Mirror-Current Switch Sampling for Precise Battery Current Detection

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Solution Overview

Problem

Existing current sampling methods for lithium batteries face challenges in achieving high precision due to the small sampling signal from small currents and temperature-dependent sampling resistor resistance, leading to significant sampling errors.

Innovation Solution

A high-precision current detection method that integrates current sampling switches and protection switches on the same chip, using a mirror current source method and adjusting the switching states based on the load of the current loop to optimize the sampling proportion parameter.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a sampling resistor is used to detect current by reading voltage at its two ends, then current sampling can be achieved, but the sampling signal is very small when small current is generated and sampling error is large

Engineering Contradiction:

Improvecurrent sampling precisionVSAvoidconduction loss

Core Design Contradiction:

Measurement precisionVSLoss of energy

Solution Approach 1:

The patent uses a mirror current source to create a scaled copy of the original current. The mirror current source generates a sampling current that is a fixed proportion of the original current, allowing small currents to be amplified to a measurable level without requiring a large sampling resistor that would cause excessive conduction loss.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The mirror current source acts as an intermediary device between the original current and the measurement system. It transforms the original current into a proportional sampling current that can be measured accurately by the ADC, eliminating the need for direct voltage measurement across a small sampling resistor.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If the sampling proportion parameter Q is increased to improve small current sampling, then the sampling signal is amplified, but the voltage withstanding performance of the device is compromised

Engineering Contradiction:

Improvesmall current sampling precisionVSAvoidvoltage withstanding performance

Core Design Contradiction:

Measurement precisionVSStrength

Solution Approach 1:

The patent implements dynamic adjustment of the sampling proportion parameter Q based on the magnitude of the original current. When the original current is small, Q is increased to amplify the sampling signal. When the original current is large, Q is decreased to maintain voltage withstanding performance. This dynamic adjustment resolves the contradiction between sampling precision and voltage withstanding capability.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the sampling proportion parameter Q as a variable parameter rather than a fixed value. By adjusting Q according to the original current magnitude, the system optimizes both small current sampling precision and voltage withstanding performance under different operating conditions.

Inventive Principle:

Principle #35Parameter changes

3Loss of energy

If multiple protection switches are used in parallel to reduce conduction loss, then the total resistance is reduced, but the current sampling signal is further divided and becomes weaker

Engineering Contradiction:

Improveconduction lossVSAvoidcurrent sampling signal strength

Core Design Contradiction:

Loss of energyVSMeasurement precision

Solution Approach 1:

The patent applies the mirror current source technique to each parallel protection switch branch. Each branch has its own mirror current source that generates a sampling current proportional to the current in that branch. The sampling currents from all branches are then summed to obtain the total current, ensuring that the sampling signal remains strong even when multiple switches are used in parallel.

Inventive Principle:

Principle #26Copying

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 method improves the signal-to-noise ratio and sampling precision while reducing conduction loss and system cost, particularly under large-current conditions.

Implementation Method 1

the current sampling switch obtains a current sampling signal Is by using a mirror current source method

Methodology Applied

Scientific EffectMirror current source:

Data Source

PatentUS20250118957A1High-precision current detection method and chip module therefor

Publication Date: 2025.04.10 SHANGHAI METAPWR ELECTRONICS CO LTD

AI summary

A high-precision current detection method for current detection in a current loop with at least two protection switches. The method includes: arranging a sampling bridge arm which are connected in parallel on at least one protection switch. The sampling bridge arm comprises at least one current sampling switch and at least one signal processing unit which are connected in series, the current sampling switches are at least two connected in parallel and/or at least two corresponding protection switches are connected in parallel; the current sampling switch obtains a current sampling signal Is by using a mirror current method; and the signal processing unit generates a protection switch current signal Ip according to the current sampling signal Is.