Introduction Power Factor Correction (PFC) very much necessity off-lin

The Datasheet Archive - 100 Million Datasheets from 7500 Manufacturers.

Introduction Power Factor Correction (PFC) very much necessity off-lin

Datasheet Thumbnail

Top Searches for this datasheet

AND8179/D Using Critical Conduction Mode High Power Factor Correction
Introduction Power Factor Correction (PFC) very much necessity off-line switchmode power supplies requiring output powers watts more. Boost converters using discontinuous mode critical conduction mode design approaches have been mostly relegated power power spectrum because cost simplicity circuitry. turns that critical conduction mode approach offers same simplicity cost power factor correctors kilowatt range additionally offer several performance advantages over more conventional continuous conduction mode typically used this power range. Continuous Conduction Mode versus Critical Conduction Mode Continuous conduction mode typically chosen high power designs because offers lowest peak average current ratio converter throughput power, operates fixed switching frequency. peak average current ratio minimizes power mosfet peak current output (bulk) capacitor ripple current requirements. Referring typical boost pre-converter Figure inductance value choke switching frequency chosen such that component current choke never goes zero during part switching cycle most upper load range. Despite advantage lower peak average current ratio continuous mode boost converter, there several significant disadvantages associated with this conversion mode: "hard" reverse recovery output diode when mosfet switch turns generation high frequency harmonic products probably most significant disadvantage. Keep mind that forward current will normally flowing through diode when mosfet turns continuous mode operation. high power designs output diode must ultra-fast, soft-recovery type. Otherwise additional circuitry composed tapped chokes, saturable inductors, resonant snubbing networks required soften reverse current transient diode switching mosfet turn-on. control algorithm assure maximum power factor minimum harmonic distortion over full input range output load range very complex requires significant external circuitry most cases provide bias sense levels required most commonly used continuous mode control chip. most high power continuous mode designs significant circuit layout "tweaking" necessary before reliable operation conducted emissions assured.
Converter
Rectifiers Line
Preconverter
High Frequency Bypass Capacitor
Bulk Storage Capacitor
Load
Figure Active Power Factor Correction Preconverter
Semiconductor Components Industries, LLC, 2004
October, 2004 Rev.
Publication Order Number: AND8179/D
AND8179/D
critical conduction mode operation, sometimes referred boundary mode transition mode operation, inductor current allowed completely zero before next switching cycle mosfet initiated. Figure illustrates inductor current waveform with mains current envelope superimposed show their relationship. order critical conduction mode technique work properly, means sensing when inductor current reached zero imperative. This done most effectively small auxiliary sense winding boost choke that indicates when flyback voltage across winding dropped less than volt Sensing zero current this indirect method much more noise immune than sensing current directly. consequence having sense zero current point prior mosfet turn-on disallows fixed frequency operation this mode. fact frequency will typically vary over range from midpoint sinewave zero crossing point. Changes output load and/or nominal line operating point will also cause shifts median operating frequency.
Peak
IGBT boost switch, peak currents their impact become less significant following advantages this design approach realized: output diode essentially self-commutates because current zero device before IGBT turns many cases conventional fast recovery diode used boost output rectifier heatsinking necessary because diode losses forward conduction. IGBT mosfet) switch sees zero current switching turn-on heating switching losses generated only when power switch turns off. should also noted that switching frequency lowest when input line peaks maximum hence power switch currents their maximum. Maximum switching frequency minimum switch current occurs around zero crossing point line envelope. average further reduced constantly shifting "dithering" effect variable frequency operation PFC. control algorithm achieving high power factor harmonic distortion using this mode extremely simple accomplished with Semiconductor's MC33262 eight control chip minimum external components. required inductance boost choke approximately fourth that typically required continuous mode chokes. This means fewer turns less expensive chokes most cases. shown that lowest harmonic distortion, choke with linear response characteristic (i.e. constant inductance) desirable critical conduction mode operation. This requires gapped ferrite core which would typically larger structure maximum flux limitations ferrite than would powdered iron Molypermalloy (MPP) magnetic structures commonly used continuous mode PFCs. been found experimentally, however, that more compact choke design necessary, loss powdered iron materials used effectively critical conduction mode long inductance drop caused bias more than about maximum.
Inductor Current
Average
MOSFET
Figure Inductor Current MOSFET Gate Voltage Waveforms
major disadvantage critical conduction mode operation high peak currents mosfet output diode. turns that careful analysis ripple current output capacitor shows that only about times that equivalent continuous mode stage triangular waveshape current associated value. using high speed, higher current density
http://onsemi.com
AND8179/D
Kilowatt Power Factor Corrector Figure shows kilowatt, universal input power factor corrector implemented with Semiconductor MC33262 critical conduction mode control chip single IGBT. internal circuit architecture chip shown Figure Referring these figures basic circuit operation follows: Input signals control chip from output voltage (Pin full-wave rectified line voltage (Pin presented inputs single quadrant, analog voltage multiplier. output multiplier just reproduction rectified line voltage which amplitude modulated output voltage achieve output regulation. multiplier output signal becomes reference current sense comparator. non-inverting input this comparator sees peak IGBT current profile that developed across current sense resistor current sense comparator output pulse width pulse rate modulated signal that eventually drives gate IGBT after some additional logic level signal processing. Note that next critical level signal processing latch where zero current sense detector circuit allows IGBT turned next switching cycle only after choke current reached zero. zero current point detected indirectly looking complete collapse choke flyback voltage
100k 27,1 1N4751A MUR160
result this logical process that peak current being switched IGBT through choke must track frequency sine envelope rectified line voltage (see Figure Because triangular current waveform produced critical conduction control algorithm, turns that average choke current over line half-cycle also sine wave. result that input line current forced sinusoidal phase with line voltage. order harmonic distortion minimal bandwidth voltage control loop must less than line frequency. Capacitor sets this point about bandwidth were wider, error amplifier would attempt regulate ripple component output bulk capacitors This would cause input current waveshape start looking like trapezoidal wave instead sine wave. power factor would still high harmonic distortion would become unacceptable. those interested detailed mathematical description power factor corrector circuits operating critical conduction mode, please Semiconductor Application Note AND8123/D Joel Turchi. (see references)
input from filter
(optional) MUR860 MC33262 IRG4PC50W MUR110 2N2907A R9a, 0.1, output 1N5406
MUR110
Figure Power Factor Controller with MC33262 Controller
http://onsemi.com
AND8179/D
Zero Current Detector 1.2V 6.7V UVLO 13V/ 8.0V Drive Output Latch
1.6V/ 1.4V
2.5V Reference
Timer Delay
Current Sense Comparator
1.5V Overvoltage Comparator 1.08 Vref 10mA Multiplier Error Vref 10pF
Quickstart
Figure Power Factor Controller
Circuit Comments Performance circuit Figure constructed tested with both resistive load switchmode power supply which connected variable load. tests using
Table
Power Vout
"downstream" power supply load done check possible switching circuit noise interactions stability driving typical "real world" load. performance data tabulated below.
0.98 0.96 0.99 0.98 0.99 0.98
Efficiency
(Current) 4.0% 10.1% 2.9% 4.0% 3.2% 5.1%
http://onsemi.com
AND8179/D
following information from additional data taken during testing PFC: Heatsinking required small amount forced fan) blown across breadboard when operated maximum output power. Thermal losses from were minimal. inductor wound ferrite core (Phillips/Ferroxcube E55/28/21-3C90) with turns strands (twisted) #26HN magnet wire over approximately layers. auxiliary winding control chip zero current sensing turns insulated wire spiral wound main winding over width main coil. core gapped each leg. main winding inductance approximately Zener diode along with resistor were added make sure control chip's operating exceed volts. power applications this level dedicated supply recommended, however, this simple approach works satisfactorily. Ultrafast diode added reverse transient protection because IGBT does have intrinsic body diode like mosfet does. optional amp, volt frequency diode that prevents resonant voltage ring-up bulk capacitors when input initially applied PFC. circuit uses appropriate resistive inrush limiting, this diode necessary still recommended. combination form "speed-off" circuit IGBT dramatically lowers device's turn-off switching losses. optional comprised turns wire around small powered iron toroidal core give inductance about This forms network with polypropylene input capacitors help reduce differential mode conducted EMI. Although paralleled current sense resistors through will result watts dissipation with full power mains input, recommended that current sense transformer used substitute because noise effects propagation delays sensing current peaks. found that reliable starting under output load universal input conditions, needed least dedicated source used this issue. optimum values will depend circuit layout resultant common mode noise that exists circuit whole. will less most applications while will optimum between Keep mind that filter will required before input rectifier meet agency requirements conducted EMI. Common mode megahertz range will typically lower than that produced equivalent continuous mode circuit. Lower frequency differential mode components higher should fall below lower specified agency limit designed properly. High value resistors should probably broken down into series elements adding required resistance. They shown schematic single resistors simplicity. References: AND8123/D. "Power Factor Controller Stages Operating Critical Conduction Mode." www.onsemi.com MC33260/D. "GreenLinet Compact Power Factor Controller: Innovative Circuit Cost Effective Solutions." www.onsemi.com MC34262/D. "Power Factor Controllers." www.onsemi.com
http://onsemi.com
AND8179/D
Semiconductor registered trademarks Semiconductor Components Industries, (SCILLC). SCILLC reserves right make changes without further notice products herein. SCILLC makes warranty, representation guarantee regarding suitability products particular purpose, does SCILLC assume liability arising application product circuit, specifically disclaims liability, including without limitation special, consequential incidental damages. "Typical" parameters which provided SCILLC data sheets and/or specifications vary different applications actual performance vary over time. operating parameters, including "Typicals" must validated each customer application customer's technical experts. SCILLC does convey license under patent rights rights others. SCILLC products designed, intended, authorized components systems intended surgical implant into body, other applications intended support sustain life, other application which failure SCILLC product could create situation where personal injury death occur. Should Buyer purchase SCILLC products such unintended unauthorized application, Buyer shall indemnify hold SCILLC officers, employees, subsidiaries, affiliates, distributors harmless against claims, costs, damages, expenses, reasonable attorney fees arising directly indirectly, claim personal injury death associated with such unintended unauthorized use, even such claim alleges that SCILLC negligent regarding design manufacture part. SCILLC Equal Opportunity/Affirmative Action Employer. This literature subject applicable copyright laws resale manner.
PUBLICATION ORDERING INFORMATION
LITERATURE FULFILLMENT: Literature Distribution Center Semiconductor P.O. 61312, Phoenix, Arizona 85082-1312 Phone: 480-829-7710 800-344-3860 Toll Free USA/Canada Fax: 480-829-7709 800-344-3867 Toll Free USA/Canada Email: orderlit@onsemi.com American Technical Support: 800-282-9855 Toll Free USA/Canada Japan: Semiconductor, Japan Customer Focus Center 2-9-1 Kamimeguro, Meguro-ku, Tokyo, Japan 153-0051 Phone: 81-3-5773-3850 Semiconductor Website: http://onsemi.com Order Literature: http://www.onsemi.com/litorder additional information, please contact your local Sales Representative.
http://onsemi.com
AND8179/D

Introduction Power Factor Correction (PFC) very much necessity off-lin

Top Searches for this datasheet

Other recent searches