unisonic technologies co., ltd US4651S linear integrated circuit www.unisonic.com.tw 1 of 9 copyright ? 2015 unisonic technologies co., ltd qw-r129-003.b low cost power-saving mode power-switch for flyback converters ? description the utc US4651S is a high performance current mode power-switch ideally suited for low standby power. drain start up make the power reliable on startup design and lower standby power. at no load condition, the ic operates in power-saving mode for lower standby power, decreasing frequency for higher conversion efficiency at light load condition. the utc US4651S contains protection with automatic recovery including olp (over load protection), otp (over temperature protection), ovp (over voltage protection), uvlo (v dd over voltage sop-8 clamp and under voltage lockout).to prot ect the power mosfet, gate-drive outpu t is fixed up to 16v max. the utc US4651S contains protection ocp (cycle-by-cycle current limiting). the internal slope compensation improves system st ability at high pwm duty cycle output. leading-edge blanking on current sense input removes the signal glitch, which offering minimal external component count in the design. excellent emi performance is achieved with utc proprietary frequency hopping technique (zl201020615247.1) together with soft driver control. audi o noise is eliminated due to switch frequency more than 20khz during operation. the utc US4651S has such applications as: battery charger, power adaptor, set-top box power supplies, ink jet printers, open-frame smps. ? features * utc proprietary frequency hopping technology for improved emi performance. * power-saving mode for high light-load and standby efficiency * soft start * dynamic peak current limitin g for constant output power * built-in synchronized slope compensation * olp,ovp,otp and v dd clamp for higher security * drain start up for lower standby power * fixed switch frequency 65khz * gate output voltage clamped at 15v * low start-up current * cycle-by-cycle current limiting * under voltage lockout (uvlo) * few external components required ? ordering information ordering number package packing US4651Sg-s08-r sop-8 tape reel US4651Sg-s08-r (1)packing type (2)package type (3)green package (1) r: tape reel (2) s08: sop-8 (3) g: halogen free and lead free
US4651S linear integrated circuit unisonic technologies co., ltd 2 of 9 www.unisonic.com.tw qw-r129-003.b ? marking ? pin configuration gnd fb nc drain v dd nc cs 1 2 3 4 8 7 6 5 nc ? pin description pin no. pin name pin type description 1 v dd p power supply. 2 gnd p ground. 3, 5, 7 nc no connection 4 cs i current sense input pin. connected to mosfet current sensing resistor node. 6 drain o connected the primary lead of the transformer. 8 fb i feedback input pin. the pwm duty cycle is determined by voltage level into this pin and cs pin input. ? block diagram drain fb pwm comp ocp uvlo reference voltage burstmode v dd gnd latch s r q q cs driver leb slope compensation constant power limit otp logic control ovp 8 1 6 4 3/5/7 2 oscillator frequency hopping nc uvlo m1 m2
US4651S linear integrated circuit unisonic technologies co., ltd 3 of 9 www.unisonic.com.tw qw-r129-003.b ? absolute maximum ratings (t a =25c, v dd =15v, unless otherwise specified) parameter symbol ratings unit drain voltage v drain -0.3~600 v supply voltage v dd 30 v input voltage to fb pin v fb -0.3 ~ 7 v input voltage to cs pin v cs -0.3 ~ 7 v junction temperature t j +150 ? c operating temperature t opr -40 ~ +125 c storage temperature t stg -50 ~ +150 ? c note: absolute maximum ratings are those values beyond which the device could be permanently damaged. absolute maximum ratings are stress ratings only and functional device oper ation is not implied. ? operating range parameter symbol ratings unit supply voltage v dd 9~ 24 v ? electrical characteristics (t a =25c, v dd =15v unless otherwise specified) parameter symbol test conditions min typ max unit supply section start up current i str v dd = v dd(on) -0.5v 2.5 20 a ic operating current i op v fb =3.5v 3 5 ma v dd zener clamp current i clamp i vdd =20ma 31 33 35 v under-voltage lockout section start threshold voltage v thd(on) 12 13 14 v min. operating voltage v dd(min) 6 7 8 v control section v fb open loop voltage level v fb-open 5.4 v pwm input gain a vcs ? v fb / ? v cs 3 v/v burst-mode out fb voltage v fb(out) v cs =0 1.8 v reduce-frequency end fb voltage v fb(end) v cs =0 2.9 v burst-mode enter fb voltage v fb(in) v cs =0 1.5 v normal v fb =3.5v 60 65 70 khz switch frequency power-saving f sw before enter burst mode 19 22 25 khz duty cycle d max v fb =3.5v, v cs =0 70 78 85 % frequency hopping f j(sw) 4 % frequency vdd stability f dv v dd =12v~20v 5 % frequency temperature stability f dt t=-20~85c 5 % feedback short current i fb 280 ua protection section v cc over voltage protection threshold v ovp v fb =3.5v 25 27 29 v fb pin over load protection threshold v olp 4.2 v over temperature protection t (thr) 135 ? c over load protection delay-time t delay 90 ms soft start time t ss 3 ms current limiting section peak current flat threshold voltage v cs-f v fb =3.5v, duty 60% 0.85 0.95 1.05 v peak current valley threshold voltage v cs-v v fb =3.5v, duty=0% 0.55 0.65 0.75 v lead edge blanking time t leb 540 ns mosfet section drain-source breakdown voltage v bvdss 600 v static drain to source on resistor r ds(on) 12 ?
US4651S linear integrated circuit unisonic technologies co., ltd 4 of 9 www.unisonic.com.tw qw-r129-003.b ? operation description the utc US4651S devices integrate many useful designs into one controller for low-power switch-mode power supplies. the following descriptions highlig ht some of the f eatures of the utc US4651S series. drain hv-start up the utc US4651S achieves lower standby power through drain hv-start up . power-saving mode operation the proprietary power-saving mode function provides linearly decreasing the switching frequency under light-load conditions for higher efficiency. the feedback volt age, which is sampled from the voltage feedback loop, is taken as the reference. once the feedback voltage dropped below the thresh old voltage, the switching frequency starts to decrease. this power-savin g mode function dramatically reduce s power consumption under light-load conditions. the 22khz minimum frequency control also elim inates the audio noise at any loading conditions. at zero load condition, the magnitude of power loss is in proportion to the number of switching events within a fixed period of time. reducing switching events leads to the reduction on the power loss and thus conserves the energy. the US4651S enter burst mode at st andby condition to minimize the switching loss and reduces the standby power consumption. power supplies using the utc US4651S can easily meet even t he strictest regulations regarding standby power consumption. switch frequency set the maximum switch frequency is fixed to 65khz. switch frequency is modulated by output power p out during ic operating. at no load or light load cond ition, most of the power dissipation in a switching mode power supply is from switching loss on the mosfet transistor, the core loss of the transformer and the loss on the snubber circuit. the magnitude of power loss is in proportion to the number of sw itching events within a fixed period of time. so lower switch frequency at lower load, which more and more improve ic?s efficiency at light load. at from no load to light load condition, the ic will operate at from burst m ode to reducing frequency mode. the relation curve between f sw and p out /p out (max) as followed fig.1. fig.1 the relation curve between f sw and relative output power p out / p out (max)
US4651S linear integrated circuit unisonic technologies co., ltd 5 of 9 www.unisonic.com.tw qw-r129-003.b ? operation description (cont.) frequency hopping for emi improvement the frequency hopping is implemented in the ic; there are two oscillators built-in the ic. the first oscillator is to set the normal switching frequency; the switching frequency is modulated with a period signal generated by the 2nd oscillator. the relation between the first oscillator and th e 2nd oscillator as followed fig.2. so the tone energy is evenly spread out, the spread spectrum minimizes the conduction band emi and therefor e eases the system design in meeting stringent emi requirement. fig.2 frequency hopping built-in slope compensation built-in slope compensation circuit greatly improv es the close loop stabilit y at ccm and prevents the sub-harmonic oscillation. leading-edge blanking each time the power mosfet is switched on, a turn-on sp ike will inevitably occur at t he sense-resistor. to avoid premature termination of the switching pulse, a 400ns leading-edge blanking time is built in. conventional rc filtering can therefore be omitted. during this blanking period, the curr ent-limit comparator is disabled and it cannot switch off the gate driver. constant output power limit when the cs voltage, ac ross the cs resistor r s , reaches the threshold voltag e, around 0.8v, t he output gate drive will be turned off after a small propagation delay t d . this propagation delay will introduce an additional current proportional to t d v in /lp. since the propagation dela y is nearly constant regardle ss of the input line voltage v in . higher input line voltage will result in a larger additional cu rrent and hence the output power lim it is also higher than that under low input line voltage. to co mpensate this variation for wide ac in put range, the threshold voltage is adjusted by the v in current. since v in pin is connected to the rectified i nput line voltage through a resistor r vin , a higher line voltage will generate higher v in current into the v in pin. the threshold volt age is decreased if the v in current is increased. smaller threshold voltage, forces the output gate drive to termi nate earlier, thus reduce the total pwm turn-on time and make the output power equal to that of low line input. this proprietary internal compensation ensures a constant output power limit for wide ac input voltage from 90vac to 264vac. under voltage lockout (uvlo) the turn-on and turn-off thresholds of the utc US4651S are fixed internally at v thd(on) /v dd(min) during start-up, the hold-up capacitor must be charged to v thd(on) through the start-up resi stor, so that the utc US4651S will be enabled. the hold-up capacitor will continue to supply v dd until power can be delivered from the auxiliary winding of the main transformer. v dd must not drop below v dd(min) during this start-up process. this uvlo hysteresis window ensures that hold-up capacitor will be adequate to supply v dd during start-up. gate output the utc US4651S output stage is a fast totem pole gate driver. cross conduction has been avoided to minimize heat dissipation, increase efficiency, and enhance reliability. a good tradeoff is ac hieved through dead time control. the low idle loss and good emi system design is easier to ac hieve with this dedicated control scheme. an internal 15v clamp is added for mosfet gate protection at higher than expected v dd input.
US4651S linear integrated circuit unisonic technologies co., ltd 6 of 9 www.unisonic.com.tw qw-r129-003.b ? operation description (cont.) protection controls the ic takes on more protection functions such as ovp, olp and otp etc. in case of those failure modes for continual blanking time, the driver is shut down . driver is reset after failure is eliminated. ovp the ovp will shut down the switchin g of the power mosfet whenever v dd >v ovp . the ovp event as followed fig.3. fig.3 ovp case fig.4 olp case olp olp will shut down driver when v fb > v olp for continual a blanking time. the olp event as followed fig.4. otp otp will shut down driver when ic temperature >t (thr) . pcb layout note noise from the current sense or the control signal can cause significant pulse width jitter in continuous-conduction mode, and slope compensation helps alleviate these problems. good placement and layout practices should be followed. avoiding long pcb traces and component leads, locating compensation and filter components near the utc US4651S , and increasing the power mos gate resistance is advised.
US4651S linear integrated circuit unisonic technologies co., ltd 7 of 9 www.unisonic.com.tw qw-r129-003.b ? refrence circuit 12w (5v/2.4a) fb v dd drain u1 8 2 1 r20 r21 r22 r13 + c7 c10 l n f1 3 12 4 lf1 3 12 4 lf2 cx1 r1 r2 4 bd1 3 2 1 r7 r10 c1 c2 + c3 d1 d3 5 6 4 9 1 3 4 u3 2 r41 r42 3 u4 c45 c46 r43 r45 r46 r47 v out + v out gnd t1 r40 c40 d5 a l1 + c41 + c43 c42 cy1 b r11 r8 4 cs c6 + zd1 gnd 6 bom reference component reference component bd1 2a_600v lf1, lf2 choke c1 cc 10nf/1kv r7, r8 r 47k ? c2 elc 22uf/400v 105c, 20% r13 r 4.7 ? c3 cc 1000pf/1kv r15 r 10 ? c6 cc 1nf/50v r16 r 47 ? c10 elc 10uf/50v 105c, 20% r18 r 1k ? c7, c46 cc 0.1uf/50v r20, r21 r 1.5 ? c41, c43 elc 680uf/25v, 105 , 20% r22 r 2.7 ? c45 cc 10nf/50v r46 r 10k ? d4 1n4148, 0.15a/75v r41 r 820 ? d1 1n4007, 1.0a/1000v r42 r 2.2k ? d3 bav20w ,1a/200v r43 r 680 ? d5 schottky 10a/100v r45 r 68k ? cx1 x-cap 0.11uf/275vac r46 r 10k ? cy1 y-cap 1000pf/400v u1 ic US4651S f1 fuse, 1.0a / 250v u3 ltv-431 t1 ee-16 u4 tl431
US4651S linear integrated circuit unisonic technologies co., ltd 8 of 9 www.unisonic.com.tw qw-r129-003.b ? typical characteristics v thd(on) (v) v dd(min) (v) i str (a) f sw (khz) f sw-power-saving (khz) d max (%)
US4651S linear integrated circuit unisonic technologies co., ltd 9 of 9 www.unisonic.com.tw qw-r129-003.b utc assumes no responsibility for equipment failures that result from using products at values that exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or other parameters) listed in products specifications of any and all utc products described or contained herein. utc products are not designed for use in life support appliances, devices or systems where malfunction of these products can be reasonably expected to result in personal injury. reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. the information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changed without notice.
|
