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r ev . 0.8 i w3623 p age 1 p r elimina r y s e p tembe r 10, 2012 IW3623 ac/dc digital power controller for high power factor off-line led drivers 1.0 features isolated ac/dc off-line led driver power factor > 0.95 for wide input voltage range 100 C 277v ac total harmonic distortion (thd) < 10% under 5% 100hz/120hz output current ripple resonant control to achieve high effciency led current foldback with external ntc small size design x small size input bulk capacitor x small size output capacitor x small transformer primary-side sensing eliminates the need for opto-isolator feedback and simplifes design tight led current regulation 5% under 0.5 second start-up time hot-plug led module support multiple protection features: x led open circuit protection x single-fault protection x over-current protection x led short-circuit protection x current sense-resistor-short-circuit protection x input over-voltage and brown-out protection 2.0 description the IW3623 is a high-performance ac/dc off-line power supply controller for led luminaires. the IW3623 combines power factor correction and led current regulation into one controller. it achieves pf > 0.95 and thd < 10% for 100C 277v ac input voltage range. the IW3623 operates in quasi-resonant mode to provide high effciency. the device uses iwatts advanced primary- side sensing technology to achieve excellent line and load regulation without secondary-feedback circuit. in addition, the IW3623s pulse-by-pulse waveform analysis technology allows accurate led current regulation. the IW3623 maintains stability over all operating conditions without the need for loop compensation components. 3.0 applications non-dimmable led lamps and luminaires optimized for up to 40w output power IW3623 ac/dc digital power controller for high power factor off-line led drivers
r ev . 0.8 i w3623 p age 2 p r eliminar y s eptember 10, 2012 ac input 1 14 cfg v in b drv IW3623 10 11 12 13 5 8 9 7 6 4 3 2 bi sense agnd pgnd v t fv sense fi sense f drv v cc asu v cb bv sense v out rtn ntc booster converter flyback converter figure 3.1 : typical application circuit IW3623 ac/dc digital power controller for high power factor off-line led drivers
r ev . 0.8 i w3623 p age 3 p r eliminar y s eptember 10, 2012 pin # name type pin description 1 bv sense analog input boost inductor voltage feedback 2 v in analog input rectifed ac line voltage feedback 3 bi sense analog input boost current sense (used for cycle-by-cycle peak current limit) 4 b drv output base drive for boost bjt 5 cfg analog in/out chooses input start-up voltage and brown-out shutdown voltage 6 asu output active start-up control 7 v cc power power supply for control logic and voltage sense for power-on reset circuitry 8 pgnd ground power ground 9 agnd ground signal ground 10 f drv output gate drive for flyback mosfet 11 fi sense analog input primary current sense (used for cycle-by-cycle peak current control and limit) 12 fv sense analog input auxiliary voltage sense (used for primary-side regulation and zvs) 13 v t analog input output power limit and shutdown control 14 v cb analog input boost output voltage feedback IW3623 1 2 3 14 13 12 4 11 v cb v in bi sense b drv fv sense fi sense bv sense v t 5 6 7 10 9 8 f drv asu v cc pgnd cfg agnd 4.0 pinout description IW3623 ac/dc digital power controller for high power factor off-line led drivers
r ev . 0.8 i w3623 p age 4 p r eliminar y s eptember 10, 2012 parameter symbol value units dc supply voltage range (pin 7, i cc = 20ma max) v cc -0.3 to 18 v dc supply current at v cc pin i cc 20 ma f drv output (pin 10) -0.3 to 18 v b drv output (pin 4) -0.3 to 4.0 v cfg input (pin 5) -0.3 to 4.0 v cfg output (pin 5) -0.3 to 18 v fv sense input (pin 12, i 10ma) -0.7 to 4.0 v bv sense input (pin 1, i 3ma) -0.7 to 4.0 v v in input (pin 2) -0.3 to 18 v v cb input (pin 14) -0.3 to 18 v fi sense input (pin 11) -0.3 to 4.0 v bi sense input (pin 3) -0.3 to 4.0 v asu output (pin 6) -0.3 to 18 v v t input (pin 13) -0.3 to 4.0 v power dissipation at t a 25c 900 mw maximum junction temperature t j max 150 c storage temperature t stg -65 to 150 c lead temperature during ir refow for 15 seconds t lead 260 c thermal resistance junction-to-pcb board surface temperature jb (note 1) 45 c/w esd rating per jedec jesd22-a114 2,000 v latch-up test per jedec 78 100 ma notes: note 1. jb [psi junction to board] provides an estimation of the die junction temperature relative to the pcb surface temperature. this data is measured at the ground pins (pin 8 and pin 9) without using any thermal adhesives. absolute maximum ratings are the parameter values or ranges which can cause permanent damage if exceeded. for maximum safe operating conditions, refer to electrical characteristics in section 6.0. 5.0 absolute maximum ratings IW3623 ac/dc digital power controller for high power factor off-line led drivers
r ev . 0.8 i w3623 p age 5 p r eliminar y s eptember 10, 2012 v cc = 12 v, -40c t a 85c, unless otherwise specifed (note 1) parameter symbol test conditions min typ max unit v in section start-up voltage threshold (note 2) v in_st t a = 25c, cfg resistor = 20k w 0.283 v t a = 25c, cfg resistor = 4.7k w 0.212 v brown-out threshold (note 3) v br_th t a = 25c, cfg resistor = 20k w 0.283 v t a = 25c, cfg resistor = 4.7k w 0.212 v over-voltage shutdown threshold v in_ovp t a = 25c, positive edge 1.512 1.68 1.848 v input impedance z in after start-up 5 k w v in range v in 0 1.8 v v cb section over-voltage shutdown threshold v cb_ovp t a = 25c, positive edge 1.62 1.8 1.98 v input impedance z cb after start-up 15 k w v cb range v cb 0 1.8 v fv sense section input leakage current i bvs(fvsense) v sense = 2v 1 a normal voltage threshold v sense(nom) t a = 25c, negative edge 1.521 1.536 1.551 v output ovp threshold (default) v sense(max) t a = 25c, negative edge 1.683 1.7 1.717 v bv sense section input leakage current i bvs(bvsense) v sense = 0.1v 1 a f drv section output low level on-resistance r ds_on_lo(fdrv) i sink = 5ma 16 w output high level on-resistance 1 r ds_on_hi(fdrv) i source = 5ma 25 w maximum switching frequency (note 4) f sw_fdrv(max) 200 khz b drv section output low level on-resistance r ds_on_lo(bdrv) i sink = 5ma 1 w maximum switching frequency (note 4) f sw_bdrv(max) if v in_a < 130mv 200 khz if v in_a > 130mv 90 khz output source current i b 90 ma 6.0 electrical characteristics IW3623 ac/dc digital power controller for high power factor off-line led drivers
r ev . 0.8 i w3623 p age 6 p r eliminar y s eptember 10, 2012 parameter symbol test conditions min typ max unit asu section maximum operating voltage v asu(max) 18 v resistance between v cc and asu r vcc_asu 830 k w v cc section maximum operating voltage v cc(max) 17 v start-up threshold v cc(st) 11.5 12.5 13.5 v under-voltage lockout threshold v cc(uvl) 6.0 6.5 7.0 v operating current i ccq 6.5 ma asu turn-off threshold v cc_asu_off 16.25 v fi sense section cc regulation threshold limit v reg_th(flyback) 1.4 v i sense short protection reference v rsens(eflyback) 0.16 v over-current limit threshold v ocp(flyback) 1.5 v bi sense section i sense short protection reference v rsense(boost) 0.15 v over-current limit threshold v ocp(boost) 1.9 v v t section power limit high threshold (note 5) v p_lim(hi) 0.56 v power limit low threshold (note 5) v p_lim(lo) 0.44 v shutdown threshold (note 5) v sh_th 0.22 v input leakage current i bvs(vt) v vt = 1.0v 1 a 6.0 electrical characteristics (cont.) v cc = 12 v, -40c t a 85c, unless otherwise specifed (note 1) IW3623 ac/dc digital power controller for high power factor off-line led drivers
r ev . 0.8 i w3623 p age 7 p r eliminar y s eptember 10, 2012 notes: note 1. adjust v cc above the start-up threshold before setting at 12v. note 2. v in pin voltage is greater than v in_st for more than three miliseconds. note 3. once v in pin maximum voltage is less than v br_th , ic will shut down immediately. note 4. operating frequency varies based on the line and load conditions. see the theory of operation section for more details. note 5. these parameters refer to digital preset values. they are not 100% tested. 6.0 electrical characteristics (cont.) v cc = 12 v, -40c t a 85c, unless otherwise specifed (note 1) parameter symbol test conditions min typ max unit pull-up current source i vt 90 100 110 a cfg section pull-up current source i cfg 90 100 110 a IW3623 ac/dc digital power controller for high power factor off-line led drivers
r ev . 0.8 i w3623 p age 8 p r eliminar y s eptember 10, 2012 7.0 typical performance characteristics 0.0 0.0 6.0 3.0 9.0 2.0 6.0 10.0 14.0 v cc (v) v cc supply start-up current (a) 4.0 8.0 12.0 to be determined figure 7.1 : v cc vs. v cc supply start-up current -50 12.0 -25 25 75 125 ambient temperature (c) v cc start-up threshold (v) 0 50 100 12.2 11.8 11.6 to be determined figure 7.2 : start-up threshold vs. temperature -50 -25 25 75 125 ambient temperature (c) % deviation of switching frequency from ideal 0 50 100 0.3 % -0.3 % -0.9 % -1.5 % to be determined figure 7.3 : % deviation of switching frequency to ideal switching frequency vs. temperature 1.98 -50 2.00 1.99 2.01 -25 25 75 125 ambient temperature (c) internal reference voltage (v) 0 50 100 to be determined figure 7.4 : internal reference vs. temperature IW3623 ac/dc digital power controller for high power factor off-line led drivers
r ev . 0.8 i w3623 p age 9 p r eliminar y s eptember 10, 2012 8.0 functional block diagram figure 8.1 : IW3623 functional block diagram v in bv sense v cc v t bi sense f drv gate driver enable 65k adc mux adc signal conditioning v cb asu 1m cfg 1.9v ocp boost control and constant current control base driver b drv 10k fv sense fi sense signal conditioning pgnd agnd 1.5v dac ocp i peak v in _ a v cb_a z in z cb + ? + ? + ? 100a m ux the IW3623 uses iwatts proprietary digital control technology, which consists of: 1) boost control circuit. 2) primary-side controlled fyback converter control circuit. it uses iwatts proprietary bjt boost switch control technique, which achieves high power factor and low thd within wide input voltage range at high effciency. the fyback controller operates with valley mode switching to achieve high effciency and minimum emi. it incorporates iwatts proprietary primary-feedback constant current control technology to achieve tight led current regulation. figure 8.1 shows the functional block diagram. the advanced digital control mechanism reduces system design time and improves reliability. the start-up algorithm makes sure the v cc supply voltage is ready before powering up the ic. the IW3623 provides multiple protection features for current limit, over-voltage protection, and over-temperature protection. IW3623 ac/dc digital power controller for high power factor off-line led drivers
r ev . 0.8 i w3623 p age 10 p r eliminar y s eptember 10, 2012 the IW3623 is a high performance ac/dc off-line power supply controller for non-dimmable led luminaires. the IW3623 actively shapes the input current to match the phase of the input voltage to increase power factor (pf) and reduce total harmonic distortion (thd). the led luminaires can easily conform to the iec harmonic current limit specifcations. the IW3623 operates in quasi-resonant mode to provide high effciency and simplify emi design. in addition, the IW3623 includes a number of key built-in protection features. using iwatts state-of-the-art primary-feedback technology, the IW3623 removes the need for secondary-feedback circuitry while achieving excellent line and load regulation. the IW3623 also eliminates the need for loop compensation components while maintaining stability over all operating conditions. pulse-by-pulse waveform analysis allows for accurate led current regulation. the two-stage design can achieve almost zero 2x line frequency output current ripple. 9.1 pin detail pin 1 C bv sense sense signal input from boost inductor winding, which provides the boost switching timing feedback used for valley mode switching. pin 2 C v in sense signal input from the rectifed line voltage. the input line voltage is scaled down using a resistor network. it is used for input over-voltage protection, brown-out protection, and start-up voltage setting. pin 3 C bi sense boost switch current sense. used for cycle-by-cycle peak current limit. pin 4 C b drv base drive for the boost switching circuit bjt switch. pin 5 C cfg confgure the start-up voltage and brown-out voltage through an external resistor during initial start-up. pin 6 C asu control the external high voltage start-up switch. pin 7 C v cc power supply for the controller during normal operation. the controller starts up when v cc reaches 12.5v (typical). the controller shuts down when the v cc voltage is below 6.5v (typical). high-frequency transients and ripples can be easily generated on the v cc pin due to power supply switching transitions, and line and load disturbances. excess ripples and noises on v cc may lower the controller function performance. a decoupling capacitor should be connected between the v cc pin and agnd/pgnd. it is suggested that a ceramic capacitor of minimum 0.1f is connected to the v cc pin as closely as possible. pin 8 C pgnd power ground. this pin should be connected to the negative terminal of the bulk capacitor. pin 9 C agnd analog ground. this pin should be connected to the pgnd. pin 10 C f drv gate drive for the fyback circuit mosfet switch. pin 11 C fi sense primary current sense. used for cycle-by-cycle peak current control. pin 12 C fv sense sense signal input from auxiliary winding, which provides the secondary voltage feedback used for output regulation. pin 13 C v t external power limit and shutdown control. if the shutdown control is not used, this pin should be connected to gnd via a 20k w resistor. pin 14 C v cb sense signal input from the boost output voltage. v cb is used for boost output voltage regulation. it is also used for boost output over-voltage protection. 9.0 theory of operation IW3623 ac/dc digital power controller for high power factor off-line led drivers
r ev . 0.8 i w3623 p age 11 p r eliminar y s eptember 10, 2012 9.2 ic start-up prior to start-up, the v cc capacitor is charged up through active start-up circuit controlled by the asu pin, and through the v in and v cb to v cc internal diodes. when v cc is fully charged to a voltage higher than the start-up threshold v cc(st) , the enable signal becomes active and enables the control logic, as shown in figure 9.1. the IW3623 detects the input voltage at v in pin. if the input voltage reaches the start-up threshold, then constant output current mode is enabled and the output-voltage starts to ramp up. when the output-voltage rises above the forward-voltage of led, the controller operates in constant current mode. the asu is disabled after the fyback operates for about 50 miliseconds. the IW3623 implements an output current soft-start. the output current starts at 5% and move quickly to 100% level. this feature helps to eliminate output current overshoot during the start-up. . v cc v cc(st) enable start-up sequencing v in asu figure 9.1 : start-up sequencing diagram 9.3 boost operation ac + br z in l c r vin d 1 d 2 v cb_a c b r 3 q c r s b drv bv sense bi sense v in_a r vcb z cb v bus figure 9.2 : boost schematic the pfc control block provides an on-time (t on ) controlled, valley mode switching power factor correction controller. the t on is determined by the v in_a and v cb_a voltage. v cb_a is scaled down from the bus voltage. v in_a is scaled down from the rectifed input voltage. after power up, v in_a voltage is monitored. if v in_a voltage is higher than v in_st, ic will send out driver signal to the boost and fyback switch. the frequency of boost circuit is limited to below 90khz when v in_a is greater than 0.13v. it is limited to below 200khz when v in_a is less than 0.13v. the bjt emitter resistor provides over-current protection for boost circuit: i qc(max) = v ocp (boost) ? rs (9.1) to minimize bjt turn-on loss and reduce emi, the bjt is turned on at valley point of collector pin voltage. this valley signal is sensed by the bv sense pin connected to a secondary winding on boost choke. the dc bus voltage is typically 30v above the peak of line voltage. the minimum value is clamped to 200v (see section 9.5 for bus voltage calculation). 9.4 bjt drive one important feature of the IW3623 is that it directly drives a bjt switching device in boost circuit. in the switching operation mode, the IW3623 drives the bjt with dynamic base current control to optimize performance. the bjt base current ranges from 10ma to 90ma, and it is dynamically controlled according to the bjt peak conducting current. the higher the bjt current, the higher the base current. 9.5 v in and v cb resistors the v in and v cb pin resistors are chosen primarily to scale down the ac line voltage and input bulk capacitor voltage of the fyback circuit. the typical scale factor k cb and k in is: k cb and k in = 0.004 for 230v v ac (rms) k cb and k in = 0.033 for 277v v ac (rms) the scale factor can be adjusted to optimize effciency and power factor. the r vin and r vcb resistance can be equated by r vin = z in / k in C z in and r v cb = z cb / k cb - z cb the internal impedance z in is 5k? 5%, z cb is 15k? 5%. for example, with v in (rms) = 230v, the v in and v cb pin resistors should add up to IW3623 ac/dc digital power controller for high power factor off-line led drivers
r ev . 0.8 i w3623 p age 12 p r eliminar y s eptember 10, 2012 r vin = 5k? / 0.004 C 5k? = 1245k? r vcb = 15k? / 0.004 C 15k? = 3735k? the relationship between v in and v cb pin voltage for boost output voltage regulation is: v cb_a = v in_a(max) + 0.12v the dc bus voltage is determined by: v bus = v cb_a /k cb v cb_a regulation range is from 0.8v to 1.48v (for example, when k cb = 0.004, v bus will be clamped to minimum 0.8/0.004 = 200v). 9.6 primary feedback figure 9.3 illustrates a simplifed fyback converter. when the switch q 1 conducts during t on (t) , the current i g (t) is directly drawn from the rectifed sinusoid v g (t) . the energy e g (t) is stored in the magnetizing inductance l m . the rectifying diode d 1 is reverse biased and the load current i o is supplied by the secondary capacitor c o . when q 1 turns off, d 1 conducts and the stored energy e g (t) is delivered to the output. + v in (t) t s (t) i o v o v aux n:1 d1 q1 v aux c o v g (t) i g (t) + ? i in (t) i d (t) figure 9.3 : simplifed flyback converter in order to tightly regulate the output voltage, the information about the output voltage and load current needs to be accurately sensed. in the dcm fyback converter, this information can be read via the auxiliary winding or the primary magnetizing inductance (l m ). during the q 1 on-time, the load current is supplied from the output flter capacitor c o . the voltage across l m is v g (t) , assuming the voltage dropped across q 1 is zero. the current in q 1 ramps up linearly at a rate of: () () gg m di t v t dt l (9.2) at the end of on-time, the current has ramped up to: _ () () g on g peak m vt t it l (9.3) this current represents a stored energy of: 2 _ () 2 m g g peak l e it (9.4) when q 1 turns off, i g (t) in l m forces a reversal of polarities on all windings. ignoring the communication-time caused by the leakage inductance l k at the instant of turn-off, the primary current transfers to the secondary at a peak amplitude of: _ () () p d g peak s n it i t n (9.5) assuming the secondary winding is master and the auxiliary winding is slave. v aux 0v v aux = -v in x n aux n p v aux = v o x n aux n s figure 9.4 : auxiliary voltage waveforms the auxiliary voltage is given by: () aux aux o s n v vv n (9.6) and refects the output voltage as shown in figure 9.4. the voltage at the load differs from the secondary voltage by a diode drop and ir losses. the diode drop is a function of current, as are ir losses. thus, if the secondary voltage is always read at a constant secondary current, the difference between the output voltage and the secondary voltage is a fxed v . furthermore, if the voltage can be read when the secondary current is small, for example, at the knee of the auxiliary waveform (see figure 9.4), then v is also small. with the IW3623, v can be ignored. the real-time waveform analyzer in the IW3623 reads the auxiliary waveform information cycle by cycle. the part then generates a feedback voltage v fb . the v fb signal precisely represents the output voltage and is used to regulate the output voltage. IW3623 ac/dc digital power controller for high power factor off-line led drivers
r ev . 0.8 i w3623 p age 13 p r eliminar y s eptember 10, 2012 9.7 valley mode switching in order to reduce switching losses in the mosfet, bjt, and to lower emi, the IW3623 employs valley mode switching during constant output current operation for both mosfet and bjt. in valley mode switching, the mosfet and bjt switches are turned on at the point where the resonant voltage across the drain and source of the mosfet (or across the collector and emitter of bjt) is at its lowest point (see figure 9.5). by switching at the lowest v ds , the switching loss is minimized. g a t e v d s figure 9.5 : valley mode switching turning on at the lowest v ds generates the lowest dv/dt, thus valley mode switching can also reduce emi. at each of the switching cycles, the falling edge of fv sense is checked. if the falling edge of fv sense is not detected, the off-time is extended until the falling edge of fv sense is detected. 9.8 led current regulation after soft-start has been completed, the digital block measures the output conditions. when the fv sense pin voltage is less than 1.538v, the control system works in constant current (cc) mode. the device regulates the output current i out to its nominal value. the IW3623 incorporates a patented primary-side only constant current regulation technology. the IW3623 regulates the output current at a constant level regardless of the output voltage, while avoiding continuous conduction mode. to achieve this regulation, the IW3623 senses the load current indirectly through the primary current. the primary current is detected by the fi sense pin through a resistor from the mosfet source to ground. i p i s i o t on t of f t r t s figure 9.6 : constant led current regulation the fi sense resistor determines the maximum current output of the power supply. the output current of the power supply is determined by: out = i sense r 1 2 ps n reg_th v r t s t (9.7) where n ps is the turns ratio of the primary and secondary windings and r sense is the fi sense resistor. ic will set v reg_th to: s reg_th t v = r t k cc (9.8) where k cc is equal to 0.7v. from equation 9.7 and 9.8 we get: out = k cc i sense r 1 2 ps n (9.9) from equation 9.9, r sense can be calculated based on i out and n ps . 9.9 constant voltage mode if fv sense pin voltage is higher than 1.538v, the control system will change t on and t off to regulate the fv sense voltage to 1.538v. the device operates in constant voltage (cv) mode. the output current i out will be lower than nominal. if less than 0.2v is detected on fv sense, it is assumed that the auxiliary winding of the transformer is either open or shorted and the IW3623 shuts down. the IW3623 normally operates in a fxed frequency pwm or critical discontinuous conduction mode when i out is greater than approximately 10% of the specifed maximum load current. as the output load i out is reduced, the IW3623 ac/dc digital power controller for high power factor off-line led drivers
r ev . 0.8 i w3623 p age 14 p r eliminar y s eptember 10, 2012 on-time t on is decreased. during this mode the pwm switching frequency is between 30khz and 130 khz, depending on the line and load conditions. at the moment that the load current drops below 10% of nominal, the controller transitions to pulse frequency modulation (pfm) mode. thereafter, the on-time is modulated by the line voltage and the off-time is modulated by the load current. the device automatically returns to pwm mode when the load current increases. 9.10 cfg pin the cfg pin is used to set up start-up and brown-out voltage. the cfg pin outputs 100a current source after v cc reaches the start-up threshold. the start-up voltage is confgured based on the information in table 9.1. cfg option number cfg pin resistor v in_st v br_th value tolerance 1 20k w 5% 0.283v 0.283v 2 4.7k w 5% 0.212v 0.212v table 9.1 cfg pin resistor ic will start sending out drive signal for pfc and fyback circuit after v in is greater than v in_st for three miliseconds. 9.11 pcl, ocp and srsp protection peak-current limit (pcl), over-current protection (ocp), and sense-resistor short protection (srsp) are features built into the IW3623. with the fi sense pin the IW3623 is able to monitor the primary-peak current of the fyback circuit. this allows for cycle-by-cycle peak current control and limit. when the primary-peak current multiplied by the fi sense sense resistor is greater than 1.5v, over-current is detected and the ic immediately turnes off the gate drive until the next cycle. the output driver sends out switching pulse in the next cycle, and the switching pulse continues if the ocp threshold is not reached; or, the switching pulse turns off again if the ocp threshold is still reached. the bi sense pin provides the same protection mechanism for the boost circuit. the bi sense ocp threshold is 1.9v. if the fi sense sense resistor is shorted, there is a potential danger of the over-current condition not being detected. thus the ic is designed to detect this sense-resistor short fault after the start-up, and shut down immediately. the v cc is discharged since the ic remains biased. in order to avoid overcharging the output voltage, the IW3623 employs an extended discharge time before restart. if the bi sense resistor is shorted, the IW3623 cannot determine the base drive current of the boost bjt, which can ultimately result in the boost bjt exceeding its safe operating area. thus the ic is designed to detect this boost sense-resistor short fault during the configuration state. when the IW3623 detects a boost-sense-resistor- short fault for two consecutive detection cycles, then the ic shuts down immediately. the v cc is discharged since the ic remains biased. to prevent over-stress on the boost circuit components, the IW3623 employs an extended discharge time before restart. initially if v cc drops below the uvlo threshold, the controller resets itself and then initiates a new soft-start cycle. 9.12 output over-voltage/led open protection the IW3623 includes a function that protects against an output over-voltage (ovp). the output voltage is monitored by the fv sense pin. if the voltage at this pin exceeds its over-voltage threshold the IW3623 shuts down immediately. however, the ic remains biased which discharges the v cc supply. in order to avoid overcharging the output voltage, the IW3623 employs an extended discharge time before restart. initially if v cc drops below the uvlo threshold, the controller resets itself and then initiates a new soft-start cycle. under the output over-voltage fault condition, the controller tries to start up for three consecutive times. if all three start-up attempts fail, the controller enters the inactive mode, during which the controller does not respond to v cc power-on requests. the controller is activated again after it sees 29 start-up attempts. the controller can also be reset to the initial condition if v cc is discharged. typically, this extended discharge time is around three to fve seconds. this extended discharge time allows the IW3623 to support hot-plug led modules without causing dangerously high output voltages while maintaining a quick recovery. in additional to the output over-voltage protection, the IW3623 also employs the constant output voltage regulation operation mode. this allows the output voltage sustains at the reference level if the led module is disconnected from the driver and the output voltage does not overshoot above the over-voltage protection threshold. IW3623 ac/dc digital power controller for high power factor off-line led drivers
r ev . 0.8 i w3623 p age 15 p r eliminar y s eptember 10, 2012 9.13 input and bulk over-voltage the IW3623 supports the over-voltage protection from ac input and boost output. if the input voltage sense the v in pin voltage is higher than 1.68v for continuous 2ms within every 16ms period, and this condition lasts for eight consecutive times, the IW3623 shuts down both the boost and fyback driving signals. when v cc drops below the uvlo threshold, the controller resets itself and then initiates a new soft-start cycle. if the boost voltage sense v cb pin voltage is higher than 1.8v for continuous 128ms, the IW3623 shuts down both the boost and fyback driving signals. when v cc drops below the uvlo threshold, the controller resets itself and then initiates a new soft-start cycle. under both the input and boost over-voltage fault conditions, the controller tries to start up for three consecutive times. if all three start-up attempts fail, the controller enters the inactive mode, during which the controller does not respond to v cc power-on requests. the controller is activated again after it sees 29 start-up attempts. the controller can also be reset to the initial condition if v cc is discharged. typically, this extended discharge time is around three to fve seconds. 9.14 input brown-out protection after start-up, if v in pin maximum voltage is below v br_th , ic will shut down the pfc and fyback circuit. ic will enter an inactive mode, during which the controller does not respond to the v cc power-on requests. the controller is activated again after it sees 29 start-up attempts. 9.15 output short protection the IW3623 includes a function that protects against an output short-circuit fault. if the voltage at the fv sense pin is below 0.228v, the IW3623 shuts down immediately. after the shutdown, the IW3623 remains powered, which discharges the v cc . in order to avoid excessive power stress due to auto-restart, the IW3623 employs an extended discharge time. to support applications with high output capacitance, output short protection is not activated in the initial led current soft start period. this allows the voltage to build up in the output capacitor without mis-triggering the protection. 9.16 over-temperature protection if an ntc thermistor is connected between the v t pin and gnd, the IW3623 is able to detect and protect against an over-temperature event. the IW3623 provides an i vt to the v t pin and detects the voltage on the pin. based on this voltage, the IW3623 can monitor the resistance of the ntc thermistor, which is related to the temperature of the thermistor. as the v t pin voltage reduces, the IW3623 reduces the power in boost and fyback converter. v t pin voltage percentage of nominal output current (%) 0.0 0.2 0.4 0.6 0.8 1.0 0 20 40 60 80 100 v p-lim(hi) v p-lim(lo) v sh-th figure 9.7 : v t pin voltage vs. % of nominal output current when the v t pin voltage reaches v p-lim(hi) the output current begins to reduce linearly from 100% to 20% as shown in figure 9.7. at v p-lim(lo) the output current will be clamped to 1%. if the v t pin further decreases to below v sh_th, the IW3623 will shut down. IW3623 ac/dc digital power controller for high power factor off-line led drivers
r ev . 0.8 i w3623 p age 16 p r elimina r y s e p tembe r 10, 2012 IW3623 ac/dc digital power controller for high power factor off-line led drivers part number options package description IW3623-00 soic-14 tape & reel 1 note 1: tape & reel packing quantity is 2,500/reel. 10.0 physical dimensions figure 10.1 : physical dimensions, 8-lead soic package compliant to jedec standard ms12f controlling dimensions are in inches; millimeter dimensions are for reference only this product is rohs compliant and halide free. soldering temperature resistance: [a] package is ipc/jedec std 020d moisture sensitivity level 1 [b] package exceeds jedec std no. 22-a111 for solder immersion resistance; package can withstand 10 s immersion < 270?c dimension d does not include mold flash, protrusions or gate burrs. mold flash, protrusions or gate burrs shall not exceed 0.15 mm per end. dimension e does not include interlead flash or protrusion. interlead flash or protrusion shall not exceed 0.25 mm per side. the package top may be smaller than the package bottom. dimensions d and e are determined at the outermost extremes of the plastic bocy exclusive of mold flash, tie bar burrs, gate burrs and interlead flash, but including any mismatch between the top and bottom of the plastic body. 14-lead soic package coplanarity 0.10 (0.004) 14 8 7 1 seating plane a1 e h b d e a c l top view side views inches symbol millimeters min 0.004 a1 max min max 0.010 0.10 0.25 0.053 a 0.069 1.35 1.75 0.013 b 0.020 0.33 0.51 0.007 c 0.010 0.19 0.25 0.337 d 0.344 8.55 8.75 0.150 e 0.157 3.80 4.00 0.050 bsc e 1.27 bsc 0.228 h 0.244 5.80 6.20 0.086 n 0.094 2.18 2.39 0.016 l 0.050 0.40 1.27 0 8 m 3.20 3.00 0.118 0.126 0 0 8 11.0 ordering information IW3623 ac/dc digital power controller for high power factor off-line led drivers

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