Light Sensor Circuit Dark Current Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Light sensor circuits face challenges due to junction capacitance and dark current issues in photodiodes, which affect the linearity and accuracy of sensor measurements, particularly when using analog-to-digital converters.
Innovation Solution
A light sensor circuit design that incorporates a capacitor unit to maintain the cathode of the photodiode at a voltage similar to the anode, effectively reducing visible junction capacitance and dark current impact, utilizing simple circuit structures with capacitive and switch components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a voltage follower is used to control the bias voltage at both ends of the photodiode, then the junction capacitance can be reduced, but the circuit complexity increases due to additional operational amplifier requirements
Solution Approach 1:
The patent extracts the essential function of voltage control from the complex voltage follower circuit and implements it using a simplified capacitor-based voltage holding mechanism. The capacitor unit holds the cathode voltage at a reference level without requiring an operational amplifier, thereby achieving junction capacitance reduction while eliminating the complexity of the voltage follower circuit.
Solution Approach 2:
The patent replaces the expensive and complex operational amplifier-based voltage follower with a simple, low-cost capacitor and switch combination. This substitution achieves the same voltage control function with minimal components, significantly reducing circuit complexity and manufacturing cost.
2Productivity
If the integrator operates at a reference voltage VCM, then the analog-to-digital conversion can be performed, but the design difficulty increases due to additional voltage control requirements
Solution Approach 1:
The patent merges the voltage holding function with the integration process by using the same capacitor unit to maintain the cathode voltage at the reference level during integration. This consolidation eliminates the need for separate voltage control circuits, reducing design complexity while maintaining ADC functionality.
3Measurement precision
If dark current calibration is performed in advance, then the linearity of the sensor can be improved, but the manufacturing process becomes more complex
Solution Approach 1:
The patent performs dark current calibration in advance during the manufacturing process by temporarily connecting the cathode to the anode through the switch element. This preliminary calibration establishes the baseline dark current value, which is then stored and used during normal operation, achieving high linearity without adding complexity to the final product.
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 enhances the performance and accuracy of analog-to-digital converters by minimizing dark current influence and simplifying circuit design and manufacturing costs.
Implementation Method 1
the signal of a light sensor circuit 9 is generated by a photocurrent produced by a photodiode 90
Implementation Method 2
By controlling the capacitor unit to maintain the cathode of the photodiode at a voltage level similar to or close to that of the anode, the visible junction capacitance of the photodiode can be effectively reduced
Data Source
AI summary
The present application discloses a light sensor circuit, which comprises a photodiode and a capacitor unit. The cathode of the photodiode is controlled by a capacitive unit to maintain the same or close voltage level as the anode of the photodiode, which significantly reduces the effect of the dark current of the photodiode. Thus, the light sensor circuit can effectively maintain the performance and accuracy of an analog-to-digital converter applying the light sensor circuit. The circuit design difficulty and manufacturing cost are also significantly reduced.