Thermal Protection for Integrated Power MOSFET
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Solution Overview
Problem
Existing thermal protection devices for power MOS transistors are either overprotective, limiting functionality, or fail to accurately sense the temperature due to the distance and parasitic activations of external temperature sensors, leading to potential overheating failures.
Innovation Solution
A thermal protection device that integrates a temperature sensor within the power MOS structure, using interdigitated source regions to sense temperature and generate an over-temperature flag signal, minimizing distance and structural differences with the power transistor, and optionally using a second sensor to compensate for temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a temperature sensor is integrated on the chip at a distance from the power MOS, then the protection device can be implemented, but the sensor cannot sense exactly the real working temperature of the MOS transistor
Solution Approach 1:
The temperature sensor is merged with the power MOS transistor structure by using a subset of the interdigitated source regions as the sensing element. This integration ensures the sensor is located at the exact position where temperature measurement is needed, eliminating the distance problem and achieving accurate real-time temperature monitoring of the power MOS.
2Reliability
If a bipolar transistor is used as temperature sensor, then temperature monitoring can be implemented, but parasitic activations caused by below ground voltages are likely to occur
Solution Approach 1:
The invention extracts the temperature sensing function from the conventional bipolar transistor implementation and integrates it directly into the power MOS structure using interdigitated source regions. This extraction eliminates the parasitic activation problem because the sensing structure is now part of the power MOS itself and is not susceptible to the same voltage-induced parasitic effects that plague separate bipolar sensor implementations.
3Measurement precision
If the temperature sensor is integrated inside the power MOS structure, then precise temperature monitoring is achieved, but the device complexity increases
Solution Approach 1:
The interdigitated source regions of the power MOS transistor serve dual functions: they are both essential components of the power MOS operation and the temperature sensing element. This multi-functionality approach achieves precise temperature monitoring without adding separate dedicated sensing structures, thereby minimizing the increase in device complexity while maximizing measurement precision.
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
Provides precise temperature monitoring and reduced parasitic activations, enabling accurate detection of overheating conditions and preventing damage while maintaining operational efficiency.
Implementation Method 1
the voltage of these separately connected source regions through which a certain current is forced will depend on their temperature
Implementation Method 2
a comparator, integrated on the substrate outside the well region, comparing the source voltage present on the small number of separately connected source regions with a threshold voltage
Data Source
AI summary
A thermal protection device is for an integrated power MOSFET transistor including an interdigitated array of source regions and drain regions defined in a well region of the monocrystalline silicon substrate, and gate structures overhanging channel regions defined between adjacent source and drain regions. The thermal protection device may include a temperature sensor and a comparator for generating an over temperature flag signal usable for turning off the overheated power transistor. The thermal protection device may sense, in a very accurate manner, the temperature of the power MOS and may include a circuit for forcing a fixed current through a small number of source regions of the interdigitated array separately connected from the other source regions electrically connected in common of the power transistor; and a comparator, integrated on the substrate outside the well region, comparing the source voltage present on the small number of separately connected source regions with a threshold voltage for producing on an output the over temperature flag signal.