‫بسم هللا الرحمن الرحيم‬
The Islamic University of Gaza
Faculty of Engineering
Electrical Engineering Department
POWER ELECTRONICS
EELE 5450 — Summer 2012
Instructor: Eng. Jalal Al Roumy
Lecture 5
Chapter Three
Thyristors
The SCR (Silicon-controlled rectifier) is the most important
member of the family of power semiconductor devices.
Chapter Three
Applications
Chapter Three
Thyristors family
There are other power semiconductor devices of the thyristor
family which share the latching characteristics of the SCR:
Triac.
Bidirectional diode switch.
Silicon controlled switch.
Silicon unilateral and bilateral switches( SUS,SBS).
Light activated devices Like LASCR and LASCS.
Complementary SCRs.
Programmable unijunction transistors( PUT).
Chapter Three
Thyristor (SCR)
When
theother
anode
voltage
isJ1made
with respect
toof
the
Since
If
the the
anode-to
cathode
junctions
voltage
andVpositive
J3
ak
is
areincreased
already
forward
todevice
a sufficiently
biased,
A Thyristor
(SCR)
is a four-layer
semiconductor
pnpn
cathode,
the
junction
J1junctions.
and J3junction
are
biased.
large
there
value,
will
be
the
reverse-biased
free pn
movement
of
carriers
Jthree
2 will
across
break. This
all:Anode
three
is
structure
with
three
Itforward
has
terminals
The
junction
J2 is reverse
biased,
andthe
small
leakage current
known
junction,
asresulting
avalanche
inbreakdown
a large
forward
and
anode
corresponding
current.
The
voltage
device
,Cathode,
Gate.
flows
to cathode.
( Forward
blocking off-state) ID
is
will
called
befrom
inforward
a anode
conducting
breakdown
state or
voltage
on-state.
VBO.
Chapter Three
If
The
thevoltage
anode
forward
current
anode
must
current
bedue
more
is to
reduced
than
a below
value
known
a level
as
known
The
drop
would
be
the ohmic
drop
in the
four as
SCR
(V-I
characteristics)
the
latching
holding
current
IL ,IH,
in
order
thyristor
to 1V.
maintain
will
blocking
required
state.
amount
layers
and
itcurrent
is small,
Typically,
Inbe
theinthe
on-state,
the
anode
When
of the carrier
Cathode
flowis
across
positive
the junction.
with
respect or
to aanode
current
is limited
by
an external
impedance
resistor(reverse
, RL.
blocking state) IR
Chapter Three
IG effects
End of Lecture