Bidirectional DC-DC Voltage Balancing for Battery String Imbalance

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Solution Overview

Problem

The existing architecture of electric or hybrid electric vehicles experiences power imbalances between high-voltage battery strings due to asymmetric power consumption by DC-DC converters, leading to inefficient energy distribution, especially when the vehicle is in motion.

Innovation Solution

A buck/boost DC-DC converter with Silicon Carbide MOSFET switches and protective fuses is implemented to actively balance voltage between battery strings, allowing real-time balancing even during traction mode propulsion, using a controller to manage switching operations and ensure efficient power transfer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If passive balancing is used during parked mode, then voltage balancing can be achieved, but vehicle mobility is restricted and balancing cannot occur during traction mode

Engineering Contradiction:

Improvevoltage balancing capabilityVSAvoidvehicle operational flexibility

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent implements a dynamic voltage balancing system that can operate in both parked mode (passive balancing) and traction mode (active balancing). The system dynamically switches between balancing strategies based on vehicle operational state, enabling voltage balancing during both stationary and moving conditions without restricting vehicle mobility

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The voltage balancing circuit is designed to perform multiple functions: passive balancing during parked mode and active balancing during traction mode. This multi-functional approach allows the same system to maintain voltage balance across different operational scenarios, enhancing both reliability and adaptability

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Power

If DC-DC converters operate with asymmetric power consumption, then power conversion is achieved, but power imbalances between battery strings occur

Engineering Contradiction:

Improvepower conversion capabilityVSAvoidpower balance between battery strings

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent employs a control system that continuously monitors voltage levels across battery strings and adjusts DC-DC converter operation accordingly. This feedback mechanism detects power imbalances caused by asymmetric power consumption and dynamically adjusts converter duty cycles to maintain equal voltage levels between battery strings

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system changes operational parameters of DC-DC converters dynamically based on real-time voltage measurements. By adjusting conversion ratios, power transfer rates, and switching frequencies, the system compensates for asymmetric power consumption and maintains power balance between battery strings

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If voltage balancing is delayed until parked mode, then simple control logic is maintained, but energy efficiency decreases and battery life is reduced

Engineering Contradiction:

Improvecontrol logic simplicityVSAvoidenergy efficiency

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The patent implements continuous voltage balancing operation during both parked mode and traction mode. Rather than delaying balancing until the vehicle is stationary, the system performs balancing continuously during all operational phases, preventing energy losses and maintaining optimal battery conditions throughout vehicle usage

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

The system performs preliminary voltage balancing during traction mode before significant voltage imbalances develop. By proactively managing voltage levels during operation rather than reactively correcting them during parked mode, the system reduces overall energy losses and extends battery life

Inventive Principle:

Principle #10Preliminary action

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

The solution provides efficient voltage balancing with up to 97% efficiency, maintaining vehicle performance and extending battery life by actively managing power imbalances in real-time, even when the vehicle is in motion.

Implementation Method 1

A buck/boost DC-DC converter with Silicon Carbide MOSFET switches is implemented to actively balance voltage between battery strings

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

buck/boost DC-DC converter with Silicon Carbide MOSFET switches

Methodology Applied

Scientific EffectSemiconductor conduction:

Data Source

PatentUS20240140270A1Voltage balancing circuit and controller for same

Publication Date: 2024.05.02 LEAR CORP

AI summary

A voltage balancing circuit includes a direct-current-to-direct-current (DC-to-DC) voltage converter interconnecting a first battery having a first voltage and a second battery having a second voltage, wherein the DC-to-DC converter transfers electrical power from the first battery to the second battery when the first voltage is greater than the second voltage, and transfers electrical power from the second battery to the first battery when the first voltage is less than the second voltage, and wherein the transfer of electrical power from the first battery to the second battery or from the second battery to the first battery balances the electrical power difference between the first battery and the second battery.