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?2000 fairchild semiconductor international www.fairchildsemi.com rev. 5.0 features ? internal startup timer ? internal r/c filter which eliminates the need for an external r/c filter ? overvoltage comparator eliminates runaway output voltage ? zero current detector ? one quadrant multiplier ? trimmed 1.5% internal bandgap reference ? under voltage lock out with 5v of hysteresis ? totem pole output with high state clamp ? low startup and operating current ? 8-pin dip or 8-pin sop applications ? electronic ballast ?smps descriptions the KA7526 provides simple and high performance active power factor correction. KA7526 is optimized for electronic ballast and low power, high density power supplies requiring a minimum board area, reduced component count and low power dissipation. addition of internal r/c filter eliminates the need for an external r/c filter. internal clamping of the error amplifier and multiplier outputs improves turn on over- shoot characteristics and current limiting. special circuitry has also been added to prevent no load runaway conditions. the output drive clamping circuit limits overshoot of the power mosfet gate drive independent of supply voltage, so that it greatly enhance the system reliability. KA7526 power factor correction controller 8-dip 8-sop 1 1
KA7526 2 internal block diagram ic characteristics parmaeter KA7526 uvlo 8/13v multiplier input range (vm1) 0 ~ 3.8v multiplier input range (vm2) vref ~ verf + 2v maximum current sense voltage 1.65v pin4 threshold(vmo) k = + - + - vm1 ? (vm2-vref) 2.5v ref internal bias + - timer r + - + - 8 7 5 6 1 4 3 2 v cc 36v uvlo 7.5v 1.8v zero current detector current sense comparator vmo vm1 multiplier vm2 error amp gnd ea out vea(-) inv 1.8v + - over voltage protection out v cc s r q drive output vref vref idet cs mult 240mv 5v 13v 40k ? 8pf 1.65v 0~3.8v vref~vref+2v
KA7526 3 pin assignments pin definitions pin number pin name pin function descrition 1 inv inverting input of the error amplifier. the output of the boost converter should be resistively divided to 2.5v and con- nected to this pin. 2ea out the output of the error amplifier. a feedback compensation network is placed between this pin and the inv pin 3mult input to the multiplier stage. the full-wave rectified ac is divided to less than 3.8v and is connected to this pin. 4cs input to the pwm comparator. the current is sensed in the boost stage by a resistor in the source lead of mosfet. an internal leading edge blanking circuitry has been included to reject any high frequency noise present on the current waveform. 5 idet the zero current detector senses the inductor current by monitoring when the boost inductor auxilary winding voltage falls below 1.8v. 6 gnd the ground potential of all the pins. 7out the output of a high-current power driver capable of driving the gate of a power mosfet. 8v cc the logic and control power supply connection. 1 2 3 45 6 7 8 inv ea out mult cs vcc out gnd idet (top view)
KA7526 4 absolute maximum ratings note : based in 8-dip temperature characteristics (-25 o c ta 125 o c ) parameter symbol value unit supply voltage v cc 30 v peak drive output current i oh , i oi 500 ma driver output clamping diodes v o >v cc or v o <-0.3v iclamp 10 ma detector clamping diodes idet 3ma error amp, multiplier and comparator input voltage v in -0.3 to 6 v operating temperature range topr -25 to 125 o c storage temperature range tstg -65 to 150 o c power dissipation (note) pd 0.8 w thermal resistance (note) (junction-to-air) qja 100 o c /w parameter symbol value unit temperature stability for reference voltage(vref) ? vref (typ) 20 mv temperature stability for multiplier gain(k) ? k/ ? t (typ) -0.2 %/ o c
KA7526 5 electrical characteristics unless otherwise specified, for typical values vcc=12v, ta=25 o c, for min/max values ta is the operating ambient temperature range with -25 o c ta 125 o c . parameter symbol condition min. typ. max. unit under voltage lock out section start threshold voltage vth (st) v cc increasing 12 13 14 v uvlo hysteresis hy(st) - 4 5 6 v supply zener voltage vz i cc =10ma 30 36 - v supply current section start up supply current ist v cc KA7526 6 electrical characteristics (continued) notes : 1. because the reference is not brought out externally, this specification cannot be tested on the package part. it is guarantee d by design. 2. this parameter, although guaranteed, is not tested in production. 3. k = parameter symbol condition min. typ. max. unit current sense section input offset voltage (note2) vio(cs) vm1=0v, vm2=2.2v -10 3 10 mv input bias current ib(cs) 0v v cc 1.7v -1 -0.3 1 a current sense delay to output (note2) td(cs) - - 200 500 ns detect section detect input threshold vth(det) vdet increasing 1.5 1.8 2.1 v detect hysteresis hy(det) - 180 240 400 mv input low clamp voltage vclamp(i) idet=-100 a 0.45 0.75 1 v input high clamp voltage vclamp(h) idet=3ma 6.7 7.5 8.3 v input bias current ib(det) 1v vdet 6v -1 -0.2 1 a input high/low clamp diode current (note2) iclamp - - - 3ma output driver section output voltage high v oh i o =-10ma, v cc =12v 8.5 9 - v output voltage low v ol i o =10ma, v cc =12v - 0.8 1 v rising time (note2) tr ci=1nf - 130 200 ns falling time (note2) tf ci=1nf - 50 120 ns maximum output voltage vomax(o) v cc =20v 12 13 15 v output voltage with uvlo activated vomin(o) v cc =5v, i o =100 a--1v restart timer section restart time delay td(rst) vm1=1v, vm2=3.5v - 300 - s overvoltage protection section voltage feedback input threshold vth(ovp) vcs=-0.5v, vm1=1v vdet=0v 1.7 1.8 1.9 v pin4 threshold vm1 (vm2-vref) (vm1=vpin3, vm2=vpin2)
KA7526 7 typical performance characteristics 2.5 3.0 3.5 4.0 4.5 5.0 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 fig1. e.a. output voltage vs c.s. threshold vm1=1.5v vm1=1v vm1=4v vm1=0.5v c.s threshold voltage [v] ea output voltage [v] 012345 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 fig2. multiplier input voltage vs c.s. threshold veao=3.25v veao=3v veao=2.75v veao=5v veao=2.5v c.s. threshold voltage [v] multiplier input voltage [v] 0 5 10 15 20 25 30 35 40 45 0.0 2.5 5.0 7.5 10.0 12.5 15.0 17.5 20.0 fig3. supply current vs supply voltage supply current [ma] supply voltage [v] -40 -20 0 20 40 60 80 100 120 140 2.45 2.46 2.47 2.48 2.49 2.50 2.51 2.52 2.53 2.54 fig4. reference voltage vs temperature reference voltage(v) ambient temperature( ) -40 -20 0 20 40 60 80 100 120 140 12.5 12.6 12.7 12.8 12.9 13.0 13.1 13.2 13.3 13.4 fig5. start-up threshold vs temperature start-up threshold voltage(v) ambient temperature( ) -40-20 0 20406080100120140 3.5 4.0 4.5 5.0 5.5 6.0 6.5 fig6. uv lockout hysteresis vs temperature uv lockout hysteresis(v) ambient temperature ( ) figure 1. ea output voltage vs c.s. threshold figure 2. multiplier input voltage vs c.s. threshold figure 3. supply current vs supply voltage figure 4. reference voltage vs temperature figure 5. start-up threshold vs temperature figure 6. uv lockout hysteresis vs temperature
KA7526 8 typical performance characteristics (continued) -40 -20 0 20 40 60 80 100 120 140 0.00 0.04 0.08 0.12 0.16 0.20 0.24 0.28 0.32 0.36 0.40 fig7. start-up supply current vs temperature start-up supply current(ma) ambient temperature( ) -40 -20 0 20 40 60 80 100 120 140 -10 -9 -8 -7 -6 -5 -4 -3 -2 fig8. e.a. source current vs temperature ea source current(ma) ambient temperature( ) -40 -20 0 20 40 60 80 100 120 140 0 1 2 3 4 5 6 7 8 9 10 fig9. sink current vs temperature ea sink current(ma) ambient temperature( ) -40 -20 0 20 40 60 80 100 120 140 -0.5 -0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 fig.10 input bias current vs temperature ea input bias current( ? ) ambient temperature( ) -40 -20 0 20 40 60 80 100 120 140 0.45 0.50 0.55 0.60 0.65 0.70 0.75 fig.11 multiplier gain vs temperature multiplier gain(1/v) ambient temperature( ) -40 -20 0 20 40 60 80 100 120 140 1.68 1.72 1.76 1.80 1.84 1.88 1.92 fig.12 idet threshold high vs temperature idet threshold high(v) ambient temperature( ) figure 7. start-up supply current vs temperature figure 8. ea source current vs temperature figure 9. ea sink current vs temperature figure 10. ea input bias current vs temperatur e figure 11. multiplier gain vs temperature figure 12. idet threshold volyage vs temperature
KA7526 9 typical performance characteristics (continued) -40-20 0 20406080100120140 0 40 80 120 160 200 240 280 320 360 400 fig.13 idet input hysteresis vs temperature idet input hysteresis(mv) ambient temperature( ) -40-200 20406080100120140 0 100 200 300 400 500 600 fig.14 restart time vs temperature restart time( ? ) ambient temperature( ) -40 -20 0 20 40 60 80 100 120 140 1.45 1.50 1.55 1.60 1.65 1.70 1.75 1.80 1.85 fig.15 max. mult. output voltage vs temperature max. multi output voltage(v) ambient temperature( ) -40 -20 0 20 40 60 80 100 120 140 0 1 2 3 4 5 6 7 8 fig.16 supply current vs temperature supply current(ma) ambient temperature( ) figure 13. idet input hysteresis vs temperature figure 14. restart time vs temperature figure 15. max.mult.output voltage vs temperature figure 16. supply current vs temperature
KA7526 10 operating description KA7526 is high performance, critical conduction, current-mode power factor controller specifically designed for use in off- line active preconverters with minimal external components. this device provides the necessary features which are required to significantly en-hance poor power factor loads by keeping the ac line current sinusoidal and in phase with the line voltage. KA7526 contains many of the building blocks and protection features that are employed in modern high performance current mode power supply controllers. a description of each of the function blocks is given below. start-up an undervoltage lockout comparator has been incorporated to guarantee that ic is fully functional before enabling the output stage. the positive power supply terminal (vcc) is monitored by the uvlo comparator with the upper threshold set at 13v and the lower threshold at 8v. in the stand-by mode, with vcc at 12.5v, the required supply current is less than 0.3ma . this large hysteresis and low start-up current allow the implementation of efficient bootstrap start-up techniques, making this device ideally suited for wide range off-line preconverter applications. fig.1.1 shows the start-up circuit. circuit operation is as follows: the start-up capacitor (cst) is charged by current through start-up resistor (rst) minus the start-up current drawn by the ic. once the capacitor voltage reaches the start-up threshold, the ic turns on, starting the switching of the mosfet. the opera- tion of the ic demands an increase in operating current which results in discharging the capacitor. before the start-up capacit or voltage is discharged below hysteresis voltage, the auxiliary winding voltage takes over as the supply voltage as shown in fig. 1.2. ac input KA7526 vcc out dvcc rst cst + fig.1.1 start-up circuit t vstart cst discharges hysteresis cst charges from rst fig.1.2 start-up capacitor voltage vcc
KA7526 11 error amplifier an error amplifier with access to the inverting input and output is provided. the noninverting input is internally biased at 2.5v and is not pinned out. the output voltage of the power factor converter is typically divided down and monitored by the inverting input. the error amp output is internally connected to the multiplier and is pinned out for external loop compensa- tion. typically, the loopbandwidth is set below 20hz, so that the amplifer?s output voltage is relatively constant over a given ac line cycle. in effect, the error amp monitors the average output voltage of the converter over several line cycles. input bias cur- rent(0.5ua, max) can cause an output voltage error that is equal to the product of the input bias current and the value of the upper divider resistor, r1 in fig. 2.1. over voltage protection the low bandwidth (typically below 20hz) characteristic of error amplifier control loop results in output voltage runaway condition. this condition can occur during initial start-up, sudden load removal, or during output arcing. the over voltage comparator monitors the output voltage of the error amplifier. when load is removed, error amp output swings lower than 1.8v, comparator is triggered high and output driver is turned off till the error amp inverting input voltage drops below 2.5v. at this point, the error amp output swings positive, turns the output driver back on. . multiplier a single quadrant, two input multiplier is the critical element that enables this device to get power factor correction. one in put of multiplier(pin 3) is connected to an external resistor divider which monitors the rectified ac line. the other input is inte r- nally driven by a dc voltage which is the difference of error amplifier output (pin 2) and reference voltage, vref. the multi- plier is designed to have an extremely linear transfer curve over a wide dynamic range, 0v to 3.8v for pin 3, and 2.5v to 4.5v for error amplifier output under all line and load conditions. the multiplier output controls the current sense comparator threshold as the ac voltage traverses sinusoidally from zero to peak line. this allows the inductor peak current to follow the ac line thus forcing the average input current to be sinusoidal. in other words, this has the effect of forcing the mosfet on-time to track the input line voltage, resulting in a fixed drive outp ut on-time, thus making the preconverter load appear to be resistive to the ac line. the equation below describes the relationship between multiplier output and inputs. vmo = k vm1 (vm2-vref) k : multiplier gain vm1: voltage at pin 3 vm2: error amp output voltage vmo: multiplier output voltage - + - + x 1 2 inv ea out 1.8v vref over voltage vref to multiplier to d riv e output shutdown ccomp comparator r1 r2 r3 band width= 1/(2 r1 ccomp) + _ fig.2.1 error amp and over voltage comparator +
KA7526 12 current sense comparator the current sense comparator adopt the rs latch configuration to ensure that only a single pulse appears at the drive output during a given cycle. mosfet drain current is converted to voltage using an external sense resistor in series with the external power mosfet. when sense voltage exceeds the threshold set by the multiplier output, the current sense comparator termi- nates the gate drive to the mosfet and resets the pwm latch. the latch insures that the output remains in a low state after the mosfet drain current falls back to zero. the peak inductor current under normal operating conditions is controlled by the multiplier output, vmo. abnormal operating conditions occur during preconverter start-up at extremely high line or as output voltage sensing is lost. under these conditions, the multiplier output and current sense threshold will be internally clamped to 1.65v. therefore, the maximum peak switch current is limited to: ipk(max) = 1.65v / rsense an internal r/c filter has been included to attenuate any high frequency noise that may be present on the current waveform. this circuit block eliminates the need for an external r/c filter otherwise required for proper operation of the circuit. + - + - + + vref 2 3 1.65v current sense comparator error amp . vmo vm1 vm2 inv mult ea out + - 1 fig.3.1 multiplier block 4 cs 4 cs 1.65v multiplier output rsense can be eliminated external r/c filter fig. 4.1 current sense circuit + -
KA7526 13 zero current detector KA7526 operates as a critical conduction current mode controller. the power mosfet is turned on by the zero current detec- tor and turned off when the peak inductor current reaches the threshold level established by the multiplier output. the slope o f the inductor current is indirectly detected by monitoring the voltage across a separate winding and connecting it to the zero current detector pin 5. once the inductor current reaches ground level, the voltage across the winding reverses polarity. when the idet input falls below 1.8v, the comparator output is triggered to the low state. to prevent false tripping, 240mv of hysteresis is provided. the zero current detector input is internally protected by two clamps. the upper 7.5v clamp prevents input over voltage breakdown while the lower 0.75v clamp prevents substrate injection. an internal current limit resistor protects the lower clamp transistor in case the idet pin is accidently shorted to ground. a watchdog timer function was added to the ic to eliminate the need for an external oscillator when used in stand-alone appli- cations. the timer provides a means to automatically start or restart the preconverter if the drive output has been off for mor e than 300us after the inductor current reaches zero. drive output the KA7526 contains a single totem-pole output stage specifically designed for direct drive of power mosfet. the drive output is capable of up to 500ma peak current with a typical rise and fall time of 130ns, 50ns each with a 1.0nf load. addi- tional internal circuitry has been added to keep the drive output in a sinking mode whenever the uvlo is active. this charac- teristic eliminates the need for an external gate pull-down resistor. internal voltage clamping ensures that output driver is always lower than 13v when supply voltage variation exceeds more than rated vgs threshold (typ 20v) of the external mos- fet. this eliminates an external zener diode and extra power dissipation associated with it that otherwise is required for reli - able circuit operation.
KA7526 14 application circuit #1 < 90 ~ 265v ac input, 400v dc , 32w 2 lamps self-oscillating ballast > d1 d2 d3 d4 c4 r1 r2 r4 v1 l1 c1 c3 c2 fuse ac input + c7 r3 c5 r8 c10 + c8 c6 6 4 3 8 1 5 7 2 ic 1 r7 d6 r5 r6 l2 d5 r11 q1 r9 r10 c9 q2 r13 c11 l6 r14 l5 l5 l3 l4 r17 r18 d7 d8 r16 c13 l5 l7 r15 q3 c12 c14 c15 lamp 1 lamp 2 c16 gnd KA7526
KA7526 15 component listing (for application circuit #1) reference value part number manufacturer r1, 2 1.2m ? -f, 1/4w 26mm type - r3 11k ? -f, 1/4w 26mm type - r4 150k ? , 1/2w 26mm type - r5 22k ? -j, 1/4w 26mm type - r6, 13, 15 47 ? -j, 1/4w 26mm type - r7 3.3 ? , 1/4w 26mm type - r8 1 ? -j, 1w 26mm type - r9 180k ? -f, 1/4w 26mm type - r10 820k ? -f, 1/4w 26mm type - r11 6.8k ? -f, 1/4w 26mm type - r12, 17, 18 390k ? -j, 1/4w 26mm type - r14, 16 8.2 ? -j, 1/4w 26mm type - c1 0.15uf, 630v mep-cap - c2, 3 2200pf, 3000v y-cap - c4 0.22uf, 630v mpe-cap - c5 22uf, 35v electrolytic - c6 0.33uf, 25v ceramic - c7 1000pf, 50v ceramic - c8 47uf, 450v electrolytic - c9 4700pf, 630v ppf-cap - c10 2200pf, 630v ppf-cap - c11, 12 0.15uf, 63v mpf-cap - c13 0.1uf, 50v ceramic - c14, 15 8200pf, 1000v pp-cap - c16 0.15uf, 630v mep-cap - d1, 2, 3, 4, 7 1000v, 1a in4007gp - d5 1000v, 1.5a byv26c philips d6 75v, 150ma in4148 - d8 - n413n (diac) - l1 dr 10 12 dit-010 - l2 ei 2519 dbt-002 - l3, 4 ei 2820 dpt-086 - l5 sb5s 8 3 4 ddt-005 - l6, 7 10uh bs24-100k - fuse - 52nm250v, 3a - v1 430v inr140, 431 - ic1 - KA7526 fairchild q1 500v, 4.5a qfp6n50 fairchild q2, 3 400v, 5a ksc5305d fairchild
KA7526 16 application circuit #2 < 90 ~ 265v ac input, 400v dc , 32w 2 lamps external-oscillating ballast > 8 765 1234 fuse l1 c2 ac input v1 c1 c4 c3 ntc d1 d4 d2 d3 c5 r3 r4 c6 r6 r5 q1 c9 r7 r8 d5 d6 + + r1 r2 c8 pfc output full-wave rectified output KA7526 c7 r9 l2 8 76 5 1234 to pfc output c9 + t1 r10 q2 q3 r11 l3 l4 d7 c14 r16 d8 r12 c10 c11 c12 r13 r18 r19 c19 c20 + c17 c18 c13 r17 c15 r15 r14 lamp2 lamp1 r16 to f u l l - w a v e rectified output ka7541 z1
KA7526 17 component listing (for application circuit #2) reference value part number manufacturer r1 2.2m ? -f, 1/4w 26mm type - r2 12k ? -f, 1/4w 26mm type - r3, 12 150k ? , 1/2w 26mm type - r4 22k ? -j, 1/4w 26mm type - r5, 10, 11 47 ? -j, 1/4w 26mm type - r6 3.3 ? , 1/4w 26mm type - r7 1 ? -j, 1w 26mm type - r8 1.2m ? -f, 1/4w 26mm type - r9 10k ? variable resistor - - r13 22k ? -f, 1/4w 26mm type - r14 180k ? -j, 1/4w 26mm type - r15, 16 330k ? -j, 1/4w 26mm type - r17, 18 680k ? -j, 1/4w 26mm type - r19 8.2k ? -j, 1/4w 26mm type - c1, 2 0.15uf, 630v mep-cap - c3, 4 2200pf, 3000v y-cap - c5 0.1uf, 400v mpe-cap - c6 22uf, 35v electrolytic - c7 0.33uf, 25v mpe-cap - c8 0.01uf, 25v mpe-cap - c9 47uf, 450v electrolytic - c10 47uf, 35v electrolytic - c11 0.22uf, 25v mpe-cap - c12 180pf, 25v ceramic - c13 0.1uf, 25v mpe-cap - c14 1000pf, 630v mpe-cap - c15, 16 4700pf, 1000v mpe-cap - c17, 18, 19, 20 6800pf, 630v mpe-cap - d1, 2, 3, 4 1000v, 1a 1n4007 - d5 frd(25ns) byv26c philips d6 75v, 150ma 1n4148 - d7,8 1000v, 1.5a 1n4937 - l1 80mh bsf2125 - l2 1.2mh (100t: 7t) litz wire or ustc ei2820 - l3, 4 3.1mh litz wire or ustc ei2820 - t1 1.2mh(35t:24t:24t) ee1614 - fuse - 52nm250v, 3a - v1 430v inr140, 431 - q1, 2, 3 500v, 6a skp6n50 fairchild z1 15v, 1w - -
KA7526 18 mechanical dimensions package dimensions in millimeters 6.40 0.20 3.30 0.30 0.130 0.012 3.40 0.20 0.134 0.008 #1 #4 #5 #8 0.252 0.008 9.20 0.20 0.79 2.54 0.100 0.031 () 0.46 0.10 0.018 0.004 0.060 0.004 1.524 0.10 0.362 0.008 9.60 0.378 max 5.08 0.200 0.33 0.013 7.62 0~15 0.300 max min 0.25 +0.10 ?.05 0.010 +0.004 ?.002 8-dip
KA7526 19 mechanical dimensions (continued) package dimensions in millimeters 4.92 0.20 0.194 0.008 0.41 0.10 0.016 0.004 1.27 0.050 5.72 0.225 1.55 0.20 0.061 0.008 0.1~0.25 0.004~0.001 6.00 0.30 0.236 0.012 3.95 0.20 0.156 0.008 0.50 0.20 0.020 0.008 5.13 0.202 max #1 #4 #5 0~8 #8 0.56 0.022 () 1.80 0.071 max0.10 max0.004 max min + 0.10 -0.05 0.15 + 0.004 -0.002 0.006 8-sop
KA7526 20 ordering information product number package operating temperature KA7526 8-dip -25 ~ +125 o c KA7526d 8-sop
KA7526 21
KA7526 9/25/00 0.0m 001 stock#dsxxxxxxxx ? 2000 fairchild semiconductor international life support policy fairchild?s products are not authorized for use as critical components in life support devices or systems without the express written approval of the president of fairchild semiconductor international. as used herein: 1. life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and (c) whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury of the user. 2. a critical component in any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. www.fairchildsemi.com disclaimer fairchild semiconductor reserves the right to make changes without further notice to any products herein to improve reliability, function or design. fairchild does not assume any liability arising out of the application or use of any product or circuit described herein; neither does it convey any license under its patent rights, nor the rights of others.

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