L4981B datasheet(14/17 Pages) STMICROELECTRONICS

14 / 17 page

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

harmonic amplitude),

∆Vo (output

voltage ripple), Vo (output voltage),

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

fPi

A-THD

∆VO

(Vrms)

(Hz)

(W)

(%)

(V)

(W)

(%)

222

0.999

2.94

1.98

0.61

0.55

0.70

390

200

90.2

110

220

0.999

1.79

1.40

0.40

0.31

0.28

392

201

91.6

132

218

0.999

1.71

1.16

0.40

0.35

0.31

394

202

92.8

180

217

0.999

1.88

1.52

0.65

0.40

0.34

396

203

93.8

220

217

0.997

2.25

1.68

0.83

0.57

0.48

398

204

94.2

260

216

0.995

3.30

1.84

1.30

0.39

0.73

400

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.

D94IN052

LINE

PFC

EARTH

where:

T1 = 1mH

C1 = 0.33

µF, 630V

T2 = 27mH

C2 = 2.2nF, 630V

L4981A - L4981B

14/17

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