High-Voltage MOS Current Sensing Circuit for Overcurrent Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Integrated circuits with high-voltage n-channel MOS power transistors face challenges in monitoring drain current without increasing fabrication complexity or size, particularly in determining if the current exceeds a certain value while maintaining the power transistor in the on state.
Innovation Solution
Incorporating a high-voltage isolated n-channel MOS blocking transistor and a high-voltage n-channel MOS reference transistor, both sharing the same layer structure as the power transistor but with reduced channel width, along with a voltage comparator to detect overcurrent signals when the drain current exceeds a predetermined value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a current sensing circuit is added to monitor drain current in high-voltage power transistors, then overcurrent protection capability is improved, but fabrication complexity and circuit size increase
Solution Approach 1:
The patent creates a simplified copy of the power transistor structure by using the same diffusion regions (source, drain, and body regions) for both the power transistor and the sensing transistors. This copying approach allows the sensing circuit to be built using identical fabrication processes without requiring additional complex structures, thereby providing overcurrent protection while minimizing increases in fabrication complexity and circuit size.
2Ease of manufacture
If the power transistor body is directly connected to the substrate to simplify fabrication, then fabrication complexity is reduced, but current monitoring capability deteriorates
Solution Approach 1:
The patent segments the body region into multiple isolated body regions, each associated with specific source and drain regions to form individual sensing transistors. This segmentation allows the sensing transistors to be electrically isolated from the substrate while maintaining direct connection simplicity for the main power transistor, thereby enabling current monitoring without complicating the overall fabrication process.
Solution Approach 2:
The patent introduces sensing transistors as intermediary elements that bridge the power transistor and the current monitoring function. These sensing transistors are formed using the same diffusion regions but are electrically isolated to provide current sensing capability, acting as mediators that enable measurement without requiring complex additional structures or processes.
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 configuration allows for effective monitoring of drain current without increasing the complexity or size of the integrated circuit, providing an overcurrent signal when necessary, ensuring safe operation and efficient current management.
Implementation Method 1
a voltage comparator, configured to provide an overcurrent signal if drain current through the power transistor in the on state exceeds a predetermined value
Data Source
AI summary
An integrated circuit including a high-voltage n-channel MOS power transistor, a high-voltage n-channel MOS blocking transistor, a high-voltage n-channel MOS reference transistor, and a voltage comparator, configured to provide an overcurrent signal if drain current through the power transistor in the on state exceeds a predetermined value. The power transistor source node is grounded. The blocking transistor drain node is connected to the power transistor drain node. The blocking transistor source node is coupled to the comparator non-inverting input. The reference transistor drain node is fed by a current source and is connected to the comparator inverting input. The reference transistor gate node is coupled to a gate node of the power transistor. The comparator output provides the overcurrent signal. A process of operating the integrated circuit is disclosed.