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'Need help specifying TO-220 insulated MOSFET'
2011\06\02@151608 by Dwayne Reid

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Good day to all.

I'm looking for a reasonably sized MOSFET - needs to be good for more than 300V, more than 2A, more than 50W, insulated tab.

Its the insulated tab that is giving me problems - I don't know search terms to use when perusing Digikey's website.

I've run across terms like 'TO-220 Full Pack, Isolated' and 'ISOPLUS220' and 'ISOPLUS247' but those show only a subset of what I know is available.

Can anyone suggest what terms or package types I should be using when using the Digikey search engine?  Alternatively, any suggestions for part numbers that meet the above criteria are also appreciated.

Many thanks!

dwayne

-- Dwayne Reid   <spam_OUTdwaynerTakeThisOuTspamplanet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax
http://www.trinity-electronics.com
Custom Electronics Design and Manufacturing

2011\06\02@152436 by Mark E. Skeels

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This is just an idea but you might have better luck hitting a few manufacturer's websites......once you know how they structure their part numbers you could go back and hit Digikey again.

Mark Skeels
Engineer
Competition Electronics, Inc.
TEL: 815-874-8001
FAX: 815-874-8181
http://www.competitionelectronics.com

2011\06\02@170624 by Oli Glaser

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On 02/06/2011 20:16, Dwayne Reid wrote:
{Quote hidden}

Not sure how to improve on your attempts. I would have tried similar, like searching for TO220FP etc.
As suggested, I think looking on the manufacturers sites is a good idea as they are likely to categorise their products in more detail. Plus you will get info on relevant packages and any isolated tab/plastic series of parts so you can include these in your search term. I often do this when parts are hard to narrow down on places like Digikey/Mouser/RS.

You have probably already seen it, but is this one any good? Seems to be about the only option I could find on there that meets your specs.
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=IRFIB7N50APBF-ND <http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=IRFIB7N50APBF-ND>

2011\06\02@180349 by Dwayne Reid

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At 03:06 PM 6/2/2011, Oli Glaser wrote:

>You have probably already seen it, but is this one any good? Seems to be
>about the only option I could find on there that meets your specs.
>http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=IRFIB7N50APBF-ND
>
><http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=IRFIB7N50APBF-ND>

Yeah - that was the first part I ran across.  Then I found these:

<http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=IXFC16N50P-ND>

and

<http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=SIHG20N50C-E3-ND>

This last device is in a plastic TO-247 package but I don't know if there is exposed metal at the back of the device.  Unfortunately, the datasheet doesn't say.

Part of the problem is that this is the front end of the project - now I'm told that I may need as much as 150W dissipation.  So - now I'm looking for larger parts.

The device will be operated in the linear region for use as a heating device on a flat aluminum plate.  Thus the large dissipation requirement.  Max temperature will be somewhere near 15C or so - this device is simply used to keep the internal temperature of an outdoor piece of equipment warm enough to stop it from failing because of extreme cold.  I plan to use a thermistor tightly coupled to the aluminum plate to avoid excessive transistor temperature.

Simple project, except for finding the insulated transistor!

Many thanks!

dwayne

-- Dwayne Reid   <.....dwaynerKILLspamspam@spam@planet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax
http://www.trinity-electronics.com
Custom Electronics Design and Manufacturing

2011\06\02@181512 by Peter Loron

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On 06/02/2011 03:03 PM, Dwayne Reid wrote:
{Quote hidden}

I may be showing my ignorance here, but why not use something *designed* as a heating element? Or at least a simple cement power resistor?

-Pet

2011\06\02@182331 by Mark Rages

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On Thu, Jun 2, 2011 at 5:03 PM, Dwayne Reid <dwaynerspamKILLspamplanet.eon.net> wrote:
{Quote hidden}

Why not PWM power to a aluminum-housed resistor?

Power FETs designed for linear use are not terribly cheap.

For example, look at the SOA graph for your SiHG20N50C.  It is for
pulsed power, not DC, but extrapolating from 10ms towards DC, it's not
at all clear that continuous 150W is OK at any combination of drain
current and Vds.

Use PWM and you can use a much smaller transistor.

Regards,
Mark
markrages@gmail

2011\06\02@183718 by Oli Glaser

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On 02/06/2011 23:15, Peter Loron wrote:
> I may be showing my ignorance here, but why not use something*designed*
> as a heating element? Or at least a simple cement power resistor?
>

That was my instant thought too - would a resistor or some nichrome wire not do the job?
Or use a standard transistor (I would actually think a bipolar, e.g 2N3055 would be more suited to this task) and shove some insulating material between it and the case.

2011\06\02@211009 by Dwayne Reid

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At 04:15 PM 6/2/2011, Peter Loron wrote:

>I may be showing my ignorance here, but why not use something *designed*
>as a heating element? Or at least a simple cement power resistor?

Its a reasonable question.  I don't have much height to play with in this enclosure.  About the only suitable heating element is a Watlow silicone-rubber thin, flat heating element - and these get expensive.

That was going to be my first approach.  But: the heater has to be driven from a 120Vac power line.  I was going to use a triac for switching.  The triac will be dissipating about a watt or so and needs heatsinking - I was going to fasten it to the same aluminum plate as the heating element.

But: I've been making little heaters for years now based on using a TIP122 power transistor as a heater.  This is a little circuit board powered from a 12V supply - the board is tiny (about 0.5" x 1") and fastens to a metal plate or metal strip that is formed to fit inside the enclosure.  There is a bunch of these inside ceiling-mounted surveillance cameras all over Northern Canada, for example.  Another bunch installed in the credit-card readers inside parking garage entrance controllers.  They work very well and we've sold a bunch of them.

Anyway, it occurred to me that I could simply scale the same circuit up to run from rectified, un-filtered AC and simply use the pass device as the heating element.  Like I said, I've got lots of experience with this.

Back-of-the-envelope calculations say this should work well.  Now all I need to do is find a suitable pass device.  N-channel MOSFET, because of price and voltage rating.

The device will not be running hot - the unit turns on somewhat near 0C and is guaranteed to be off at 10C or so.  Its only purpose is to raise the internal temperature of the air inside the enclosure significantly above the -45C that the outside of the enclosure is sitting at.

Hope this makes sense!

dwayne

-- Dwayne Reid   <.....dwaynerKILLspamspam.....planet.eon.net>
Trinity Electronics Systems Ltd    Edmonton, AB, CANADA
(780) 489-3199 voice          (780) 487-6397 fax
http://www.trinity-electronics.com
Custom Electronics Design and Manufacturing

2011\06\02@212859 by Denny Esterline

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>
> >I may be showing my ignorance here, but why not use something *designed*
> >as a heating element? Or at least a simple cement power resistor?
>
> Its a reasonable question.  I don't have much height to play with in
> this enclosure.  About the only suitable heating element is a Watlow
> silicone-rubber thin, flat heating element - and these get expensive.
>
>
Perhaps a TO220 packaged resistor (or it's brother, the TO247) They can't
quite dissipate your 150 watts, but a couple in series certainly could.
Digikey has them in singles for about $7 (dropping to about $4 in qty)

Also, why the requirement of a full pack? Is mica or a sil-pad not enough
isolation? I don't see how a full pack gives you better safety than a
sil-pad and shoulder washer. - either way you still have the leads with as
much exposure as the tab would normally have.

-Denn

2011\06\02@222532 by Oli Glaser

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On 03/06/2011 02:10, Dwayne Reid wrote:
> Anyway, it occurred to me that I could simply scale the same circuit
> up to run from rectified, un-filtered AC and simply use the pass
> device as the heating element.  Like I said, I've got lots of
> experience with this.
>
> Back-of-the-envelope calculations say this should work well.  Now all
> I need to do is find a suitable pass device.  N-channel MOSFET,
> because of price and voltage rating.
>
> The device will not be running hot - the unit turns on somewhat near
> 0C and is guaranteed to be off at 10C or so.  Its only purpose is to
> raise the internal temperature of the air inside the enclosure
> significantly above the -45C that the outside of the enclosure is sitting at.
>
> Hope this makes sense!

Yep, makes sense.
I can see how your smaller TIP122 circuits would work well, and should scale up okay providing you can find a suitable power transistor. I realised the suggestion of a 2N3055 was silly as they don't have the required voltage rating. I was thinking more of the TO-3 package and the high power rating.
I'm thinking it might be difficult to meet your specs with just one transistor (and keep the price reasonable) Maybe it would be an option to put a couple in parallel.

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