AN2435

Board description and bench evaluation results

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4.2

Bench results

The diagrams in this section summarize the results of certain bench evaluations. They also

show waveforms under different load and line conditions.

Figure 14 illustrates the measured efficiency for different loads (65 W, 38 W and 22 W of

output power) versus the input ac voltage.

Figure 15 demonstrates the MOSFET drain voltage (Ch4), the output voltage (Ch3) and the

input voltage.

The quantities that indicate the quality of the input current as power factor, THD (Total

Harmonic Distortion) and crest factor, where measured at full load and for different input

voltages. They are reported in Table 3.

L2 current) for different load conditions. Letting the input voltage of the converter (the

rectified main) be a perfect rectified sinusoid, it may be used as a reference and is shown as

Ch4 in the above figures.

Figure 20 illustrates the input current (Ch1) measured before the input bridge diodes. The

voltage at the input of the bridge diodes (Ch4) is also shown as a reference.

Figure 14.

Efficiency chart

Table 3.

Input current quality measurements

PFC

THD %

Crest factor

175

0.992

10.3

1.35

220

0.986

12.3

1.36

230

0.984

12.6

1.37

265

0.975

14.2

1.46