Charging Termination Control Module for Li-Ion Battery Precision
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Solution Overview
Problem
Existing battery charger circuits lack precision in determining when Li-ion or Li-polymer batteries are fully charged, leading to inefficient charging termination.
Innovation Solution
A charging termination control module comprising a charging current sense circuit, a charging termination determination circuit, and a charging termination tuning circuit, which detects the charging current, compares it with a threshold, and adjusts the charging control transistor to operate in its saturation region to maintain a predetermined voltage drop, thereby improving precision and allowing for a lower charging termination current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional charging termination control is used, then the charging circuit is simple, but the precision of charging termination determination is low
Solution Approach 1:
The charging control circuit is segmented into three functional modules: a charging current sense circuit to detect charging current, a charging termination determination circuit to compare current with threshold, and a charging termination tuning circuit to adjust transistor operation. This segmentation allows each module to perform a specific function with high precision while keeping the overall system manageable through modular design.
Solution Approach 2:
The charging termination tuning circuit implements feedback control by continuously monitoring the voltage drop across the charging control transistor and adjusting its operation to maintain optimal conditions. The circuit uses the detected charging current as feedback to dynamically adjust the transistor's operating point, ensuring precise charging termination determination while compensating for variations in battery characteristics.
2Measurement precision
If the charging termination current is set high, then the charging circuit is easier to detect, but the battery cannot be fully charged
Solution Approach 1:
The charging termination tuning circuit performs preliminary action by proactively adjusting the charging control transistor to operate in its saturation region before the charging current becomes too low to detect accurately. This advance adjustment ensures that the voltage drop across the transistor remains sufficient for detection even when the charging current approaches zero, enabling the system to detect very low termination currents (closer to zero) while maintaining reliable detection capability.
Solution Approach 2:
The circuit dynamically changes the operating parameters of the charging control transistor, specifically transitioning it to saturation region operation where the voltage drop becomes relatively independent of the charging current. This parameter change allows the system to maintain a detectable voltage signal even when the charging current is extremely low, thereby enabling accurate detection of charging termination currents closer to zero without sacrificing detection reliability.
Data Source
AI summary
A charging termination control module and a battery charger circuit comprising the same. The charging termination control module may detect/monitor/sense a charging current flowing through a charging control transistor of the battery charger circuit to provide a current sense signal, and to maintain a transistor voltage drop across the charging control transistor at a predetermined difference value once the transistor voltage drop reaches the predetermined difference value. The charging termination control module may also turn the charging control transistor off once the current sense signal is decreased to reach or to be lower than a charging termination threshold.