Capacitor Storage Circuit With Photosensitive Diode for Light Exposure
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Solution Overview
Problem
Storage devices based on capacitors, such as RFID and NFC transponders, are sensitive to light, which can significantly reduce their persistence time due to photocurrent generation, leading to rapid discharge and unreliable data retention.
Innovation Solution
Incorporating a photosensitive diode between the control circuit and the pass device, which reduces the input voltage and creates a layer of holes around the source, thereby reducing photocurrent and maintaining persistence time even when exposed to light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a capacitor-based storage device is used in RFID or NFC transponders, then data retention functionality is achieved, but persistence time is significantly reduced when exposed to light due to photocurrent generation
Solution Approach 1:
A photosensitive diode is introduced as an intermediary component between the control circuit and the pass device. This diode detects light exposure and generates a signal that triggers the control circuit to adjust the pass device's gate voltage, thereby compensating for the harmful photocurrent effect and maintaining data retention reliability under light exposure conditions.
Solution Approach 2:
The invention dynamically changes the gate voltage parameter of the pass device based on light exposure conditions. When light is detected, the control circuit modifies the gate voltage to alter the pass device's conductivity, thereby compensating for photocurrent-induced charge leakage and extending persistence time while maintaining reliable data retention.
2Device complexity
If the storage device operates normally without light protection, then device complexity is low, but light exposure causes rapid capacitor discharge and data loss
Solution Approach 1:
The photosensitive diode serves as an intermediary that detects light exposure and triggers a control response. By adding this single sensing component and its associated control logic, the system gains light protection capability with minimal increase in overall complexity, effectively reducing light sensitivity without requiring complex shielding or multiple redundant components.
3Duration of action of stationary object
If the gate voltage of the pass device is reduced to counteract photocurrent, then persistence time is maintained, but the layer of holes created around the source may affect device operation
Solution Approach 1:
The photosensitive diode provides feedback about light exposure conditions to the control circuit. Based on this feedback, the control circuit adjusts the gate voltage to an optimal level that compensates for photocurrent effects without creating excessive hole accumulation. This closed-loop control ensures persistence time is maintained while preventing operational reliability issues from improper voltage levels.
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 solution effectively reduces the light sensitivity of the storage device, maintaining an acceptable persistence time and ensuring reliable data retention by minimizing the impact of light exposure on capacitor discharge.
Implementation Method 1
a photosensitive diode coupled between the control circuit and the pass device, such that an input voltage provided by the control circuit to the pass device is reduced if the storage device is exposed to light
Data Source
AI summary
In accordance with a first aspect of the present disclosure, a storage device is provided, comprising: a capacitor configured to be charged; a charge circuit configured to charge said capacitor; a pass device coupled between the charge circuit and the capacitor; a control circuit configured to control said pass device; a photosensitive diode coupled between the control circuit and the pass device, such that an input voltage provided by the control circuit to the pass device is reduced if the storage device is exposed to light. In accordance with a second aspect of the present disclosure, a corresponding method of producing a storage device is conceived.