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january 2014 docid15099 rev 2 1/23 AN2838 application note 35 w wide-range high power factor flyback converter evaluation board using the l6562a introduction this application note describes a product eval uation board based on the transition-mode pfc controller l6562a, and presents the results of its bench demonstration. the board is a 35 w, wide-range mains input, power factor corrected smps (switched mode power supply) suitable for all low power applications requiring a high pf (power factor), such as lighting applications and power supplies for leds. the low-cost l6562a and the simple flyback topology combine to provide a very competitive pfc controller solution. figure 1. evl6562a-35wflb evaluation board using the l6562a www.st.com
contents AN2838 2/23 docid15099 rev 2 contents 1 main characteristics and circ uit description . . . . . . . . . . . . . . . . . . . . . 4 2 electrical diagram and bi ll of material . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3 test results and significant wavef orms . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.1 harmonic content measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4 thermal measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 5 conducted emission pre-compliance test . . . . . . . . . . . . . . . . . . . . . . 15 6 burst test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 7 schematic with output volt age and current loop . . . . . . . . . . . . . . . . . 18 8 power transformer specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 9 references . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 10 revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
docid15099 rev 2 3/23 AN2838 list of figures 23 list of figures figure 1. evl6562a-35wflb evaluation board using the l6562a . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 figure 2. evl6562a-35wflb evaluation board: electrical schem atic . . . . . . . . . . . . . . . . . . . . . . . . 6 figure 3. evl6562a-35wflb compliance with en61000-3- 2 class-c limits @ full load . . . . . . . . . . 9 figure 4. evl6562a-35wflb compliance with jeida-miti class-c limits @ full load . . . . . . . . . . . 9 figure 5. power factor vs. v in and load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 figure 6. evl6562a-35wflb input current waveform @100 v-50 hz - 35 w load . . . . . . . . . . . . . 10 figure 7. evl6562a-35wflb input current waveform @230 v-50 hz - 35 w load . . . . . . . . . . . . . 10 figure 8. efficiency vs. v in and load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 figure 9. static v out regulation vs. v in and i out . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 figure 10. evl6562a-35wflb output voltage ripple @ 90 v ac - full load . . . . . . . . . . . . . . . . . . . . . 11 figure 11. evl6562a-35wflb output voltage ripple @ 265 v ac - full load . . . . . . . . . . . . . . . . . . . . 11 figure 12. evl6562a-35wflb v ds and i d @ 90 v ac - full load . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 figure 13. evl6562a-35wflb v ds and i d @ 90 v ac - full load - detail. . . . . . . . . . . . . . . . . . . . . . . 11 figure 14. evl6562a-35wflb v ds and i d @ 265 v ac - full load . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 figure 15. evl6562a-35wflb v ds and i d @ 265 v ac - full load - detail. . . . . . . . . . . . . . . . . . . . . . 12 figure 16. evl6562a-35wflb v ds and i d @ 90 v ac - 40 ma . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 figure 17. evl6562a-35wflb v ds and i d @ 90 v ac - 40 ma - detail. . . . . . . . . . . . . . . . . . . . . . . . 12 figure 18. evl6562a-35wflb v ds and i d @ 265 v ac - 40 ma . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 figure 19. evl6562a-35wflb v ds and i d @ 265 v ac - 40 ma - detail . . . . . . . . . . . . . . . . . . . . . . 13 figure 20. thermal map at 90 v ac - full load. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 figure 21. thermal map at 265 v ac - full load. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 figure 22. 115 v ac and full load - phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 figure 23. 115 v ac and full load - neutral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 figure 24. 230 v ac and full load - phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 figure 25. 230 v ac and full load - neutral . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 figure 26. burst pulse and characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 figure 27. electrical schematic with secondary current feedba ck . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 figure 28. power transformer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
main characteristics and circuit description AN2838 4/23 docid15099 rev 2 1 main characteristics and circuit description the main characteristics of the smps evaluation board are: ? line voltage range: 90 to 265 v ac ? minimum line frequency (f l ): 47-63 hz ? regulated output voltage: 48 v ? rated output power: 35 w ? power factor (load = 50 %): 0.9 minimum ? minimum efficiency: 85 % at full load ? maximum 2 f l output voltage ripple: 1.5 v pk-pk / 0.39 v rms (@v in = 90 v ac , p out = 35 w) ? maximum ambient temperature: 50 c ? conducted emi: in acc. with en55022 class-b ? surge rejection: surge test 2.5 kv ? primary to secondary insulation: 4 kv ? pcb type and size: double-sided, 35 m, fr-4, 120 x 82 mm the main feature of this converte r is that the input current is almost in phase with the mains voltage, therefore the power factor is close to unity. this is achieved by the l6562a controller, which shapes the input current as a sinewave in phase with the mains voltage. the power supply utilizes a typical flyback converter topology, us ing a transformer to provide the required insulation between the primary and secondary side. the converter is connected after the mains rectifier and the capacito r filter, which in this case is quite small to avoid damage to the shape of the input current. the flyback switch is represented by the power mosfet q1, and driven by the l6562a. at startup, the l6562a is powered by the v cc capacitor (c6), which is charged via resistors r1 and r2. the tr1 auxiliary win ding (pins 8-7) generates the v cc voltage, rectified by d4 and r4, that powers the l6562a during normal operation. r3 is also connected to the auxiliary winding to provide th e transformer demagnet ization signal to the l6562a zcd pin, turning on the mosfet at any switching cycl e. the mosfet used is the stp5nk80zfp, a standard, low-cost 800 v device housed in a to -220fp package, and needing only a small heat sink. the transformer is layer type, using a standard ferrite size etd-29 and is manufactured by magnetica. the flyback refl ected voltage is ~190 v, providing enough room for the leakage inductance voltage spik e still within the reliability margin of the mosfet. the rectifier d2 and the transil d3 clamp the peak of the leakage inductance voltage spike at mosfet turn-off. the resistors r14 and r15 sense the current flowing into the transformer primary side. once the signal at the current sense pin has reached the level programmed by the internal multiplier of the l6562a, the mosfet turns off. the divider r7, r8, r9 and r6 provides to the l6562a multiplier pin with instantaneous voltage information which is us ed to modulate th e current flowing in to the transformer primary side. the divider r20 and r21 is dedicated to sensing the output voltage, and capacitor c16 and diodes d7 and d8 provide a soft-start at turn-o n. output regulation is done by means of an
docid15099 rev 2 5/23 AN2838 main characteristics and circuit description 23 isolated voltage loop by the optocoupler u2, and using an inexpensive tl431 (u3) to drive the optocoupler. the opto-transistor modulate s the input voltage of the l6562a internal amplifier, thus closing the voltage loop. the output rectifier is a fast recovery type, selected acco rding to its maximum reverse voltage, forward voltage drop and power dissipation. a small lc filter is added on the output, filtering the high frequency ripple. the board is equipped with an input emi filter designed for a 3-wire input mains plug. it is composed of two, common mode pi-filter st ages connected after the input connector and the input fuse. a varistor is also connected at the input of the board, improving immunity against input voltage fast transients.
electrical diagram and bill of material AN2838 6/23 docid15099 rev 2 2 electrical diagram and bill of material figure 2. evl6562a-35wflb evalua tion board: electrical schematic
docid15099 rev 2 7/23 AN2838 electrical diagram and bill of material 23 table 1. bill of material reference part value type/description supplier c1 2.2 nf ceramic y2 murata c2 2.2 nf ceramic y2 murata c3 0.22 f r.46 275 v ac arcotronics c4 0.1 f r.41 mkp y2/x1 300 v ac n.d. c5 220 nf mkt x2 275 v ac n.d. c6 47 f 35 v n.d. c7 100 nf ceramic n.d. c8 2.2 nf ceramic n.d. c9 2.2 nf ceramic n.d. c10 1 nf ceramic y2 murata c11 1 nf ceramic y2 murata c12 1000 f 63 v 105 c yxf rubycon c13 1000 f 63 v 105 c yxf rubycon c14 100 nf ceramic n.d. c15 2200 nf ceramic n.d. c16 1 f 100 v n.d. c17 4.7 f 63 v 105c rubycon c18 0.1 f r.41 mkp y2/x1 300 v ac n.d. c19 2.2 nf ceramic y2 murata c20 2.2 nf ceramic y2 murata c21 2.2 nf ceramic y2 murata c22 2.2 nf ceramic y2 murata c23 100 nf ceramic n.d. c24 100 nf ceramic n.d. d1 800 v, 2 a 2kbp08m diode bridge n.d. d2 p6ke300a transil stmicroelectronics d3 stth1l06 rectifier, ultra-fast 1 a, 600 v stmicroelectronics d4 1n4448 n.d. d5 stth3r02 rectifier, ultra-fast 3 a, 200 v stmicroelectronics d6 33 v zener, 5% n.d. d7 1n4448 n.d. d8 1n4448 n.d. d9 n.m. not mounted n.d. f1 2 a, 250 v fuse pcb mounting n.d.
electrical diagram and bill of material AN2838 8/23 docid15099 rev 2 reference part value type/description supplier l1 4135 filter inductor 15 h/3 a magnetica q1 stp5nk80zfp power mosfet, to-220fp w/heatsink stmicroelectronics r1 150 k axial n.d. r2 150 k axial n.d. r3 68 k axial n.d. r4 10 r axial n.d. r5 680 k axial n.d. r6 20 k axial n.d. r7 1 m axial n.d. r8 1 m axial n.d. r9 1 m axial n.d. r10 0 r shorted n.d. r11 47 k axial n.d. r12 2.2 k axial n.d. r13 10 axial n.d. r14 1r0 axial, precision 5%, ? w n.d. r15 1r0 axial, precision 5%, ? w n.d. r16 12k axial n.d. r17 3k3 axial, ? w n.d. r18 6.8 k axial n.d. r19 4.7 k axial n.d. r20 1k5 axial, precision 1% n.d. r21 27 k axial, precision 1% n.d. r23 100 k axial n.d. r24 n.m not mounted n.d. r25 0r shorted t1 3651 common mode choke 2x18 mh magnetica t2 3651 common mode choke 2x18 mh magnetica tr1 4126 switch-mode transformer magnetica u1 l6562a tm pfc controller stmicroelectronics u2 cny17-3 optocoupler dip-6 n.d. u3 tl431 voltage reference, to-92 stmicroelectronics v1 275 v vdr 40j (10/1000 s) 7 mm n.d. table 1. bill of material (continued)
docid15099 rev 2 9/23 AN2838 test results and significant waveforms 23 3 test results and significant waveforms 3.1 harmonic content measurement one of the main purposes of this converter is the correction of input current distortion, decreasing the harmonic contents below the limit s of the actual regulation. therefore, the board has been tested according to the european standard en61000-3-2 class-c and japanese standard jeida-miti class-c, at full load and both nominal input voltage mains. as shown in figures that follow, the circuit is capable of reducing the harmonics well below the limits of both regulations. the power factor (pf) has been measured also and the results are reported in figure 5 . as shown, the pf remains very close to unity throughout the input voltage mains range. the waveforms of the input current and voltage at the nominal input voltage mains and full load condition ar e illustrated in figure 6 and figure 7 . figure 3. evl6562a-35wflb compliance with en61000-3-2 class-c limits @ full load figure 4. evl6562a-35wflb compliance with jeida-miti class-c limits @ full load figure 5. power factor vs. v in and load
test results and significant waveforms AN2838 10/23 docid15099 rev 2 the converter?s efficiency has been measured and it is significantly high in all load and line conditions (see figure 8 ). at full load, the efficiency is higher than 85% at any input voltage, making this design suitable for high efficiency power supplies. also, at lower output load the efficiency is better than 82%. at minimum load (40 ma output current) the efficiency is still good. figure 9 reports the output voltage measured unde r different line and load conditions. as shown, the voltage regulation over the entire input voltage range is excellent at any output current level. figure 6. evl6562a-35wflb input current waveform @100 v-50 hz - 35 w load figure 7. evl6562a-35wflb input current waveform @230 v-50 hz - 35 w load figure 8. efficiency vs. v in and load figure 9. static v out regulation vs. v in and i out
docid15099 rev 2 11/23 AN2838 test results and significant waveforms 23 in figure 10 and figure 11 the output voltage ripple at twice the input mains frequency is measured. as shown it is less than 0.4 v p eak-to-peak, which is ideal for led or lighting applications. high frequency no ise, including spikes, is si gnificantly reduced as well. in the following illustrations, the mosfet drain voltage a nd current are measured at different line and maximum loads. figure 10. evl6562a-35wflb output voltage ripple @ 90 v ac - full load figure 11. evl6562a-35wflb output voltage ripple @ 265 v ac - full load figure 12. evl6562a-35wflb v ds and i d @ 90 v ac - full load figure 13. evl6562a-35wflb v ds and i d @ 90 v ac - full load - detail ch1: drain current - 0.5 a/div ch1: drain current - 0.5 a/div ch2: drain voltage - 200 v/div ch2: drain voltage - 200 v/div
test results and significant waveforms AN2838 12/23 docid15099 rev 2 figure 14 shows the measurement at the maximum drain voltage of 265 v ac and max load. in this worst-case condition, the peak drain voltage is 640 v pk , assuring a good margin with respect to the mosfet bv dss and contributing strongly to th e reliability and low failure rate of the design. figure 14. evl6562a-35wflb v ds and i d @ 265 v ac - full load figure 15. evl6562a-35wflb v ds and i d @ 265 v ac - full load - detail ch1: drain current - 0.5 a/div ch1: drain current - 0.5 a/div ch2: drain voltage - 200 v/div ch2: drain voltage - 200 v/div figure 16. evl6562a-35wflb v ds and i d @ 90 v ac - 40 ma figure 17. evl6562a-35wflb v ds and i d @ 90 v ac - 40 ma - detail ch1: drain current - 0.1 a/div ch1: drain current - 0.1 a/div ch2: drain voltage - 100 v/div ch2: drain voltage - 100 v/div
docid15099 rev 2 13/23 AN2838 test results and significant waveforms 23 the above figures show the mosfet waveforms at light load. even in this load condition the waveforms are correct. it can be noted that at high mains the converter works in burst mode (see figure 19 ), keeping efficiency at a good level. figure 18. evl6562a-35wflb v ds and i d @ 265 v ac - 40 ma figure 19. evl6562a-35wflb v ds and i d @ 265 v ac - 40 ma - detail ch1: drain current - 0.2 a/div ch1: drain current - 0.2 a/div ch2: drain voltage - 200 v/div ch2: drain voltage - 200 v/div
thermal measurements AN2838 14/23 docid15099 rev 2 4 thermal measurements to check the reliability of the design, thermal mapping by means of an ir camera was carried out. figure 20 and figure 21 show thermal measurements on the component side of the board at nominal input voltages and full load. some pointers visible on the pictures placed across key components show the relevant temperature. table 1 provides the correlation between the measured points and components, for both thermal maps. the ambient temperature during both measur ements was 27 c. according to these measurement results, all components on the bo ard function within their temperature limits. figure 20. thermal map at 90 v ac - full load figure 21. thermal map at 265 v ac - full load table 2. measured temperature @ 90 v ac and 265 v ac - full load component temperature @ 90 v ac temperature @ 265 v ac mosfet q1 57.8 c 43.8 c secondary diode d5 58.9 c 58.1 c diode bridge d1 65.9 c 45.6 c transformer tr1 (bobbin) 64.3 c 65.1 c transformer tr1 (core) 54.5 c 55 c choke t1 55.7 c 36. 2 c choke t2 56 c 38.2 c transil d2 70 c 59 c
docid15099 rev 2 15/23 AN2838 conducted emission pre-compliance test 23 5 conducted emission pre-compliance test the following images are the peak measurements of the conducted noise at full load and nominal mains voltages. the limits shown on th e diagrams are those of en55022 class-b, which is the most popular standard for domestic equipment. as visible in the diagrams, good margins with respect to the limits are present in all test conditions. figure 22. 115 v ac and full load - phase figure 23. 115 v ac and full load - neutral figure 24. 230 v ac and full load - phase figure 25. 230 v ac and full load - neutral
burst test AN2838 16/23 docid15099 rev 2 6 burst test the board has been tested against burst pulses, with good results. the tests have been carried out using the following equipment and the procedures: ? surge generator: schaffner nsg 200 e 7 nsg 224 a ? test types: ? sym = symmetric with respect to earth pole (pulse applied between line and neutral) ? asym = asymmetric (pulse applied betw een line and earth and between neutral and earth) ? output load 700 ma. figure 26. burst pulse and characteristics table 3. burst test report table configuration amplitude polarity and phase pulse type pulse frequency pulse number (burst) pause pulse number (burst) pause pulse number (burst) pause pulse number (burst) pause sym 2.5 kv + 90 iii 1 hz 10 15? 10 15? 10 15? 10 15? 10 15? sym 2.5 kv - 270 iii 1 hz 10 15? 10 15? 10 15? 10 15? 10 15? asym 2.5 kv + 90 iii 1 hz 10 15? 10 15? 10 15? 10 15? 10 15? asym 2.5 kv - 270 iii 1 hz 10 15? 10 15? 10 15? 10 15? 10 15?
docid15099 rev 2 17/23 AN2838 burst test 23 ? test passed with a total of 200 pulses app lied and a medium energy of 80 mj (when connected to a 50 load).
schematic with output voltage and current loop AN2838 18/23 docid15099 rev 2 7 schematic with output voltage and current loop all tests described in this document have been done using the schematic in figure 1 and using a tl431 for the output voltage feedback. if a secondary current loop is also needed, the schematic below can be implemented on th e pcb by making the modifications listed in table 4 . the proposed schematic has been designed to dr ive leds with a current rating of 700 ma. for correct board functionality the minimum outp ut voltage when the current loop is working is around 30 v. therefore, the minimum number of leds in series that can be connected to the output must be calculated according to this minimum output voltage value. figure 27. electrical schematic with secondary current feedback
docid15099 rev 2 19/23 AN2838 schematic with output voltage and current loop 23 table 4. modification list for tsm1052 implementation reference part value modification type/ description c15 removed c16 100 nf changed value ceramic c25 2.2 nf added ceramic c26 220 nf added ceramic c27 10 nf added ceramic d6 12 v changed value zener, 5% r4 22 r changed value axial r16 10 k changed value axial r18 removed r19 removed r20 5k6 changed value axial, precision 1% r21 220 k changed value axial, precision 1% r25 0r27 added axial 2 w r26 100 k added axial r27 4k7 added axial r30 4k7 added axial r100 470r mounted by reworking of pcb axial j1 jumper added wire jumper u3 removed u4 tsm1052 stmicroelectronics added current/voltage controller
power transformer specification AN2838 20/23 docid15099 rev 2 8 power transformer specification ? transformer type: open ? winding type: layer ? coil former: vertical type, 6 + 6 pins ? mains insulation: 4 kv ? unit finishing: varnished electrical characteristics (all measuremen ts taken with pins 10 and 11 shorted) ? converter topology: flyback, tm mode ? core type: etd29 ? min. operating frequency: 36 khz ? primary inductance: 550 mh 10% @ 1 khz - 0.25 v (a) ? leakage inductance: 4.5 mh@ 50 khz - 0.25 v (b) ? parasitic capacitance: 7 pf max. ? max. peak primary current: 1.9 a pk ? turn ratio: ? pin 9-12 / 8-7: 10.55 5% ? pin 9-12 / 5/4-3/2: 3.8 5% figure 28. power transformer a. measured between pins (9-12) b. measured between pins (9-12) wi th all secondary windings shorted manufacturer: magnetica p/n: 4126
docid15099 rev 2 21/23 AN2838 references 23 9 references ? l6562a transition-mode pfc controller datasheet ? application note an1059: design equations of high-power-factor flyback converters based on the l6561 ? application note an1060: flyback converters with the l6561 pfc controller
revision history AN2838 22/23 docid15099 rev 2 10 revision history table 5. document revision history date revision changes 12-nov-2008 1 initial release 20-jan-2014 2 ? updated figure 2 , table 1 , figure 27 and chapter 8 ? modified board nomenclature
docid15099 rev 2 23/23 AN2838 23 please read carefully: information in this document is provided solely in connection with st products. stmicroelectronics nv and its subsidiaries (?st ?) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described he rein at any time, without notice. all st products are sold pursuant to st?s terms and conditions of sale. purchasers are solely responsible for the choice, selection and use of the st products and services described herein, and st as sumes no liability whatsoever relating to the choice, selection or use of the st products and services described herein. no license, express or implied, by estoppel or otherwise, to any intellectual property rights is granted under this document. i f any part of this document refers to any third party products or services it shall not be deemed a license grant by st for the use of such third party products or services, or any intellectual property contained therein or considered as a warranty covering the use in any manner whatsoev er of such third party products or services or any intellectual property contained therein. unless otherwise set forth in st?s terms and conditions of sale st disclaims any express or implied warranty with respect to the use and/or sale of st products including without limitation implied warranties of merchantability, fitness for a particul ar purpose (and their equivalents under the laws of any jurisdiction), or infringement of any patent, copyright or other intellectual property right. st products are not designed or authorized for use in: (a) safety critical applications such as life supporting, active implanted devices or systems with product functional safety requirements; (b) aeronautic applications; (c) automotive applications or environments, and/or (d) aerospace applications or environments. where st products are not designed for such use, the purchaser shall use products at purchaser?s sole risk, even if st has been informed in writing of such usage, unless a product is expressly designated by st as being intended for ? automotive, automotive safe ty or medical? industry domains according to st product design specifications. products formally escc, qml or jan qualified are deemed suitable for use in aerospace by the corresponding governmental agency. resale of st products with provisions different from the statements and/or technical features set forth in this document shall immediately void any warranty granted by st for the st product or service described herein and shall not create or extend in any manner whatsoev er, any liability of st. st and the st logo are trademarks or registered trademarks of st in various countries. information in this document supersedes and replaces all information previously supplied. the st logo is a registered trademark of stmicroelectronics. all other names are the property of their respective owners. ? 2014 stmicroelectronics - all rights reserved stmicroelectronics group of companies australia - belgium - brazil - canada - china - czech republic - finland - france - germany - hong kong - india - israel - ital y - japan - malaysia - malta - morocco - philippines - singapore - spain - sweden - switzerland - united kingdom - united states of america www.st.com

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