PE&DS Slide Group 2 2014

8/10/2019 PE&DS Slide Group 2 2014

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School of Electrical and Electronic Engineering © Dr. N. Ertugrul

TYPES of DIODES

Higher current and voltage ratings

Fast recovery diodes

Schottky Diodes

Germanium Diodes

GaAs diodes Silicon Carbide Diodes

SiliconDevices


IF(AV) = 1.5 to 40 A

PARAMETER GaAs Si

VBR (V) 2500 1400

trr (nsec) 25 50

VF (V) 1.8 1.6

T jmax (oC) 260 150

Jmax (A/cm2) 500 300

Performance ComparisonUltrafast GaAs Power Diodes





States of Diodes

vf

id

A K

+ -

Conducting

A K

+-

id = 0

Blocking




Conduction Losses of Diodes

i

v

Ideal diodecharacteristic

In an ideal diode:vf = 0

Ploss = 0

A K

+ -vf


In Practical Diodes

A K

+ -vf

i

v

Operatingpoint

vf = 0

Pd = id . vf = 0

id

vf




Parallel Connected Power Diodes

To increase the current carrying capability.

D1 D2

R1 R2

L1 L2

Helps current sharing under steady-state condition

COUPLED INDUCTORSHelps current sharing under dynamic conditionIf ID1 rises L1di/dt increasesOpposite polarity voltage across L2

Low impedance path through D2 and current is shifted to D2

The current sharing will be depended upon theirrespective forward voltage drops.

It can be achieved by- connecting current-sharing resistors (losses !)- providing equal inductances, e.g. in the leads- selecting diodes with equal forward voltage drop.


Series Connected Power Diodes If a diode cannot meet the required voltage rating

Connected in series to increase the reverse blocking capability.

D1

D2

D1

v

iD2

However, the same type of diodesdiffer due to the tolerance of theirproduction process.

In the forward biasedcondition, both diode

conduct almost the same

amount of current.

In the reversed biased condition, each diode has to carry the same

leakage current. THEREFORE THE BLOCKING VOLTAGESWILL DIFFER.

Vd1 Vd2

-Is




Series Connected Power Diodes

D1Rs

Cs

D2Rs

Cs

Rs

Rs

For steady-state

voltage sharing.

Voltage sharing under

dynamic condition

(such as switching

loads) can be achieved

by the capacitors.


POWER ELECTRONIC

DEVICES :

THYRISTOR





DC

gates DC

6 in ONE

Single

gatespower terminals

2 in ONE




THYRISTOR FAMILY

SCR

TRIAC RCT GATT FCT ASYMMETRIC MCTGTO

Commonly used Thyristors

•Phase control thyristors

(slow, 50Hz, 60Hz)

• Inverter thyristors (fast, kHz !)


G

K

A

THYRISTOR (two transistors model)

G

K

Apnp

npn

IA

IC 2

IB 1

IK

IB 2IG

IC 1

4 LAYER DEVICE

G

K

A

p

n

p

n

p

n

pn




THYRISTOR - Regeneration

G

K

A

IG

gate signal, IG= IB2

IC 2

IB 2

IG causes IC2 (and IB1 )

IB 1 IB1 causes IC1

IC 1 IC1 increases the original

IB2

two transistor builds each

other up continuous conduction

occur if IC1 > IG(initial) !

IK

IA

must be forward biased

+

-• and it conducts load current IA


Tyhristor’s Characteristic Curves

v

i

B) On-state characteristic

(Forward conduction)

IG3 > IG2 > IG1 > IG0

A) Forward blockingstate characteristic

C) Off-state characteristic

(Reverse blocking)




A) Forward Blocking State

The highest

repetitive

peak forward

off-state voltage

Forward

breakdown

voltage

+Load

v

i


b) On-State Characteristic(forward conduction)

Holding current, IH

The threshold

voltage

+Load

v

i

On-state

voltage drop

Latching current, IL




C) Off-State Characteristic(Reverse Blocking)

The highest repetitive peak

reverse -blocking voltageReverse

breakdown

voltage

+Load

v

i


Requirements to TURN-ON and

TURN-OFF of a Thyristor

To turn-on :

G

K A

•VAK > 0 AND

•VGK > 0 AND

• iT > IL

• iT < IH AND

•VAK = 0 OR

VAK < 0

To turn-off :

G

K A




Features of (Thyristor)• Very higher rating thyristors are available

• One-way switch

• Controlled turn-on capability

• No controlled turn-off capability (except GTO, MCT)

• dV/dt (off state voltage) limited , (low impedance or

uncontrolled switch on)

• dI/dt (on state current) limited , (very rapid local hot spot

may occur)

• Rugged mature product• Relatively slow switch

• External commutation required

• Simple drive circuit


A simple gate drive circuit for a thyristor

• Line commutated

• No isolation

• Not very fine control

MAIN THYRISTOR

A

K

G

armatureof the motor

field coil

field coil

240V

BT101

BYX10

BYX10

270

W

5.6K

1K

W

16

F, 64V




GATE TURN-OFF (GTO)THYRISTOR


A K

G

• Keeping the benefits of thyristor• One way switch• Controlled turn-on capability• Controlled turn-off capability• Slower switching than BJT or IGBT• 3000 A, 4500 V , electric traction

applications (locomotives)

GTO THYRISTOR




A drive circuit for the GTO THYRISTOR

A

K

G

load

BTW58

R 1470

+13V to 18V

0V

R 2

82

L1

2

C1

470nF

T2

BD334

T1

BC635

AC

Drive circuit


TRIAC




TRIAC

i

i i

i

T2 T1

G

i g

i g

i g


T2 (+) and G (+)

T2 (+) and G (-)

T2 (-) and G (+)

T2 (-) and G (-)

T1 is reference

TRIAC

T2 T1

G




• Bidirectional current flow• No turn-off capability

• A positive or a negative gate signal

TRIAC

• As an AC mechanical switch

• (solid state relay)

• The average power control

• ON-OFF control or proportional

• control (temp.cont.)

APPLICATIONS :


A sample solid state relay circuit




POWER ELECTRONICDEVICES

TRANSISTORS:

a) BJT

b) MOSFET

c) IGBT)


TRANSISTORS AS A SWITCH

10 -1 10 0 10 1 10 2 10 4 10 5

Switching frequency (kHz)

Controllable

power

(kVA)

10 -1

10 1

10 2

10 3

10 4

MOSFET

BJT

IGBT

GTO

THYRISTOR

10 5

10 6

1990

2004




Application ranges of power switching devices


a) BIPOLAR JUNCTION TRANSISTOR

•One way controlled

turn-on and turn-off

• Current controlled

• Low on-resistance

• Low switching speed

•High power controlI

C= I

B

IE

= IB

+ IC

npnC

E

B




BJT Characteristics

Increasing

IB

VCE(+ For NPN

- For PNP)

IC(+ For NPN

- For PNP)

Cut-off region

Residual voltage

S a t u r a t i o n r

e g i o n

1

2


A Base Drive Circuit for the BJT

BJT andFree Wheeling DiodeDRIVE CIRCUITISOLATION CIRCUIT

+5V

-5V

27

370

2.4K 1K HCPL2200

CD4050

(1/6)optocoupler

0.1

F 2N3467

2N3725BC109

TIP162

+Vdc




b) MOSFET

•Usually three terminaldevices

•One way controlled

turn-on and turn-off

•Voltage controlled

•High switching speed

•High on-resistance

(in high power MOSFETs)

•Moderate power control

n channel

D

S

G

Id

Vds

Vgs


MOSFET transistor symbols

PE&DS Slide Group 2 2014

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