Non-Common Ground Bus Protection via Switch Isolation
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Solution Overview
Problem
Existing non-common ground bus systems in battery packs face issues with undesired current flow and potential destruction of interface units due to floating grounds, leading to the need for costly and power-loss-inducing isolation technologies.
Innovation Solution
A protection device comprising a controller, level shifter, and switches that isolate the buses by generating control signals to manage the charging and discharging processes, ensuring that at least part of the switches are turned off to prevent current flow between the buses during abnormal conditions, thereby maintaining non-common ground bus isolation without significant power dissipation or increased cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If opto-coupler isolation technology is used to protect non-common ground buses, then bus protection reliability is improved, but power loss increases and cost increases
Solution Approach 1:
The patent extracts the ground connection function from the isolation requirement. By using switches to selectively connect or disconnect ground paths, the system achieves protection without needing opto-coupler isolation technology, thereby eliminating the associated power loss and cost penalties while maintaining bus protection reliability
Solution Approach 2:
The patent introduces switches as intermediary elements between the battery pack ground and the external device ground. These switches act as controllable mediators that can establish or break ground connections based on operational conditions, providing a more efficient alternative to opto-coupler isolation
2Reliability
If opto-coupler isolation technology is used to protect non-common ground buses, then bus protection reliability is improved, but device cost increases
Solution Approach 1:
The patent replaces expensive opto-coupler isolation components with inexpensive switch elements that can be easily manufactured and integrated. The switches provide the necessary protection function at a fraction of the cost of opto-coupler technology, making the battery pack application more economically viable
Solution Approach 2:
The patent removes the need for costly opto-coupler isolation technology by extracting the essential protection function and implementing it through simpler switch-based ground connection control, thereby reducing device cost while maintaining reliability
3Ease of operation
If ground connection is established for common ground bus, then communication simplicity is improved, but undesired current flow occurs when voltage difference exists
Solution Approach 1:
The patent transforms the static ground connection into a dynamic, controllable connection. The switches can be turned on or off based on voltage differences and operational modes, allowing the system to maintain simple communication when safe while blocking harmful current flow when voltage mismatches occur
Solution Approach 2:
The controller monitors voltage differences between the battery pack and external device, and based on this feedback, dynamically controls the switch states to prevent undesired current flow while maintaining communication functionality when conditions are safe
4Reliability
If switches are turned off to isolate buses during abnormal conditions, then bus protection is improved, but charging and discharging control complexity increases
Solution Approach 1:
The switches serve multiple functions: they control normal charging and discharging operations, provide bus protection during abnormal conditions, and manage ground connections. This multi-functionality reduces the need for separate protection circuits, actually simplifying the overall control architecture while improving protection reliability
Data Source
AI summary
A protection device for non-common ground buses is disclosed. The protection circuit includes a controller, a level shifter, a first group of switches, and a second group of switches. The controller together with the level shifter controls the first group and second group of switches. The non-common ground buses will be isolated when at least one group of the switches are turned off in an abnormal condition.