EMI shielded bus bar configuration
View Patent ↗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.
1. A modular packet network device comprising:
a chassis having a power zone, a signaling zone, and a logic zone; and
a first bus bar assembly to transfer a primary power from the power zone to the signaling zone and logic zone, the first bus bar assembly having
first and second conductive members, each having a cross-section over a majority of its length with a minimum width-to-height ratio of 3:1 and at least one substantially flat side along the width direction, the at least one substantially flat side of the first conductive member facing the at least one substantially flat side of the second conductive member over a majority of the lengths of the first conductive member and the second conductive member,
an electrically insulating layer interposed between the flat facing sides of the first conductive member and the second conductive member
a power card connector coupled to the first and second conductive members and operable to couple to a power card on a first side of the first bus bar assembly; and
a signaling card connector coupled to the first and second conductive members and operable to couple to a signaling card on a second side of the first bus bar assembly that is opposite the first side.
2. The modular packet network device of claim 1 , wherein the electrically insulating layer is selected from the group of insulating devices consisting of an H-shaped plastic extrusion holding both conductive members in insulative separation, a thermoplastic dip layer formed around both conductive members, a scrim cloth material wrapped around each of the conductive members, a thermoplastic dip layer formed around at least one of the conductive members, a thermo-set cloth material, a heat-shrunk tubing lined with hot-melt adhesive, and combinations thereof.
3. The modular packet network device of claim 1 , wherein the insulating layer substantially covers both conductive members in regions where the substantially flat sides of the conductive members face each other.
4. The modular packet network device of claim 3 , further comprising an electrically conductive shielding material surrounding a section of the insulated conductive members, the electrically conductive shielding material tied to chassis ground in proximity to the signaling zone and the logic zone.
5. The modular packet network device of claim 4 , wherein the electrically conductive shielding material is selected from the group of electrically conductive shielding materials consisting of a wire mesh tube slid over the insulated conductive members, foil applied to the insulated conductive members, metallized tape applied to the insulated conductive members, a metal coating applied to the insulated conductive members, a metal mesh sheet cut to shape and wrapped around the insulated conductive members, and combinations thereof.
6. The modular packet network device of claim 4 , further comprising an insulating layer formed over the shielding material.
7. The modular packet network device of claim 1 , further comprising at least one ferrite choke surrounding the conductive members.
8. The modular packet network device of claim 1 , wherein in at a position along the conductive members, the conductive members separate to provide a separation, and a first ferrite choke surrounds the first conductive members at the separation.
9. The modular packet network device of claim 8 , further comprising a second ferrite choke surrounding the second conductive member at the separation.
10. The modular packet network device of claim 1 , wherein in at a position along the conductive members, the width of the facing sides of the first and second conductive members substantially increases.
11. The modular packet network device of claim 1 , further comprising a backplane mounted in the signaling zone and the logic zone, wherein the two conductive members separate and connect to the backplane.
12. The modular packet network device of claim 11 , wherein the backplane contains conductive layers dedicated to the delivery of the primary power to a plurality of logic cards and other conductive layers dedicated to electrical signaling between the plurality of logic cards.
13. The modular packet network device of claim 11 , wherein the backplane is dedicated to the distribution of the primary power to modules in the signaling zone and the logic zone.
14. The modular packet network device of claim 1 , further comprising a backplane mounted in the signaling zone and the logic zone and having card region corresponding to a plurality of card slots including a power card slot, the bus bar assembly running along an edge of the backplane perpendicular to the power card slot, the power card connector aligned respectively with the power card slot to deliver the primary power to the power card slot.
15. The modular packet network device of claim 14 , wherein the plurality of card slots include a signaling card slot, the signaling card connector aligned respectively with the signaling card slot to deliver the primary power to the signaling card slot.
16. The modular packet network device of claim 15 , wherein at least some of the plurality of connectors have a connection face on the front of the bus bar assembly and others of the plurality of connectors have a connection face on the back of the bus bar assembly.
17. The modular packet network device of claim 14 , wherein the flat facing sides of the first conductive member and the second conductive member are substantially parallel to the backplane such that first conductive members lies behind the second conductive member, at least one of the power card connector and the signaling card connector making electrical connection to the first conductive member through a hole in the second conductive member.
18. The modular packet network device of claim 14 , wherein the flat facing sides of the first conductive member and the second conductive member are substantially parallel to the backplane such that first conductive members lies behind the second conductive member, at least one of the power card connector and the signaling card connector making electrical connection to the first conductive member through a tab of the first conductive member that extends beyond an edge of the second conductive member.
19. The modular packet network device of claim 14 , further comprising first and second power supplies secured in the power zone, the first bus bar assembly delivering supply and return power to the signaling zone and the logic zone from the first power supply, and further comprising a second bus bar assembly delivering supply and return power to the signaling zone and the logic zone from the second power supply, the second bus bar assembly substantially similar in construction to first bus bar assembly and also running along the same edge of the backplane as the first bus bar assembly, between the backplane and the first bus bar assembly, the first and second bus bar assemblies delivering a redundant power to each of the subset of card slots.