Pulsed MOSFET Gate Control for Inrush Current and Thermal Limits
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Solution Overview
Problem
Hot-swappable components and e-fuses face challenges in managing inrush currents, leading to potential transistor failure due to excessive current and thermal overload, as traditional power MOSFETs are often oversized and prone to failure under high inrush conditions.
Innovation Solution
A pulsed gate control technique is employed to regulate the current through a transistor by pulsing the gate on and off, allowing for higher safe operating currents for short periods while cooling the transistor between pulses, thereby preventing overheating and damage, using a feedback controller to adjust the voltage pulses based on measured drain source voltage and current levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a series element with resistance is used to control inrush current, then current flow is limited during startup, but the element cannot handle very large inrush currents and may fail
Solution Approach 1:
The patent applies periodic pulsed gate control to the transistor, turning the transistor on and off in pulses during startup. This allows the transistor to conduct current in controlled bursts rather than continuously, preventing thermal overload while still enabling the system to charge large capacitance. The pulsed operation transforms the continuous harmful inrush current into periodic, manageable current pulses.
Solution Approach 2:
The patent dynamically adjusts the gate voltage of the transistor during operation, transitioning from static resistance control to dynamic control. The gate voltage is modulated in real-time based on operating conditions, allowing the transistor's effective resistance to change dynamically. This enables the transistor to handle varying inrush current levels while maintaining safe operating temperatures through adaptive control.
2Object-affected harmful factors
If a power MOSFET is oversized to handle large inrush currents, then current handling capability is sufficient, but the device is prone to failure due to excessive current and thermal overload
Solution Approach 1:
The patent uses periodic pulsed operation to allow the transistor to conduct high currents only during brief pulses rather than continuously. This intermittent operation prevents thermal accumulation that would lead to thermal overload, enabling the use of smaller, more reliable transistors that can handle the peak current pulses but would otherwise fail under continuous high current conditions.
Solution Approach 2:
The patent changes the operating parameters of the transistor by dynamically adjusting the gate voltage and pulse width. This allows the transistor to operate in different regions of its characteristic curves, optimizing performance for both high current handling and thermal management. The parameter changes enable the transistor to safely handle large inrush currents without exceeding thermal limits.
3Productivity
If continuous gate voltage is applied to the transistor, then the transistor remains on and conducts current continuously, but the transistor overheats due to sustained high current
Solution Approach 1:
The patent replaces continuous gate voltage with periodic pulsed gate voltage. The transistor is turned on during pulses to conduct current and turned off between pulses to cool down. This periodic on-off operation maintains current conduction productivity during active pulses while providing thermal relief during off periods, preventing sustained overheating.
Solution Approach 2:
The patent applies preliminary cooling action by turning the transistor off between current pulses. This intentional interruption allows heat dissipation to occur before the next current pulse, preventing thermal accumulation. The cooling action is built into the operating cycle itself, ensuring the transistor remains within safe temperature limits.
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 method effectively manages inrush currents, allowing for higher safe operating currents during short pulses and reducing the risk of transistor damage by cooling the device between pulses, thus enhancing the reliability of hot-swappable components and e-fuses.
Implementation Method 1
adjusting, for each of a first sequence of current pulses, a voltage of a voltage pulse applied to a control node of the transistor using a feedback controller until the current measured through the transistor is not greater than a first function of the safe operating current
Data Source
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AI summary
A method of controlling current through a transistor is provided. A voltage and current through the transistor are measured. A safe operating current for the voltage is determined. For each of a first sequence of current pulses, a voltage of a voltage pulse applied to a control node of the transistor using a feedback controller is adjusted until the current measured through the transistor is not greater than a first function of the safe operating current. For each of a second sequence of current pulses after the first sequence of current pulses, the voltage of the voltage pulse applied to the control node of the transistor using the feedback controller is adjusted until the current measured through the transistor is not greater than a second function of the safe operating current.