power semiconductor devices.ppt

8/18/2019 POWER SEMICONDUCTOR DEVICES.ppt

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POWER SEMICONDUCTOR

DEVICES


2/31

POWER SWITCHES

•

PE switches works in 2 states:1. On (short circuit)

2. Of (oen circuit)

• !"ications usin# switchin# is $esira%"e

%ecause o& re"ati'e" sa"" ower "oss inthe $e'ice.

• *or i$ea" switch: – when switch is oen+ no current ,ow in it –

when switch is c"ose$+ no 'o"ta#e $ro across it – Since ower is a ro$uct o& 'o"ta#e an$ current+ no "osses

occurs in the switch. – Power is 1-- trans&erre$ &ro source to "oa$.


3/31

/IO/E

• 0ncontro""a%"e switch : onof con$itions is$eterine$ % 'o"ta#es currents in the circuit.

• On : The $io$e is &orwar$ %iase$ (when the

current+ i/ ositi'e)

• Of : The $io$e is re'erse$3%iase$ (when '/ is

ne#ati'e)

• Re'erse reco'er tie+ trr is the tie re4uire$ &or

the $io$e to %e of its current %ecoe 5ero.


4/31

/IO/E CH!R!CTERISTIC

! Power Diode is use$ when a "ar#e current is in'o"'e$ which nee$s a"ar#er 6unction to $issiate the heat #enerate$. !n a$'anta#e o& usin#the Power /io$e is it is a%"e to withstan$ hi#h 'o"ta#e without %ein#$aa#e$. ! $isa$'anta#e a%out the Power /io$e is that %ein# a "ar#e

6unction it is una%"e to stan$ hi#h &re4uenc a"ications.


5/31

RE7ERSE RECO7ER8 TI9E IPOWER /IO/E

/naic characteristic o& a non3i$ea" $io$e is re'ersereco'er current.

When $io$e turns of+ the current in it $ecreases an$

oentari" %ecoes ne#ati'e %e&ore %ecoin# 5ero.

Tie trr is usua"" "ess than 1 ;s : this henoenon is

iortant to consi$er in hi#h3&re4 as. *ast reco'er $io$es $esi#ne$ to ha'e sa"" t rr

coare$ to the $io$es $esi#ne$ &or "ine3&re4uencas.

ora"" "essthan 1 ;sec


6/31

T8PES O* /IO/ES

•

2? ;s

3 use$ in "ow see$ a"ications (where trr is not

critica")

3 e# : $io$e recti@ers con'erters &or a "ow inut&re4uenc u to 1kH5 as.

3 co'er 'er hi#h current (u to ? k!) 'o"ta#e (?k7) ratin#


7/31

•

*ast Reco'er /io$e3 ha'e "ow reco'er tie+ nora"" A1 ;s

3 use$ in $c3$c $c3ac circuits+ where see$ reco'ero& o&ten critica" iortance

3 co'er 'er hi#h current+ 'o"ta#e (?-7 B k7)

• Schottk /io$e

3 eta"3to3si"icon %arrier

3 'er "ow &orwar$ 'o"ta#e $ro (-.7)

3 "iite$ (re'erse 'o"ta#e) %"ockin# 'o"ta#e (?-31--7)3 0se$ in "ow 'o"ta#e+ hi#h current a"ication such as

switche$ o$e ower su"ies

T8PES O* /IO/ES


8/31

TR!SISTORS B DIPO

• On3state is achie'e$ % ro'i$in# suFcient %ase currentto $eri'e the DT into saturation.

• Ratin# : 7o"ta#e (7CE A1---7)+ current (IC AG--!)+

switchin# &re4uenc (u to ? kH5)+


9/31

TR!SISTORS B DIPO

(d) Darlington connection


10/31

DT as a Switch 3 RecaP

! DT can %e use$ as a switchin# $e'ice in "o#ic circuits toturn on or of current to a "oa$. !s a switch+ the transistoris nora"" in either cutof ("oa$ is O**) or saturation("oa$ is O).

In cutoff, the transistor looks

like an open switch.

In saturation, the transistor

looks like a closed switch.

RB

0 V

RC I C = 0

+V CC

RC

C

E

+V CC

I B = 0 –

+ RB

RC I C(sat)

+V CC

RC

C

E

+V CC

I B

+V BB

I C(sat)


11/31

TR!SISTORS B 9OS*ET

•

9OS*ET is a 'o"ta#e3contro""e$ $e'ice can %e use$ in PEcircuits. Power 9OS*ET are the enhanceent te ratherthan the $e"etion te.

• ! suFcient "ar#e #ate3to3source 'o"ta#e wi"" turn the $e'iceon+ an$ when the 7=S is -7 it wi"" turn of.

•

In on3state+ the chan#e o& 7/C is "inear" roortiona" to thechan#e in i/. Thus+ the 9OS*ET can %e o$e""e$ as an on3state resistance R/C(on) (&ew i"iohs).

• 9OS*ET is otia" &or "ow3'o"ta#e oeration at hi#hswitchin# &re4uencies.

•

Ratin#s can %e u to 1?--7 ore than --!. Switchin#&re4uenc u to 9H5.

• 9OS*ET is $oinant in hi#h &re4uenc a"ications(J1--kH5). Di##est a"ication is in S9PS.


12/31

TR!SISTORS B 9OS*ET


13/31

TR!SISTORS B IS0

• I=DT is an inte#rate$ connection o& a 9OS*ET DT.

• I=DT circuit is sii"ar as &or 9OS*ET+ whi"e the onstate characteristics are "ike those o& the DT.

•


14/31

(a)E4ui'a"ent circuits

(%)Circuit s%o"s

TR!SISTORS B IS0


15/31

TH8RISTOR

•

Thristor are e"ectronic switches use$ in soe PEcircuits where the contro" switch on is re4uire$.

• Thristor is a terina" $e'ices inc"u$e the si"iconcontro""e$ recti@er (SCR)+ triac+ #ate turn3of thristor(=TO)+ 9OS3contro""e$ thristor (9CT).

• Thristor are caa%"e o& "ar#e currents an$ "ar#e%"ockin# 'o"ta#es &or use in hi#h3ower a"ication+%ut switchin# &re4uencies cannot %e as hi#h as whenusin# other $e'ices such as 9OS*ETs.


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• *or SCR to %e#in to con$uct+ it ust ha'e #atecurrent a"ie$ whi"e ositi'e ano$e3to3catho$e'o"ta#e.

• !&ter connection esta%"ishe$+ the #ate si#na" no"on#er re4uire$ to aintain the ano$e current.

• The SCR wi"" continue to con$uct as "on# as theano$e current reains ositi'e a%o'e theiniu 'a"ue ca""e$ the ho"$in# "e'e".

TH8RISTOR

TH8RISTOR


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(a) Si"iconcontro""e$

recti@er (SCR)(%) SCR i$ea"i5e$

i'characteristic

(c) =ate turn3-f

(=TO)($) Triac

(e) 9OS3contro""e$thristor (9CT)

TH8RISTOR


18/31

• =TO is turne$ on % a short3$uration #ate current i& the

ano$e3to3catho$e 'o"ta#e is ositi'e can %e turne$ ofwith a ne#ati'e #ate current which ake the $esi#n o&#ate $ri'e 4uite $iFcu"t. It has s"ow switchin# see$ itis use$ at 'er hi#h ower "e'e"s.

• Triac thristor is caa%"e o& con$uctin# current either ineither $irection. It is e4ui'a"ent to 2 antiara""e" SCRs.

• *or 9CT+ the &unction is e4ui'a"ent to =TO %ut without

hi#h turn of #ate current re4uireent. It has SCR 29OS*ET inte#rate$ in a $e'ice. It can %e turn on an$ of% esta%"ishin# the roer 'o"ta#e &ro #ate to catho$eas oose$ to esta%"ishin# #ate current to the =TO.

TH8RISTOR

S C S C O


19/31

• Se"ection o& ower $e'ice &or an a"ication is $een$s onthe re4uire$ 'o"ta#e+ current "e'e"s its switchin#characteristics.

• Transistors =TOs ro'i$e contro" o& %oth turn3on turn3of + SCR ro'i$e turn on %ut not turn of $io$es areneither.

• 9OS*ET has the a$'anta#e in switchin# see$ o'er DTsince it is a a6orit carrier stora#e $e"a.

•9OS*ET has "ower switchin# "osses coare$ to DT sinceit has shorter switchin# tie

• The switchin# $e'ice se"ection $een$s on the re4uire$oeratin# oint turn on turn of characteristics.

SWITCH SE


20/31

SWITCHES CO9P!RISO2---


21/31

SWITCHES

Power $io$e Thristors

Power os&et

Power DT

I=DT


22/31

• It is iortant to consi$er "osses o& ower switches:

3 To ensure that the sste oerates re"ia%" un$errescri%e$ a%ient consition.

3 Heat reo'a" echanis (e#. Heat sink+ ra$iators+ coo"ant)can %e seci@e$.

3


23/31

POWER SWITCH


24/31

*in te heat sink

SCR on the heat sink

HE!T SIKS


25/31

•

o current can ,ow when the switch is of+ an$when it is on+ current can ,ow in the $irection o& thearrow on".

• I$ea" switch has 5ero 'o"ta#e $ro across it $urin#turn on+ 7on. !"thou#h the &orwar$ current is "ar#e+

the "osses at the switch is 5ero.

• Dut &or rea" switches such as DT+ I=DT+ =TO+ SCRha'e &orwar$ con$uction 'o"ta#e which ischaracteri5e$ % the R/S (on)

*ORW!R/ CO/0CTIO


26/31

•


27/31

•

The ro$uct o& $e'ice 'o"ta#e current #i'esinstantaneous ower $issiate$ in the $e'ice.

• The heat ener# that $e'e"oe$ o'er the switchin#erio$ is the inte#ration (suation) o& instantaneous

ower o'er tie as shown % the sha$e$ area un$er theower cur'e.

• The a'era#e ower "oss is the su o& the turn3on turn3of ener#ies u"ti"ie$ with the switchin# &re4uenc.

• When the &re4uenc increase+ switchin# "osses increase. This "iits the usa%"e ran#e o& ower switches un"essroer heat reo'a" echanis is e"oe$.

*ORW!R/ CO/0CTIO D


28/31

SWITCHI=


29/31

S0DDER CIRC0IT


30/31

S0DDER CIRC0IT

L *ro re'ious e4uation+ the 'o"ta#e across the switch is

%i##er than the su" (&or a short oent).

L The sike a ecee$ the switch rate$ %"ockin# 'o"ta#ean$ causes $aa#e $ue to o'er'o"ta#e.

L To re'ent such occurrence+ a snu%%er is ut across theswitch. !n ea"e o& a snu%%er is an RC/ circuit.

L Snu%%er circuit Msoothene$N the transition an$ ake

the switch 'o"ta#e rise ore Ms"ow"N. In efect it $aensthe hi#h 'o"ta#e sike to a sa&e 'a"ue.

L DT switches an$ $io$es re4uires snu%%ers. Howe'er+ new#eneration o& I=DT+9OS*ET an$ =CT $o not re4uire it.


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RC/ S0DDER CIRC0IT

In #enera"+ snu%%ers are use$ &or:

Lturn3on: to inii5e "ar#e o'ercurrents throu#h the $e'ice at

turn3on

Lturn3of: to inii5e "ar#e o'er'o"ta#es across the $e'ice $urin#turn3of.

LStress re$uction: to shae the $e'ice switchin# wa'e&or such

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