Battery Pack Power MOSFET Extraction for Charging Efficiency

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Solution Overview

Problem

Conventional battery charging systems are inefficient due to the use of large and expensive power MOSFETs as charging switches, which result in significant power loss and reliability issues, especially during discharge mode, and require additional driver circuitry that dissipates power even in idle modes.

Innovation Solution

A battery pack with a battery management unit and a transmitting unit that communicates via a power line to control the charger, using variation patterns in the charging current to transmit data and adjust charging parameters, eliminating the need for a large charging switch in the battery pack and reducing power loss by half.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a power MOSFET is used as a charging switch in the battery pack, then the charging function can be implemented, but the device size increases and cost increases

Engineering Contradiction:

Improvecharging functionVSAvoidPCB space

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The charging switch function is extracted from the battery pack and relocated to the charger. The battery pack no longer contains a charging switch, eliminating the need for large power MOSFETs and associated driver circuitry within the battery pack, thus reducing PCB space and component count while maintaining charging functionality through the charger's switching mechanism

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The charger is designed to perform multiple functions: it provides charging current, implements charging control, and houses the charging switch functionality. This multi-functional approach eliminates the need for dedicated charging switches in the battery pack, reducing overall system complexity and space requirements

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If a power MOSFET is used as a charging switch in the battery pack, then the charging function can be implemented, but the cost increases

Engineering Contradiction:

Improvecharging functionVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The expensive power MOSFET and driver circuitry are extracted from the battery pack and relocated to the charger, significantly reducing the bill of materials cost for the battery pack while maintaining the charging function through the charger's switching mechanism

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The charging switch functionality is implemented in the charger rather than the battery pack, allowing the use of more cost-effective switching solutions in the charger while the battery pack uses simpler, cheaper components

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Ease of operation

If a charging switch is kept in the battery pack, then charging control can be implemented, but power loss increases significantly during discharge mode

Engineering Contradiction:

Improvecharging controlVSAvoidpower loss

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

The charging switch is extracted from the battery pack and relocated to the charger. During discharge mode, the battery pack operates without the charging switch, eliminating unnecessary power dissipation while the charger maintains control capability through its own switching mechanism and communication with the battery management unit

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The charging switch in the charger is controlled periodically based on charging requirements and battery management unit instructions, allowing the switch to be off during discharge mode to eliminate power loss, and only activated when charging is needed

Inventive Principle:

Principle #19Periodic action

4Ease of operation

If driver circuitry is added to control the charging switch, then the charging switch can be controlled, but power loss increases even in idle modes

Engineering Contradiction:

Improveswitch controlVSAvoidpower loss

Core Design Contradiction:

Ease of operationVSLoss of energy

Solution Approach 1:

The driver circuitry is extracted from the battery pack and relocated to the charger along with the charging switch. This eliminates the continuous power dissipation of driver circuitry in the battery pack during idle modes, as the charger's driver circuitry can be controlled based on actual charging needs

Inventive Principle:

Principle #2Taking out (Extraction)

5Power

If a charging switch is used in the battery pack, then charging function is provided, but reliability decreases due to startup damage risk

Engineering Contradiction:

Improvecharging functionVSAvoidsystem reliability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The charging switch is extracted from the battery pack and relocated to the charger, eliminating the reliability issue of startup damage to the battery pack's charging switch. The charger's switching mechanism is designed to handle startup conditions appropriately, protecting the battery pack from damage risks

Inventive Principle:

Principle #2Taking out (Extraction)

Data Source

PatentUS10541542B2System and method for charging a battery pack

Publication Date: 2020.01.21 O2 MICRO INC

AI summary

A battery pack receives a charging current from a charger via a power line. The battery pack includes a battery management unit and a transmitting unit. The battery management unit is coupled to a plurality of battery cells and is operable for acquiring data associated with the battery pack. The transmitting unit is coupled to the battery management unit and is operable for transmitting the data to the charger via a power line.