CONCLUSIONS

The evaluation has been done using the "A" ver-

sion of the L4981 controller, without using addi-

tional features obtaining high performance re-

sults, in terms of efficiency and harmonic content.

Further improvements are possible using the ad-

ditional features of the I.C. such as the LFF (pin

16) for the best control of the output voltage or

by the use of the B version to minimise the EMI

filter.

Table 1: Test Result.

Mains rms

(V)

Vout

(V)

Pout

(W)

Power

Factor

Harmonic Distortion (%)

THD

AH3

Efficiency

(%)

176

451

509

0.998

2.0

1.9

94.2

176

444

937

0.999

1.4

1.3

94.0

176

438

1396

0.999

1.0

0.9

94.0

220

451

509

0.996

2.1

1.9

95.6

220

445

941

0.998

1.5

1.4

95.2

220

438

1396

0.999

1.0

0.9

95.3

260

452

511

0.993

2.5

1.9

95.1

260

446

945

0.997

1.4

1.3

96.4

260

439

1402

0.999

1.1

0.8

96.1

L4981A PARTS LIST

Boost inductor (T) L = 0.44mH

Core :Thomson - E 55x28x25

Gap = 3mm

Primary Turns = 42 (8 x 0.5mm)

Secondary Turns = 4 (0.15mm)

Rs = 10m

Ω /1W

R1 = 5.1k

Ω /1%

R2 = 220

Ω /1%

R3 = 75k

Ω/1Ω

R4 = 1M

R5 = 47 /1/2

Ω

R6 = 100k

Ω

R7 = 27k /1%

R8 + R9 = 3.9k

Ω

R10 = 120k

Ω

R11 = 3.9k

Ω

R12 + R13 = 15

Ω

R14 = 820k

Ω /1%

R15 = 10k

Ω /1%

R16 = 909k

Ω

R17 = 10k

Ω

Co= 940

µF = [(4 + 4) x 470µF/315V + 1µF/630V]

C1 = 2.2

µF/250Vac

C2 = 220nF/630V

C3 = 330nF

C4 = 220

µF/25V

C5 = 1.5nF

C6 = 330nF

C7 = 10

µF

Power Switch = STE30NA50-DK

Input Bridge = KPBC25-04

D2 = 1N4150 (X 4)

D3 = 1N4150

AN828 APPLICATION NOTE

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