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? 2007 fairchild semiconductor corporation www.fairchildsemi.com FAN7711 ballast control ic march 2007 FAN7711 rev. 1.0.2 FAN7711 ballast control ic features ? floating channel for bootstrap operation to +600v ? low start-up and operating current: 120 a, 3.2ma ? under-voltage lockout with 1.8v of hysteresis ? adjustable run frequency and preheat time ? internal active zvs control ? internal protection function (latch mode) ? internal clamping zener diode ? high accuracy oscillator ? soft-start functionality applications ? electronic ballast description the FAN7711, developed using fairchild?s unique high- voltage process, is a ballast control integrated circuit (ic) for a fluorescent lamp. FAN7711 incorporates a preheating / ignition function , controlled by an user- selected external capacitor, to increase lamp life. the FAN7711 detects switch operation from after ignition mode through an internal active zero-voltage switching (zvs) control circuit. this control scheme enables the FAN7711 to detect an open-lamp condition, without the expense of external circuitry, and prevents stress on mosfets. the high-side driver built into the FAN7711 has a common-mode noise cancellation circuit that provides robust operation against high-dv/dt noise intrusion. ordering information 8-dip 8-sop part number package pb-free operating temperature range packing method FAN7711n 8-dip yes -25c ~ 125c tube FAN7711m 8-sop tube FAN7711mx ta p e & r e e l
FAN7711 ballast control ic ? 2007 fairchild semiconductor corporation www.fairchildsemi.com FAN7711 rev. 1.0.2 2 typical appli cation diagrams figure 1. typical application circuit for compact fluorescent lamp internal block diagram figure 2. functional block diagram v dd rt cph gnd main supply r1 r2 r3 d5 d6 r4 r5 l1 c3 c2 v b ho v s lo q1 q2 c4 c6 c7 c5 d7 d1 d2 d3 d4 c1 FAN7711 6 7 8 5 4 3 2 1 lamp FAN7711 rev. 1.00 u1 3v 5v cph i ph i ph * i rt i ph =0.6*i rt 0a 4v i ph * oscillator cph dead-time control 5v/3v s r q q sdl sdh reset syshalt adaptive zvs enable logic v ddh /v dd lsh v ddh /v dd lsh sdl sdh short-pulse generator noise canceller s r q q uvlo v b set reset delay 15v shunt regulator rt cph v dd v s ho v b i rt low-side gate driver pre-heat control high-side driver uvlo s rq q tsd bias bgr syshalt uvlo sdh sdl 10v reg reference v dd sense cph<3v yes no 2 a 12 a output transition sensing adaptive zvs controller bias & system latch gnd lo FAN7711 rev. 1.00 8 7 6 5 4 3 2 1
FAN7711 ballast control ic ? 2007 fairchild semiconductor corporation www.fairchildsemi.com FAN7711 rev. 1.0.2 3 pin configuration figure 3. pin configuration (top view) pin definitions pin # name description 1v dd supply voltage 2 rt oscillator fre quency set resistor 3 cph preheating time set capacitor 4 gnd ground 5 lo low-side output 6v s high-side floating supply return 7 ho high-side output 8v b high-side floating supply FAN7711 yww 1 2 3 4 8 7 6 5 v dd rt cph gnd v b ho v s lo FAN7711 rev. 1.00 (yww : work week code)
FAN7711 ballast control ic ? 2007 fairchild semiconductor corporation www.fairchildsemi.com FAN7711 rev. 1.0.2 4 absolute maximum ratings stresses exceeding the absolute maximum ratings may damage the device. the device may not function or be opera- ble above the recommended operating conditions and stressing the parts to these levels is not recommended. in addi- tion, extended exposure to stresses above the recommended operating conditions may affect device reliability. the absolute maximum ratings are stress ratings only. t a =25c unless otherwise specified. note: 1. do not supply a low-impedance volt age source to the internal clamping zener diode between the gnd and the v dd pin of this device. symbol parameter min. typ. max. unit v b high-side floating supply -0.3 625 v v s high-side floating supply return -0.3 600 v v in rt, cph pins input voltage -0.3 8 v i cl clamping current level 25 ma dv s /dt allowable offset voltage slew rate 50 v/s t a operating temperature range -25 125 c t stg storage temperature range -65 150 c p d power dissipation 8-sop 0.625 w 8-dip 1.2 ja thermal resistance (junction-to-air) 8-sop 200 c/w 8-dip 100
FAN7711 ballast control ic ? 2007 fairchild semiconductor corporation www.fairchildsemi.com FAN7711 rev. 1.0.2 5 electrical characteristics v bias (v dd , v bs ) = 15.0v, t a = 25 c, unless otherwise specified. symbol characteristics condition min. typ. max. unit supply voltage section v ddth(st+) v dd uvlo positive going threshold v dd increasing 12.4 13.4 14.4 v v ddth(st-) v dd uvlo negative going threshold v dd decreasing 10.8 11.6 12.4 v ddhy(st) v dd -side uvlo hysteresis 1.8 v cl supply clamping voltage i dd =10ma 14.8 15.2 i st start-up supply current v dd = 10v 120 200 a i dd dynamic operating supply current 50khz, c l = 1nf 3.2 ma high-side supply section (v b -v s ) v hsth(st+) high-side uvlo positive going threshold v bs increasing 8.5 9.2 10.0 v v hsth(st-) high-side uvlo negative going threshold v bs decreasing 7.9 8.6 9.5 v hshy(st) high-side uvlo hysteresis 0.6 i hst high-side quiescent supply current v bs = 14v 50 a i hd high-side dynamic operating supply current 50khz, c l = 1nf 1 ma i lk offset supply leakage current v b = v s = 600v 45 a oscillator section v mph cph pin preheating voltage range 2.5 3.0 3.5 v i ph cph pin charging current during preheating v cph = 1v 1.25 2.00 2.85 a i ig cph pin charging current during ignition v cph = 4v 8 12 16 v mo cph pin voltage level at running mode 7.0 v f pre preheating frequency rt = 80k , v cph = 2v 72 85 98 khz f osc running frequency rt = 80k 48.7 53.0 57.3 khz dt max maximum dead time v cph = 1v, v s = gnd during preheat mode 3.1 s dt min minimum dead time v cph = 6v, v s = gnd during run mode 1.0 s output section i oh+ high-side driver sourcing current pw = 10 s 250 350 ma i oh- high-side driver sinking current pw = 10 s 500 650 i ol+ low-side driver sourcing current pw = 10 s 250 350 i ol- low-side driver sink current pw = 10 s 500 650 t hor high-side driver turn-on rising time c l = 1nf, v bs = 15v 45 ns t hol high-side driver turn-off rising time c l = 1nf, v bs = 15v 25 t lor low-side driver turn-on rising time c l = 1nf, v bs = 15v 45 t lol low-side driver turn-off rising time c l = 1nf, v bs = 15v 25 v s (2) maximum allowable negative v s swing range for signal propagation to high-side output -9.8 v
FAN7711 ballast control ic ? 2007 fairchild semiconductor corporation www.fairchildsemi.com FAN7711 rev. 1.0.2 6 electrical characteristics (continued) v bias (v dd , v bs ) = 15.0v, t a = 25 c, unless otherwise specified. note: 2. this parameter, although guarantee d, is not 100% tested in production. symbol characteristics condition min. typ. max. unit protection section v cphsd shutdown voltage v rt = 0 after run mode 2.6 v i sd shutdown current 250 a tsd thermal shutdown (2) 165 c
FAN7711 ballast control ic ? 2007 fairchild semiconductor corporation www.fairchildsemi.com FAN7711 rev. 1.0.2 7 typical characteristics figure 4. start-up current vs. temp. figure 5. preheating current vs. temp. figure 6. ignition current vs. temp . figure 7. operating current vs. temp. figure 8. high-side quiescent current vs. temp. figure 9. shutdown current vs. temp. -40 -20 0 20 40 60 80 100 120 80 100 120 140 160 180 200 i st [ a] temperature [c] -40 -20 0 20 40 60 80 100 120 1.0 1.5 2.0 2.5 3.0 i ph [ a] temperature [c] -40 -20 0 20 40 60 80 100 120 8 10 12 14 16 i ig [ a] temperature [c] -40 -20 0 20 40 60 80 100 120 2.0 2.5 3.0 3.5 4.0 i dd [ma] temperature [c] -40 -20 0 20 40 60 80 100 120 0 20 40 60 80 100 i hst [ a] temperature [c] -40 -20 0 20 40 60 80 100 120 0 100 200 300 400 i sd [ a] temperature [c]
FAN7711 ballast control ic ? 2007 fairchild semiconductor corporation www.fairchildsemi.com FAN7711 rev. 1.0.2 8 typical characteristics (continued) figure 10. v dd uvlo vs. temp. figure 11. v bs uvlo vs. temp. figure 12. v dd clamp voltage vs. temp. figure 13. shutdown voltage vs. temp. figure 14. running frequency vs. temp. figure 15. preheating frequency vs. temp. -40 -20 0 20 40 60 80 100 120 10.4 10.8 11.2 11.6 12.0 12.4 12.8 13.2 13.6 14.0 14.4 temperature [c] v ddth [v] st+ st- -40 -20 0 20 40 60 80 100 120 8.0 8.4 8.8 9.2 9.6 10.0 temperature [c] v hsth [v] st+ st- -40 -20 0 20 40 60 80 100 120 14.8 15.0 15.2 15.4 15.6 15.8 16.0 16.2 v cl [v] temperature [c] -40 -20 0 20 40 60 80 100 120 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 v cphsd [v] temperature [c] -40 -20 0 20 40 60 80 100 120 48 50 52 54 56 58 f osc [khz] temperature [c] -40 -20 0 20 40 60 80 100 120 70 75 80 85 90 95 100 f pre [khz] temperature [c]
FAN7711 ballast control ic ? 2007 fairchild semiconductor corporation www.fairchildsemi.com FAN7711 rev. 1.0.2 9 typical characteristics (continued) figure 16. minimum dead time vs. temp. f igure 17. maximum dead time vs. temp. -40 -20 0 20 40 60 80 100 120 2.0 2.4 2.8 3.2 3.6 4.0 dt max [ s] temperature [c] -40 -20 0 20 40 60 80 100 120 0.6 0.8 1.0 1.2 1.4 1.6 1.8 dt min [ s] temperature [c]
FAN7711 ballast control ic ? 2007 fairchild semiconductor corporation www.fairchildsemi.com FAN7711 rev. 1.0.2 10 typical application information 1. under-voltage lockout (uvlo) function the FAN7711 has uvlo circuits for both high-side and low-side circuits. when v dd reaches v ddth(st+) , uvlo is released and the FAN7711 operates normally. at uvlo condition, FAN7711 consumes little current, noted i st . once uvlo is released, FAN7711 operates normally until v dd goes below v ddth(st-) , the uvlo hysteresis. at uvlo condition, all latche s that determine the status of the ic are reset. when the ic is in the shutdown mode, the ic can restart by lowering v dd voltage below v ddth(st-) . FAN7711 has a high-side gate driver circuit. the supply for the high-side driver is applied between v b and v s . to protect the malfunction of the driver at low supply voltage, between v b and v s , FAN7711 provides an additional uvlo circuit between the supply rails. if v b - v s is under v hsth(st+) , the driver holds low-state to turn off the high-side switch, as shown in figure 18. as long as v b -v s is higher than v hsth(st-) after v b -v s exceeds v hsth(st+) , operation of the driver continues. 2. oscillator the ballast circuit for a fluorescent lamp is based on the lcc resonant tank and a half-b ridge inverter circuit, as shown in figure 18. to accomplish zero-voltage switching (zvs) of the half-br idge inverter circuit, the lcc is driven at a higher frequency than its resonant frequency, which is determined by l, c s , c p , and r l , where r l is the equivalent lamp's impedance. figure 18. resonant inverter circuit based on lcc resonant tank the transfer function of l cc resonant tank is heavily dependent on the lamp impedance, r l , as illustrated in figure 19. the oscillator in FAN7711 generates effective driving frequencies to assist lamp ignition and improve lamp life longevity. accordingly, the oscillation frequency is changed in the following sequence: preheating freq.->ignition freq.-> normal running freq . before the lamp is ignited, the lamp impedance is very high. once the lamp is turned on, the lamp impedance significantly decreases. since the resonant peak is very high due to the high-resistance of the lamp at the instant of turning on the lamp, the la mp must be driven at higher frequency than the resonant frequency, shown as (a) in figure 19. in this mode, the current supplied by the inverter mainly flows through c p . c p connects both filaments and makes the current path to ground. as a result, the cu rrent warms up the filament for easy ignition. the amount of the current can be adjusted by controlling the oscillation frequency or changing the capacitance of c p . the driving frequency, f pre , is called preheating frequency and is derived by: after the warm-up, the FAN7711 decreases the frequency, shown as (b) of figure 19. this action increases the voltage of the lamp and helps the fluorescent lamp ignite. the ignition frequency is described as a function of cph voltage, as follows: where v cph is the voltage of cph capacitor. equation 2 is valid only when v cph is between 3v to 5v before FAN7711 enters running mode. once v cph reaches 5v, the internal latch records the exit from ignition mode. unless v dd is below v ddth(st-) , the preheating and ignition modes appear only once during lamp start transition. finally, the lamp is driven at a fixed frequency by an external resistor, rt, shown as (c) of figure 19. if v dd is higher than v ddth(st+) and uvlo is released, the voltage of rt pin is regulated to 4v. this voltage adjusts the oscillator's control current according to the resistance of r t . because this current and an internal capacitor set the oscillation frequency, the FAN7711 does not need any external capacitors. the proposed oscillation characteristic is given by: even in the active zvs mode, shown as (d) in figure 19, the oscillation frequency is not changed. the dead-time is varied according to the resonant tank characteristic. high-side driver low-side driver dead-time controller oscillator rt FAN7711 cph v dd v dc l c s c p equivalent lamp impedance r l lcc resonant tank filament v dd rt cph v b ho v s lo gnd FAN7711 rev. 1.00 (eq 1) . pre osc f 16 f = (eq 2) ( ) ig cph osc f 0.3 5-v 1 f ?? = + ?? (eq 3) 9 osc 410 f rt =
FAN7711 ballast control ic ? 2007 fairchild semiconductor corporation www.fairchildsemi.com FAN7711 rev. 1.0.2 11 figure 19. lcc transfer function in terms of lamp impedance 3. operation modes FAN7711 has four operation modes: (a) preheating mode, (b) ignition mode, (c) active zvs mode, and (d) shutdown mode, depicted in figure 20. the modes are automatically selected by th e voltage of cph capacitor, shown in figure 20. in modes (a) and (b), the cph acts as a timer to determine the preheating and ignition times. after the preheating and ignition modes, the role of the cph is changed to stabilize the active zvs control circuit. in this mode, the dead time of the inverter is selected by the voltage of cph. only when FAN7711 is in active zvs mode is it possible to shut off the whole system using cph pin. pulling the cph pin below 2v in active zvs mode, causes the FAN7711 to enter shutdown mode. in shutdown mo de, all active operation is stopped, except uvlo and some bias circuitry. the shutdown mode is triggered by the external cph control or the active zvs circuit. the active zvs circuit automatically detects lamp removal (open-lamp condition) and decreases cph voltage below 2v to protect the inverter switches from damage. figure 20. operation modes 3.1 preheating mode (t0~t1) when v dd exceeds v ddth(st+) , the FAN7711 starts operation. at this time, an internal current source (i ph ) charges cph. cph voltage increases from 0v to 3v in preheating mode. accordingly, the oscillation frequency follows the equation 4. in this mode, the lamp is not ignited, but warmed up for easy ignition. the preheating time depends on the size of cph: according to preheating process, the voltage across the lamp to ignite is reduced and the lifetime of the lamp is increased. in this mode, th e dead time is fixed at its maximum value. 3.2 ignition mode (t1~t2) when the cph voltage exceeds 3v, the internal current source to charge cph is increased about six times larger than i ph , noted as i ig , causing rapid increase in cph voltage. the internal oscillator decreases the oscillation frequency from f pre to f osc as cph voltage increases. as depicted in figure 20, lowering the frequency increases the voltage across the lamp. finally, the lamp ignites. ignition mode is defined when cph voltage lies between 3v and 5v. once cph voltage reaches 5v, the FAN7711 does not return to ignition mode, even if the cph voltage is in that range, until the FAN7711 restarts from below v ddth(st-) . since the ignition mode continues when cph is from 3v to 5v, the ignition time is given by: in this mode, dead time varies according to the cph voltage. 0db 20db 40db r l =100k r l =1k r l =500 preheating frequency (a) (b) (c) (d) dead-time control mode at fixed frequency r l =10k running frequency FAN7711 rev. 1.00 1 2 3 4 5 6 7 8 (a) preheating mode (b) ignition mode time cph voltage [v] 0 oscillation frequency preheating frequency:f pre running frequency: f osc time preheating mode running mode ignition mode (c) active zvs m ode 1 2 3 0 dead time[ s] (d) shutdown mode cph voltage varies by active zvs control circuit dt max dt min t0 t1 t2 t3 FAN7711 rev. 1.00 (eq 4) [.] preheat ph 3cph f sec i = (eq 5) [.] ignition ig 2cph t sec i =
FAN7711 ballast control ic ? 2007 fairchild semiconductor corporation www.fairchildsemi.com FAN7711 rev. 1.0.2 12 3.3 running and active zero-voltage switching (azvs) modes (t2~) when cph voltage exceeds 5v, the operating frequency is fixed to f osc by rt. however, active zvs operation is not activated until cph reaches ~6v. the FAN7711 prepares for active zvs operation from the instant cph exceeds 5v during t2 to t3. when cph becomes higher than ~6v at t3, the active zvs operation is activated. to determine the switching condition, FAN7711 detects the transition time of the output (v s pin) of the inverter. from the output-transition informati on, FAN7711 controls the dead time to meet the zvs condition. if zvs is satisfied, the FAN7711 slightly increases the cph voltage to reduce the dead time and to find optimal dead time, which increases the efficiency and decreases the thermal dissipation and emi of the inverter switches. if zvs fails, the FAN7711 decreases cph voltage to increase the dead time. cph voltage is adjusted to meet optimal zvs operation. during the active zvs mode, the amount of the charging/discharging current is the same as i ph . figure 21 depicts normal operation waveforms. figure 21. typical transient waveform from preheating to active zvs mode 3.4 shutdown mode if the voltage of capacitor cph is decreased below ~2.6v by an external application circuit or internal protection circuit, the ic enters shutdown mode. once the ic enters shutdown mode, this status continues until an internal latch is reset by decreasing v dd below v ddth(st-) . figure 22 shows an example of external shutdown control circuit. figure 22. external shutdown circuit the amount of the cph char ging current is the same as i ph , making it possible to shut off the ic using small signal transistor. FAN7711 provides active zvs operation by controlling the dead time according to the voltage of cph. if zvs fail s, even at the maximum dead time, FAN7711 stops driving the inverter. the FAN7711 thermal shutdown circuit senses the junction temperature of th e ic. if the temperature exceeds ~160c, the therma l shutdown circuit stops operation of the FAN7711. the current usages of shutdown mode and under- voltage lockout status are different. in shutdown mode, some circuit blocks, such as bias circuits, are kept alive. therefore, the current cons umption is slightly higher than during under-voltage lockout. 4. automatic open-lamp detection FAN7711 can automatically detect the open-lamp condition. when the lamp is opened, the resonant tank fails to make a closed-loop to the ground, as shown in figure 23. the supplied current from the v s pin is used to charge and discharge the charge pump capacitor, c p . since the open-lamp condition means resonant tank absence, it is impossible to meet zvs condition. in this condition, the power dissipation of the FAN7711, due to capacitive load drive, is estimated as: where f is driving frequency and v dc is dc-link voltage. 6v 5v 3v 2v active zvs activated dead time settling preheating period (filament warm-up) ignition running mode active zvs mode cph v dd v ddth(st+) v ddth(st-) time time time 0v out time 0v lamp voltage t=1/f osc zoom-in dead time perfect zvs t=1/f osc t=1/f osc t=1/f osc FAN7711 rev. 1.00 cph shutdown q1 3 4 cph gnd FAN7711 FAN7711 rev. 1.00 (eq 6) 2 dissipation p dc 1 p cvfw 2 [] =
FAN7711 ballast control ic ? 2007 fairchild semiconductor corporation www.fairchildsemi.com FAN7711 rev. 1.0.2 13 figure 23. current flow when the lamp is open assuming that c p , v dc , and f are 1nf, 311v, and 50khz, respectively; the power dissipation reaches about 2.4w and the temperature of FAN7711 is increased rapidly. if no protection is provided, t he ic can be damaged by the thermal attack. note that hard-switching condition during the capacitive-load drive causes lots of emi. figure 24 illustrates the waveforms during the open- lamp condition. in this condition, the charging and discharging current of c p is directly determined by FAN7711 and considered hard-switching condition. the FAN7711 tries to meet zvs condition by decreasing cph voltage to increase dead time. if zvs fails and cph goes below 2v, even though the dead time reaches its maximum value, FAN7711 shuts off the ic to protect against damage. to restart FAN7711, v dd must be below v ddth(st-) to reset an internal latch circuit, which remembers the status of the ic. figure 24. cph voltage variation in open-lamp condition 5. power supply when v dd is lower than v ddth(st+) , it consumes very little current, i st , making it possible to supply current to the v dd pin using a resistor with high resistance (r start in figure 25). once uvlo is released, the current consumption is increased and whole circuits are operated, which requires additional power supply for stable operation. the supply must deliver at least several ma. a charge pump circuit is a cost-effective method to create an additional power supply and allows c p to be used to reduce the emi. figure 25. local power supply for v dd using a charge pump circuit as presented in figure 25, when v s is high, the inductor current and c cp create an output transition with the slope of dv/dt. the rising edge of v s charges c cp . at that time, the current that flows through c cp is: this current flows along the path (1). it charges c vdd , which is a bypass capacitor to reduce the noise on the supply rail. if c vdd is charged over the threshold voltage of the internal shunt regulator, the shunt regulator is turned on and regulates v dd with the trigger voltage. when v s is changing from high to low state, c cp is discharged through dp2, shown as path (2) in figure 26. these charging/discharging operations are continued until FAN7711 is halted by shutdown operation. the charging current, i, must be large enough to supply the operating current of FAN7711. the supply for the high-side gate driver is provided by the boot-strap technique, as illustrated in figure 26. when the low-side mosfet connected between v s and gnd pins is turned on, the charging current for v b flows through d b . every low v s gives the chance to charge the c b . therefore c b voltage builds up only when FAN7711 operates normally. high-side driver low-side driver dead-time controller oscillator rt FAN7711 cph c vdd v dc l c s c p equivalent lamp impedance r l lcc resonant tank filament open v dd rt cph v b ho v s lo gnd c b c cp db dp2 dp1 charge pump FAN7711 rev. 1.00 6v 5v 3v 2v active zvs activated automatic shutdown preheating period (filament warm-up) ignition period running mode active zvs mode cph v dd v ddth(st+) v ddth(st-) out time time time 0v shutdown mode shutdown release restart FAN7711 rev. 1.00 FAN7711 v dc l c s c p equivalent lamp impedance r l lcc resonant tank filament open v dd rt cph v b ho v s lo gnd c b ccp db dp2 dp1 charge pump shunt regulator + r start c vdd (1) (2) dv/dt FAN7711 rev. 1.00 cp dv i c dt ? (eq 7)
FAN7711 ballast control ic ? 2007 fairchild semiconductor corporation www.fairchildsemi.com FAN7711 rev. 1.0.2 14 when v s goes high, the diode d b is reverse-biased and c b supplies the current to the high-side driver. at this time, since c b discharges, v b -v s voltage decreases. if v b -v s goes below v hsth(st-) , the high-side driver cannot operate due to the high-side uvlo protection circuit. c b must be chosen to be large enough not to fall into uvlo range due to the discharge during a half of the oscillation period, especially when the high-side mosfet is turned on. figure 26. implementation of floating power supply using the bootstrap method FAN7711 v dc l c s c p equivalent lamp impedance r l lcc resonant tank filament open v dd rt cph v b ho v s lo gnd c b c cp db dp2 dp1 charge pump shunt regulator + r start c vdd bootstrap circuit charging path FAN7711 rev. 1.00
FAN7711 ballast control ic ? 2007 fairchild semiconductor corporation www.fairchildsemi.com FAN7711 rev. 1.0.2 15 design guide 1. start-up circuit the start-up current (i st ) is supplied to the ic through the start-up resistor, r start . once operation starts, the power is supplied by the charge pump circuit. to reduce the power dissipation in r start , select r start as high as possible, considering the current requirements at start- up. for 220v ac power, the rectified voltage by the full- wave rectifier makes dc voltage, as shown in equation 8. the voltage contains lots of ac component due to poor regulation characteristic of the simple full-wave rectifier: considering the selected parameters, r start must satisfy the following equation: from equation 9, r start is selected as: note that if choosing the maximum r start , it takes long time for v dd to reach v ddth(st+) . considering v dd rising time, r start must be selected as shown in figure 30. another important concern for choosing r start is the available power rating of r start . to use a commercially available, low-cost 1/4 resistor, r start must obey the following rule: assuming v dc =311v and v cl =15v, the minimum resistance of r start is about 350k . when the ic operates in shutdown mode due to thermal protection, open-lamp protection, or hard-switching protection, the ic consumes shutdown current, i sd , which is larger than i st . to prevent restart during this mode, r start must be selected to cover i sd current consumption. the following equation must be satisfied: from equations 10 - 12; it is possible to select r start : (1) for safe start-up without restart in shutdown mode: (2) for safe start-up with restart from shutdown mode: if r start meets equation 14, restar t operation is possible. however, it is not recommended to choose r start at that range because v dd rising time could be long and it increases the lamp's turn-on delay time, as depicted in figure 27. figure 27. v dd build-up figure 28 shows the equivalent circuit for estimating t start . from the circuit analysis, v dd variation versus time is given by: where c vdd is the total capacitance of the bypass capacitors connected between v dd and gnd. from equation 15, it is possible to calculate t start by substituting v dd(t) with v ddth(st+) : in general, equation 16 can be simplified as: accordingly, t start can be controlled by adjusting the value of r start and c vdd . for example, if v dc =311v, r start =560k, c vdd =10f, i st =120a, and v ddth(st+) = 13.5v, t start is about 0.33s. figure 28. equivalent circuit during start (eq 8) [] [] dc v 2 220 v 311 v = ? (eq 9) () dc ddth st st start vv i r + ? > (eq 10) () dc ddth st start st vv r i + ? > (eq 11) () 2 dc cl start vv 1 w r4 [] ? < (eq 12) () dc ddth st start sd vv r i + ? > () () 2 dc ddth st dc cl start sd vv 4v v r i + ? ?<< (eq 13) (eq 14) () () dc ddth st dc ddth st start sd st vv vv r ii ++ ?? << FAN7711 rev. 1.00 v cl v ddth(st+) v ddth(st-) v dd time t start 0 () () /( ) () start vdd tr c dd dc start st vt v r i 1e ?? =?? ? (eq 15) (eq 16) dc start st ddth st start start vdd dd start st vriv trc vri () ln + ? ?? =? ? ? ?? () () start vdd ddth st start dc start st ddth st rcv t vriv + + ? ? ??? (eq 17) i st v dd rt cph gnd r start c vdd FAN7711 rev. 1.00
FAN7711 ballast control ic ? 2007 fairchild semiconductor corporation www.fairchildsemi.com FAN7711 rev. 1.0.2 16 2. current supplied by charge pump for the ic supply, the charge pump method is used in figure 29. since c cp is connected to the half-bridge output, the supplied current by c cp to the ic is determined by the output voltage of the half-bridge. when the half-bridge output shows rising slope, c cp is charged and the charging current is supplied to the ic. the current can be estimated as: where dt is the dead time and dv/dt is the voltage variation of the half-bridge output. when the half-bridge shows falling slope, c cp is discharged through dp2. total supplied current, i total , to the ic during switching period, t, is: from equation 19, t he average current, i avg , supplied to the ic is obtained by: for the stable operation, i avg must be higher than the required current. if i avg exceeds the required current, the residual current flows through the shunt regulator implemented on the chip, which can cause unwanted heat generation. therefore, c cp must be selected considering stable operation and thermal generation. for example, if c cp =0.5nf, v dc =311v, and f=50khz, i avg is ~7.8ma; it is enough current for stable operation. figure 29. charge pump operation 3. lamp turn-on time the turn-on time of the lamp is determined by supply build-up time t start , preheating time, and ignition time; where t start has been obtained by equation 17. when the ic's supply voltage exceeds v ddth(st+) after turn-on or restart, the ic operates in preheating mode. this operation continues until cph pin's voltage reaches ~3v. in this mode, cph capacitor is charged by i ph current, as depicted in figure 30. the preheating time is achieved by calculating: the preheating time is related to lamp life (especially filament); therefore, the characteristics of a given lamp should be considered when choosing the time. figure 30. preheating timer compared to the preheating time, it is almost impossible to exactly predict the ignition time, whose definition is the time from the end of the preheating time to ignition. in general, the lamp ignites during the ignition mode. therefore, assume that the maximum ignition time is the same as the duration of ignition mode, from 3v until cph reaches 5v. thus, ignition time can be defined as: note that, at ignition m ode, cph is charged by i ig , which is six times larger than i ph . consequently, total turn-on time is approximately: vdd build-time + preheating time + ignition time = dc cp cp v dv ic c dt dt = (eq 18) (eq 19) total cp dc iidtcv =? = ? (eq 20) total cp dc avg cp dc icv icvf tt ? == =?? v dc to v dd c cp dp1 dp2 c vdd i dp1 f=1/t half-bridge output i dp1 dp1 dp2 i dp1 =0 dt:dead time charging mode discharging mode to v dd c vdd c cp FAN7711 rev. 1.00 (eq 21) preheat ph cph t3 i = v dd rt cph gnd cph i ph FAN7711 rev. 1.00 () ignition ig ig cph cph t53 2 ii =? = (eq 22) (eq 23) () [.] ignition ig ig cph cph t53 2sec ii =? =
FAN7711 ballast control ic ? 2007 fairchild semiconductor corporation www.fairchildsemi.com FAN7711 rev. 1.0.2 17 4. pcb guide line component selection and placement on the pcb is very important when using power control ics. bypass the v cc to gnd as close to the ic terminals as possible with a low-esr/esl capacitor, as shown in figure 31. this bypassed capacitor (cbp) can reduce the noise from the power supply parts, such as start-up resistor and charge pump. the signal gnd must be separated from the power gnd. so, the signal gnd should be directly connected to the rectify capacitor using an individual pcb trace. in addition, the ground return path of the timing components (cph, rt) and v dd decoupling capacitor should be connected directly to the ic gnd lead and not via separate traces or jumpers to other ground traces on the board. these connec tion techniques prevent high- current ground loops from interfering with sensitive timing component operations and allow the entire control circuit to reduce common-mode noise due to output switching. figure 31. preheating timer hot pgnd sgnd cbp cph rt one point sgnd
FAN7711 ballast control ic ? 2007 fairchild semiconductor corporation www.fairchildsemi.com FAN7711 rev. 1.0.2 18 typical appli cation diagram figure 32. application circuit of 32w two lamps v dd rt cph r50 d50 d51 r55 r57 l3 v b ho v s lo m2 m3 c53 c57 c58 d52 d7 c5 lamp d1 d2 d3 d4 c1 c2 c3 c4 fuse gnd 8 7 6 5 1 2 3 4 out gnd zcd cs mot inv comp vcc ac input r1 r4 c7 r5 r9 r10 c11 d6 m1 FAN7711 8 7 6 5 1 2 3 5 l2 c55 c56 lamp ntc v dc r3 l1 r12 r11 r13 r54 tnr r8 r58 r56 FAN7711 rev. 1.00 rectified waveform rectified waveform fan7529 c6 d5 c8 c1 0 c9 r51 r52 c51 c50 r53 c52 c54 r6 r7 r2 zd 1
FAN7711 ballast control ic ? 2007 fairchild semiconductor corporation www.fairchildsemi.com FAN7711 rev. 1.0.2 19 component list for 32w two lamps part value note part value note resistor c55 15nf/630v miller capacitor r1 330k 1/2w c56 2.2nf/1kv miller capacitor r2 750k 1/4w c57 15nf/630v miller capacitor r3 100 1/2w c58 2.2nf/1kv miller capacitor r4 20k 1/4w diode r5 47 1/4w d1 1n4007 1kv,1a r6 10k 1/4w d2 1n4007 1kv,1a r7 50k 1/4w d3 1n4007 1kv,1a r8 47k 1/4w d4 1n4007 1kv,1a r9 0.3 1w d5 uf4007 ultra fast,1kv,1a r10 1m 1/4w d6 uf4007 ultra fast,1kv,1a r11 1m 1/4w d7 1n4148 100v,1a r12 12.6k 1/4w,1% d50 uf4007 ultra fast,1kv,1a r13 220k 2w d51 uf4007 ultra fast,1kv,1a r50 150k 1/4w d52 uf4007 ultra fast,1kv,1a r51 150k 1/4w zd1 in4746a zener 18v, 1w r52 150k 1/4w mosfet r53 90k 1/4w,1% m1 fqpf5n60c 500v,6a r54 10 1/4w m2 fqpf5n50c 500v,5a r55 47 1/4w m3 fqpf5n50c 500v,5a r56 47k 1/4w fuse r57 47 1/4w fuse 3a/250v r58 47k 1/4w tnr capacitor tnr 471 c1 47nf/275v ac box capacitor c2 150nf/275v ac box capacitor ntc c3 2200pf/3kv ceramic capacitor ntc 10d-09 c4 2200pf/3kv ceramic capacitor line filter c5 0.22f/630v miller capacitor lf1 40mh c6 12nf/50v ceramic capacitor transformer c7 22f/50v electrolytic capaci tor l1 0.94mh(75t:10t) ei2820 c8 1f/50v ceramic capacitor inductor c9 1f/50v ceramic capacitor l2 3.2mh(130t) ei2820 c10 0.1f/50v ceramic capacitor l3 3.2mh(130t) ei2820 c11 47f/450v electrolytic capacitor ic c50 10f/50v electrolytic capacitor u1 FAN7711 fairchild semiconductor c51 1f/50v ceramic capacitor u2 fan7529 fairchild semiconductor c52 0.47f/25v ceramic capacitor,5% c53 100nf/50v ceramic capacitor c54 470pf/1kv ceramic capacitor
FAN7711 ballast control ic ? 2007 fairchild semiconductor corporation www.fairchildsemi.com FAN7711 rev. 1.0.2 20 component list for 20w cfl note: 3. refer to the typical application circuit provided in figure 1. part value note part value note resistor diode r1 560k 1/4w d1 1n4007 1kv/1a r2 90k 1/4w d2 1n4007 1kv/1a r3 10 1/4w d3 1n4007 1kv/1a r4 47 1/4w d4 1n4007 1kv/1a r5 47 1/4w d5 uf4007 1kv/1a,ultra fast d6 uf4007 1kv/1a,ultra fast capacitor d7 uf4007 1kv/1a,ultra fast c1 22f/250v electrolytic capacitor inductor c2 10f/50v electrolytic capacitor l1 2.5mh (280t) ee1616s c3 470nf/25v miller capacitor mosfet c4 100nf/25v miller capacitor q1 fqpf1n50c 500v,1a c5 470pf/630v miller capacitor q2 fqpf1n50c 500v,1a c6 33nf/630v miller capacitor ic c7 3.9nf/1kv miller capacitor u1 FAN7711 fairchild semiconductor
FAN7711 ballast control ic ? 2007 fairchild semiconductor corporation www.fairchildsemi.com FAN7711 rev. 1.0.2 21 package dimensions 8-sop dimensions are in millimeter s unless otherwise noted. figure 33. 8-lead small outline package (sop) 4.92 0.20 0.194 0.008 0.41 0.10 0.016 0.004 1.27 0.050 5.72 0.225 1.55 0.20 0.061 0.008 0.1~0.25 0.004~0.001 6.00 0.30 0.236 0.012 3.95 0.20 0.156 0.008 0.50 0.20 0.020 0.008 5.13 0.202 max #1 #4 #5 0~8 #8 0.56 0.022 () 1.80 0.071 max0.10 max0.004 max min + 0.10 -0.05 0.15 + 0.004 -0.002 0.0 06 january 2001, rev. a sop8_dim.pdf
FAN7711 ballast control ic ? 2007 fairchild semiconductor corporation www.fairchildsemi.com FAN7711 rev. 1.0.2 22 package dimensions 8-dip dimensions are in inches and [milli meters] unless otherwise noted. figure 34. 8-lead dual in-line package (dip)
? 2007 fairchild semiconductor corporation www.fairchildsemi.com FAN7711 ballast control ic FAN7711 rev. 1.0.2 23

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