Battery Protection Circuit Isolation Device Failure Detection

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Solution Overview

Problem

Rechargeable battery modules with active protection circuits face increased cost, complexity, and reduced efficiency due to constant drain on battery cells, leading to faster discharge and potential damage from protection circuitry, especially when not in use or stored for extended periods.

Innovation Solution

A battery module system with reduced protection circuit footprint and component count, utilizing a first and second isolation device controlled by sensing circuits to isolate charger and battery terminals, and a bypass control module to minimize leakage current when the load is inactive, thereby extending storage life and reducing discharge rate.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If active protection circuits are used to protect battery modules, then safety and protection capability are improved, but cost and complexity increase

Engineering Contradiction:

Improveprotection capabilityVSAvoidcircuit complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent combines multiple protection functions (overcharge protection, over-discharge protection, short circuit protection, and leakage current detection) into a single integrated protection circuit. The isolation device performs both the primary protection function and the leakage detection function, eliminating the need for separate redundant circuits and reducing overall system complexity while maintaining comprehensive safety coverage.

Inventive Principle:

Principle #5Merging (Combining)

2Reliability

If active protection circuits are used to protect battery modules, then safety is improved, but manufacturing cost increases

Engineering Contradiction:

Improveprotection capabilityVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The isolation device is designed to perform multiple functions: it acts as the primary protection switch for overcharge/over-discharge conditions, serves as the detection point for leakage current monitoring, and provides the isolation function between battery and load. This multi-functionality reduces the total component count and bill of materials cost while maintaining comprehensive protection capabilities.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If active protection circuits are used to protect battery modules, then protection capability is improved, but battery discharge rate increases

Engineering Contradiction:

Improveprotection capabilityVSAvoidbattery discharge rate

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The protection circuit uses periodic sampling of leakage current instead of continuous monitoring. The sensing circuit periodically measures the current through the isolation device and only activates the protection function when abnormal current levels are detected. This periodic action significantly reduces the constant drain on battery cells while maintaining effective protection capability.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The protection circuit dynamically adjusts its operation based on actual battery conditions. The isolation device remains in a high-impedance state during normal operation to minimize leakage, and only transitions to active protection mode when sensing circuits detect abnormal conditions such as overcharge, over-discharge, short circuit, or excessive leakage current. This dynamic behavior minimizes energy loss while maintaining protection readiness.

Inventive Principle:

Principle #15Dynamics

4Reliability

If redundant circuitry is added to meet safety standards, then safety is improved, but physical size increases

Engineering Contradiction:

ImprovesafetyVSAvoidcircuit footprint

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The patent integrates the leakage current detection function into the existing isolation device structure rather than adding separate detection circuits. The sensing circuits utilize the isolation device's inherent electrical characteristics to detect abnormal leakage currents, and the control logic is merged with the protection circuit's existing control mechanisms. This integration achieves redundant safety coverage without increasing the physical footprint of the protection circuit.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS11502520B2Battery protection circuit with isolation device failure detection

Publication Date: 2022.11.15 MOTOROLA SOLUTIONS INC

AI summary

A battery module includes a first load terminal, a second load terminal, a first charger terminal, a charger enable terminal, and a battery having a first battery terminal coupled to the first load terminal and a second terminal coupled to the second load terminal. A first isolation device is coupled between the first load terminal and the first charger terminal and has an enable terminal coupled to the charger enable terminal. A first protection circuit includes a second isolation device coupled between the second battery terminal and the second load terminal and a first sensing circuit configured to enable the second isolation device responsive to detecting a failure of the first isolation device.