View BW9910A_7543091.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

bw9910/a high brightn ess led driver ?2012 bruckewell technology corp., ltd. 1 www.bruckewell - semi.com/ features ? efficiency > 90% ? u niversal rectified 85 v ac to 265 v ac input range ? constant current led driver ? application s from a few ma to more than 1.0a ? led string from one to hundreds of diodes ? pwm low - frequency dimming v ia pwm_d pin ? input voltage surge rating s up to 500v ? internal over temperature protection (otp) ? 7.5v mosfet drive bw9910 10v mosfet drive bw9910 a typical applications ? a c/d c or d c/dc led driver application s ? rgb b acklighting led driver ? back l ighting of f lat p anel d isplays ? general purpose cons tant current source ? signage and d ecorative led l ighting ? buck/buck - boost/boost led driver ? t8/t9/t10 led tubes ? e26/e27 led bulbs product description the bw9910 / bw9910 a is a pwm high - efficiency led driver control ic. it allows efficient opera tion of h igh b rig htness (hb) leds from voltage sources ranging from 85v ac up to 265v ac . the bw9910 / bw9910 a controls an external mosfet at fixed switching frequency up to 300khz. the frequency can be programmed using a single resistor. the led string is driven at constant c urrent rather than constant voltage, thus providing constant light output and enhanced reliability. the output current can be programmed between a few m a and up to more than 1.0a. the bw9910 / bw9910 a uses a rugged high voltage junction isolated process tha t can withstand an input voltage surge of up to 50 0v. output current to an led string can be programmed to any value between zero and its maximum value by applying an external control voltage at the line ar dimming control input of the bw9910 / bw9910 a . the b w9910 / bw9910 a provides a low - frequency pwm dimming input that can accept an external contro l signal with a duty ratio of 0 % ~ 100% and a frequency of up to a few k hz. the bw9910 a allows wider range of external mosfet which has lower r ds ( on ) (d rain - s ource o n resistance ) at h ighe r v gs . the bw9910 / bw9910 a is available in sop - 8 and so8 - ep packages. typical application circuit
bw9910/a high brightness led driver ?2012 bruckewell technology corp., ltd. 2 www.bruckewell - semi.com/ pin assignments and ordering information device v cs tolerance packaging quantity of tape & reel bw9910 mst 10% sop - 8 3000 bw9 910 mpt 10% so8 - ep 3000 bw9910 a mst 10% sop - 8 3000 bw9910 a mpt 10% so8 - ep 3000 pin descriptions sop - 8 so8 - ep pin name function input voltage pin. 1 1 v in dc input supply voltage. current sensing input pin . 2 2 c s sens es led string current . ground pin . 3 3 gnd device ground. gate driver output pin . 4 4 gate drives the gate of the external mosfet. pwm dimming input pin . 5 5 pwm_d low f requency pwm d imming pi n, also e nable input. internal 200k pull - down resistor to gnd . internal/external supply voltage pin. 6 6 v dd internally regulated supply voltage. 7.5v nominal for the bw9910 and 10v nominal for the bw9910 a . this pin can supply up to 1 .0 ma for external circuitry. a sufficient storage c apacitor is used to provide storage when the rectified ac input is near the zero crossings . linear dimming input pin. 7 7 ld linear d imming by changing the current limit threshold at current sensing comparator . oscillator control pin. 8 8 r osc a resistor conne cted between this pin and gnd sets the pwm frequency. exposed pad. n/a ep ep pad package bottom. connect to gnd directly underneath the package.
bw9910/a high brightness led driver ?2012 bruckewell technology corp., ltd. 3 www.bruckewell - semi.com/ absolute maximum rating s ( note 1 ) symbol parametar ratings unit v indc dc input supply vol tage range, v in to gnd - 0. 5 ~ + 5 2 0 v v cs cs input pin voltage range relative to gnd - 0. 3 ~ + 0.45 v v ld ld input pin voltage range relative to gnd - 0. 3 ~ + (v dd + 0.3) v v pwm_d pwm_d input pin voltage range relative to gnd - 0. 3 ~ + (v dd + 0.3) v v gate gat e output pin voltage range relative to gnd - 0. 3 ~ + (v dd + 0.3) v continuous power dissipation ( t a +25c) 8 pin so (de - rat ing 6.3mw/ c above +25 c ) 0.63 w 8 pin so - ep (de - rating 16 mw/ c above +25 c ) 1.6 w t j junction temperature +150 ? t st g storage temperature range - 65 ~ + 150 ? ja junction - to - ambient thermal resistance for sop - 8 165 ? /w ja (ep) junction - to - ambient thermal resistance for so8 - ep 60 ? /w note : 1 . e xceeding these ratings could cause damage to the device. a ll voltages are with respect to ground. currents are positive into , n egative out of the specified termina l. recommended operating conditions symbol parametar min. max. unit bw9910 15 500 v indc dc input supply voltage range, v in to gnd bw9910 a 20 50 0 v v en(lo) pwm_d input pin low voltage range relative to gnd 0 1.0 v v en(hi) pwm_d input pin high voltage range relative to gnd 2.4 v dd v t a a mbient tempe rature range for sop - 8 package (note 2 ) bw9910 mst - 40 +85 ? t a(ep) a mbient temperature range for so8 - ep package (note 2 ) bw9910 mpt - 40 +105 ? note : 2 . maximum ambient temperature range is limited by allowable power d issipation. the e xposed pad so 8 - ep with its lower thermal impedance allows the variants using this package to extend the allowable maximum ambient temperature range.
bw9910/a high brightness led driver ?2012 bruckewell technology corp., ltd. 4 www.bruckewell - semi.com/ e lectrical characteristics (over recommended operating conditions unless otherwise specified. t a + 25c ) parameter symbol min. typ. max. unit condition 15 500 bw9910 input dc supply voltage range v indc 20 500 v bw9910 a dc input voltage 0.5 1 .0 bw9910 shut down mode supply current i i nsd 0.65 1.20 ma bw9910 a pin pwm_d to gnd, v in v in dc (min) (note 3) 7.0 7.5 8.0 bw9910 internally regulated voltage v dd 9.5 10.0 11.0 v bw9910 a v in v in dc (min) ~ 500v (note 3) , l dd( ext) 0, gate pin open bw9910 v dd current available for external circuitry ( note 4 ) i dd( ext ) 1.0 ma bw9910 a v in v in dc (min) ~ 100v (note 3) 6.4 6. 7 7. 0 bw9910 v dd under voltage lockout threshold v uvlo 8.4 9.0 9.6 v bw9910 a v dd rising 500 bw9910 v dd under voltage lockout hysteresis ?v uvlo 650 mv bw9910 a v dd falling pwm_d pull - down resistance r pwm_d 1 50 2 00 2 50 k v pwm _d 5v current sensing pull in threshold voltage v cs 225 250 275 mv full ambient temperature range (note 5) gate high output voltage v gat e ( h i ) v dd - 0.3 v dd v i out 10ma gate low output voltage v gat e ( l o ) 0 0.3 v i out - 10ma f osc 1 20 2 6 3 2 r osc 1m oscillator frequency f osc 2 80 100 120 khz r osc 226k maximum o scillator pwm d uty c ycle d max (hf) 100 % f pwm (hf) 25khz, at gate , cs tie to gnd. linear d imming pin voltage range v ld 0 250 mv full ambient temperature range (note 5) , v in 20 v current sensing blanking interval t blank 1 6 0 250 440 ns v cs 0.5 v delay from cs trip to gate lo w t delay 300 ns v in 20v, v ld 0.15 v , v cs 0 v ~ 0.22v after t blank gate output rise time t rise 30 50 ns c gate 500pf gate output fall time t fall 30 50 ns c gate 500pf thermal s hut down t sd 1 5 0 c thermal shut down hysteresi s ? t sd 50 c note : 3. v in dc (min) for the bw9910 is 15v and for the bw9910 a it is 20v. 4 . a lso limited by package power dissipation limit, whichever is lower. 5. full ambient temperature range for bw9910 mst and bw9910 a mst is - 40 to +85c; for bw9910 m pt and bw9910 a mpt is - 40 to +105c.
bw9910/a high brightness led driver ?2012 bruckewell technology corp., ltd. 5 www.bruckewell - semi.com/ functional block diagram
bw9910/a high brightness led driver ?2012 bruckewell technology corp., ltd. 6 www.bruckewell - semi.com/ application information ac - dc off - line application the bw9910/BW9910A is a low cost off - line buck or boost converter control ic specifically designed for driving multi - led stings or arrays. it can be operated from either universal ac line or any dc voltage between 15v and 500v. optionally, a passive power factor correction circuit can be used in order to pass the ac harmonic limits set by en61000 - 3 - 2 c lass c for lighting equipment having inpu t power less than 25w. the bw9910/BW9910A can drive up to hundreds of hb leds or multiple strings of hb leds. the led arrays can be configured as a series or series/parallel connection. the bw9910/BW9910A regulates constant current that ensures controlled brightness and spectrum of the leds, and extends their lifetime , and also allows pwm control of brightness via an enable (pwm_d) pin . the bw9910 / bw9910 a can also control brightness of leds by programming continuous output current of the led driver (so - cal led linear dimming) when a control voltage is applied to the ld pin. the bw9910 / bw9910 a is offered in standard 8 - pin soic and soic - ep package s . the bw9910 / bw9910 a has a built - in high - voltage linear regulator that powers all internal circuits and can also serve as a bias supply for low voltage and low power external circuitry. led driver operation the bw9910 / bw9910 a can control all basic types of converters, isolated or non - isolated, operating in continuous or discontinuous conduction mode. when the gate signal turns on the external power mosfet, the led driver stores the input energy in an inductor or in the primary inductance of a transformer and, depending on the converter type, may partially deliver the energy directly to leds . the energy stored in the magnetic component is further delivered to the output during the off - cycle of the power mosfet producing current through the string of leds (fly - back mode of operation). when the voltage at the v dd pin exceeds the v uvlo threshold voltage, the gate drive is enabled. the output current is controlled by means of limiting peak current in the external power mosfet. a current sensing resistor is c onnected in series with th e s ource terminal of the mosfet. the voltage from the sensing resistor is appli e d to the c s pin of the bw9910 / bw9910 a. when the voltage at cs pin exceeds a peak current sensing threshold voltage, the gate drive signal terminates, and the power mosfet turns off. the threshold is internally set to 250mv, or it can be programmed externally by a ppl ying voltage to the ld pin. when the soft - start function is required, a capacitor can be connected to the ld pin to allow this voltage to ramp at a desired rate , therefore, assuring that output current of the led ramps gradually . additionally , a simple pas sive power factor correction circuit, consisting of 3 diodes and 2 capacitors, can be added as shown in the typical applica tion circuit diagram of figure 6 . supply current a current of 1 .0 ma is needed to start the bw9910 / bw9910 a. as shown in the block dia gram on page 5 , this current is internally generated in the bw9910 / bw9910 a without using bulky startup resistors typically required in the off - line applications. moreover, in many applications the bw9910 / bw9910 a can be continuously powered using its intern al linear regulator that provides a regulated voltage of 7.5v /10v for all internal circuits . setting lighting output when the buck converter topology of figure 5 is selected, the peak cs voltage is a good representation of the average current in the led. however, there is a certain error associated with this current sensing method that needs to be accounted for. this error is introduced by the difference between the peak and the average current in the inductor. for example , if the peak - to - peak ripple curre nt in the inductor is 150ma, to get a 500ma led current, the sens ing resistor should be as follows : 0.43 dimming dimming can be accomplished in two ways, separately or combined, depending on the application. light output of the led can be controlled either by linear change of its current, or by switching the current on and off while maintaining it cons tant. the second dimming method
bw9910/a high brightness led driver ?2012 bruckewell technology corp., ltd. 7 www.bruckewell - semi.com/ (so - called pwm dimming) controls the led brightness by varying the duty ratio of the output current. the linear dimming can be implemented by applying a control voltage from 0 to 250mv to the ld pin. this control vol tage overrides the internally set 250mv threshold level of the cs pin and programs the output current accordingly. for example, a potentiometer connected between v dd and ground can program the control voltage at the cs pin. applying a control voltage highe r than 250mv will not change the output current setting. when higher current is desired, select a smaller sensing resistor. the pwm dimming scheme can be implemented by applying an external pwm signal to the pwm_d pin. the pwm signal can be generated by a microcontroller or a pulse generator with a duty cycle proportional to the amount of desired light output. this signal enables and disables the converter modulating the led current in the pwm fashion. in this mode, led current can be in one of the two sta tes: zero or the nominal current set by the current sense resistor. it is not possible to use this method to achieve average brightness levels higher than the one set by the current sense threshold level of the bw9910 / bw9910 a. by using the pwm control meth od of the bw9910 / bw9910 a, the light output can be adjusted between zero a nd 100%. the accuracy of the pwm dimming method is limited only by the minimum gate pulse width, which is a fraction of a percentage of the low frequency duty cycle. pwm dimming of th e led light can be achieved by turning on and off the converter with low frequency 50hz to 1k hz ttl logic level signal. programming operating frequency the operating frequency of the oscillator is programmed between 25khz and 300khz using an external resi stor connected to the r osc pin . equation : (1) where f osc unit is khz. r osc unit is in k and shall be 820k ~ 1m for the case of v out < 7v because it has to satisfy the condition of t on > t blank . the efficiency can be improved as well. power factor correction when the input power to the led driver does not exceed 25w, a simple passive power factor correction circuit can be added to the bw9910 / bw9910 a typical application circuit in figure 2 in order to pass the ac line harmonic limits of the en61000 - 3 - 2 standard for class c equipment. the typical application circuit diagram shows how this can be done without affecting the rest of the circuit significantly. a simple circuit consisting of 3 diodes and 2 capacitors is added across the rectified ac line input to improve the line current harmonic distortion and to achieve a power factor greater tha n 0.85. inductor design the buck circuit is usually selected and it has two operation modes: continuous and discontinuous conduction modes. a buck power stage can be designed to operate in continuous mode for load current above a certain level usually 15% to 30% of full load. usually, the input voltage range, the output voltage and load current are defined by the power stage specification. this leaves the inductor value as the only design parameter to maintain continuous conduction mode. the minimum value of inductor to maintain continuous conduction mode can be determined by the following example. referring to the typical buck application circuit i n figure 5, the value can be calculated from the desired peak - to - peak led ripple current in the inductor. typ ically, such ripple current is selected to be 30% of the nominal led current. in the example given here, the nominal current i led is 350ma . the next step is to determin e the total voltage drop across the led string. for example, when the string consists of 10 high brightness leds and each diode has a forward voltage drop of 3. 3 v at its nominal current , i.e. the total led voltage drop v leds is 3 3 v. equation : (2) (3) (4) (5) where i led unit is ampere.
bw9910/a high brightness led driver ?2012 bruckewell technology corp., ltd. 8 www.bruckewell - semi.com/ assuming the nominal rectified input voltage v in 120v 1.41 4 169v, the switching duty ratio can be determined as follows : 0. 195 (6) then, in this example , given the switching frequency, f osc 50 k hz, the required on - time of the mosfet transistor can be calculated as below : 3.91 s (7) the require d minimum value of the inductor is given by : 5.06 mh (8) input bulk capacitor an input filter capacitor should be designed to hold the rectified ac voltage above twice the led string voltage throughout the ac line cycle. assuming 15% relative voltage ripple across the capacitor, a simplified formula for the minimum value of the bulk input capacitor is given by : equation : (9) w here d ch : c in capacity charge work period, generally about 0.2 0 ~ 0.2 5, f l : input frequency for full range (85 v rms ~ 265 v rms ) , ? v dc(max) should be set 10 % ~ 15 % of if the capacitor has a 15% voltage ripple then a simplified formula for the minimum value of the bulk input capacitor approximates to : (10) 2 4 f, a value 33 f/250v can be used . a passive pfc circuit at the input requires using two series connected capacitors at the place of calculated c min . each of these identical capacitors should be rated for ? of the input voltage and have twice as much c apacitance . enable function the bw9910 / bw9910 a can be turned off by pull ing the pwm_d pin to ground. when the device is disabled, the bw9910 / bw9910 a draws quiescent current of less than 1 .0 ma. output open circuit protection when the buck topology is used , and the led is connected in series with the inductor, there is no need for any protection against an open circuit condition in the led string. open led connection means no switching and can be continuous. in this case, since the output voltage will be th e same as input voltage, if there is a capacitor connected across the output, this capacitor should be able to withstand the peak value of the input voltage. thermal shut down thermal protection is added due to buck topology can generate large heat when o perated with high voltage input. the over temperature protection is activated to shut down external mosfet when the junction temperature (t j ) reaches 150 ? . there is a 50 ? hysteresis to re - start the mosfet. dc - dc low voltage applications boost led driver bw9910 / bw9910 a can also be used in boost configurations at reduced accuracy. the accuracy can be improved by mea suring the led current with an o p - a mp and use the o p a mps output to drive the ld pin. refer to figure 1, a b oost led driver is used when th e total voltage drop of the output led string is higher than the input supply voltage. for example, the b oost topology can be appropriate when input voltage is supplied by a 48v power supply and the led string consists of twenty hb leds, as the case may be for a street light.
bw9910/a high brightness led driver ?2012 bruckewell technology corp., ltd. 9 www.bruckewell - semi.com/ in a b oost converter, when the external mosfet is on the energy is stored in the inductor which is then delivered to the output when the external mosfet switches off. if the energ y stored in the inductor is not f ully depleted by the next switching cycle (continuous conduction mode) the dc conversion between input and output voltage is given by : ( 11 ) from the switching frequency, f osc , the on - time of the mosfet can be calculated : ( 12 ) from this the required inductor value can be determined by : ( 13 ) the b oost topology led driver requires an output capacitor to deliver current to the led string during the time that the external mosfet is on. in boost led driver topologies if the leds should become open circuit , damage may occur to the power switch and so some form of detection should be present to provide o ver - voltage detection/protection. figure 1 . dc - dc boost led driver buck - boost (fly - back) led driver refer figure 2, the buck - boost power conversion topology can be used when the forward voltage drop of the led string is higher, equal or lower than the input supply voltage. for example, the buck - boost topology can be appropriate whe n input voltage is supplied by 24v system bus for trucks (voltage at supply battery is between 18v and 32v) and output string consists of six to nine hb leds, as the case may be for tail and break signal lights. in the buck - boost converter, the energy fro m the input source is first stored in the inductor or fly - back transformer when the switching transistor is on. the energy is then delivered to the output during the off time of the transistor. when the energy stored in the fly - back inductor is not fully d epleted by the next switching cycle (continuous conduction mode) the dc conversion between input and output voltage is given by : ( 14 ) or d (15) the output voltage can be either higher or lower than the input voltage, depending on duty ratio. let us discuss the above example o f 24v battery system led driver that needs to drive six hb leds ( v f 3.3 v ) at 350ma. knowing the nominal input voltage v in 24v , the nominal duty ratio can be determined as below : d 0.45 then, given the switching frequency, in this example f osc 50khz, the required on - time of the mosfet transistor can be calculated : 9?
bw9910/a high brightness led driver ?2012 bruckewell technology corp., ltd. 10 www.bruckewell - semi.com/ the required minimum value of the inductor is given by : 2.05mh so, use 2.2mh output capacitor unlike the buck topology, the buck - boost convert er requires an output filter capacitor to deliver power to the led string during the on time of the mosf e t. in order to reduce the current ripple on the led, this capacitor must have impedance that is much lower than the dynamic impedance r out of the led string. if we assume r out 3 in our exa mple, in order to attenuate the switching ripple by a factor of 10, a capacitor with equivalent se ries resistance (esr) of 0 .3 is needed. a chip smt tantalum capacitor can be selected for this purpose . figure 2 . dc - dc buck - boost led driver ( b w9910 for 24v battery system) buck led driver the buck power conversion topology can be used when the led string voltage is needed to be lower than the input supply voltage. the design procedure for a buck led driver outlined in the previous section s can be applied to the low voltage led drivers as well. however, the designer must keep in mind that the input voltage must be maintained higher than 2 times the forward voltage drop across the leds. this limitation is related to the output current instabil ity that may develop when the bw9910/BW9910A buck converter operates at a duty cycle greater than 0.5. this instability reveals itself as an oscillation of the output current at a sub - harmonic of the switching frequency. benefiting from the bw9910 / bw991 0 a inherit ed high voltage f eature, rectified dc high voltage (v dc v ac 1.414) can be directly fed into power pin to achieve high duty cycle, which is only limited by v out / v in , to optimize design efficiency. t hi s solution can easily achieve above 90% efficiency. however , if the duty cycle is configured to reach above more than 50%, some instability called sub - harmonics oscillation ( sbo) will occur. the best solution is to adopt the so - called constant off - time op eration as shown in figure 4 and 6 . t o se t operating frequency , t he resistor (r osc ) is connected to ground by default . t his resistor can alternatively be connect ed to gate of mosfet to force the bw9910 / bw9910 a to enter constant off - time m ode which will dec rease duty cycle from 50% by increas e total period, t o n + t off . n o r mally , fixed f r equency design is chosen as shown in f igure 3 because it has better efficiency. for general led lighting application, pfc becomes a necessary f actor in order to meet the int ernational standard of solid state lighting. if passive valley - fill pfc is chosen, then the bw9910 / bw9910 a is bias ed right after passive pfc stage . t he dc voltage rail v in , is halved and it will easily create a more than 50% duty cycle for the same led loa ding due to v out / v in ratio is doubled. a sbo noise can be generated. in this case, t he constant off - time mode as shown in f igure 6 should be chosen. example : v in : v ac 110v with passive pfc v out : c onsist ing of 1w hb led with nominal v f 3. 3 v v in(min) : a fter rectified and passing pfc stage, the actual dc rail will become v in(min) 110v 1.414 / 2 77.7v dc the duty cycle, d v out / v in ( min ) , will reach above 50% when voltage drop of led string, as the v out is more than 77.7/2 38.8v. another word, if any string consisting of 38.8/3. 3 1 2 leds in a series, sbo will occur.
bw9910/a high brightness led driver ?2012 bruckewell technology corp., ltd. 11 www.bruckewell - semi.com/ in this case, the resistor ( r o s c ) should be connected between p in 8 , r osc , and p in 4, gate to set the bw9910 / bw9910 a operate in constant off - time mode to avoid sbo. figure 3. fixed frequency mode figure 4 . constant off - time mode figure 5 . typical a pplication circuit w ithout pfc in fixed frequency mode
bw9910/a high brightness led driver ?2012 bruckewell technology corp., ltd. 12 www.bruckewell - semi.com/ figure 6. typical application circuit with valley - fill pfc in constant off - time mode
bw9910/a high brightness led driver ?2012 bruckewell technology corp., ltd. 13 www.bruckewell - semi.com/ p ackage outline dimensions package type : sop - 8 / so8 - ep marking information sop - 8 so8 - ep sop - 8 so8 - ep x = a/t site , yy = year, ww = working week , z = device version bw9910 x yyww z bw9910 x yyww z bw9910 a x yyww z bw9910 a x yyww z
bw9910/a high brightness led driver ?2012 bruckewell technology corp., ltd. 14 www.bruckewell - semi.com/ legal disclaimer notice disclaimer all p oduct, p oduct specifications and data a e subject to change without notice to imp ove eliability, function o design o othe wise. bruckewell technology inc., its affiliates, agents, and employees, and all persons acting on its or their behalf (collectively, bruckewell), disclaim any and all liability for any errors, inaccuracies or incompleteness contained in any datasheet or in any other disclosure rel ating to any product. bruckewell makes no warranty, representation or guarantee regarding the suitability of the products for any particular purpose or the continuing production of any product. to the maximum extent permitted by applicable law, bruckewell disclaims (i) any and all liability arising out of the application or use of any product. (ii) any and all liability, including without limitation special, consequential or incidental damages. (iii) any and all implied warranties, including warranties of fitness for particular purpose, non - infringement and merchantability. statements regarding the suitability of products for certain types of applications are based on bruckewells knowledge of typical requirements that are often placed on bruckewell produc ts in generic applications. such statements are not binding statements about the suitability of products for a particular application. it is the customers responsibility to validate that a particular product with the properties described in the product s pecification is suitable for use in a particular application. parameters provided in datasheets and-or specifications may vary in different applications and performance may vary over time. product specifications do not expand or otherwise modify bruckewel ls terms and conditions of purchase, including but not limited to the warranty expressed therein.

▲Up To Search▲

Price & Availability of BW9910A

	To Download BW9910A Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .