AN2521

Test results

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400 V input voltage. It can be observed that an improvement is achieved at 90 Vac and 230

Vac mains.

As a final measurement, the comparison between the global efficiency with and without

TBO is shown in Figure 8, confirming the previous measurements.

Figure 8.

Comparison between the global efficiency with and without TBO

2.2

Harmonic content measurement

One of the main purposes of a PFC pre-conditioner is to correct the input current distortion,

decreasing the harmonic contents below the limits of the relevant regulations. Therefore, the

board has been tested according to the European rule EN61000-3-2 Class-D and Japanese

rule JEIDA-MITI Class-D, at full load and 50% of output rated load, at both nominal input

mains voltages.

As demonstrated in the illustrations below, the circuit is capable of reducing the harmonics

well below the limits of both regulations from full load down to light load. Because the

maximum input power of the board is close to the limit of 75 W, to demonstrate the correct

behavior of the circuit it has been tested also a 37 W (half load). Of course, no current

regulation requires meeting any limit at these power levels.

80%

81%

82%

83%

84%

85%

86%

87%

88%

89%

90%

90

115

230

265

Vin [Vrms]

WITHOUT TBO

WITH TBO

Figure 9.

EVAL6668-75W compliance to

EN61000-3-2 standard @230 V, 50

Hz - full load

Figure 10.

EVAL6668-75W compliance to

JEIDA-MITI standard @100 V, 60 Hz

- full load

0.0001

0.001

0.01

0.1

1

1 3 5 7 9 11 13 151719 212325 27 2931 333537 39

Harmonic Order [n]

Measured value

EN61000-3-2 Class-D limits

0.0001

0.001

0.01

0.1

1

1 3 5 7 9 111315 1719212325 2729 313335 37 39

Harmonic Order [n]

Measured value

JEIDA-MITI Class-D limits