Active Device Array Substrate ESD Protection Circuit
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Solution Overview
Problem
Conventional TFT array substrates for LCDs face significant risks of damage from electrostatic discharge (ESD) due to the accumulation of electrostatic charges during manufacturing and assembly, leading to disabled ESD protection functions and potential damage to the substrate.
Innovation Solution
An active device array substrate is designed with scan lines, data lines, pixel units, ESD protection elements, a first short ring, and an ESD biased generator, where the ESD biased generator senses electrostatic voltage and provides a voltage level to turn on ESD protection elements to conduct charges to the short rings, neutralizing them at the lowest voltage level, thereby preventing damage to pixel units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the turned on voltage of the back-to-back diode is increased to reduce current leakage, then the effect to the TFT array substrate is reduced, but the pixel units are damaged by ESD charges when the substrate is subjected to ESD stress
Solution Approach 1:
The ESD protection element dynamically changes its electrical state based on the voltage level. During normal operation, it maintains a high-impedance state to minimize current leakage. When ESD stress occurs and voltage exceeds the threshold, it transitions to a low-impedance state to conduct ESD charges to the short ring, thus adapting to different operational conditions to resolve the contradiction between reducing leakage and maintaining protection capability
Solution Approach 2:
The invention changes the voltage parameter of the ESD protection element to control its conductivity. By applying a controlled voltage from the ESD biased generator, the protection element's turned-on voltage is dynamically adjusted. This allows the element to remain off during normal operation (reducing leakage) and turn on during ESD events (providing protection), resolving the contradiction through parameter control
2Reliability
If conventional back-to-back diodes are used for ESD protection, then ESD charges can be conducted to the short ring, but the ESD protection function is disabled after the substrate is completely fabricated and wiring circuits are cut off
Solution Approach 1:
The ESD biased generator is activated in advance before ESD stress occurs to establish the proper voltage state of the ESD protection element. This preliminary action ensures that the protection element is in the correct state to immediately respond to ESD events, maintaining protection functionality throughout the substrate's operational lifecycle, including after fabrication and wiring circuit cutoff
Solution Approach 2:
The ESD protection system is self-activating through voltage sensing. When ESD stress occurs, the resulting voltage change automatically triggers the ESD biased generator to adjust the protection element's state, enabling the system to serve itself without external control. This self-service mechanism ensures continuous protection duration from fabrication through operation
3Reliability
If the ESD protection element is always turned on to protect against ESD, then ESD charges can be conducted, but large current leakage occurs affecting operation signals between scan line and data line
Solution Approach 1:
The ESD protection element transitions from a static always-on state to a dynamic state that adapts to operational conditions. It remains in a high-impedance off-state during normal operation to minimize current leakage, and switches to a low-impedance on-state only when ESD stress is detected, thus dynamically balancing protection and energy loss
Solution Approach 2:
The system uses voltage sensing as feedback to control the ESD protection element's state. The ESD biased generator monitors the voltage across the protection element and adjusts its conductivity accordingly. This feedback mechanism ensures the element turns on only when necessary (during ESD events) and remains off during normal operation, eliminating unnecessary current leakage while maintaining 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
The solution effectively neutralizes electrostatic charges and maintains ESD protection functionality, preventing damage to the active device array substrate during ESD events and reducing energy consumption by adjusting voltage differences during normal operation.
Implementation Method 1
An ESD protection element 340 has a first connection terminal 342, a second connection terminal 344 and a third connection terminal 346, wherein the first connection terminal 342 is electrically connected to one of a corresponding scan line 320 and data line 330, the second connection terminal 344 is electrically connected to the short ring 350
Implementation Method 2
an ESD biased generator 360, wherein the third connection terminal 346 is electrically connected to the ESD biased generator 360
Data Source
AI summary
An active device array substrate includes pixel units, scan lines, data lines, electrostatic discharge (ESD) protection elements, a short ring and an ESD biased generator. Each pixel unit is electrically connected to the corresponding scan line and data line. Each ESD protection element has a first connection terminal, a second connection terminal and a third connection terminal, wherein the first connection terminal is electrically connected to one of the corresponding scan line and data line, the second connection terminal is electrically connected to the short ring, and the third connection terminal is electrically connected to the ESD biased generator. As an ESD stress occurs, the ESD biased generator provides a voltage to the ESD protection elements to turn on them. It causes that the accumulated electrostatic charges are conducted into the lowest potential of the substrate through the short rings, so as to prevent the pixel units from ESD damaging.