Optical Receiver Circuit With Dynamic Threshold Shifting
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Solution Overview
Problem
Existing optical receiver circuits face challenges in reducing pulse width distortion due to high junction capacitance in photodiodes, leading to increased delay times and blunted waveforms, especially at high temperatures and over time, which affects the accuracy of signal conversion from optical to electrical signals.
Innovation Solution
The optical receiver circuit incorporates a level shift circuit and a controller that dynamically adjusts the reference voltage by generating a shift control signal to shift the voltage signal to a low-level side when it exceeds a certain threshold, and returns it to a high-level side after a prescribed period, using a second voltage source and a comparator to minimize pulse width distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a level shift circuit shifts the voltage to avoid saturation of the differential amplifier, then the output signal saturation is reduced, but the threshold changes between pulses and delay time varies
Solution Approach 1:
The patent implements dynamic threshold adjustment by switching between two reference voltages (Vth1 and Vth2) based on the input signal state. When the input voltage exceeds a predetermined level, the threshold is switched from Vth1 to Vth2, allowing the comparison threshold to adapt dynamically to signal conditions rather than remaining fixed or uniformly shifted
Solution Approach 2:
The patent divides the single threshold function into two distinct reference voltages (Vth1 and Vth2) that are selectively applied. The first reference voltage Vth1 is used for normal operation, while the second reference voltage Vth2 is used when the input signal exceeds a predetermined level, segmenting the threshold function into multiple operational modes
2Measurement precision
If the reference voltage is set to a high level to increase voltage comparison accuracy, then comparison precision is improved, but pulse width distortion increases due to PD junction capacitance
Solution Approach 1:
The patent changes the reference voltage parameter dynamically based on signal conditions. By switching between two different reference voltage levels (Vth1 and Vth2) depending on whether the input signal exceeds a predetermined level, the system adapts the comparison threshold to maintain both accuracy and minimize pulse width distortion under varying signal conditions
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 reduces pulse width distortion by stabilizing the comparator switching and minimizing the delay time, allowing for more accurate and efficient conversion of optical signals to electrical signals, even under varying conditions.
Implementation Method 1
a photocurrent detected by a PD (photodiode)
Data Source
AI summary
An optical receiver circuit and an optical coupling device, which includes: a light-receiving element; TIA operable to output a first voltage signal in response to input of the current signal; a voltage source operable to supply a second voltage signal serving as a reference voltage for determining pulse switching; a voltage source operable to supply a third voltage signal serving as a reference voltage for generating a shift control signal; a level shift circuit operable to output a voltage signal generated by subtracting a level shift voltage from the first voltage signal; a comparator operable to convert the first voltage signal to a pulse, and a controller operable to output the shift control signal outputting the first voltage signal shifted to a low-level side when the first voltage signal exceeds the third voltage signal, and outputting the first voltage signal without shifting after the output of the level shift circuit is lowered below the second voltage signal, are provided.