in accordance with an adjusted voltage value from an external adjusted voltage source (Vadj) and adjusts the DC bias of the positive-phase signal (Aout+) and the DC bias of the negative-phase signal (Aout−).