Types of Static Switches

7/21/2019 Types of Static Switches

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TYPES OF STATIC SWITCHES

Uncontrolled static switch-Power Diode

IA

A

K

VAK

IAK

trolled switchON and OFF by activating and deactivating a control circuit.

Turns On and OFF by itself depending on the polarity ofvoltage

ControlledElecromechanical

switch

Has !o"in# contacts $

%onstatic o&eartion

Controlled static switch(Power semiconductor

devices

C'

(

C

'

(

!nilateral "ilateral



Directional &ro&erties o) static switches

CU**E%T DI*ECTIO%S

•

Unidirectional Diode+ SC*+ I,T+ .T+ ,TO+ /CT• idirectional /OSFET+ *CT+ T*IAC

VO0TA,E CAPAI0ITY

• Forward "olta#e 1loc2in#

• *e"erse 1loc2in# 3Power diode4• oth )orward and re"erse 1loc2in# 3SC*4



TYPES OF SWITCHI%, CO%T*O0S

Static switches are classi5ed on the 1asis o) switchin# control as

A4 Contin6o6s switchin# control

) In so!e de"ice the t6rn on switchin# is i!&le!ented 17 an in&6t to thecontrol ter!inal+ this in&6t to 1e contin6e to 1e &resent+ to 2ee& theswitch in O% state8

) I) control in&6t sto&s+ the switch t6rns OFF8

) oth O% and OFF o&erations i!&le!ented 17 sa!e control circ6it

E9a!&les .T+I,T+ /OSFET

4 0atchin#

) Control in&6t to t6rn O% and or OFF need a short d6ration &6lse8

) Once O%+ it re!ains O% a)ter re!o"in# 3sto&&in#4 the control si#nal8

) To t6rn OFF short d6ration &6lse on its control ter!inal is #i"en

) De"ice is latched in re:6ired state 17 a &6lse o) short d6ration 2nown as

0atchin#8) E9& SC*+ ,TO



IDEA0 switchCharacteristics:

1. Controllable: able to turn ON or OFF at will. We prefer voltage control

over current control

2. Voltage blocking: blocks large voltages when OFF. Forward AN !everse.

". Current conduction: Conduct large currents when ON. Forward AN

!everse.

#. Fast Speed: $witch fro% ON to OFF or back &uickl' (instantl' preferred).*. Negligible losses: conduction losses and switching losses are negligible

+. Power for control source is negligible. ,oltage control does this far better

than current control.

-. Negligible deviation fro% true ON or OFF behaviour

a. eakage current in the OFF state is negligible b. Forward voltage in theON state is negligible

/. Positive temperature coefficient (!esistance rises the te%perature rise).

0his situation tends to contribute to circuit stabilit'.

. Large di/dt and dv/dt ratings. elps speed3



*e"iew o) Switchin# Conce&ts and Power Se!icond6ctorDe"ices

• The need )or switchin# in Power Electronic Circ6its

• Switchin# Characteristics

– The ideal switch

– The &ractical switch

•

Switchin# )6nctions and /atri9 re&resentation• T7&es o) Switches

• A"aila1le Se!icond6ctor Switchin# De"ices

– i&olar and Uni&olar De"ices

– Th7ristor-ased De"ices

• Co!&arison o) Switchin# De"ices

• F6t6re Trends in Power De"ices



Introd6ction

• Uni&olar and 1i&olar t7&e de"ices

– i&olar ;6nction transistor 3.T4

– /etal O9ide se!icond6ctor 5eld-e<ect transistors 3/OSFET4

– Ins6lated #ate 1i&olar transistor 3I,T4

–

Th7ristor-1ased de"ices – Silicon-controlled recti5ers 3SC*4

– ,ate t6rn-o< 3,TO4 th7ristor

– Triac

– Static Ind6ction transistor and th7ristor

–

/OS-controlled th7ristor 3/CT4• The e!&hasis will 1e on the de"ice ter!inal i-" switchin#

characteristics and their c6rrent+ "olta#e+ and switchin#li!its8



Power se!icond6ctor de"ices

re&resent the heart o) !odern&ower electronics+ with two !a;ordesira1le characteristics #6idin#

their de"elo&!ent

– Switchin# s&eed 3t6rn-on and t6rn-o<ti!es4

– Power-handlin# ca&a1ilities 3"olta#e-1loc2in# and c6rrent-carr7in#ca&a1ilities4



The Need For #witching $n PowerElectronic Circuits

• 0he need for se%iconductor devices to perfor% conversion

functions is related to the converter efficienc'• A low4efficienc' power s'ste% %eans that large a%ounts of

power are being dissipated in the for% of heat5 with one or %oreof the following i%plications:

–

0he cost of energ' increases due to increased consu%ption – Additional design co%plications %ight be i%posed5 especiall'

regarding the design of device heat sinks

– Additional co%ponents such as heat sinks increase the cost5si6e5 and weight of the s'ste%5 resulting in low power densit'

– igh power dissipation forces the switch to operate at lowswitching fre&uencies5 resulting in li%ited bandwidth and slowresponse5 and the si6e and weight of %agnetic co%ponents

– Co%ponent and device reliabilit' is reduced



E9a!&le (• The purpose of this example is to investigate the efficiency of four different

power electronic circuits whose function is to take power from a 24 V dc

source and deliver a 12 V dc output to a 6 Ω resistive load. In other words, the

task of these circuits is to serve as dc transformers with a ratio of 2:1. The four

circuits are shown in Fig. 2.1(a), (b), (c), and (d ), representing a voltage

divider circuit, zener regulator, transistor linear regulator, and switching

circuit, respectively. The objective is to calculate the efficiency of these four

power electronic circuits.

Fig %.& 3a4 Volta#e di"ider 314 =ener

re#6lator 3c4 Transistor re#6lator 3d4Switchin# circ6it

3c4

3a4

314

3d4



Fig %.& 3e4 =ener diode i-" switchin# characteristics 3)4 Switchin#

wa"e)or!s )or circ6its

3)4

3e4



Voltage divider dc regulator:

The first circuit is the simplest, forming a voltage divider with R = RL = 6 Ω and Vo = 12

V. The efficiency, defined as the ratio of the average load power, PL, to the average input

power, Pin , is

The efficiency is simply Vo/Vin%. As the output voltage becomes smaller, the efficiency

decreases proportionally.

Zener dc regulator:

Since the desired output is 12 V, we select a zener diode with zener breakdown VZ = 12 V

is selected. Assume the zener diode has the i-v characteristic shown in Fig. 2.1(e). Since

RL = 6 Ω , the load current, IL, is 2 A. Calculate R for IZ = 0.2 A (10% of the load current),

results in R = 5.45 Ω8 Since the input power is Pin = 2.2 A x 24 V = 52.8 W and the output

power is Pout = 24 W, the efficiency of the circuit is:

Sol6tion )or E9a!&le (

η =

= + =

P

P

R

R R

L

in

L

L

7

7 *87

7/.*2

2#

W

W =η

>?@8@



Transistor dc regulator:

It is clear from Fig. 2.1(c) that for Vo = 12 V, the collector emitter voltage must be

around 12 V. The control circuit must provide a base current, IB, to put the transistor in

the active mode with VCE ≈12 V. Since the load current is 2 A, the collector current is

approximately 2 A (assume small IB

). The total power dissipated in the transistor can be

approximated by the following equation:

The efficiency of the circuit is 50%.

Switching dc regulator:

Consider the switching circuit of Fig. 2.1(d) by assuming the switch is ideal and

periodically turns on and off, as shown in Fig. 2.1( f ). The output voltage waveform is

also shown in Fig. 2.1( f ). Even though the output voltage is not constant or pure dc, its

average value is given by

where D is the duty ratio, the ratio of the on-time to the switching period, Ts. For Vo,ave =

12 V, set D = 0.5, i.e., the switch has a duty cycle of 0.5 or 50%. In this case, the average

output power is 48 W and the average input power is also 48 W, resulting in 100%

efficiency

P V I V I diss CE C BE B= +

5



Switchin# CharacteristicsThe $deal #witch

• %o li!it on the a!o6nt o) c6rrent 32nown as )orward or re"ersec6rrent4 that the de"ice can carr7 when in the cond6ction state 3on-

state4• %o li!it on the a!o6nt o) de"ice "olta#e 32nown as )orward or

re"erse 1loc2in# "olta#e4 when the de"ice is in the noncond6ctionstate 3of -state4

• =ero-on state "olta#e dro& when in the cond6ction state

•

In5nite of -state resistance+ i8e8+ Bero lea2a#e when in the non-cond6ction state

• %o li!it on the o&eratin# s&eed o) the de"ice when it chan#es statei8e8+ Bero rise and )all ti!es



The Practical Switch

• 0i!ited &ower-handlin# ca&a1ilities+ i8e8+ li!itedcond6ction c6rrent when the switch is in the on state+ andli!ited 1loc2in# "olta#e when the switch is in the of -state8

• 0i!ited switchin# s&eed+ ca6sed 17 the 5nite t6rn-on andt6rn-o< ti!es+ which li!its the !a9i!6! o&eratin#)re:6enc7 o) the de"ice

• Finite on-state and of -state resistances i8e8+ the e9istenceo) )orward "olta#e dro& in the on state+ and re"ersec6rrent ow 3lea2a#e4 in the o<-state

• eca6se o) characteristics ' and + the &ractical switche9&eriences &ower losses in the on and of states andd6rin# switchin# transitions



Fig %.' 3a4 Practical switch c6rrent+ "olta#e+ and

wa"e)or!s

3a4



A 6se)6l &lot that ill6strates how switchin# ta2es &lace )ro! onto o< and "ice "ersa is called a switchin# tra;ector7+ which issi!&l7 a &lot o) isw "ers6s "sw as shown here

Fig %.' 314 Switchin# tra;ector7

314



E9a!&le '

• Consider a linear a&&ro9i!ation o) Fi#'83a4 as shown in Fi# '8?3a4 with D > (3this ass6!es that Ts is the on ti!e4

–

,i"e a &ossi1le circ6it i!&le!entation 6sin# a&ower switch whose switchin# wa"e)or!s areas shown in Fi# '8?3a4

– Deri"e the e9&ressions )or the instantaneo6sswitchin# and cond6ction &ower losses and

s2etch the! – Deter!ine the total a"era#e &ower dissi&ated

in the circ6it d6rin# one switchin# &eriod

– Find the !a9i!6! &ower



Fig %. 3a4 0inear a&&ro9i!ation o) t7&ical c6rrent and "olta#eswitchin# wa"e)or!s 314 Circ6it i!&le!entation 3c4

Instantaneo6s &ower wa"e)or!s

3a4

314

3c4



314 The instantaneo6s c6rrent and "olta#e wa"e)or!s

( )

( )

≤≤−+−−

−

−≤≤

≤≤+−

=

sOFF sOFF OFF ON

OFF

s

OFF sON ON

ON OFF OFF ON

ON

sw

T t t T I I I t

T t

t T t t I

t t I I I t

t

t i

8

)(

( )

( )

≤≤−+−−

−−≤≤

≤≤+−−

−

=

sOFF sON OFF OFF

ON OFF

OFF sON ON

ON ON ON

ON

ON OFF

sw

T t t T V t Tst t

V V

t T t t V

t t V t t t

V V

t v

)(

8

)(

It can 1e shown that i) Ion Io< and Vo< Von

( )

( ) ( )

≤≤−−−−−

−≤≤

≤≤−−

=

sOFF s sOFF

OFF

ON OFF

OFF sON ON ON

ON ON

ON

ON OFF

T t t T T t t Tst

t

I V

t T t t I V

t t t t t t

I V

t p

)(

8

)(

2

2

Sol6tion )or E9a!&le '3a4 When the switch is of + the 1loc2in# "olta#e across the switch is VOFF+

which can 1e re&resented as a DC "olta#e so6rce o) "al6e VOFF reectedso!ehow across the switch d6rin# the of -state



Switchin# F6nctions and /atri9

*e&resentation

The s7ste! 1elow has n in&6ts and m o6t&6ts that can1e either "olta#es or c6rrents8 There are n 9 m switches



E9a!&les o) &ower electronic circ6its 3a4 Sin#le-&hase

3a4



E9a!&le

• Given that vs(t) is a triangular waveform, assume the switch is ideal

and initially off. Control works in such a way that it toggles every

time vs(t ) crosses zero. Use Vp = 12 V, R = 10Ω and T = 1 ms.

a4 S2etch the wa"e)or!s )or is and "o

14 Calc6late the a"era#e and r!s "al6es )or the o6t&6t"olta#e

c4 Calc6late the a"era#e in&6t &ower+ a"era#e o6t&6t&ower+ and eGcienc7

d4 *e&eat &arts 3a4-3c4 17 ass6!in# T > ( µs

e4 *e&eat &arts 3a4-3d4 17 ass6!in# the switch has ( V

"olta#e dro& was closed



Sol6tion )or E9a!&le

• The o6t&6t "olta#e and the so6rce c6rrent wa"e)or!are shown in Fi#8 '8314

Fi# '8 314



314 The a"era#e o6t&6t "olta#e

V V

V T

T

dt t v

T

V P

P

T

"

#

)

22

1(

1)(

1

8

88 ====

∫ The rms is

V V

V p

rms .#+

58 ≈=

The a"era#e in&6t &ower is calc6lated )ro!+

W dt t vt iT

P

T

s sin #.2)()(1

8

== ∫

∫ ==

T

out W dt t vt i

T

P

8

88 #.2)()(1

7188== inout P P η

The a"era#e o6t&6t &ower+

EGcienc7



Sa!e as a1o"e 31eca6se the res6lts are inde&endent o) T4The a"era#e o6t&6t "olta#e can 1e a&&ro9i!ated 17 the )ollowin# inte#ration+

V V

dt V t T

V dt V t

T

V

T dt t V

T V

p

T

T

T

T

p

p

p

pT

ave

*.2)2(#

1

1"#

1#1

)(1

2

#

#"

28

858

=−=

−+

−+

−−== ∫ ∫ ∫

And the rms "olta#e is

V dt t V T

V

T

orms ".#)(1

8

2

58 == ∫

It can 1e shown that the a"era#e in&6t &ower is+

W V

R

dt t vt iT

P

p

s

T

sin

"-*.21"

2

#

1

)()(1

2

8

=

−=

= ∫

and the a"era#e o6t&6t &ower+

( )( ) W V RV

dt t vt iT

P

p

p

o

T

oout

/*.111+

1

)()(1

"

8

≈+−=

= ∫

*es6ltin# in eGcienc7 o)

7.--7188;"-*.2

/*.17188; ≈==

in

out

P

P η



T7&es o) Switches

Ta1le '8( T7&es o) Se!icond6ctor Switches+ theirControlla1ilit7 Feat6res+ and their Possi1le SwitchI!&le!entations8



A"aila1le Se!icond6ctor Switchin#De"ices

• i&olar and Uni&olar De"ices

– Power diodes

– i&olar ;6nction transistors

– Ins6lated #ate 1i&olar transistors 3I,Ts4

–/etal o9ide se!icond6ctor 5eld-e<ect transistors3/OSFETs4

• Th7ristor-ased De"ices

– Silicon-controlled recti5ers 3SC*s4

– ,ate t6rn-o< 3,TO4 th7ristors

– Triode ac switches 3triacs4

– Static ind6ction transistors 3SITs4 and th7ristors 3SITHs4

– /OS-controlled th7ristors 3/CTs4



i&olar and Uni&olarDe"ices

• The Power Diode

• Power diodes ha"e i!&ortant )eat6res

– Power-handlin# ca&a1ilites

– Incl6din# )orward c6rrent carr7in# and re"erse"olta#e 1loc2in#

– *e"erse reco"er7 ti!e 3trr4 at t6rn-o<

Fig %.) S7!1ol and Practical and Ideal i-" characteristic c6r"es

3a4 314 3c4



• *e"erse reco"er7 c6rrent I**

• Dela7 t( and t' is d6e to the !inorit7 carriers in

the de&letion re#ion

• Dela7 t' and t is ca6sed 17 the char#e stored

in the 16l2 o) the se!i-cond6ctor !aterial

• *e"erse reco"er7 char#e rr

• *atio 1etween 3t-t'4 and trr is a diode

sna&&iness

Fig %.* T7&ical diode switchin# characteristics 3a4

Switchin# circ6it with S closed at t > to 314 Diode c6rrent

3a4 314



E9a!&le '8?

Deri"e the e9&ression )or I** and

the &ea2 switch c6rrent in ter!s o)

the diode re"erse reco"er7 ti!e )orFi#8 '8(J8

Fig %.&+ Diode switchin# circ6it with &arasitic ind6ctor



When the switch is closed at t>tJ+ the diode "olta#e re!ains Beroand its c6rrent is #i"en 17+

iD > IJ-is

and is )or t ≥ t

J is #i"en 17+

s

n

s

= −

At t > t( the diode c6rrent 1eco!es Bero and i

s 1eco!es I

J8 Hence

the inter"al t(-tJ is #i"en 17+

in

so

V

L I t t =− 81

Since t-t

'≈J+ then t

'-t

(≈t

rr and I

** is #i"en 17+

rr

s

in

RR t L

V

I =

&ea2 switch c6rrent occ6rs at t > t' when i

D> -I

** and is #i"en 17+

5

Sol6tion )or E9a!&le '8?



The i&olar .6nction Transistors3.T4

• The sche!atic s7!1ol and i-" characteristics)or the 1i&olar ;6nction transistors 3.T4 areshown in Fi#8 '8((3a4+ 314+ 3c4

Fig %.&& .T switchin# characteristics 3a4 n&n transistor

314 Ideal I-" characteristics 3c4 Practical I-" characteristics

3a4 314 3c4



Fig %.&' Switchin#characteristics )or the .T3a4 Circ6it 314 Switchin#

wa"e)or!s

3a4

314

i t # it hi (, i Ch t i ti



ansistor #witching (,ynamic Characteristic

Transient /odel o) .T



The Power /OSFET

Unli2e the 1i&olar ;6nctiontransistor+ /OSFET 1elon#s to theunipolar device )a!il78 Fi# '8(@

shows a"aila1le de"ices

Fig %.&- /OSFET de"ice s7!1ols3a4 n-channel enhance!ent-!ode 314 &-channel enhance!ent-

!ode3c4 n-channel de&letion-!ode 3d4 &-channel de&letion-!ode

3a4 314 3c4 3d4



Fig %.& 3a4 n-channel enhance!ent-!ode /OSFET and

314 its iD "s8 "DS characteristics

3a4 314



On-State*esistance

)(

2

5 on D Ddisson R I P =

$nternal "ody ,iode

The !odern &ower /OSFET has an internal diode called a1od7 diode connected 1etween the so6rce and the drain

Fig %.&) 3a4 /OSFET internal 1od7 diode 314 I!&le!entation o) a)ast 1od7 diode

3a4 314

/OSFETS ha"e on-state resistance+ *DS

3sw4+ that ca6se

&ower dissi&ation as



Internal Ca&acitors

•

Parasitic ca&acitances 1etween the de"ices three ter!inals – ,ate-to-so6rce 3C#s4

– ,ate-to-drain 3C#d4

– Drain-to-so6rce 3Cds4

• De"ices data sheet &ara!eters Ciss+ Coss+ and Crss

C#d > Crss

C#s > Ciss L Crss

Cds > Coss L Crss

where+

Crss > s!all-si#nal re"erse trans)er ca&acitance

Ciss > s!all-si#nal in&6t ca&acitance with the drain and so6rce ter!inals shorted

Coss > s!all-si#nal o6t&6t ca&acitance with the #ate and so6rce ter!inals shorted

Fig %.&* 3a4 E:6i"alent /OSFET re&resentation incl6din# ;6nctionca&acitances 314 *e&resentation o) this &h7sical location

3a4 314



*e#ions o) O&eration

• For ",S V Th+ the de"ice can 1e either in the

triode re#ion+ called Mconstant resistanceM re#ion+or in the sat6ration re#ion+ de&endin# on the"al6e o) "DS8 For a #i"en ",S+ with a s!all "DS 3"DS

N ",S - V Th4 the de"ice o&erates in the triodere#ion 3sat6ration re#ion in the .T4+ and with alar#e "DS 3"DS ",S - V Th4+ the de"ice enters the

sat6ration re#ion 3acti"e re#ion in the .T48

• For ",S

N V Th

+ the de"ice t6rns o<+ with the drain

c6rrent al!ost e:6al to Bero8 Under 1oth re#ionso) o&eration+ the #ate c6rrent is al!ost Bero8/OSFET is 2nown as a "olta#e-dri"en de"ice and+there)ore+ re:6ires a si!&le #ate control circ6it8



The drain c6rrent+ iD+ can 1e !athe!aticall7

a&&ro9i!ated as )ollows

=

−=

−−=

L

W C !

V v ! i

vvV v ! i

OX n

T"# D

D D T"# D

µ 21

2

2

.)(

<)(2= Triode *e#ion

Sat6ration *e#ion

whereµn electron !o1ilit7

CO o9ide ca&acitance &er 6nit area

0 0en#th o) the channelW Width o) the channel

Fig %.%& 0ar#e-si#nal e:6i"alentcirc6it !odel



/OSFET o6t&6t resistance can 1e e9&ressed as )ollows

)(18

T"# V vk

r −=

λ

Fig %.%% /OSFET characteristic c6r"e incl6din# o6t&6t resistance



Fig %.% S!all-si#nal e:6i"alent circ6it incl6din# /OSFET

o6t&6t resistance

Fig %.%' 0ineariBed iD "s8 ",S c6r"e with o&eratin# dc

&oint 34



In&6t Ca&acitance

• /OSFET has two li!itations

– Hi#h in&6t #ate ca&acitances

– Transient$dela7 d6e to carrier trans&ort thro6#h the dri)tre#ion

•

Usin# the /iller theore!+ the total in&6t ca&acitance+ Cin+1etween the #ate and so6rce is+

Fig %.%- 3a4 S!all-si#nal e:6i"alent circ6it incl6din#

&arasitic ca&acitances 314 A&&l7in# the /iller theore!

$d Lm $sin C R $ C C )1( ++=



Sa)e O&eration Area

• The sa)e o&eration area 3SOA4 o) a de"ice&ro"ides the c6rrent and "olta#e li!its the de"ice!6st handle to a"oid destr6cti"e )ail6re

Fig %.%/ Sa)e o&eration area )or a /OSFET



Th7ristor-ased De"ices

• The Silicon-Controlled *ecti5er

– S7!1ol and i-" characteristics )or the SC*

Fig %.'& SC* switchin# characteristics8 3a4 S7!1ol8 314 i-v

characteristics8 3c4 Ideal switchin# characteristics8

Th , t T < Th i t



The ,ate T6rn-o< Th7ristor3,TO4

• The sche!atic s7!1ol and the &ractical andideal switchin# i-" characteristics )or the #atet6rn-o< th7ristor 3,TO4 are shown

Fig %.' ,TO switchin# characteristics8 3a4 S7!1ol8 314 i-v

characteristics83c4 Ideal switchin# characteristics8

3a4

314 3c4



The Triode AC Switch 3Triac4

•

Triode ac – 0i2e the ,TO+ the triode ac 3triac4 switchin# de"ice was

introd6ced i!!ediatel7 a)ter the SC*

• The Diac

– Is essentiall7 a #ateless triac constr6cted to 1rea2 down atlow )orward and re"erse "olta#es

Fig %.'/ Triac switchin# characteristics8 3a4 E:6i"alent re&resentation6sin# two SC*s8 314 S7!1ol8 3c4 i-v characteristics8 3d4 Ideal switchin#

characteristics8



The Ins6lated ,ate i&olar Transistor 3I,T4

• The si!&li5ed two-transistor circ6it !odel+ andthe sche!atic s7!1ol )or the ins6lated #ate1i&olar transistors 3I,T4 are shown 1elow

Fi# '8J 3a4 I,T e:6i"alent circ6it+ 314 si!&li5ed

e:6i"alent circ6it+ and 3c4 s7!1ol

3a4 314 3c4

S i d i i d



Static Ind6ction Transistors and Th7ristors

– Static ind6ction transistor 3SIT4

– Static ind6ction th7ristor 3SITH4

Fig %.') 3a4 SIT s7!1ol8 314 SITH s7!1ol8

3a4 314

Two di<erent t7&es

The /OS Controlled



The /OS-Controlled Th7ristor

• Si!&li5ed e:6i"alent circ6it !odel and thesche!atic s7!1ol )or a p-t7&e /OS-controlledth7ristor 3/CT4

Fig %.'* /CT switchin# characteristics8 3a4 E:6i"alentcirc6it8 314 &-/CT s7!1ol8 3c4 Ideal switchin#

characteristics8 3d4 n-/CT s7!1ol8

3a4 314 3c4 3d4

Co!&arison o) Power



Co!&arison o) PowerDe"ices



Fig %.+ Fre:6enc7 "ers6s &ower ratin# ran#es )or "ario6s

&ower de"ices8



Sn611er Circ6its

•

To relie"e switches )ro! o"erstress d6rin# switchin#+switchin# aid circ6its+ 2nown as snubber circuits

• The o1;ecti"es o) sn611er circ6its are

– *ed6cin# the switchin# &ower losses in the !ain&ower de"ice in the &ower electronic circ6it

–

A"oidin# second 1rea2downs – Controllin# the de"ices dv $dt or di$dt

Fig %.& Passi"e sn611er

3a4 314

Types of Static Switches

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