Battery Pack Switch Control to Limit Capacitor Inrush Current Damage
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Solution Overview
Problem
Battery packs used in power tools and vacuum cleaners face damage due to high inrush currents when connecting to capacitors, leading to protection device failure and inefficient start-up times.
Innovation Solution
A battery pack design incorporating a battery manager that outputs pulse width modulation signals to control discharge current, limiting inrush currents through a second switch, and gradually reducing duty cycles to manage capacitor charging efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a high capacity capacitor is provided at opposite ends of the battery pack to stably drive the motor, then the motor stability is improved, but a large inrush current is generated when the capacitor and battery pack are electrically connected, causing damage to the protection device
Solution Approach 1:
The battery manager performs preliminary action by detecting the connection state of the external load before full power delivery, and pre-controlling the second switch to limit inrush current. This preliminary detection and control prevents the harmful inrush current from damaging the protection device while still enabling stable motor operation.
Solution Approach 2:
The second switch acts as an intermediary component between the battery and the capacitor/load circuit. By controlling the second switch's on/off state, the battery manager mediates the inrush current flow, limiting it to safe levels while still allowing sufficient current for capacitor charging and motor operation.
2Reliability
If the second switch is controlled to limit inrush current, then the protection device is protected from damage, but the charging time of the capacitor increases, leading to longer start-up delay
Solution Approach 1:
The battery manager dynamically adjusts the control strategy based on the charging state of the capacitor. Initially, the second switch is controlled to limit inrush current for protection. As the capacitor charges and voltage increases, the battery manager gradually relaxes the limitation, allowing faster charging current to reduce start-up delay. This dynamic adjustment optimizes both protection and speed.
Solution Approach 2:
The battery manager implements periodic monitoring of the capacitor voltage and adjusts the second switch control accordingly. By periodically checking the charging state and adjusting the current limitation, the system balances protection requirements with the need for quick start-up, reducing overall delay while maintaining device safety.
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
The solution effectively reduces inrush currents, preventing protection device damage and minimizing start-up delays, ensuring stable power supply and efficient operation of external loads.
Implementation Method 1
a second switch configured to open or close according to a second control signal, and to open the first switch that is turned on by the first control signal, by a voltage of the first pack terminal or the second pack terminal
Implementation Method 2
A battery pack design incorporating a battery manager that outputs pulse width modulation signals to control discharge current, limiting inrush currents through a second switch
Data Source
AI summary
A battery pack includes a battery including at least one battery cell, a terminal portion electrically connected to the battery and including a first pack terminal connected to an external load and a second pack terminal, a first switch configured to switch a discharge current of the battery according to a first control signal, a second switch configured to open or close according to a second control signal, and to open the first switch that is turned on by the first control signal, by a voltage of the first pack terminal or the second pack terminal, and a battery manager configured to output the first control signal and the second control signal.