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 AN828/1297 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 m f 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 m f 630v + - po=1500w vo=440v d95in249c 176v ac /265v ac d3 1n4150 r s 10m w c1 2.2 m f 250v + - c2 220nf + - r5 47 500mw d2 4 x 1n4150 c4 220 m f 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 m f 315v 4 x 470 m f 315v transformer core: thomson - csf ger55x28x25 gap: 3.1mm for a total primary inductance of 440 m h primary: 42 turns of 8x0.5mm (#24 awg) secondary: 4 turns of #27 awg (0.15mm) figure 1: schematic diagram 1/3
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 w /1w r1 = 5.1k w /1% r2 = 220 w /1% r3 = 75k w/1w r4 = 1m r5 = 47 /1/2 w r6 = 100k w r7 = 27k /1% r8 + r9 = 3.9k w r10 = 120k w r11 = 3.9k w r12 + r13 = 15 w r14 = 820k w /1% r15 = 10k w /1% r16 = 909k w r17 = 10k w co= 940 m f = [(4 + 4) x 470 m f/315v + 1 m f/630v] c1 = 2.2 m f/250vac c2 = 220nf/630v c3 = 330nf c4 = 220 m f/25v c5 = 1.5nf c6 = 330nf c7 = 10 m f power switch = ste30na50-dk input bridge = kpbc25-04 d2 = 1n4150 (x 4) d3 = 1n4150 application note 2/3
information furnished is believed to be accurate and reliable. however, sgs-thomson microelectronics assumes no responsib ility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result f rom its use. no license is granted by implication or otherwise under any patent or patent rights of sgs-thomson microelectronics. specification mentioned in this publication are subject to change without notice. this publication supersedes and replaces all information previously s upplied. sgs- thomson microelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of sgs-thomson microelectronics. ? 1997 sgs-thomson microelectronics C printed in italy C all rights reserved sgs-thomson microelectronics group of companies australia - brazil - canada - china - france - germany - italy - japan - korea - malaysia - malta - morocco - the netherlands - singapore - spain - sweden - switzerland - taiwan - thailand - united kingdom - u.s.a. application note 3/3
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