Charge-Discharge Control Circuit for Battery Cell Balance
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Solution Overview
Problem
Conventional charge-discharge control circuits for battery packs with multiple cells fail to sufficiently reduce voltage differences between cells, leading to inefficient charging and discharging, premature cell deterioration, and reduced battery pack lifetime due to uneven capacity distribution and excessive current consumption by bypass circuits.
Innovation Solution
A charge-discharge control circuit that includes a cell balance detection circuit, memory to store the cell reaching a predetermined voltage first, and bypass circuits with switch units controlled by the circuit to maintain the ON/OFF status from the end of one charging operation to the start of the next, ensuring that only the cell with the lowest voltage in the previous cycle has its charge current reduced in the subsequent charging operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bypass circuits are activated to reduce voltage difference between cells, then cell balance is improved, but charge current is excessively reduced leading to lower charging efficiency
Solution Approach 1:
The bypass circuit switch is controlled dynamically based on real-time voltage detection. The control circuit activates the bypass circuit only when the voltage difference between cells exceeds a predetermined threshold, and deactivates it when the voltage difference is within the threshold. This dynamic control allows the system to maintain cell balance when needed while preserving charging efficiency when cell voltage is balanced.
Solution Approach 2:
The system changes the operational state (ON/OFF) of the bypass circuit based on voltage difference parameters. By monitoring the voltage difference parameter and adjusting the bypass circuit state accordingly, the system optimizes the balance between cell balance maintenance and charging efficiency.
2Reliability
If bypass circuit is activated continuously to maintain cell balance, then voltage difference between cells is reduced, but current consumption increases
Solution Approach 1:
The bypass circuit is activated periodically or intermittently based on voltage detection results rather than continuously. The control circuit repeatedly detects the voltage difference and activates the bypass circuit only during periods when the voltage difference exceeds the threshold, thereby reducing unnecessary current consumption while maintaining cell balance.
3Reliability
If charge terminate voltage is set low to prevent overcharge, then cell safety is improved, but charging capacity is reduced
Solution Approach 1:
The bypass circuit is activated in advance when the voltage difference between cells approaches the threshold, before any cell reaches the charge terminate voltage. This preliminary action prevents voltage imbalance from developing further, allowing the system to maintain higher charge terminate voltages for increased capacity while still ensuring cell safety through proactive balance management.
Data Source
AI summary
A charge-discharge control circuit includes a cell balance detection circuit that detects that a voltage of a cell reaches a predetermined voltage; a memory circuit that stores the cell that reaches the predetermined voltage first among plural of the cells; bypass circuits respectively connected to the plural cells in parallel, each of the bypass circuits including a switch unit for bypassing the current that flows through the corresponding cell when charging; and a control circuit that controls the switch units, wherein the control circuit controls the switch unit based on the cell stored in the memory circuit so that an ON/OFF status of the switch unit is maintained from a start to an end of a next charging operation subsequent to a charging operation during which the cell is stored in the memory circuit.