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january 2008 rev 1 1/30 AN2600 application note smps for high-end pv r based on l6668 introduction the set-top box (stb) market is growing very fa st due to the high gr owth of both satellite and terrestrial/cable broadcasting. as expected, the market is always looking for solutions with high cost effectiveness and performance. this document introduces a reference design of a 55 w switch-mode power supply dedicated to high-end set-top box applications, and in particular for pvrs (personal video recorders). this kind of solution in addition to typical loads is able to supply hd and vfd front panels. the board accepts european input voltage range (from 185 to 265v ac ) and delivers eight outputs. it is based on the advanced current mode pwm controller l6668, working at fixed frequency. despite high performance, standard parts are used, e.g. standard capacitors are connected on the outputs in place of low esr components commonly used, contributing to an overall decrease of the total cost of the solution. figure 1. steval-isa040v1 www.st.com
contents AN2600 2/30 contents 1 main characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2 circuit description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.1 transformer specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.1.1 windings data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.2 bom . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3 test description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 3.1 cross regulation and main waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 3.2 high frequency ripple of output voltages at full load . . . . . . . . . . . . . . . . . 20 3.3 measurement of rms current of output capacitors . . . . . . . . . . . . . . . . . 21 3.4 dynamic load test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 3.5 startup behavior . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 3.6 wakeup time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 3.7 short circuit test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 3.8 conducted emission (emi) measurements . . . . . . . . . . . . . . . . . . . . . . . 28 3.9 thermal measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 4 conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 5 revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
AN2600 list of tables 3/30 list of tables table 1. output specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 table 2. windings parameters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 table 3. bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 table 4. output voltages measurement at v in = 184 v and full load . . . . . . . . . . . . . . . . . . . . . . . . . 12 table 5. output voltages measurement at v in = 230 v and full load . . . . . . . . . . . . . . . . . . . . . . . . . 12 table 6. output voltages measurement at v in = 276 v and full load . . . . . . . . . . . . . . . . . . . . . . . . . 13 table 7. output voltages measurement at v in = 184 v and reduced load. . . . . . . . . . . . . . . . . . . . . 14 table 8. output voltages measurement at v in = 230 v and reduced load. . . . . . . . . . . . . . . . . . . . . 15 table 9. output voltages measurement at v in = 276 v and reduced load. . . . . . . . . . . . . . . . . . . . . 15 table 10. output voltages measurement at v in = 184 v and reduced load (20 w) . . . . . . . . . . . . . . . 17 table 11. output voltages measurement at v in = 230 v and reduced load (20 w) . . . . . . . . . . . . . . . 17 table 12. output voltages measurement at v in = 276 v and reduced load (20 w) . . . . . . . . . . . . . . . 17 table 13. output voltages measurement at v in = 230 v and light load . . . . . . . . . . . . . . . . . . . . . . . . 19 table 14. measurement of high frequency ripple of output voltages at v in = 230 v and full load . . . . 20 table 15. measurement of rms current of output capacitors at v in = 230 v and full load . . . . . . . . . 21 table 16. dynamic load test on 3.3 v out . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 table 17. dynamic load test on 5 v out . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 table 18. overshoot . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 table 19. thermal behavior of the components at primary side. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 table 20. thermal behavior of the components at secondary side . . . . . . . . . . . . . . . . . . . . . . . . . . 29 table 21. document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
list of figures AN2600 4/30 list of figures figure 1. steval-isa040v1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 figure 2. electrical schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 figure 3. transformer electrical and mechanical drawings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 figure 4. vds and id of stp5nk60z in full load at v in = 184 v rms - 50 hz . . . . . . . . . . . . . . . . . . . . 13 figure 5. vds and id of stp5nk60z in full load at v in = 230 v rms - 50 hz . . . . . . . . . . . . . . . . . . . . 13 figure 6. vds and id of stp5nk60z in full load at v in = 276 v rms - 50 hz. . . . . . . . . . . . . . . . . . . . 14 figure 7. vds and id of stp5nk60z at reduced load v in = 184 v rms - 50 hz . . . . . . . . . . . . . . . . . 15 figure 8. vds and id of stp5nk60z at reduced load v in = 230 v rms - 50 hz . . . . . . . . . . . . . . . . . 16 figure 9. vds and id of stp5nk60z at reduced load v in = 276 v rms - 50 hz . . . . . . . . . . . . . . . . . 16 figure 10. vds and id of stp5nk60z at reduced load (20 w) v in = 184 v rms - 50 hz . . . . . . . . . . . . 18 figure 11. vds and id of stp5nk60z at reduced load (20 w) v in = 230 v rms - 50 hz . . . . . . . . . . . . 18 figure 12. vds and id of stp5nk60z at reduced load (20 w) v in = 276 v rms - 50 hz . . . . . . . . . . . . 19 figure 13. vds and id of stp5nk60z at light load at 230 v . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 figure 14. high frequency ripple of output voltages at full load at 230 v. . . . . . . . . . . . . . . . . . . . . . . 21 figure 15. outputs behavior under dynamic load on 3.3 v output at v in =230 v. . . . . . . . . . . . . . . . . 22 figure 16. behavior of outputs with dynamic load applied to 5 v output at v in =230 v . . . . . . . . . . . . 23 figure 17. startup behavior of the system at v in = 184 v rms - 50 hz. . . . . . . . . . . . . . . . . . . . . . . . . . 24 figure 18. startup behavior of the system at v in = 230 v rms - 50 hz. . . . . . . . . . . . . . . . . . . . . . . . . . 24 figure 19. startup behavior of the system at v in = 276 v rms - 50 hz. . . . . . . . . . . . . . . . . . . . . . . . . . 25 figure 20. wakeup behavior of the system at v in = 184 v rms - 50 hz . . . . . . . . . . . . . . . . . . . . . . . . . 26 figure 21. wakeup behavior of the system at v in = 230 v rms - 50 hz . . . . . . . . . . . . . . . . . . . . . . . . . 26 figure 22. wakeup behavior of the system at v in = 276 v rms - 50 hz . . . . . . . . . . . . . . . . . . . . . . . . . 27 figure 23. short circuit on 5 v output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 figure 24. conducted emissions of the system at full load and v in =230 v - phase conducted emission28 figure 25. conducted emissions of the system at full load and v in =230 v-neutral conducted emission 28
AN2600 main characteristics 5/30 1 main characteristics the main characteristics of the smps are listed below: input voltage: ?v in = 185 265 v rms ?f=50 hz emi: in accordance with en55022 class b safety: in accordance with iec 60065 7 th ed. table 1. output specifications vout (v): iout (a) pout (w) tolerance notes 1 3.3 3.5 11.55 +/- 5% dedicated to 3.3 v circuitry, 2.6 v and 1.1 v local post regulators 2 5 1.9 9.5 +/- 5% dedicated to hdd, display, 5v circuitry and 2.6 v local post regulators 3 12 0.8 9.6 +/- 2% dedicated to hdd 4 16 0.5 8 +/- 10% dedicated to lnb for satellite dvb 5 23 0.5 11.5 +/- 10% dedicated to lnb for satellite dvb 6 -25 0.15 3.75 +/- 10% dedicated to display 7 3.3 ac 0.08 0.25 dedicated to the display filaments 8 33 0.01 0.33 +/- 10% dedicated to the tuner p out (w) =55 w
main characteristics AN2600 6/30 figure 2. electrical schematic + c108 470uf 16v 1 2 3 4 j8 hdd_con 12v 5v r112 6.8r 2w r113 6.8r 2w + c107 1uf 100v q9 bd139 r84 33k 2w r99 10k q10 bc848b q11 bc848b + c27 10uf 50v ahfan r93 22k ahfan 1 2 3 4 j9 con4 r110 10k nc 1 2 j4 con2 1 2 3 4 5 6 7 8 9 10 11 12 j7 dvb-s2 + c77 1000uf c76 2n2 y 1 d56 by t01-400 r62 100k 25v r94 10k c78 220nf c79 220nf f4 fuse 2a r63 2k + c80 68uf 275v x2 5v 275v x2 r64 ntc_15r r65 1k0 r95 22k r66 47k r67 33k d50 stth802cfp 3.3v 1 2 3 4 5 6 7 8 9 10 11 12 13 j5 full_con 400v + c81 470uf 400v + c83 22uf r68 33k 2w d52 stth302 c84 10nf r69 6.2k r70 3.9k d53 stth1l06 + c87 10uf 16v r97 22k + c106 1uf 100v hv 1 hvs(nc) 2 pfc_stop 14 vref 8 vcc 5 skipadj 9 rct 16 st-by 13 n.c. 6 ss 11 dis 7 comp 10 s_comp 15 gnd 3 out 4 isen 12 u13 l6668 r71 1r5 r72 470e r73 2k2 fl2t lnb_16v fl1 c89 470p 35v l28 22uh r74 24k l29 22uh c90 100nf 2 1 3 q7 bc858b lnb_23v fl2 + c91 4700uf + c92 10uf 50v d54 stps1545cfp d55 stps745fp r75 10k d57 bav103 2 1 3 u15 tl431 c93 2n2 r76 3.3k r77 68r lnb_23v 1 4 2 3 l30 2*45mh c94 1000nf r115 1k l31 22uh r78 4.3k 1 3 2 q4 stp5nk60zfp r80 1r5 r81 1r5 d67 12vz d58 1n4007 d59 1n4007 d60 1n4007 d61 1n4007 + c96 33uf l32 22uh 35v c97 100nf r114 1k8 1 2 4 3 u16 pc817 + c98 33uf d62 bav103 lnb_16v r82 150r r89 220k c99 470pf fl1 c100 100p c82 2n2 y 1 r90 100k r92 220k + c102 fl2 + c103 10uf 100v 33v d65 33vz ahfan lnb_23v lnb_16v 3.3v 5v 12v 3.3v d66 12vz 50v 5v r109 22r 4 14 10 9 8 12 11 13 15 16 1 3 2 5 t4 2522.5006a d70 1n4148 50v -25v -25v 6.3v c95 470nf 12v r98 22k fl2t 2 1 3 q5 bc848b 33v d63 stth102 d64 27vz 2200uf 16v + c105 22uf 50v r100 470r -25v 2 1 3 q6 bc848b vin 3 vout 2 1 gnd u5 ld1084v12 12v + c26 22uf r111 8.2k 1 2 3 4 5 6 7 8 9 10 j6 dvb-t r83 33k 2w l33 22uh ahfan 3.3v 5v 12v l34 22uh fl1 33v 5v 50v q8 bd140 + c101 470uf 16v d72 1n4148
AN2600 circuit description 7/30 2 circuit description the topology used in this power supply is a standard flyback, working in continuous conduction mode with fixed frequency. the s witching frequency (65 khz) represents a good trade-off between the transformer size and the harmonics of the switching frequency, in order to optimize the input filter size and cost. the power mosfet is a 600 v-1.6 ? in supermesh? technology, housed in a to-220fp (insulated package). the reflected voltage is 70 v, providing enough room fo r the leakage inductance voltage spike with still margin for reliability. the network d53-r68- r83-r84-c84 clamps th e peak of the leakage inductance voltage spike. the controller is the new l6668, integrating all the functionalities needed to control an smps with high performance and minimum component count, offering the maximum flexibility. a new functionality embedded in th e device is a high voltage startup internal circuit which draws current from the dc bus and charges the ic supply capacitor (c96). as soon as the voltage on this capacitor reaches the l6668 turn-on threshold, the controller starts to drive the mosfet, and the ic is s upplied only by the auxiliary winding of the transformer via the diode d62 (after startup, the hv current source is deactivated, saving power during normal operation). the control system is current mode, so the current flowing in the primary is sensed by r71, r80 and r81 then filtered by r65 and c100 and fed into pin 12 (isen). no slope compensation is needed as the duty cycle is kept well below 50%. the circuit connected to pin 7 (dis) provides overvoltage protection in case of feedback network failures and open loop operation. an internal comparator senses this pin voltage and in case its threshold is exceeded, the l6668 stops operating and reduces its consumption. after disable intervention the controller operation can be resumed only by disconnecting the mains plug. the switching frequency is programmed by the rc network connected to pin 16 (rct) and in case of reduced load operation, the controller can decrease the operating frequency via pin 13 (st-by) and resistor r69 proportionally to the load consumption. the output rectifiers have been chosen according to the maximum reverse voltage and power dissipation. the 3.3 v and 5 v outputs rectifiers are schottky type, featuring lower losses compared to standard pn diodes. the diodes d50, d54 and d55 need a small heat sink, as indicated on the bom. the other output rectifiers are fast recovery. the 12 v output is obtained from the 16 v output by a high-current low-drop voltage regulator. the output voltage control is performed by the secondary feedback on the 5 v and 3.3 v outputs, while for the other outputs the control is achieved by the transformer coupling. the feedback network uses a tl431 driving an opto-c oupler, in this case a pc817, ensuring the required insulation between primary and secondary. the opto-transistor drives directly the comp pin of the l6668. an lc filter has been added on all outputs in order to filter the high frequency ripple without increasing the output capacitors. the input emi filter consists of two x2 capacitors with a common mode choke in between. the ntc limits the inrush current charging the input capacitor at plug-in. the transformer is layer type, manufactured by pulse eldor corporation, in accordance with the safety standard iec 60065 7 th ed.
circuit description AN2600 8/30 2.1 transformer specification figure 3. transformer electrical and mechanical drawings primary inductance: 675 h 10% at 10 khz - 1 v leakage inductance: 20 h at 100 khz - 1 v typical operating frequency: 65 khz 2.1.1 windings data table 2. windings parameters terminal no. windings number of turns wire 2-3 w1 primary/2 26 0.45 - g 12-11 w2 - 3.3 v 3 cu-foil - w=10 mm t=0.1 mm 13-12 w3 - 5 v 1 cu-foil - w=10 mm t=0.1 mm 14-11 w4 - 16 v 12 2x0.45-g2 15-14 w5 - 23 v 4 0.45-g2 16-11 w6 - 33 v 26 0.25-g2 10-11 w7 - 25 v 20 0.25-g2 9-8 w8 - fl 3 0.25-g2 4-5 w9 - aux 10 0.25-g2 3-1 w10 - primary/2 26 0.45-g2
AN2600 circuit description 9/30 2.2 bom table 3. bill of material qty reference value & part description 3 c26,c83,c105 22 f 50 v electrolytic cap 1 c27 10 f 50 v electrolytic cap 2 c76,c82 2.2 nf 4 kv y1 cap 1 c77 1000 f 25 v electrolytic cap 2 c78,c79 220 nf 75 v x2 cap 1 c80 68 f 400 v electrolytic cap 1 c81 470 f 35 v electrolytic cap 1 c84 10 nf 400 v ceramic cap 1 c87 10 f 16 v electrolytic cap 2 c89,c99 470 pf 0805 50 v smd ceramic cap 1 c90 100 nf 1206 50 v smd ceramic cap 1 c91 4700 f 6.3 v electrolytic cap 1 c92 10 f 50 v electrolytic cap 1 c93 2.2 nf 0805 50 v smd ceramic cap 1 c94 1000 nf 0805 50 v smd ceramic cap 1 c95 470 nf 1206 50 v smd ceramic cap 1 c96 33 f 35 v electrolytic cap 1 c97 100 nf 0805 50 v smd ceramic cap 1 c98 33 f 50 v electrolytic cap 2 c101, c108 470 f 16 v electrolytic cap 1 c106, c107 1 f 100v electrolytic cap 1 c100 100 pf 0805 25 v smd ceramic cap 1 c102 2200 f 16 v electrolytic cap 1 c103 10 f 100 v electrolytic cap 1 d50 stth802cfp stmicroelectronics high-efficiency, ultrafast diode 1 d52 stth302 stmicroelectronics high-efficiency, ultrafast diode 1 d53 stth1l06 stmicroelectronics ultrafast, high-voltage rectifier 1 d54 stps1545cfp stmicroelectroni cs power schottky rectifier 1 d55 stps745fp stmicroelectronics power schottky rectifier 1 d56 byt01-400 stmicroelectronics high-efficiency, ultrafast diode 2 d57,d62 bav103 general-purpose rectifier 4 d58,d59,d60,d61 1n4007 rectifier 1 d63 stth102 stmicroelectronics ultrafast diode
circuit description AN2600 10/30 1 d64 27vz do35 1 w zener diode 1 d65 33vz d035 1 w zener diode 2 d66,d67 12vz d034 0.5w zener diode 2 d70,d72 1n4148 general-purpose rectifier 1 f4 fuse 2 a radial fuse 1 j4 con2 7.62 mm pitch two-pin input connector 1 j5 full_con 2.54 mm pitch 13-pin output connector 1 j8 hdd_con rs code:471-430 hard disk connector 1 j9 con4 2.54 mm pitch 4-pin vfd connector 4 l28,l29,l31,l32 22 h 5 a radial power inductor 1 l30 2*45 mh-hf2430-453 tdk common-mode choke coils 2 l33,l34 22 h 1 a radial inductor 1 q4 stp5nk60zfp stmicroelectronics n-channel power mosfet 4 q5,q6,q10,q11 bc848b npn general-purpose bipolar 1 q7 bc858b pnp general-purpose bipolar 1 q8 bd140 stmicroelectronics pnp transistor 1 q9 bd139 stmicroelectronics npn transistor 3 r62, 100 k ? 0805 smd resistor r75,r94 10 k ? 0805 smd resistor 1 r63 2 k ? 0805 smd resistor 1 r64 ntc_16 ? 2.9 a inrush current suppressor 1 r65 1 k ? 0805 smd resistor 1r66 47 k ? 0805 smd resistor 1r67 33 k ? 0805 smd resistor 2 r68,r83,r84 33 k ? 2 w axial resistor 1 r69 6.2 k ? 1206 smd resistor 1 r70 3.9 k ? 0805 smd resistor 3 r71,r80,r81 1.5 ? 1206 smd resistor 1 r72 470 ? 0805 smd resistor 1 r73 2.2 k ? 1206 smd resistor 1r74 24 k ? 1206 smd resistor 1 r76 3.3 k ? 1206 smd resistor 1 r77 68 ? 1206 smd resistor 1 r78 4.3 k ? 0805 smd resistor 1 r79 not mounted 1 m ? ? w axial resistor table 3. bill of material (continued) qty reference value & part description
AN2600 circuit description 11/30 note: q4 needs 15 c/w heatsink; d50, d54, d55 needs 20 c/w heatsink; u5 needs 12 c/w heatsink; 1 r82 150 ? 1206 smd resistor 2 r89,r92 220 k ? 0805 smd resistor 1 r90 100 k ? 0805 smd resistor 4 r93,r95,r97,r98 22 k ? 0805 smd resistor 1r99 10 k ? 0805 smd resistor 1 r100 470 ? ? w axial resistor 1r109 22 ? ? w axial resistor 1 r110 not mounted 10 k ? 0805 smd resistor 1 r111 8.2 k ? ? w axial resistor 2 r112,r113 6.8 ? 2 w axial resistor 1r114 1.8 k ? 0805 smd resistor 1r115 1 k ? 0805 smd resistor 1 t4 2522.5006c pulseeng smt 1 u5 ld1084v12 stmicroelectronics 5 a low-drop, positive voltage regulator 1 u13 l6668 stmicroelectronics smart primary controller 1 u15 tl431 stmicroelectronics voltage reference 1 u16 pc817 optocoupler table 3. bill of material (continued) qty reference value & part description
test description AN2600 12/30 3 test description the set of tests performed on the board aim to evaluate the performance of the power supply for different load conditions, in terms of regulation, power consumption, efficiency and safe operating area of the power mosfet, moreover, in order to evaluat e the behavior of the smps in terms of stability, the performance under dynamic load condition have been measured and several tests have been performed at startup with three different input voltage values and full load conditions. finally the conducted emission measurements and the thermal performances of the main critical components have been evaluated. 3.1 cross regulation and main waveforms in ta b l e 4 , 5 , and 6 the output voltage cross regulation is given with static and dynamic loads and the overall efficiency of the converter measured at different input voltages. all the output voltages have been measured after the load connector by means of a digital multimeter. the length of the connection cable is 100 mm. moreover the primary power mosfet stp5nk60z main waveforms are shown. full load - satellite2 dvb note: all voltages are within tolerance. note: all voltages are within tolerance. table 4. output voltages measurement at v in = 184 v and full load v out [v] 3.42 5.1 11.94 16.8 22.94 32.28 -26.9 v in [v rms ] 184 ? v out % + 3.6 + 2 -0.5 + 5 - 0.26 -2.2 + 7.6 i out [a] 3.5 1.9 0.8 0.5 0.5 0.01 0.15 i in [a rms ] 0.742 p out [w] 11.97 9.69 9.55 8.41 11.49 0.32 4.03 p in [w] 76.3 p outtot [w] 55.46 (%) 73 f s [khz] 67.8 table 5. output voltages measurement at v in = 230 v and full load v out [v] 3.44 5.08 11.9 16.71 22.8 31.98 -26.67 v in [v rms ] 230 ? v out % 4.2 +1.6 -0.8 +4.4 -0.8 -2.2 +6.68 i out [a] 3.5 1.9 0.8 0.5 0.5 0.01 0.15 i in [a rms ] 0.623 p out [w] 12.04 9.65 9.52 8.37 11.44 0.32 4 p in [w] 75.2 p outtot [w] 55.34 (%) 73.6 f s [khz] 67.1
AN2600 test description 13/30 note: all voltages are within tolerance. figure 4. v ds and i d of stp5nk60z in full load at v in = 184 v rms - 50 hz figure 5. v ds and i d of stp5nk60z in full load at v in = 230 v rms - 50 hz table 6. output voltages measurement at v in = 276 v and full load v out [v] 3.42 5.09 11.91 16.69 22.8 32.21 -26.72 v in [v rms ] 276 ? v out % 3.6 +1.8 -0.75 +4.3 -0.8 -2.4 +6.88 i out [a] 3.5 1.9 0.8 0.5 0.5 0.01 0.15 i in [a rms ] 0.548 p out [w] 11.97 9.67 9.53 8.36 11.41 0.32 4 p in [w] 74.9 p outtot [w] 52.5 (%) 73.8 f s [khz] 66.4
test description AN2600 14/30 figure 6. v ds and i d of stp5nk60z in full load at v in = 276 v rms - 50 hz note: ch1: drain voltage (brown) ch2: drain current (blue) v in (v ac ): 184 - 230 - 276 v dsmax (v): 420 - 476 - 540 i dpk (a): 1.78 - 1.78 - 1.72 the measured values are the drain peak voltage and current at minimum, nominal and maximum input mains voltage, during normal operation at full load. the voltage peak, which is 540 v, assures a reliable operation of the stp5nk60zfp with a good margin against the maximum bv dss . reduced load - terrestrial dvb (without lnb) note: all voltages are within tolerance. table 7. output voltages measurement at v in = 184 v and reduced load v out [v] 3.38 5.11 11.92 17.19 24.26 32.2 -26.83 v in [v rms ] 184 ? v out % +2.42 +2.2 -0.6 +7.4 +5.4 -2.4 +7.32 i out [a] 3.5 1.9 0.8 - 0.003 (1) 1. with a 8.2 k ? 1/4 w dummy load 0.01 0.15 i in [a rms ] 0.531 p out [w] 11.83 9.7 9.54 - 0.072 0.32 4 p in [w] 52.6 p outtot [w] 35.5 (%) 67.5 f s [khz] 63.5
AN2600 test description 15/30 note: all voltages are within tolerance. note: all voltages are within tolerance ta bl e 7 , 8 and 9 show the output voltage measured applying the same loads that we could have if a different dvb type is powered (e.g. a terrestrial or cable) without the lnb. as under the load condition described before, all the output voltages are within the tolerances. to keep the 23 v lnb output within the tolerance, a negligible dummy load has to be connected on this output. figure 7. v ds and i d of stp5nk60z at reduced load v in = 184 v rms - 50 hz table 8. output voltages measurement at v in = 230 v and reduced load v out [v] 3.39 5.09 11.92 17.15 24.21 32.2 -26.7 v in [v rms ] 230 ? v out % +2.72 +1.8 -0.6 +7.18 +5.26 -2.4 +6.8 i out [a] 3.5 1.9 0.8 - 0.003 (1) 1. with a 8.2 k ? 1/4 w dummy load 0.01 0.15 i in [a rms ] 0.448 p out [w] 11.86 9.67 9.54 - 0.072 0.32 4 p in [w] 52.3 p outtot [w] 35.47 (%) 67.8 f s [khz] 62.2 table 9. output voltages measurement at v in = 276 v and reduced load v out [v] 3.37 5.1 11.92 17.16 24.2 32.24 -26.82 v in [v rms ] 276 ? v out % +2.12 +2 -0.6 +7.2 +5.2 -2.3 +7.28 i out [a] 3.5 1.9 0.8 - 0.003 (1) 1. with a 8.2 k ? 1/4 w dummy load 0.01 0.15 i in [a rms ] 0.396 p out [w] 11.79 9.69 9.54 - 0.072 0.32 4.1 p in [w] 52.3 p outtot [w] 35.5 (%) 67.9 f s [khz] 61
test description AN2600 16/30 figure 8. v ds and i d of stp5nk60z at reduced load v in = 230 v rms - 50 hz figure 9. v ds and i d of stp5nk60z at reduced load v in = 276 v rms - 50 hz note: ch1: drain voltage (brown) ch2: drain current (blue) v in (v ac ): 184 - 230 - 276 v dsmax (v): 400 - 460 - 528 i dpk (a): 1.46 - 1.46 - 1.46 the measured values are the drain peak voltage and current at minimum, nominal and maximum input mains voltage, during normal operation at full load. the voltage peak, which is 528 v, assures a reliable operation of the stp5nk60z with a good margin against the maximum bv dss .
AN2600 test description 17/30 reduced load - total power = 20 w even still reducing the load down to 20 w, than ks to the coupling of th e transformer, all the output voltages are well regulated. the tables above show that the switching frequency is decreased according to the power consumption. table 10. output voltages measurement at v in = 184 v and reduced load (20 w) v out [v] 3.5 5 12 16.56 23.01 32.15 -26.2 v in [v rms ] 184 ? v out % +6 +0 +0 +3.5 +0 -2.5 +4.8 i out [a] 1.75 1 0.4 - 0.003 (1) 1. with a 8.2 k ? 1/4 w dummy load 0.01 0.15 i in [a rms ] 0.301 p out [w] 6.125 5 4.8 - 0.07 0.32 3.93 p in [w] 28.3 p outtot [w] 20.2 (%) 71.4 f s [khz] 53.8 table 11. output voltages measurement at v in = 230 v and reduced load (20 w) v out [v] 3.5 5 11.98 16.57 23.03 32.1 -26.2 v in [v rms ] 230 ? v out % +6 +0 -0.16 +3.6 +0.1 -2.72 +4.8 i out [a] 1.75 1 0.4 - 0.003 (1) 1. with a 8.2 k ? 1/4 w dummy load 0.01 0.15 i in [a rms ] 0.256 p out [w] 6.125 5 4.79 - 0.07 0.32 3.93 p in [w] 28.35 p outtot [w] 20.2 (%) 71.4 f s [khz] 52 table 12. output voltages measurement at v in = 276 v and reduced load (20 w) v out [v] 3.5 5.04 11.98 16.59 23.04 32.17 -26.2 v in [v rms ] 276 ? v out % +6 +0.8 -0.16 +3.7 +0.1 -2.5 +4.8 i out [a] 1.75 1 0.4 - 0.003 (1) 1. with a 8.2 k ? 1/4 w dummy load 0.01 0.15 i in [a rms ] 0.225 p out [w] 6.125 5.04 4.79 - 0.07 0.32 3.93 p in [w] 28.3 p outtot [w] 20.2 (%) 71.4 f s [khz] 50
test description AN2600 18/30 figure 10. v ds and i d of stp5nk60z at reduced load (20 w) v in = 184 v rms - 50 hz figure 11. v ds and i d of stp5nk60z at reduced load (20 w) v in = 230 v rms - 50 hz
AN2600 test description 19/30 figure 12. v ds and i d of stp5nk60z at reduced load (20 w) v in = 276 v rms - 50 hz note: ch1: drain voltage (brown) ch2: drain current (blue) v in (v ac ): 184 - 230 - 276 v dsmax (v): 376 - 440 - 508 i dpk (a): 1.16 - 1.18 - 1.18 the measured values are the drain peak voltage and current at minimum, nominal and maximum input mains voltage, during normal operation at full load. the voltage peak, which is 508 v, assures a reliable operation of the stp5nk60z with a good margin against the maximum bv dss . light load table 13. output voltages measurement at v in = 230 v and light load v out [v] 3.58 5.25 12 16.52 22.65 32 -25.74 v in [v rms ] 230 i out [a] 0.8 0.08 0.08 - 0.003 (1) 1. with a 8.2 k ? 1/4 w dummy load 0.01 0.15 i in [a rms ] 0.114 p out [w] 2.86 0.42 0.96 - 0.07 0.32 3.93 p in [w] 11.3 p outtot [w] 8.56 (%) 75.7 f s [khz] burst mode
test description AN2600 20/30 figure 13. v ds and i d of stp5nk60z at light load at 230 v also in this load condition the circuit is still able to maintain all voltages under control, hence a perfect functionality of the circuit is achieved also in this abnormal condition. during light load operation the circuit works in burst mode and, thanks to the controller functionality, the switching frequency inside the burst pulses is kept low. this allows low power consumption of the power supply under light load. 3.2 high frequency ripple of output voltages at full load the output voltage ripple at switching frequency has been measured, as listed in ta bl e 1 4 . in figure 14 the waveforms of the voltage ripple are shown. ch1: drain voltage (brown) ch2: drain current (blue) table 14. measurement of high frequency ripple of output voltages at v in = 230 v and full load v out [v] 3.3 5 12 16 23 33 -25 ? v outhf [mv] 11 6 4.8 46 36 29 43
AN2600 test description 21/30 figure 14. high frequency ripple of output voltages at full load at 230 v 3.3 measurement of rms curre nt of output capacitors ta bl e 1 5 shows the rms current values flowing into the output capacitors at 230v ac , full load. all the rms currents are within the rating of the capacitor type indicated. this avoids any component overstress that co uld affect the reliability and the expected lifetime of the smps. 3.4 dynamic load test the dynamic load tests have been performed by varying the load on 3.3 v and 5 v outputs, keeping the other outputs at full load. varying the load on 3.3 v output, the following results have been obtained: ch1: +23 v out (brown) ch2: +16 v out (blue) ch3: +12 v out (purple) ch4: +5 v out (green) ch1: -25 v out (brown) ch3: +33 v out (purple) ch4: +3.3 v out (green) table 15. measurement of rms current of output capacitors at v in = 230 v and full load i capc77 (16v out )i capc91 (3.3v out )i capc81 (23v out )i capc102 (5v out ) 0.850 1.9 0.550 1
test description AN2600 22/30 figure 15. outputs behavior under dynamic load on 3.3 v output at v in =230 v varying the load on 5 v output, the following results have been obtained: table 16. dynamic load test on 3.3 v out outputs load condition +5 v, +12 v, +16 v, +23 v, +33 v, -25 v full load +3.3 v load 50% 90% table 17. dynamic load test on 5 v out outputs load condition +3.3 v, +12 v, +16 v, +23 v, +33 v, -25 v full load +5 v load 50% 90% ch2: +3v3 i out (blue) ch4: +3v3 v out (green) ch1: +23 v out (brown) ch2: +16 v out (blue) ch4: +5 v out (green)
AN2600 test description 23/30 figure 16. behavior of outputs with dynamic load applied to 5 v output at v in =230 v the worst case condition happens when the 3.3 v output load is increased from 50% to 90% of full load value. 3.5 startup behavior figure 17 , 18 , 19 show the rise slopes at full load of the output voltage at nominal, minimum and maximum input voltage. as shown in the graphs, the rise times are almost constant. ch2: +5 v i out (blue) ch4: +5 v v out (green) ch1: +23 v out (brown) ch2: +16 v out (blue) ch4: +3.3 v out (green)
test description AN2600 24/30 figure 17. startup behavior of the system at v in = 184 v rms - 50 hz figure 18. startup behavior of the system at v in = 230 v rms - 50 hz
AN2600 test description 25/30 figure 19. startup behavior of the system at v in = 276 v rms - 50 hz note: ch1: +23 v out (brown) ch2: +16 v out (blue) ch3: +12 v out (purple) ch4: +5 v out (green) ta bl e 1 8 lists the overshoot for the most significant outputs at startup, giving the performances of the power supply in terms of stability. all voltages are well controlled. table 18. overshoot v in (v ac )23 v out (%) 16 v out (%) 12 v out (%) 5 v out (%) 184 5 4.2 0.8 5.1 230 3.6 2.6 0.6 3.7 276 4.2 3.5 0.9 4.7
test description AN2600 26/30 3.6 wakeup time figure 20 , 21 , 22 show the waveforms at startup with the wakeup time measurement at the minimum, nominal at maximum input mains. obviously, due to the circuitry characteristics, the wakeup time is constant and independent from the input voltage. the measured value is about 0.9 s, according to the ic startup high voltage current generator. figure 20. wakeup behavior of the system at v in = 184 v rms - 50 hz figure 21. wakeup behavior of the system at v in = 230 v rms - 50 hz
AN2600 test description 27/30 figure 22. wakeup behavior of the system at v in = 276 v rms - 50 hz note: ch1: drain voltage (brown) ch2: drain current (blue) ch4: +3.3 v out v in (v ac ): 184 - 230 - 276 v dsmax (v): 335 - 401 - 465 i dpk : 2.25 - 2.2 - 2.16 3.7 short circuit test the short circuit tests have been performed on the two regulated voltages. the short circuit has been provided by means of the electronic l oad, which is able to emulate the "soft" short circuit that could happen on the stb main board. the tests have been done at nominal input voltage with all outputs at full load. the protection against short circuit on the +12 v is given by the protection of the voltage regulator. figure 23. short circuit on 5 v output ch1: drain voltage (yellow) ch2: vcc voltage (blue) ch3: 5 v out (purple) ch4: drain current (purple)
test description AN2600 28/30 as the coupling betwee n the 3.3 v and the auxiliary winding s is poor, to help the smps to enter hiccup mode in case of 3.3 v output shorted, the circuitry based on q10 and q11 has been added. 3.8 conducted emission (emi) measurements conducted emissions measurements at full load and nominal mains voltage have been performed, using a 50 ? lisn and a spectrum analyzer with peak detector as shown in figure 24 and 25 . the emissions are below the limits given by the en55022 standard for class b equipment. as the margin between the limits and emission is acceptable, the power supply is ready for the final compliance test. 3.9 thermal measurements in order to check the reliability of the design , thermal measurements using a thermocouple have been performed. ta bl e 1 9 and ta bl e 2 0 list the thermal measurements at nominal input voltage at ambient temperature (25 c) for the most critical components under full load. figure 24. conducted emissions of the system at full load and v in =230 v - phase conducted emission figure 25. conducted emissions of the system at full load and v in =230 v - neutral conducted emission 02:30:30 nov 14, 2006 ref 75 db v# atten 10 db peak log 10 db/ w1 s2 s3 fc aa start 150 khz res bw 9 khz vbw 30 khz stop 30 mhz sweep 881.3 ms (1515 pts) 02:31:12 nov 14, 2006 ref 75 db v# atten 10 db peak log 10 db/ w1 s2 s3 fc aa start 150 khz res bw 9 khz vbw 30 khz stop 30 mhz sweep 881.3 ms (1515 pts) table 19. thermal behavior of the components at primary side stp5nk60zfp case (c) stp5nk60zfp heatsink (c) trafo core (c) trafo windings (c) snubber resistor (c) after 30 min6657435060 after 1 hour7263495065
AN2600 conclusions 29/30 4 conclusions a 55 w smps for terrestrial and satellite dvb based on 710 0 chipset has been designed and fully validated, resulting in an efficient, reliable, and cost-effective system. the power supply is based on the l6668 controller with integrated high voltage startup circuit, which provides high efficiency also in standby and light load conditions, thanks to its dedicated functions related to "stby" and "skipadj" pins. 5 revision history table 20. thermal behavior of the components at secondary side d55 case (c) d54 case (c) u5 case (c) u5 heatsink (c) c102 (c) after 30 min586979 64 61 after 1 hour 63 71 81 68 65 table 21. document revision history date revision changes 17-jan-2008 1 initial release
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