Passive Resonant Bidirectional Converter for Battery Cell Balancing
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Solution Overview
Problem
Traditional battery cell balancing methods are inefficient and complex, often requiring direct galvanic connections, dissipative components, and digital control schemes, which reduce system reliability and efficiency, and can lead to energy loss and cell failure in lithium and super-capacitor systems.
Innovation Solution
A passive resonant bidirectional converter system that uses center tapped windings, chopper circuits, and resonant tank circuits to automatically synchronize and transfer energy across a galvanic barrier, eliminating the need for direct connections and complex control schemes, and achieving efficient balancing without energy dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dissipative balancing method using resistive shunts is used, then cell voltage balancing is achieved, but energy efficiency deteriorates due to power dissipation
Solution Approach 1:
The patent introduces a resonant tank circuit as an intermediary between cells with different voltages. This circuit uses capacitive coupling to transfer energy from higher voltage cells to lower voltage cells through a shared resonant frequency, avoiding direct resistive dissipation. The intermediary circuit enables energy redistribution while maintaining overall system energy efficiency.
Solution Approach 2:
The patent replaces the traditional resistive (dissipative) balancing mechanism with a resonant electromagnetic field-based energy transfer system. By using oscillating electric fields at resonant frequency to couple cells together, the system substitutes lossy resistive connections with efficient electromagnetic energy exchange, eliminating the need for power-dissipating shunt resistors.
2Reliability
If traditional dissipative balancer with multiple components is used, then cell balancing is achieved, but system reliability deteriorates
Solution Approach 1:
The patent merges multiple balancing functions into a single resonant tank circuit that can simultaneously balance multiple cells. By combining the balancing operation for all cells into one unified resonant system sharing common capacitors and inductors, the design eliminates the need for separate resistive shunts for each cell, reducing component count while maintaining balancing capability.
Solution Approach 2:
The resonant tank circuit serves multiple functions simultaneously: it provides energy transfer between cells, establishes resonant coupling, and enables bidirectional energy flow. This universal circuit architecture replaces multiple specialized components (individual shunt resistors, control circuits for each cell) with a single multi-functional resonant system that handles all balancing operations.
3Use of energy by moving object
If direct galvanic connection is used for balancing, then energy transfer is achieved, but system reliability deteriorates due to direct exposure to cell voltage variations
Solution Approach 1:
The patent introduces capacitive coupling through the resonant tank circuit as an intermediary between cells. This intermediary provides galvanic isolation while enabling energy transfer through electric field coupling. The capacitive interface blocks direct current flow and voltage transient propagation, protecting cells from each other's voltage variations while maintaining efficient energy transfer through the resonant electromagnetic field.
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 system efficiently balances cell voltages, maximizes energy storage, and extends battery life by redistributing charge without dissipating power, while being simpler, more reliable, and lighter, with fewer components, and capable of quick energy transfer.
Implementation Method 1
a resonant tank circuit including at least the inductance of the center tap winding and the parasitic capacitance of the chopper circuit for operating the converter section at resonance
Implementation Method 2
the center tapped windings of the first and second converter sections being disposed on a first common winding core and the inductance feed windings of the first and second converter sections being disposed on a second winding core for automatically synchronizing the resonant oscillation
Data Source
AI summary
A passive resonant bidirectional converter system that transports energy across a galvanic barrier includes a converter using at least first and second converter sections, each section including a pair of transfer terminals, a center tapped winding; a chopper circuit interconnected between the center tapped winding and one of the transfer terminals; an inductance feed winding interconnected between the other of the transfer terminals and the center tap and a resonant tank circuit including at least the inductance of the center tap winding and the parasitic capacitance of the chopper circuit for operating the converter section at resonance; the center tapped windings of the first and second converter sections being disposed on a first common winding core and the inductance feed windings of the first and second converter sections being disposed on a second common winding core for automatically synchronizing the resonant oscillation of the first and second converter sections and transferring energy between the converter sections until the voltage across the pairs of transfer terminals achieves the turns ratio of the center tapped windings.