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  1. 1. Chapter 1 Power Electronic Devices Outline 1.1 An introductory overview of power electronic devices 1.2 Uncontrolled device—power diode 1.3 Half- controlled device—thyristor 1.4 Typical fully- controlled devices 1.5 Other new power electronic devices
  2. 2. 1.1 An introductory overview of power electronic devices 1) The concept and features Power electronic devices: are the electronic devices that can be directly used in the power processing circuits to convert or control electric power. Very often: Power electronic devices= Power semiconductor devices Major material used in power semiconductor devices——Silicon In broad sense Power electronic devices Vacuum devices: Mercury arc rectifier thyratron, etc. . seldom in use today Semiconductor devices: major power electronic devices
  3. 3. Features of power electronic devices a) The electric power that power electronic device deals with is usually much larger than that the information electronic device does. b) Usually working in switching states to reduce power losses c)Need to be controlled by information electronic circuits. d)Very often, drive circuits are necessary to interface between information circuits and power circuits. e)Dissipated power loss usually larger than information electronic devices —special packaging and heat sink are necessary. On-state Voltage across the device is 0 p=vi=0 V=0 Off-state Current through the device is 0 p=vi=0 i=0
  4. 4. 2) Configuration of systems using power electronic devices Power electronic system: Protection circuit is also very often used in power electronic system especially for the expensive power semiconductors. Control circuit (in a broad sense) Control circuit detection circuit drive circuit circuit Power circuit (power stage, main circuit) Electric isolation: optical, magnetic
  5. 5. Terminals of a power electronic device Control signal from drive circuit must be connected between the control terminal and a fixed power circuit terminal (therefore called common terminal A power electronic device usually has a third terminal — —control terminal to control the states of the device C G E A power electronic device must have at least two terminals to allow power circuit current flow through. Drive Circuit
  6. 6. Major topics for each device Appearance, structure, and symbol Physics of operation Specification Special issues Devices of the same family Passive components in power electronic circuit Transformer, inductor, capacitor and resistor: these are passive components in a power electron ic circuit since they can not be controlled by control signal and their characteristics are usually constant and linear. The requirements for these passive components by power electronic circuits could be very different from those by ordinary circuits.
  7. 7. 1.2 Uncontrolled device Power diode  Appearance
  8. 8.  PN junction - - - - - - - - - - - - - - - - - - - - + + + + + + + + + ++ + + + + + + + ++ p region Space charge Region (depletion region, potential barrier region) n region Direction of inner electric field
  9. 9. PN junction with voltage applied in the forward direction V + - p n W WO - - - - - + + + + +
  10. 10. PN junction with voltage applied in the reverse direction V +- p n W WO - - - - - + + + + + Effective direction of electronic field
  11. 11.  Construction of a practical power diode + V - Anode Cathode Na =10 cm 19 -3 P + Nd =10 cm -3 Nd =10 cm 19 -3 -314 n+ -n epi substrate 10μ m 250μ m Breakdown Voltage 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 capacitor The positive and negative charge in the depletion region is variable with the changing of external voltage. variable with the changing of external voltage. —–Junction capacitor C Junction capacitor CJ . Junction capacitor influences the switching characteristics of power diode. Junction capacitor CJ Potential barrier capacitor CB Diffusion capacitor CD
  13. 13.  Static characteristics of power diode  Turn-off transient Turn- on transient IF I O UTO UF U IF UF tF t0 trr td tf t1 t2 t UR UR P IR P diF dt diR dt UFP u i iF uF tfr t0 2V
  14. 14.  Examples of commercial power diodes part number Rated vag current VF(typical) tr(max)Rated max voltage Fast recovery rectifiers 1N3913 SD453N25S20PC MUR815 MUR1560 RHRU100120 Ultra-fast recovery rectifiers Schottky rectifiers MBR6030L 444CNQ045 30CPQ150 400V 2500V 150V 600V 1200V 30V 45V 150V 30A 400A 8A 15A 100A 60A 440A 30A 1.1V 2.2V 0.48V 1.19V 0.69V 0.975V 2.6V 1.2V 400ns 20μ s 35ns 6ns 60ns
  15. 15. 1.3 Half- controlled device—Thyristor Another name: SCR—silicon controlled rectifier Thyristor 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 processing area. Still in use in high power situation. Thyristor till has the highest power-handling capability.
  16. 16.  Appearance and symbol of thyristor
  17. 17. Structure and equivalent circuit of thyristor P1 A G K N1 P2P2 N1 N2 a) NPN PNP A G K IG IK Ic2 Ic1 IA V1 V2 b) Structure Equivalent circuit Equivalent circuit
  18. 18. Physics of thyristor operation R NPN PNP A G S K EG IG EA IK Ic2 Ic1 IA V1 V2 Equivalent circuit: A pnp transistor and an npn transistor interconnected together Positive feedback Trigger Can not be turned off by control signal Half-controllable
  19. 19. Quantitative description of thyristor operation When 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 21 CBO2CBO1G2 A αα +− ++ =I ( 1-5 )
  20. 20.  Other methods to trigger thyristor on High voltage across anode and cathode—avalanche breakdown High rising rate of anode voltagte —du/dt too high High junction temperature Light activation  Static characteristics of thyristor Blocking when reverse biased, no matter if there is gate current applied. Conducting only when forward biased and there is triggering current applied to the gate. Once triggered on, will be latched on conducting even when the gate current is no longer applied.
  21. 21.  Switching characteristics of thyristor 100% 90% 10% u AK tO 0 td tr trr tgrURRM IRM i A t
  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 power semiconductor devices nowadays.
  23. 23. 1.4.1 Gate- turn- off thyristor—GTO Major difference from conventional thyristor: The gate and cathode structures are highly interdigitated , with various types of geometric forms being used to layout the gates and cathodes.
  24. 24.  Physics of GTO operation The basic operation of GTO is the same as that of the conventional thyristor. The principal differences lie in the modifications in the structure to achieve gate turn- off capability. –Large α2 –α1+α2 is just a little larger than the critical value 1. –Short distance from gate to cathode makes it possible to drive current out of gate. R NPN PNP A G S K EG IG EA IK Ic2 Ic1 IA V1 V2
  25. 25. 1.4.2 Giant Transistor—GTR GTR is actually the bipolar junction transistor that can handle high voltage and large current. So GTR is also called power BJT, or just BJT.
  26. 26. Structures of GTR different from its information-processing counterpart
  27. 27. Static characteristics of GTR cut-off region Amplifying (active) region Saturation region O Ic ib3 ib2 ib1 ib1<ib2<ib3 Uce
  28. 28. Second breakdown of GTR O ic UCE IB=0 IB5 IB4 IB1 IB2 IB3 Active region Second breakdown Quasi-saturationHard saturation 1 - Rd Primary breakdown IB5 >IB4. etc. IB<0 IB=0 BVCEO BVCBO BVSUS
  29. 29. 1.4.3 Power metal- oxide- semiconductor field effect transistor— Power MOSFET A classification Basic structure Symbol Field Effect Transistor (FET) Metal- onside-semiconductor FET (MOSFET) Power MOSFET Junction FET (JFET) Static induction transistor (SIT) n channel p channel N channel G S D G S D P channel
  30. 30.  Physics of MOSFET operation (Off- state) p-n- junction is reverse-biased off-state voltage appears across n- region
  31. 31.  Physics of MOSFET operation (On-state) p-n- junction is slightly reverse biased positive gate voltage induces conducting channel drain current flows through n- region an conducting channel on resistance = total resistances of n- region,conducting channel,source and drain contacts, etc.
  32. 32.  Static characteristics of power O iD UDS Ohmic [UGS-VGS(th)=UDS] VGS5 VGS1 VGS2 VGS3 VGS4 Active Cut off VGS< VGS(th) BVDSS VGS5> VGS4 etc.
  33. 33.  Switching characteristics of power MOSFET Turn- on transient Turn- off transient –Turn- on delay time td(on) –Turn- off delay time td(off) –Rise time tr –Falling time tf Rs RG RF RL iD uGS up iD +UE iD O O O up t t t uGS uGSP uT td(on) tr td(off) tf
  34. 34. Examples of commercial power MOSFET part number Rated vag current Qg(typical)RonRated max voltage IRFZ48 IRF510 APT105M25BN R IRF740 MTM15N40E APT5025BN APT1001RBNR 60V 100V 100V 400V 400V 500V 1000V 50A 5.6A 28A 75A 10A 15A 23A 11A 0.018Ω 0.54Ω 0.3Ω 1.0Ω 0.25Ω 0.077Ω 0.55Ω 0.025Ω IRF540 100V 110nC 8.3 nC 171 nC 8.3 nC 63 nC 110 nC 72 nC 83nC 150 nC
  35. 35. 1.4.4 Insulated- gate bipolar transistor—IGBT  Combination of MOSFET and GTR GTR: low conduction losses (especially at larger blocking volta ges), longer switching times, current- driven MOSFET : faster switching speed, easy to drive (voltage- driven), larger conduction losses (especially for higher blocking voltages) IGBT
  36. 36.  Features On- state losses are much smaller than those of a power MOSFET, and are comparable with those of a GTR Easy to drive —similar to power MOSFET Faster than GTR, but slower than power MOSFET  Structure and operation principle of IGBT Also multiple cell structure Basic structure similar to power MOSFET, except extra p region On- state: minority carriers are injected into drift region, leading to conductivity modulation compared with power MOSFET: slower switching times, lower on- resistance, useful at higher voltages (up to 1700V) E G C N+ N - PN+ N+ P N+ N+ P+ Emitter Gate Collector Injecting layer Bufferlayer DriftregionJ3 J2 J1
  37. 37.  Equivalent circuit and circuit symbol of IGBT G E C + -+- + - ID RN IC VJ1 IDRon G C E Drift region resistance
  38. 38.  Switching characteristics of IGBT t t t current tail UGEMUGE 90%UGEM 10%UGEM 0 0 0 ICMIC 90%ICM 10%ICM UCE UCEM UCE(on) ton tfv1 toff td(on) tfv2 tfi1 tfi2 tftr td(off)
  39. 39.  Examples of commercial IGBT part number Rated avg current tf(typical)VF(typical ) Rated max voltage Single-chip devices HGTG32N60E2 multiple-chip power modules_ CM400HA-12E CM300HA-24E 600V 1200V 600V 1200V 32A 30A 2.4V 3.2VHGTG30N120D2 0.62μ s 0.58μ s 400A 300A 2.7V 2.7V 0.3μ s 8.3 nC 0.3μ s
  40. 40. 1.5 Other new power electronic devices Static induction transistor —SIT Static induction thyristor —SITH MOS controlled thyristor —MCT Integrated gate- commutated thyristor —IGCT Power integrated circuit and power module 1) Static induction transistor—SIT Another 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 with even higher on-state losses)
  41. 41. 2) Static induction thyristor—SITH other names –Field controlled thyristor—FCT –Field controlled diode Features –Minority- carrier device, a JFET structure with an additional injecting layer –Power- handling capability similar to GTO –Faster switching speeds than GTO –Normally- on device, not convenient (could be made normally- off, but with even higher on- state losses)
  42. 42. 3) MOS controlled thyristor—MCT Essentially a GTO with integrated MOS- driven gates controlling both turn- on and turn- off that potentially will significantly simply the design of circuits using GTO. The difficulty is how to design a MCT that can be turned on and turned off equally well. Once believed as the most promising device, but still not commercialized in a large scale. The future remains uncertain. 4) Integrated gate- commutated thyristor — IGCT The newest member of the power semiconductor family, introduced in 1997 by ABB Actually the close integration of GTO and the gate drive circuit with multiple MOSFETs in parallel providing the gate currents Short name: GCT Conduction drop, gate driver loss, and switching speed are superior to GTO Competing with IGBT and other new devices to replace GTO
  43. 43.  Review of device classifications power electronic devices Current- driven (current- controlled) devices: thyristor, GTO, GTR Voltage- driven (voltage- controlled) devices (Field- controlled devices):power MOSFET,IGBT, SIT, SITH, MCT, IGCT power electronic devices Pulse- triggered devices: thyristor, GTO Level- sensitive (Level- triggered) devices: GTR, power MOSFET, IGBT, SIT, SITH,MCT, IGCT power electronic devices Uni- polar devices (Majority carrier devices): SBD, power MOSFET, SIT Bipolar devices (Minority carrier devices): ordinary power diode, thyristor, , GTO, GTR, IGCT, IGBT, SITH, MCT Composite devices: IGBT, SITH, MCT