The evaluation board has been designed using: a

faster not dissipative start-up circuit, a diode (D2)

to speed-up the MOS start-off time and (even if a

single resistor can be used) an external divider to

improve the precision of the overcurrent thresh-

old.

Further there is a possibility to change the input

threshold voltage using an external divider (R23

and R22) and if an inrush current problem arises

a NTC resistor can be used.

The PFC demoboard performances has been

evaluated testing the following parameters:

PF (power factor), A-THD (percentage of current

total harmonic distortion), H3..H9 (percentage of

current’s n

th

harmonic amplitude),

η (efficiency).

The test configuration, equipments and results

are:

AC POWER

SOURCE

LARCET /3KW

PM1200

AC POWER

ANALYSER

EMI

FILTER

PFC

L4981

DEMO

LOAD

D94IN057

PF

A-THD

H3

H5

H7

H9

PO

η

(Hz)

(W)

(%)

(%)

(%)

(%)

(%)

(V)

(V)

(W)

(%)

88

60

222

0.999

2.94

1.98

0.61

0.55

0.70

390

8

200

90.2

110

60

220

0.999

1.79

1.40

0.40

0.31

0.28

392

8

201

91.6

132

60

218

0.999

1.71

1.16

0.40

0.35

0.31

394

8

202

92.8

180

50

217

0.999

1.88

1.52

0.65

0.40

0.34

396

8

203

93.8

220

50

217

0.997

2.25

1.68

0.83

0.57

0.48

398

8

204

94.2

260

50

216

0.995

3.30

1.84

1.30

0.39

0.73

400

8

205

95.2

EMI/RFI FILTER

The harmonic content measurement has been

done using an EMI/RFI filter interposed between

the AC source and the demoboard under test,

while the efficiency has been calculated without

the filter contribution.

C1

D94IN052

T1

T2

C

LINE

PFC

EARTH

where:

T1 = 1mH

C1 = 0.33

µF, 630V

T2 = 27mH

C2 = 2.2nF, 630V

L4981A - L4981B

14/17