Transformer-less Battery Charger Safety via Switch Actuation
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Solution Overview
Problem
Transformer-based battery charger systems are bulky, expensive, and pose safety hazards due to the lack of isolation in non-isolated DC-DC converters, which can lead to electric shocks when users inadvertently contact the output terminals.
Innovation Solution
A transformer-less battery charger system utilizing a non-isolated DC-DC converter with safety mechanisms such as housing design and switch actuation to prevent user contact, and an MCU-controlled PWM signal for the three-stage charging process, ensuring safe and efficient charging without the need for transformers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a transformer-based battery charger system is used, then electrical isolation and safety are improved, but the device size, weight, and cost increase
Solution Approach 1:
The patent removes the transformer component from the battery charger system entirely, transitioning from a transformer-based isolated design to a transformer-less non-isolated design. This extraction eliminates the heavy transformer while implementing alternative safety mechanisms through housing design and switch actuation systems that detect battery presence to prevent electric shock hazards.
2Reliability
If a transformer-based battery charger system is used, then electrical isolation and safety are improved, but the device size and cost increase
Solution Approach 1:
The transformer component is completely removed from the system, eliminating its physical footprint and associated cost. The patent compensates for the lost electrical isolation function through a combination of insulating housing design and intelligent switch control that activates only when a battery is properly inserted, thereby maintaining safety while reducing size.
3Device complexity
If a non-isolated DC-DC converter is used without safety mechanisms, then device complexity is reduced, but electrical shock hazards increase
Solution Approach 1:
The patent introduces an intermediary detection system consisting of switches and control circuitry that mediates between the non-isolated DC-DC converter and the user-accessible output terminals. The switches remain open under normal conditions and only close when a battery is properly inserted, as detected by the control system. This intermediary mechanism enables the use of simpler non-isolated converters while preventing electric shock hazards through intelligent control.
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 transformer-less design reduces size, weight, and cost while providing safety features to prevent electric shocks, ensuring efficient and safe charging of lithium-ion battery packs.
Implementation Method 1
an MCU-controlled PWM signal for the three-stage charging process
Data Source
AI summary
A transformer less battery charger system. In one embodiment, the battery charger system includes input terminals for receiving an AC voltage, output terminals for receiving terminals of a rechargeable battery pack, and a non-isolated DC-DC converter coupled between the input terminals and the output terminals. A device is also coupled somewhere between the input terminals and the output terminals. The device is configured to selectively and indirectly couple the input terminals to the output terminals. More particularly, the device indirectly couples the input terminals to the output terminals when the rechargeable battery pack terminals are received by the output terminals, and the device indirectly decouples the input terminals from the output terminals when the rechargeable battery pack terminals are separated from the output terminals.