Summary of Lecture 1 on Power Electronics I - Slides | ECE 562, Study notes of Electrical and Electronics Engineering

Download Summary of Lecture 1 on Power Electronics I - Slides | ECE 562 and more Study notes Electrical and Electronics Engineering in PDF only on Docsity! ECE 562 Week 10 Lecture 1 Fall 2008 Week 10 Lecture 1 Summary Problem 6.267-77 Lm in flyback converters56-66 Synchronous rectification49-51 Problem 6.552-55 Snubbers78-89 Diode stresses44-48 Resonance and ringing36-43 Flyback converters16-35 PWM12-15 Regulator requirements and applications7-11 Linear vs. Switch mode converter3-6 TopicSlides ?~— Sy ae Veen : o's) Comet mar eR | saose90 ante ; = \ me Ty — Fig.3. Implementation af the MIC2T6® Post-Regulated by the MICST9O. Ty of Converter - Vin lL, “CK Vout Vew Filtes Ke ® FLoap Figure 3-20 Switching regulator principle. ty 7a 4 Chapter 1 Introduction g 7A Veo.vin 4 y Mio * 2 Vr. Veo y >A ou Veo,vio Wo y Wo Ver MEM ve VariDge eux Pentium Vac Motherboard Ve Pentium It STORY Motherboard Pentium Ill Motherboard Figure 1-3 Next generation motherboards require a higher number of specialized regulators. ae Applications LCD Displays Handheld Devices Portable Applications Cellular Phones aa Digital Cameras  Typical Applications = Microprocessor Power supplies 0 Low voltage 1-5V 0 High Current 100A 0 Low Noise (Low Ripple) * @ Today's Servers Contain Several Microprocessors @ Businesses May Have Several Servers @ Uninterruptible Power Supplies (UPS) Importance of PWM * Switch-mode converters employ a on-off power switches so power dissipation is low * PWM Duty cycle D is used to control the switch output power. power conversion efficiencies exceeding 90% are common, about twice that of a linear regulator. Neglecting» ( Chest Rhewsh @ Ow & LC perasric) on Aver AAe ‘Peak, max Average or Web notes Lecture 14 Disadvanta: in and Introduction ie onverter |, Use of Transformers or Coupled Inductors in PWM Converters A. Disadvantages of Transformers for PWM Converter Circuits v i r with a Coupled Inductor ransformer Drive A. Origin of the flyback from the buck-boost B. Circuit Model for CCM and DCM. Operation C. ‘Erickson Problem 6.4: Two Transistor Flyback Implementation in DCM Operation Ill. Flyback Converter Mode Transformer ¥e oe He ee WWch Soe LY * flow in the primary. This is flyback operation. Next we use the full transformer like circuit model to describe the coupled inductors and explain alternate current fiows in the primary and secondary during different time intervals as well as energy storage. B, Model of Flyback for CCM and DCM Operation Smell 41) Magnetizing Inductance, L, , EI Ina flyback due to the air g Ee ancete much erat than in a core without an air gap. Hence, a much smaller ‘magnetizing inductance occurs as compared to an un-gapped ‘core where the magnetizing inductance is large. In short, in the flyback core Lu is small and a LARGE lu current flows, Use the circuit below for the analysis. The contro! signal switches Q; on then energy builds up in L, for duration D,T,. Current is flowing into the L.. inductance but due to 0, placement and the arrangement no secondary current Dots an ‘Assuming CCM, when the control voltage switches Q, off then le flows in @ loop into the primary with one tum, n= 1, flowing out of the dot => i flows in of the n-tun secondary winding as follows. It comes into the dot side of the secondary coil or out of the undot side of the colftuming D, of so that Eni= 0. Latis chésen small to= maximize in. Me ‘ Maximize b. (vs) dt — bn Durink D cere? @ ened} 6X of y7 Gon Det e + Vig ™ Subinterval 1 7 Neti nie - ath | Transformer model | CCM: smail ripple *4 approximation leads to burns fet ay a et ¢ Son Penne a fea of Power Electroni: pter ae: Converter circuits Das X00 leg “Saturate Use (7B ofL Don ® Subinterval 2 E (Lend —_ Seconbery 5 : V. ai | i 7 ea oat) wn ea mode! Tran un bi v Y= H s v ic= k = _ i,=0 *# CCM: small ripple approximation leads to y=-¥ —fv¥ io f ~ 4 7 Veryay §,=0 'D id, Came Fundamentals 6f Potoer 4 « Uerw afcere) circuits | \ Use core with sir” bag |  A two-winding inductor Symbol is same as transformer, but fi m transformer *# Energy is stored in magnetizing inductance Magnetizing inductance is relatively small + Current does not simultaneous Ly flow i in fed and secondary windings D, « Instantaneous win a Trad £ Fu sie ‘Ke ‘““® » Instantaneous (and rms) j range Qe + Model as (small) magnetizing inductance in parallel with ideal transformer Fundamentals of Power Electronics 59 Why? Chapter 6: Converge cireuts Summ y Flyback configuration so Rv wh . Vd b—ton—— t off —4 com Were Qon, Daft | Qoff, Don “A ot Vdspk=Vg+(NI/N2)(V+Vd) YAOe Peak 0X! “S tert : " vivernaf onto down ie Bele ct Tt (VeVdjnt/n2 —n t —} eel Lon gmat a ” i ee the hoe & Ve i‘ 7 5. Flyback transformer” —= ae %4 Eln,5) Nica >t- . & Atwo-winding inductor | t « Symbol is same as fg Rey transformer, but function differs significantly from 7 - ideal transformer a a] « Energy is stored in ° L w magnetizing inductance | the Secondory * Nupeemnacin yy + Current does not simultaneously flow in primary and secondary ‘iopend + Instantaneous winding voltages follow turns ratio | + Instantaneous (and rms) winging currents do not follow turns ratio Afabe.s | « Model as (small) magnetizing inductance in parallel with ideal transformer Fundamentals of Power Electronics 0 Chapter 6: Converter circuits “# vw ‘ Discussion: Flyback converter —— \. or Widely used in low power and/or hi igh voltage applications Seed] Low parts count Se Multiple outputs are easily obtained, with minimum additional parts e Cross regulation is inferior to buck-derived isolated converters *# « Often operated in discontinuous conduction mode « DCM analysis: DCM buck-boost with turns ratio Fundamentals of Power Electronics 65 Chapter 6: Convefler circuits  Rings actly Vora ge Ethers ———— “Ring Vio aeress ene, ‘exis iW One Sco hi ka Vi nat av, Prwy Awanskermer has «4 vag Ly rie nS at 2 4b tow ft Tis é ea e Reales rc =  ITnkes be Pou bY Vy, [ off) stress ig wars cose (wo t\ = Viev — om “EU Ss + L. \lew’ cats. @ Lett a\3 pan! ee ties : &® Wirids call My htt | XL ne av Mie * Ss Me We Yglat) , Le: ig Cerrast | Do on MB aupiopower “4 /{ th e izing inductance (L Resonant frequencies are given by Eqs. 1 and 3; 1 fares: = = RES InJLa x. Ta XC (Eq, 1) 1 fe (Tine - where f,,., equals the resonant frequency due to the transformer leakage inductance, fe; equals the resonant frequency due to the transformer magnetizing inductance, Lye. equals the transformer leakage inductance, L equals the transformer magnetizing inductance and equals the transformer resonant capacitance, = re heen aire Seta MAG Cus Pe ¥e ee ee Next mext level ae Series resopance 2 Vag ff) Ra: - fig tine, ul = las ona Xo pie ee NOE hia . i alt per a Emce Toi Ting oor ot Pass Comphance Choices FET with Ca, Teh with \, wing Consegvences Vas Vag Tings + ‘ We \ L On~ ony, vse we a iw Series driven The Same Ny lof effeoks + 2 Second Lex Clamp ery aN. Never mars —~ than “gt ~ a Nevaeh more + Fran Vy Vg (acest) Diode oo ae VO) 2c diode S Bei 2 ote GT pt Lg ‘s 4 b wicant Vp =aNy nN" Trans terme Vee (2) Ny, if hy We ovate —tVo ¢ <i fe aie Tevers> iad | ‘6 7 i ye HN Wor one? i Ch 14 Le ond Cyst) Bide: Rinainy Asa Gavses Noss Eme — MTs Switches Eni —~ gines evrers XO éontrl) ewes results oY EMy ebecons tones rules ft + a Mudd, Inigher Tig £ : 1 ap ot TMA any LS peutial pe qarnartie’s “ie fram SW wiring Trt, arate . Tavasitic tpg oe ‘ CSomance vi Ly [trans former) - oe ( bit hed  ‘Sof-Seart Plenre 1: Flyback Power Supply with Discrete Semiconductors Needed for: UTE talvration FS ety &. sad B, Meike Te us Fi : | Need Uns: 4 2enSer .  ies “Fig. In this flyback circuit, Jqput de current s derived from voltage across the sense resistor, www.allegromicro.con e Features of Magnetic and High Current Circuit: = High Dielectric Isolation (2.5 kV) « Smail Package Size « Low Resistance (730 w.Q) Fully integrated and Calibrated Solution High Reliability Provided by Monolithic Hall IC Ultra-low Power Loss Very Low Thermal Drift of Signal Accuracy “*  120-W adapter (left) are improved with the redesign (right) that eliminat- ed the need for a heatsink by using a SmartRectifier and SO-8 MOSFETs.  T Jed Suhn ts Trablen 6S eA wo Nenulael Flyback couserter:, nd ame, LL. = Yekl HospeT ena renttente Rn Trade Gramed wlhage amp Mb Flak timate windy reiastnces so Sittin 4 Twhlen 65" Novidead Fly beck hack cowerter, com D 4 , ai Yell HosFEeT — ena vesithance Rew Dede Poraord vollage drop Ve Figeak trasfarver windy resivbeuces Rand Rs Fpaeled coat wodel used Loe Pyback RwE  " few Fundamentals of Power Electronics fa Chapter 6; Converter circuits  Fig. 1. Typical flyback converter.  Fig.2. Current waveforms far (a) Continuous made and (i) Discontinu- ous mode. Why L,, Small iv ree F 4 elirg wes ine) each Sib eat aaa ap -— cs oy Lm Lmt EltF each fie iy air SoP (a) —~ By pa A= +  B (a Volt seconds) af Fluxing = AB ——— Current for larger gap *— Primary current a fem current to primary) “8 Fig. 3. An idealized B/H characteristic for the continuous mode fivback transformer.  pet ce UO Fly bac 5 os ao“ wet PE EE i ‘i a = Vie Fe Reet Aa te hh eth soot bo * oa* sees tae term Vip. ‘ t = ak te L 4 tr \ “5 I a Conditions Lee DEM Iw Occur peace SS edt morn rr - Ze fons To sec TEN ont <3 | all: eat ‘uaia)= 5e1%, tid The lc cet ripple, : velired te primary la) is Ce ee eptning creed ais SYS ~— Sih Me me rete et oles, ee BT er 2 2 ey eae Ae 3 OO > ae ran marl Pent or fn beled at ie haga yh aes ke _ bed te pmey, bt Ris commded te Ae et ek ——_. hoe Stress on Q iv DEM mode <5 Lids \ 2D: Vag? Ltn) bw?, Stress on Serenluy Side Dy RA, Vy lilt =, 9% ' an, = ; f a dy ~ Nylew) 20 Tia)- 4." = Va! o i VbH) .* TL Dim. Flyback tu . ductor yal aemd balance: Oy, - be Sapacttee charge baboon | - OA ie YN Seles e ¥e Re Slowing down the Switch transitions Page | of 1 ae Slowing down the Switch transitions ao Besides reducing L, we can reduce di/dt and thereby reduce the voltage spike which follows from V=Ldi/dt mH In other words, besides focussing on layout alone, we can reduce the noise spikes is by slowing down the switch — > One way to do this is to simply use a slower switch — either a mosfet with a higher gate charge or a bipolar junction transistor (bjt). = Another common way to do this is to insert a small resistor (typically 10 ta 20 ohms) in series with the bootstrap capacitor as shown below. But note that this only slows down the turn-on, it does nothing to the turn-off.  Snubbors pee eS me @ Loc Le, ‘alse Reduces Cocuen. ae Teo “os GLa ott es FET a on ee ony We coe Tat 1 40 Wpiahors z Saebler, ora i of Tanke : W), one Ven > #8 : With SriVher Ver £ $0 L, lS Vv, a wt ‘ ery 3 Vceen a Vy +t (at be Figure 2a: Flyback converter with primary RC snubber. —s- Ringing 'frequeney = 12 MHz * 7 3 Secondary Ringing Solution Turn ott o£ disse ig also a& Source of vith ing due te: A, Qar Cay of Mode 2. C Cott) appears tong) 6. Lb pe ‘ee & Scterdoy ert + * t Vo wk SN, Rarhoitics ab . =: = ob Kb - 3 ae Vp x nVy ¥Vo Ch “4  H_snvbber — Figure 5b: Secondary diode waveform with- out snubbera Ringing frequen- ey = 24 MHz __ i or ates TING Le-C, Figure Sa: RC Snubber addec to the flyback secondary