Semiconductor Current Limiting with Dynamic Gate Voltage Control
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Solution Overview
Problem
The existing semiconductor devices face challenges in accurately detecting overcurrents due to the overcurrent limit value being set higher than the maximum momentary inrush current, leading to decreased overcurrent detection accuracy and potential instability in load start-up.
Innovation Solution
A semiconductor device with a current limiting unit that includes a control transistor to manage the gate voltage of the main transistor, where the current limiting function is activated when the current exceeds a predetermined limit value and the control transistor's operating voltage meets a correction voltage threshold, ensuring accurate overcurrent detection and stable load start-up.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the overcurrent limit value is set higher than the maximum momentary inrush current to ensure stable load start-up, then the load can start up stably without current limitation, but the overcurrent detection accuracy decreases and lower current values cannot be detected as overcurrents
Solution Approach 1:
The patent segments the current detection and control function into two distinct modes: a first control mode during load start-up that allows inrush current to pass, and a second control mode during normal operation that provides accurate overcurrent detection. This segmentation resolves the contradiction by applying different current limit values at different operational stages, enabling both stable start-up and accurate overcurrent protection.
2Measurement precision
If the overcurrent limit value is set lower to improve overcurrent detection accuracy, then overcurrents can be detected more accurately, but the load start-up becomes unstable due to current limitation being imposed on inrush current
Solution Approach 1:
The patent implements dynamic adjustment of the overcurrent limit value based on the operational state of the load. During start-up, a higher current limit value is applied to accommodate inrush current, while during normal operation, a lower current limit value is applied for accurate overcurrent detection. This dynamic adaptation resolves the contradiction by making the system flexible rather than fixed.
3Device complexity
If a single overcurrent limit value is used for both start-up and normal operation, then the device structure remains simple, but it cannot simultaneously achieve stable start-up and accurate overcurrent detection
Solution Approach 1:
The patent changes the parameter of overcurrent limit value based on operational conditions. By switching between a first overcurrent limit value during start-up and a second overcurrent limit value during normal operation, the system achieves both stable start-up and accurate overcurrent detection without requiring complex additional hardware, thus maintaining simplicity while improving reliability.
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 solution enhances overcurrent detection accuracy and allows for stable load start-up by setting the current limit value lower than the maximum inrush current, preventing malfunctions and enabling cost reductions through chip size reduction while maintaining high reliability.
Implementation Method 1
a control transistor that controls the gate voltage of the main transistor
Implementation Method 2
the current limiting unit detects that an overcurrent is flowing from the main transistor, and activates the current limiting function, when the current flowing through the main transistor is equal to or greater than the current limit value
Data Source
AI summary
A semiconductor device, including a main transistor configured to supply power from a power source to a load, and a current limiting device including a control transistor. The current limiting device is configured to detect that the current flowing from the main transistor is an overcurrent, and to limit the current upon determining that the current is equal to or greater than a current limit value, and an operating voltage of the control transistor is equal to or greater than a current limiting activation voltage. The current limit value is a threshold for determining whether the current is greater than an operating current of the main transistor for the load to operate in a steady state. The current limiting activation voltage is a sum of a correction voltage and a predetermined threshold voltage at the gate of the control transistor when the current rises to the current limit value.