Switching Module Temperature Compensation for Accurate Current Sensing

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Solution Overview

Problem

Smart power switching modules face challenges in achieving 2% accuracy in load current sensing across all conditions due to temperature coefficient drift of the current replication ratio between power and sense switching devices, especially at extreme temperatures.

Innovation Solution

Incorporating temperature coefficient compensation resistance within the sense current path to counteract the effects of parasitic routing resistance, ensuring the sense current is partly compensated for temperature variations, thereby maintaining accurate load current sensing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If current replication ratio is used between power and sense switching devices, then load current sensing is achieved, but temperature coefficient drift causes accuracy degradation at extreme temperatures

Engineering Contradiction:

Improveload current sensing accuracyVSAvoidsensing accuracy under temperature variations

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent modifies the electrical parameters of the sense current path by introducing compensation resistors with specific temperature coefficients. These resistors are sized and positioned to counteract the temperature-dependent drift in the current replication ratio, thereby maintaining accurate load current sensing across varying temperatures without changing the fundamental sensing architecture

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces compensation resistors as intermediary elements in the sense current path. These resistors act as mediators that counterbalance the temperature-induced errors in the current replication ratio between the power and sense switching devices, enabling accurate current sensing under thermal variations

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of manufacture

If parasitic routing resistance is present in power switching device, then device fabrication is simplified, but temperature-induced errors increase in current sensing

Engineering Contradiction:

Improvedevice fabrication simplicityVSAvoidcurrent sensing accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent converts the harmful effect of parasitic routing resistance into a beneficial compensation mechanism. By intentionally adding compensation resistors with matched temperature coefficients to the sense current path, the circuit exploits the temperature-dependent behavior of resistive elements to cancel out the errors introduced by parasitic resistance, thereby maintaining sensing accuracy without requiring complex fabrication processes

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 effectively compensates for temperature-induced inaccuracies in load current sensing, ensuring consistent accuracy across varying temperatures and conditions, meeting the 2% accuracy requirement.

Implementation Method 1

at least one temperature coefficient compensation resistance within the path of the at least one sense current and arranged to cause the at least one sense current to be at least partly compensated for a temperature coefficient caused by at least one parasitic routing resistance

Methodology Applied

Scientific EffectTemperature coefficient compensation: Thermal Expansion

Data Source

PatentUS10103622B2Switching module

Publication Date: 2018.10.16 NXP USA INC

AI summary

A switching module comprising at least one power switching device arranged to output from an output node thereof a load current for the switching module, and at least one current sense component arranged to generate at least one sense current representative of the load current. The at least one current sense component comprises at least one temperature coefficient compensation resistance within the path of the at least one sense current and arranged to cause the at least one sense current to be at least partly compensated for a temperature coefficient caused by at least one parasitic routing resistance of a load current path for the at least one power switching device.