power devices - technische universität münchen · pdf file2 power devices in power...

1

„Power Devices“

Prof. Dr.‐Ing. Hans‐Georg Herzog([email protected])

Prof. Dr.‐Ing. Ralph Kennel([email protected])

Technische Universität MünchenArcisstraße 21

80333 MünchenGermany

2

Power Devicesin power electronics active operation of power semiconductor devices is avoided

• either the voltage at the device is 0

• or the current in the device is 0

unfortunately power semiconductor devices are no ideal switches!

→ what requirements have to be postulated ?

switch off switching event switch on

• low blocking current • low switching losses • low voltage drop

• bidirectional blocking • short switching time • bidirectional conduction

• high blocking voltage • free control oftime of switching

• high current capability

• high du/dt • no snubber circuits • high di/dt

3

Losses in Real Power Semiconductor Devices

switch-onlosses

switch-offlosses

conductionlosses

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Hard Switching Devices

• high stress on semiconductor• wide SOA (safe operation area) necessary• low switching frequency• problematic with respect to high power

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Soft Switching Devices

• low stress on semiconductor• high switch-off current possible• high switching frequency• simple gate driving circuits• additional power components necessary

6

IGBT Turn-Off with Snubberhard switching

Eoff = 226µJ Eoff = 98µJ

with snubber

current “pops up”

but losses are still greatly reduced in the semiconductor

the overall losses, however, increase

Gate voltage

Collector current

Collector voltage

Gate voltage

Collector current

Collector voltage

400V, 20A, 125°C, RG = 9.1Ω

7

„Power Devices“

Diode(Thyristor, GTO, IGCT)

Referents:Prof. Dr.‐Ing. Hans‐Georg Herzog

([email protected])Prof. Dr.‐Ing. Ralph Kennel

([email protected])Technische Universität München

Arcisstraße 2180333 München

Germany

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Power Diode Characteristic

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Power Diode Switching-Off Behaviour

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PIN - Diode… to ensure a sufficient voltage capability …

… the junction area is increased in distance…

… by introducing a so-called „intrinsisc“ layer

(= semiconductor material without any doping)

between the p-doped and the n-doped layer …

PIN - Diode

p nii

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ThyristorStructure

ACA

A

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Thyristor Characteristic

13

Triac

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/ GTO

standard thyristortechnology

single waferuntil 150 mm

low conductionlosses

high currentcapability

high switching losses

high powerfor driver circuit

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GTO IGCT

both are controllable thyristors –

however, according to different philosophies

GTOearlier in the market

switch-off concept :by deviating

a part of the load current (ca. 30 %) via the gate

filigrane structure on the chip

IGCT(too) late in the market

switch-off concept :by deviating

the full load currentvia the gate

very complex driver circuits

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„Power Devices“

(bipolar) Transistor





Germany

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Bipolar Power Transistor

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Switch-On Behaviour of a Bipolar Power Transistors

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Switch-Off Behaviour of a Bipolar Power Transistors

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Darlington Structure

UBE1 = 0,7 V

UCE1 =0,3 V

UBE2 = 0,7 V

UCE2 =0,7 V+ 0,3 V

= 1,0 V

transistor in saturation UCE1 < UBE1

transistor achieve saturationUCE2 >> UBE2

very high conduction losses

21

„Power Devices“

Field Effect Transistor (FET)





Germany

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Field Effect Transistor (MOSFET)Structure

channel : long and thin high internal resistance

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channel : still thin - but not as long any more

low internal resístance

Field Effect Transistor (MOSFET)Structure

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Field Effect Transistor (MOSFET) parasitic pnp-transistor

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Field Effect Transistor (MOSFET) parasitic capacitances

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„Power Devices“

Insulated Gate Bipolar Transistor (IGBT)





Germany

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Insulated Gate Bipolar Transistor (IGBT)Structure

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Insulated Gate Bipolar Transistor (IGBT)Structure and Equivalent Circuit

bipolar pnp-transistor

Think of it as a MOSFET with low conduction loss.

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Insulated Gate Bipolar Transistor (IGBT)parasitic capacitances

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Insulated Gate Bipolar Transistor (IGBT)parasitic (latch-up) transistor

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MOSFETtechnology

chip size until20 x 20 mm²

low powerfor driver circuit

low switching losses

high voltage drop

contactingproblems

32TECHNOLOGY TO THE NEXT POWER

On-State Voltage Comparison – Same Die Size

•IGBT has lower on-voltage above about 4 Amps.

•MOSFET conduction loss is sensitive to temperature, the IGBT is not.

•APT6038BLL: ID = 17A

•APT30GP60B: IC2 = 49A

MOSFET 125 °C

MOSFET 25 °C

IGBT

On-State Voltage vs. Current

0

10

20

30

40

50

60

0 10 20 30 40

Current (A)

Vo

ltag

e (

V)

APT6038BLL (25 °C) APT30GP60B (25 or 125 °C)

APT6038BLL (125 °C)


Conduction Loss Comparison – Same Die Size

•IGBT has much lower conduction loss above about 4 Amps.

•IGBT has much better overload capability.

Conduction Loss vs. Current (125 °C)

0

200

400

600

800

1000

1200

1400

0 5 10 15 20 25 30 35 40

Current (A)

Po

wer

(W)

APT6038BLL APT30GP60B

MOSFET

IGBT

3434

Power MOS 7MOSFET Power MOS 7 IGBT

APT6010B2LL, 400V, 50A, 125 ºC, 5 Ohms APT50GP60B, 400V, 50A, 125 ºC, 5 Ohms

Switching Loss: 54A MOSFET vs. 72A IGBT

Eoff = 1062 µJ Eoff = 1058 µJ

•At 50A, the IGBT has lower conduction loss and lower switching loss.

•At less current, the MOSFET would have lower Eoff (no tail current).

•The IGBT is about half the size of the MOSFET – lower cost.

Tail currentCurrent

Voltage

VGS

Current

Voltage

VGS

TECHNOLOGY TO THE NEXT POWER


Frequency vs. Current

0

100

200

300

400

500

5 10 15 20 25 30

Current (Amps)

Fre

qu

en

cy (

kH

z)

APT15GP60B APT6029BLL

Application Comparison – Hard Switched Boost

MOSFET is best at low current, very high frequency.IGBT is best at high current.IGBT is lower cost.

IGBT

MOSFET

Boost: Hard switched

400V, TJ = 125 C, TC = 75 C, 5

APT15GP60: IC2 = 30A

APT6029: ID = 21A

MOSFET is 2.5 times larger than IGBT.

IGBT has good overload capability.

36

Advantage of IGBTs

• Lower cost – much smaller die size for same power.

• Excellent overload capability – linear conduction loss versus current, very insensitive to temperature.

• Simple gate drive – can replace MOSFETs – positive only gate drive

• Highest speed IGBTs – turn-on is the same as a MOSFET, turn-off is only slightly longer.

• Suitable for soft and hard switching – zero voltage or reduced voltage turn-off not as good as MOSFETs.

TECHNOLOGY TO THE NEXT POWER

37

Parallel Connection of IGBTs

• additional resistors in series

• semiconductor design with integrated path

with a positive temperature coefficient

40

Siliziumkarbid (SiC)

41

Reasons for Wide Band Gap Devices Added Value and Related Impact

source :Pierric Gueguen, Market & Technology Overview of Power Electronics Industry and Impact of

WBG Devices, Yole Développement, SEMICON Europa 2014, Grenoble, 09.10.2014

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Quelle : Teresa Bertelshofer; Universität Erlangen

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Comparison Si SiC(switching) losses

source : www.infineon.com/sic; Power Electronics Europe ; Issue 6 2009„Efficiency Improvement with Silicon Carbide Based Power Modules“

http://www.infineon.com/sic

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SiC Device Application Roadmapsource :

Pierric Gueguen, Market & Technology Overview of Power Electronics Industry and Impact of WBG Devices, Yole Développement, SEMICON Europa 2014, Grenoble, 09.10.2014

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Silicon Carbide (SiC)

• better (faster ?) switching

• higher temperature robustness

• voltage drops ?

• cannot be produced on

„outsourced“ production lines for memory chips

investment cost not negligible

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Key Characteristics of GaN vs. SiC vs. Sisource : ECPE

56

„Power Devices“

Mechanical Design andCooling Techniques





Germany

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Power Module and Disc Design

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Housings

plastic

aluminium

silicon

aluminium

AlN substrate

soldering

simple mounting (screws)insulation to groundsuitable for single chipsundefined fault behaviourexplosion posiible

copper

molybdenium

aluminium

silicon

Aluminium

metal substr.

copper

Power Module

Disc Design double sided coolingfault shortcutsuitable for series connectionlow flexibilitymechanical provisions

for pressing

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Insulated Gate Bipolar Transistor (IGBT)Mechanical Design

60

Driver Circuits

61

Cooling Techniques

Cooling of Power Devices

• thermâl equivalent circuit

• natural convection

• forced air cooling

• liquid cooling

62

Electrical Equivalent Circuitfor Modelling of Thermal Behaviour

Dualism :heat source current sourcethermal energy currenttemperature electrical potentialtemperature difference voltagethermal resistance electrical resistanceheat capacitance electrical capacitancedoes not exist electrical inductance

… therefore temperature can physically not „oscillate“

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… in case of simple heat distributions of low complexitythe components of the equivalent circuit can be calculated

from the geometry of the design and the physical parameters of the material

… for more complex heat distributionsFEM simulation software is available in the market

… like in the case of electrical resistors

Elektrical Equivalent Circuitfor Modelling of Thermal Behaviour

64

Alternative : by measurement as in the analysis of electrical circuits

… e. g. by measuring step response(s)


65

advantage of electrical equivalent circuit :

transient heat dissipation can be calculated simplyby methods of network theory and signal analysis


66

natural convectionheat transfer from heat sink

to surrounding airdepends on :

temperature difference„active“ surface speed of airflow

… therefore the heat sink must …

contain materialof good thermal conductivity

(aluminium, copper etc.) thick root and as many ribs as possible

provide surface as wide as possible(mostly as aluminium profile)

have a dark surfacebe mounted vertically

(chimney effect)

67

more designs of heat sinks

• punched and molded sheet metal

• plug-on star-shaped or flag-like heat sink

– made of aluminium

– made of phosphorus bronze

– made of sheet steel

• base plate made of aluminium,

with pressed in cooling sheets

68

in comparison to natural cooling (convection)the thermal resistance of the heat sink

can be reduced to 1/5 ... 1/15by forced air cooling

with respect to the major part of convectionin the cooling

a black/dark surface does not really have an effectin case of forced air cooling

Forced Air Cooling

69

Liquid Cooling

lower temperature drop betweenheat sink surface and cooling liquid

higher power transfer or lower temperature of the chip

(long life time)

with respect to ist high thermal capacitance(specific heat cp = 4,187 kJ/kg *K)

water is suitable for heat transfermore than other liquids (oil or glycol)

70

Liquid Cooling in the Cooling System of a Vehicle:

by additional mixing of e. g. glycolthe thermal capacitance of the liquid is reduced

at the same time viscosity and specific weight of the cooling liquid increases

with increasing percentage of glycolthermal resistance between heat sink and cooling liquid increases significantly

50 % glycol addition increase of Rthhw by 50...60 %90 % glycol addition increase of Rthhw by 110...130 %

Liquid Cooling

71

Heatpipes are for heat transport

… are used,to transmit the heat from a device

to the heat sink(e. g. in case of cramped space condition)

... improve the temperature distributionas well as the dynamic behaviour

Liquid Cooling by Heat Pipes

power devices - technische universität münchen · pdf file2 power devices in power...

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