AN1842 APPLICATION NOTE

6/17

Standby operation

Like in the previous section, the output voltages and the efficiency have been checked, and the input pow-

er has been measured. It is clearly visible that with the required standby load (5V@30mA, 12V@0mA)

the input power consumption is well below 800mW at both the input voltage ranges. Besides, the cir-

cuit has been characterised at both the nominal input voltage values for different output load and the effi-

ciency is high in all conditions. In the fig. 8, it is shown the output voltage variation as a function of the 5V

current.

During the standby operation the circuit works at reduced frequency, according to load and input voltage

therefore, thanks to this function, the switching losses are minimized. This allows reaching very low stand-

by consumption because in a power switch the switching and the capacitive losses are directly proportion-

al to the working frequency.

5V ± 2%

12V ± 10%

TOLERANCE

230 Vac

Vout

[V]

@Iout

[A]

Vout

[V]

@Iout

[A]

[W]

Pin

[W]

Efficiency

Vaux

[V]

fs

[KHz]

5.106

2

12.09

4

OK

58.57

69.3

84.5%

17.7

51

5.107

2

12.23

3

OK

46.90

55.3

84.8%

17.3

51

5.109

2

12.40

2

OK

35.02

41.2

85.0%

16.9

51

5.110

2

12.74

1

OK

22.96

27.6

83.2%

16.6

51

5.110

2

13.12

0.5

OK

16.78

20.8

80.7%

16.6

51

5.108

1

11.85

4

OK

52.51

63.9

82.2%

17.5

51

5.108

1

12.00

3

OK

41.11

49.4

83.2%

16.7

51

5.110

1

12.15

2

OK

29.41

35.0

84.0%

16.2

51

5.112

1

12.39

1

OK

17.50

21.0

83.3%

15.9

51

5.112

1

12.66

0.5

OK

11.44

14.0

81.7%

15.9

51

5V

115 Vac

Vout [V]

@Iout [mA]

Pin [W]

Efficiency

5.11

20

0.102

0.433

23.6%

5.11

30

0.153

0.515

29.8%

5.11

40

0.204

0.593

34.5%

5.11

50

0.256

0.667

38.3%

5.11

60

0.307

0.745

41.1%

5.11

80

0.409

0.881

46.4%

5.11

100

0.511

1.021

50.1%

5V

230Vac

5.11

20

0.102

0.493

20.7%

5.11

30

0.153

0.582

26.3%

5.11

40

0.204

0.672

30.4%

5.11

50

0.256

0.755

33.8%

5.11

60

0.307

0.842

36.4%

5.11

80

0.409

1.008

40.6%

5.11

100

0.511

1.168

43.8%