Battery Charging Circuit Active Cell Balancing
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Solution Overview
Problem
Passive battery cell balancing techniques result in higher power losses due to energy dissipation, which limits the battery pack's capacity and runtime, especially when cells have inconsistent internal impedance and discharge rates.
Innovation Solution
A battery charging and discharging circuit with a second conversion circuit having a fixed step-down ratio, where the output terminals are connected to common nodes of battery cells, allowing for unequal charging currents until cells are balanced, thereby reducing power losses by transferring excess charge between cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If passive battery cell balancing technique is used, then battery cell equalization is achieved, but power losses increase due to energy dissipation
Solution Approach 1:
The patent introduces a DC-DC conversion circuit as an intermediary device between battery cells to transfer energy from cells with higher charge to cells with lower charge. This mediator enables direct energy transfer without dissipation, resolving the contradiction by replacing the passive resistor-based equalization with an active energy transfer mechanism that maintains overall battery capacity while achieving cell balancing.
Solution Approach 2:
The patent changes the operational parameters of battery cell equalization from passive energy dissipation to active energy transfer. By controlling the DC-DC conversion circuit, the system dynamically adjusts current flow between cells based on their charge states, transforming the equalization process from a lossy passive operation to an efficient active process that preserves energy.
2Reliability
If passive equalization uses resistors to dissipate excess energy, then battery cell balancing is achieved, but battery pack capacity is limited
Solution Approach 1:
The DC-DC conversion circuit serves as an intermediary that enables energy redistribution without loss. Instead of dissipating excess energy as heat through resistors, the converter transfers this energy to undercharged cells, effectively utilizing the full capacity of the battery pack and eliminating the capacity limitation imposed by passive equalization methods.
Solution Approach 2:
The patent recovers energy that would otherwise be discarded in passive equalization. By capturing the excess energy from overcharged cells and redirecting it to undercharged cells through the DC-DC converter, the system recovers what would be lost energy, thereby maintaining overall battery pack capacity while achieving cell balancing.
3Power
If multiple battery cells are connected in series, then power supply capability is improved, but cell inconsistency in internal impedance and discharge rate causes balancing issues
Solution Approach 1:
The patent implements a feedback control mechanism where the DC-DC conversion circuit continuously monitors the charge states of individual battery cells and adjusts current distribution accordingly. This feedback loop compensates for cell inconsistencies in internal impedance and discharge rate, maintaining reliable operation of series-connected cells by dynamically balancing their charge levels based on real-time conditions.
Solution Approach 2:
The system transitions from static equalization to dynamic balancing. The DC-DC conversion circuit actively adjusts current flow between cells based on their instantaneous charge states, internal impedances, and discharge rates. This dynamic approach allows the system to adapt to cell inconsistencies and maintain optimal charging/discharging balance, thereby improving reliability of series-connected battery packs.
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 method effectively balances battery cells with minimal power loss, extending battery life and maintaining capacity by actively managing charging currents, unlike passive methods that dissipate excess energy.
Implementation Method 1
a first conversion circuit, wherein an input terminal of the first conversion circuit is used to connect to an external power supply, and an output terminal of the first conversion circuit is connected to an input terminal of the second conversion circuit and a first terminal of the battery pack
Implementation Method 2
The second conversion circuit has N-1 output terminals. The step-down ratio of the second conversion circuit is a fixed value. The Mth output terminal is used to output the input voltage of M/N
Implementation Method 3
Each one of the common nodes of the N battery cells, in the order from the second terminal to the first terminal of the battery pack, is connected to one of the output terminals of the second conversion circuits from a low voltage to a high voltage
Data Source
AI summary
A charging and discharging circuit includes a first conversion circuit and a second conversion circuit. The input terminal of the first conversion circuit is used to connect an external power supply. The output terminal of the first conversion circuit is connected to the input terminal of the second conversion circuit and the first terminal of a battery pack, and the second terminal of the battery pack is grounded. N battery cells have N-1 common nodes. Each common node is connected to a corresponding output terminal of the second conversion circuit. In the embodiment of the present application, the second conversion circuit effectively “transfers” the excess charge on the cell with a higher battery voltage in the battery pack to the cell with a lower voltage through the uneven distribution of the charging current.