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QPI-10-CB1 Datasheet(PDF) 4 Page - Vicor Corporation |
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QPI-10-CB1 Datasheet(HTML) 4 Page - Vicor Corporation |
4 / 7 page Picor Corporation • www.picorpower.com QPI-10-CB1 Data Sheet Rev. 1.1 Page 4 of 7 EMI Bypass Configurations EMI bypass capacitors (“Y” capacitors) are an essential element in a switch-mode DC-DC filter application as these capacitors provide a return path for common- mode noise currents to their source; so careful attention to bypass capacitor implementation is essential for a successful EMI filter design. This carrier board is preconfigured in a “base-plate” EMI topology, which uses six “Y” capacitors (only four are actually used in a BCM configuration), as illustrated in Figure 7 below. This is the preferred topology for VI Chip applications. The carrier board can be manually reconfigured to an “open frame” topology, which uses four “Y” caps in a PRM/VTM combination (two for a BCM), as shown in Figure 8. The open-frame approach may attenuate certain load dependent noise better than the base-plate method. The carrier board provides an ideal test vehicle for making a comparison between the two “Y” capacitor configurations. To reconfigure to “open frame” carefully remove capacitors CY5 through CY10 and place four of those six capacitors in the positions marked as CY1 through CY4. EMI Performance and Test Set Up The EMI plots in Figures 9 through 14 are the total noise measurements, on both the positive and negative lines of the QPI-10LZ with various VI Chip configurations, BUS+ QPI+ BUS- QPI- QPI VIN+ VOUT+ VIN- VOUT- PRM VIN+ VOUT+ VIN- VOUT- VTM CY5 CY6 CY9 CY7 CY10 CY8 C1 47 uF LISN LISN PCB Plane Under Converter ~1.25 m Shielded Box Shield Plane (Earth Ground) PCB Board BUS SUPPLY SW Figure 7 – Basic EMI measurement setup for “base-plate” configuration. BUS+ QPI+ BUS- QPI- QPI VIN+ VOUT+ VIN- VOUT- PRM VIN+ VOUT+ VIN- VOUT- VTM CY3 CY1 CY4 CY2 C1 47 uF LISN LISN PCB Plane Under Converter ~1.25 m Shielded Box Shield Plane (Earth Ground) PCB Board BUS SUPPLY SW Figure 8 – Basic EMI measurement setup for “open-frame” configuration. using the basic base-plate standard “Y” cap configuration. Figure 7 shows the basic EMI measurement set up that was used to achieve these results. Figure 8 shows the alternate set up method when converting to the open-frame approach. In Figure 7 (base-plate method), capacitors CY5 through CY10 represent the recirculation capacitors that are connected to each of the four input and output terminals, then are commoned to a shield plane that has been created underneath the converter. Since the PRM/ VTM pair is similar to a conventional converter, which is split into to halves, two additional “Y” caps (CY7 and CY9) were added to the PRM’s output (the input to the VTM), referenced to the shield plane. In Figure 8 (open-frame method), four “Y” capacitors are used (CY1 through CY4) rather than the two “Y” caps that a conventional converter would require, once again because of the topology split created by the pair. In a BCM application there is no topology split so the set up would require two fewer capacitors for either configuration. The open-frame method would only need one pair of input an output caps, referenced to the shield plane on either side of the BCM. And for open-frame method a pair of “Y” caps across the positive input to positive output, and negative input and negative output would be sufficient. |
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Similar Description - QPI-10-CB1 |
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