Battery Protection Circuit Using Current Mirror MOSFETs

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Solution Overview

Problem

Existing secondary battery protection systems, such as those using Li-ion cells, face inefficiencies due to power consumption in detection resistances during charging and discharging operations, leading to reduced continuous operation time and measurement precision issues.

Innovation Solution

The implementation of charge and discharge current detection MOSFETs with different cell ratios and corresponding detection resistances in parallel with control MOSFETs on the charge and discharge paths, forming current mirror circuits to minimize power consumption and improve measurement precision.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If detection resistances are used to monitor charge and discharge currents, then current detection function is achieved, but power consumption increases and continuous operation time decreases

Engineering Contradiction:

Improvecurrent detection precisionVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent replaces the traditional resistance-based current detection method with a magnetic field-based detection method using Hall effect sensors. This substitution eliminates the need for detection resistances in the current path, thereby removing the power consumption associated with these resistances while maintaining accurate current detection capability through magnetic field measurement.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 configuration reduces power consumption, extends continuous operation time, and enhances measurement precision of battery state, allowing for more accurate detection of charge and discharge currents.

Implementation Method 1

charge and discharge current detection MOSFETs with different cell ratios and detection resistances in parallel with control MOSFETs on charge and discharge paths, forming current mirror circuits

Methodology Applied

Scientific EffectCurrent mirror effect:

Data Source

PatentUS9742207B2Cell protection system

Publication Date: 2017.08.22 RENESAS ELECTRONICS CORP

AI summary

A cell protection system includes a charge control MOSFET, a charge current detection MOSFET, a discharge control MOSFET, a discharge current detection MOSFET, a charge current detection resistance, a discharge current detection resistance and a control circuit. The charge current detection MOSFET has a drain and a gate common with the charge control MOSFET. The discharge control MOSFET has a drain common with the charge control MOSFET. The discharge current MOSFET has a drain and a gate common with discharge control MOSFET. The charge current detection resistances and the discharge current detection resistance are provided in correspondence to the charge current detection MOSFET and the discharge current detection MOSFET, respectively. The control circuit generates a gate control signal for the charge control MOSFET and the charge current detection MOSFET by using the charge current detection resistance and generates a gate control signal for the charge control MOSFET and the discharge current detection MOSFET by using the discharge current detection resistance.