Electrostatic Protection Circuit With Overcurrent Control
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Solution Overview
Problem
Existing electrostatic discharge (ESD) protection circuits, such as RC triggered MOS circuits, risk damaging shunt transistors due to prolonged high currents during ESD events, as they rely on time constants that may not adequately protect against overcurrent conditions.
Innovation Solution
An electrostatic protection circuit with a trigger circuit, shunt element, overcurrent detection circuit, and switch circuit that turns off the shunt element when current exceeds a predetermined threshold, preventing overheating and damage, utilizing a combination of MOS transistors and resistors to manage ESD surges effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a large time constant is used in the trigger circuit to allow complete discharge of ESD surge, then the ESD protection is improved, but the shunt transistor may overheat and be damaged due to prolonged high current
Solution Approach 1:
The patent applies dynamics by making the shunt transistor's on-time adjustable and controllable. Instead of using a fixed large time constant that causes prolonged current flow, the circuit dynamically adjusts the discharge duration based on real-time current monitoring. The control circuit receives feedback about the discharge status and terminates the shunt transistor operation when the ESD surge is sufficiently discharged, preventing overheating while maintaining effective protection.
Solution Approach 2:
The patent implements feedback through a control circuit that monitors the discharge current and provides feedback signals to control the shunt transistor's operation. The feedback mechanism detects when the ESD surge has been adequately discharged and automatically turns off the shunt transistor, creating a closed-loop control system that balances complete discharge with prevention of overheating.
2Duration of action of moving object
If the shunt transistor remains on for a long time to fully discharge ESD surge, then the discharge completeness is improved, but the risk of shunt transistor damage increases
Solution Approach 1:
The patent makes the shunt transistor's operational duration dynamic rather than static. The control circuit continuously monitors discharge progress and adjusts the shunt transistor's on-time accordingly, extending it enough to achieve complete ESD discharge but terminating it before damage occurs, thus dynamically optimizing both discharge completeness and device reliability.
Solution Approach 2:
The patent applies preliminary action by establishing a control mechanism that is ready to terminate the shunt transistor operation at the optimal moment. The control circuit is pre-configured with threshold values and control logic that will automatically stop the discharge process when safety conditions are met, preventing damage before it occurs rather than reacting after damage has started.
3Device complexity
If a simple RC triggered MOS circuit is used, then the device complexity is reduced, but the ability to prevent overcurrent damage is insufficient
Solution Approach 1:
The patent adds feedback functionality to the simple RC triggered MOS circuit by incorporating a control circuit that monitors discharge current and provides feedback control signals. This feedback mechanism enables the circuit to detect overcurrent conditions and automatically adjust or terminate shunt transistor operation, significantly improving overcurrent protection capability while adding only moderate complexity.
Solution Approach 2:
The patent introduces an intermediary control circuit that mediates between the simple RC trigger and the shunt transistor. This intermediary layer processes the trigger signal, monitors discharge conditions, and controls the shunt transistor's operation, thereby enhancing protection capability without directly complicating the core RC trigger mechanism.
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 ensures complete discharge of ESD surges while protecting shunt elements from damage by controlling the shunt circuit to prevent overcurrent conditions, aligning with ESD protection standards like the Human Body Model, thereby enhancing the reliability and longevity of semiconductor devices.
Implementation Method 1
ESD means a discharge from an electrically charged body or machine to a semiconductor device and a discharge from an electrically charged semiconductor device to the ground potential
Implementation Method 2
a serial circuit including a resistor and a capacitor serially connected between power terminals
Implementation Method 3
the on time of the shunt transistor is determined by a time constant of the trigger circuit
Implementation Method 4
a large amount of electric charge from the terminal flows into the semiconductor device as a current
Implementation Method 5
when a large current keeps flowing through the shunt transistor for a long time, there is concern that the shunt transistor itself may overheat and be damaged
Data Source
AI summary
An electrostatic protection circuit includes a trigger circuit that is connected between a first power line and a second power line. The trigger circuit is configured to output a trigger signal in response to a voltage fluctuation between the first and second power lines. A shunt element has a main current path between the first power line and the second power line and is controllable to be on and off using the trigger signal. A control circuit is configured to supply a control signal to turn off the shunt element when a current value of the main current path of the shunt element exceeds a predetermined threshold value.