Reversible Current Limiting via Dynamic Body Bias
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional electronic fuses and e-fuses are irreversible, requiring reset operations to restore functionality after overcurrent events, limiting their ability to maintain proper operation during current fluctuations between maximum saturation current and protection values.
Innovation Solution
An electrical protection device comprising a power transistor, a sensing transistor with a body terminal, and a control stage that uses a body-driving stage to bias the sensing transistor, allowing for reversible current limitation and maintaining protection values without the need for reset operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional electronic fuses use power MOSFETs to limit maximum current, then protection function is achieved, but the power MOSFET enters saturation and requires reset operation to restore functionality
Solution Approach 1:
The invention makes the threshold voltage of the sensing transistor dynamic by coupling its body terminal to a voltage divider network connected to the drain of the power MOSFET. This allows the threshold voltage to automatically adjust based on the drain voltage, enabling the device to maintain protection functionality without requiring reset operations after saturation events.
Solution Approach 2:
The invention changes the electrical parameter (threshold voltage) of the sensing transistor dynamically through body effect modulation. By varying the body voltage through the voltage divider, the threshold voltage changes to prevent the power MOSFET from entering saturation, thereby eliminating the need for reset operations while maintaining reliable protection.
2Reliability
If the power MOSFET operates in saturation to limit current, then maximum saturation current is limited, but the protected device cannot be supplied properly when normal operating current exceeds the saturation current
Solution Approach 1:
The sensing transistor's threshold voltage is made dynamic through body effect, allowing it to operate in different regions (cutoff, linear, saturation) depending on the load current requirements. This dynamic operation enables the power MOSFET to supply full current during normal operation while still providing protection when overcurrent conditions occur.
Solution Approach 2:
By changing the threshold voltage parameter of the sensing transistor through body voltage modulation, the invention enables the system to adapt between two states: (1) allowing full current supply during normal operation when threshold voltage is low, and (2) limiting current during overcurrent events when threshold voltage increases, thus resolving the contradiction between protection and productivity.
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
Enables reversible current limitation, ensuring the protected device can operate within normal conditions without resets, maintaining the protection value even during overcurrent events by dynamically adjusting the sensing transistor's threshold voltage.
Implementation Method 1
A body-driving stage is coupled to the body terminal and configured to bias the body terminal of the sensing transistor as a function of an operating condition of the power transistor
Data Source
AI summary
An electrical protection device including an input line, an output terminal, and a power transistor coupled between the input line and the output terminal A sensing transistor is connected between the input line and the output terminal and has a body terminal. A control stage is coupled to respective control terminals of the power transistor and of the sensing transistor and is configured to limit a first current of the power transistor to a protection value. A body-driving stage is coupled to the body terminal and is configured to bias the body terminal of the sensing transistor as a function of an operating condition of the power transistor.