AN2393 datasheet(9/35 Pages) STMICROELECTRONICS

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AN2393

Electrical test results

9/35

Electrical test results

2.1

Efficiency measurements

Table 1 and Table 2 show the output voltage measurements at the nominal mains voltages

of 115 Vac and 230 Vac, with different load conditions. For all measurements, both at full load

and at light load operation, the input power is measured using a Yokogawa WT-210 digital

power meter.

Particular attention has to be paid when measuring input power at full load in order to avoid

measurement errors due to the voltage drop on cables and connections. Therefore please

connect the WT210 voltmeter termination to the board input connector. For the same reason

please measure the output voltage at the output connector or use the remote sense option

of your active load for a correct output voltage measurement.

In Table 1, Table 2 and Figure 5 the overall circuit efficiency is measured at each load

condition, at both nominal input mains voltages of 115 Vac and 230 Vac. The values were

measured after 30 minutes of warm-up at maximum load. The high efficiency of the PFC

pre-regulator working in FOT mode and the very high efficiency of the resonant stage

working in ZVS (i.e. with negligible switching losses), provides for an overall efficiency better

than 88%. This is a significant high value for a two-stage converter with two output voltages

delivering an output current in excess of 5 amps, especially at low input mains voltage

where the PFC conduction losses increase. Even at lower loads, the efficiency still remains

high.

The global efficiency at full load has been measured even at the limits of the input voltage

range, with good results:

●

At VIN = 90 Vac - full load, the efficiency is 86.88% (POUT = 208.8 W and PIN = 240.3 W)

●

At VIN = 264 Vac - full load, the efficiency is 90.90% (POUT = 208.7 W and PIN =

229.6 W)

Table 1.

Efficiency measurements @VIN = 115 Vac

+24 V(V) @load(A) +12 V(V) @load(A) +5 V(V) @load(A) +3.3 V(V) @load(A) POUT (W) PIN (W) Efficiency

23.81 - 6.00

11.86 - 4.94

4.93 - 0.98

3.35 - 0.71

208.66

235.00

88.79%

24.04 - 3.04

11.80 - 4.91

4.93 - 0.98

3.35 - 0.71

138.23

155.50

88.89%

23.84 - 3.02

11.91 - 1.98

4.93 - 0.98

3.35 - 0.71

102.79

115.47

89.02%

23.79 - 2.01

11.96 - 0.49

4.96 - 0.31

3.35 - 0.31

56.25

63.55

88.52%

23.94 - 0.53

11.92 - 0.49

4.97 - 0.31

3.35 - 0.31

21.11

25.56

82.58%

Table 2.

Efficiency measurements @VIN = 230 Vac

+24 V(V) @load(A) +12 V(V) @load(A) +5 V(V) @load(A) +3.3 V(V) @load(A) POUT (W) PIN (W) Efficiency

23.82 - 6.00

11.86 - 4.94

4.94 - 0.98

3.35 - 0.71

208.73

229.96

90.77%

24.05 - 3.04

11.80 - 4.91

4.94 - 0.98

3.35 - 0.71

138.27

152.85

90.46%

23.85 - 3.02

11.91 - 1.98

4.94 - 0.98

3.35 - 0.71

102.83

114.05

90.16%

23.80 - 2.01

11.96 - 0.49

4.96 - 0.31

3.35 - 0.31

56.27

63.47

88.66%

23.94 - 0.53

11.92 - 0.49

4.96 - 0.31

3.35 - 0.31

21.11

26.47

79.73%

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