EMI Shielded Bus Bar Configuration for Modular Packet Switches
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Solution Overview
Problem
The existing modular packet switch/router designs face challenges in scaling due to thick copper power planes, which complicate dielectric filling, increase board thickness, and lead to inefficiencies in cooling and redundancy, particularly with DC/DC power converters being placed after logic components, leading to potential shutdowns and difficult maintenance.
Innovation Solution
A novel power distribution design where power conversion cards are placed behind the backplane, generating logic voltages, eliminating the need for thick power planes on line cards, allowing for separate cooling and easier replacement, and implementing sharing mechanisms for redundancy and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If thick copper power planes are used to distribute primary power, then power distribution capability is improved, but board thickness increases and dielectric filling becomes complicated
Solution Approach 1:
The invention divides the power distribution function into two separate components: thick copper power planes in the backplane for high-current distribution, and thin power planes on line cards for local voltage distribution. This segmentation allows the backplane to handle bulk power transmission while line cards perform local power conversion, eliminating the need for thick power planes on line cards and reducing overall board thickness.
Solution Approach 2:
The invention transitions from a two-dimensional planar power distribution approach to a three-dimensional hierarchical approach, where power is distributed vertically through the backplane thickness and then horizontally across line cards. This dimensional change enables efficient power delivery without requiring uniformly thick power planes across all boards.
2Device complexity
If DC/DC power converters are placed after logic components in the cooling airflow path, then board layout flexibility is improved, but cooling efficiency deteriorates and shutdown risk increases
Solution Approach 1:
The invention inverts the conventional cooling approach by placing DC/DC power converters in the coolest region of the chassis (at the air intake end) rather than at the exhaust end. This inversion ensures that power converters receive the coolest air first, preventing thermal shutdowns while maintaining board layout flexibility through the modular backplane design.
3Adaptability or versatility
If power conversion cards are integrated with line cards, then device integration is improved, but maintenance difficulty and redundancy complexity increase
Solution Approach 1:
The invention segments the power conversion function into a separate, standalone power conversion card that interfaces with the backplane, rather than integrating it permanently into line cards. This segmentation allows power conversion cards to be independently replaced and maintained, simplifying repair operations while maintaining system integration through the standardized backplane connection.
Solution Approach 2:
The invention creates a universal power conversion card design that can serve multiple line cards through the backplane interface. This universal card performs the same power conversion function for different line card types, providing redundancy and ease of replacement without requiring line-card-specific power conversion circuits.
Data Source
AI summary
A modular packet network device uses bus bars to transfer primary power to either a backplane or directly to one or more cards that perform primary-to-logic-power conversion. The bus bars are fabricated in packages that reduce the transfer of differential and common-mode noise existing in the device chassis into the power delivery system through the bus bars. Other embodiments are also described and claimed.