AN2782 datasheet(33/39 Pages) STMICROELECTRONICS

33 / 39 page

AN2782

Test results and significant waveforms

Doc ID 14763 Rev 2

33/39

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

the results are illustrated in Figure 28, 29, 30, 31. 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 high mains range. THD is low, remaining within 30% at

maximum input voltage.

The efficiency 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 shown in

Figure 28

, 29, 30, 31. As shown, the voltage is perfectly stable over the entire input voltage

range. Just at 265Vac and light load, there are negligible deviations of 1 V due to the

intervention of the burst mode (for the “static OVP”) function.

Figure 28.

Power factor vs. Vin and load

Figure 29.

THD vs. Vin and load

0.70

0.75

0.80

0.85

0.90

0.95

1.00

1.05

130

180

230

280

Vin (Vac)

Pout =400W

Pout =200W

Pout =70W

130

180

230

280

Vin (Vac)

Pout =400W

Pout =200W

Pout =70W

Figure 30.

Efficiency vs. Vin and load

Figure 31.

Static Vout regulation vs. Vin and

load

100

130

180

230

280

Vin (Vac)

Pout =400W

Pout =200W

Pout =70 W

Pout =15W

397

398

399

400

401

402

403

404

130

180

230

280

Vin(Vac)

Pout =400W

Pout =200W

Pout =70W

Pout =15W

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