Laptop Charging System Inrush Limiter Control
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Solution Overview
Problem
Charging multiple laptops simultaneously poses challenges due to high initial current inrush, which can trip branch circuit protection and cause excessive wear on switches, limiting the number of laptops that can be charged at once.
Innovation Solution
A control system with current limiters and switches, such as triacs, is used to manage the power supply, allowing a low impedance path initially to minimize inrush and then decoupling to allow the current limiters to cool, enabling simultaneous charging of multiple laptops without tripping upstream protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple laptops are charged simultaneously, then charging productivity is improved, but current inrush causes branch circuit protection to trip
Solution Approach 1:
The system performs preliminary sequencing of power supply activation. Instead of simultaneously energizing multiple power supplies, the controller activates them in a predetermined sequence with time delays between each activation. This preliminary staged approach prevents simultaneous current inrush that would trip circuit protection, while ultimately achieving the goal of charging multiple laptops.
Solution Approach 2:
The system employs periodic activation of power supplies rather than continuous simultaneous operation. Each power supply is activated for a specific duration, then deactivated or held in standby, allowing the system to cycle through multiple power supplies periodically. This periodic action distributes the current demand over time, preventing circuit overload while maintaining charging productivity.
2Productivity
If multiple laptops are charged simultaneously, then charging efficiency is improved, but switch contacts experience excessive wear and welding
Solution Approach 1:
The controller implements preliminary control over switch activation timing. Before allowing full power flow through switch contacts, the system activates power supplies in a controlled sequence, ensuring that switch contacts are not subjected to simultaneous high-current transitions from multiple power supplies. This preliminary timing control reduces mechanical and thermal stress on contacts.
Solution Approach 2:
The system dynamically adjusts the activation and deactivation timing of individual power supply switches based on system state. Rather than using fixed simultaneous switching, the controller dynamically staggers switch operations, adapting the timing to current conditions. This dynamic approach minimizes peak current through any single switch contact, reducing wear and welding risk while maintaining overall charging efficiency.
3Device complexity
If power supplies are activated simultaneously, then system simplicity is maintained, but current inrush increases and trips protection
Solution Approach 1:
The controller segments the power supply activation process into distinct time-staggered stages. Instead of a single simultaneous activation event, the system divides the activation of multiple power supplies into separate sequential events, with each power supply receiving activation signals at different times. This segmentation of the activation process reduces peak current inrush while adding controlled complexity to the power management system.
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
This solution allows for the simultaneous charging of multiple laptops without tripping branch circuit protection and reduces wear on switches, enabling efficient and secure charging of a large number of devices.
Implementation Method 1
Each of the receptacle banks may be coupled to the AC source via a current limiter. The current limiters may have an impedance that initially limits an initial current inrush
Implementation Method 2
A switch may be provided in parallel with the current limiter. The switch may initially have a high impedance that prevents the switch from providing a low impedance path
Implementation Method 3
The controller may be configured to determine when the current limiter has cooled and to couple the current limiter back into the circuit. A temperature sensor may be coupled to the current limiter
Implementation Method 4
Feedback may be provided to the controller via an opto-isolator
Data Source
AI summary
A control system of a laptop computer storage system comprises a plurality of receptacles for charging one or more laptop computer batteries. A first switch may be provided for coupling the receptacles to a power source via a current limiter having an impedance that initially limits a current inrush and then decreases with temperature. A second switch may be provided for coupling the receptacles to the power source via a low impedance path. A controller may be provided and configured to activate the first switch to limit an initial current inrush while charging energy storing components associated with the laptop computer's power supply and then activate the second switch to allow each laptop coupled to the receptacles to at least partially charge its battery.