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LD7515L 8/5 / 2015 1 leadtrend technology corporation www.leadtrend.com.tw LD7515L - d s - 0 0 a ugust 2015 primary side quasi - resonant bjt controller with cv/cc operation r ev . 0 0 general description the LD7515L is an excellent primary side feedback bjt controller with cv/cc operation, integrated with several functions of protections. it minimizes the compone nt counts and is available in a tiny sot - 26 package. those make it an ideal design for low cost applications. it provides functions of ultra - low startup current, green - mode power - saving operation and leading - edge blanking of the current sensing. also, the LD7515L features internal otp (over temperature protection) and ovp (over voltage protection) to prevent the circuit from being damaged due to abnormal conditions. in most cases, the power supply with primary - side feedback controller would accompany with s ome serious load regulation effect. to deal with this problem, the LD7515L consists of dedicated load regulation compensation circuit to enhance its performance. feature s ? primary - side feedback control w ith q uasi - resonant operation ? direct d rive o f bjt s witch ? constant voltage within ? 5% ? built - in adjustable load regulation compensation ? constant current control ? ultra - low startup current (<1. 9 ? a ) ? 0.5m a low operating current a t light load ? 60 k h z maximum switching frequency . ? current mode control ? green mode c ontrol improve efficiency ? leb ( leading - edge blanking ) o n cs pin ? built - in soft start ? vcc ovp ( over voltage protection ) ? fb pin open / short protection ? internal otp (over temperature protection) applications ? mobile phone adapter ? lower power ac/dc adapter typical application v c c a c i n p u t a c i n p u t e m i f i l t e r o u t c s c o m p l d 7 5 1 5 l g n d f b
LD7515L 8/5/2015 2 leadtrend technology corporation www.leadtrend.com.tw LD7515L - d s - 00 august 2015 pin configuration order ing information part number package t op mark shipping LD7515L gl sot - 26 ywp/ 1 5l 3000 / tape & reel the LD7515L is rohs compliant /green packaged pin descriptions pin name function 1 vcc supply voltage pin. 2 gnd ground. 3 fb auxiliary voltage sense and quasi resonant detection. 4 cs current sense pin, connect to sense the switch current. 5 comp output of the error amplifier for voltage compensati on. 6 out base drive output to drive the external bjt switch. sot - 26 (top view) yy, y : year code (d: 2004, e: 2005 ..) ww, w : week code pp : production code p 1 5l : ld75 1 5l 1 2 3 4 5 6 vcc gnd fb out comp cs y w p 1 5l pp
LD7515L 8/5/2015 3 leadtrend technology corporation www.leadtrend.com.tw LD7515L - d s - 00 august 2015 block diagram out internal bias & vref gnd 13 v 4 v vref ok pg 18 v vcc protection ovp uvlo comparator base driver ovp comparator vcc ok fb pwm comparator 2 r r r s q error amplifier load compensation max . frequency & green mode cs 1 v leading edge blanking internal otp 0 . 1 v / 0 . 2 v qrd gm 2 . 0 v sample and hold comp qrd blanking time time - out 1 c . c . fb buffer qrd v comp time - out 2 delay counter protection pg r s q q ovp 1 . 0 v s / h s / h uvp c . c . fb vcc cc control cs qrd
LD7515L 8/5/2015 4 leadtrend technology corporation www.leadtrend.com.tw LD7515L - d s - 00 august 2015 absolute maximum ratings supply voltage vcc, 2 0v out - 0.3 v ~3.3v comp, fb, cs - 0.3 v ~3.3v fb(ac current Q 3 ma - 0.7 v ~ 3.3v maximum junction temperature 150 ? c storage temperature range - 6 5 ? c to 1 50 ? c package thermal resistance (sot - 26, ja ) 200 ? c /w power dissipation (sot - 26, at ambient temperature = 85 ? c ) 200mw lead temperature (soldering, 10sec) 260 ? c esd voltage protection, human body model 2.5 kv esd voltage protection, machine model 250 v caution: stress exceeding maximum ratings may damage the device. maximum ratings are stress ratings only. functional operation above the recommended operating c onditions is not implied. extended exposure to stress above recommended operating conditions may affect device reliability recommended operating conditions item min. max. unit operating junction temperature - 40 1 1 0 ? c supply vcc voltage 5.5 16 v vcc c apacitor 2.2 10 ? f start - up resistor value (ac side, half wave) 1m 6.6 m ? comp pin capacitor 470 4700 p f note: 1. it s essential to connect vcc pin with a smd ceramic capacitor (0.1 ? f~0.47 ? f) to filter out the undesired switching noise for stable operatio n. this capacitor should be placed close to ic pin as possible 2. connecting a capacitor to comp pin is also essential to filter out the undesired switching noise for stable operation. 3. the small signal components should be placed close to ic pin as possible.
LD7515L 8/5/2015 5 leadtrend technology corporation www.leadtrend.com.tw LD7515L - d s - 00 august 2015 electrical characteristics (t a = +25 ? c unless otherwise stated, v cc =1 2 .0v) parameter conditions sym. min typ max units supply voltage (vcc pin) startup current vcc=uvlo - on - 0.05v i cc _ st 1.0 1.9 ? comp =0v, out=open, fb=2v i cc _ o p2 0.5 ma ovp/fb uvp tripped, fb=0v i cc _ opa 0.18 0.25 0.32 ma uvlo (off) v cc _ off 3.4 4.0 4.6 v uvlo (on) v cc _ on 12 13 14 v vcc ovp level v cc _ ovp 17 18 19 v error amplifier (comp pin) reference voltage, v ref v ref 1.97 2. 00 2. 03 v output sink current v fb = v ref +0.05 , v comp =2v* i comp _ sink1 - 4 ? fb = vref - 0.05 v , v comp =2v* i comp _ source1 4 ? fb =1 .0 v * v comp _ clamp 3 v load compensation current v comp = 3 v i l oad c omp 1 7 20 23 ? current sens ing (cs pin) maximum input voltage v cs _ max 0.93 1 1.07 v minimum v cs - off v comp < 0.45v * v cs _ min 15 0 1 7 5 195 m v leading edge blanking time * t leb 430 6 0 0 770 ns oscillator for switching frequency maximum frequency f sw _ max 54.5 60 65.5 khz green mod e frequency * f sw _ green 25 khz minimum frequency f sw _ min 0.6 0.8 1. 0 khz maximum on time t on _ max 11 16 21 ? output drive (out pin) max. output base current vcs=1v i b _ max 54 62 69 ma fb under voltage protection (uvp, fb pin) under voltage level v fb _ uvp 0.9 1.0 1.1 v uvp delay time at start - up* t d _ fbuvp _ ss 20 ms on chip otp (over temperature) otp level * * t inotp 115 13 0 145 ? inotp _ hys 3 0 ? * : guaranteed by design. * * : for reference only, parameter verified in design p hase .
LD7515L 8/5/2015 6 leadtrend technology corporation www.leadtrend.com.tw LD7515L - d s - 00 august 2015 typical performance characteristics v cc - on (v) fig. 1 uvlo (on) vs. temperature temperature ( ? c) 1 0 .0 1 1 . 0 1 2.0 13. 0 1 4.0 1 5 .0 - 40 0 40 80 120 125 v cc - off (v) temperature ( ? c) fig. 2 uvlo ( o ff ) vs. temperature 1 . 0 3 .0 4.0 6.0 2 . 0 - 40 0 40 80 120 125 5.0 i cc - st ( ? a ) temperature ( ? c) fig. 3 start up current vs. temperature 0 . 5 1 . 0 2 . 0 0 . 0 - 40 0 40 80 120 125 1 . 5 f sw - max (khz) fig. 4 max frequency v s. temperature temperature ( ? c) - 40 45 50 55 60 65 70 0 40 80 120 125 f sw - green (khz) temperature ( ? c) fig. 5 green mode frequency vs. temperature 1 9 21 2 3 2 5 2 7 2 9 - 40 0 40 80 120 125 f sw - min (khz) temperature ( ? c) fig. 6 min frequency vs. temperature 0 . 5 0 . 6 0 . 7 0 . 8 0 . 9 1 . 0 - 40 0 40 80 120 125
LD7515L 8/5/2015 7 leadtrend technology corporation www.leadtrend.com.tw LD7515L - d s - 00 august 2015 v ref (v) temperature ( ? c) fig. 7 reference voltage vs. temperature - 40 0 40 80 120 125 1.9 8 1.99 2.00 2.0 1 2.0 2 1.9 7 -40 -20 0 20 40 60 80 100 120 0 3 6 9 12 15 18 y axis title x axis title -40 -20 0 20 40 60 80 100 120 0 3 6 9 12 15 18 y axis title x axis title i load c omp ( ? a) temperature ( ? c) fig. 8 load compensation vs. temperature - 40 0 40 80 120 12 5 5 10 15 20 25 0 30 v cs - max (v) temperature ( ? c) fig. 9 v cs ( off ) vs. temperature 0. 94 0. 96 0. 98 1.00 1.02 1.04 - 40 0 40 80 120 125 v cc - ovp (v) temperature ( ? c) fig. 10 vcc ovp vs. temperature 1 5 1 6 17 18 19 20 - 40 0 40 80 120 125 r out - l ( ? ) temperature ( ? c) fig. 1 1 output low on - resistance vs. temperature - 40 0 40 80 120 125 0 .5 1 . 5 2 .5 3 . 5 4 . 5 i b - max ( ma ) temperature ( ? c) fig. 1 2 max. output base current vs. temperature - 40 0 40 80 120 125 3 0 4 0 5 0 6 0 7 0 8 0
LD7515L 8/5/2015 8 leadtrend technology corporation www.leadtrend.com.tw LD7515L - d s - 00 august 2015 application information operation overview the LD7515L is an excellent primary side feedback controller with quasi - resonant operat ion to provide high efficiency. the LD7515L removes the need for secondary feedback circuits while achieving excellent line and load regulation. i t meets the green - power requirement and is intended for the use in those modern switching power suppliers and linear adaptors that demand higher power efficiency and power - saving. it integrates with more functions to reduce the external components counts and the size. m ajor features are described as below. under voltage lockout (uvlo) an uvlo comparator is impleme nted in it to detect the voltage across vcc pin. it would assure the supply voltage enough to turn on the LD7515L and further to drive the power bjt. as shown in fig. 13, a hysteresis is built in to prevent shutdown from voltage dip during startup. fig. 13 startup current and startup circuit t he typical startup circuit to generate vcc of the LD7515L is shown in fig. 14. at startup transient , the vcc i s below the uvlo (on) threshold, so there s no pulse deliver ed out from l d7515l to drive the power bjt. therefore, the current through r1 will be used to charge the capacitor c1. until the vcc is fully charged to deliver the drive - out signal, the auxiliary winding of the transformer will provide supply current . lower startup c urrent requirement on the pwm controller will help to increase the value of r1 and then reduce the power consumption on r1. by using cmos process and some unique circuit design, the LD7515L requires only 1.9 ? a max to start up. higher resistance of r1 will spend much more time to start up. t he user is recommended to select proper value of r1 and c1 to optimize the power consumption and startup time. fig. 14 vcc uvlo(on) uvlo(off) t t i(vcc) startup current (~ua) operating current (~ ma) e m i f i l t e r r 1 o u t c s v c c g n d l d 7 5 1 5 l a c i n p u t c 1 c b u l k d 1
LD7515L 8/5/2015 9 leadtrend technology corporation www.leadtrend.com.tw LD7515L - d s - 00 august 2015 principle of cv operation in the dcm flyback converter, it can sen se the output voltage from auxiliary winding. LD7515L s amples the auxiliary winding on the primary - side to regulate the output voltage, as shown in the fig. 15 . the voltage induced in the auxiliary winding is a reflection of the secondary winding voltage w hile the bjt is in off state. via a resistor divider connected between the auxiliary winding and fb pin, the auxiliary voltage is sampled after the sample delay time which is defined as 30~50% of secondary current discharge time from previous cycle . a nd wi ll be hold until the next sampling period . the sampled voltage is compared with an internal reference v ref (2. 0 v) and the error will be amplified. the error amplifier output comp reflects the load condition and controls the duty cycle to regulate the outpu t voltage, thus constant output voltage can be achieved. the output voltage is given as: where v f indicates the drop voltage of the output d iode , ra and rb are top and bottom feedback resistor value, ns and na are the turns of tran sformer secondary and auxiliary . in case that the output voltage is sensed through the auxiliary winding; the leakage inductance will induce ringing to affect output regulation. to optimize the collector voltage clamp circuit will minimize the high frequen cy ringing and achieve the best regulation. fig . 16 shows the desired collector voltage waveform in compare to those with large undershoot due to leakage inductance induced ring (fig. 17) . th e ringing may make the sample error and cause poor performance fo r output voltage regulation. a proper selection for resistor rs, in series with the clamp diode, may reduce any large undershoot, as shown in fig. 1 8 . fig. 15 fig.16 fig.17 fig.18 f out v ) na ns )( rb ra 1 ( v 0 . 2 v ? ? ? o u t c s c o m p f b n a n s n p r a r b v i n s / h v r e f + - d r i v e r l d 7 5 1 5 l v c e t h e o v e r s h o o t h e r e i s m i n o r v c e t h e u n d e r s h o o t w o u l d m a k e t h e s a m p l e e r r o r . o u t c s c o m p f b n a n s n p r a r b v i n l d 7 5 1 5 l r s
LD7515L 8/5/2015 10 leadtrend technology corporation www.leadtrend.com.tw LD7515L - d s - 00 august 2015 load regulation compensation LD7515L is implement ed with load regulation compensation to compensate the cable voltage drop and to achieve a better voltage regulation . the offset voltage across fb is produced by t he internal sink current source during the sampling period . the internal sink current source is proportional to the value of v comp to compensate the cable loss as shown in fig. 19. so, the offset voltage will decrease as the v comp decreases from full - load to no - load. it is programmable by adjusting the resistance of the voltage divider to compensate the drop for cable lines used in various conditions . the equat ion of internal sink current is shown as: the compe n sation current versus v comp is shown as: fig. 19 q uasi - r esonant mode detection the LD7515L employs quasi - re sonant (qr) switching scheme to switch in valley - mode either in cv or cc operation. this will greatly reduce the switching loss and the ra tio dv/dt in the entire operating range for the power supply. fig. 20 shows the typical qr detection block . the qr detection block will detect auxiliary winding signal to drive bjt as fb pin voltage drops to 0. 1 v. the qr comparator will not activate if fb pin voltage remains above 0. 2 v. fig. 20 multi - mode operation t he LD7515L is a qr controller operating in multi - mode s . the controller changes operation mode s according to line voltage and load conditions. at heavy - load (v co mp >1. 8 v, fig . 21 ), there might be two situations to meet. if the system ac input is in low line, the LD7515L will turn on in first valley. if in high line, the switching frequency will increase till over the limit of 60 khz and skip the first valley to tur n on in 2 nd , 3 rd .valley. the switching frequency would var y depending on the line voltage and the load conditions when the system is operated in qr mode . at mediu m or light load conditions (0 . 7 vLD7515L will turn on in 4 th , 5 th . valley. that is, when the load decreases, the system will automatically skip some valleys and the switching frequency is therefore reduced. a smooth frequency fold - back and high power efficiency are then achieved. at zero load or very light load conditions (v comp < 0. 3 v ), the system operates in minimum frequency for power saving . t he system modulates the frequency accordi ng to the load and v comp conditions. a) ( 85 . 7 0.45) (v i comp fb ? ? ? ? v c o m p ( v ) 0 3 . 0 0 . 4 5 2 0 i f b ( ? a ) fb pwm 2 r r r s q error amplifier load compensation max . frequency & green mode cs 1 v leading edge blanking 0 . 1 / 0 . 2 v qrd gm 2 . 0 v sample and hold qrd blanking time time - out 1 buffer qrd v comp time - out 2 s / h c . c . fb turn - on turn - off ra rb n aux
LD7515L 8/5/2015 11 leadtrend technology corporation www.leadtrend.com.tw LD7515L - d s - 00 august 2015 fig. 21 current sensing and leading - edge blanking the typical current mode of pwm controller feedbacks both current signal and voltage signal to close the control loop and achieve regula tion. as shown in fig. 22, the LD7515L detects the primary bjt current from the cs pin, which is not only for the peak current mode control but also for the pulse - by - pulse current limit. the maximum voltage threshold of the current sensing pin is set at 1v . from above, the bjt peak current can be obtained from below. a leading - edge blanking (leb) time is included in the input of cs pin to prevent the false - trigger from the turn - on current spike. fig. 22 principle of c.c. operation t he p rimary side control scheme is applied to eliminate secondary feedback circuit or o p to - coupler, which will reduce the system cost. the switching waveforms are shown in fig. 23 . t he output current i o can be expressed as: the primary peak current ( i p , p k ) , inductor current discharge time (t dis ) and switching period (t s ) can be detected by the ic . t he ratio of v cs* t dis /t s will be modulate d as a constant (v cs* t dis /t s =1/3). so that i o can be obtained as however this is an approximat e equation. the user may fine - tune it according to the experiment result. fig. 23 q u a s i r e s o n a n t ( f i r s t v a l l e y ) d i s c o n t i n u o u s w i t h v a l l e y s w i t c h i n g ( 2 n d , 3 r d , 4 t h . . . v a l l e y ) 2 5 k h z 0 . 8 k h z 6 0 k h z v c o m p f s g r e e n m o d e 1 . 4 v 0 . 7 v 0 . 3 v 1 . 8 v cs peak(max) r 1v i ? o u t c s c o m p f b n a n s n p r a r b v i n l d 7 5 1 5 l r s l e b t i m e r c s s dis cs cs s p dis pk p, s p s dis pk s, t t r v n n 2 1 ts t i n n 2 1 t t i 2 1 io ? ? ? ? ? ? ? ? 3 1 r 1 n n 2 1 t t r v n n 2 1 io s s p s dis s cs s p ? ? ? ? ? ? o u t i p i s i p , p k i s , p k t o n t d i s t s
LD7515L 8/5/2015 12 leadtrend technology corporation www.leadtrend.com.tw LD7515L - d s - 00 august 2015 ovp (over voltage protection) on vcc C auto recovery LD7515L is implemented with ovp fun ction through vcc. as the vcc voltage rises over the ovp threshold voltage, the output drive circuit will be shut off simultaneously thus to stop the switching of the power bjt until the next uvlo(on) arrives. the vcc ovp function of LD7515L is an auto - re covery type protection. t he fig. 24 shows its operation. that is, if the ovp condition is removed, it will resume to normal output voltage and v cc level in normal condition. fig. 24 fb un der voltage protection (fb uvp) & fb short circuit protection C auto recovery LD7515L is implemented with an uvp function over fb pin. if the fb voltage falls below 1.0 v over the delay time, the protection will be activated to stop the switching of the power bjt until the next uvlo(on) arriv es. the fb uvp function in LD7515L is an auto - recovery type protection. t he fig. 25 shows its operation. the fb uvp is disabled during the soft start period . during the soft start period, the fb uvp is disabled. to avoid output over voltage in soft start p eriod. the fig. 26 shows the opera tion. while fb is short to gnd, fb pin keeps in zero voltage level. if fb cannot detect any voltage signal over 0.2v in the beginning of soft start period, then the soft start will turn to generate a driving signal every 4 ms until fb uvp d elay to shut down ic and auto recovery . fig. 25 fig. 26 v c c u v l o ( o n ) u v l o ( o f f ) t o v p t r i p p e d t o u t s w i t c h i n g s w i t c h i n g n o n - s w i t c h i n g o v p l e v e l f b u v p l e v e l t f b u v p t r i p p e d t o u t s w i t c h i n g s w i t c h i n g n o n - s w i t c h i n g v c c t f b u v p d e l a y t i m e u v l o ( o n ) u v l o ( o f f ) s o f t s t a r t + f b u v p d e l a y t i m e f b f b s h o r t l e v e l t f b s h o r t t c s n o n - s w i t c h i n g v c c t u v l o ( o n ) u v l o ( o f f ) s o f t s t a r t + f b u v p d e l a y t i m e o u t t
LD7515L 8/5/2015 13 leadtrend technology corporation www.leadtrend.com.tw LD7515L - d s - 00 august 2015 package information sot - 26 symbol dimension in millimeters dimensions in inches min max min max a 2.692 3.099 0.10 6 0.122 b 1.397 1.803 0.055 0.071 c ------- 1.450 ------- 0.057 d 0.300 0.5 00 0.012 0.020 f 0.95 typ 0.037 typ h 0.080 0.254 0.003 0.010 i 0.050 0.150 0.002 0.006 j 2.600 3.000 0.102 0.118 m 0.300 0.600 0.012 0.024 0 10 0 10 i mportant not ice leadtrend technology corp. reserves the right to make changes or corrections to its products at any time without notice. cust omers should verify the datasheets are current and complete before placing order.
LD7515L 8/5/2015 14 leadtrend technology corporation www.leadtrend.com.tw LD7515L - d s - 00 august 2015 r e vision history rev . d a te change notice 00 0 8 / 0 5 / 2015 original specification .

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