Mosfet heating Up in DC DC converter
  
STVTalk.com Forum Index
 STVTalk.com
All about Satellite TV systems.
 
 FAQFAQ   MemberlistMemberlist     RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 
   
Google
 
Web stvtalk.com
Mosfet heating Up in DC DC converter

 
Post new topic   Reply to topic    STVTalk.com Forum Index -> Satellite Navigation System
Author Message
praveen
Guest
Posted: Wed Dec 22, 2004 1:33 pm    Post subject: Mosfet heating Up in DC DC converter Reply with quote
Hello,
I have a problem in power supply which i have designed. I have
designed a dual supply of 3.3V and 5.4V from 30 V using semtech
SC2442H DC DC converter and Infineon BS0604NS2 Mosfet.
The problem is that mosfet is getting heated up a lot, it goes to
about 100 C.
I have calculated the power, it turn to be 0.72 W and the Mosfet can
handle upto 2 W. Can some one point why is the mosfet getting
heated???Because of this the inductor and capacitor near it is also
getting heated up.
DC DC converter operating frequency is 250 KHz.

Thanks and regards
Praveen
Back to top
Tony Williams
Guest
Posted: Wed Dec 22, 2004 1:34 pm    Post subject: Re: Mosfet heating Up in DC DC converter Reply with quote
In article <ff8a3afb.0412220033.2f92b685@posting.google.com>,
praveen <praveenkumar1979@rediffmail.com> wrote:

Quote:
I have a problem in power supply which i have designed. I have
designed a dual supply of 3.3V and 5.4V from 30 V using semtech
SC2442H DC DC converter and Infineon BS0604NS2 Mosfet. The
problem is that mosfet is getting heated up a lot, it goes to
about 100 C. I have calculated the power, it turn to be 0.72 W
and the Mosfet can handle upto 2 W. Can some one point why is the
mosfet getting heated???Because of this the inductor and
capacitor near it is also getting heated up. DC DC converter
operating frequency is 250 KHz.

Did your calculations allow for the switching losses?

I've just been simulating a simple 1300 Hz PWM switch
where the simulation shows that the MOSFETs dissipate
about 2.5W each. But only 1.5W of that is the "dc"
loss, another 1W comes from the switching losses. In
fact the simulation shows a peak of 160 V*I during
each on/off edge.

--
Tony Williams.
Back to top
Nospam
Guest
Posted: Wed Dec 22, 2004 1:50 pm    Post subject: Re: Mosfet heating Up in DC DC converter Reply with quote
"praveen" <praveenkumar1979@rediffmail.com> wrote in message
news:ff8a3afb.0412220033.2f92b685@posting.google.com...
Quote:
Hello,
I have a problem in power supply which i have designed. I have
designed a dual supply of 3.3V and 5.4V from 30 V using semtech
SC2442H DC DC converter and Infineon BS0604NS2 Mosfet.
The problem is that mosfet is getting heated up a lot, it goes to
about 100 C.
I have calculated the power, it turn to be 0.72 W and the Mosfet can
handle upto 2 W. Can some one point why is the mosfet getting
heated???Because of this the inductor and capacitor near it is also
getting heated up.
DC DC converter operating frequency is 250 KHz.

Thanks and regards
Praveen

And the connection with Satellite's and GPS is ?
Back to top
Meindert Sprang
Guest
Posted: Wed Dec 22, 2004 1:59 pm    Post subject: Re: Mosfet heating Up in DC DC converter Reply with quote
"praveen" <praveenkumar1979@rediffmail.com> wrote in message
news:ff8a3afb.0412220033.2f92b685@posting.google.com...
Quote:
Hello,
I have a problem in power supply which i have designed. I have
designed a dual supply of 3.3V and 5.4V from 30 V using semtech
SC2442H DC DC converter and Infineon BS0604NS2 Mosfet.
The problem is that mosfet is getting heated up a lot, it goes to
about 100 C.
I have calculated the power, it turn to be 0.72 W and the Mosfet can
handle upto 2 W.

This is a nice misunderstanding. The fact that your mosfet can handle 2 W
does not mean that it does not heat up at 0,7W. Check the thermal resistance
from the datasheet, multiply that with your power (0,72W) and this gives you
the temperature rise above ambient. If that gives you 100C, the circuit is
ok and you just need to cool the mosfet. If the calculated rise is lower,
you either do not have sufficient drive voltage to the gate (mosfet not
completely on) or you have an unwanted oscillation at a high frequence which
can also produce a lot of dissipation.

Meindert
Back to top
Rheilly Phoull
Guest
Posted: Wed Dec 22, 2004 5:26 pm    Post subject: Re: Mosfet heating Up in DC DC converter Reply with quote
"Nospam" <nospam@please.co.uk> wrote in message
news:41c9354c$0$401$afc38c87@news.easynet.co.uk...
Quote:

"praveen" <praveenkumar1979@rediffmail.com> wrote in message
news:ff8a3afb.0412220033.2f92b685@posting.google.com...
Hello,
I have a problem in power supply which i have designed. I have
designed a dual supply of 3.3V and 5.4V from 30 V using semtech
SC2442H DC DC converter and Infineon BS0604NS2 Mosfet.
The problem is that mosfet is getting heated up a lot, it goes to
about 100 C.
I have calculated the power, it turn to be 0.72 W and the Mosfet can
handle upto 2 W. Can some one point why is the mosfet getting
heated???Because of this the inductor and capacitor near it is also
getting heated up.
DC DC converter operating frequency is 250 KHz.

Thanks and regards
Praveen

And the connection with Satellite's and GPS is ?


It may have escaped your attention that sometime things are crossposted, for

example I am reading your post in the NG 'sci.electronics.design', which
would seem to be appropriate ??

--
Regards ..... Rheilly Phoull
Back to top
Nospam
Guest
Posted: Wed Dec 22, 2004 6:23 pm    Post subject: Re: Mosfet heating Up in DC DC converter Reply with quote
"Rheilly Phoull" <Rheilly@bigpong.com> wrote in message
news:32t7f2F3rhg71U1@individual.net...
Quote:

"Nospam" <nospam@please.co.uk> wrote in message
news:41c9354c$0$401$afc38c87@news.easynet.co.uk...

"praveen" <praveenkumar1979@rediffmail.com> wrote in message
news:ff8a3afb.0412220033.2f92b685@posting.google.com...
Hello,
I have a problem in power supply which i have designed. I have
designed a dual supply of 3.3V and 5.4V from 30 V using semtech
SC2442H DC DC converter and Infineon BS0604NS2 Mosfet.
The problem is that mosfet is getting heated up a lot, it goes to
about 100 C.
I have calculated the power, it turn to be 0.72 W and the Mosfet can
handle upto 2 W. Can some one point why is the mosfet getting
heated???Because of this the inductor and capacitor near it is also
getting heated up.
DC DC converter operating frequency is 250 KHz.

Thanks and regards
Praveen

And the connection with Satellite's and GPS is ?


It may have escaped your attention that sometime things are crossposted,
for
example I am reading your post in the NG 'sci.electronics.design', which
would seem to be appropriate ??

--
Regards ..... Rheilly Phoull



Yes I agree with you, but I still ask the question, what is the relevance to
Satellite's and GPS.?
All the replies are also coming to sci.geo.satellite-nav group, just because
the original person could not be bothered to check what groups he (she) was
sending to, and all the people replying just reply without checking where
their replies are going to.
Back to top
Rheilly Phoull
Guest
Posted: Wed Dec 22, 2004 6:29 pm    Post subject: Re: Mosfet heating Up in DC DC converter Reply with quote
"Nospam" <nospam@please.co.uk> wrote in message
news:41c9753b$0$16634$afc38c87@news.easynet.co.uk...
Quote:

"Rheilly Phoull" <Rheilly@bigpong.com> wrote in message
news:32t7f2F3rhg71U1@individual.net...

"Nospam" <nospam@please.co.uk> wrote in message
news:41c9354c$0$401$afc38c87@news.easynet.co.uk...

"praveen" <praveenkumar1979@rediffmail.com> wrote in message
news:ff8a3afb.0412220033.2f92b685@posting.google.com...
Hello,
I have a problem in power supply which i have designed. I have
designed a dual supply of 3.3V and 5.4V from 30 V using semtech
SC2442H DC DC converter and Infineon BS0604NS2 Mosfet.
The problem is that mosfet is getting heated up a lot, it goes to
about 100 C.
I have calculated the power, it turn to be 0.72 W and the Mosfet can
handle upto 2 W. Can some one point why is the mosfet getting
heated???Because of this the inductor and capacitor near it is also
getting heated up.
DC DC converter operating frequency is 250 KHz.

Thanks and regards
Praveen

And the connection with Satellite's and GPS is ?


It may have escaped your attention that sometime things are crossposted,
for
example I am reading your post in the NG 'sci.electronics.design', which
would seem to be appropriate ??

--
Regards ..... Rheilly Phoull



Yes I agree with you, but I still ask the question, what is the relevance
to
Satellite's and GPS.?
All the replies are also coming to sci.geo.satellite-nav group, just
because
the original person could not be bothered to check what groups he (she)
was
sending to, and all the people replying just reply without checking where
their replies are going to.

Ahh, such is human nature. Better to 'bend with the flow' you are never

going to change this sort of thing (worst luck), theres always the old
killfile thingy :-)

Cheers.... R.P
Back to top
Jack Erbes
Guest
Posted: Wed Dec 22, 2004 6:38 pm    Post subject: DC-DC Voltage Regulator Question Reply with quote
We have a similar topic going here in another thread. A number folks
here are good on electronics so I have a question.

Does anyone have an opinion on this design for a DC-DC voltage regulator
that is on Peter Bennet's GPS page? The design is here:

http://vancouver-webpages.com/peter/vreg.pdf

I was planning on getting the components and making the LM317 one to
drop a nominal 12V source to 4V.

I want to "pot" it in epoxy, put it in line on a cable, and will leave
the back of the LM317 exposed for heat dissipation.

Also, I am little confused about the two caps being shown with slightly
different symbols and one being polarized and the other not. What would
those two caps be called as far as the type and rating?

Thanks for any inputs.

Jack

--
Jack Erbes in Ellsworth, Maine, USA - jackerbes at adelphia dot net
(also receiving email at jacker at midmaine.com)
Back to top
Andy Hill
Guest
Posted: Wed Dec 22, 2004 8:52 pm    Post subject: Re: DC-DC Voltage Regulator Question Reply with quote
Jack Erbes <jackerbes@adelphia.net> wrote:
Quote:
We have a similar topic going here in another thread. A number folks
here are good on electronics so I have a question.

Does anyone have an opinion on this design for a DC-DC voltage regulator
that is on Peter Bennet's GPS page? The design is here:

http://vancouver-webpages.com/peter/vreg.pdf

I was planning on getting the components and making the LM317 one to
drop a nominal 12V source to 4V.

I want to "pot" it in epoxy, put it in line on a cable, and will leave
the back of the LM317 exposed for heat dissipation.

Also, I am little confused about the two caps being shown with slightly
different symbols and one being polarized and the other not. What would
those two caps be called as far as the type and rating?

Thanks for any inputs.

C1 is just a little ceramic cap of some sorts, while C2 is some sort of

electrolytic cap.

My question 'tho -- with switching regulators being both cheap as and common as
dirt these days, why would anyone in their right mind want to build a linear
regulation circuit? C'mon -- grab a cellphone car adapter out of the junkbox,
ebay, or wally world, look up the data sheet for the switching regulator that it
uses, and change out a resistor or two to get the voltage that you want.
Hardest part would be tracking down the right power connector -- probably would
have to go the pfranc route.
Back to top
B. Comegys
Guest
Posted: Thu Dec 23, 2004 2:05 am    Post subject: Re: DC-DC Voltage Regulator Question Reply with quote
Hi Jack ;
I would google it. Try "power trends" they are a TI company
"Family Name :Standard Voltage Regulators"
I have purchased a couple of these from www.digikey.com
Figure out what the input voltage is 12VDC the output voltage 4VDC and
how many AMPS you want. Then you order a Power Trends package and a cap
from DIGIKEY. solder some leads and the cap on to the package. The package
has small leads on it. Output voltage is very stable even when Input
voltage varies. You might need a resistor to adjust the output voltage.
All the Best
Bill


On Wed, 22 Dec 2004, Jack Erbes wrote:

Quote:

We have a similar topic going here in another thread. A number folks here
are good on electronics so I have a question.

Does anyone have an opinion on this design for a DC-DC voltage regulator that
is on Peter Bennet's GPS page? The design is here:

http://vancouver-webpages.com/peter/vreg.pdf

I was planning on getting the components and making the LM317 one to drop a
nominal 12V source to 4V.

I want to "pot" it in epoxy, put it in line on a cable, and will leave the
back of the LM317 exposed for heat dissipation.

Also, I am little confused about the two caps being shown with slightly
different symbols and one being polarized and the other not. What would
those two caps be called as far as the type and rating?

Thanks for any inputs.

Jack

--
Jack Erbes in Ellsworth, Maine, USA - jackerbes at adelphia dot net
(also receiving email at jacker at midmaine.com)
Back to top
clifto
Guest
Posted: Thu Dec 23, 2004 2:53 am    Post subject: Re: Mosfet heating Up in DC DC converter Reply with quote
Nospam wrote:
Quote:
"praveen" <praveenkumar1979@rediffmail.com> wrote...
I have calculated the power, it turn to be 0.72 W and the Mosfet can
handle upto 2 W. Can some one point why is the mosfet getting
heated???

And the connection with Satellite's and GPS is ?

To the original idiot crossposter:

Get a 13.2V power source such as a car battery. Get a 240 ohm, 1 watt
resistor. Connect the resistor across the power source (0.72 W) and
hold the resistor in your hand for one hour. Come back and report
your findings.

--
The state religion of the USA is atheism, as established by the courts.
Back to top
Christopher Green
Guest
Posted: Thu Dec 23, 2004 1:14 pm    Post subject: Re: Mosfet heating Up in DC DC converter Reply with quote
On 22 Dec 2004 00:33:59 -0800, praveenkumar1979@rediffmail.com
(praveen) wrote:

Quote:
Hello,
I have a problem in power supply which i have designed. I have
designed a dual supply of 3.3V and 5.4V from 30 V using semtech
SC2442H DC DC converter and Infineon BS0604NS2 Mosfet.
The problem is that mosfet is getting heated up a lot, it goes to
about 100 C.
I have calculated the power, it turn to be 0.72 W and the Mosfet can
handle upto 2 W. Can some one point why is the mosfet getting
heated???Because of this the inductor and capacitor near it is also
getting heated up.
DC DC converter operating frequency is 250 KHz.

Thanks and regards
Praveen

Sounds like inadequate heat sinking. This is an SO-8 dual MOSFET, and
it doesn't have real good thermal properties to begin with. See
Infineon's application note on thermal considerations with their SO-8
devices:
http://www.infineon.com/cmc_upload/documents/086/819/ThermalPackageConsideration-DPAK-SO-8.pdf

If you are using the device without any provision for heat sinking,
you're going to see it run something close to 80K over ambient at 0.72
W. You need a low-thermal-resistance path to several square
centimeters of copper just to get the thermal resistance down to 60K/W
or so. If this isn't feasible, you need something in a different
package for which you can more readily arrange a proper heat sink.

--
Chris Green
Back to top
Mike F
Guest
Posted: Fri Dec 24, 2004 5:13 am    Post subject: Re: Mosfet heating Up in DC DC converter Reply with quote
Another one that will cause it to overheat is if the driver
circuit for the MOSFET either has too slow a rise/fall time
or does not drive it completely on or off. Too much time
in the linear region causes lots of heat problems too.

mikey

"Christopher Green" <cj.green@att.net> wrote in message
news:b0vks0l2eqirl6je50c045vef6pu453vcn@4ax.com...
Quote:
On 22 Dec 2004 00:33:59 -0800, praveenkumar1979@rediffmail.com
(praveen) wrote:

Hello,
I have a problem in power supply which i have designed. I have
designed a dual supply of 3.3V and 5.4V from 30 V using semtech
SC2442H DC DC converter and Infineon BS0604NS2 Mosfet.
The problem is that mosfet is getting heated up a lot, it goes to
about 100 C.
I have calculated the power, it turn to be 0.72 W and the Mosfet can
handle upto 2 W. Can some one point why is the mosfet getting
heated???Because of this the inductor and capacitor near it is also
getting heated up.
DC DC converter operating frequency is 250 KHz.

Thanks and regards
Praveen

Sounds like inadequate heat sinking. This is an SO-8 dual MOSFET, and
it doesn't have real good thermal properties to begin with. See
Infineon's application note on thermal considerations with their SO-8
devices:

http://www.infineon.com/cmc_upload/documents/086/819/ThermalPackageConsideration-DPAK-SO-8.pdf

If you are using the device without any provision for heat sinking,
you're going to see it run something close to 80K over ambient at 0.72
W. You need a low-thermal-resistance path to several square
centimeters of copper just to get the thermal resistance down to 60K/W
or so. If this isn't feasible, you need something in a different
package for which you can more readily arrange a proper heat sink.

--
Chris Green
Back to top
Christopher Green
Guest
Posted: Fri Dec 24, 2004 6:46 am    Post subject: Re: Mosfet heating Up in DC DC converter Reply with quote
Quite so. Just that it is not strictly necessary to explain his
situation. His 100C temperature is consistent with his calculated 0.72W
dissipation and something around 100K/W thermal resistance. An SO-8
with no heat sink will do that without any further design flaws.
--
Chris Green
Back to top
 
Post new topic   Reply to topic    STVTalk.com Forum Index -> Satellite Navigation System All times are GMT
Page 1 of 1

 
 You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum



FPGA Electronics Hardware and Peripherals Auto Forum
New Topics Powered by phpBB