Photodiode Light Receiver for Abrupt Light Change Detection
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Solution Overview
Problem
Existing light receiving circuits suffer from low sensitivity due to parasitic capacitance and require expensive low pass filters, leading to increased size and current consumption, while struggling to detect abrupt changes in light levels effectively across varying ambient conditions.
Innovation Solution
A light receiving circuit design that includes a photodiode, a reset circuit, a voltage detection circuit, and a voltage increase detection circuit, which uses a capacitor to control voltage levels and detect abrupt changes in light without a low pass filter, reducing current consumption and size while maintaining high sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a low pass filter is used to detect abrupt light changes, then detection accuracy is improved, but device complexity and size increase
Solution Approach 1:
The patent extracts and eliminates the low pass filter component from the circuit. Instead of using a low pass filter to detect abrupt light changes, the invention uses a photodiode directly connected to a transistor, simplifying the circuit while maintaining detection accuracy through the transistor's switching characteristics.
Solution Approach 2:
The patent replaces the mechanical/electronic filtering mechanism (low pass filter) with a semiconductor-based detection mechanism. The transistor's inherent switching behavior substitutes for the filtering function, eliminating the need for separate filtering components and reducing circuit complexity.
2Reliability
If a low pass filter is used to maintain light receiving sensitivity, then sensitivity is improved, but current consumption increases
Solution Approach 1:
The patent removes the low pass filter component that was consuming current, and instead relies on the photodiode-transistor combination to maintain light receiving sensitivity. The transistor's switching action preserves sensitivity without the continuous current consumption associated with active filtering components.
3Ease of manufacture
If parasitic capacitance is present at the photodiode node, then circuit integration is improved, but voltage increase rate decreases
Solution Approach 1:
The patent changes the circuit configuration parameters by directly connecting the photodiode to the transistor gate, eliminating intermediate nodes with parasitic capacitance. This parameter change maintains circuit integrability while significantly improving the voltage increase rate by reducing capacitive loading effects.
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 circuit achieves high sensitivity in detecting abrupt light changes with reduced current consumption and cost, and a smaller footprint, effectively addressing the limitations of existing designs by controlling voltage levels and eliminating the need for low pass filters.
Implementation Method 1
a photodiode 101... When the photodiode 101 is irradiated with light of an LED or the like, a current is generated in the photodiode 101
Data Source
AI summary
The light receiving circuit includes: a photoelectric conversion element for causing a current corresponding to an amount of incident light to flow to a node; a voltage detection circuit for outputting a detection signal when a voltage of the node becomes equal to or higher than a first voltage; a reset circuit for causing, when the detection signal of the voltage detection circuit is input, the current of the photoelectric conversion element to flow to a GND terminal so that the voltage of the node becomes a second voltage lower than the first voltage, and for holding this state when the detection signal is no longer input; and a voltage increase detection circuit for detecting a fluctuation in the voltage of the node and outputting a detection result.