Dual Detection Circuit for Voltage Collapse Protection
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Solution Overview
Problem
Battery charging circuits face voltage collapse when the system current load exceeds a current-limited charger's capacity, leading to potential battery damage from unintentional charging when the load decreases, as existing detection methods may fail to accurately determine when charging should be terminated, especially for fully charged or temperature-sensitive batteries.
Innovation Solution
A battery charging circuit with dual detection circuits, one analog and one digital, to quickly sense current flow into the battery, ensuring voltage collapse protection (VCP) is terminated by detecting current reversals, preventing unintentional charging through a battery management system (BMS) that can re-purposed ADC circuitry for low-current detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single detection circuit is used to sense current flow into the battery, then the device complexity is reduced, but the detection precision and speed are insufficient to accurately determine when charging should be terminated
Solution Approach 1:
The detection function is segmented into two separate detection circuits: a first detection circuit with a higher current detection limit for detecting significant current flow, and a second detection circuit with a lower current detection limit for detecting small residual current flow. This segmentation allows each circuit to be optimized for its specific detection range, improving overall detection precision without requiring a single overly complex circuit to handle all current levels.
2Reliability
If the battery is connected to supplement the system load during voltage collapse, then the voltage collapse protection is activated, but current may inadvertently flow into the battery when the load decreases, causing unintentional charging
Solution Approach 1:
The system continuously monitors current flow direction through the battery using the two detection circuits. When the load decreases and current begins to flow into the battery, the detection circuits provide feedback signals that trigger the control circuit to disconnect the battery, preventing unintentional charging. This feedback mechanism ensures reliable VCP operation while protecting against harmful reverse current flow.
3Speed
If the first detection circuit has a higher current detection limit for faster response, then the voltage collapse detection speed is improved, but small currents after load reduction may not be detected, leading to delayed termination
Solution Approach 1:
The detection range is segmented between two circuits: the first detection circuit is optimized for high-current detection with faster response time to detect voltage collapse conditions, while the second detection circuit is optimized for low-current detection with higher sensitivity to detect small residual currents. This segmentation resolves the contradiction by assigning different detection tasks to specialized circuits rather than requiring a single circuit to excel at both.
Solution Approach 2:
The first detection circuit uses a higher current detection threshold that may not detect very small currents, but this is acceptable because the second detection circuit compensates for this limitation by detecting small residual currents. The excessive action of the first circuit (higher threshold) is balanced by the complementary action of the second circuit (lower threshold), ensuring both fast response and accurate small current detection.
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
Effectively prevents battery damage by rapidly terminating VCP when the load returns within charger capacity, ensuring safe and accurate end-of-charge detection, even for small currents, while maintaining efficiency and power considerations suitable for small devices.
Implementation Method 1
A first detection circuit may sense a voltage drop across a sense resistor as an indication of current flowing into the battery
Implementation Method 2
A second detection circuit may sense a voltage drop across a sense resistor as an indication of current flowing into the battery
Data Source
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AI summary
Disclosed is battery charging circuit having a first detection circuit and a second detection circuit for detecting when to terminate an activated voltage collapse protection operation. The first detection circuit may be an analog design and the second detection circuit may include digital circuitry.