Actively-Controlled Thyristor Trigger Circuit for Overstress Protection
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Solution Overview
Problem
Electronic systems face challenges in protecting integrated circuits from transient overstress events such as electrical overstress and electrostatic discharge, which can cause overvoltage conditions and high power dissipation, leading to damage or destruction of ICs, particularly in devices with low breakdown voltages like advanced CMOS and BiCMOS technologies.
Innovation Solution
An actively-controlled thyristor protection circuit is implemented, comprising a silicon controlled rectifier (SCR) connected between a signal node and a discharge node, with an overvoltage sense circuit and an active trigger and latch release circuit that detects transient overstress events and controls the SCR's activation voltage using trigger signals, enabling fast activation and low static power dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional SCR protection circuit is used, then the circuit can provide overvoltage protection, but the SCR triggers at high voltage thresholds causing excessive voltage overshoot that damages low breakdown voltage devices
Solution Approach 1:
The patent changes the triggering parameter of the SCR from a high voltage threshold to a low voltage threshold using an active pull-down circuit that applies a negative voltage to the gate, enabling the SCR to trigger at much lower overvoltage levels and reduce voltage overshoot
Solution Approach 2:
The patent applies preliminary action by pre-charging a capacitor through a resistor before the overvoltage event, and using an active circuit to rapidly discharge the capacitor through the SCR gate when overvoltage is detected, enabling fast triggering response
2Object-affected harmful factors
If the SCR activation voltage is reduced to protect low breakdown voltage devices, then voltage overshoot is reduced, but the SCR may trigger inadvertently at normal operating voltages
Solution Approach 1:
The patent uses feedback by monitoring the gate voltage of the SCR and using an operational amplifier to detect when the voltage exceeds a reference threshold, enabling precise control of the triggering condition and preventing false activation at normal operating voltages
Solution Approach 2:
The patent introduces an intermediary operational amplifier circuit between the overvoltage condition and the SCR gate, which acts as a mediator to precisely control when the SCR triggers based on a reference voltage threshold, preventing inadvertent activation
3Speed
If a fast-acting protection circuit is implemented, then the turn-on speed is improved, but the circuit complexity increases
Solution Approach 1:
The patent merges multiple functions into a single operational amplifier circuit that performs both the detection of overvoltage conditions and the generation of the trigger signal, reducing overall circuit complexity while maintaining fast response time
Solution Approach 2:
The operational amplifier serves multiple functions: it acts as a voltage detector, a comparator against reference voltage, and a trigger signal generator, consolidating what would otherwise require separate circuits into a single multi-functional component
Data Source
AI summary
Apparatus and methods for actively-controlled trigger and latch release thyristor are provided. In certain configurations, an actively-controlled protection circuit includes an overvoltage sense circuit, a thyristor or silicon controlled rectifier (SCR) that is electrically connected between a signal node and a discharge node, and an active trigger and latch release circuit. The overvoltage sense circuit controls a voltage of a dummy supply node based on a voltage of the signal node, and the active trigger and latch release circuit detects presence of a transient overstress event at the signal node based on the voltage of the dummy supply node. The active trigger and latch release circuit provides one or more trigger signals to the SCR to control the SCR's activation voltage, and the active trigger and latch release circuit activates or deactivates the one or more trigger signals based on whether or not the transient overstress event is detected.