Pixel Substrate Protection Circuit for Radiation-Induced Voltage
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Solution Overview
Problem
Conventional pixel substrates face reliability issues and integration challenges due to voltage fluctuations when powered off and exposed to radiation, which can damage circuit elements and complicate adaptation with logic substrates.
Innovation Solution
A protection circuit is implemented on the pixel substrate that short-circuits the supply line and substrate region when the voltage falls below a negative threshold, limiting quiescent voltage and preventing damage to circuit elements, and is self-powered through a photodiode element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the pixel substrate is powered off and exposed to radiation, then photoelectric conversion occurs generating electric potential differences, but voltage fluctuations damage circuit elements and reduce reliability
Solution Approach 1:
The patent converts the harmful effect of radiation-induced voltage fluctuations into a beneficial protective mechanism. The protection circuit uses the generated electric potential difference to activate the photodiode element, which in turn triggers the switching element to short-circuit the supply line and substrate region, thereby limiting the harmful quiescent voltage to a safe level. This transforms the harmful radiation effect into the activation signal for the protection mechanism.
Solution Approach 2:
The patent introduces a protection circuit as an intermediary between the photoelectric conversion element and the external circuitry. This protection circuit, comprising the switching element and photodiode element, mediates the voltage fluctuations by detecting them through the photodiode and actively limiting the quiescent voltage through the switching element's short-circuiting action, thus protecting the circuit elements from damage.
2Reliability
If a protection circuit is added to limit voltage, then reliability improves, but device complexity increases
Solution Approach 1:
The patent merges the protection function with the existing pixel substrate structure by integrating the protection circuit directly into the substrate. The switching element and photodiode element are combined into a unified protection mechanism that works together with the photoelectric conversion element, rather than adding a separate standalone protection device. This integration minimizes the increase in device complexity while achieving the reliability improvement.
Solution Approach 2:
The protection circuit is designed to be self-activating and self-regulating. The photodiode element automatically detects the voltage fluctuations caused by radiation exposure and triggers the switching element to activate the protection mechanism without requiring external control signals or additional complexity. The circuit serves itself by using the harmful voltage fluctuation as the activation signal for its own protection function.
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 protection circuit effectively limits quiescent voltage, enhancing the reliability of pixel substrates and simplifying integration with logic substrates by preventing voltage-induced damage and ensuring safe operation during radiation exposure.
Implementation Method 1
A photoelectric conversion element converts electromagnetic radiation impinging onto a detection area into an electronic sensor signal, e.g. a photocurrent
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A pixel substrate (100) includes a photoelectric conversion element (PD). The photoelectric conversion element (PD) includes a doped region (111) and a substrate region (112). The doped region (111) and the substrate region (112) form a pn junction (115). A pixel circuit (120) is electrically connected to a first supply line (101) and the photoelectric conversion element (PD). A protection circuit (130) is configured to short-circuit the first supply line (101) and the substrate region (112) when a voltage difference between the first supply line (101) and the substrate region (112) falls below a negative threshold voltage.