AN2929 datasheet(18/32 Pages) STMICROELECTRONICS

18 / 32 page

Testing the board

AN2929

18/32

Doc ID 15333 Rev 2

The performance of the VIPER27LN board is much better than required. The power

consumption is about twelve times lower than the ENERGY STAR® limit. Even if the results

seem to be disproportionally better than the requirements, it is worth mentioning that often

AC-DC adapter or battery charger manufacturers have very strict requirements concerning

no-load consumption and if the converter is used as an auxiliary power supply, the line filter

of the entire power supply is much bigger and considerably increases the standby

consumption.

Even if the ENERGY STAR® program does not have other requirements regarding light-load

performance, in order to give complete information we have provided the input power and

efficiency of the demonstration board in two other low-load cases also. Table 14 and

Table 15 show the performances when the output load is 25 mW and 50 mW respectively.

The input power and the average switching frequency versus the input voltage for different

load conditions are shown in the following figures.

Table 14.

Low-load performance POUT = 25 mW

VIN_AC

POUT (mW)

PIN (mW)

Eff. (%)

PIN-POUT

(mW)

fSW_AVG (kHz)

25.760

53.22

22.640

2.017

115

26.760

54.95

21.940

1.886

230

25.760

41.95

35.640

1.461

265

25.760

38.74

40.740

1.355

Table 15.

Low-load performance POUT = 50 mW

VIN_AC

POUT (mW)

PIN (mW)

Eff. (%)

PIN-POUT (mW)

fSW_AVG (kHz)

51.510

64.39

28.490

3.407

115

51.510

62.82

30.490

3.177

230

51.510

52.56

46.490

2.435

265

51.510

104

49.53

52.490

2.284

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