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1 www.irf.com irpllnr5 irpllnr5 wide range input linear fluorescent ballast reference design using the irs2168d table of contents page 1. features?????????????????????????...?.2 2. descrip tion.............................................................................................2 3. electrical c haracterist ics .......................................................................3 4. fault protection characteri stics.............................................................4 5. irpllnr5 schematics????...??..?????????????..5 6. pcb component placem ent diagram and board fabrication????..6 7. bill of material and induc tor specification?????????..???..8 8. functional description???.?????????.???????....11
2 rd-0613 www.irf.com 1. features ? drives 1 x 54 w tl5 lamp ? input voltage: 90-305 vac ? high power factor/low total harmonic distortion ? high frequency operation ? lamp filament preheating ? lamp fault protection with auto-restart after lamp replacement ? low ac line protection ? lamp end-of-life shutdown ? irs2168d hvic ballast controller 2. description the irpllnr5 reference design is a high efficien cy, high power factor, fixed output, electronic ballast designed for driving rapid-start fluorescen t lamp types. the design contains an emi filter, active power factor correction, and a ballast control circuit using the irs2168d(s)pbf ballast control ic. this reference design is intended to ease the evaluation of the irs2168d, demonstrate pcb layout techniques, and serve as an aid in the development of a production-ready ballast using the irs2168d. irs2168d line input uvlo pfc control half-bridge driver lamp fault lamp emi filter rectifier boost pfc output stage control ic fig. 1: ballast block diagram
3 rd-0613 www.irf.com 3. electrical characteristics parameter units value lamp type 54 w tl5 input power [w] 54 lamp running voltage [vpp] 400 run mode frequency [khz] 50 preheat mode frequency [khz] 85 preheat time [s] 1.0 lamp preheat voltage [vpp] 500 lamp ignition voltage [kvpp] 2.0 input ac voltage range [vac] 90-305 vac power factor 0.995 at 120 vac 0.98 at 220 vac total harmonic distortion [%] 10 at 120 vac 14 at 220 vac table 3.1: ballast parameters vin pin (w) pf thd (%) dcbus (v) 90 55.5 0.997 9.15 495 110 52.8 0.996 9.85 495 130 51.8 0.994 11 495 150 51.1 0.992 11.25 495 170 50.8 0.99 12.2 495 190 50.7 0.987 12.8 495 210 50.6 0.983 13.9 495 230 50.5 0.978 14.9 495 250 50.5 0.972 16.1 495 270 50.5 0.964 17.7 495 table 3.2: pfc data
4 rd-0613 www.irf.com 0.96 0.965 0.97 0.975 0.98 0.985 0.99 0.995 1 90 140 190 240 vin pf 0 2 4 6 8 10 12 14 16 18 20 thd pf pm thd pm fig. 2: pfc and thd performa nces versus input voltage 4. fault protection characteristics fault ballast restart operation line voltage low deactivates increase line voltage upper filament broken deactivates lamp exchange lower filament broken d eactivates lamp exchange failure to ignite deactivates lamp exchange open circuit (no lamp) d eactivates lamp exchange end of life deactivates lamp exchange
5 rd-0613 www.irf.com 5. irpllnr5 schematics fig. 3: schematic diagram, irs2168d, single lamp, voltage mode heating
6 rd-0613 www.irf.com 6. pcb component place ment diagram and board fabrication fig. 4: pcb compon ent placement diagram
7 rd-0613 www.irf.com board fabrication 1) board size: l = 8.59 inch, w = 1.195 inch 2) no. of copper layers: 1 (bottom layer) 3) copper: 2 oz. 4) board material: fr-4 5) through hole plating: no 6) solder plating on pads: yes 7) solder mask: green lp1 (bottom layer only) 8) silk screen layers: top and bottom 9) silk screen ink: white epoxy, non-conductive 10) gerber file: irpllnr5.zip 11) gerber file description: a) irpllnr5.apr apertures b) irpllnr5.drl nc drill c) irpllnr5.drr nc drill d) irpllnr5.gbl bottom layer e) irpllnr5.gbo silk screen bottom f) irpllnr5.gbs solder mask bottom g) irpllnr5.gd1 drill drawing h) irpllnr5.gg1 drill guide i) irpllnr5.gm1 mechanical layer j) irpllnr5.gto silk-screen top
8 rd-0613 www.irf.com 7. bill of material and inductor specification item qty manufacturer part numb er description reference 1 1 diodes inc. df10s bridge rectifier, 1 a, 1000 v br1 2 1 roederstein wkp222mcpej0k capacitor, 2.2 nf, 305 vac y cap cy 3 1 dale cw-1/2 resistor, 0.5 ? , 1/2 w f1 4 1 roederstein f1772433-2200 capacitor, 0.33 f, 275 vac c1 5 1 panasonic elf-15n007a emi inductor, 10 mh, 0.7 a peak l1 6 1 vishay dale mkp1841410634 capacitor, 0.1 f, 630 vdc c2 7 1 wima mkp10-.1/400/10 capacitor, 0.1 f, 400 vdc cdc 8 1 panasonic erz-v05d471 transient suppressor rv1 9 1 vogt il 060 320 41 02 pfc inductor, 2 mh, 2.5 a peak lpfc 10 2 panasonic eeu-eb2v330s capacitor, 33 f, 350 vdc, 105 c cbus1, cbus2 11 2 panasonic ecj-3vb1e104k capacitor, 0.1 f, smt 1206 cbs, cvcc 12 2 panasonic ecu-v1h102jch capacitor, 1 nf, smt 1206 csd, ceol (see note 2) 13 3 panasonic ecj-3yb1e105k capacitor, 1 f, smt 1206 ccomp, cph, cvco 14 1 panasonic ecu-v1h103kbm capacitor, 0.01 f, smt 1206 cvbus 15 1 panasonic ecj-3vb1e334k capacitor, 0.33 f, smt 1206 csd1 16 1 panasonic ece-a1ekg100 capacitor, 10 f, 25 vdc, 105 c cvcc1 17 1 johanson dielectrics 102r29w102kv4e capacitor, 1 nf, 1 kv, smt 1808 cbs 18 1 wima fkp1-3300/2000/5 capacitor, 3.3 nf, 2 kv cres 19 2 panasonic ecu-v1h471kbm capacitor, 470 pf, smt 1206 ccs, coc 20 2 panasonic ecqb1104jfw capacitor, 0.1 f, 100 v ch1, ch2 21 1 diodes inc. zmm5240b-7 zener diode, 10 v, minimelf, 0.5 w deol1 22 1 diodes inc. zmm5232b-7 zener diode, 5.6 v, minimelf, 0.5 w deol2 23 1 digi-key murs160dict-nd diode, 1 a, 600 v, smt smb dpfc 24 3 diodes ll4148dict-nd diode, 1n4148, smt dl35 dcp1, dcp2, dsd 25 1 tyco electronics/amp 2-641262-1 dip 16 ic socket through-hole ic1 26 1 international rectifier irs2168d ic, ballast driver / pfc ic1 27 1 vogt il 060 320 51 01 resonant inductor, 2 mh, 2 a peak lres 28 3 international rectifier irfb9n60a transistor, mosfet mpfc, mhs, mls 29 2 > = 22 a.w.g jumpers j1, j2 30 5 panasonic erj-8geyj120v resistor, 12 ? , smt 1206 rpfc, rlo, rho, rlm1, rlm2 31 1 panasonic erj-8geyj474v resistor, 470 k ? , smt1206 rcph 32 1 phoenix passive components 5033ed220k0f12af5 resistor, 220 k ? , 1/2 w rvcc 33 2 panasonic erj-8geyj684v resistor, 680 k ? , smt 1206 rvbus1, rvbus2 34 1 panasonic erj-8geyj333v resistor, 33 k ? , smt 1206 rzx 35 2 panasonic erj-8geyj102v resistor, 1 k ? , smt 1206 rf1, rf2 36 1 vishay/dale rs01a1r500fs70 resistor, 1.5 ? , 1%, 1 w rcs 37 1 digi-key p0.62w-1bk-nd resistor, 0.62 ? , 1 w roc 38 1 panasonic erj-8enf1132v resistor, 11.3 k ? , 1%, smt 1206 rvbus 39 1 panasonic erj-8geyj104v resistor, 100 k ? , smt 1206 rsd 40 4 panasonic erj-8geyj224v resistor, 220 k ? , smt 1206 reol1, reol2, reol3, rpu 41 1 panasonic erj-8geyj203v resistor, 20 k ? , 5%, smt 1206 reol4 (see note 3) 42 1 digi-key 36.0kfrct-nd resistor, 36 k ? , 1%, smt 1206 rfmin 43 1 panasonic erj-8geyj563v resistor, 56 k ? , 1%, smt 1206 rph 44 1 wago 235-203 connector, 3 terminal x1 45 1 wago 235-207 connector, 4 terminal x2 table 1: bill of material lamp type: 54 w tl5; line input voltage: 80-305 vac
9 rd-0613 www.irf.com note 1: different lamp types require different frequency programming components. note 2: ceol and csd values can be increased up to 470 nf to increase noise immunity. note 3: reol4 value can be increased to 33 k ? for a more sensitive lamp end-of-life detection horizontal inductor specification core size core material gap length fi 324 or equivalent winding start pin finish pin turns wire diameter (mm) main zx physical layout test main winding inductance inductance tolerances: +/- 5% mm part no.: il 060 320 41 02 ref des: lpfc (test frequency = 50khz) nominal inductance maximum current maximum core temperature mh apk oc 115 note : inductor must not saturate at maxi mum current and maximum core temperature at given test frequency electrical layout bobbin pins evd25 3.5 8 2 2.5 17 tbd 3526 4 strands of awg 32 awg 32 5mm 5mm 20.05mm 25mm top view 1 2 3 4 8 7 6 5 main winding inductance induct ance resistance max 3.2 ohm fig. 5: power factor inductor specification
10 rd-0613 www.irf.com horizontal inductor specification core size core material gap length fi 324 or equivalent winding start pin finish pin t urns wire diameter (mm) main physical layout t est main winding min 1.9 max 2.1 main winding mm mh mh max 1.8 ohms part no.: il 060 320 51 01 ref des: lres (test frequency = 50khz) nominal inductance maximum current maximum core temperature mh a pk oc 115 note : inductor must not saturate at maximum current and maximum core temperature at given test frequency. electrical bobbin pins cathode (1) cathode (2) evd25 2.82 8 2 2 5mm 5mm 20.05mm 25mm top view 1 2 3 4 8 7 6 5 1 8 185 4 strands of awg 32 6 7 8 4 strands of awg 32 4 5 8 4 strands of awg 32 fig. 6: resonant i nductor specification
11 rd-0613 www.irf.com 8. functional description the irpllnr5 reference design consists of an emi f ilter, an active power factor correction section, a ballast control section, and a resonant lamp output stage. the active power factor correction section is a boost converter operating in critical conduction, free-running frequency mode. the ballast control section provides frequency modulation control of a tr aditional rcl lamp resonant output circuit and is easily adaptable to a wide variety of lamp types. th e ballast control section also provides the necessary circuitry to perform lamp fault det ection, shutdown, and auto-restart. reference design overview this demo-board is designed for a single 54 w tl5 lamp with voltage mode heating. tl5 lamps are popular due to their low profile and high lumen/watt output. these lamps, however, can be more difficult to control due to their higher ignition and running voltages. a typical ballast output stage using current-mode filament heating (filament placed inside l-c tank) will result in excessive filament current during running. the output stage has therefore been configured for voltage-mode filament heating using secondary windings off of the re sonant inductor lres. the lamp has been placed outside the under- damped resonant circuit loop, which consist of lres and cres. the filament heating during preheat can be adjusted with the capacitors ch1 and ch2. the result is a more flexible ballast output stage necessary for fulfilling the lamp requirements. the dc blocking capacitor, cdc, is also placed outside the under-damped resonant circuit loop such that it does not influence the natural resonance frequency of lres and cres. the snubber capacitor, csnub, serves as emi reduction and a charge pump for supplying the irs2168d. the irs2168d ballast control ic is used to program the ballast operating points and protect the ballast against conditions such as lamp strike failures, low dc bus or lamp failure during normal operations. it is also used to regulate the dc bus and for power factor correction to give high power factor and low harmonic distortion of the ballast ac input current. power factor correction section the power factor correction section contained in the irs2168d controls a boost topology circuit operating in critical conduction mode. this topology is designed to step-up and regulate the output dc bus voltage while drawing sinusoidal current from the line (low thd) which is ?in phase? with the ac input line voltage. the power factor correction section also includes over-current protection of the boost mosfet to prevent damage that can occur during boost inductor saturation. ballast control section the ballast control section of the irs2168d ballast control ic contains an oscillator, a high-voltage half-bridge gate driver, and lamp fault protection circuitry. please refer to the datasheet of this ic for the block diagram and the state diagram. the following is a breakdown of the different modes of operation for the ballast. startup mode when power is initially applied to the ballast, the voltage on the vcc pin of the irs2168d begins to increase. the voltage for the irs2168d is derived fr om the current supplied from the rectified ac line through the startup resistor rsupply. during th is initial startup when the vcc voltage of the irs2168d is below the rising under-voltage lock-out threshold (uvlo+), the ic is in uvlo mode and draws micro-power current at vcc. the micro-power current of the irs2168d allows for the use of a
12 rd-0613 www.irf.com large value, low-wattage startup resistor (rsupply). when the voltage on the irs2168d reaches the rising under-voltage lockout threshold (12.5 v), the gate driver oscillator is enabled (this assumes that there are no fault conditions) and drives the half-b ridge output mosfets (mhs and mls). when the half-bridge is oscillating, capacitor csnub, diod es dcp1 and dcp2 form a snubber/charge pump circuit which limits the rise and fall time at the half-b ridge output and also supplies the current to charge capacitor cvcc2 to the vcc clamp voltage (approx. 15.6 v). when the rising under-voltage lockout threshold of the irs2168d is reached, the power factor control output also starts to oscillate and drives mosfet mpfc to boost and regulate the bus voltage to 500 v dc. preheat mode when the ballast reaches the end of the uvlo mode, the preheat mode is entered. at this point, the ballast control oscillator of the irs2168d has begun to operate and the half-bridge output is driving the resonant load (lamp) circuit. there is an initial startup frequency that is higher than the preheat frequency that lasts for only a short duration. this is done to ensure that the initial voltage appearing across the lamp at the startup of oscillation does not exceed the minimum lamp ignition voltage. if, at the initiation of oscillation of the half-bridge, the voltage across the lamp is large enou gh, a visible undesired flash of the lamp can occur. this in effect is a cold strike of the lamp and can shorten the life of the lamp. the ballast control section oscillator of the irs2168d consists of an internal timing capacitor and an external timing resistor (rfmin ). resistors rfmin and rph progra m a current that determines the ramp up time of the internal timing capacitor. the preheat frequency is determined by the equivalent resistance formed by the parallel combination of rfmin and rph. th e preheat frequency is selected such that the voltage appearing across the lamp is below the minimum lamp ignition voltage while supplying enough current to preheat the lamp filaments to their correct emission temperature within the preheat mode time period. the preheating of the lamp filaments is performed using voltage mode heating that consists of a constant voltage across the lamp filaments. the waveform in figure 7 shows the cph voltage and lamp voltage during normal preheat, ignition, and run modes. figure 8 shows the half-bridge voltage (vs pin) during preheat mode.
13 rd-0613 www.irf.com fig. 7: cph pin voltage (black) and lamp voltage (blue) during normal preheat, ignition and run modes fig. 8: half-bridge mid-point volt age (vs pin) during preheat mode
14 rd-0613 www.irf.com f osc t preheat ignition run f preheat f run start f fig. 9: oscillator frequency versus time during normal operating conditions figure 9 shows a plot of the half-bridge oscillati on frequency as a function of time for normal preheat, ignition and run ballast operating modes. the dura tion of the preheat mode, as well as all ballast operating modes, are determined by the voltage on the cph pin of the irs2168d. at the end of uvlo mode, preheat mode is entered and the external cap acitor at the cph pin of the irs2168d begins to charge through the external resistor (rcph) from cph to vcc. the ballast remains in preheat mode until the voltage on the cph pin exceeds the end-of-preheat mode threshold of 0.67(v cc ), at which time the ballast then enters ignition mode. ignition mode when the ic enters ignition mode, cph is discharged quickly to 0.33(v cc ) and rph is disconnected from com via an internal mosfet at the rph pin. cph begins to charge up again from 0.33(v cc ) and the frequency begins to ramp down to the run frequency at a rate determined by the time constant rph(cvco). during this ramping downward of the fr equency, the voltage across the lamp increases in magnitude as the frequency approaches the resonant frequency of the lc load circuit until the lamp ignition voltage is exceeded and the lamp ignites. the maximum ignition voltage that can be generated is determined from the value of rcs, and the ignition frequency must be higher than the run frequency so that the frequency sweeps through the resonance frequency to ensure lamp ignition. if the lamp does not ignite, then the ignition regulation feature of th e irs2168d will regulate the ballast output voltage to a constant level (programmed by rcs) for the duration of ignition mode. figure 10 shows the lamp voltage during ignition ramp and ignition regulation during a lamp non-strike condition.
15 rd-0613 www.irf.com fig. 10: cph pin voltage (black) an d lamp voltage (blue) during lamp non-strike fault condition during ignition mode, the voltage on the cph pin of the irs2168d continues to ramp up until the voltage at the cph pin exceeds 0.67(v cc ) a second time and the ic enters run mode. the over-current fault counter is disabled during ignition mode due to the ignition regulation feature and enabled again at the start of run mode. during a lamp non-strike condition, the ignition voltage will be regulated for the duration of ignition mode and then unregulated during run mode. this means that the ignition voltage will increase slightly after ignition mode (as the frequency decreases towards the run frequency) until the fault counter times out, after 65 cycles above the over-current threshold, and the ballast shuts off. the amount of frequency shift and resulting voltage increase is determined by the value of cvco. the 5 v shutdown threshold at the sd pin is also disabled during ignition mode and enabled again at the start of run mode. a full explanation of the functionality of the over-current sensing and shutdown functions are in the fault mode section. run mode during run mode and after a successf ul lamp ignition, the frequency is at the final run frequency and is determined by rfmin. the 1 v and 3 v end-of-life (eol) window comparator at the sd/eol pin, the 5 v unlatched shutdown threshold at the sd/eol pin, and the fault counter at the cs pin, are all enabled in run mode. a functional description of the over-current sensing and end-of-life sensing is given in the fault mode section.
16 rd-0613 www.irf.com the run mode frequency (figure 11) is that at which the lamp is driven to the lamp manufacturer?s recommended lamp power rating. the running frequency of the lamp resonant output stage for selected component values is defined as, f lc p cv lc p cv v v lc run lamp lamp lamp lamp dcbus lamp =? ? ? ? ? ? ? +? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? 1 2 1 2 1 24 1 2 2 2 2 2 2 2 22 where, l = lamp resonant circuit inductor (lres) (h) c = lamp resonant circuit capacitor (cres) (f) p lamp = lamp running power (w) v lamp = lamp running voltage amplitude (v) fig. 11: half-bridge mid-point voltage (vs pin) during run mode normal power down a normal power down occurs when the ac line voltage is disconnected from the ballast. when this occurs, the voltage on the vbus pin of the irs2168d drops below the vbus pin under-voltage reset threshold of 3 v. this will cause vcc to be discha rged internally to uvlo- (10.5 v). the ic enters
17 rd-0613 www.irf.com uvlo mode and the pfc and ballast oscillators are disabled, the pfc and half-bridge driver outputs (pfc, lo, and ho) are turned o ff, and the irs2168d consumes micro-power current at vcc. lamp removal and auto-restart resistors rpu, rsd and capacitor csd1 form a divi der/filter network used to detect an open lower lamp filament and/or lamp replacement. under norm al conditions, the voltage across csd1 is close to zero. if the lower filament becomes open or the lamp is removed, however, the voltage at the sd pin increases above the 5 v threshold and causes the ic to shutdown (figure 12). the ballast remains shutdown until a lamp replacement is performed. if th e lamp is replaced with a lamp with a good lower filament, the voltage on the sd pin of the irs2168d drops back below the 3 v threshold and the ballast will restart in preheat mode. the ballast w ill go through the preheat, ignition, and run mode sequences each time a restart is performed. note th at the sd pin of the ir s2168d is active during preheat and run modes and is disabled during ignition mode. fig. 12: sd pin voltage (black) and lamp voltage (blue) during lamp removal/auto-restart condition fault mode when a fault is detected at the cs pin or sd/e ol pin, the ic will enter fault mode. during fault mode, the ballast section and pfc section are both shutdown. the dc bus voltage will drop to the non-boosted peak ac line voltage level. there are se veral lamp fault conditions that can cause the ic to enter into fault mode. these include: hard-switching at the half-bridge mid-point (open load), over- current (non-strike), lamp voltage shift (end-of-life), and lamp remova l (sd/eol pin). resistor rcs in the source lead of the low-side mosfet (mls) serves as the current-sensing point for the half-bridge, and is used to detect hard-switching or over-current. during normal operation when the half-bridge is oscillating, a voltage appears across rcs when th e low-side mosfet, mls, is turned on. the magnitude of this voltage directly relates to the current in the lamp resonant circuit.
18 rd-0613 www.irf.com if at any time during preheat mode or run mode the voltage across resistor rcs rises above the over- current threshold (1.25 v) for 65 events, the pfc and half-bridge mosfets, (mpfc, mhs and mls) are turned off and the ballast goes into fault mode. during the ignition mode, the over-current is disabled and the ignition regulation feature limits the maximum current flowing in the resonant tank and half-bridge. an over-current condition can occur if the lamp fails to ignite or the lamp is broken (an open circuit cathode or broken lamp). if a cathode is broken (open circuit), the half-bridge output hard-switches. each time the low-side mosfet (mls ) is turned on, a large current pulse occurs and thus a large voltage pulse occurs across resistor rcs signaling a fault. the ballast will remain in fault mode until the ac line voltage is reset or a lamp replacement is performed. during an end-of-life lamp fault condition, the lamp voltage can increase or decrease asymmetrically. the resulting excessive voltage across the lamp filament s can cause the lamp ends to reach temperatures high enough to melt the tube glass. the lamp can then fall out of the fixture and cause harm or damage. to protect against this condition, resistors reol 1, reol2, reol3, reol4, and zener diodes deol1 and deol2, are used for end-of-life protection. the end-of-life window comparator at the sd/eol pin is enabled in run mode. if the voltage on sd/eol pi n falls outside the range of the internal 1 v ? 3 v window comparator, the ic will enter fault mode. the sd/eol pin is internally biased at 2 v with an internal +/-10 a ota. the value of reol4, deol1 and de ol2 are selected such that the sd/eol pin remains at 2 v during normal operation, but increases above 3 v or decreases below 1 v during an end-of-life fault condition. the lamp voltage end-of-lif e threshold can be adjusted by changing the value of resistor reol4 and/or zener diodes deol1 and deol2. a threshold of 30% higher than the nominal running lamp voltage is typical. pfc control section the irs2168d contains control circuitry for driving a boost-type power factor correction (pfc) circuit. this is necessary for producing sinu soidal input curr ent at the mains input that is ?in phase? with the mains voltage and contains minimal total harmonic distortion (thd). it is also convenient to use the boost converter to regulate the dc bus voltage to a constant dc level. the pfc control is achieved using five control pins. the dc bus voltage is sensed with a resistor divider at the vbus pin. the loop compensation speed is programmed with an external capacitor at the comp pin. the cycle-by-cycle zero-crossing of the boost in ductor current is detected at the zx pin. the gate drive for the boost mosfet is provided by the pfc pin. the cycle-by-cycle over-current protection is performed by the oc pin. the following waveforms show the operation of the pfc at 120 vac (figure 13) and 290 v ac (figure 14) input line conditions.
19 rd-0613 www.irf.com fig. 13: ac input current (green) and ac input voltage (blue) at 120 vac fig. 14: ac input current (green) and ac input voltage (blue) at 290 vac pfc over-current protection the pfc section includes cycle-by-cyc le over-current protection. the oc pin senses the current in the pfc mosfet via an external sense re sistor (roc). should the voltage across this resistor exceed the internal threshold (1.25 v typical), the pfc mosfet will turn off to limit the instantaneous current
20 rd-0613 www.irf.com and will turn on again at the next zero-crossing of the inductor current as detected by the zx pin. this over-current condition can occur, fo r example, during a low-line condition (figure 15). as the ac line decreases, the pfc inductor and mosfet current w ill increase to keep the dc bus constant for a given power level. when the peak current reaches the over-current threshol d, the cycle-by-cycle current limit will cause the peak of the mosfet current to flatten and the dc bus to start to drop. this current limit is necessary to prevent saturation of the pfc inductor current and to protect the pfc mosfet from being damaged. fig. 15: oc pin voltage (black) and dc bu s voltage (green) during low-line condition brown-out protection the irs2168d includes an under-voltage reset (uvr) function at the vbus pin. should the dc bus decrease too far during a momentary interrupt of the mains input voltage, the ballast should be properly shutdown and restarted. this will prevent the lamp from extinguishing and will properly preheat and restart the lamp when the mains voltage returns. if the vbus pin voltage decreases below 3 v, the pfc and half-bridge gate drivers will be turned off and vcc will be discharged to uvlo-. the ballast will then be restarted via the rsupply resistor wh en the mains voltage reach es a high enough level again (figure 16).
21 rd-0613 www.irf.com fig. 16: vbus pin (black), lamp voltage (blue) and dc bus voltage (green) during momentary interruption of the mains 02/15/2007

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