AN3276 datasheet(16/22 Pages) STMICROELECTRONICS

16 / 22 page

BC2 design in 450 W PFC

AN3276

16/22

Doc ID 17975 Rev 1

3.3

Efficiency comparison

BC2 and SiC diode efficiency have been compared under two Vmains levels as shown in

Figure 15 (230 VRMS) and Figure 16 (90 VRMS) with a switching frequency equal to

140kHz. At 230VRMS, the BC

2 circuit saves up to 2.25 W at full load and 1 W at 100 W

compared to the 8 A SiC diode. Under low load, the reflected voltage from NS2 still improves

the BC2 efficiency because the switch-off losses are lower than the SiC as described in the

phase time [t0-t1]. As soon as the PFC works in discontinuous mode (< 100 W) the SiC and

the BC2 have the same efficiency as shown in Figure 15.

Figure 15.

Efficiency comparison at 230 V rms

At 90 V rms, the soft switching method benefits plus the power saving in the COSS discharge

reinforces the benefit of the BC2 circuit. Up to 5.4 W is saved thanks to the BC2 at 450 W

compared to the SiC diode and under low load, up to 1.7% is saved thanks to the switch-off

power saving.

100

150

200

250

300

350

400

450

OUT

² solution

8A SIC

Continuous mode

Discontinuous mode

SiC

BC²

+1%

+0.7%

+0.5%

Fs = 140 kHz

Efficiency = f(P

)

OUT

= 230 V

mains

RMS

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