Rev 1.5

vicorpower.com

Page 6 of 15

08/2015

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QPI-21

Figure 6 — Ericsson PKM 4402NG using open-frame “Y” capacitors on

QPI-21-CB1 evaluation board, 414 W load

Figure 8 — Ericsson PKM4304B PI using base-plate “Y” capacitors

with a 360 W load

Figure 7 — Ericsson PKM 4402NG using open-frame “Y” capacitors on

QPI-21-CB1 evaluation board, 414 W load, converter’s output

ground connected to earth

Figure 9 — Ericsson PKM4304B PI using base-plate “Y” capacitors

with a 360 W load, CX1 = 47uF (see Figure 2).

The EMI results shown in Figures 6 and 7 are of the total noise

measured using the QPI-21 in an "open-frame" topology, as shown

in Figure 5, with and without the converter's ground tied to

chassis/earth.

The EMI results shown in Figures 8 and 9 are of the total noise

measured using the QPI-21 in an "base-plate" topology, as shown in

Figure 2, with and without the optional CX1 capacitor in use.

Using EMI splitters, the peak EMI at the fundamental switching

frequency was determined to be mostly differential mode current.

The addition of a 47 μF capacitor reduced the total peak by about

6dBuV, as shown in Figure 10.

Figure 10 — CM Peak Measurements with a 10 µF and 47 µF

CX1 capacitor