00:00:00.080
hi this continuation for power
00:00:01.680
electronics lectures and today we are
00:00:03.760
going to continue
00:00:04.799
talking about transistors in the
00:00:07.200
previous video we have
00:00:09.200
spoken about bgt transistors
00:00:12.320
and what are the differences between um
00:00:15.519
the normal transistors and the power
00:00:17.680
transistors
00:00:18.720
and then we can throw some more details
00:00:21.199
and today we are going to
00:00:22.800
discuss the mosfet transistors
00:00:24.800
especially the power
00:00:26.400
and mosfet transistors so as we know
00:00:29.279
from electronics fundamentals that the
00:00:31.279
mosfet in general they are voltage
00:00:33.840
controlled devices we don’t need to push
00:00:36.960
current
00:00:37.680
into the gate to make it on like the vgt
00:00:41.200
transistors
00:00:42.079
so we have three terminals for the
00:00:44.480
mosfets
00:00:45.200
which is the gate and the drain and the
00:00:48.399
source
00:00:48.879
and we have two types which are
00:00:50.559
n-channel and p-channel mosfet
00:00:52.800
and from the background i think we know
00:00:55.039
that the mosfet is available as
00:00:57.039
a in depletion type or enhancement type
00:01:00.800
but the most popular one and common now
00:01:03.199
is the enhancement type so that’s why
00:01:05.360
i’m going to focus on enhancement type
00:01:08.400
mosfets so the relation between
00:01:12.080
the vgs which is the voltage between the
00:01:14.799
gate and source
00:01:16.000
and the current look like this okay we
00:01:19.119
have this curve
00:01:20.080
which describing the voltage i’m
00:01:22.080
applying
00:01:23.200
across the gate and source okay
00:01:26.240
and the relation with the current going
00:01:28.640
through that
00:01:29.360
mosfet between drain and source so
00:01:32.799
it’s different from the bgt transistor
00:01:35.200
where i need
00:01:36.000
to push current to make current between
00:01:38.560
collector and emitter we have here to
00:01:40.640
apply some
00:01:41.680
voltage between gate and source okay to
00:01:44.799
make
00:01:45.360
current uh passing through the
00:01:48.159
transistor from the drain to the source
00:01:50.399
and there is very important point which
00:01:52.880
is
00:01:53.680
the voltage i’m applying is between the
00:01:55.759
gate and the source
00:01:57.119
not the gate and the ground because we
00:02:00.159
sometimes have some circuits
00:02:01.920
the ground is far away from the source
00:02:04.000
and maybe you have your load or another
00:02:06.560
a component between the source and
00:02:08.239
between the ground so when you apply
00:02:10.160
your voltage you have to make sure that
00:02:12.000
you are applying between
00:02:13.360
the gate and the source and the voltage
00:02:16.000
between the gate and
00:02:16.879
the source has something threshold and
00:02:18.800
that threshold is
00:02:20.239
mentioned in the data sheet and it’s uh
00:02:23.360
it depends on the structure and the type
00:02:25.760
of the mosfet and the power
00:02:27.520
and current ratings so we have in this
00:02:30.000
example definition is about
00:02:31.959
2.2 voltage or 2.5 voltage and after
00:02:35.519
that
00:02:36.080
now raising the vgs the current go more
00:02:40.319
and more and more and more
00:02:41.599
the relation between the vgs and the
00:02:44.239
current
00:02:44.959
is determined by the this slope which is
00:02:48.480
there the
00:02:49.440
rds on reciprocal so the relation
00:02:52.480
between that current and that voltage
00:02:54.640
is determined by the rds on which is
00:02:58.400
also mentioned
00:02:59.519
in the data sheet so mosfet can be
00:03:02.239
easily modeled as a resistance
00:03:04.080
rds on between the drain and the source
00:03:06.800
so it’s capable of
00:03:08.080
bi-directional current flow and this is
00:03:10.319
very important point
00:03:11.680
so the mosfet by this way okay it can
00:03:15.519
pass the current from the drain to the
00:03:17.360
source and
00:03:18.720
from the source to the drain it’s
00:03:20.640
different from the bgt where we have
00:03:22.959
just from the cooling 30 emitter if it’s
00:03:25.280
np and transistor
00:03:26.799
it doesn’t uh allow the current to flow
00:03:29.840
from the emitter
00:03:31.200
to the collector and this is good
00:03:33.680
feature for the mosfet in some circuits
00:03:35.840
like
00:03:36.159
inverters so now we have n channel and p
00:03:39.120
channel but
00:03:39.840
which one is more popular in our
00:03:42.799
circuits is the n channel and the reason
00:03:44.959
behind it is
00:03:46.560
is it cheaper uh compared with the p
00:03:49.680
channel with the same ratings and also
00:03:52.400
it has
00:03:53.200
very low uh rds on resistance
00:03:57.920
uh during the on time compared with a
00:04:01.360
pitch and a p
00:04:02.080
channel sometimes has uh three times or
00:04:05.120
four times
00:04:05.920
are the s on if we compare it with the n
00:04:08.480
channel
00:04:08.959
so that’s why they don’t prefer to use p
00:04:11.840
channel
00:04:12.640
in the circuits it has one or two
00:04:16.880
advantage when you drive it in high side
00:04:19.279
which we will
00:04:20.238
discuss later but the ant channel is
00:04:23.199
more popular to use
00:04:24.560
and if we look at the structure of the
00:04:26.560
mosfet again
00:04:28.080
we have a little bit different structure
00:04:30.160
like the
00:04:31.280
diodes and transistors they have a
00:04:33.680
different regions with different
00:04:35.360
turbine uh percentage here so we have
00:04:38.240
here
00:04:38.560
and positive and then pre and then n
00:04:41.120
negative
00:04:41.759
and then n possessive and we have here
00:04:43.759
the source
00:04:44.800
okay and the gate and here we have the
00:04:47.520
drain
00:04:48.000
okay but this region here which is
00:04:52.000
s i o two it’s like a direct lick region
00:04:55.520
like insulator that’s why we don’t have
00:04:58.240
a
00:04:58.880
an electric contact between the gate and
00:05:02.080
the other pn junction
00:05:05.440
inside the mosfet and if you look deeply
00:05:09.039
into this structure
00:05:10.400
you have n p and n
00:05:14.240
you have also p and n what does it mean
00:05:18.160
it means that we have inside the mosfet
00:05:21.440
we have
00:05:22.000
other structures for other components
00:05:24.960
like
00:05:25.600
pgt transistor and like diodes
00:05:29.280
so that’s why it this structure has
00:05:32.560
inherently and has parasitic components
00:05:36.080
and one of the main parasitic components
00:05:38.479
is that deut
00:05:39.680
we have look at the this junction we
00:05:41.840
have p
00:05:43.120
and n negative and and positive what
00:05:45.840
does this
00:05:46.720
remind you i think this is the same
00:05:49.039
structure as the power div
00:05:51.039
okay so we have inside the mosfet
00:05:53.600
parasitic diode
00:05:54.800
and that there is a is is reversed there
00:05:58.720
so we have the symbol sometimes
00:06:01.199
is like this so we have this body that
00:06:03.280
is it drawn
00:06:04.479
from the source to the drain like that
00:06:06.880
okay so that one
00:06:08.400
is not intentionally made but it is a
00:06:11.759
parasitic one we have also another
00:06:14.000
structure here as well which is
00:06:15.600
n p n what is np and
00:06:18.800
it’s a transistor but that transistor
00:06:21.199
has been cancelled
00:06:22.720
when they short this pn junction by a
00:06:25.919
metal
00:06:26.639
okay so that one here is shorted
00:06:30.560
and they cancel that a npn transistor
00:06:33.680
and the one that is kept is the uh
00:06:37.360
p and junction here which is uh a power
00:06:40.560
diode and this picture here shows that
00:06:42.560
terminals of
00:06:44.319
an example a mosfet we have a gate drain
00:06:47.919
and source and we have that metal
00:06:49.840
which is the body one is drain terminal
00:06:52.319
as well
00:06:52.960
and we have a very important question
00:06:55.280
which is is there any problem with this
00:06:57.599
plastic
00:06:58.400
diode inside the mosfet the main problem
00:07:01.360
is
00:07:01.840
it has very long reverse recovery time
00:07:05.360
that means if we have a circuit that we
00:07:07.759
need to switch
00:07:08.720
off the mosfet that diode here
00:07:12.960
try to pass the current for a short time
00:07:15.680
which
00:07:16.000
is the reverse recovery time through the
00:07:19.440
mosfet
00:07:20.240
through the data inside the mosfet and
00:07:22.240
that sometimes
00:07:23.440
makes some problem for some structures
00:07:25.599
so that’s why we will study this
00:07:27.440
maybe in in later circuits but keep in
00:07:29.680
mind that
00:07:30.560
this has a long reversible time and
00:07:33.919
and sometimes to deal with this they
00:07:37.360
they have to provide another day
00:07:39.360
externally
00:07:40.400
with lower voltage and higher speed just
00:07:42.880
to make
00:07:43.520
a replacement of that build and now as
00:07:46.400
before we have to discuss the
00:07:48.479
switching power mosfets and because of
00:07:51.440
the structure of the mosfet and there
00:07:53.360
are some insulations
00:07:54.639
and some dielectric we make also
00:07:57.199
parasitic capacitors
00:07:58.879
so for example we have a capacit small
00:08:00.960
capacitance between the drain
00:08:02.560
and the gate and between the gate and
00:08:04.720
the source and also between the drain
00:08:06.800
and the source okay and when we switch
00:08:09.440
on
00:08:09.840
and off this mosfet here we have to
00:08:13.520
just put in mind that these
00:08:16.639
voltages and these currents pushed into
00:08:19.199
the mosfet
00:08:20.080
they have to charge these capacitance
00:08:22.720
during the switching time
00:08:24.560
okay and that makes sometimes problems
00:08:28.319
to the most with and how we drive it and
00:08:30.479
that’s why we have to
00:08:32.479
select some drivers uh carefully to
00:08:35.679
satisfy the mosfets and the capacitance
00:08:38.799
appearing at the terminals of these
00:08:41.120
mosfets
00:08:42.000
and now for example we have here a
00:08:44.640
switching
00:08:45.680
diagram we have off time and then we
00:08:48.800
applied some voltage here
00:08:51.839
at the gate and that voltage we
00:08:55.760
mentioned before that there is
00:08:57.279
insulation here and there is no current
00:08:59.120
will go to the
00:09:00.240
gate yes there is no current will go to
00:09:02.320
the structure there
00:09:03.760
but because of the capacitance there is
00:09:06.720
current will go through the
00:09:08.320
parasitic capacitance appearing between
00:09:10.880
the terminals
00:09:11.920
and practically we have to see some
00:09:15.040
current going through there
00:09:16.640
just to charge these capacitors because
00:09:19.360
without
00:09:19.920
charging these capacitors we are not
00:09:21.760
going to pass
00:09:23.120
the v threshold and turn on our mosfet
00:09:26.560
so for example now we applying here um
00:09:31.360
a pulse okay and we have that a turn
00:09:34.800
on edge as it’s shown here what happens
00:09:38.000
when we
00:09:38.560
giving a turn on edge there’s current
00:09:40.880
will go to
00:09:41.839
started charging this mosfet which is
00:09:44.480
the between the gate and the source
00:09:46.720
and it’s like charging any capacitor the
00:09:49.920
voltage will grow smoothly okay
00:09:53.040
until we pass the something called v
00:09:56.160
threshold and that v threshold with it’s
00:09:59.040
the value that
00:10:00.399
will the current will start passing
00:10:02.959
between the
00:10:05.920
drain and source so when i reach this
00:10:08.880
point now
00:10:10.320
the drain will open a little bit
00:10:13.680
and the current will start flowing
00:10:16.399
between the drain
00:10:17.440
and the source and at that time the
00:10:20.720
voltage between
00:10:21.680
and the source will now start to drop
00:10:24.399
okay
00:10:25.040
so now at that threshold exactly we have
00:10:28.320
a drop in voltage between the drain and
00:10:30.399
the source and also flow of current
00:10:33.440
so what happens later because the drain
00:10:36.320
now
00:10:36.800
start to uh to to
00:10:40.000
drop the voltage between between it and
00:10:43.120
between the source so
00:10:45.360
for example we have hundred volt between
00:10:47.200
the transfers in the off time
00:10:49.040
but we in the on time process now the
00:10:51.839
voltages
00:10:52.480
start to drop drop the drop drop between
00:10:54.800
the drain and the source as
00:10:56.880
as we see here that means this terminal
00:10:59.920
of that capacitor now
00:11:02.000
is going is going is going to be
00:11:05.360
at this point at that point eventually
00:11:07.760
so what happened next
00:11:09.839
actually we can simulate and model
00:11:12.880
what’s happening in this process here
00:11:15.920
by paralleling these capacitors that
00:11:18.800
means
00:11:19.279
instead of charging one capacitor during
00:11:22.320
the
00:11:22.640
on time we will see another capacitor is
00:11:27.040
included
00:11:28.000
okay and that capacitor is not small is
00:11:30.320
also big
00:11:31.440
and that will make the charging
00:11:35.360
uh like like stable here okay and there
00:11:38.079
is no voltage will go
00:11:39.680
grow okay and that um
00:11:42.959
a flat edge is called the plateau okay
00:11:46.160
and that’s called because of the miller
00:11:48.480
capacitance and miller
00:11:50.240
effect okay so that capacitor here will
00:11:52.959
look like
00:11:53.760
big capacitor during this transition and
00:11:56.639
the
00:11:57.200
current needed to charge one capacitor
00:11:59.680
now we have to charge
00:12:01.680
two capacitors now okay so that’s why
00:12:04.240
now we
00:12:06.000
will see a turn on okay edge
00:12:09.040
and then a flat edge and then after
00:12:12.079
start discharging this capacitor from
00:12:15.120
the previous
00:12:15.920
charge and then recharge it with a new
00:12:18.800
charge from the gate
00:12:20.320
so it spends some time and then we’ll
00:12:23.600
charge it again to the value that we
00:12:26.240
need okay
00:12:27.120
so the process of of switching on the
00:12:29.839
mosfet and the gate of the mosfet
00:12:31.600
has a three parts which is the v
00:12:34.560
threshold
00:12:35.440
and then the plateau and this edge now
00:12:38.079
is called the gate blatant
00:12:39.760
voltage and then completing the
00:12:43.279
the charging process or turning on the
00:12:45.920
mosfet
00:12:46.800
and this is the process for the for
00:12:50.320
switching on the mosfet and when we look
00:12:52.560
at the charges we
00:12:53.920
spending and we have to push into the
00:12:56.720
gate
00:12:57.440
to charge the phase capacitance and that
00:13:00.480
second capacitance also it has
00:13:02.720
this a waveform so this is the charge
00:13:05.839
axis
00:13:06.320
and this is the vgs axis so the voltage
00:13:10.000
will grow if i pushed more charges and
00:13:13.120
this is known
00:13:14.240
in the capacitance okay so we have zero
00:13:16.560
charge here okay
00:13:17.839
there is nothing pushed but once you
00:13:20.079
turn on you start pushing some charges
00:13:22.160
with
00:13:22.480
which is uh relevant to that current you
00:13:25.519
you are pushing and this charge now is
00:13:28.480
just responsible
00:13:29.920
to be charging this capacitor and later
00:13:33.519
on because
00:13:34.240
the turning on make that drain go and
00:13:37.519
drop a drop
00:13:38.240
to the source point here so we have to
00:13:41.760
a charge also that capacitance and that
00:13:45.040
also needs some time so that’s why we
00:13:48.079
have
00:13:48.480
the flat plateau uh edge here which is
00:13:51.920
miller plateau and then we complete the
00:13:54.560
charge so
00:13:55.519
that the charge is called the aqs
00:14:00.720
charge okay and this charge
00:14:04.399
is responsible to complete that charging
00:14:07.600
process
00:14:08.320
but with the g e d
00:14:11.920
charge okay capacitance here okay so
00:14:14.639
this is how it look like when we push
00:14:16.560
some charges and some currents okay
00:14:18.639
and that one is the completion of the
00:14:21.040
charging process
00:14:22.320
now where we find these capacitors value
00:14:26.399
and where we find
00:14:27.760
these charge values all of them are in
00:14:30.160
the data sheet
00:14:31.279
but if we got the qgs and the qgd this
00:14:34.959
is not
00:14:35.360
enough to to charge the the whole
00:14:37.680
capacitance because we have this part
00:14:39.600
to include this part they they have
00:14:41.760
defined for us in the data sheet
00:14:43.360
something called
00:14:44.880
the qg okay so the qg is the total
00:14:48.639
charge
00:14:49.279
you have to push to charge the phase
00:14:51.519
capacitance and also the second
00:14:53.120
capacitors
00:14:53.920
and push it more to arrive the
00:14:56.959
uh the turn on voltage okay so this is
00:15:00.160
the total capacitance that we care about
00:15:02.800
in our design and this waveform just
00:15:05.440
show to us
00:15:06.560
uh the current and and voltage waveform
00:15:09.440
with the vgs waveform as well
00:15:11.440
so during the charging here this is the
00:15:13.440
first time we
00:15:14.560
we we apply some pulses um
00:15:17.600
uh between the gate and the source
00:15:20.639
and there’s v threshold here where the
00:15:22.800
current start passing
00:15:24.240
flowing and also the uh voltage between
00:15:27.839
the drain and source
00:15:29.040
started dropping okay at that point we
00:15:31.759
have
00:15:33.120
another capacitance included uh within
00:15:36.480
the process
00:15:37.120
the charging time and this is the
00:15:39.120
plateau and we have here the current
00:15:41.759
is already gone to the maximum and the
00:15:44.800
voltage needs more
00:15:46.000
time to go to the lowest point here
00:15:48.800
until we
00:15:49.600
finish the plateau time here
00:15:52.639
and then the remaining of the process
00:15:55.920
time now will start to grow and grow
00:15:57.440
grow
00:15:57.920
until we finish the turning on the
00:16:00.320
mosfet
00:16:00.959
and again i think i mentioned that these
00:16:03.680
capacitance are mentioned in the data
00:16:05.360
sheet bob
00:16:06.160
they are not mentioned as cgs and cgd
00:16:10.160
and cds no they are mentioned in
00:16:12.560
different way
00:16:13.519
which is c i s s which is the input
00:16:15.920
capacitance
00:16:16.880
c o s s which is the outcome output
00:16:19.360
capacitance
00:16:20.240
and c r as us which is the reverse
00:16:22.720
transfer capacitance between
00:16:24.720
the the gate and the drain okay the gate
00:16:28.160
and the drain this one and this is an
00:16:30.399
example of
00:16:31.360
how the datasheet mentioned these so all
00:16:34.079
these capacitors here
00:16:35.279
and also it mentions that the qg
00:16:38.639
and also qgs and the qgd qgs and qgd
00:16:42.720
is not enough to determine the total
00:16:45.279
charge i need to turn on completely the
00:16:47.440
mosfets that’s why
00:16:48.639
they have included qg and for example
00:16:51.040
for this mosfet we have it as
00:16:53.040
63 nano column okay so we have here a
00:16:56.720
question which is important question
00:16:58.959
look at these capacitors here and mainly
00:17:00.959
the ciss the input capacitance i want to
00:17:04.160
charge
00:17:04.720
to turn in my mosfet i think here it
00:17:07.199
mentions
00:17:07.760
1 and 300 peak of arad
00:17:11.199
it’s very very tiny so why
00:17:14.720
we have concerns about the charging this
00:17:17.439
tiny
00:17:18.240
capacitors the concern because if we are
00:17:21.839
looking
00:17:22.480
at a turning on this mosfet
00:17:25.760
in very short time like 100 nanoseconds
00:17:28.640
so look at this
00:17:29.760
example now we have for example
00:17:32.960
uh capacitance between a gate and the
00:17:36.000
drain so this one
00:17:38.000
okay we will forget this one just to
00:17:40.080
make example simple
00:17:41.440
okay so this one now is about 500
00:17:44.160
picofarad for example
00:17:45.679
and we have the turn on time is 100
00:17:48.480
nanosecond
00:17:49.360
so i want to go through all that process
00:17:52.000
that i showed you
00:17:53.120
within just 100 nanoseconds how i
00:17:55.760
achieved that is it simple
00:17:57.360
or no so because the the time is very
00:18:01.360
short
00:18:02.240
even if the capacitance is very small i
00:18:05.360
need
00:18:05.919
huge current to push during this short
00:18:08.880
time
00:18:09.679
to turn on or to charge this capacitance
00:18:13.120
okay
00:18:13.679
and for example if we are looking at
00:18:15.679
this capacitor here
00:18:17.120
okay and we have these values as 400 and
00:18:20.160
i want to drive my mosfet
00:18:22.000
by 20 volt so now i am buying here 20
00:18:25.760
volt
00:18:26.480
okay and that started charging that
00:18:28.559
capacitor
00:18:30.080
and the voltage now dropped between the
00:18:32.559
call the drain and the source
00:18:34.640
making this point close now closer
00:18:37.520
closer closer to zero
00:18:38.880
it was 400 at this terminal okay
00:18:42.400
and finally this terminal will be zero
00:18:45.440
and this terminal should be 20. so what
00:18:48.320
is the difference in this process
00:18:50.160
that point was 400 and then it will be
00:18:53.919
zero so i have to discharge the 400 and
00:18:57.039
then
00:18:57.440
charge it in the reverse polarity
00:19:01.120
20 volts here okay coming from the gate
00:19:03.760
so
00:19:04.160
look at this complicated process here so
00:19:06.480
what is the difference between
00:19:08.559
the uh the first position
00:19:12.080
where we have 400 here and then the
00:19:14.880
final decision where we have a 20 volt
00:19:17.200
there and zero there
00:19:18.559
okay so the difference in this process
00:19:21.679
where we are tearing on our mosfet the
00:19:24.080
change in the gate to drain
00:19:25.840
voltage is 420 why 420 because we have
00:19:30.480
to finish this 400 first to make it zero
00:19:33.440
and then we charge it
00:19:34.480
from that terminal 20 so we have to
00:19:37.760
deplete the 400 and push another
00:19:40.960
to have a 20 volt so now this is the
00:19:43.760
change in voltage
00:19:45.200
and this is the change in current within
00:19:47.440
the 100 nanosecond
00:19:49.039
so that that current i need to make
00:19:52.320
this change equals the capacitance
00:19:55.760
multiplied by the difference in voltage
00:19:59.280
divided by difference in current
00:20:00.960
and in time and that equals 500
00:20:03.360
picofarad
00:20:04.400
and the difference in voltage is 420
00:20:07.520
within within time of 100 nanosecond and
00:20:10.640
at that equals
00:20:11.919
2.1 ampere so i have to push
00:20:15.679
in 100 nanoseconds 2.1 ampere is it easy
00:20:19.039
it’s not very easy okay that’s why we
00:20:22.159
have to use get drivers to do this
00:20:24.320
okay we can’t uh drive this mosfet
00:20:28.720
by applying zero five zero five from
00:20:31.919
microcontroller
00:20:33.360
from arduino from any microcontroller
00:20:35.919
stm microcontrollers
00:20:37.600
because it’s not a capable of pushing
00:20:40.640
that currently
00:20:42.159
during this time this is first reason
00:20:44.559
second reason
00:20:45.520
because it doesn’t have the voltage
00:20:47.760
sometime because some mosfets
00:20:49.600
they need to trigger on maybe at
00:20:52.799
15 volt and the microturns they don’t
00:20:55.679
have that voltage so that’s why
00:20:57.440
we have to use the gate drivers and if
00:21:00.000
we use that
00:21:00.880
charge information from the data sheet
00:21:03.280
and for example we have a qg here
00:21:05.520
equals 100 nano columns so we didn’t use
00:21:07.600
the capacitance we use the
00:21:09.440
qg and that qg i have to
00:21:13.120
to to deliver this is charged to the
00:21:16.320
mosfet okay within 100 nanosecond and
00:21:19.360
how i
00:21:20.159
also calculate the current the current
00:21:22.159
equals this charge
00:21:23.440
over time and we have 100 nano coulomb
00:21:26.320
divided by 100 nanosecond and that
00:21:28.080
equals
00:21:28.880
one ampere so i have to push when i’m
00:21:30.960
there again our microcontrollers can’t
00:21:33.200
do that easily
00:21:34.320
and that’s why we have to use get driver
00:21:36.720
i will show you now just
00:21:38.240
one example of without and with the gate
00:21:41.120
driver
00:21:41.760
what’s the situation and how that
00:21:43.600
switching look like
00:21:45.039
this is the vds waveform the voltage
00:21:47.440
between the drain and source
00:21:48.880
and this is the voltage between gate and
00:21:51.520
source
00:21:52.080
the voltage between gate and source is
00:21:54.400
developing like this
00:21:55.520
this is the first part during uh
00:21:58.799
charging the uh capacitance between the
00:22:01.600
the gate and source
00:22:02.799
and this is the plateau and then
00:22:05.280
complete the charging process
00:22:07.120
and that takes time that means it it
00:22:10.080
dissipates more power
00:22:12.000
during turning on that means increasing
00:22:14.720
the switching losses
00:22:16.159
okay but if we use the driver and good
00:22:19.600
design driver i think we can shorten
00:22:22.240
this
00:22:22.880
period to very small period and also
00:22:26.000
make the charging process faster
00:22:29.039
making the switching losses lower so
00:22:31.520
this is
00:22:32.080
with a gate driver and how it looked
00:22:34.799
like
00:22:35.120
and the final word about mosfets i think
00:22:38.799
we have other switches like igbts and i
00:22:41.280
will not talk about igbts because they
00:22:43.520
are very
00:22:44.400
close to the properties of uh driving
00:22:47.520
a mosfet and also it has some terminals
00:22:49.840
here shared with
00:22:51.280
bipolar transistors so that’s why
00:22:53.440
talking about igbt will not be very
00:22:55.360
different
00:22:56.000
if we just know the information about
00:22:58.320
mosfets and
00:22:59.520
by board transfer transistors so the
00:23:02.080
igbt
00:23:02.799
look like this it has collector and
00:23:04.559
emitter and they took
00:23:06.480
the input side here from the mosfets
00:23:08.799
which is the gate because
00:23:10.159
we don’t need to push current we have
00:23:12.240
just to apply some voltage
00:23:13.679
and it’s easier to drive than the
00:23:16.159
bipolar
00:23:17.600
transistors so as a comparison very
00:23:20.240
quick comparison
00:23:21.360
we have the speed for the bipolar
00:23:24.080
transistors
00:23:25.120
is slow okay for power
00:23:28.240
applications and for the mosfet it’s
00:23:31.360
fast and for the
00:23:32.640
igbt is slower than the mosfet but
00:23:35.840
faster than
00:23:37.039
the bybora transistors for the drive
00:23:39.679
power we have to drive it
00:23:41.279
very highly because as we mentioned in
00:23:43.279
some examples before that we have to
00:23:44.880
push
00:23:45.279
high current sometime and it has some
00:23:47.279
complication
00:23:48.320
but this one is is is no compared with
00:23:51.279
that one and this one is low because we
00:23:53.200
have
00:23:53.600
gate okay uh and that gate doesn’t need
00:23:56.880
a constant and the steady current to be
00:23:59.360
pushed toward the
00:24:00.799
uh the gate we just want to push high
00:24:03.360
current
00:24:04.000
just to charge the capacitors and that’s
00:24:06.000
it okay
00:24:07.200
for the large current capability it’s
00:24:09.360
very excellent so that’s why we have
00:24:11.440
between the emitter and collector we can
00:24:13.440
apply very high voltage
00:24:14.880
but for the mosfets for the silicon
00:24:17.840
mosfets yeah we don’t have that high
00:24:19.679
capability but
00:24:20.880
for the silicon carbide mosfets we have
00:24:23.840
we have up to
00:24:25.120
one thousand two hundred and one
00:24:27.520
thousand seven hundred as well
00:24:29.039
and maybe will be bigger and bigger in
00:24:30.559
the future as well so
00:24:32.240
silicon mosfets they are not capable of
00:24:34.720
blocking higher voltage and higher
00:24:36.559
current but for silicon carbide mosfet
00:24:38.960
yes it does okay and for the igbt yes
00:24:42.559
it’s
00:24:42.880
it has high voltage and current
00:24:45.679
properties and very excellent capability
00:24:47.919
so now according of what i uh see in the
00:24:51.279
application of
00:24:52.320
and and circuits of power electrons they
00:24:54.240
mainly use mosfets now
00:24:56.000
and by providing the the new material
00:24:58.880
silicon carbide
00:25:00.000
mosfets and thermospheres they
00:25:03.120
they make the usage of mosfets more
00:25:07.120
popular
00:25:07.919
and maybe a visible more if we compared
00:25:11.360
it with
00:25:11.760
lgbts and bipolar transistors so main
00:25:14.720
focus if you want just
00:25:16.480
look at the resources okay talking about
00:25:19.120
mosfets more
00:25:20.159
and make yourself knowledgeable about
00:25:22.400
what is the trends and what is coming
00:25:24.480
for as a new technology
00:25:26.400
to use it in your applications and to
00:25:28.640
make the reduction of
00:25:30.799
switching losses conduction lessons
00:25:32.720
worth for your new applications
00:25:34.880
that’s it for this part of the lecture
00:25:36.720
and see you in the coming lecture thank
00:25:38.240
you very much BU YAZUYU BANA TÜRKÇEye çevir