Temperature Sensor ESD Circuit for Surge Protection and Fault Detection
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Solution Overview
Problem
Existing electro-optical devices face issues with temperature detection due to failures in the electrostatic protection circuit, particularly when electrical breakdown occurs in capacitance elements at the cathode side, leading to undetected short-circuited currents and compromised protection functions.
Innovation Solution
The electrostatic protection circuit includes a transistor connected in parallel with a temperature detecting element, featuring a first capacitance element with a dielectric layer thicker than the gate insulating film and a resistance element connected to the gate electrode, ensuring adequate protection against surge currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resistance element is connected between the gate electrode and cathode wiring line to protect against surge currents, then the protection function is improved, but when electrical breakdown occurs in the capacitance element at the cathode side, the short-circuited current cannot be detected and the protection function fails
Solution Approach 1:
The patent divides the electrostatic protection circuit into distinct functional segments: the first capacitance element (C1) handles surge current from the anode side, the second capacitance element (C2) handles surge current from the cathode side, and the resistance element (R3) provides detection capability. This segmentation allows each component to specialize in specific protection scenarios, enabling both protection functions to coexist without interfering with current detection.
Solution Approach 2:
The patent introduces an intermediary node (the gate electrode of the transistor) that serves as a common connection point for both capacitance elements and the resistance element. This intermediary structure allows the circuit to detect short-circuited currents while maintaining electrostatic protection, as the gate electrode potential changes can be monitored to detect failures without compromising the protection function.
2Reliability
If two capacitance elements are connected in series between anode and cathode wiring lines with the gate electrode connected to their connecting node, then electrostatic protection is improved, but inspection of failures in capacitance elements becomes difficult
Solution Approach 1:
The patent implements a feedback mechanism where the resistance element (R3) connected to the gate electrode provides continuous monitoring of the circuit state. When a capacitance element fails, the feedback through the resistance element causes a detectable change in the gate electrode potential or current flow, enabling automatic or assisted detection of failures without requiring complex external inspection equipment.
3Reliability
If the electrostatic protection circuit is designed with capacitance elements and resistance elements to protect the temperature detecting element, then protection against surge currents is improved, but the circuit complexity increases
Solution Approach 1:
The patent designs the electrostatic protection circuit with multi-functional components: the transistor serves both as a protection element and a detection node, the capacitance elements provide both surge protection and failure indication, and the resistance element provides both current limiting and feedback functionality. This multi-functionality reduces the need for additional dedicated components, thereby limiting the increase in circuit complexity while maintaining comprehensive protection.
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 effectively protects the temperature detecting element from surge currents, enabling accurate temperature detection and maintaining the electrostatic protection function, even in the presence of electrical breakdowns.
Implementation Method 1
a first capacitance element (C1), the electrostatic capacity of which is greater than an electrostatic capacity between the gate electrode (33t) and the semiconductor layer (31t)
Implementation Method 2
a first dielectric layer (40a) provided between the first capacitance electrode (4e) and the second capacitance electrode (5e1)
Implementation Method 3
a resistance element (R3) having one end electrically connected to the gate electrode (33t) and the first capacitance electrode (4e) and the resistance element (R3) having another end electrically connected to a source-drain region (31i) on one side of the semiconductor layer (31t) and the second capacitance electrode (5e1)
Data Source
AI summary
An electro-optical device includes a temperature detecting element and an electrostatic protection circuit configured to protect the temperature detecting element from a surge current. The electrostatic protection circuit includes a transistor electrically connected to the temperature detecting element in parallel, a first capacitance element electrically connected to the transistor, and a resistance element electrically connected to the first capacitance element in parallel. The electrostatic capacity of the first capacitance element is greater than a gate capacity between a gate electrode and a semiconductor layer that constitutes the transistor. In addition, a dielectric layer of the first capacitance element is thicker than a gate insulating film of the transistor.