ts19701a cc/cv primary-side pwm controller 1/9 version: a12 sot - 26 description ts19701a is a high performance offline pwm power sw itch for low power ac/dc charger and adapter applications. it operates in primary-side sensing a nd regulation. consequently, opto-coupler and ts431 could be eliminated. proprietary constant voltage (cv) and c onstant 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 se nse resistor rs at cs pin. in cv control, multi-mode operations are utilized to achieve high performance and high e fficiency. in addition, good load regulation is achieved by the b uilt-in cable drop compensation. device operates in pfm in cc mode as well at large load condition and it operate s in pwm with frequency reduction at light/medium l oad. ts19701a offers power on soft start control and pro tection coverage with auto-recovery features includ ing cycle- by- cycle current limiting, vdd ovp, vdd clamp and uvlo. excellent emi performance is achieved with po wer- source proprietary frequency shuffling technique. h igh precision constant voltage (cv) and constant cu rrent (cc) can be achieved by ts19701a features 5% constant voltage regulation at universal ac input primary-side sensing and regulation programmable cv and cc regulation adjustable constant current and output power setting built-in adaptive current peak regulation built-in primary winding inductance compensation programmable cable drop compensation power on soft-start built-in leading edge blanking (leb) cycle-by-cycle current limiting vdd under voltage lockout with hysteresis application led lighting cell phone charger ordering information part no. package packing ts19701acx6 rfg sot-26 3kpcs / 7 reel note: g denote for halogen free product absolute maximum rating (ta = 25 o c unless otherwise noted) characteristics symbol rating unit drain voltage (off state) v drain -0.3 to bvdss v vdd voltage v dd -0.3 to vdd_clamp v vdd zener clamp continuous current -- 10 ma comp voltage v comp -0.3 to 7 v cs input voltage v cs -0.3 to 7 v inv input voltage v inv -0.3 to 7 v max operating junction temperature tj 150 c min/max storage temperature t stg -55 to 150 c thermal resistance from junction to case jc 180 c/w thermal resistance from junction to ambient ja 250 c/w pin definition : 1. gnd 2. gate 3. current sense 4. inv 5. compensation 6. v dd
ts19701a cc/cv primary-side pwm controller 2/9 version: a12 electrical specifications (ta = 25 o c unless otherwise noted) characteristics symbol conditions min typ max units supply voltage (vdd) section standby current i dd st v dd =13v -- 5 20 ua operation current i dd op operation supply current i nv =2v, c s =0v, v dd =v ddg =18v -- 2 3 ma vdd under voltage lockout enter u vlo(on) v dd falling 8.2 9.0 10.5 v vdd under voltage lockout exit u vlo(off) v dd rising 13.5 14.8 16.0 v maximum vdd operation voltage v dd clamp i dd =10ma 27 28.5 30 v over voltage protection voltage ovp ramp v dd until gate shut down 26 27.5 29 v current sense input section leb time t leb -- 625 -- ns over current threshold vth_oc 880 910 940 mv ocp propagation delay td_oc -- 110 -- ns input impedance z sense _in 50 -- -- k ? soft start time t_ ss -- 17 -- ms frequency section ic maximum frequency freq_max (note) 55 60 65 khz system nominal switch frequency freq_nom -- 50 -- khz freq_startup i nv =0v, comp=5v -- 14 -- khz frequency shuffling range ? f/freq -- +/-6 -- % error amplifier section reference voltage for ea vref_ea 1.97 2 2.03 v dc gain of ea gain - 60 - db max. cable compensation current i_comp_ma x i nv =2v, comp=0v - 37.5 - ua note: freq_max indicates ic internal maximum clock frequ ency. in system application, the maximum operation frequency of 60khz nominal occurs at maximum output power or the transition point from cv to cc
ts19701a cc/cv primary-side pwm controller 3/9 version: a12 typical application circuit block diagram pin description pin function description 1 gnd ground 2 gate drive mosfet 3 cs current sense input 4 inv the voltage feedback from auxiliary winding 5 comp loop compensation for cv stability 6 vdd power supply
ts19701a cc/cv primary-side pwm controller 4/9 version: a12 function description ts19701a is a cost effective pwm power switch optim ized for off-line low power ac/dc applications incl uding battery chargers and adapters. it operates in prima ry side sensing and regulation, thus opto-coupler a nd tl431 are not required. proprietary built-in cv and cc contro l can achieve high precision cc/cv control meeting most adapter and charger application requirements. startup current and start up control startup current of ts19701a is designed to be very low so that vdd could be charged up above uvlo thre shold and starts up quickly. a large value startup resist or can therefore be used to minimize the power loss in application. operating current the operating current of ts19701a is as low as 2.0m a. good efficiency is achieved with the low operati ng current together with muti-mode control features. soft start ts19701a features an internal soft start to minimiz e the component electrical over-stress during power on startup. as soon as vdd reaches uvlo (off), the control algo rithm will ramp peak current voltage threshold grad ually from nearly zero to normal setting of 0.91v. every restart is a soft start. cc/cv operation ts19701a 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 f ull charged and smoothly switches to operate in cv portion of the c urve. in an ac/dc adapter, the normal operation occ urs only on the cv portion of the curve. the cc portion provide s output current limiting. in cv operation, the out put voltage is regulated through the primary side control. in cc o peration mode, ts19701a will regulate the output cu rrent constant regardless of the output voltage drop. principle of operation to support ts19701a proprietary cc/cv control, syst em needs to be designed in dcm mode for flyback sys tem (refer to typical application diagram on page1). in the dcm flyback converter, the output voltage can be sensed via the auxiliary winding. during mosfet turn-on ti me, the load current is supplied from the output fi lter capacitor co. the current in the primary winding ramps up. wh en mosfet turns off, the primary current transfers to the secondary at the amplitude of the auxiliary voltage reflects the output voltage a s shown in fig.2 and it is given by where ? v indicates the drop voltage of the output diode.
ts19701a cc/cv primary-side pwm controller 5/9 version: a12 function description (continue) fig.2. auxiliary voltage waveform via a resistor divider connected between the auxili ary winding and inv (pin 4), the auxiliary voltage is sampled at the end of the demagnetization and it is hold until the next sampling. the sampled voltage is compared with vref (2.0v) and the error is amplified. the error amplif ier output comp reflects the load condition and con trols the pwm switching frequency to regulate the output voltage, thus constant output voltage can be achieved. when sampled voltage is below vref and the error amplifier outpu t comp reaches its maximum, the switching frequency is controlled by the sampled voltage thus the output v oltage to regulate the output current, thus the con stant output current can be achieved. adjustable cc point and output power in ts19701a, the cc point and maximum output power can be externally adjusted by external current sens e resistor rs at cs pin as illustrated in typical app lication diagram. the output power is adjusted thro ugh cc point change. the larger rs, the smaller cc point is, and the smaller output power becomes, and vice versa a s shown in fig.3 fig.3 adjustable output power by changing rs
ts19701a cc/cv primary-side pwm controller 6/9 version: a12 function description (continue) operation switching frequency the switching frequency of ts19701a is adaptively c ontrolled according to the load conditions and the operation modes. no external frequency setting components are required. the operation switching frequency at max imum output power is set to 60khz internally. for flyback operating in dcm, the maximum output po wer is given by where lp indicate the inductance of primary winding and ip is the peak current of primary winding. ref er to the equation 3, the change of the primary winding induc tance results in the change of the maximum output p ower and the constant output current in cc mode. to compensa te the change from variations of primary winding in ductance, the switching frequency is locked by an internal lo op such that the switching frequency is since tdemag is inversely proportional to the induc tance, as a result, the product lp and fsw is const ant, thus the maximum output power and constant current in cc mod e will not change as primary winding inductance cha nges. up to 10% variation of the primary winding inducta nce can be compensated. frequency shuffling for emi improvement the frequency shuffling (switching freq uency modulation) is implemented in ts19701a. the oscillation frequency is modulated so that the tone energy is spread out. the spread spectrum minimize s the conduction band emi and therefore eases the system design. current sensing and leading edge blanking cycle-by-cycle current limiting is offered in ts197 01a current mode pwm control. the switch current is detected by a sense resistor into the cs pin. an internal le ading edge blanking circuit chops off the sensed vo ltage spike at initial internal power mosfet on state so that the external rc filtering on sense input is no longer n eeded. the pwm duty cycle is determined by the current sense i nput voltage and the ea output voltage. gate drive the internal power mosfet in ts19701a is driven by a dedicated gate driver for power switch control. t oo weak the gate drive strength results in higher conductio n and switch loss of mosfet while too strong gate d rive compromises emi. a good tradeoff is achieved throug h the built-in totem pole gate design with right ou tput strength control. programmable cable drop compensation in ts19701a, cable drop compensation is implemented to achieve good load regulation. an offset voltage is generated at inv by an internal current flowing int o the resister divider. the current is inversely pr oportional to the voltage across pin comp, as a result, it is inverse ly proportional to the output load current, thus th e drop due to the cable loss can be compensated. as the load current decreases from full-load to noload, the offset volt age at inv will increase. it can also be programmed by adjusti ng the resistance of the divider to compensate the drop for various cable lines used.
ts19701a cc/cv primary-side pwm controller 7/9 version: a12 function description (continue) protection control good power supply system reliability is achieved wi th its rich protection features including cycle-by- cycle current limiting (ocp), vdd clamp, power on soft start, and under voltage lockout on vdd (uvlo). vdd is supplied by transformer auxiliary winding ou tput. the output of ts19701a is shut down when vdd drops below uvlo (on) limit and switcher enters power on start-up sequence thereafter.
ts19701a cc/cv primary-side pwm controller 8/9 version: a12 sot-26 mechanical drawing unit: millimeters
ts19701a cc/cv primary-side pwm controller 9/9 version: a12 notice specifications of the products displayed herein are subject to change without notice. tsc or anyone on its behalf, assumes no responsibility or liability for any erro rs or inaccuracies. information contained herein is intended to provide a product description only. no license, express or implied, to any intellectual property rights is granted by this document. except as provided in tscs terms and co nditions of sale for such products, tsc assumes no liability wh atsoever, and disclaims any express or implied warr anty, relating to sale and/or use of tsc products includi ng liability or warranties relating to fitness for a particular purpose, merchantability, or infringement of any patent, cop yright, or other intellectual property right. the products shown herein are not designed for use in medical, life-saving, or life-sustaining applica tions. customers using or selling these products for use i n such applications do so at their own risk and agr ee to fully indemnify tsc for any damages resulting from such i mproper use or sale.
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