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| CM6802A/b/ah/bh (dynamic soft pfc/green pwm) http://www.championmicro.com.tw epa/80++ zvs-like pfc/pwm combo controller design for high efficient power supply at both full load and light load 2012/05/10 rev. 1.5 champion microelectronic corporation 1 general description features switching to CM6802A/b/ah/bh from your existing cm6800 family boards can gain the following advanced performances: 1.) around 2% efficiency gain when the output load is below 40% of the full load. 2.) hold up time can be increased ~ 30% from the existing 6800 power supply. 3.) 420v bulk capacitor value may be reduced pfc boost ripple current can be reduced; therefore, the boost inductor core size maybe reduced. 4.) no load consumption can be reduced 290mw at 270vac. 5.) pwm transformer size can be smaller. 6.) to design 12v, 5v and 3. 3v output filters can be easy. 7.) the stress over the entire external power device is reduced and emi noise maybe reduced. 8.) monotonic output des ign is easy and more?of cause, the cost will be reduced. CM6802A/b/ah/bh is pin to pin compatible with cm6800 family. beside all the goodies in the cm 6800, it is designed to meet the epa/80+ regulation. with the proper design, its efficiency of power supply can easily approach 85%. to start evaluating CM6802A/b /ah/bh from the exiting cm6800,cm6800a or ml4800 boar d, 6 things need to be taken care before doing the fine tune: 1.) change rac resistor (on pin 2, iac) from the old value to a higher resistor value between 4.7 mega ohms to 8 mega ohms. 2.) change rtct pin (pin 7) from the existing value to rt=7.75k ohm and ct=1000pf to have fpfc=55khz, fpwm=55khz, frtct=220khz. 3.) adjust all high voltage resistor around 5 mega ohm or higher. 4.) vrms pin (pin 4) needs to be 1.125v at vin=85vac for universal input application from line input from 85vac to 270vac. both poles for the vrms of the CM6802A/b/ah/bh needs to substantially slow than cm6800 about 5 to 10 times. 5.) at full load, the aver age veao needs to around 4.5v and the ripple on the veao needs to be less than 250mv. 6.) soft start pin (pin 5), t he soft start current has been reduced from cm6800?s 20ua to CM6802A/b/ah/bh?s 10ua.soft start capacitor can be reduced to 1/2 from your original cm6800 capacitor. ? patents pending ? pin to pin compatible with cm6800,cm6800a, ml4800 and fan4800. ? 23v bi-cmos process. ? designed for epa/ 80++ efficiency. ? CM6802A/b : selectable boost output from 380v to 300v during light load. ? CM6802Ah/bh: selectable boost output from 380v to 342v during light load. ? all high voltage resistors can be greater than 4.7 mega ohm (4.7 mega to 8 mega ohm) to improve the no load consumption. ? rail to rail cmos drivers with on, 60 ohm and off, 30 ohm for both pfc and pwm with two 17v zeners. ? fast start-up circuit without extra bleed resistor to aid vcc reaches 13v sooner. ? low start-up current (55ua typ.) ? low operating current (2.5ma typ.) ? 16.5v vcc shunt regulator ? leading edge blanking for both pfc and pwm. ? frtct = 4*fpfc =4*fpwm for CM6802A//ah ? frtct = 4*fpfc =2*fpwm for cm6802b/bh ? dynamic soft pfc to ease the stress of the power device and ease the emi filter design. ? pfc brown out and pwm brown out ? internally synchronized leading edge pfc and trailing edge pwm in one ic to reduces ripple current in the 420v storage capacitor between the pfc and pwm sections. ? low total harmonic distortion, thd and power factor approaches 1.0. ? average current, continuous or discontinuous boost leading edge pfc. ? pwm configurable for current mode or feed-forward voltage mode operation. ? current fed gain modulator for improved noise immunity. ? gain modulator is a constant maximum power limiter. ? brown-out control, over-voltage protection, uvlo, and soft start, and reference ok. ? pwm short circuit protection ? power fold back protection ? green mode pwm for less no load consumption.
CM6802A/b/ah/bh (dynamic soft pfc/green pwm) http://www.championmicro.com.tw epa/80++ zvs-like pfc/pwm combo controller design for high efficient power supply at both full load and light load 2012/05/10 rev. 1.5 champion microelectronic corporation 2 applications pin configuration ? epa/80++ related power supply ? desktop pc power supply ? internet server power supply ? lcd power supply ? pdp power supply ? ipc power supply ? ups ? battery charger ? dc motor power supply ? monitor power supply ? telecom system power supply ? distributed power sop-16 (s16) / pdip-16 (p16) 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 i eao i ac i sense v rms ss v dc r amp1 r amp2 v eao v fb v ref v cc pfc out pwm out gnd dc i limit pin description operating voltage pin no. symbol description min. typ. max. unit 1 i eao pfc transconductance current error amplifier output (gmi). 0 vref v 2 i ac iac has 2 functions: 1. pfc gain modulator reference input. 2. at start up, iac is connec ted to vcc and it helps to reduce the startup time and it helps to reduce the no load consumption. typical ra c resistor is about 6 mega ohm to sense the line. 0 100 ua 3 i sense pfc current sense: for both gain modulator and pfc ilimit comparator. -1.2 0.7 v 4 v rms line input sense pin and also, it is the brown out sense pin. 0 vcc+0.3 v 5 ss soft start capacitor pin; can use it to on/off the boost follower function; it is pulled down by 300 ohm internal resistor when dcilimit reach 1v; the power is limited during the pwm brown out. 0 10 v CM6802A/b/ah/bh (dynamic soft pfc/green pwm) http://www.championmicro.com.tw epa/80++ zvs-like pfc/pwm combo controller design for high efficient power supply at both full load and light load 2012/05/10 rev. 1.5 champion microelectronic corporation 3 6 v dc dc to dc pwm voltage feedback input. 0 10 v 7 ramp 1 (rtct) oscillator timing node; timing set by rt and ct 0.8 4 v 8 ramp 2 (pwm ramp) in current mode, this pin functions as the current sense input; when in voltage mode, it is the feed-forward sense input from pfc output 380v (feed forward ramp). 0 v dc max -1.8 v 9 dc i limit pwm current limit comparator input 0 1 v 10 gnd ground 11 pwm out pwm driver output 0 vcc v 12 pfc out pfc driver output 0 vcc v 13 v cc positive supply for CM6802A/b/ah/bh 10 15 18 v 14 vref maximum 4ma buffered output for the internal 7.5v reference when vcc=14v 7.5 v 15 v fb pfc transconductance voltag e error amplifier input 0 2.5 3 v 16 veao pfc transconductance voltage error amplifier output (gmv) 0 6 v ordering information part number temperature range package CM6802A/b/ah/bhgip* -40 to 125 16-pin pdip (p16) CM6802A/b/ah/bhgis* -40 to 125 16-pin narrow sop (s16) CM6802A/b/ah/bhgistr* -40 to 125 16-pin narrow sop (s16) CM6802A/b/ah/bhxip* -40 to 125 16-pin pdip (p16) CM6802A/b/ah/bhxis* -40 to 125 16-pin narrow sop (s16) CM6802A/b/ah/bhxistr* -40 to 125 16-pin narrow sop (s16) *note: g : suffix for pb free product tr : package is typing reel x : suffix for halogen free product CM6802A/b/ah/bh (dynamic soft pfc/green pwm) http://www.championmicro.com.tw epa/80++ zvs-like pfc/pwm combo controller design for high efficient power supply at both full load and light load 2012/05/10 rev. 1.5 champion microelectronic corporation 4 simplified block diagram (CM6802A/b/ah/bh) vfb vfb 15 zener 17v npfc isense 3 veao mnpfc s r q q vfb 0.5v + - pfc tri-fault iac 2 pfc out 12 vfb -1.0v ppwm zener 17v 2.36v ramp1 7 s r q q vref 14 5 ref-ok vrms 4 reference 7.5v vcc + - pfc cmp rmul 380v-ok + - . ramp2 8 isense ieao 1 pwm out 11 + - pfc ilimit uvlo 1.0v + - green pfc gnd 10 0.3v gmv - + . veao 16 vcc vcc vcc 1.8v green pwm 10ua 300 s r q q s + - dc ilimit vdc 6 pfc ovp + - . vcc 13 2.5v mppfc gmi + - . vref+2.5v 2.85v pfcclk pwmclk . . pfc ramp sw spst + - - pfc modulator gain 380-ok dc ilimit 9 rmul zener 16.5v 1 2 absolute maximum ratings absolute maximum ratings are those values beyo nd which the device could be permanently damaged. parameter min. max. units v cc 18 v ieao 0 vref+0.3 v i sense voltage -5 0.7 v gnd ? 0.3 vcc + 0.3 v gnd ? 0.3 vcc + 0.3 v pfc out pwmout voltage on any other pin gnd ? 0.3 vcc + 0.3 v i ref 5 ma i ac input current 1 ma peak pfc out current, source or sink 0.5 a peak pwm out current, source or sink 0.5 a pfc out, pwm out energy per cycle 1.5 j junction temperature 150 storage temperature range -65 150 operating temperature range -40 125 lead temperature (soldering, 10 sec) 260 thermal resistance ( ja ) plastic dip plastic soic 80 105 /w /w power dissipation (pd) t a <5 0 800 mw esd capability, hbm model 5.5 kv esd capability, cdm model 1250 v CM6802A/b/ah/bh (dynamic soft pfc/green pwm) http://www.championmicro.com.tw epa/80++ zvs-like pfc/pwm combo controller design for high efficient power supply at both full load and light load 2012/05/10 rev. 1.5 champion microelectronic corporation 5 electrical characteristics: unless otherwise stated, these specifications apply vcc=+14v, r t = 7.75k k ? , c t = 1000pf, t a =operating temperature range (note 1) CM6802A/b/ah/bh symbol parameter test conditions min. typ. max. unit pfc brown out vrms threshold high room temperature=2 5 1.19 1.25 1.32 v vrms threshold low room temperature=2 5 0.97 1.05 1.13 v hysteresis 170 216 260 mv ac high line sweep vrms pin 2.15 2.25 2.35 v ac low line sweep vrms pin 1.85 2 2.12 v hysteresis 200 300 mv voltage error amplifier (g mv ) input voltage range 0 3 v transconductance v noninv = v inv , veao = 2.25v @ t=25 53 69 88 CM6802A/b 1.9 2 2.1 v feedback reference voltage (low) CM6802Ah/bh ss>vref and veao < 1.75v and vrms < 2v 2.19 2.26 2.33 v input bias current note 2 -1.0 -0.05 current error amplifier (g mi ) input voltage range (is ense pin) -1.2 0.7 v transconductance v noninv = v inv , ieao = 1.5v @ t=25 53 69 85 CM6802A/b/ah/bh (dynamic soft pfc/green pwm) http://www.championmicro.com.tw epa/80++ zvs-like pfc/pwm combo controller design for high efficient power supply at both full load and light load 2012/05/10 rev. 1.5 champion microelectronic corporation 6 electrical characteristics: (conti.) unless otherwise stated, these specifications apply vcc=+14v, r t = 7.75 k ? , c t = 1000pf, t a =operating temperature range (note 1) CM6802A/b/ah/bh symbol parameter test conditions min. typ. max. unit sink current i sense = -0.5v, ieao = 1.5v -42 -33 -30 pfc ovp comparator threshold voltage 2.70 2.85 3.0 v hysteresis 200 300 mv pfc green power detect comparator veao threshold voltage 0.15 0.25 0.35 v tri-fault detect fault detect high 2.70 2.85 3.0 v time to fault detect high v fb =v fault detect low to v fb =open, 470pf from v fb to gnd 2 4 ms fault detect low 0.4 0.5 0.6 v pfc i limit comparator threshold voltage -1.10 -1.00 -0.90 v (pfci limit ? gain modulator output) 100 200 mv delay to output (note 4) overdrive voltage = -100mv 700 ns dc i limit comparator threshold voltage 0.92 1.0 1.08 v delay to output (note 4) overdrive voltage = 100mv 700 ns dc to dc pwm brown out comparator ok threshold voltage 2.20 2.36 2.52 v hysteresis 900 950 1000 mv CM6802A/b/ah/bh (dynamic soft pfc/green pwm) http://www.championmicro.com.tw epa/80++ zvs-like pfc/pwm combo controller design for high efficient power supply at both full load and light load 2012/05/10 rev. 1.5 champion microelectronic corporation 7 electrical characteristics: (conti.) unless otherwise stated, these specifications apply vcc=+14v, r t = 7.75 k ? , c t = 1000pf, t a =operating temperature range (note 1) CM6802A/b/ah/bh symbol parameter test conditions min. typ. max. unit gain modulator gain1 (note 3) i ac = 20 ss CM6802A/b/ah/bh (dynamic soft pfc/green pwm) http://www.championmicro.com.tw epa/80++ zvs-like pfc/pwm combo controller design for high efficient power supply at both full load and light load 2012/05/10 rev. 1.5 champion microelectronic corporation 9 typical performanc e characteristic: pfc soft diagram : dynamic soft pfc performance @ vin=110 vac ch1 is 380v bulk cap voltage which is 100v/div. ch3 is input line current which is 1a/div. input line voltage (110 vac) was turned off for 40ms before r eaching pwm brownout which is 209vdc. when the bulk cap voltage go es below 209v, the system will reset the pwm soft start. the result of the CM6802A/b/ah/bh input line current has a clean off and softly on even the system does not reset pwm soft-start. dynamic soft pfc performance @ vin=220 vac ch1 is 380v bulk cap voltage which is 100v/div. ch3 is input line current which is 1a/div. input line voltage (220 vac) was turned off for 40ms before reachi ng pwm brownout which is 209vdc when bulk cap voltage drops b elow 209v. when the bulk cap voltage goes below 209v, the system will rese t the pwm soft start. the result of the CM6802A/b/ah/bh in put line current has a clean off and softly on even the system does not re set itself. the first peak current at the beginning of the on time is the inrush current. CM6802A/b/ah/bh (dynamic soft pfc/green pwm) http://www.championmicro.com.tw epa/80++ zvs-like pfc/pwm combo controller design for high efficient power supply at both full load and light load 2012/05/10 rev. 1.5 champion microelectronic corporation 10 turn on timing : output 50% and 100% load turn on waveform at 110vac ch1 is 380v bulk cap voltage which is 100v/div. ch2 is vcc,ch3 is ss(soft start pin),ch4 is vo(12v). output 10% and 20% load turn on waveform at 230vac output 50% and 100% load turn on waveform at 230vac ch1 is 380v bulk cap voltage which is 100v/div. ch1 is 380v bulk cap voltage which is 100v/div. ch2 is vcc,ch3 is ss(soft start pin),ch4 is vo(12v) ch2 is vcc,ch3 is ss(soft start pin),ch4 is vo(12v) dynamic load: output step load 10% to 100% load at 90vac output step 100% load to 10% load at 90vac ch1 is 380v bulk cap voltage which is 100v/div. ch1 is 380v bulk cap voltage which is 100v/div. ch2 is vcc,ch3 is ss(soft start pin),ch4 is vo(12v) ch2 is vcc,ch3 is ss(soft start pin),ch4 is vo(12v) CM6802A/b/ah/bh (dynamic soft pfc/green pwm) http://www.championmicro.com.tw epa/80++ zvs-like pfc/pwm combo controller design for high efficient power supply at both full load and light load 2012/05/10 rev. 1.5 champion microelectronic corporation 11 output step load 10% to 100% load at 230vac output step 100% load to 10% load at 230vac ch1 is 380v bulk cap voltage which is 100v/div. ch1 is 380v bulk cap voltage which is 100v/div. ch2 is vcc,ch3 is ss(soft start pin),ch4 is vo(12v) ch2 is vcc,ch3 is ss(soft start pin),ch4 is vo(12v) ac power cycling : 90vac turn on 500ms turn off 100ms at 10%load ch2 is ac input voltage which is 100v/div. ch3 is pfc stage mosfet drain current(zoom out) ch3 is pfc stage mosfet drain current, ch4 is vo(12v) 90vac turn on 500ms turn off 100ms at 100%load ch2 is ac input voltage which is 100v/div. c h3 is pfc stage mosfet drain current(zoom out) ch3 is pfc stage mosfet drain current, ch4 is vo(12v) CM6802A/b/ah/bh (dynamic soft pfc/green pwm) http://www.championmicro.com.tw epa/80++ zvs-like pfc/pwm combo controller design for high efficient power supply at both full load and light load 2012/05/10 rev. 1.5 champion microelectronic corporation 12 90vac turn on 500ms turn off 10ms at 10%load ch2 is ac input voltage which is 100v/div. ch3 is pfc stage mosfet drain current (zoom out) ch3 is pfc stage mosfet drain current, ch4 is vo (12v) 90vac turn on 500ms turn off 10ms at 100%load ch2 is ac input voltage which is 100v/div. ch3 is pfc stage mosfet drain current (zoom out) ch3 is pfc stage mosfet drain current, ch4 is vo (12v) 230vac turn on 500ms turn off 100ms at 10%load ch2 is ac input voltage which is 100v/div. ch3 is pfc stage mosfet drain current (zoom out) ch3 is pfc stage mosfet drain current, ch4 is vo (12v) CM6802A/b/ah/bh (dynamic soft pfc/green pwm) http://www.championmicro.com.tw epa/80++ zvs-like pfc/pwm combo controller design for high efficient power supply at both full load and light load 2012/05/10 rev. 1.5 champion microelectronic corporation 13 230vac turn on 500ms turn off 100ms at 100%load ch2 is ac input voltage which is 100v/div. ch3 is pfc stage mosfet drain current (zoom out) ch3 is pfc stage mosfet drain current, ch4 is vo (12v) 230vac turn on 500ms turn off 10ms at 10%load ch2 is ac input voltage which is 100v/div. c h3 is pfc stage mosfet drain current (zoom out) ch3 is pfc stage mosfet drain current, ch4 is vo (12v) 230vac turn on 500ms turn off 10ms at 100%load ch2 is ac input voltage which is 100v/div. ch3 is pfc stage mosfet drain current (zoom out) ch3 is pfc stage mosfet drain current, ch4 is vo (12v) CM6802A/b/ah/bh (dynamic soft pfc/green pwm) http://www.championmicro.com.tw epa/80++ zvs-like pfc/pwm combo controller design for high efficient power supply at both full load and light load 2012/05/10 rev. 1.5 champion microelectronic corporation 14 getting start: to start evaluating CM6802A/ b/ah/bh from the exiting cm6800 or ml4800 board, 6 things need to be taken care before doing the fine tune: 1.) change rac resistor (on pin 2, iac) from the old value to a higher resistor value between 4.7 mega ohms to 8 mega ohms. 2.) change rtct pin (pin 7) from the existing value to rt=7.0k ohm and ct=1000pf to have fpfc=55 khz, fpwm=55khz, frtct=220khz for CM6802A/ah and fpfc=55 khz, fpwm=110khz, frtct=220khz for cm6802b/bh. 3.) adjust all high voltage resistor around 5 mega ohm or higher. 4.) vrms pin (pin 4) needs to be 1.125v at vin=85vac for universal input application from line input from 85vac to 270vac. both poles for the vrms of the CM6802A/b/ah/bh needs to substantially slow than cm6800 about 5 to 10 times. 5.) at full load, the average veao needs to around 4.5v and the ripple on the veao needs to be less than 250mv. 6.) soft start pin (pin 5), t he soft start current has been reduced from cm6800?s 20ua to CM6802A/b/ah/bh?s 10ua.soft start capacitor can be reduced to 1/2 from your original cm6800 capacitor. functional description CM6802A/b/ah/bh is designed for high efficient power supply for both full load and light load. it is a popular epa/80++ pfc-pwm power supply controller. the CM6802A/b/ah/bh consists of an average current controlled, continuous/discontinuous boost power factor correction (pfc) front end and a synchronized pulse width modulator (pwm) back end. the pwm can be used in either current or voltage mode. in vo ltage mode, feed-forward from the pfc output bus can be used to improve the pwm?s line regulation. in either mode, the pwm stage uses conventional trailing edge duty cycle modulation, while the pfc uses leading edge modulation. this patented leading/trailing edge modulation technique results in a higher usable pfc error amplifier bandwidth, and can significantly reduce the size of the pfc dc buss capacitor. the synchronized of the pwm with the pfc simplifies the pwm compensation due to the controlled ripple on the pfc output capacitor (the pwm input capacitor). in addition to power factor correction, a number of protection features hav e been built into the CM6802A/b/ah/bh. these include soft-start, pfc over-voltage protection, peak current limiting, brownout protection, duty cycle limiting, and under-voltage lockout. power factor correction power factor correction makes a nonlinear load look like a resistive load to the ac line. fo r a resistor, the current drawn from the line is in phase with and proportional to the line voltage, so the power factor is unity (one). a common class of nonlinear load is the input of most power supplies, which use a bridge rectifier and capacitive input f ilter fed from the line. the peak-charging effect, which occurs on the input filter capacitor in these supplies, causes brief high- amplitude pulses of current to flow from the power line, rather than a sinusoidal current in phase with the line voltage. such supplies present a power factor to the line of less than one (i.e. they cause significant current harmonics of the power li ne frequency to appear at their input). if the input current drawn by such a supply (or any other nonlinear load) can be made to follow the input voltage in instantaneous amplitude, it will appear resistive to the ac line and a unity power factor will be achieved. to hold the input current draw of a device drawing power from the ac line in phase with and propor tional to the input voltage, a way must be found to prevent t hat device from loading the line except in proportion to the inst antaneous line voltage. the pfc section of the CM6802A/b/a h/bh uses a boost-mode dc-dc converter to accomplish this. the input to the converter is the full wave rectified ac line voltage. no bulk filtering is applied following the bridge rectifier, so the input voltage to the boost converter ranges (at twice line frequency) from zero volts to the peak value of the ac input and back to zero. by forcing the boost converter to meet two simultaneous conditions, it is possible to ensure that the current drawn from the power line is proportional to the input line volt age. one of these conditions is that the output volt age of the boost converter must be set higher than the peak value of the line voltage. a commonly used value is 385vdc, to allow for a high line of 270vac rms . the other condition is that the current dr awn from the line at any given instant must be proportional to the line voltage. establishing a suitable voltage control loop for the converter, which in turn drives a current error amplifie r and switching output driver satisfies the first of these requirements. the second requirement is met by using the rectified ac line voltage to modulate the output of the voltage c ontrol loop. such modulation causes the current error amplifier to command a power stage current that varies directly with the input volt age. in order to prevent ripple, which will necessarily appear at the output of boost circuit (typically about 10vac on a 385v dc level); from introducing distortion back through the voltage error amplifier, the bandwidth of the voltage loop is deliberately kept low. a final refinement is to adjust the overall gain of the pfc such to be proportional to 1/(vin x vin), which linearizes the transfer function of the system as the ac input to voltage varies. since the boost converter topology in the CM6802A/b/ah/bh pfc is of the current-averaging type, no slope compensation is required. more exactly, the output current of the gain modulator is given by: CM6802A/b/ah/bh (dynamic soft pfc/green pwm) http://www.championmicro.com.tw epa/80++ zvs-like pfc/pwm combo controller design for high efficient power supply at both full load and light load 2012/05/10 rev. 1.5 champion microelectronic corporation 15 dynamic soft pfc (patent pending) besides all the goodies from cm6800a, dynamic soft pfc is the main feature of CM6802A/b/ah/bh. dynamic soft pfc is to improve the efficiency, to reduce power device stress, to ease emi, and to ease the monot onic output design while it has the more protection such as the short circuit with power fold back protection. its unique sequential control maximizes the performance and the protec tions among steady state, transient and the power on/off conditions. pfc section: gain modulator figure 1 shows a block diagram of the pfc section of the CM6802A/b/ah/bh. the gain modulator is the heart of the pfc, as it is this circuit block which controls the response of the current loop to line voltage waveform and frequency, rms line voltage, and pfc output volt ages. there are three inputs to the gain modulator. these are: 1. a current representing the instantaneous input voltage (amplitude and wave-shape) to the pfc. the rectified ac input sine wave is converted to a proportional current via a resistor and is then fed into the gain modulator at i ac . sampling current in this way minimizes ground noise, as is required in high power switching power conversion environments. the gain modulator responds linearly to this current. 2. a voltage proportional to the long-term rms ac line voltage, derived from the rect ified line voltage after scaling and filtering. this signal is presented to the gain modulator at vrms. the gain modulator?s output is inversely proportional to v rms 2 (except at unusually low values of v rms where special gain contouring takes over, to limit power dissipation of the circuit components under heavy brownout conditions). the relationship between v rms and gain is called k, and is illustrated in the typical performance characteristics. 3. the output of the voltage er ror amplifier, veao. the gain modulator responds linearly to variations in this voltage. the output of the gain modulator is a current signal, in the form of a full wave rectified sinusoid at twice the line frequency. this current is applied to the virtual-ground (negative) input of t he current error amplifier. in this way the gain modulator forms the reference for the current error loop, and ultimately controls the inst antaneous current draw of the pfc from the power line. the gen eral formula of the output of the gain modulator is: i mul = 2 rms ac v 0.7v) - veao i ( x constant (1) gain=imul/iac k=gain/(veao-0.7v) i mul = k x (veao ? 0.7v) x i ac where k is in units of [v -1 ] note that the output current of the gain modulator is limited around 100 ac mul ac offset sense i i i i i = ? = gain selecting r ac for iac pin iac pin is the input of the gain modulator. iac also is a current mirror input and it requires current input. by selecting a proper resistor r ac , it will provide a good sine wave current derived from the line voltage and it al so helps program the maximum input power and minimum input line voltage. r ac =vin min peak x 39.09k. for example, if the minimum line voltage is 85vac, the r ac =85 x 1.414 x 39.09k = 4.7 mega ohm. CM6802A/b/ah/bh (dynamic soft pfc/green pwm) http://www.championmicro.com.tw epa/80++ zvs-like pfc/pwm combo controller design for high efficient power supply at both full load and light load 2012/05/10 rev. 1.5 champion microelectronic corporation 16 vrms description: vrms pin is designed for the following functions: 1. vrms is used to detect the ac brown out (also, we can call it pfc brown out.). when vrms is less than 1.0 v +/-5%, pfcout will be turned off and veao will be softly discharged toward 0 volt. when vrms is greater than 1.25v +/-5%, pfcout is enabled and veao is released. 2. vrms also is used to deter mine if the ac line is high line or it is low line. if vrms is above 2.5v +/- 5%, ic will recognize it is high line the. if vrms is below 2.25v +/- 5%, it is low line. between 2v <=~ vrms <=~ 2.25v, it is the hysteresis. 3. at high line and light load, 380v to 304v (vfb threshold moves from 2.5v to 2v) is prohibited of CM6802A/b ; 380v to 342v (vfb threshold moves from 2.5v to 2.25v) is prohibited of CM6802Ah/bh. at low line and light load, 380v to 304v (vfb threshold moves from 2.5v to 2v) is enable of CM6802A/b ; 380v to 342v (vfb threshold moves from 2.5v to 2.25v) is enable of CM6802Ah/bh. it provides zvs-like performance. current error amplifier, ieao the current error amplifier?s output controls the pfc duty cycle to keep the average current through the boost inductor a linear function of the line volt age. at the inverting input to the current error amplifier, the output current of the gain modulator is summed with a current which results from a negative voltage being impressed upon the i sense pin. the negative voltage on i sense represents the sum of all currents flowing in the pfc circuit, and is typically derived from a current sense resistor in series with the negative terminal of the input bridge rectifier. in higher power applications, two current transformers are sometimes used, one to monitor the if of the boost diode. as stated above, the inverting input of the current error amplifier is a virtual ground. given this fact, and the arrangement of the duty cycle modulator polariti es internal to the pfc, an increase in positive current from the gain modulator will cause the output stage to incr ease its duty cycle until the voltage on i sense is adequately negative to cancel this increased current. similarly, if the gain modulator?s output decreases, the output duty cycle will decrease, to achieve a less negative voltage on the i sense pin. error amplifier compensation the pwm loading of the pfc can be modeled as a negative resistor; an increase in input voltage to the pwm causes a decrease in the input current. this response dictates the proper compensation of the two transconductance error amplifiers. figure 2 shows the types of compensation networks most commonly used for the voltage and current error amplifiers, along with their respective return points. the current loop compensation is returned to v ref to produce a soft-start characteristic on the pfc: as the reference voltage comes up from zero volts, it creates a differentiated voltage on i eao which prevents the pfc from immediately demanding a full duty cycle on its boost converter. pfc brown out (pfc brown out comparator) the pfc brown out comparator monitors the vrms (pin 4) voltage and inhibits the pfc and pfc error amplifier output, veao is pulled down during the vrms is lower than threshold. if this voltage on vrms is less than its nominal 1.25v. once this voltage reaches 1.25v, which corre sponds to the pfc input rms is around 88vac. it is a hyster esis comparator and its lower threshold is 1v. after pfc brow n out conditions are removed, the system will initiate the start up sequence with the proper soft start rate set by ss (pin 5). cycle-by-cycle current limiter and selecting r sense the i sense pin, as well as being a part of the current feedback loop, is a direct input to the cyc le-by-cycle current limiter for the pfc section. should the input vo ltage at this pin ever be more negative than ?1v, the output of the pfc will be disabled until the protection flip-flop is reset by the clock pulse at the start of the next pfc power cycle. r s is the sensing resistor of the pfc boost converter. during the steady state, li ne input current x r sense = i mul x 7.75k. since the maximum output voltage of the gain modulator is i mul max x 7.75 kP 0.8v during the steady state, r sense x line input current will be limited below 0.8v as well. when veao reaches maximum veao which is 6v, isens e can reach 0.8v. at 100% load, veao should be around 4.5v and isense average peak is 0.6v. it will provide the optimal dynamic response + tolerance of the components. therefore, to choose r sense , we use the following equation: r sense + r parasitic =0.6v x vinpeak / (2 x line input power) for example, if the minimum input voltage is 80vac, and the maximum input rms power is 200watt, r sense + r parasitic = (0.6v x 80v x 1.414) / (2 x 200) = 0.169 ohm. the designer needs to consider the parasitic resistance and the margin of the power supply and dynamic response. assume r parasitic = 30 mohm, r sense = 139 mohm. pfc ovp in the CM6802A/b/ah/bh, pfc ovp comparator serves to protect the power circuit from being subjected to excessive voltages if the load should suddenly change. a resistor divider from the high voltage dc output of the pfc is fed to vfb. when the voltage on vfb exceeds ~ 2. 85v, the pfc output driver is shut down. the pwm section will continue to operate. the ovp comparator has 250mv of hysteresis, and the pfc will not restart until the voltage at vfb drops below ~ 2.55v. the vfb power components and the CM6802A /b/ah/bh are within their safe operating voltages, but not so low as to interfere with the boost voltage regulation loop. CM6802A/b/ah/bh (dynamic soft pfc/green pwm) http://www.championmicro.com.tw epa/80++ zvs-like pfc/pwm combo controller design for high efficient power supply at both full load and light load 2012/05/10 rev. 1.5 champion microelectronic corporation 17 pfc voltage loop there are two major concerns when compensating the voltage loop error amplifier, v eao ; stability and transient response. optimizing interaction between transient response and stability requires that the error amplifier?s open-loop crossover frequency should be 1/2 that of the line frequency, or 23hz for a 47hz line (lowest anticipated international power frequency). deviate from its 2.5v (nominal) value. if this happens, the transconductance of the voltage error amplifier, gmv will increase significantly, as shown in the typical performance characteristics. this raises the gain-bandwidth product of the voltage loop, resulting in a much more rapid voltage loop response to such perturbations than would occur with a conventional linear gain characteristics. the voltage loop gain (s) cv v dc eao 2 outdc in fb eao out fb eao out z * gm * c * s * v * v 2.5v * p v v * v v * v v = z cv : compensation net work for the voltage loop gm v : transconductance of veao p in : average pfc input power v outdc : pfc boost output voltage; typical designed value is 380v. c dc : pfc boost output capacitor pfc current loop the current transcondutanc e amplifier, gmi, i eao compensation is similar to that of the voltage error amplifier, v eao with exception of the choice of crossover frequency. the crossover frequency of the current amplifier should be at least 10 times that of the voltage amplifier, to prevent interaction with the voltage loop. it should also be limited to less than 1/6th that of the switching frequency, e.g. 8. 33khz for a 50khz switching frequency. the current loop gain (s) ci i s outdc sense eao eao off off isense z * gm * 2.5v * l * s r * v i i * i d * d v = z ci : compensation net work for the current loop gm i : transconductance of ieao v outdc : pfc boost output voltage; typical designed value is 380v and we use the worst condition to calculate the z ci r sense : the sensing resistor of the boost converter 2.5v: the amplitude of the pfc leading edge modulation ramp(typical) l: the boost inductor the gain vs. input voltage of the CM6802A/b/ah/bh?s voltage error amplifier, v eao has a specially shaped non-linearity such that under steady-state operating conditions the transconductance of the error am plifier, gmv is at a local minimum. rapid perturbation in line or load conditions will cause the input to the voltage error amplifier (v fb ) to i sense filter, the rc filter between r sense and i sense : there are 2 purposes to add a filter at i sense pin: 1.) protection: during start up or in rush current conditions, it will have a large voltage cross rs wh ich is the sensing resistor of the pfc boost converter. it requires the i sense filter to attenuate the energy. 2.) to reduce l, the boost inductor: the i sense filter to reduce l, the boost inductor: the i sense filter also can reduce the boost inductor value since the i sense filter behaves like an integrator before going i sense which is the input of the current error amplifier, ieao. the i sense filter is a rc filter. t he resistor value of the i sense filter is between 100 ohm and 50 ohm because i offset x the resistor can generate an offset voltage of ieao. by selecting r filter equal to 50 ohm will keep the offs et of the ieao less than 5mv. usually, we design the pole of i sense filter at fpfc/6=8.33khz, one sixth of the pfc switching frequency. therefore, the boost inductor c an be reduced 6 times without disturbing the stability. theref ore, the capacitor of the i sense filter, c filter , will be around 381nf. CM6802A/b/ah/bh (dynamic soft pfc/green pwm) http://www.championmicro.com.tw epa/80++ zvs-like pfc/pwm combo controller design for high efficient power supply at both full load and light load 2012/05/10 rev. 1.5 champion microelectronic corporation 18 pfc ieao 1 0.3v vfb 15 ramp1 7 vcc pfc ovp + - . isense -1.0v rmul vrms 4 pfc out 12 mppfc 2.5v gmv - + . s r q q + - pfc ilimit zener 17v veao + - green pfc modulator gain + - pfc cmp vref 14 2.85v vcc pfc ramp isense 3 pfcclk . veao 16 vfb gmi + - . 0.5v mnpfc s r q q rmul zener 16.5v 1 2 + - pfc tri-fault reference 7.5v vfb vcc 13 iac 2 figure 1. pfc section block diagram CM6802A/b/ah/bh (dynamic soft pfc/green pwm) http://www.championmicro.com.tw epa/80++ zvs-like pfc/pwm combo controller design for high efficient power supply at both full load and light load 2012/05/10 rev. 1.5 champion microelectronic corporation 19 oscillator (ramp1, or called rtct) in CM6802A/ah, frtct=4xfpwm=4xfpfc frtct=200khz, fpwm=50khz and fpfc=50khz when veao=0v, it provides the best performance in the pc application. in cm6802b/bh, frtct=2xfpwm=4xfpfc frtct=200khz, fpwm=100khz and fpfc=50khz when veao=0v, it provides the best performance in the pc application. the oscillator frequency, frtct is the similar formula in cm6800: frtct = deadtime ramp t t 1 + the dead time of the oscillator is derived from the following equation: t ramp = c t x r t x in 3.75 v 1.25 v ref ref ? ? at vref = 7.5v: t ramp = c t x r t x 0.51 the dead time of the oscillator may be determined using: t deadtime = 4.216ma 2.5v x c t = 593 x c t the dead time is so small (t ramp >> t deadtime ) that the operating frequency can typically be approximately by: frtct = ramp t 1 ct should be greater than 470pf. let us use 1000pf solving for r t yields 7.75k. selecting standard components values, c t = 1000pf, and r t = 7.75k ? the dead time of the oscillator determined two things: 1.) pfc minimum off time which is the dead time 2.) pwm skipping reference duty cycle: when the pwm duty cycle is less than the dead time, the next cycle will be skipped and it reduces no load consumption in some applications. pwm section pulse width modulator the pwm section of the CM6802A/b/ah/bh is straightforward, but there are several points which should be noted. foremost amo ng these is its inherent synchronization to the pfc se ction of the device, from which it also derives its basic timing. the pwm is capable of current-mode or voltage-mode operation. in current-mode applications, the pwm ramp (ramp2) is usually derived directly from a current sensing resistor or current transformer in the primary of t he output stage, and is thereby representative of the current fl owing in the converter?s output stage. dci limit , which provides cycle-by-cycle current limiting, is typically connected to ramp2 in such applications. for voltage-mode, operation or certain specialized applications, ramp2 can be connected to a separate rc timing network to generate a voltage ramp against which v dc will be compared. under these conditions, the use of voltage feed-forward from the pfc buss can assist in line regulation accuracy and response. as in current mode operation, the dc i limit input is used for output stage over-current protection. no voltage error amplifier is included in the pwm stage of the CM6802A/b/ah/bh, as this function is generally performed on the output side of the pwm?s isolat ion boundary. to facilitate the design of opto-coupler feedback circ uitry, an offset has been built into the pwm?s ramp2 input which allows v dc to command a zero percent duty cycle for input voltages below around 1.8v. pwm current limit (dcilimit) the dc i limit pin is a direct input to the cycle-by-cycle current limiter for the pwm section. should the input voltage at this pin ever exceed 1v, the output flip-fl op is reset by the clock pulse at the start of the next pwm power cy cle. beside, the cycle-by-cycle current, when the dc ilimit trigger ed the cycle-by-cycle current. it will limit pwm duty cycle m ode. therefore, the power dissipation will be reduced during the dead short condition. when dcilimit pin is connected with ramp2 pin, the CM6802A/b/ah/bh?s pwm secti on becomes a current mode pwm controller. sometimes, network between dcilimit and ramp2 is a resistor divider so the dcilimit?s 1v threshold can be amplified to 1.5v or higher for easy layout purpose. pwm brown out (380v-ok comparator) the 380v-ok comparator monito rs the dc output of the pfc and inhibits the pwm if this voltage on v fb is less than its nominal 2.36v. once this voltage reaches 2.36v, which corresponds to the pfc output capacitor being char ged to its rated boost voltage, the soft-start begins. it is a hyster esis comparator and its lower threshold is 1.35v. CM6802A/b/ah/bh (dynamic soft pfc/green pwm) http://www.championmicro.com.tw epa/80++ zvs-like pfc/pwm combo controller design for high efficient power supply at both full load and light load 2012/05/10 rev. 1.5 champion microelectronic corporation 20 pwm control (ramp2) when the pwm section is used in current mode, ramp2 is generally used as the sampling point for a voltage representing the current on t he primary of the pwm?s output transformer, derived either by a current sensing resistor or a current transformer. in voltage m ode, it is the input for a ramp voltage generated by a second set of timing components (r ramp2 , c ramp2 ),that will have a minimum value of zero volts and should have a peak value of approximately 5v. in voltage mode operation, feed-forward from the pfc output buss is an excellent way to derive the timing ramp for the pwm stage. soft start (ss) start-up of the pwm is contro lled by the selection of the external capacitor at ss. a current source of 10 a supplies the charging current for the capacitor, and start-up of the pwm begins at ss~1.4v. start-up delay can be programmed by the following equation: c ss = t delay x 1.8v a 10 where c ss is the required soft start capacitance, and the t dealy is the desired start-up delay. it is important that the time constant of t he pwm soft-start allow the pfc time to generate sufficient output power for the pwm section. the pwm start-up delay should be at least 5ms. solving for the minimum value of c ss : c ss = 5ms x 1.8v a 10 P 27nf caution should be exercised when using this minimum soft start capacitance value because premature charging of the ss capacitor and activation of t he pwm section can result if vfb is in the hysteresis band of the 380v-ok comparator at start-up. the magnitude of v fb at start-up is related both to line voltage and nominal pfc out put voltage. typically, a 0.05 f soft start capacitor will allow time for v fb and pfc out to reach their nominal values prior to activation of the pwm section at line voltages between 90vrms and 265vrms. generating v cc after turning on CM6802A/b/ah/bh at 13v, the operating voltage can vary from 10v to 17.9v. that?s the two ways to generate vcc. one way is to use auxiliary power supply around 15v, and the other way is to use bootstrap winding to self-bias CM6802A/b/ah/bh system. the bootstrap winding can be either taped from pfc boost choke or from the transformer of the dc to dc stage. the ratio of winding transformer for the bootstrap should be set between 18v and 15v. a filter network is recommended between vcc (pin 13) and bootstrap winding. the resistor of the filter can be set as following. r filter x i vcc ~ 2v, i vcc = i op + (q pfcfet + q pwmfet ) x fsw i op = 3ma (typ.) if anything goes wrong, and vcc goes beyond 19.4v, the pfc gate (pin 12) drive goes low and the pwm gate drive (pin 11) remains function. the resistor?s value must be chosen to meet the operating current requirement of the CM6802A/b/ah/bh itself (5ma, ma x.) plus the current required by the two gate driver outputs. example: with a wanting voltage called, v bias ,of 18v, a vcc of 15v and the CM6802A/b/ah/bh driving a total gate charge of 90nc at 100khz (e.g. 1 irf840 mosfet and 2 irf820 mosfet), the gate driver current required is: i gatedrive = 100khz x 90nc = 9ma r bias = g cc cc bias i i v v + ? + ? ? the CM6802A/b/ah/bh should be locally bypassed with a 1.0 f is also required across the part, both for filtering and as part of the start-up bootstrap circuitry. leading/trailing modulation conventional pulse width modulation (pwm) techniques employ trailing edge modulation in which the switch will turn on right after the trailing edge of the system clock. the error amplifier output is then compared with the modulating ramp up. the effective duty cycle of the trailing edge modulation is determined during the on time of the switch. figure 4 shows a typical trailing edge control scheme. CM6802A/b/ah/bh (dynamic soft pfc/green pwm) http://www.championmicro.com.tw epa/80++ zvs-like pfc/pwm combo controller design for high efficient power supply at both full load and light load 2012/05/10 rev. 1.5 champion microelectronic corporation 21 in case of leading edge modulation, the switch is turned off right at the leading edge of the system clock. when the modulating ramp reaches the level of the error amplifier output voltage, the switch will be turned on. the effective duty-cycle of the leading edge modulation is determined during off time of the switch. figure 5 shows a leading edge control scheme. one of the advantages of this control technique is that it required only one system clock. switch 1(sw1) turns off and switch 2 (sw2) turns on at the same instant to minimize the momentary ?no-load? period, t hus lowering ripple voltage generated by the switching acti on. with such synchronized switching, the ripple voltage of the first stage is reduced. calculation and evaluation have shown that the 120hz component of the pfc?s output ripple voltage can be reduced by as much as 30% using this method. CM6802A/b/ah/bh (dynamic soft pfc/green pwm) http://www.championmicro.com.tw epa/80++ zvs-like pfc/pwm combo controller design for high efficient power supply at both full load and light load 2012/05/10 rev. 1.5 champion microelectronic corporation 22 CM6802A/b/ah/bh application circuit (voltage mode) 1m 1% 10 pwm is 2n2907 470pf 30l30 380vdc l4 r5*25 14k 1% 10k 47 iso1a 817c byv-26egp emi circuit 0.47uf/16v 0.47uf l3 r5*25 20n60 1 3 2 470 + 150uf/450v 0.22 2w (s) 2.49k 1% l 1 aps27950 1m byv-26egp + 2200uf/10v tl431 2 3 1 in5406 pwm out + 2200uf/16v 20n60 0.1uf/25v 1000pf 470pf (spare) 1m 1n4148 10.2k 1% 470pf/250v 0.2/2w (s) + 2200uf/16v 0.47uf 3m1% 8a/600v 2 1 +12v ac inlet l fg n - + gbl408 2 1 3 4 1m 1% 0.1uf +12v vcc 200k 1% 3m 1% 0.047uf 10 1000pf 1000pf pwm is 10k 0.1uf 4.75k 1% 1/8w l1a 28ts 2200pf 1n5406 20 20n60 4.7k 380vdc 4700pf +5v 10k erl-35 0.2 2w (s) mps751 c b e 470pf 39.2k 1% 0.047uf 820pf pwm out l1b 12ts 30.1k 13k 1% 20 gnd gnd erl-35 22k 243k 16 15 6 1 14 7 10 5 9 8 11 12 4 2 3 13 ve ao vfb vdc ieao vre f ramp 1 gnd ss dcilim ramp 2 pwm out pfc out vrms iac isense vcc 2k 1% 1000pf ei10 pc40 +5v 1uf/400v iso1a 817c + 22uf/25v vre f + 2200uf/6.3v 1000pf 2n2222 36.5k gnd 2200pf b+ 10 1uf 1k 10 r16 10 vcc 55ts 0.47uf in5406 10 CM6802A/b/ah/bh (dynamic soft pfc/green pwm) http://www.championmicro.com.tw epa/80++ zvs-like pfc/pwm combo controller design for high efficient power supply at both full load and light load 2012/05/10 rev. 1.5 champion microelectronic corporation 23 CM6802A/b/ah/bh application circuit (current mode) 0.2/2w(s) 36.5k 2k 1% 10 iso1a 817c 243k 4.75k 1% 1/8w 30.1k 0.1uf pwm is 1uf/400v 470pf/250v 10 1m 1% + 2200uf/16v 10 byv-26egp l3 r5*25 byv-26egp 2200pf in5406 10.2k 1% (spare) - + gbl408 2 1 3 4 10k 0.047uf l4 r5*25 820pf 1m 470pf emi circuit 2n2907 vcc +5v 1n4148 + 2200uf/16v l1b 12ts 14k 1% 55ts 1n5406 l 1 aps27950 0.47uf 470pf 10 mps751 c b e 1m 1m 1% 2.49k 1% 0.22 2w (s) ac inlet l fg n 0.1uf tl431 2 3 1 + 150uf/450v 380vdc 0.47uf 0.2 2w (s) b+ 20n60 + 2200uf/10v pwm out 20n60 1 3 2 1000pf vcc l1a 28ts 39.2k 1% 470 3m1% 380vdc 2n2222 0.047uf + 22uf/25v 22k 200k 1% 4700pf pwm out 2200pf 10 20 gnd 470 gnd 1000pf 0.1uf/25v gnd +12v iso1a 817c +5v 4.7k 0.47uf 1000pf 20 13k 1% in5406 3m 1% 1uf +12v + 2200uf/6.3v 30l30 10k ei10 pc40 16 15 6 1 14 7 10 5 9 8 11 12 4 2 3 13 ve ao vfb vd c ieao vre f ramp 1 gnd ss dcilim ramp 2 pwm out pfc out vrms iac isense vcc 10k 47 0.47uf/16v 1000pf 470pf 1k 8a/600v 2 1 r16 10 erl-35 vre f 1000pf pwm is 20n60 erl-35 CM6802A/b/ah/bh (dynamic soft pfc/green pwm) http://www.championmicro.com.tw epa/80++ zvs-like pfc/pwm combo controller design for high efficient power supply at both full load and light load 2012/05/10 rev. 1.5 champion microelectronic corporation 24 package dimension 16-pin sop (s16) 16-pin pdip (p16) pin 1 id CM6802A/b/ah/bh (dynamic soft pfc/green pwm) http://www.championmicro.com.tw epa/80++ zvs-like pfc/pwm combo controller design for high efficient power supply at both full load and light load 2012/05/10 rev. 1.5 champion microelectronic corporation 25 important notice champion microelectronic corporation (cmc) reserves the right to make changes to its products or to discontinue any integrated circuit product or service without notice, and advises its customers to obtain the latest version of relevant information to verify, before placing orders, that the information being relied on is current. a few applications using integrated circuit products ma y involve potential risks of death, personal injury, or severe property or environmental damage. cm c integrated circuit products are not designed, intended, authorized, or warranted to be suitable for use in life-support applications, devices or systems or other critical applications. use of cmc products in such applications is understood to be fully at the risk of the customer. in order to minimize risks associated with the customer?s applications, the customer should provide adequate design and operating safeguards. hsinchu headquarter sales & marketing 5f, no. 11, park avenue ii, science-based industrial park, hsinchu city, taiwan 21f., no. 96, sec. 1, sintai 5th rd., sijhih city, taipei county 22102, taiwan, r.o.c. t e l : +886-3-567 9979 t e l : +886-2-2696 3558 f a x : +886-3-567 9909 f a x : +886-2-2696 3559 http://www.champion-micro.com |
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