Power electronics


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Power electronics

  1. 1. Chapter 1 Power Electronic DevicesOutline1.1 An introductory overview of power electronic devices1.2 Uncontrolled device—power diode1.3 Half- controlled device—thyristor1.4 Typical fully- controlled devices1.5 Other new power electronic devices
  2. 2. 1.1 An introductory overview of power electronic devices1) The concept and featuresPower electronic devices: are the electronic devices that can be directlyused in the power processing circuits to convert or control electricpower.Very often: Power electronic devices= Power semiconductor devicesMajor material used in power semiconductor devices——SiliconIn broad sensePower electronic devicesVacuum devices: Mercury arcrectifier thyratron, etc. . seldomin use todaySemiconductor devices:major power electronic devices
  3. 3. Features of power electronic devicesa) The electric power that power electronic device deals with is usuallymuch larger than that the information electronic device does.b) Usually working in switching states to reduce power lossesc)Need to be controlled by information electronic circuits.d)Very often, drive circuits are necessary to interface betweeninformation circuits and power circuits.e)Dissipated power loss usually larger than information electronicdevices —special packaging and heat sink are necessary.On-state Voltage across the device is 0 p=vi=0V=0Off-state Current through the device is 0 p=vi=0i=0
  4. 4. 2) Configuration of systems using power electronic devicesPower electronic system:Protection circuit is also very often used in power electronic systemespecially for the expensive power semiconductors.Control circuit (in a broad sense)Controlcircuitdetection circuitdrive circuitcircuitPower circuit (powerstage, main circuit)Electric isolation:optical, magnetic
  5. 5. Terminals of a power electronic deviceControl signal from drive circuit must be connected between the controlterminal and a fixed power circuit terminal (therefore called commonterminalA power electronicdevice usually hasa third terminal ——control terminalto control thestates of the deviceCGEA power electronic devicemust have at least twoterminals to allow powercircuit current flow through.DriveCircuit
  6. 6. Major topics for each deviceAppearance, structure, and symbolPhysics of operationSpecificationSpecial issuesDevices of the same familyPassive components in power electronic circuitTransformer, inductor, capacitor and resistor: these are passivecomponents in a power electronic circuit since they can not be controlled by control signal and theircharacteristics are usually constant and linear.The requirements for these passive components by power electroniccircuits could be very different from those by ordinary circuits.
  7. 7. 1.2 Uncontrolled device Power diode Appearance
  8. 8.  PN junction- -- --- --- - - -- - - -- - - -+ + +++++ + +++++ + + ++ + ++p regionSpace chargeRegion(depletion region,potentialbarrier region)n regionDirection ofinner electric field
  9. 9. PN junction with voltage applied in the forward directionV+ -p nWWO-----+++++
  10. 10. PN junction with voltage applied in the reverse directionV +-p nWWO-----+++++Effective directionof electronic field
  11. 11.  Construction of a practical power diode+V-AnodeCathodeNa =10 cm19 -3P+Nd =10 cm-3Nd =10 cm19 -3-314n+-nepisubstrate10μ m250μ mBreakdownVoltage dependent
  12. 12.  Features different from low-power (information electronic) diodes–Larger size–Vertically oriented structure–n drift region (p-i-n diode)–Conductivity modulation Junction capacitorThe positive and negative charge in the depletion region is variable with thechanging of external voltage. variable with the changing of externalvoltage.—–Junction capacitor C Junction capacitor CJ .Junction capacitor influences the switching characteristics ofpower diode.Junction capacitor CJPotential barrier capacitor CBDiffusion capacitor CD
  13. 13.  Static characteristics of power diodeTurn-off transient Turn- on transientIFIO UTO UF UIFUFtF t0trrtd tft1 t2 tURURPIRPdiFdtdiRdtUFPui iFuFtfr t02V
  14. 14.  Examples of commercial power diodespart number Rated vag current VF(typical) tr(max)Rated max voltageFast recovery rectifiers1N3913SD453N25S20PCMUR815MUR1560RHRU100120Ultra-fast recovery rectifiersSchottky rectifiersMBR6030L444CNQ04530CPQ150400V2500V150V600V1200V30V45V150V30A400A8A15A100A60A440A30A1.1V2.2V0.48V1.19V0.69V0.975V2.6V1.2V400ns20μ s35ns6ns60ns
  15. 15. 1.3 Half- controlled device—ThyristorAnother name: SCR—silicon controlled rectifierThyristor Opened the power electronics era–1956, invention, Bell Laboratories–1957, development of the 1st product, GE–1958, 1st commercialized product, GE–Thyristor replaced vacuum devices in almost every power processingarea.Still in use in high power situation. Thyristor till has thehighest power-handling capability.
  16. 16.  Appearance and symbol of thyristor
  17. 17. Structure and equivalent circuit of thyristorP1AGKN1P2P2N1N2a)NPNPNPAGKIGIKIc2Ic1IAV1V2b)Structure Equivalent circuitEquivalentcircuit
  18. 18. Physics of thyristor operationRNPNPNPAGSKEGIGEAIKIc2Ic1IAV1V2Equivalent circuit: A pnp transistor and an npntransistor interconnected togetherPositive feedbackTriggerCan not be turned off by controlsignalHalf-controllable
  19. 19. Quantitative description of thyristor operationWhen IG =0, α1+α2 is small.When IG >0, α1 +α2 will approach 1, IA will be very large.I c1=α1 IA + I CBO1 (1-1)I c2=α2 IK + I CBO2 (1-2)IK=IA+IG (1-3)IA=Ic1+Ic2 (1-4)(α III)1 21CBO2CBO1G2Aαα +−++=I ( 1-5 )
  20. 20.  Other methods to trigger thyristor onHigh voltage across anode and cathode—avalanche breakdownHigh rising rate of anode voltagte —du/dt too highHigh junction temperatureLight activation Static characteristics of thyristorBlocking when reverse biased, no matter if there is gate current applied.Conducting only when forward biased and there is triggering currentapplied to the gate.Once triggered on, will be latched on conducting even when the gatecurrent is no longer applied.
  21. 21.  Switching characteristics of thyristor100%90%10%uAKtO0 td trtrr tgrURRMIRMiAt
  22. 22. 1.4 Typical fully- controlled devices Features–IC fabrication technology, fully- controllable, high frequency Applications–Begin to be used in large amount in 1980s–GTR is obsolete and GTO is also seldom used today.–IGBT and power MOSFET are the two major powersemiconductor devices nowadays.
  23. 23. 1.4.1 Gate- turn- off thyristor—GTOMajor difference from conventional thyristor:The gate and cathode structures are highly interdigitated , with various typesof geometric forms being used to layout the gates and cathodes.
  24. 24.  Physics of GTO operationThe basic operation of GTO is thesame as that of the conventionalthyristor. The principaldifferences lie in themodifications in thestructure to achieve gate turn-off capability.–Large α2–α1+α2 is just a little larger thanthe critical value 1.–Short distance from gate tocathode makes it possible todrive current out of gate.RNPNPNPAGSKEGIGEAIKIc2Ic1IAV1V2
  25. 25. 1.4.2 Giant Transistor—GTRGTR is actually the bipolar junction transistor that can handlehigh voltage and large current.So GTR is also called power BJT, or just BJT.
  26. 26. Structures of GTR different from its information-processingcounterpart
  27. 27. Static characteristics of GTRcut-off regionAmplifying (active) regionSaturation regionOIcib3ib2ib1ib1<ib2<ib3Uce
  28. 28. Second breakdown of GTROicUCEIB=0IB5IB4IB1IB2IB3 Active regionSecond breakdownQuasi-saturationHardsaturation 1-RdPrimarybreakdownIB5 >IB4. etc.IB<0IB=0BVCEO BVCBOBVSUS
  29. 29. 1.4.3 Power metal- oxide- semiconductor field effect transistor—Power MOSFETA classificationBasic structure SymbolField EffectTransistor(FET)Metal- onside-semiconductor FET (MOSFET) Power MOSFETJunction FET (JFET) Static induction transistor (SIT)n channelp channelN channelGSDGSDP channel
  30. 30.  Physics of MOSFET operation (Off- state)p-n- junction isreverse-biasedoff-state voltageappears acrossn- region
  31. 31.  Physics of MOSFET operation (On-state)p-n- junction is slightly reverse biased positive gate voltage inducesconducting channel drain current flows through n- region anconducting channel on resistance = total resistances of n-region,conducting channel,source and drain contacts, etc.
  32. 32.  Static characteristics of powerOiDUDSOhmic[UGS-VGS(th)=UDS]VGS5VGS1VGS2VGS3VGS4ActiveCut offVGS< VGS(th)BVDSSVGS5> VGS4 etc.
  33. 33.  Switching characteristics of power MOSFETTurn- on transient Turn- off transient–Turn- on delay time td(on) –Turn- off delay time td(off)–Rise time tr –Falling time tfRsRG RFRLiDuGSupiD+UEiDOOOuptttuGSuGSPuTtd(on) tr td(off) tf
  34. 34. Examples of commercial power MOSFETpart number Rated vag current Qg(typical)RonRated max voltageIRFZ48IRF510APT105M25BNR IRF740MTM15N40EAPT5025BNAPT1001RBNR60V100V100V400V400V500V1000V50A5.6A28A75A10A15A23A11A0.018Ω0.54Ω0.3Ω1.0Ω0.25Ω0.077Ω0.55Ω0.025ΩIRF540 100V110nC8.3 nC171 nC8.3 nC63 nC110 nC72 nC83nC150 nC
  35. 35. 1.4.4 Insulated- gate bipolar transistor—IGBT Combination of MOSFET and GTRGTR: low conduction losses (especially at larger blocking volta ges),longer switching times, current- drivenMOSFET : faster switching speed, easy to drive (voltage- driven),larger conduction losses (especially for higher blocking voltages)IGBT
  36. 36.  FeaturesOn- state losses are much smaller thanthose of a power MOSFET, and arecomparable with those of a GTREasy to drive —similar to powerMOSFETFaster than GTR, but slower than powerMOSFET Structure and operation principle ofIGBTAlso multiple cell structure Basic structuresimilar to power MOSFET, except extrap region On- state: minority carriersare injected into drift region, leading toconductivity modulationcompared with power MOSFET: slowerswitching times, lower on- resistance,useful at higher voltages (up to 1700V)E GCN+N-PN+N+PN+N+P+Emitter GateCollectorInjecting layerBufferlayerDriftregionJ3 J2J1
  37. 37.  Equivalent circuit and circuit symbol of IGBTGEC+-+-+-ID RNICVJ1IDRon GCEDrift regionresistance
  38. 38.  Switching characteristics of IGBTtttcurrent tailUGEMUGE90%UGEM10%UGEM000ICMIC90%ICM10%ICMUCE UCEMUCE(on)tontfv1tofftd(on)tfv2tfi1 tfi2tftr td(off)
  39. 39.  Examples of commercial IGBTpart number Rated avg current tf(typical)VF(typical)Rated max voltageSingle-chip devicesHGTG32N60E2multiple-chip power modules_CM400HA-12ECM300HA-24E600V1200V600V1200V32A30A2.4V3.2VHGTG30N120D20.62μ s0.58μ s400A300A2.7V2.7V 0.3μ s8.3 nC0.3μ s
  40. 40. 1.5 Other new power electronic devicesStatic induction transistor —SITStatic induction thyristor —SITHMOS controlled thyristor —MCTIntegrated gate- commutated thyristor —IGCTPower integrated circuit and power module1) Static induction transistor—SITAnother name: power junction field effect transistor—power JFET Features–Major- carrier device–Fast switching, comparable to power MOSFET–Higher power- handling capability than power MOSFET–Higher conduction losses than power MOSFET–Normally- on device, not convenient (could be made normally- off, but witheven higher on-state losses)
  41. 41. 2) Static induction thyristor—SITHother names–Field controlled thyristor—FCT–Field controlled diodeFeatures–Minority- carrier device, a JFET structure with an additionalinjecting layer–Power- handling capability similar to GTO–Faster switching speeds than GTO–Normally- on device, not convenient (could be madenormally- off, but with even higher on- state losses)
  42. 42. 3) MOS controlled thyristor—MCTEssentially a GTO with integrated MOS- driven gates controlling bothturn- on and turn- off that potentially will significantly simply thedesign of circuits using GTO.The difficulty is how to design a MCT that can be turned on and turnedoff equally well.Once believed as the most promising device, but still not commercializedin a large scale. The future remains uncertain.4) Integrated gate- commutated thyristor — IGCTThe newest member of the power semiconductor family, introduced in1997 by ABBActually the close integration of GTO and the gate drive circuit withmultiple MOSFETs in parallel providing the gate currentsShort name: GCTConduction drop, gate driver loss, and switching speed are superior toGTOCompeting with IGBT and other new devices to replace GTO
  43. 43.  Review of device classificationspower electronicdevicesCurrent- driven (current- controlled) devices:thyristor, GTO, GTRVoltage- driven (voltage- controlled) devices(Field- controlled devices):power MOSFET,IGBT,SIT, SITH, MCT, IGCTpower electronicdevicesPulse- triggered devices: thyristor, GTOLevel- sensitive (Level- triggered) devices:GTR, power MOSFET, IGBT, SIT, SITH,MCT, IGCTpower electronicdevicesUni- polar devices (Majority carrier devices):SBD, power MOSFET, SITBipolar devices (Minority carrier devices):ordinary power diode, thyristor, , GTO, GTR,IGCT, IGBT, SITH, MCTComposite devices: IGBT, SITH, MCT