Bidirectional MOSFET Body Current Reduction
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Solution Overview
Problem
Existing IC switches, particularly MOSFETs, face inaccuracies in monitoring reverse current due to body current issues, leading to increased complexity and cost when bidirectional current flow is required, as existing techniques fail to accurately measure current density.
Innovation Solution
The design of a bidirectional MOSFET switch with a body region, buried layer, and configuration switch that reduces body current by connecting the body terminal to the buried layer terminal when the source terminal voltage exceeds the drain terminal voltage, using a semiconductor configuration that enables accurate current monitoring without additional complex circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the sense-transistor technique is used for bidirectional current monitoring, then current monitoring capability is improved, but measurement precision deteriorates for reverse current flows
Solution Approach 1:
The patent extracts and eliminates the body current component that causes measurement errors in reverse direction by connecting the body terminal to the source terminal through a configuration switch, thereby isolating the error source and enabling accurate bidirectional measurement
Solution Approach 2:
The patent dynamically configures the body terminal connection based on current direction: connecting body to source during reverse current flow to eliminate body current errors, and connecting body to buried layer during forward current flow for normal operation, thus adapting the measurement system to bidirectional requirements
2Adaptability or versatility
If existing current monitoring techniques are used for bidirectional flow, then bidirectional monitoring is achieved, but device complexity increases
Solution Approach 1:
The configuration switch serves multiple functions: it acts as a body terminal connection switch for error elimination, a current path selector for bidirectional operation, and an enabler for both forward and reverse current monitoring using the same sense transistor, thus reducing overall circuit complexity
Solution Approach 2:
The sense transistor inherently monitors both forward and reverse current flows when properly configured, and the configuration switch automatically adjusts the body terminal connection based on current direction, enabling the system to self-adapt to bidirectional operation without additional monitoring circuitry
3Device complexity
If body current is not eliminated in reverse-biased MOSFETs, then device simplicity is maintained, but measurement precision deteriorates
Solution Approach 1:
The configuration switch proactively connects the body terminal to the source terminal before or during reverse current flow, preventing body current from affecting the measurement in the first place, rather than attempting to correct measurement errors after they occur
Solution Approach 2:
The patent applies preliminary anti-action by preemptively eliminating the body current error source through terminal reconfiguration, counteracting the measurement error mechanism before it can degrade precision in reverse-biased operation
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 allows for accurate bidirectional current monitoring without the need for external or internal sensing resistors, reducing complexity and cost while minimizing reverse recovery losses and switching time.
Implementation Method 1
The gate terminal is drivable to form a channel in the body region, thereby enabling conduction between the source terminal and the drain terminal
Implementation Method 2
the accuracy of reverse current monitoring may be aided by the elimination of body current through reverse-biased MOSFETs
Data Source
AI summary
An illustrative bidirectional MOSFET switch includes a body region, a buried layer, a gate terminal, and a configuration switch. The body region is a semiconductor of a first type separating a source region and a drain region that are a semiconductor of a second type. The buried layer is a semiconductor of the second type separating the body region from a substrate that is a semiconductor of the first type. The gate terminal is drivable to form a channel in the body region, thereby enabling conduction between the source terminal and the drain terminal. The configuration switch connects the body terminal to the buried layer terminal when the source terminal voltage exceeds the drain terminal voltage.