Transistor Switch Gate Clamp Circuit for Load-Independent Overvoltage
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Solution Overview
Problem
Existing eFuse circuits for transistor switches, such as NMOS and PMOS FETs, face challenges in providing overvoltage protection that is independent of load impedance, load current, and load capacitance, leading to voltage clamping that is often dependent on these factors, which can result in instability and potential damage to electronic loads.
Innovation Solution
An electronic circuit with an overvoltage comparator and switch configuration that regulates the gate voltage of the transistor switch, including a fast discharge circuit and undershoot protection, allows for independent overvoltage protection that is not dependent on load conditions, using Schmitt-trigger comparators and a charge pump to manage voltage clamping effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional eFuse circuits are used for overvoltage protection, then the circuit can provide basic voltage clamping, but the clamping voltage becomes dependent on load impedance, load current, and load capacitance, leading to instability
Solution Approach 1:
The patent introduces an intermediary voltage regulator circuit between the switch and the load that actively regulates the clamp voltage independently of load conditions. This regulator acts as a mediator that decouples the voltage clamping function from load-dependent parameters, ensuring stable clamping voltage regardless of variations in load impedance, current, or capacitance.
Solution Approach 2:
The patent implements feedback control through a comparator that continuously monitors the source voltage and compares it against a reference voltage. When overvoltage is detected, the comparator triggers the voltage regulator to adjust the gate voltage, creating a closed-loop feedback system that maintains stable voltage clamping independent of load variations.
2Reliability
If the eFuse circuit is isolated from load conditions for stable clamping, then voltage protection becomes reliable, but the circuit complexity increases due to additional regulation components
Solution Approach 1:
The voltage regulator circuit performs multiple functions: it regulates the gate voltage to achieve independent voltage clamping, provides fast discharge capability through integrated switches, and incorporates undershoot protection mechanisms. By combining these functions into a single multi-functional block, the patent reduces overall circuit complexity while maintaining reliable load-independent voltage protection.
3Speed
If fast discharge circuit is activated for overvoltage protection, then the response time to clamp voltage is reduced, but current consumption increases during protection events
Solution Approach 1:
The fast discharge circuit operates periodically rather than continuously - it remains inactive during normal operation and only activates when overvoltage conditions are detected by the comparator. This periodic activation allows the circuit to achieve fast response speed during protection events while maintaining low current consumption during normal operation, as the discharge switches are only closed temporarily when needed.
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 enables robust overvoltage protection that clamps output voltage to a fixed level, auto-corrects for process, current, and temperature variations, and ensures low current consumption during normal operation, effectively isolating the eFuse circuit from load impedance and capacitance when no overvoltage is detected.
Implementation Method 1
an overvoltage comparator configured to detect an overvoltage on a source voltage of the transistor switch by comparing the source voltage to a reference voltage
Implementation Method 2
a voltage regulator configured to regulate a clamp voltage when the switch is switched on. The clamp voltage may regulate a gate voltage on a gate of the transistor switch
Implementation Method 3
a charge pump can be used to provide the required gate voltage for the FET to turn 'on' and allow current to flow through it
Implementation Method 4
When a voltage is applied to the gate terminal, it creates an electric field that forms a conducting channel between the drain and source regions
Implementation Method 5
The channel allows current to flow from the drain to the source. The amount of current that flows through the channel is controlled by the voltage applied to the gate terminal
Implementation Method 6
The gate terminal controls the conduction of current through the channel. It is electrically insulated from the channel by a thin layer of oxide, typically made of silicon dioxide (SiO2)
Data Source
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AI summary
An electronic circuit for overvoltage protection of a transistor switch, including: an overvoltage comparator configured to detect an overvoltage on a Vsource of the transistor switch by comparing the Vsource to a Vref and output an on signal when overvoltage is detected; a switch configured to switch on by the on signal; a voltage regulator configured to regulate a Vclamp when the switch is switched on, wherein the Vclamp regulates Vgate of the transistor switch; and a further comparator configured to detect a Vcc of the transistor switch and output an off signal when Vcc is below a threshold voltage, wherein the switch is configured to switch off by the off signal, and wherein the voltage regulator and the further comparator switch off when the switch is switched off.