This short article describes the power supply loops in a PDB for Huawei SG7000. 

Each SG7000 cabinet is powered by two -48 VDC power supplies. The power supply for the parts in the cabinet is controlled by the PDB at the top of the cabinet.

The power supply of the PDB is as shown in Figure 1(DPD100-2-6) or Figure 2(DPD100-2-20).

Figure 1 Power supply of the PDB(DPD100-2-6)
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Figure 2 Power supply of the PDB(DPD100-2-20)
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To increase the reliability of the power supplies in the cabinet, the PDB uses a large power diode to combine the two input power supplies into one. Then the power supply is exported to the six switches on the panel of the PDB through one power bus cable. These switches help to supply the power for the parts in the cabinet through a power distribution system. In this way, when one input power supply fails, the other can power the parts in the cabinet through the PDB.

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