application note 4.5w flyback converter for power line modem applications AN534/0695 by jo?l huloux, patrice morel, jean-michel ravon summary page i switching power supply description .............................. 2 i.1 general description . . . . . . . . . . . . . . . . . . . . . . . . . . . . ................... 2 i.2 schematic. . . . . . . . . . . . . . . . . ......................................... 2 ii switching power supply tests ..................................... 4 ii.1 voltage versus power. . . . . . ....................................... 4 ii.2 current consumption. ............................................. 4 ii.3 b.e.r. with switching power supply . . . . . . . . . . . . . ................... 4 results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ................... 4 ii.4 spectrum frequency and cenelec . . . . ............................. 5 iii measure on mains .................................................. 6 iii.1 mains alone . ....................................................... 6 iii.2 mains with p.l.m. communication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 iii.3 mains with p.l.m. communication and several noises. . . ............. 7 iv conclusion ..................................... ................... 9 1/9
i - switching power supply description the power supply described in this document has been realised in order to powering the power line modem st7537 applications. it provides 5v and 10v to supply the st7537 and a microcontroller. this power supply has the advantage of its small size, that is very important for home system de- vices. i.1 - general description the power supply is a 4.5w flyback converter which supply 10v dc with a switching supply proc- ess. its uses a uc3845 circuit that generate a 32.5khz square signal which drives a stk 2n50 mos or equivalent. the 5v dc is provided by a regulator l78m05 cs. in the version of the supply tested the supply board side is less than 4cm. table 1 : flyback converter specifications parameter test conditions value unit output voltage 20% of load 100% of load 10.15 and 5 9.75 and 5 v output maximum power 4.5 w dynamic of input voltage 130 to 264 v dc precision of regulation between 20% and 100% of load 4 % variation in voltage according to mains at 75% of load 0.4 % yield 80% of max. power, 0.218a on 10v and 0.15a on 5v 100% of max. power, 0.3a on 10v and 0.15a on 5v 100% of max. power 0.45a on 10v 59 61 74 % working temperature ambient temperature : 25 c55 o c maximum life time ambient temperature : 85 c ambient temperature : 55 c 8000 64000 hours output noise level i 0 = 450ma before regulator 80 peak-peak mv protective measure short cut protected i.2 - schematic 12 11 v in vc 14 v ref 7 rt/ct 2 4 nc nc 6 nc 13 nc 98 gnd pgnd r4 33k w c3 1nf c4 22 m f 16v + r6 120k w 1% r5 39k w 1% 5 c/sen c2 220pf r2 1k w 1 c1 39pf 3 comp vfb 10 out r9 680k w c7 4.7nf r1 22 w d4 d5 d6 3 x 1n4148 c9 47nf r10 100k w r3 1.2 w l1 470 m h1a toko 10rhb d2 smbyt01/400 d1 smbyt01/400 + + c5 68 m f 20v oscon r7 180k w 1/2w d7 bzwo4p 376 co19 c6 4.7 m f 400v d3 1n4007 r8 47 w 1/2w uc3845d 13 2 l78mo5x + c8 10 m f 10v ref 5v 10v ac2 ac1 t1 stk2n50 AN534-01.eps figure 1 : flyback converter 4.5w flyback converter for power line modem applications 2/9
table 2 : bill of materials item quantity reference part 1 1 c1 39pf 2 1 c2 220pf 3 1 c3 1nf 41c4 22 m f 16v 51c5 68 m f 20v oscon sanyo 61c6 4.7 m f 400v 7 1 c7 4.7nf 81c8 10 m f 10v 9 1 c9 47nf 10 2 d1 d2 byt01/400 byt01/400 11 1 d3 1n4007 12 3 d4 d5 d6 1n4148 1n4148 1n4148 13 1 d7 bzwo4p 376 co19 14 1 l1 10rhb 470 m h toko or equivalent 15 1 r1 22 w 16 1 r2 1k w 17 1 r3 1.2 w 18 1 r4 33k w 19 1 r5 39k w 1% 20 1 r6 120k w 1% 21 1 r7 180k w 1/2w 22 1 r8 47 w 1/2w 23 1 r9 680k w 24 1 r10 100k w 25 1 t1 stk 2n50 mos (sot-82) 600 w 500v 26 1 u1 uc3845d (sgs-thomson) 27 1 u2 l78m05x 4.5w flyback converter for power line modem applications 3/9
ii - switching power supply tests several tests have been done on the flyback con- verter and this section describes the way the tests have been done and shows the results. ii.1 - voltage versus power the power supply has been loaded on its 10v output by resistors of different values . the 5v dc has not been connected. the power has been calculated and results are shown below. table 3 : voltage, current and power consumption load ( w ) voltage (v) intensity (10 -3 a) power (w) nothing 10.87 23.5 9.78 420 4.07 47 9.97 210 2.11 150 10.17 68 0.68 500 10.42 20.8 0.22 1,000 10.54 10.5 0.11 demo-board tx 10.02 86.8 demo-board rx 10.18 28.5 11.0 10.5 10.0 9.5 9.0 01 234 test values vmax vmin voltage (v) power (w) AN534-03.eps figure 2 : voltage versus power ii.2 - current consumption the consumptions of the st7537 demo-board have been tested during the b.e.r. test with the flyback converter powering the transmitter, and then the receiver. values are given in the table below. in the worst case, the load on the mains was only a few ohms : all the laboratory devices were connected to the mains (with a personal computer which has a switching supply). the 5v does not depend on the impedance of the mains, it is only powering the microcontroller (st90e28l6), the 3 led's, and the rs232 driver (max 232). table 4 : flyback converter with demo-board consumption voltage transmitting receiving 220v ac 25.8ma 19ma 220v ac (worst case) 31ma 19ma 10v dc 86.8ma 28.5ma 10v dc (worst case) 133ma 28.5ma 5v dc 32ma 35.4ma ii.3 - b.e.r. with switching power supply the bit error rate test needs two demo-boards, one for transmission, the other one for reception. the board with the switching supply has been set in receive mode and in transmit mode. each time the b.e.r. results are the same as with regulated supply. on the transmitting demo board the pin test1 is set to 1 to allow continuous transmission. demo board st7537 switching power supply t ransmitter mains demo bo ard st7537 receiver regul ated power supply b.e.r. tester cersem tm1 511 bits pattern ccitt 1200bps/s bit/c ar infin ite AN534-04.eps figure 3 : switching power supply powering transmitter demo board st7537 switching power supply receiver mains demo bo ard st7537 t ransmitter regul ated power supply b.e.r. tester cersem tm1 511 bits pattern ccitt 1200bps/s bit/c ar infin ite AN534-05.eps figure 4 : switching power supply powering receiver results measurements are made using the laboratory power network. on this network, several devices were producing noise : - tektronix 2247a oscilloscope, - hp 3225b synthetiser, - weller wecp-20 soldering iron, - topward tps 4000 power supply, - a light. 4.5w flyback converter for power line modem applications 4/9
50 100 150 200 250 300 350 400 450 500 20 40 60 80 100 120 140 frequency (khz) lvl peak value (db m v) lvl peak value (db m v) cenelec bandwith 100hz spectrum analysis test 1 : flyback converter powering the transmitter AN534-06.ai figure 5 : st7537 demo-board with flyback converter there has been no error for more than a 15 minutes test period (in the two conditions). in 15 minutes there is : 15 ? 60 ? 1200 = 1080000 bits. that means a b.e.r. < 10 -6 . b.e.r. < 10 -6 ii.4 - spectrum frequency and cenelec the p.l.m. has been connected to a spectrum analyser in order to see the influencesof the flyback converter. the cenelec specification n en 50065- 1 peak values limit has been drawn (see the following table). the spectrum has been done with a hp 3585 spectrum analyser, configured accord- ing to cenelec ; that means a bandwidth of 100hz, and the use of the max hold function in order to keep the peak values. table 5 : cenelec specifications frequency band (mhz) limits (db m v) peak values limits (db m v) means 0.15 to 0.5 66 to 46 56 to 46 0.5 to 5 56 46 5to30 60 50 50 100 150 200 250 300 350 400 450 500 20 40 60 80 100 120 140 frequency (khz) lvl peak value (db m v) lvl peak value (db m v) cenelec bandwith 100hz spectrum analysis test 2 : regulated power supply powering transmitter AN534-07.ai figure 6 : st7537 demo-board with regulated supply 4.5w flyback converter for power line modem applications 5/9
4.8k w 6w phase 1.45k w 6w neutral 1/10 spectrum analyser 2.2nf 400v AN534-08.ai figure 7 : connecting the spectrum analyser to the mains iii - measure on mains during these tests, the transmit signal has been measured by connecting a spectrum analyser as described in figure 7. this operation needs to isolate the analyser from the earth and to connect its ground level to the neutral. a capacitor of 2.2nf is used to filter the 50hz and a voltage divider (resistors) is used to measure the signal. the sup- ply is shielded to avoid radiation. the values give theses results : r total = 4800 + 1450 = 6250 w f c =( r total ? c ? 2 ? p) = 1.1khz f c = 1.1khz v real = 10 ? v mes ? r total 1450 v realdb =v mesdb + 32.7db the values read on the spectrum analyser are 32.7db under the real values. the values on all the following spectrums has been corrected and take into account the 32.7db gain. 100 200 300 400 500 50 60 70 80 90 frequency (khz) lvl peak value (db m v) spectrum 1 bandwith 100hz mains spectrum frequency mains without device AN534-09.ai figure 8 : mains without device 100 200 300 400 500 40 60 80 100 120 frequency (khz) lvl peak value (db m v) spectrum 2 bandwith 100hz 140 st7537 + switching power supply AN534-10.ai figure 9 : the p.l.m. is alone on the mains iii.1 - mains alone in this case, the spectrum analyser has been con- nected to a laboratory mains without device on. this test gives an idea of the noise you can get on the mains. 4.5w flyback converter for power line modem applications 6/9
iii.2 - mains with p.l.m. communication this spectrum has been realised while the b.e.r. test was in progress. the two st7537 demo-board were the only devices connected to the mains. the peak values have been obtained by using the max hold function of the spectrum analyser. the car- rier frequency is at 132.45khz. iii.3 - mains with p.l.m. communication and several generators these tests have been realised with several de- vices such as drill, hoover, ... so the noise appears on the spectrum, and it is possible to compare the noise level and the signal level. during all theses tests, the b.e.r. test was in progress. no errors has been detected . the table on the following page gives the condi- tions at the moment of the realisation of the spec- trum. the values have been registered by the use of the spectrum analyser hpib interface, and are peak values. each graph is realised with 1001 points. table 6 : conditions of the tests spectre device conditions frequency range figure 11 drill bosch 420w ref. 1123-7 several switch on/off accelerating 100khz to 500khz figure 12 drill bosch 420w ref. 1123-7 several switch on/off accelerating 1khz to 5mhz figure 13 neon lighting osram15w ref. rz2 several switch on/off 50khz to 500khz figure 14 hoover nilfisk 700w model gst several switch on/off 50khz to 500khz figure 15 all laboratory devices normal use 50khz to 500khz all the devices are operating under 220v 50hz. the analyser bandwidth has been set to 10khz. the different spectrum are given below. 100 200 300 400 500 80 100 120 140 frequency (khz) lvl peak value (db m v) spectrum 3 bandwith 10khz mains spectrum frequency AN534-11.ai figure 10 : transmitting while using a drill 012345 80 100 120 140 160 thousands frequency (khz) lvl peak value (db m v) spectrum 4 bandwith 10khz mains spectrum frequency AN534-12.ai figure 11 : transmitting while using a drill (wide spectrum) 4.5w flyback converter for power line modem applications 7/9
50 100 150 200 250 300 350 400 450 500 40 60 80 100 120 frequency (khz) lvl peak value (db m v) spectrum 5 bandwith 10khz mains spectrum frequency AN534-13.ai figure 12 : transmitting while using a neon lighting 50 100 150 200 250 300 350 400 450 500 60 80 100 120 140 160 frequency (khz) lvl peak value (db m v) spectrum 6 bandwith 10khz mains spectrum frequency AN534-14.ai figure 13 : transmitting while using a hoover 80 90 frequency (khz) spectrum 7 bandwith 10khz mains spectrum frequency st7537 + switching power supply 110 100 70 60 50 500 lvl peak value (db m v) AN534-15.eps figure 14 : all the laboratory devices on use in this last graph, the level of the st7537 carrier has fallen to 104db m v because of the load on the mains (we have connected a personal computer which has a switching power supply). nevertheless, the communications occurs without any errors. 4.5w flyback converter for power line modem applications 8/9
iv - conclusion information furnished is believed to be accurate and reliable. however, sgs-thomson microelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. no licence is granted by implication or otherwise under any patent or patent rights of sgs-thomson microelectronics. specifications mentioned in this publication are subject to change without noti ce. this publication supersedes and replaces all information previously supplied. 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. ? 1995 sgs-thomson microelectronics - all rights reserved purchase of i 2 c components of sgs-thomson microelectronics, conveys a license under the philips i 2 c patent. rights to use these components in a i 2 c system, is granted provided that the system conforms to the i 2 c standard specifications as defined by philips. sgs-thomson microelectronics group of companies australia - brazil - china - france - germany - hong kong - italy - japan - korea - malaysia - malta - morocco the netherlands - singapore - spain - sweden - switzerland - taiwan - thailand - united kingdom - u.s.a. even with a high level noise or important distur- bance on mains, or even a load under 5 w , the st7537 has a b.e.r. under 10 -6 (we have not detected any error during all the test period). power line system communication needs a st7537, a power line interface, a control system, and a 10v dc supply. the power line interface is already existing, and sgs-thomsonprovides a large range of microcontrollers (interface between st9 micro- controller and st7537 has been realised). the flyback converter comes to provides 10v dc for p.l.m. (and a 5v dc for the microcontroller) and replace the classical regulated supply. the st7537 and power line interface consumption lets more than 2.5w for microcontroller and application, available in both 5 and 10v. the 10v fluctuations are under the st7537 specifications (which needs 10v 10%). in fact, the flyback converter is really suited to st7537 applications : - its voltages complies with st7537 specifications, - it does not disturb the transmit spectrum, - the performances of the power line modem are the same as with regulated supply, - its size allows its use in small systems, like home system applications, - the 4.5w power provides supply for both p.l.m and microcontroller. 4.5w flyback converter for power line modem applications 9/9
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