Chapter 1 Power Electronic Devices

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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 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. Vacuum devices: Mercury arc In broad sense Power electronic devices rectifier thyratron, etc.. seldom in use today Semiconductor devices: major power electronic devices Very often: Power electronic devices= Power semiconductor devices Major material used in power semiconductor devices Silicon

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 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 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.

4 2) Configuration of systems using power electronic devices Power electronic system: Control circuit (in a broad sense) Electric isolation: optical, magnetic Control circuit detection circuit drive circuit Power circuit (power stage, main circuit) Protection circuit is also very often used in power electronic system especially for the expensive power semiconductors.

5 Terminals of a power electronic device A power electronic device usually has a third terminal control terminal to control the states of the device C A power electronic device must have at least two terminals to allow power circuit current flow through. G Drive Circuit E Control signal from drive circuit must be connected between the control terminal and a fixed power circuit terminal (therefore called common terminal

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 1.2 Uncontrolled device Power diode Appearance

8 PN junction Direction of inner electric field p region Space charge Region (depletion region, potential barrier region) n region

9 PN junction with voltage applied in the forward direction V + - p n W WO

10 PN junction with voltage applied in the reverse direction Effective direction of electronic field p V n WO W

11 Construction of a practical power diode Anode + V n + epi P Na =10 cm 14 Nd =10 cm -3 10μm Breakdown Voltage dependent - - n substrate 19-3 Nd =10 cm 250μm Cathode

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 Static characteristics of power diode I IF O UTO UF U Turn-off transient Turn- on transient u I F d i F i i F d t U FP U F t d t rr t f t F t 0 t 1 t 2 d i R d t I R U R U R t 2V 0 u F t fr t

14 Examples of commercial power diodes part number Rated max voltage Rated vag current VF(typical) tr(max) Fast recovery rectifiers 1N3913 SD453N25S20PC 400V 2500V 30A 400A 1.1V 2.2V 400ns 20μs Ultra-fast recovery rectifiers MUR V 8A 0.975V 35ns MUR V 15A 1.2V 6ns RHRU V 100A 2.6V 60ns Schottky rectifiers MBR6030L 30V 60A 0.48V 444CNQ045 30CPQ150 45V 150V 440A 30A 0.69V 1.19V

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 Appearance and symbol of thyristor

17 Structure and equivalent circuit of thyristor Structure A Equivalent circuit A I A PNP P 1 V 1 I c2 G N 1 P 2 N 1 P 2 G I G I c1 NPN V 2 N 2 I K K a) b) K

18 Physics of thyristor operation A Equivalent circuit: A pnp transistor and an npn G I A V 1 I G PNP I c1 I c2 R transistor interconnected together Positive feedback Trigger S E G NPN V 2 I K E A Can not be turned off by control signal K Half-controllable

19 Quantitative description of thyristor operation I c1=α 1 IA + I CBO1 (1-1) I c2= α 2 IK + I CBO2 (1-2) IK=IA+IG (1-3) IA=Ic1+Ic2 (1-4) α2 I G + I CBO1 + I CBO2 I A = ( 1-5 ) 1 ( α + 1 α 2 ) When IG =0, α1+α2 is small. When IG >0, α1 +α2 will approach 1, IA will be very large.

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 Switching characteristics of thyristor i A 100% 90% 10% u AK 0 t d t r t I RM O t t rr U RRM t gr

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 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 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 turnoff 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. G I A A PNP V 1 I G I c1 NPN S E G I c2 V 2 I K K R E A

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 Structures of GTR different from its information-processing counterpart

27 Static characteristics of GTR I c Saturation region Amplifying (active) region i b3 i b2 O i b1 cut-off region i b1 < i b2 < i b3 U ce

28 Second breakdown of GTR Hard Quasi-saturation saturation 1 - i R c d Second breakdown IB5 >IB4. etc. IB5 IB4 IB3 Active region Primary breakdown IB2 IB1 IB<0 O IB=0 BVSUS IB=0 BVCEO BVCBO U CE

29 1.4.3 Power metal- oxide- semiconductor field effect transistor Power MOSFET A classification Field Effect Transistor (FET) Metal- onside-semiconductor FET (MOSFET) Power MOSFET n channel p channel Junction FET (JFET) Static induction transistor (SIT) Basic structure Symbol D D G G S N channel S P channel

30 Physics of MOSFET operation (Off- state) p-n- junction is reverse-biased off-state voltage appears across n- region

Physics of MOSFET operation (On-state) p-n- junction is slightly reverse biased positive gate voltage induces conducting channel drain current

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 Static characteristics of power id [UGS-VGS(th)=UDS] Ohmic VGS5 Active VGS4 VGS5> VGS4 etc. VGS3 VGS2 Cut off O VGS1 VGS< VGS(th) BVDSS UDS

33 Switching characteristics of power MOSFET + U E u p R L O t i D u GS u GSP R s u p R G u GS R F i D u T O i D O t d (on) t r t d (off) t f t t Turn- on transient Turn- off transient Turn- on delay time td(on) Turn- off delay time td(off) Rise time tr Falling time tf

34 Examples of commercial power MOSFET part number Rated max voltage Rated vag current Ron Qg(typical) IRFZ48 IRF510 IRF540 APT105M25BN IRF740 MTM15N40E APT5025BN APT1001RBNR 60V 100V 100V 100V 400V 400V 500V 1000V 50A 5.6A 28A 75A 10A 15A 23A 11A 0.018Ω 0.54Ω 0.077Ω 0.025Ω 0.55Ω 0.3Ω 0.25Ω 1.0Ω 110nC 8.3 nc 72 nc 171 nc 63 nc 110 nc 83nC 150 nc

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 IGBT MOSFET : faster switching speed, easy to drive (voltage- driven), larger conduction losses (especially for higher blocking voltages)

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) Emitter Gate E G N + N P + N + N P + J 3 J 2 N - N + J 1 C P + Collector Drift region Buffer layer Injecting layer

37 Equivalent circuit and circuit symbol of IGBT C G I D R N - + I D R on - V J Drift region resistance I C G C E E

38 Switching characteristics of IGBT UGE 90%UGEM UGEM 10%UGEM 0 IC 90%ICM t d(on) t r ICM t d(off) t f t 10%ICM 0 t on UCE UCEM t fi1 t fi2 t off current tail t t fv1 t fv2 0 UCE(on) t

39 Examples of commercial IGBT part number Rated max voltage Rated avg current V F (typical tf(typical) Single-chip devices HGTG32N60E2 600V HGTG30N120D2 1200V multiple-chip power modules_ CM400HA-12E 600V CM300HA-24E 1200V 32A 30A 400A 300A 2.4V 3.2V 0.62μs 0.58μs 2.7V 0.3μs 2.7V 0.3μs

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 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 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 Review of device classifications power electronic devices 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 Pulse- triggered devices: thyristor, GTO Level- sensitive (Level- triggered) devices: GTR, power MOSFET, IGBT, SIT, SITH,MCT, IGCT Uni- polar devices (Majority carrier devices): SBD, power MOSFET, SIT power electronic devices Bipolar devices (Minority carrier devices): ordinary power diode, thyristor,, GTO, GTR, IGCT, IGBT, SITH, MCT Composite devices: IGBT, SITH, MCT

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