MOSFET Body Diode Forward Voltage for Temperature-Aware Short Circuit Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing methods for detecting short circuits in MOSFETs are inadequate due to the temperature dependence of on-state resistance, leading to potential misclassification of cold MOSFETs carrying high currents as normal operating currents, which can result in device failure, and require additional complex and costly temperature sensing solutions.
Innovation Solution
A circuit arrangement that measures the forward voltage of a body diode in field effect transistors to determine temperature, using a predefined current and known voltage-current characteristics, allowing for direct and efficient temperature measurement without additional electronic elements or complex adaptations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If additional temperature sensors are added to determine MOSFET temperature, then accurate temperature measurement is achieved, but device complexity and cost increase
Solution Approach 1:
The patent makes the body diode serve dual purposes: its inherent function as a freewheeling diode and as a temperature sensor. By measuring the forward voltage of this existing component, the system obtains temperature information without adding separate sensing elements, thereby reducing device complexity while maintaining measurement precision.
Solution Approach 2:
The body diode is utilized for multiple functions: current freewheeling during MOSFET off-state and temperature sensing through forward voltage measurement. This multi-functionality eliminates the need for dedicated temperature sensors, reducing overall circuit complexity while achieving accurate temperature-dependent short circuit detection.
2Loss of energy
If MOSFETs with lower on-state resistance are used, then power losses are reduced, but temperature-dependent detection issues are worsened
Solution Approach 1:
Instead of detecting short circuits through the MOSFET's on-state voltage (which decreases with temperature and creates detection issues), the patent inverts the approach by using the body diode's forward voltage, which increases with temperature. This inversion provides a detection signal that becomes more prominent under cold conditions, compensating for the lower on-state resistance of modern low-loss MOSFETs.
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
This approach effectively closes the 'protection gap' in short circuit detection by accurately distinguishing between cold and hot MOSFETs, enhancing detection reliability and reducing the risk of device failure, while eliminating the need for expensive special transistors and complex circuitry.
Implementation Method 1
measuring a forward voltage of a body diode of any one of the at least two field effect transistors resulting from a predefined current flowing through the field effect transistor
Data Source
AI summary
According to various embodiments, a circuit arrangement is provided which includes a bridge circuit having at least two field effect transistors and a measurement circuit configured to measure a forward voltage of a body diode of any one of the at least two field effect transistors resulting from a current flowing through the field effect transistor.