Battery Center Tap Capacitive Store for Loss-Free Switching

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Solution Overview

Problem

Existing battery systems face significant switching losses due to high voltage and current changes during tap switching, leading to inefficiencies, electromagnetic compatibility issues, and the need for complex protective circuitry, particularly in electric vehicles.

Innovation Solution

A battery system with a center tap and capacitive store that allows changeover at zero current and maximum voltage, utilizing low-frequency switches and inductive-capacitive networks to minimize switching losses and ensure even battery element loading, enabling zero-voltage or zero-current switching.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If conventional switching elements are used for changing over between battery elements, then the battery system can operate, but switching losses are excessive due to high voltage and current during changeover

Engineering Contradiction:

Improveswitching lossesVSAvoidchangeover speed

Core Design Contradiction:

Loss of energyVSProductivity

Solution Approach 1:

The circuit is designed to automatically charge the capacitive store before a changeover event, so that when the switching element needs to change state, the capacitive store is already prepared with sufficient voltage to enable loss-free commutation. This preliminary charging action eliminates the need for high current during switching transitions.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

A capacitive store is introduced as an intermediary energy storage element between the battery elements and the switching element. This capacitor acts as a buffer that absorbs and releases energy during transitions, mediating the changeover process and preventing direct high-current switching between battery elements.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If conventional protective circuitry is added to handle switching transients, then switching reliability improves, but device complexity increases

Engineering Contradiction:

Improveswitching reliabilityVSAvoidcircuit complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The capacitive store automatically performs the protective function by naturally limiting current during switching transitions through its voltage-dependent characteristics. The circuit self-regulates the switching process without requiring external protective components or complex control logic, as the capacitor's inherent properties provide the necessary current limiting and voltage stabilization.

Inventive Principle:

Principle #25Self-service

3Speed

If changeover speed is increased to improve productivity, then system response improves, but switching losses increase due to tail currents and electromagnetic interference

Engineering Contradiction:

Improvechangeover speedVSAvoidswitching losses

Core Design Contradiction:

SpeedVSLoss of energy

Solution Approach 1:

The circuit operates by changing the voltage parameter of the capacitive store over time, allowing the switching element to transition at optimal moments when the capacitive store voltage facilitates loss-free commutation. This parameter-based control enables fast switching without the traditional trade-off between speed and losses.

Inventive Principle:

Principle #35Parameter changes

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 approach reduces switching losses by performing changeovers at minimal current and voltage levels, enhancing efficiency, reducing electromagnetic interference, and allowing for automatic charge equalization across battery elements, thereby improving the overall performance and cost-effectiveness of battery management systems.

Implementation Method 1

the center tap has a first capacitive store arranged on it that has a store voltage that appears over an appropriate period in accordance with a first and/or second battery element voltage

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

utilizing low-frequency switches and inductive-capacitive networks to minimize switching losses

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS10135266B2Battery system for motor vehicle with loss-free switching and automatic charge equalization

Publication Date: 2018.11.20 DR ING H C F PORSCHE AG

AI summary

A battery system having a battery having at least one first battery element, at least one second battery element and a center tap between the at least one first and the at least one second battery element, a power changeover switch having a plurality of switching elements for changing over between the at least one first battery element and the at least one second battery element, and at least one pair of output terminals that is electrically connected to the battery, wherein the center tap has a first capacitive store arranged on it that has a store voltage that appears over an appropriate period in accordance with a first and/or second battery element voltage provided by the first and/or second battery element, wherein during the period in which the store voltage appears, a store current decreases from a maximum value to a value of zero.