Battery Protection IC Prevents Overdischarge Current Leakage
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Solution Overview
Problem
Conventional rechargeable battery protection circuits allow a small current to continue flowing when the load is not removed, leading to inefficiencies and potential damage during overdischarge states due to the design of the load detection mechanism.
Innovation Solution
The proposed solution involves a rechargeable battery protection integrated circuit that includes a discharge control transistor and a control circuit to manage the flow of current by pulling down the monitor terminal's potential to ground when overdischarge is detected, and then cancels this pull-down if the load is not removed within a predetermined time, thereby preventing unnecessary current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Difficulty of detecting and measuring
If a pull-down resistor is used to detect load removal by pulling down the monitor terminal potential, then load detection capability is improved, but a small current continues to flow through the battery even when the load is connected, causing energy loss
Solution Approach 1:
The control circuit performs preliminary action by turning off the discharge control transistor before the battery is fully discharged. When the control circuit detects that the battery voltage has dropped below a predetermined threshold voltage, it turns off the discharge control transistor in advance to prevent overdischarge and the associated energy loss, while still maintaining the ability to detect load removal through the pull-down resistor mechanism.
2Reliability
If the discharge control transistor is turned off to prevent overdischarge, then battery protection is improved, but the ability to detect load removal becomes unreliable if the pull-down remains active for extended periods
Solution Approach 1:
The control circuit implements dynamics by making the pull-down resistor connection conditional and time-dependent. After turning off the discharge control transistor to protect the battery, the control circuit maintains the pull-down connection only for a predetermined time period to detect load removal. If load removal is not detected within this time, the control circuit cancels the pull-down connection to prevent interference with subsequent operation, thus adapting the detection mechanism to the current operational state.
Data Source
AI summary
A battery protection circuit protects a rechargeable battery from overdischarge, by turning off a transistor inserted in series in a current path between a negative electrode of the battery and a negative terminal coupled to ground of a load or a charger. A detection circuit detects a power source voltage between power source and ground terminals, and a control circuit pulls down a monitor terminal potential to a ground terminal potential by turning off the transistor and stopping battery discharge when the power source voltage lower than an overdischarge detection voltage is detected. The control circuit cancels pull-down of the monitor terminal potential to the ground terminal potential when the power source voltage higher than an overdischarge reset voltage is not detected until a predetermined time elapses in a state in which the battery discharge is stopped and the monitor terminal potential is pulled down to the ground terminal potential.