AN828

APPLICATION NOTE

1500W - 440V POWER FACTOR CORRECTOR

PREREGULATOR

The application here described has been tailored

to supply a three phase inverter for motion con-

trol (see fig.1). To reduce the current in the

switches of the inverter, the output voltage of the

power factor has been held quite high.

The target specification of the PFC application is:

Mains supply Vin(rms)

= 220Vac

±20%

(f = 50/60Hz)

Output Voltage Vout

= 440Vdc

Output Power Pout

= 1500W

A switching frequency of 60kHz has been chosen

as a good compromise between requirements of

small size magnetics and low switching losses.

For this application a full isolated ISOTOP(TM)

STE30NA50-DK has been used.

This module is especially intended for boost appli-

cations and consists off the integration of a low

RDS/500V Mosfet with a TURBOSWITCH(TM) di-

ode.

The use of the module allows a compact and ef-

fective solution in terms of layout and power dis-

sipation. The output stage of the L4981A/B is ca-

pable of driving directly the module without the

aid of a buffer stage. The L4981A controller is

supplied by the auxiliary of the boost inductor, a

Graetz bridge and a simple resistor for the start-

up phase. The Output capacitor filter has been re-

alized connecting in parallel four tap in "series"

configuration. This solution allows the use stand-

ard parts, in terms of the rated voltage, resulting

easier to be implemented in comparison with a

"single" configuration. To be noted that the high

frequency filter (C1 + C2) has been split in two

parts. In this way it is possible to held a low value

capacitor (C2) connected to the output of the rec-

tifier bridge, minimising the harmonic

distortion

(introduced by the rectified DC contents). On the

other hand, the capacitor (C1) connected to the

AC side of the bridge, performs most of the high

frequency filter function without introducing DC

content.

The schematic circuit is shown in fig.1

October 2002

®

R4

1M

4

BRIDGE

KBPC25-04

L4981A

R3

75K

1W

19

T

13

14

C6 330nF

R10 120K 5%

3

R12 15 5%

Rx

150K

20

R2

220

1%

R8

3.9K

5%

R6 100K

5%

C3

330nF

R9

3.9K

5%

C5

105nF

R7

27K

1%

C7

10

µF

16V

1

R15

10K

1%

R17

10K

1%

R14

820K

1%

R16

909K

1%

12

17

10

18

9

5

8

2

FUSE

10A/250V

Vi

Co

1

µF

630V

+

-

Po=1500W

Vo=440V

D95IN249C

176VAC/265VAC

D3

1N4150

C1

2.2

µF

250V

+

-

C2

220nF

R5

47

500mW

D2

4 x

1N4150

C4 220

µF 25V

Dz 18V 500mW

R11 3.9K 5%

7

6

11

R1

5.1K

1%

R13

1 5%

STE30NA50-DK

Rx

150K

4 x

470

µF

315V

4 x

470

µF

315V

Transformer

Core: THOMSON - CSF GER55x28x25

Gap: 3.1mm for a total primary inductance of 440

µH

Primary: 42 turns of 8x0.5mm (#24 AWG)

Secondary: 4 turns of #27 AWG (0.15mm)

Figure 1: Schematic Diagram

1/3