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august 2009 doc id 15327 rev 2 1/43 um0670 user manual 80 w offline led driver with pfc 1 introduction the use of high power leds in lighting applications is becoming increasingly popular due to rapid improvements in lighting efficiency, l onger life, higher reliability and overall cost effectiveness. dimming functions are more easily implemented in leds, and they are more robust and offer wider design flexibility compared to other light sources. for this reason a demonstration board for driving high brightness and power leds has been developed. the STEVAL-ILL013V1 demonstration board is an 80 w offline dimmable led driver with high power factor (pf) intended for fixed number of leds, the overall design of which is described in detail in this user manual. the led current can be set to 350 ma, 700 ma and 1000 ma, using jumpers. additionally, a dimming function using a pwm (pulse width modulation) signal is implemented as well, allowing the user to set the led brightness from 0% up to 100%. the demonstration board can be ordered using order code STEVAL-ILL013V1, and is shown in figure 1 . STEVAL-ILL013V1 main features 80 w led driver 350 ma, 700 ma and 1 a led current settings high efficiency (~90%) wide input voltage range: 88 to 265 vac high power factor: 0.99 for 110 vac and 0.98 for 230 vac universal pwm input for dimming (external board required) non-isolated smps brightness regulation between 0% and 100% emi filter implemented en55015 and en61000-3-2 compliant figure 1. STEVAL-ILL013V1 demonstration board www.st.com
contents um0670 2/43 doc id 15327 rev 2 contents 1 introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 getting started . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3 design concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4 STEVAL-ILL013V1 technical details . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5 schematic diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 6 bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 7 STEVAL-ILL013V1 performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 8 dimming function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 9 measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 9.1 output waveform measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 9.2 power mosfet turn on and off time . . . . . . . . . . . . . . . . . . . . . . . . . . 22 9.3 led current ripple reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 9.4 standard en61000-3-2 measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 9.5 emi measurement (en55015) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 10 design features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 10.1 proper startup circuit design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 10.2 zero dimming design implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 11 references and related materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 appendix a design calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 a.1 design specifications for a modified buck convertor . . . . . . . . . . . . . . . . . 37 12 revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
um0670 list of tables doc id 15327 rev 2 3/43 list of tables table 1. led values for different output currents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 table 2. output led current adjustment on the demonstration board . . . . . . . . . . . . . . . . . . . . . . . . 5 table 3. STEVAL-ILL013V1 demonstration boar d bill of material . . . . . . . . . . . . . . . . . . . . . . . . . . 12 table 4. document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
um0670 list of figures doc id 15327 rev 2 4/43 list of figures figure 1. STEVAL-ILL013V1 demonstration board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 figure 2. STEVAL-ILL013V1 block schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 figure 3. high pf boost converter design concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 figure 4. modified buck converter with dimming design concept. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 figure 5. STEVAL-ILL013V1 with pwm module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 figure 6. high pfc boost converter with the l6562a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 figure 7. modified buck converter with the l6562a . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 figure 8. efficiency over the whole input voltage range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 figure 9. power factor for wide input voltage range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 figure 10. detailed power factor for wide input voltage range. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 figure 11. total harmonic distortion for wide input voltage range . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 figure 12. output led current dimming capability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 8 figure 13. output led current waveform (i led = 350 ma) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 figure 14. output led current for different led voltages (i led = 350 ma). . . . . . . . . . . . . . . . . . . . . 20 figure 15. output led current waveforms (i led = 700 ma) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 figure 16. output led current for different led voltage (i led = 700 ma). . . . . . . . . . . . . . . . . . . . . . 21 figure 17. output led current waveform (i led = 1000 ma) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 figure 18. output led current for different led voltage (i led = 1000 ma). . . . . . . . . . . . . . . . . . . . . 22 figure 19. power mosfet turn on and off measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22 figure 20. led current ripple for the 100 nf output capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 figure 21. en61000-3-2 analysis for led current of 350 ma and v in from 85 v to 160 vac . . . . . . 23 figure 22. en61000-3-2 analysis for led current of 350 ma and v in from 180 v to 265 vac . . . . . 24 figure 23. en61000-3-2 analysis for led current of 700 ma and v in from 85 v to 160 vac . . . . . . 24 figure 24. en61000-3-2 analysis for led current of 700 ma and v in from 180 v to 265 vac . . . . . 24 figure 25. en61000-3-2 analysis for led current of 1000 ma and v in from 85 v to 160 vac . . . . . 25 figure 26. en61000-3-2 analysis for led current of 1000 ma and v in from 180 v to 265 vac . . . . 25 figure 27. average limit measurement from 150 khz to 30 mhz (i led = 350 ma) . . . . . . . . . . . . . . . 26 figure 28. quasi-peak limit measurement from 9 khz to 150 khz (i led = 350 ma) . . . . . . . . . . . . . . 26 figure 29. quasi-peak limit measurement from 150 khz to 30 mhz (i led = 350 ma). . . . . . . . . . . . . 27 figure 30. average limit measurement from 150 khz to 30 mhz (i led = 700 ma) . . . . . . . . . . . . . . . 27 figure 31. quasi-peak limit measurement from 9 khz to 150 khz (i led = 700 ma) . . . . . . . . . . . . . . 28 figure 32. quasi-peak limit measurement from 150 khz to 30 mhz (i led = 700 ma). . . . . . . . . . . . . 28 figure 33. average limit measurement from 150 khz to 30 mhz (i led = 1000 ma) . . . . . . . . . . . . . . 29 figure 34. quasi-peak limit measurement from 9 khz to 150 khz (i led = 1000 ma) . . . . . . . . . . . . . 29 figure 35. quasi-peak limit measurement from 150 khz to 30 mhz (i led = 1000 ma). . . . . . . . . . . . 30 figure 36. average limit measurement from 150 khz to 30 mhz (i led = 0 ma) . . . . . . . . . . . . . . . . . 30 figure 37. quasi-peak limit measurement from 9 khz to 150 khz (i led = 0 ma) . . . . . . . . . . . . . . . . 31 figure 38. quasi-peak limit measurement from 150 khz to 30 mhz (i led = 0 ma). . . . . . . . . . . . . . . 31 figure 39. proper startup circuit design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 figure 40. proper startup using diode d104 and capacitor c110 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 figure 41. improper startup without using diode d104 and capacitor c110 . . . . . . . . . . . . . . . . . . . . 33 figure 42. design improvement allowing zero dimming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 figure 43. voltage on capacitor c110 and output bus voltage of 400 v . . . . . . . . . . . . . . . . . . . . . . . 35
getting started um0670 5/43 doc id 15327 rev 2 2 getting started this section is intended to help designers begin evaluating the board quickly, describing how the board should be connected with the load and how the jumpers adjust the output led current. as mentioned in the introduction, the board has a nominal output power of 80 w and the output led current can be set to 350 ma, 700 ma or 1 a. the leds are connected to one string. basically, this means if the led current is set to 350 ma, then the led voltage should be approximately 228 v in order to provide output power of 80 w. if the led current is set to 700 ma, then the led voltage should be around 114 v. finally, if the led current is set to 1 a, then the led voltage should be about 80 v. assuming that a high brightness led has (typically) a 3.5 v forward voltage drop, the number of leds for the 350 ma output current is 65, for the 700 ma output current it is 32 and for the output current of 1 a it is 23 (see ta ble 1 ). of course, designers must recalculate the number of leds in cases where the led has a forward voltage drop other than 3.5 v. if the output led voltage is different than that given in ta ble 1 , output led current precision will be influenced so is recommended that the total forward voltage drop across all the leds is as close as possible to the calculated output voltages shown in table 1 . connect the led string to the board using connector j2 or j3, being careful to observe the correct led polarity (anode + and cathode ?). set the output led current to 350 ma, 700 ma or 1 a, based on how many leds are connected to the output. the output led current is set using jumpers jp1, jp2, jp3 and jp4, in accordance with the connection settings specified in ta bl e 2 . it is not necessary to connect a dimming module with a pwm signal, because if the module is not used the led brightness is set to maximum level (100% brightness). finally, connect an input voltage to the demonstration board between 88 vac and 265 vac, and the le ds begin illuminating. note: the leds cannot be connected during operation, when the input voltage is connected to the demonstration board. this is because in this case the output capacitor c208 = 0.47 f is charged to 400 v and can cause uncontrolled peak led current. table 1. led values for different output currents output led current [ma] output led voltage [v] number of leds for forward voltage drop 3.5 v 350 228 65 700 114 32 1000 80 23 table 2. output led current adjustment on the demonstration board jumper 350 ma 700 ma 1000 ma jp1 not connected connected not connected jp2 not connected connected not connected jp3 not connected not connected connected jp4 not connected not connected connected
um0670 design concept doc id 15327 rev 2 6/43 3 design concept the STEVAL-ILL013V1 block schem atic is illustrated in figure 2 . as shown, the design is divided into two main topologies. the first is a high pf (power factor) boost converter, and the second is a modified buck converter. as an additional board, any external pwm generator can be used for led brightness regulation. if no pwm generator is connected to the STEVAL-ILL013V1, the led brightness is pre-adjusted to 100%. there are two main reasons the high pf boost converter is designed on the steval- ill013v1 demonstration board. the first is the requirement for lighting equipment with an input active power higher than 25 w to comply with standard en61000-3-2 (harmonic current distortion). thanks to the high pf converter, compliance to the standard is achieved with no difficulty. the second reason is that a high input voltage (in this case 400 v) is needed for the modified buck converter, because it is, in fact, a buck converter and thus the input voltage must be higher than the output voltage. the output led voltage can be up to 228 v, as was shown in ta ble 1 . an additional advantage of the high pf converter is its wide input voltage range. this allows the demonstration board to be used either in either the european or us markets. a more detailed description of the high pf boost converter is provided in the evl6562a-tm-80w data brief (see section 11: references and related materials : 1 ). the second converter is designed as a constant current source, as it ensures the best lighting performance from the leds. concerning the topology, the ?modified buck? has been chosen, ?modified? insofar as the power switch is connected to ground (instead of the high- side switch, as in a standard buck topology) and therefore it is easier to control the switch. the design uses a fot (fixed off-time) network, operating in ccm (continuous conduction mode) and thanks to this principle the overall solution is very simple and cost effective. all equations needed for proper modified buck converter design are described in application note an2928 (see section 11: references and related materials : 2 ). figure 2. STEVAL-ILL013V1 block schematic microcontroller st7liteu05 pf controller l6562a external pwm generator modified buck converter high power factor boost converter bright regulation stth1l06 stp8nm50fp v in = 88 v to 265 v ac input filter pf controller l6562a 400 v 80 w load stpsc806d stf9nm50n steval- ill013v1 am00400
design concept um0670 7/43 doc id 15327 rev 2 figure 3 illustrates a high pf boost converter design concept. two additional features are implemented in the application and these improvements are shown in the blue segments. the first improves circuit behavior during startup (see section 10.1 for a description) and the second allows the dimming of the led down to 0%, or no led brightness (description provided in section 10.2 ). figure 4 shows the design concept of a modified buck converter with a dimming function. the output led current is adjusted by setting the proper sense resistor size via the jumpers (to adjust maximum led current), together with the proper setting of the capacitor used in the fot network (adjust minimum led current). the external pwm generator provides a pwm signal between 0 and 100% for brightness regulation. this signal is connected through a diode to the current sense pin and allows control of led brightness. figure 3. high pf boost converter design concept am00413 v out = 400 v vc = 16 v supplying pwm generator with st7liteu05 supplying l6562a in modified buck converter gnd l6562a cs input emi filter proper startup allowing 0% dimming stth1l06 stp8nm50fp d104 c110 comp inv c107 zcd v cc mult gd v in = 88 v to 265 v ac
um0670 design concept doc id 15327 rev 2 8/43 figure 4. modified buck converter with dimming design concept gnd l6562a comp cs inv v in = 400 v generated by the first converter 80 w leds l78l33 iccclk st7liteu05 clkin reset ain2 v dd 350 ma 700 ma 1 a external module for brightness regulation icc programming pwm signal 0% to 100% fixed off-time network stpsc806d stf9nm50n additional board gd v cc vc = 16 v generated by the first converter am00414 nc v ss pwm mult zcd
STEVAL-ILL013V1 technical details um0670 9/43 doc id 15327 rev 2 4 STEVAL-ILL013V1 technical details 80 w led driver 350 ma, 700 ma and 1 a led current settings pf = 0.99 with v in = 110 v or pf = 0.98 with v in = 230 v thd (total harmonic distortion) = 4.6 and v in = 110 v or thd = 10.3 and v in = 230 v high pfc boost converter operating in transition mode modified buck converter working in ccm and using fot network switching frequency f = 125 khz / 350 ma (modified buck converter) switching frequency f = 69 khz / 700 ma (modified buck converter) switching frequency f = 55 khz / 1000 ma (modified buck converter) the same inductor and transformer core used (e25) supply voltage provided for external pwm generator board size: 130 mm x 60 mm x 27 mm optional external pwm generator (non isolated) full brightness if pwm generator is not connected two output connectors for leds high efficiency (~90%) wide input voltage range: 88 v to 265 vac brightness regulation between 0% and 100% emi filter implemented en55015 and en61000-3-2 tested figure 5. STEVAL-ILL013V1 with pwm module
um0670 schematic diagram doc id 15327 rev 2 10/43 5 schematic diagram figure 6. high pfc boost converter with the l6562a 400 v 16 v e 25 x 13 x 7 1.5 mm gap, n67 primary: 105 turns 2 x 0.3 mm secondary: 11 turns 1 x 0.3 mm c112 150 nf c103 220 nf r122 0 r120 15 k r111 0 r115 33 j1 c110 33 f r121 82 k tr1 cmc 2x 22 m 1 a h / r109 47 r102 1 m r101 1 m r106 270 k c109 12 nf q102 bux8 3 c113 47uf / 450 v d101 18 v r113 1 d104 r114 1 d103 stth1l06 r107 270 k inv 1 gd 7 comp 2 zcd 5 v cc 8 mult 3 gnd 6 cs 4 u101 l6562a c108 12 nf c102 470 nf c111 2200 nf r105 15 k r126 20 k 47 k r116 r108 47 c106 100 nf ntc 10 r112 1 5 10 1 6 2 3 7 8 9 t101 r127 20 k c104 220 nf r123 330 k r128 43 k f1 2 a 1 m r119 c107 10 f c101 1nf / y1 / 250 v ac c101 r118 1 m br1 d102 r124 330 k 2 4 3 1 q101 stp8nm50fp heatsink r125 330 k r103 1 m r117 22 k r104 1 m c105 10nf r110 47 k am00402
schematic diagram um0670 11/43 doc id 15327 rev 2 figure 7. modified buck converter with the l6562a 16 v 400 v + + ? ? pwm dimming signal c206 1.5 nf / 63 v 1 2 jp4 2 1 3 4 5 6 7 8 9 10 j4 c208 0.47 f / 450 v r207 1 k d202 stpsc806d c207 330 pf r204 1.5 / 0.6 w 1 2 jp3 jumper jumper r208 47 k c204 390 pf / 63 v inv 1 gd 7 comp 2 zcd 5 v cc 8 mult 3 gnd 6 cs 4 u201 l6562a l201 / 172 turns 1.6 mh r206 2.2 / 0.6 w c205 820 pf / 63 v c201 22 f / 35 v 1 2 jp1 c202 100 nf r209 3.9 k r205 2.7 / 0.6 w 2 1 3 4 5 6 j3 2 1 j2 r203 3.9 k 2 4 3 1 q201 stf9nm50n heatsink r201 33 d201 1n4148 d204 1n4148 02 1 k r2 1 2 jp2 d203 stth1l06a c203 220 pf / 63v am00403 jumper jumper
um0670 bill of material doc id 15327 rev 2 12/43 6 bill of material table 3. STEVAL-ILL013V1 demonstration board bill of material (1) i q reference part note manufacturer order code 1 1 j1 socket input socket 2 1 f1 fuse 2.5 a / 250 v 3 1 f1 fuse socket socket 41ntc 10 ntc thermistor epcos b57235s100m 5 1 tr1 2 x 22 mh / 1 a common mode choke epcos b82732r2102b030 6 1 br1 1 a / 250 v diode bridge 7 1 c101 1 nf / 250 vac y1 capacitor murata manufacturing co., ltd. de1e3kx102ma5b 8 1 c102 470 nf / 265 vac x2 capacitor epcos b32922c3474k 9 2 c103, c104 220 nf / 265 vac x2 capacitor epcos b32922c3224m 10 1 c105 10 nf / 63 v smd capacitor 1206 11 2 c106, c202 100 nf / 63 v smd capacitor 1206 12 1 c107 10 f / 35 v electrolytic capacitor 13 2 c108, c109 12 nf / 63 v smd capacitor 1206 14 1 c110 33 f / 35 v electrolytic capacitor 15 1 c111 2200 nf / 25 v x7r smd 1206 ceramic capacitor avx 12063c225kat2a 16 1 c112 150 nf / 50 v smd capacitor 1206 17 1 c113 47 f / 450 v electrolytic capacitor epcos b43501a5476m000 18 1 d101 18 v / 0.5 w zener diode 19 4 d102, d104, d201, d204 1n4148 smd diode 20 1 d103 stth1l06u smb package stmicroelectronics stth1l06u 21 2 u101, u201 l6562a pfc controller stmicroelectronics l6562ad 22 4 r101, r102 r103, r104 1 m smd resistors 1206 23 1 r105 15 k smd resistors 1206 24 2 r106, r107 270 k smd resistors 1206 25 2 r108, r109 47 smd resistors 1206 26 3 r110, r116, r208 47 k smd resistors 1206 27 2 r111, r122 0 smd resistors 1206 28 3 r112, r113, r114 1 / 1% smd resistors 1206 29 2 r115, r201 33 smd resistors 1206
bill of material um0670 13/43 doc id 15327 rev 2 30 1 r117 22 k smd resistors 1206 31 2 r118, r119 1 m / 1% axial resistor 0.6 w / 1% 32 1 r120 15 k / 1% smd resistors 1206 33 1 r121 82 k / 1% smd resistors 1206 34 3 r123, r124 r125 330 k smd resistors 1206 35 2 r126, r127 20 k axial resistor 0.6 w 36 1 r128 43 k smd resistor 1206 37 1 t101 transformer e25/13/7 1.5 mm gap , n67 primary: 105 turns 2 x 0.3 secondary: 11 turns 1 x 0.3 38 1 q101 stp8nm50 power mosfet stmicroelectronics stp8nm50fp 39 1 q102 bux87 bipolar transistor stmicroelectronics bux87 40 2 heat sink heat sink for mosfets 41 2 r202, r207 1k smd resistors 1206 42 2 r203, r209 3900 smd resistors 1206 43 1 r204 1.5 / 0.6 w axial resistor 44 1 r205 2.7 / 0.6 w axial resistor 45 1 r206 2.2 / 0.6 w axial resistor 46 1 c201 22 f / 35 v electrolytic cap 47 1 c203 220 pf / 63 v smd capacitor 1206 48 1 c204 390 pf / 63 v smd capacitor 1206 49 1 c205 820 pf / 63 v smd capacitor 1206 50 1 c206 1.5 nf / 63 v smd capacitor 1206 51 1 c207 330 pf / 63 v smd capacitor 1206 52 1 c208 0.47 f / 450 v electrolytic capacitor epcos b43827a5474m000 53 1 d202 stpsc806d silicon carbide diode stmicroelectronics stpsc806d 54 1 d203 stth1l06a sma package stmicroelectronics stth1l06a 55 4 jp1, jp2 jp3, jp4 jumper two pin connector 56 2 jpj1, jpj2 jumper jumpers 57 1 j2 socket output socket 58 1 j3 socket output socket 59 1 j4 socket pwm socket 60 1 q201 stf9nm50n power mosfet stmicroelectronics stf9nm50n 61 1 l201 1.6 mh e25/13/7 2 mm gap n67, 172 turns 1 x 0.28 1. the power mosfet stf9nm50n can be replaced by stf10nm60n. table 3. STEVAL-ILL013V1 demonstration board bill of material (continued) (1) i q reference part note manufacturer order code
um0670 STEVAL-ILL013V1 performance doc id 15327 rev 2 14/43 7 STEVAL-ILL013V1 performance figure 8 shows the efficiency of the STEVAL-ILL013V1 (measured also with an external pwm generator) for the output led current 350 ma, 700 ma and 1 a, over the entire input voltage range. measured efficiency for the input voltage of 230 v was above 90% (90.49% for the 350 ma output led current, 90.53% for the 700 ma output led current, and 90.3% for the 1 a output led current) efficiency for the input voltage of 110 v was above 87% (88.05% for the 350 ma output led current, 88.2% for the 700 ma output led current and 87.37% for the output led current of 1 a). measured pf for the output led current of 350 ma, 700 ma and 1 a is shown in figure 9 and figure 10 . pf for the input voltage of 110 vac is 0.99, and 0.98 for the input voltage of 230 vac. thd is demonstrated in figure 11 , and as it can be observed is below 12% over the whole input voltage range. note: le uw e3b ostar ? leds from osram were used as the load (see section 11: references and related materials : 6. ). figure 8. efficiency over the whole input voltage range 0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00 85 100 110 120 140 160 180 200 220 230 240 265 input voltage [v] efficiency [%] 700 ma at 6 leds 350 ma at 12 leds 1 a at 4 leds am00395
STEVAL-ILL013V1 performance um0670 15/43 doc id 15327 rev 2 figure 9. power factor for wide input voltage range figure 10. detailed power factor for wide input voltage range 0 0.2 0.4 0.6 0.8 1 85 100 110 120 140 160 180 200 220 230 240 265 input voltage [v] power factor [-] 700 ma at 6 leds 350 ma at 12 leds 1 a at 4 leds am00397 0.95 0.96 0.97 0.98 0.99 1 85 100 110 120 140 160 180 200 220 230 240 265 input voltage [v] 700 ma at 6 leds 350 ma at 12 leds 1 a at 4 leds am00396 power factor [-]
um0670 STEVAL-ILL013V1 performance doc id 15327 rev 2 16/43 figure 11. total harmonic distortion for wide input voltage range 0.00 2.00 4.00 6.00 8.00 10.00 12.00 85 100 110 120 140 160 180 200 220 230 240 265 input voltage [v] thd [%] 700 ma at 6 leds 350 ma at 12 leds 1 a at 4 leds am00398
dimming function um0670 17/43 doc id 15327 rev 2 8 dimming function leds as a light source are very often used in applications where the brightness regulation is required. their biggest advantage is that their minimum brightness can be easily regulated by changing their current, and they are stable even at very low brightness. generally, there are two basic concepts regarding how the brightness is regulated. the first is called ?analog dimming?, which means that the brightness is regulated by changing the continuous forward led current. this concept is not used on the STEVAL-ILL013V1. the second solution is to use a low frequency (~200 hz) pwm signal and change the brightness by pulse width modulation. this is the approach used in the design of the STEVAL-ILL013V1. any external pwm generator can be used for brightness regulation, but it should be taken into account that the STEVAL-ILL013V1 is not isolated. in order to demonstrate the dimming function on the STEVAL-ILL013V1, an external pwm generator using stmicroelectronics? st7liteu05 microcontroller was connected to the board, and the output led current was measured. the microcontroller generates a pwm signal with a frequency of 250 hz. the duty cycle is set by a potentiometer from 0% up to 100%.the result with duty cycles of 50%, 10% and 2% is shown in figure 12 . the input voltage was, in this case, 230 vac and the output led current was set to 350 ma. it is also possible to achieve led brightness regulation below 2%. in this case the nominal led current is slightly decreased.
um0670 dimming function doc id 15327 rev 2 18/43 figure 12. output led current dimming capability
measurement um0670 19/43 doc id 15327 rev 2 9 measurement 9.1 output waveform measurement figure 13 shows the output led current waveform. the led current was set to 350 ma and, as shown, the current ripple is 92 ma and the switching frequency for the modified buck converter is 125 khz. the input voltage was 230 vac and 12 leds were used as the load (ostar led le uw e3b; see section 11: references and related materials 6 ). the output led current slightly varies with the output voltage, as explained in detail in application note an2928, ( section 11: references and related materials 2 ) and therefore this design is optimal for a fixed number of leds. the output led current accuracy for different led voltages is demonstrated in figure 14 . figure 13. output led current waveform (i led = 350 ma)
um0670 measurement doc id 15327 rev 2 20/43 figure 14. output led current for different led voltages (i led = 350 ma) figure 15 shows the output led current waveform for the led current of 700 ma. the current ripple is, in this case, 333 ma and the switching frequency for the modified buck converter is 69 khz. the input voltage was 230 ac and 6 leds were used as the load (ostar led le uw e3b see section 11: references and related materials : 6 ). the output led current accuracy for the different led voltages is shown in figure 16 . figure 15. output led current waveforms (i led = 700 ma) v led v s. i led for nominal led current 350 ma 0 50 100 150 200 250 300 350 400 450 174 193 211 230 250 led voltage [v] led current [ma] 350 ma am00399
measurement um0670 21/43 doc id 15327 rev 2 figure 16. output led current for different led voltage (i led = 700 ma) figure 17 shows the output led current waveform for the output led current of 1000 ma. the current ripple is 433 ma and the switching frequency for the modified buck converter is 55 khz. the input voltage was 230 vac and 4 leds were used as the load (ostar led le uw e3b see section 11: references and related materials : 6 ). the output led current accuracy for the different led voltages is shown in figure 18 . figure 17. output led current waveform (i led = 1000 ma) am00404 v led v s. i led for nominal led current 700 ma 0 100 200 300 400 500 600 700 800 82 101 121 139 led voltage [v] led current [ma] 700 ma
um0670 measurement doc id 15327 rev 2 22/43 figure 18. output led current for different led voltage (i led = 1000 ma) 9.2 power mosfet turn on and off time the power mosfet turn on and off time is shown in figure 19 . turn on time is approximately 50 ns and turn off time is approximately 120 ns (off time is used in equation 13 in the appendix). figure 19. power mosfet turn on and off measurement 9.3 led current ripple reduction the output led current ripple can be reduced by increasing the output capacitor size. for example, inductor current ripple is 400 ma for the 100 nf / 450 v output capacitor, as shown in figure 20 . thanks to the larger 470 nf capacitor used on the STEVAL-ILL013V1, the v led v s. i led for nominal led current 1 a 0 200 400 600 800 1000 1200 63 84 103 122 led voltage [v] led current [ma] 1 a am00405
measurement um0670 23/43 doc id 15327 rev 2 output current ripple is reduced to 92 ma (see figure 13 ). however, there are some limitations for the capacitors used in dimmable applications, as capacitors that are too large cause a decrease in dimming resolution (minimum duty cycle is limited). the 470 nf capacitor used on the STEVAL-ILL013V1 is a good compromise between lower output current ripple and good dimming resolution, as illustrated in figure 12 . figure 20. led current ripple for the 100 nf output capacitor 9.4 standard en61000-3-2 measurement figure 21. en61000-3-2 analysis for led current of 350 ma and v in from 85 v to 160 vac en61000-3-2 analysis for led current 350 ma at 12 leds v in from 85 v to 160 v ac 0 200 400 600 800 1000 1200 13579 13579 13579 13579 13579 13579 85 v 100 v 110 v 120 v 140 v 160 v current [ma] real limits am00406
um0670 measurement doc id 15327 rev 2 24/43 figure 22. en61000-3-2 analysis for led current of 350 ma and v in from 180 v to 265 vac figure 23. en61000-3-2 analysis for led current of 700 ma and v in from 85 v to 160 vac figure 24. en61000-3-2 analysis for led current of 700 ma and v in from 180 v to 265 vac en61000-3-2 analysis for led current 350 ma at 12 leds v in from 180 v to 265 v ac 0 100 200 300 400 500 600 13579 13579 13579 13579 13579 13579 180 v 200 v 220 v 230 v 240 v 260v current [ma] real limits am00407 en61000-3-2 analysis for led current 700 ma at 6 leds v in from 85 v to 160 v ac 0 200 400 600 800 1000 1200 13579 13579 13579 13579 13579 13579 85 v 100 v 110 v 120 v 140 v 160 v current [ma] real limits am00408 en61000-3-2 analysis for led current 700 ma at 6 leds v in from 180 v to 265 v ac 0 100 200 300 400 500 600 13579 13579 13579 13579 13579 13579 180 v 200 v 220 v 230 v 240 v 260 v current [ma] real limits am00409
measurement um0670 25/43 doc id 15327 rev 2 figure 25. en61000-3-2 analysis for led current of 1000 ma and v in from 85 v to 160 vac figure 26. en61000-3-2 analysis for led current of 1000 ma and v in from 180 v to 265 vac en61000-3-2 analysis for led current 1 a at 4 leds v in from 85 v to 160 v ac 0 200 400 600 800 1000 1200 13579 13579 13579 13579 13579 13579 85 v 100 v 110 v 120 v 140 v 160 v current [ma] real limits am00410 en61000-3-2 analysis for led current 1 a at 4 leds v in from 180 v to 265 v ac 0 100 200 300 400 500 600 13579 13579 13579 13579 13579 13579 180 v 200 v 220 v 230 v 240 v 260 v current [ma] real limits am00411
um0670 measurement doc id 15327 rev 2 26/43 9.5 emi measurement (en55015) figure 27. average limit measurement from 150 khz to 30 mhz (i led = 350 ma) figure 28. quasi-peak limit measurement from 9 khz to 150 khz (i led = 350 ma)
measurement um0670 27/43 doc id 15327 rev 2 figure 29. quasi-peak limit measurement from 150 khz to 30 mhz (i led = 350 ma) figure 30. average limit measurement from 150 khz to 30 mhz (i led = 700 ma)
um0670 measurement doc id 15327 rev 2 28/43 figure 31. quasi-peak limit measurement from 9 khz to 150 khz (i led = 700 ma) figure 32. quasi-peak limit measurement from 150 khz to 30 mhz (i led = 700 ma)
measurement um0670 29/43 doc id 15327 rev 2 figure 33. average limit measurement from 150 khz to 30 mhz (i led = 1000 ma) figure 34. quasi-peak limit measurement from 9 khz to 150 khz (i led = 1000 ma)
um0670 measurement doc id 15327 rev 2 30/43 figure 35. quasi-peak limit measurement from 150 khz to 30 mhz (i led = 1000 ma) figure 36. average limit measurement from 150 khz to 30 mhz (i led = 0 ma)
measurement um0670 31/43 doc id 15327 rev 2 figure 37. quasi-peak limit measurement from 9 khz to 150 khz (i led = 0 ma) figure 38. quasi-peak limit measurement from 150 khz to 30 mhz (i led = 0 ma)
um0670 design features doc id 15327 rev 2 32/43 10 design features 10.1 proper startup circuit design high pf boost converter design is described in the evl6562a-tm-80w ( section 11: references and related materials : 1. ) and this type of design typically includes a single electrolytic capacitor on the v cc pin of the l6562a to ensure proper startup. the situation for the STEVAL-ILL013V1 is different, as this input capacitor also supplies the second l6562a driver, used for controlling the modified buck converter, and also provides a supply voltage for the pwm generator. generally, this means that there is always some additional current discharging the input capacitor during startup, and therefore the high pf boost converter does not start properly if the low input ac voltage is applied to the board. this is due to there being insufficient energy in the input capacitor to guarantee proper startup. the waweforms which illustrate this situation are given in figure 41 (circuit without capacitor c110 and diode d104). as soon as the input voltage reaches the turn on threshold, the l6562a starts operating and the input voltage on the v cc pin is decreased. as soon as it reaches the turn off threshold, the capacitor is charged again and the l6562a stops operating. this behavior is repeated and so after a short period the output voltage should reach 400 v. however, this is not possible due to low energy in the input capacitor on the v cc pin. this problem is solved by adding capacitor c110 and diode d104 to the original schematic, as shown in figure 39 . thanks to this configuration the input capacitor c107 on the v cc pin is not discharged because it is supplying the pwm generator and second converter. capacitor c110 is used to provide supply voltage to the pwm generator and the second converter. capacitor c110 is charged via a capacitive supply source connected to the zcd when the l6562a operates. the voltage on capacitor c110 is added to the voltage on capacitor c107 through diode d104, and as soon as the voltage on capacitor c110 also reaches the turn on threshold, the l6562a starts operating continuously and the output voltage reaches 400 v, as shown in figure 40 . figure 39. proper startup circuit design c107 mult v cc comp cs inv c110 d104 gnd l6562a zcd gd am00412
design features um0670 33/43 doc id 15327 rev 2 figure 40. proper startup using diode d104 and capacitor c110 figure 41. improper startup without using diode d104 and capacitor c110 10.2 zero dimming design implementation during zero dimming (duty cycle is 0%) the high pf boost converter is in burst mode because there is zero load. during this mode, capacitors c107 and c110 are charged only in short pulses (c107 is also slightly charged via resistor from the input voltage, but it is not enough) and therefore do not have enough energy to also supply the pwm generator and the second l6562a controller used for the modified buck converter. the circuit shown in figure 42 allows brightness changes down to 0% without any problem, because if the
um0670 design features doc id 15327 rev 2 34/43 voltage on the emitter of q102 is below the limit established by voltage divider r125 and r128 (upper limit set to 16.6 v) the transistor is opened and charges c110 and c107. therefore, it is possible to change the brightness between 0% and 100% on the steval- ill013v1. the real measurement is shown in figure 43 , and it is evident that the supply voltage on capacitor c110 is not below 12.5 v during no brightness. figure 42. design improvement allowing zero dimming v out = 400 v vc = 16 v supplying pwm generator with st7liteu05 supplying l6562a in modified buck converter gnd l6562a cs allowing 0% dimming d104 c110 comp inv c107 am00401 r125 r126 r128 q102 zcd v cc mult gd
design features um0670 35/43 doc id 15327 rev 2 figure 43. voltage on capacitor c110 and output bus voltage of 400 v
um0670 references and related materials doc id 15327 rev 2 36/43 11 references and related materials 1. stmicroelectronics, evl6562a-tm-80w, 80 w high performance transition mode pfc evaluation board, data brief; see www.st.com 2. stmicroelectronics, an2928, modified buck converter for led applications, application note; see www.st.com 3. stmicroelectronics, stf9nm50n, n-channel second generation mdmesh? power mosfet, datasheet; see www.st.com 4. stmicroelectronics, stpsc806d, 600 v power schottky silic on carbide diode, datasheet; see www.st.com 5. epcos, b66317, ferrites and accessories e25/13/7 (ef25) core and accessories, datasheet; see www.epcos.com 6. osram, le uw e3b, ostar lighting with optics, datasheet; see www.osram-os.com.
design calculation um0670 37/43 doc id 15327 rev 2 appendix a design calculation the aim of this section is to demonstrate how the components for the modified buck converter are calculated. design calculation follows precisely the equations used in application note an2928 ( section 11: references and related materials : 2. ). therefore, please refer to this application note for more information. a.1 design specifications for a modified buck convertor v in = 400 v v led = 80 v i avr = 1 a i max = 1.4 a i min = 0.6 a f = 50 khz t a = 30 c t jmax_mosfet = 70 c modified buck converter working with duty cycle (output led current is 1 a): equation 1 calculated off time for selected switching frequency of 50 khz is: equation 2 now, the fot network should be calculated. first, resistor r203 is selected: r 203 = 3900 two capacitors in parallel (c204 and c206) are used for the 1 a output led current (jumper jp3 is connected) and their size is determined using the following equation: equation 3 therefore the capacitors c204 and c206 have the following size: c 204 = 390 pf c 206 = 1.5 nf d v led v in ------------- - 80 400 --------- - 0.2 === t off 1d ? () f ----------------- - 10.2 ? () 50000 --------------------- - 16 s == = c 204 c 206 || t off 2.1 r 203 --------------------------- 16 10 6 ? 2.1 3900 ---------------------------- 1.95nf == =
um0670 design calculation doc id 15327 rev 2 38/43 resistor r202 limits the charging current and should be in the following range: equation 4 equation 5 equation 6 a 1 k resistor is chosen for r202 . capacitor c203 should be lower than 1.25 nf, and therefore a value of 220 pf was chosen: equation 7 c 203 = 220 pf inductor size is calculated using following equation: equation 8 two sense resistors are connected in parallel and their size is calculated: equation 9 the output led current of 1 a was precisely set by adjusting resistors r204 and r206, and therefore their optimal resistance values are 1.5 and 2.2 . r 204 = 1.5 r 206 = 2.2 in the next step the power mosfet and its heat sink are calculated. the power mosfet rms current is derived using the following equation: v gd max v zcd clamp v f ? ? i zcd max v zcd clamp r 203 ---------------------------------- - + ------------------------------------------------------------------------------- r 202 r 203 v gd min v ? zcd clamp v f ? v zcd clamp ----------------------------------------------------------------------------- - ?? ?? ?? << 15 5.7 ? 0.7 ? 0.01 5.7 3900 ------------ - ?? ?? + ------------------------------------ - r 202 3900 9.8 5.7 ? 0.7 ? 5.7 ------------------------------------ - ?? ?? << 750 r 202 2326 << c 203 c 204 c 206 || () v zcd clamp v gd cmax v zcd clamp ? v f ? () --------------------------------------------------------------------------------------- - 1.89 10 9 ? 5.7 15 5.7 ? 0.7 ? ---------------------------------- - 1.25nf == < l v led t off 2i max i avr ? () --------------------------------------------- - 80 16 10 6 ? 21.41 ? () --------------------------------------- 1.6mh === r 204 r 206 v cs i max ------------ 1.08 1.04 ----------- 0.77 === ||
design calculation um0670 39/43 doc id 15327 rev 2 equation 10 power mosfet conduction loss is: equation 11 where the power mosfet chosen is the stf9nm50n (see datasheet section 11: references and related materials : 3. ) and its r ds (on) for 70 c is: equation 12 power mosfet switching losses can be approximately calculated (turn off time was measured 120 ns - see figure 19 ): equation 13 the total power loss on the power mosfet is 1.839 w, so the heat sink can be calculated from following equation: equation 14 and maximum heat sink-to-ambient resistance is: equation 15 the heat sink used in the power mosfet on the STEVAL-ILL013V1 has a thermal resistance of 13.5 c / w, and therefore this heat sink is optimized for this design. the last power component remaining to be calculated is the power diode. the diode conducts during the off time, and therefore its average current is: equation 16 l rms 2 d l avr 2 l pp 2 12 ------- - + 0.2 1 0.8 2 12 ---------- - + 0.21 = == p con l rms 2 r ds on () 70 c () 0.21 0.756 0.159w = == r ds on () c () r ds on () c () 1.35 0.56 1.35 0.756 = = = p sw v in i max t off sw f 2 ------------------------------------------------------------------- - 400 1.4 120 10 9 ? 50 10 3 2 -------------------------------------------------------------------------------------------- - 1.68w = = = p tot t jmax mosfet t a ? r thjc r thch r thha ++ ----------------------------------------------------------- - = r thha t jmax mosfet t a ? p tot ------------------------------------------------------ r thjc ? r thch 70 30 ? 1.839 ------------------ - 5 ? 0.5 16.25 cw ? = ? = ? < i avr d 1d ? () i max i min + 2 ----------------------------- - 10.2 ? () 1.4 0.6 + 2 ---------------------- - 0.8a = = =
um0670 design calculation doc id 15327 rev 2 40/43 power loss on the stpsc806d diode is: equation 17 where forward diode voltage was found for the average diode current 0.8 a in the datasheet (see datasheet section 11: references and related materials : 4. ). calculated junction diode temperature without using heat sink is: equation 18 junction-to-case thermal resistance is available in the datasheet for the stpsc806d and case-to-ambient temperature is determined by the device package used. in this case, the to-220 package is used and its thermal resistance is typically 60 c / w. calculated junction diode temperature without using a heat sink is much lower than the maximum junction temperature for the stpsc806d, and therefore this diode is suitable for the design. one of the most important things to consider is proper inductor design. the inductor size was calculated in equation 8 , but generally the inductor size by itself is not enough to ensure proper inductor design and therefore several additional equations are used for completing overall inductor construction. first, the inductor core size must be selected and for this selection it is very helpful to calculate the minimum area product using application parameters. minimum required core area product (ap), where the flux swing is limited by core saturation is: equation 19 where the constant is cl = j max x c r x 10 ?4 = 420 x 0.5 x 10 ?4 . the inductor core e25 from epcos was selected. the minimum core cross section is 51.5 mm 2 and the winding cross section is 61 mm 2 (see datasheet section 11: references and related materials : 5. ) and the calculated product area is: equation 20 the calculated product area is bigger than the minimum required product area, and therefore the inductor core e25 can be used. p loss d i avr d v f 0.8 0.7 0.56w = = = t j p loss d r thjc r thca + () t a 0.56 2.4 60 + () 30 65 c = + = + = ap min ll peak l rms b max cl --------------------------------------------- ?? ?? 4 3 -- - 1.6 10 3 ? 1.4 1 0.3 420 0.5 10 4 ? ----------------------------------------------------------- - ?? ?? ?? 4 3 -- - 0.2518cm 4 = = = ap a n a min 61 51.5 0 31415cm 4 , = = =
design calculation um0670 41/43 doc id 15327 rev 2 the number of turns for the inductor is: equation 21 where the inductance factor al for the e25 core and 2 mm gap is calculated: equation 22 k 1 = 70 (see datasheet section 11: references and related materials : 5. ) k 2 = ? 0,73 (see datasheet section 11: references and related materials : 5. ) s = e25 core air gap [mm]. the last step to complete the inductor design is to calculate the wire diameter. maximum inductor power dissipation is: equation 23 the wire resistance on the inductor is (copper wire with diameter of 0.28 mm is chosen): equation 24 where average turn length i n is written in the core datasheet (see datasheet section 11: references and related materials 5. ). the power dissipation on the wire is: equation 25 the power loss in the wire is much lower than the maximum power loss in the inductor, and so a wire with a diameter of 0.28 mm is suitable for this inductor. n l a l ------ 1.6 10 3 ? 54.22 10 9 ? --------------------------------- - 172 = = = a l k 1 s 1 k 2 ------ 90 2 1 0.73 ? -------------- 54.22nh = = = p max loss t max t a ? r t --------------------------- 70 30 ? 40 ------------------ - 1w = = = r ? l s -- - l n n d --------------- - 1.76 10 6 ? 5172 3.14 0.028 --------------------------------- - 17.2m = = = = p wire rl avr 2 17.2 10 3 ? 1 2 17.2mw = = =
um0670 revision history doc id 15327 rev 2 42/43 12 revision history table 4. document revision history date revision changes 15-may-2009 1 initial release. 10-aug-2009 2 document reformatted, corrected typing error in figure 7 , added note below ta b l e 3 .
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