AN2950 datasheet(19/37 Pages) STMICROELECTRONICS

19 / 37 page

AN2950

Testing the board

Doc ID 15494 Rev 1

19/37

Even if the performance seems to be unproportionally better than the requirement, it is

worth noting that often AC-DC adapter or battery charger manufacturers have very strict

requirements about no load consumption, and if the converter is used as an auxiliary power

supply, the line filter is often the big line filter of the entire power supply that significantly

increases consumption in standby mode.

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

performance, in order to provide complete information we have also reported the input

power and efficiency of the demonstration board in two other low load cases. Table 15 and

Table 16 show the board’s performances when the output load is 25 mW and 50 mW

respectively.

Figure 24 reports the input power vs input voltage for no load and low load conditions.

Figure 24.

Pin vs VIN at low load

Table 15.

Low load performance - POUT = 25 mW

VIN_AC

POUT (mW)

PIN (mW)

Eff. (%)

PIN-POUT (mW)

45.5

54.94505

20.5

115

46.8

53.4188

21.8

150

47.7

52.4109

22.7

180

50.4

49.60317

25.4

230

45.45455

265

40.98361

Table 16.

Low load performance - POUT = 50 mW

VIN_AC

POUT (mW)

PIN (mW)

Eff. (%)

PIN-POUT (mW)

73.5

68.02721

23.5

115

76.6

65.27415

26.6

150

62.5

180

60.97561

230

59.52381

265

54.34783

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