Parallel MOSFET Current Balancing via Individual Gate Control
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Solution Overview
Problem
In high current applications like servers and telecom equipment, parallel-connected MOSFETs in Efuses face current mismatch during the startup period due to variations in on-thresholds, leading to excessive stress and potential damage, especially at high temperatures.
Innovation Solution
The implementation of a circuit with multiple power transistors connected in parallel, each equipped with a current sensing circuit to sense and balance the current flowing through them, with control voltages adjusted based on the relationship between the current sensing signals to ensure equal current distribution among the transistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple MOSFETs are connected in parallel to handle high current, then the current handling capability is improved, but current mismatch during startup period causes excessive stress on individual MOSFETs
Solution Approach 1:
The patent implements a feedback mechanism where current sensing circuits continuously monitor the current through each MOSFET and feed this information back to the control circuit. The control circuit adjusts the gate-source voltage of each MOSFET based on the feedback signal to balance the current distribution, preventing any single MOSFET from bearing excessive stress during startup.
Solution Approach 2:
The patent enables each MOSFET to automatically adjust its own current contribution through self-service mechanisms. Each MOSFET is equipped with its own current sensing circuit and control circuit that independently regulates its gate-source voltage based on its own current status, allowing the system to self-balance without external intervention.
2Device complexity
If gate terminals of parallel MOSFETs are tied together for simple control, then the device complexity is reduced, but current mismatch occurs due to threshold voltage variations
Solution Approach 1:
The patent segments the control system by providing separate control circuits for each MOSFET instead of a single unified control. Each control circuit independently regulates its associated MOSFET based on individual current sensing feedback, allowing precise control of current distribution while maintaining manageable complexity through modular architecture.
Solution Approach 2:
The patent applies local quality by tailoring the control characteristics to each individual MOSFET's needs. Each MOSFET receives a customized gate-source voltage adjustment based on its specific current status and threshold voltage characteristics, rather than applying a uniform control signal to all devices.
Data Source
AI summary
A semiconductor device for limiting inrush current in hot-swap applications includes a power transistor and a current sensing circuit. The power transistor has a first terminal, a second terminal and a control terminal, wherein the first terminal is configured to receive an input voltage from a power supply, the second terminal is configured to provide an output voltage to a load, the control terminal is configured to receive a control voltage. Under regulation of the control voltage, the output voltage increases gradually towards the input voltage during a startup period and becomes substantially equal to the input voltage in a steady state. The current sensing circuit senses the current flowing through the power transistor and generates a current sensing signal. In order to achieve current balance, the control voltage is adjusted based on the relationship between the current sensing signal and current sensing signals of other semiconductor devices connected in parallel with the semiconductor device.