AN2994 datasheet(10/38 Pages) STMICROELECTRONICS

10 / 38 page

Test results and significant waveforms

AN2994

10/38

Doc ID 15796 Rev 2

The power factor (PF) and the total harmonic distortion (THD) have also been measured

and the results are reported in Figure 13 and Figure 14. As shown, the PF at full load and

half load remains close to unity throughout the input voltage mains range, while when the

circuit is delivering 70 W it decreases at a high mains range. THD is low, remaining within

20% at the maximum input voltage.

The converter’s efficiency reported in Figure 15 is very good at all load and line conditions.

At full load, it is always significantly higher than 90%, making this design suitable for high-

efficiency power supplies.

The measured output voltage variation at different line and load conditions is reported in

Figure 16. As shown, thanks to the voltage feed-forward function embedded in the L6563S,

the voltage is perfectly stable over the entire input voltage range. At 265 Vac and light load,

there is a negligible deviation of 1 V due to the intervention of the burst mode function.

Figure 11.

EVL6563S-400W input current

waveform at 100 V, 60 Hz, 70 W load

Figure 12.

EVL6563S-400W input current

waveform at 230 V, 50 Hz, 70 W load

CH1: Rectified mains voltage

CH4: Input current

Figure 13.

Power factor vs. Vin and load

Figure 14.

THD vs. Vin and load

0.75

0. 8

0.85

0. 9

0.95

100

115

130

180

230

265

Vin [ Vrms]

400W

200W

70W

100

115

130

180

230

265

Vin [Vrms ]

THD[% ]

400W

200W

70W

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