Bidirectional MOSFET Current Sensing With Dual Sense Circuits

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Solution Overview

Problem

Existing field-effect transistors lack the ability to accurately sense current flow in both directions, limiting their effectiveness in high-power circuits where current direction can change.

Innovation Solution

A bidirectional current sense circuit is introduced, comprising two current sense circuits with sense transistors, operational amplifiers, and mirroring current sources to generate a current sense signal regardless of current direction, using miniaturized transistors and feedback loops to stabilize voltage conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a single current sense circuit is used to sense power current, then the circuit complexity is reduced, but the ability to sense current in both directions is lost

Engineering Contradiction:

Improvebidirectional current sensing capabilityVSAvoidcurrent sense circuit structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The current sense circuit is divided into two separate circuits: a first current sense circuit for sensing positive current flow (drain to source) and a second current sense circuit for sensing negative current flow (source to drain). Each circuit includes its own sense transistor, operational amplifier, and mirroring current source, allowing independent optimization for each current direction while maintaining overall system functionality.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The bidirectional current sense circuit achieves multi-functionality by enabling the same system to sense current in both positive and negative directions through the coordinated operation of two current sense circuits. The output nodes of both circuits are connected to a common output, allowing the system to universally sense current regardless of flow direction.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Measurement precision

If miniaturized sense transistors are used in the current sense circuit, then the power current sensing accuracy is improved, but the current handling capability of the sense circuit is reduced

Engineering Contradiction:

Improvepower current sensing accuracyVSAvoidcurrent handling capability

Core Design Contradiction:

Measurement precisionVSPower

Solution Approach 1:

A mirroring current source is introduced as an intermediary component between the sense transistor and the output. The mirroring current source copies the current flowing through the sense transistor and provides it to the output node, allowing the miniaturized sense transistor to accurately sense power current without being directly exposed to high power conditions, thus maintaining both accuracy and safety.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS12493061B2Bidirectional current sense for power field-effect transistor

Publication Date: 2025.12.09 INFINEON TECH CANADA INC

AI summary

A bidirectional current sense circuit allowing for sensing of power current passing through a power field-effect transistor, regardless of the direction of the power current. The bidirectional current sense circuit outputs a current sense signal representing the power current onto a current sense output node. The bidirectional current sense circuit includes the power field-effect transistor, and two current sense circuits. One of the current sense circuits senses the power current when the power current flows in the positive direction. The other current sense circuit senses the power current when the power current flows in the negative direction.