?on-bright electronics - 1 - ob_doc_ds_1100 ob2211/ob2212 primary-side regulation pwm power switch general description ob2211/ob2212 is an offline pwm power switch for low power ac/dc charger and adaptor applications. it operates in primary-side sensing and regulation. consequently, opto-coupler and tl431 could be eliminated from design. proprietary constant voltage (cv) and constant current (cc) control is integrated as shown in the figure below. in cc control, the current and output power setting can be adjusted externally by the sense resistor rs at cs pin. in cv control, multi-mode operations are utilized to achieve high performance and high efficiency. device operates in fixed frequency mode at large load conditions, fre quency reduction mode at light/medium load and ?extended burst mode? at no/light load conditions. ob2211/ob2212 offers power on soft start control and complete protection cove rage with auto-recovery features including cycle-by-cycle current limiting, vdd over-voltage clamp and uvlo, fail-safe protection for open loop fault condition. excellent emi performance is achieved with on-bright proprietary frequency shuffling technique together with soft switching control at the totem pole gate drive output with no-y cap design. fig 1. typical cc/cv curve features ? primary-side sensing and regulation with no tl431 and opto-coupler ? multi-mode operation for high efficiency ? programmable cv and cc regulation ? adjustable constant current and output power setting ? frequency shuffling and adjustable gate drive greatly improving emi ? power on soft-start time (4ms) ? ?extended burst mode control? for improved efficiency and minimum standby design ? built-in leading edge blanking (leb) ? cycle-by-cycle current limiting ? vdd under voltage lockout with hysteresis (uvlo) ? vdd over voltage shutdown and clamp ? auto-restart in over voltage condition ? fail-safe protection for open loop fault condition applications low power ac/dc offline smps for ? cell phone charger ? digital cameras charger ? small power adaptor ? auxiliary power for pc, tv etc. ? linear regulator/rcc replacement ob2211 is offered in sop8 package. ob2212 is offered in dip8 package typical application on-bright confidential to microbridge on-bright confidential to lycon
?on-bright electronics - 2 - ob_doc_ds_1100 ob2211/ob2212 primary-side regulation pwm power switch general information pin configuration the pin map is shown as below for sop8 and dip8. ordering information part number description OB2211CP sop8, pb-free, tube OB2211CPa sop8, pb-free, t&r ob2212ap dip8, pb-free absolute maximum ratings parameter value drain voltage (off state) -0.3v to 650v vdd voltage -0.3 to 33 v vddg voltage -0.3 to 33 v vdd zener clamp continuous current 10 ma cs input voltage -0.3 to 7v inv input voltage -0.3 to 7v min/max operating junction temperature t j -20 to 150 o c min/max storage temperature t stg -55 to 150 o c lead temperature (soldering, 10secs) 260 o c note: stresses beyond those listed under ?absolute maximum ratings? may cause permanent damage to the device. these are stress ratings only, functional operat ion of the device at these or any other conditions beyond those indicated under ?recommended operating conditions? is not im plied. exposure to absolute maximum-rated conditions for ex tended periods may affect device reliability. ob2211 x x x primary-side regu lation pwm power switch package c:sop8 packing blank : tube a : taping package pb-free p : lead free on-bright confidential to microbridge on-bright confidential to lycon
?on-bright electronics - 3 - ob_doc_ds_1100 ob2211/ob2212 primary-side regulation pwm power switch marking information terminal assignments pin num pin name i/o description 1 vddg p internal gate driver power supply 2 vdd p ic dc power supply input 3 inv i inverting input of error amplifier (ea). connected to resistor divider from primary sensing winding reflecting output voltage. pwm duty cycle is determined by ea output and current sense signal at pin 4. 4 cs i current sense input 5/6 drain o hv mosfet drain pin. the drain pin is connected to the primary lead of the transformer 7/8 gnd p ground output power table 230vac15% 90-264vac product open frame 1 open frame 1 ob2211 10w 8w ob2212 20w 12w notes: 1. maximum practical continuous power in an open frame des ign with sufficient drain pattern as a heat sink, at 50 ambient. on-bright confidential to microbridge on-bright confidential to lycon
?on-bright electronics - 4 - ob_doc_ds_1100 ob2211/ob2212 primary-side regulation pwm power switch block diagram cs inv 3 leb cc/cv operation burst mode controller pwm, & control logic 4 frequency shuffling soft start error amplifier 1.25v ea drain soft driver 5/6 vddg power mosfet 1 pwm genterator gnd 8 vdd 2 uvlo por regulator internal supply on-bright confidential to microbridge on-bright confidential to lycon
?on-bright electronics - 5 - ob_doc_ds_1100 ob2211/ob2212 primary-side regulation pwm power switch electrical characteristics (t a = 25 o c, vdd=vddg=16v, if not otherwise noted) symbol parameter test conditions min typ max unit supply voltage (vdd) section i dd st standby current vdd=13v 5 10 ua i dd op operation current operation supply current inv=1.25v, cs=0v, vdd=vddg=20v - 1.0 2.0 ma uvlo(on) vdd under voltage lockout enter 7.5 8.5 9.5 v uvlo(off) vdd under voltage lockout exit 14.0 15 16.0 v ovp(on) over voltage protection voltage cs=0v,inv=1v ramp up vdd until gate clock is off 28.5 30.0 31.5 v v dd _clamp i dd =10ma 33 v current sense input section t leb leb time 540 ns vth_oc v th _oc_test 780 820 860 mv td_oc propagation delay 300 ns z sense _in input impedance 50 kohm t_ss soft start time 4 ms cv section freq normal mode frequency 45 50 55 khz freq_burst burst mode base frequency 22 khz f/freq frequency shuffling range +/-4 % cc section minimum frequency 12 khz freq oscillation frequency maximum frequency 50 khz error amplifier section vref_ea reference voltage for ea 1.21 1.25 1.29 v gdc dc gain of the ea 50 db gbw unity gain bandwidth 37.5 khz power mosfet section bvdss mos drain-source breakdown voltage 650 v ob2211 12 15 rds(on) static drain to source on resistance ob2212 10 12 ? on-bright confidential to microbridge on-bright confidential to lycon
?on-bright electronics - 6 - ob_doc_ds_1100 ob2211/ob2212 primary-side regulation pwm power switch characterization plots on-bright confidential to microbridge on-bright confidential to lycon
?on-bright electronics - 7 - ob_doc_ds_1100 ob2211/ob2212 primary-side regulation pwm power switch operation description ob2211 and ob2212 are cost effective pwm power switch optimized for off-line low power ac/dc applications includi ng battery chargers and adaptors. it operates in primary side sensing and regulation, thus opto-coupler and tl431 are not required. proprietary cc control and built-in error amplifier can achieve a good cc/cv performance. z startup current and start up control startup current of ob2211/2 is designed to be very low so that vdd could be charged up above uvlo threshold and starts up quickly. a large value startup resistor can therefore be used to minimize the power loss in application. z operating current the operating current of ob2211/2 is as low as 1ma. good efficiency is achieved with the low operating current together with ?extended burst mode? control features. z soft start ob2211/2 features an internal 4ms soft start to minimize the component electrical over-stress during power on startup. as soon as vdd reaches uvlo(off), the control algorithm will ramp peak current voltage threshold gradually from nearly zero to normal setting of 0.82v. every restart is a soft start. z cc/cv operation ob2211/2 is designed to produce good cc/cv control characteristic as shown in the fig. 1. in charger applications, a discharged battery charging starts in the cc portion of the curve until it is nearly full charged and smoothly switches to operate in cv portion of the curve. in an ac/dc adapter, the normal operation occurs only on the cv portion of the curve. the cc portion provides added cycle-by-cycle current limiting protection. in cv operation, the output voltage is sensed on the primary side and the sensed signal controls the duty cycle through a built-in error amplifier (ea). to support ob2211/2 proprietary cc/cv control, system needs to be designed in dcm mode for flyback system. when inv is equivalent or larger than 1.25v, the system works in cv control, otherwise, the system works in cc control. z error amplifier (ea) connected to a resistor divider from the primary side sensing winding, the inverting input of the error amplifier (ea) is compared to an internal reference voltage of 1.25v to regulate the output voltage. the ea output is internally connected to the pwm generator and controls the duty cycle. z adjustable cc point and output power in ob2211/2, the cc point and output power can be externally adjusted by external current sense resistor rs at cs pin. the output power is adjusted through cc point change. the larger rs, the smaller cc point is, and the smaller output power becomes, and vice versa as shown in fig.2. fig. 2 adjustable output power by changing rs z extended burst mode operation at light load or zero load condition, most of the power dissipation in a switching mode power supply is from switching loss, the core loss of the transformer and the loss on the snubber circuit. the magnitude of power loss is in proportion to the switching frequency. lower switching frequency leads to the reduction on the power loss and thus conserves the energy. ob2211/2 self adjusts the switching frequency according to the loading condition. the switch frequency is reduced at light/no load condition to improve the conversion efficiency. at light load/no load condition, the output of the error amplifier (ea) drops below the burst mode threshold level and device enters burst mode control. the frequency control also eliminates the audio noise at any loading conditions. z operation switching frequency the switching frequency of ob2211/2 is internally set and adjusted according to cc/cv operation. no external frequency setting components are required. on-bright confidential to microbridge on-bright confidential to lycon
?on-bright electronics - 8 - ob_doc_ds_1100 ob2211/ob2212 primary-side regulation pwm power switch z frequency shuffling for emi improvement the frequency shuffling/jittering (switching frequency modulation) is implemented in ob2211/2. the oscillation frequency is modulated with a pseudo random source so that the tone energy is spread out. the spread spectrum minimizes the conduction band emi and therefore eases the system design. z current sensing and leading edge blanking cycle-by-cycle current limiting is offered in ob2211/2 current mode pwm control. the switch current is detected by a sense resistor into the cs pin. an internal leading edge blanking circuit chops off the sensed voltage spike at initial internal power mosfet on state due to snubber diode reverse recovery and surge current of power mosfet due to drain/source cap so that the external rc filtering on sense input is no longer needed. the pwm duty cycle is determined by the current sense input voltage and the ea output voltage. z adjustable drive capability the internal power mosfet in ob2211/2 is driven by a dedicated gate driver for power switch control. too weak the gate drive strength results in higher conduction and switch loss of mosfet while too strong gate drive compromises emi. a good tradeoff is achieved through the built-in totem pole gate design with right output strength control. the gate drive strength can be adjusted externally by a resistor connected between vdd and vddg the low idle loss and good emi system design is possible with this dedicated control scheme. z protection control good power supply system reliability is achieved with its rich protection features including cycle-by- cycle current limiting (ocp), vdd over voltage protection and clamp, power on soft start, and under voltage lockout on vdd (uvlo). vdd is supplied by transformer auxiliary winding output. pwm output of ob2211 is shut down when vdd is higher than 30v due to over voltage protection triggering. the output of ob2211 is shut down when vdd drops below uvlo(on) limit and switcher enters power on start-up sequence thereafter. on-bright confidential to microbridge on-bright confidential to lycon
?on-bright electronics - 9 - ob_doc_ds_1100 ob2211/ob2212 primary-side regulation pwm power switch package mechanical data dimensions in millimeters dimensions in inches symbol min max min max a 1.350 1.750 0.053 0.069 a1 0.100 0.250 0.004 0.010 a2 1.300 1.550 0.051 0.061 b 0.330 0.510 0.013 0.020 c 0.170 0.250 0.006 0.010 d 4.700 5.150 0.185 0.203 e 3.800 4.000 0.150 0.157 e1 5.800 6.200 0.228 0.244 e 1.270 (bsc) 0.050 (bsc) l 0.400 1.270 0.016 0.050 0o 8o 0o 8o on-bright confidential to microbridge on-bright confidential to lycon
?on-bright electronics - 10 - ob_doc_ds_1100 ob2211/ob2212 primary-side regulation pwm power switch dimensions in millimeters dimensions in inches symbol min max min max a 3.710 4.310 0.146 0.170 a1 0.500 0.020 a2 3.200 3.600 0.126 0.142 b 0.350 0.650 0.014 0.026 b1 1.524 (bsc) 0.060 (bsc) c 0.200 0.360 0.008 0.014 d 9.000 9.500 0.354 0.374 e 6.200 6.600 0.244 0.260 e1 7.320 7.920 0.288 0.312 e 2.540 (bsc) 0.100 (bsc) l 3.000 3.600 0.118 0.142 e2 8.200 9.000 0.323 0.354 on-bright confidential to microbridge on-bright confidential to lycon
|
