Transistor Gate Protection Circuit Using NTC Diodes for Short Circuits
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Solution Overview
Problem
Silicon carbide transistor devices are more susceptible to short circuit events due to their smaller size and higher current density, leading to a lower short circuit withstand time compared to silicon devices, necessitating improved protection mechanisms.
Innovation Solution
Incorporation of a short circuit protection circuitry with negative temperature coefficient diodes between the control and current terminals, which reduces voltage drop during a short circuit event, effectively shutting off the transistor to prevent failure, while maintaining minimal area usage on the die.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicon carbide transistor devices are used to achieve higher blocking voltage and lower on-state resistance, then device performance is improved, but short circuit withstand time is reduced
Solution Approach 1:
The patent implements preliminary protective action by incorporating a protection circuit that activates before catastrophic failure occurs. The circuit includes a first protection device (clamp) that activates at a first voltage threshold and a second protection device (resistor) that activates at a second voltage threshold, creating staged protection that intervenes before the transistor can be damaged by short circuit conditions.
Solution Approach 2:
The patent applies beforehand cushioning by placing protective devices in parallel with the transistor that absorb and dissipate energy before it can damage the transistor. The first protection device clamps voltage at a safe level, and the second protection device provides additional cushioning through resistance, preventing voltage spikes from reaching destructive levels during short circuit events.
2Reliability
If protection circuitry is added to extend short circuit withstand time, then reliability during short circuit is improved, but device complexity increases
Solution Approach 1:
The patent employs protection devices that are designed to be simple, passive components rather than complex active circuits. The first protection device uses a clamp structure with relatively low breakdown voltage, and the second uses a resistor with relatively high resistance value. These simple, disposable-like protective elements provide robust protection without requiring complex control logic or additional circuitry.
Solution Approach 2:
The patent achieves protection through parameter selection rather than circuit complexity. By choosing specific voltage thresholds for the first protection device and specific resistance values for the second protection device, the patent creates effective short circuit protection using simple components. The protection is achieved by changing the electrical parameters of parallel-connected devices rather than adding complex control circuits.
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
Significantly extends the short circuit withstand time of silicon carbide transistor semiconductor dies, potentially indefinitely, while also providing protection against electrostatic discharge and voltage overshoot, with minimal impact on active area and maintaining operational reliability.
Implementation Method 1
Incorporation of a short circuit protection circuitry with negative temperature coefficient diodes between the control and current terminals, which reduces voltage drop during a short circuit event
Implementation Method 2
providing protection against electrostatic discharge and voltage overshoot
Implementation Method 3
The voltage clamp generally contains one or more parallel branches connected between the source and gate terminals of the MOSFET. Each branch contains at least one diode and in many cases a series of diodes that, depending on the clamping voltage desired, are connected so that they either break down or conduct in a forward direction when the gate-to-source voltage reaches a selected level
Data Source
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AI summary
A transistor semiconductor die includes a first current terminal, a second current terminal, and a control terminal. A semiconductor structure is between the first current terminal, the second current terminal, and the control terminal and configured such that a resistance between the first current terminal and the second current terminal is based on a control signal provided at the control terminal. Short circuit protection circuitry is coupled between the control terminal and the second current terminal. In a normal mode of operation, the short circuit protection circuitry is configured to provide a voltage drop that is greater than a voltage of the control signal. In a short circuit protection mode of operation, the short circuit protection circuitry is configured to provide a voltage drop that is less than a voltage of the control signal.