Sense Resistor Current Sensing via Square-Wave Signal Conversion

Solution Overview

Problem

Current sensors face challenges in efficiently sensing currents across sense resistors without requiring high-withstand-voltage transistors, leading to increased size and cost due to the need for high-voltage compatibility.

Innovation Solution

A current sensor design that includes a square wave generation circuit and a current sense signal output circuit, using a switch control circuit to generate a square-wave signal with an amplitude proportional to the sense resistor voltage, allowing for reduced withstand voltage requirements in circuit elements by alternating switch states and utilizing low-withstand-voltage transistors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If high-withstand-voltage transistors are used to sense current across the sense resistor, then the current sensing capability is improved, but the device size and manufacturing cost increase

Engineering Contradiction:

Improvecurrent sensing capabilityVSAvoiddevice size

Core Design Contradiction:

ReliabilityVSWeight of stationary object

Solution Approach 1:

The current sensing function is divided into two separate circuits: a square wave generation circuit that handles high-voltage switching to generate a square wave signal proportional to the sense resistor voltage, and a current sense signal output circuit that processes this signal at low voltage to generate the current sense signal. This segmentation allows each circuit to be optimized for its specific voltage level, enabling the use of low-withstand-voltage transistors in the signal processing path while maintaining accurate current sensing capability.

Inventive Principle:

Principle #1Segmentation

2Reliability

If high-withstand-voltage transistors are used to sense current across the sense resistor, then the current sensing capability is improved, but the manufacturing cost increases

Engineering Contradiction:

Improvecurrent sensing capabilityVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The current sensing function is divided into two separate circuits: a square wave generation circuit that handles high-voltage switching to generate a square wave signal proportional to the sense resistor voltage, and a current sense signal output circuit that processes this signal at low voltage to generate the current sense signal. This segmentation allows each circuit to be optimized for its specific voltage level, enabling the use of low-withstand-voltage transistors in the signal processing path while maintaining accurate current sensing capability.

Inventive Principle:

Principle #1Segmentation

3Measurement precision

If the circuit elements are designed for high-voltage compatibility, then the current sensing accuracy is maintained, but the component size increases

Engineering Contradiction:

Improvecurrent sensing accuracyVSAvoidcomponent size

Core Design Contradiction:

Measurement precisionVSArea of moving object

Solution Approach 1:

The current sensing function is divided into two separate circuits: a square wave generation circuit that handles high-voltage switching to generate a square wave signal proportional to the sense resistor voltage, and a current sense signal output circuit that processes this signal at low voltage to generate the current sense signal. This segmentation allows each circuit to be optimized for its specific voltage level, enabling the use of low-withstand-voltage transistors in the signal processing path while maintaining accurate current sensing capability.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A square wave signal serves as an intermediary between the high-voltage sense resistor and the low-voltage signal processing circuit. The square wave generation circuit converts the high-voltage differential signal into a square wave signal that preserves the current information, which can then be processed by low-voltage transistors without requiring high-withstand-voltage components, thereby reducing component size while maintaining sensing accuracy.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS20240125823A1Current sensor

Publication Date: 2024.04.18 ROHM CO LTD

AI summary

A current sensor includes: a first and a second input terminal configured to be capable of having a sense resistor connected therebetween; a square wave generation circuit connected to the first and second input terminals and configured to be capable of generating a square-wave signal with an amplitude proportional to the voltage across the sense resistor; and a current sense signal output circuit configured to be capable of outputting based on the square-wave signal a current sense signal corresponding to the current passing through the sense resistor.