LCD Driver Output Circuit for EMI-Resistant ESD Protection
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Solution Overview
Problem
Conventional LCD driver circuits are susceptible to electromagnetic interference (EMI), which alters the voltage output and affects the intensity levels of displayed pixels, as the ESD protection circuits can clamp voltages outside the intended range, leading to unintended pixel intensity due to the interference.
Innovation Solution
A semiconductor integrated circuit with a voltage attenuating element connected to the internal signal line to reduce voltage swings caused by EMI, and a voltage limiting circuit to protect against electrostatic damage without altering the average output voltage, ensuring the voltage remains within a predetermined range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ESD protection circuits are used to protect against electrostatic discharge, then reliability is improved, but the circuits become susceptible to electromagnetic interference that alters output voltage
Solution Approach 1:
A clamp circuit is introduced as an intermediary component between the ESD protection circuit and the output terminal. This clamp circuit captures and suppresses voltage spikes caused by electromagnetic interference before they reach the output, thereby maintaining the protective function while reducing susceptibility to EMI
Solution Approach 2:
The invention modifies the voltage clamping characteristics by introducing a clamp circuit with specific threshold levels. The clamp circuit activates only when voltage exceeds predetermined thresholds, changing the operational parameters of the protection system to differentiate between ESD events and EMI-induced voltage fluctuations
2Reliability
If voltage clamping is applied to limit voltage range, then protection against overvoltage is improved, but average output voltage is altered causing unintended pixel intensity
Solution Approach 1:
The clamp circuit is designed to activate only partially - specifically when voltage exceeds predetermined thresholds due to EMI. It does not continuously clamp the voltage, allowing the average output voltage to remain accurate while providing protection during transient interference events
Solution Approach 2:
The clamp circuit operates with feedback mechanisms that monitor voltage levels and activate clamping only when necessary. This feedback control ensures that normal output voltages are not altered, maintaining pixel intensity accuracy while providing protection against voltage excursions caused by EMI
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 attenuates voltage swings caused by EMI, maintaining the intended average voltage output and preventing damage from electrostatic interference, thus stabilizing the displayed image even in the presence of electromagnetic interference.
Implementation Method 1
A semiconductor integrated circuit with a voltage attenuating element connected to the internal signal line to reduce voltage swings caused by EMI
Implementation Method 2
a voltage limiting circuit to protect against electrostatic damage without altering the average output voltage, ensuring the voltage remains within a predetermined range
Data Source
AI summary
A semiconductor integrated circuit has an output terminal connected to an external load, an internal signal line by which the output terminal is connected to an internal node, and a voltage generator that outputs a voltage to the internal node, for output through the internal signal line and the output terminal to the external load. A voltage attenuating element is connected to the internal signal line to attenuate voltage swings on the internal signal line. A limiting circuit is connected to the internal node to limit the voltage at the internal node to a predetermined range. Moderate voltage swings caused by external electromagnetic interference are kept within the predetermined range by the voltage attenuating element, so that the limiting circuit does not operate and the average output voltage is not changed.