Temperature-Compensated Desaturation Circuit for Stable MOSFET Tripping
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Solution Overview
Problem
Switching devices like MOSFETs experience changes in operating characteristics due to temperature increases from high current flows, affecting circuit characteristics such as thresholds and potentially leading to unintended tripping.
Innovation Solution
A desaturation circuit with temperature compensation is implemented, using a combination of proportional to absolute temperature (PTAT) and complementary to absolute temperature (CTAT) circuits to adjust the trip voltage threshold based on temperature changes, ensuring a constant tripping point at a specific current level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a constant trip voltage threshold is used in the desaturation circuit, then the circuit design is simple, but the tripping point varies with temperature causing unintended device shutdowns
Solution Approach 1:
The patent changes the parameter of the trip voltage threshold from a constant value to a temperature-dependent value. The desaturation circuit dynamically adjusts the trip voltage threshold based on temperature conditions, allowing the threshold to vary with temperature while maintaining a consistent tripping point in terms of current level. This resolves the contradiction by making the threshold parameter adaptive rather than fixed.
Solution Approach 2:
The patent implements a feedback mechanism where the desaturation circuit monitors temperature conditions and adjusts the trip voltage threshold accordingly. The circuit uses the temperature information to modify the threshold, creating a closed-loop system that maintains reliable operation across varying temperature conditions while preventing unintended shutdowns.
2Reliability
If the trip voltage threshold is adjusted to compensate for temperature changes, then the tripping point remains consistent, but the circuit complexity increases
Solution Approach 1:
The patent applies parameter changes by making the trip voltage threshold a function of temperature. The circuit dynamically adjusts this parameter based on operating conditions, ensuring that the power dissipation limit remains stable across temperature variations. This approach maintains reliability while using a systematic method to manage the increased complexity through parameter adaptation.
3Reliability
If a constant current level is maintained through temperature compensation, then power dissipation is properly limited, but the circuit requires additional temperature-dependent components
Solution Approach 1:
The patent uses parameter changes to maintain a constant current level by adjusting the trip voltage threshold according to temperature. The circuit modifies the voltage threshold parameter in response to temperature variations, ensuring that the current limit remains consistent. This approach achieves reliable power dissipation control while managing component complexity through systematic parameter adaptation.
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 temperature-compensated desaturation circuit maintains a consistent tripping point for the MOSFET at a constant current level, effectively managing power dissipation and preventing unintended device shutdowns due to temperature fluctuations.
Implementation Method 1
a proportional to absolute temperature (PTAT) circuit having a bandgap circuit, wherein the PTAT circuit has an output
Implementation Method 2
a complementary to absolute temperature (CTAT) circuit having an output
Implementation Method 3
a combiner circuit to combine the output of the CTAT circuit and the output of the PTAT circuit to generate the temperature-compensated voltage desaturation threshold voltage
Data Source
AI summary
Methods and apparatus for a desaturation circuit having a temperature compensated voltage threshold for protecting a power transistor, such as a FET. A comparator module has a first input compared to a voltage source associated with current through the FET and a second input coupled to the voltage threshold circuit. As a resistance of the FET changes due to temperature changes, the voltage threshold changes to compensate for the resistance change of the FET.