Method of operating a power transistor formed by a plurality of transistor cells electrically connected in parallel
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Solution Overview
Problem
Power transistors, particularly SiC MOSFETs, face challenges in short-circuit and overcurrent protection due to high instantaneous power density and rapid temperature rise, leading to overheating and reliability issues, as existing heat dissipation mechanisms and gate drive designs struggle to respond quickly enough to prevent device destruction.
Innovation Solution
Incorporating a ferroelectric insulator in the gate dielectric stack of power transistors, which undergoes a phase transition above the Curie temperature, increasing the threshold voltage and reducing drain current to limit overcurrent conditions, and using a driver control circuit to set the ferroelectric insulator into a defined polarization state for enhanced protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive heat dissipation mechanisms are used, then overheating is avoided, but the response time is too slow to prevent device destruction during short circuit conditions
Solution Approach 1:
The ferroelectric insulator is pre-configured with specific polarization states that automatically activate protection mechanisms when temperature thresholds are reached, eliminating the need for slow external detection and response systems
Solution Approach 2:
The device uses its own thermal field to trigger the phase transition in the ferroelectric insulator, which automatically limits current without requiring external sensors or control circuits
2Reliability
If temperature sensors are embedded in the power transistor die, then operating temperature is detected for preventing high-temperature operation, but device complexity increases
Solution Approach 1:
The ferroelectric insulator inherently responds to temperature changes through phase transition, eliminating the need for separate temperature sensors and control circuits
Solution Approach 2:
The electrical properties of the ferroelectric insulator change with temperature, providing intrinsic temperature sensing and protection functionality without additional components
3Reliability
If integrated current sensors are used, then overcurrent condition is detected, but die area is significantly occupied
Solution Approach 1:
The ferroelectric insulator automatically responds to overcurrent conditions through thermal effects, eliminating the need for dedicated current sensing circuits and freeing up die area
Solution Approach 2:
The protection function is extracted from separate sensing circuits and integrated into the gate dielectric stack itself, removing the need for additional sensor components
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 ferroelectric-based gate dielectric stack effectively self-regulates drain current and improves short-circuit reliability by decoupling the trade-off between on-resistance and peak currents, ensuring safe operation and reducing heat generation during short-circuit events.
Implementation Method 1
a ferroelectric insulator in the gate dielectric stack, which undergoes a phase transition above the Curie temperature, increasing the threshold voltage and reducing drain current to limit overcurrent conditions
Data Source
AI summary
A power transistor is formed by a plurality of transistor cells electrically connected in parallel. Each transistor cell includes a gate structure including a gate electrode coupled to a control terminal and a gate dielectric stack, the gate dielectric stack including a ferroelectric insulator. A method of operating the power transistor includes: switching the power transistor in a normal operating mode by applying a switching control signal to the control terminal, the switching control signal having a maximum voltage and a minimum voltage; and setting the ferroelectric insulator into a defined polarization state by applying a first voltage pulse to the control terminal, the first voltage pulse exceeding the maximum voltage of the switching control signal.