unisonic technologies co., ltd uc3863a linear integrated circuit www.unisonic.com.tw 1 of 10 copyright ? 2017 unisonic technologies co., ltd qw-r103-148.b low cost power-saving mode pwm controller for flyback converters ? description the uc3863a is a high performance current mode pwm controller ideally suited for lo w standby power. the pwm switching frequency is programmable externally at normal operation. low v dd startup current make the powe r reliable on startup design and a large value resistor could be used in the startup circuit to minimize the 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 uc3863a contains protection with automatic recovery including olp (over load protection), ocp (cycle-by-cycle current limiting), and uvlo (v dd over voltage clamp and under voltage lockout). it also provides the protections including otp (over temperature protection), ovp (over voltage protection) with automatic recovery. to protect the power mosfet, gate-drive output is fixed up to 16v max. the internal slope compensation improves system stability 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. audio noise is eliminated due to switch frequency more than 20khz during operation. the uc3863a 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 * dynamic peak current limitin g for constant output power * built-in synchronized slope compensation * olp with automatic recovery * otp and ovp with automatic recovery * v dd clamp for higher security * programmable pwm frequency * gate output voltage clamped at 16v * low start-up current * cycle-by-cycle current limiting * under voltage lockout (uvlo) * few external components required
uc3863a linear integrated circuit unisonic technologies co., ltd 2 of 10 www.unisonic.com.tw qw-r103-148.b ? ordering information ordering number lead free halogen free package packing UC3863AL-AG6-R uc3863ag-ag6-r sot-26 tape reel uc3863al-s08-r uc3863ag-s08-r sop-8 tape reel uc3863al-sh2-r uc3863ag-sh2-r hsop-8 tape reel ? marking sot-26 sop-8 / hsop-8
uc3863a linear integrated circuit unisonic technologies co., ltd 3 of 10 www.unisonic.com.tw qw-r103-148.b ? pin configuration ? pin description pin no. sot-26 sop-8 hsop-8 pin name pin type description 1 8 gnd p ground 2 7 fb i feedback input pin. the pwm duty cycle is determined by voltage level into this pin and sense pin input 3 5 ri i a resistor connected between ri and gnd sets switching frequency. a 100k ? resistor r i results in a 65khz switching frequency 4 4 sense i current sense input pin. co nnected to mosfet current sensing resistor node 5 2 v dd p power supply. 6 1 gate o the totem-pole output driver for driving the power mosfet - 3, 6 nc - no connection ? block diagram gate fb pwm comp ocp uvlo reference voltage burstmode oscillator v dd gnd latch s r q q sense driver leb frequency hopping slope compensation constant power limit otp logic control ovp 1/8 2/7 5/2 6/1 4/4 3/5 ri
uc3863a linear integrated circuit unisonic technologies co., ltd 4 of 10 www.unisonic.com.tw qw-r103-148.b ? absolute maximum ratings (t a =25c, v dd =15v, unless otherwise specified) parameter symbol ratings unit supply voltage v dd 35 v input voltage to fb pin v fb -0.3 ~ 7 v input voltage to cs pin v sense -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 10 ~ 24 v ? electrical characteristics (t a =25c, v dd =15v, r i =100k ? 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 15 a ic operating current i op v fb =3.5v 0.8 1.8 ma v cc zener clamp voltage v cc(clamp) i vcc =20ma 31 33 35 v under-voltage lockout section start threshold voltage v thd(on) 16.5 18 20 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 sense =0 1.5 v burst-mode enter fb voltage v fb(in) v sense =0 1.35 v normal v fb =3.5v, ri=100k ? 60 65 70 khz switch frequency power-saving f sw before enter burst mode 20 khz duty cycle d max v fb =3.5v, v sense =0 70 78 90 % frequency hopping f j(sw) -9 +9 % frequency vdd stability f dv v dd =12v ~ 20v 10 % frequency temperature stability f dt t=-40 ~ 110c 10 % feedback short current i fb 240 ua softstart time tss 5 ms protection section vcc over voltage protection threshold v ovp v fb =3.9v 25 27 29 v fb pin over load protection threshold v olp 4.2 v over load protection delay-time t delay 60 88 120 ms otp threshold t (thr) v fb =3.9v 150 c current limiting section peak current valley threshold voltage v cs-f v fb =3.9v, duty 60% 0.92 v peak current valley threshold voltage v cs-v v fb =4.0v, duty=0% 0.60 0.65 0.70 v lead edge blanking time t leb 200 350 550 ns driver output section output voltage low state v ol v dd =16, i o =-20ma 1 v output voltage high state v oh v dd =16, i o = 20ma 11 v output voltage rise time t r c l =1.0nf 150 ns output voltage fall time t f c l =1.0nf 60 ns
uc3863a linear integrated circuit unisonic technologies co., ltd 5 of 10 www.unisonic.com.tw qw-r103-148.b ? operation description the uc3863a devices integrate many useful designs into one controller for low-power switch-mode power supplies. the following descriptions high light some of the features of the uc3863a series. start-up current the start-up current is only 5 a. low start-up current allows a start- up resistor with a high resistance and a low-wattage to supply the start-up power for the controller. for ac/dc adaptor with universal input range design, a 2.5~3m ? , 1/8w startup resistor c ould be used together with a v dd capacitor to provide a fa st startup and low power dissipation solution. 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 uc3863a enter burst mode at standby condition to mi nimize the switching loss and reduces the standby power consumption. power supplies using the uc3863a can easily meet even t he strictest regulations regarding standby power consumption. switch frequency set the maximum switch frequency is set through the 100k ? ri-pin resistor to 65khz. switch frequency is modulated by output power p out during ic operating. at no load or light load condition, mo st 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 switching 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 mode to reducing frequency mode. the relation curve between f sw and p out /p out (max) as followed fig.1. the maximum switch frequency is set through the ri-pin resistor ri: f sw =6500/ri (k ? ) khz. fig.1 the relation curve between f sw and relative output power p out / p out (max)
uc3863a linear integrated circuit unisonic technologies co., ltd 6 of 10 www.unisonic.com.tw qw-r103-148.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 sense voltage, acro ss the sense resistor r s , reaches the threshold voltage, around v cs-v , the 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 delay is nearly co nstant regardless of the input line voltage v in . higher input line voltage will result in a larger additional current and hence the output power limit is also higher than that under low input line vo ltage. to compensate this variation for wi de ac input 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 uc3863a 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 resistor, so that the uc3863a 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 uc3863a output stage is a fast totem pol e gate driver. cross conduction has been avoided to minimize heat dissipation, increase efficiency, and enhance reliability. a good tradeoff is achieved through dead time control. the low idle loss and good emi system design is easier to achiev e with this dedicated control scheme. an internal 16v clamp is added for mosfet gate prot ection at higher than expected v dd input.
uc3863a linear integrated circuit unisonic technologies co., ltd 7 of 10 www.unisonic.com.tw qw-r103-148.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. v fb driver on / off t t v fb(in) v olp t 1 v olp for continual a blanking time. the olp event as followed fig.4. otp otp will shut down driver when junction temperature t j >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 uc3863a , and increasing the power mo s gate resistance is advised.
uc3863a linear integrated circuit unisonic technologies co., ltd 8 of 10 www.unisonic.com.tw qw-r103-148.b ? refrence circuit (12v/1.5a) bom reference component reference component bd1 1n40074 l2 33 h 68mm cx1 (optional) nc q1 4n65k cy1 (optional) yc 102p/400v (y1) r1,r2 r 4.7m ? 1206 c2 ec 33 f/400v 105c r3 r 200k c1 ec 6.8 f/400v 105c r4 (optional) 0 ? c3 cc 0.001 f/1000v r5 r 24.9 ? c4 ec 10 f/50v r6 r 42.21 ? 1206 c5,c13 (optional) cc 104p/50v r7 r 0.66 ? 1w c7 (optional) nc r8 r 51k ? 1206 c8 cc 103p/25v r9 r 100k ? 0805 c9 nc r10 nc c10 ec 470u/10v r12 r 220 ? 0805 c11 ec 220u/10v r13 r 1k ? 0805 c12 cc 103p/50v 0805 r14 r 10k ? 0805 c14 nc r15 r 100k ? 0805 d2 diode fr107 r16 r 25.94k ? 0805 d4 (optional) 1n4148 t1 ee-219 d5 mbr10100 u1 ic uc3863a f1 2a/250v u2 tl431 l1 nc u3 pc817
uc3863a linear integrated circuit unisonic technologies co., ltd 9 of 10 www.unisonic.com.tw qw-r103-148.b ? typical characteristics
uc3863a linear integrated circuit unisonic technologies co., ltd 10 of 10 www.unisonic.com.tw qw-r103-148.b ? typical characteristics (cont.) 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.
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