MOSFET Inrush Current Control via Dynamic Gate Feedback
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Solution Overview
Problem
In hot-swappable electronic systems, the high inrush current caused by large capacitance components can lead to power MOSFET failure due to exceeding current handling limits or thermal issues, necessitating oversized and costly components.
Innovation Solution
A method and system that measure voltage and current across a transistor, determine a safe operating current, and use a feedback controller to adjust the control node voltage to maintain the current within safe operating limits, allowing for smaller transistors and reduced costs while preventing inrush current-related failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a series element (power MOSFET) is used to control inrush current, then current flow is controlled during startup, but the MOSFET may fail due to exceeding maximum current or thermal limits
Solution Approach 1:
The patent implements dynamic control of the MOSFET gate voltage to adjust the series element's resistance in real-time during startup. The controller dynamically modifies the gate voltage based on monitored current and voltage conditions, allowing the MOSFET to transition smoothly from high resistance to low resistance, preventing both overcurrent and thermal damage while maintaining reliability.
Solution Approach 2:
The system employs feedback control by continuously monitoring the current through and voltage across the series element during startup. This feedback information is used by the controller to adjust the gate voltage of the MOSFET, ensuring the device operates within safe current and thermal limits, thereby preventing failure while effectively controlling inrush current.
2Object-affected harmful factors
If oversized power MOSFETs are used to handle very large inrush currents, then current handling capability is improved, but device cost and size increase
Solution Approach 1:
The patent changes the operating parameters of the MOSFET dynamically during startup by adjusting the gate voltage. This allows a smaller, more cost-effective MOSFET to handle large inrush currents temporarily during the startup phase, rather than requiring an oversized device rated for continuous high current. The parameter change enables the device to operate safely within its capabilities without needing excessive margin.
Solution Approach 2:
The system applies periodic or pulsed gate voltage to the MOSFET during the startup phase to control inrush current. By using time-limited control action during the critical startup period, a smaller MOSFET can handle the transient high current without requiring the continuous current handling capability of an oversized device, thus reducing cost and size.
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 limits inrush current within safe operating areas, enhancing reliability and reducing component size and cost, while ensuring reliable operation without overheating.
Implementation Method 1
adjusting a voltage of a control node of the transistor using a feedback controller until the measured current through the transistor is not greater than the determined safe operating current
Data Source
AI summary
In accordance with an embodiment of the present invention, a method of controlling current through a transistor includes measuring a voltage across the transistor, measuring a current through the transistor, determining a safe operating current for the measured voltage across the transistor, and adjusting a voltage of a control node of the transistor using a feedback controller until the measured current through the transistor is not greater than the determined safe operating current.