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From: Tim Williams on 7 Jul 2010 00:36
"Martin Riddle" <martin_rid(a)verizon.net> wrote in message news:i10mka$rbp$1(a)news.eternal-september.org...
> CCM is suppose to be a tad less in switching noise than DCM.

But, you need dI/dt snub or else your rectifier makes it all back (or your switch gets toasty).

Not a problem is you use SiC rectifiers, but those are still a while off in price :)

BCM is the best I suppose, certainly easier to snub and doesn't have the ringing of DCM. Has spread-spectrum characteristics, which may be handy.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms
From: Hammy on 7 Jul 2010 07:10
On Tue, 6 Jul 2010 23:36:21 -0500, "Tim Williams"
<tmoranwms(a)charter.net> wrote:

>"Martin Riddle" <martin_rid(a)verizon.net> wrote in message news:i10mka$rbp$1(a)news.eternal-september.org...
>> CCM is suppose to be a tad less in switching noise than DCM.
>
>But, you need dI/dt snub or else your rectifier makes it all back (or your switch gets toasty).
>
>Not a problem is you use SiC rectifiers, but those are still a while off in price :)

This paper all be it's 6 years old shows comparision of rectifier
technologies in CCM boost and its really not worth paying for a SIC
device until you start getting over 1kW output power.

http://mysite.valuebound.com/boseresearch/resources/designconsiderations.pdf

I have a couple of soft recovery "Stealth diodes" I'll try. They tend
to have a higher Vf. But if you dont have to use a snubber they might
have better overall efficency.

>BCM is the best I suppose, certainly easier to snub and doesn't have the ringing of DCM. Has spread-spectrum characteristics, which may be handy.
>
>Tim
I think CCM is the best mode above 2 to 300W. DCM the peak and rms
currents would start to get excessive.

Heres an IGBT for you Tim. Look at Vce sat vs temp. It shows Vce sat
at 0.95 x the 25C value. The worst case Vce sat @ 25C is 1.7V.

http://www.st.com/stonline/products/literature/ds/11823/stgw35nb60sd.pdf
From: Hammy on 7 Jul 2010 07:30
On Tue, 6 Jul 2010 21:51:58 -0400, "Martin Riddle"
<martin_rid(a)verizon.net> wrote:


>
>Heres the 1150
><https://ec.irf.com/v6/en/US/adirect/ir?cmd=catSearchFrame&domSendTo=byID&domProductQueryName=IR1150>

I was using IRF1150 no wonder I couldn't find it.

>Similar to the ncp part. It could do 200khz.
>
>TI also has the UCC28019.
><http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=296-21936-1-ND>
>Aside from the loop component values, and brown out, it's just about a
>pin-for-pin replacement.
>
>We have a larger >1Kw design that used the 1150 and a large IGBT, the
>switching losses were a problem and needed a beefy driver.

I don't know what your output voltage is but if you could use a 500V
FET this would give you half the conduction losses of a typical 1.7Vce
sat IGBT For a 1kW design.I'm guessing between the IGBT and the
bridge rectifier heat sink size is probably eating up the most real
estate.

http://canada.newark.com/stmicroelectronics/sty60nm50/n-channel-mosfet-500v-60a-max247/dp/89K1683?whydiditmatch=rel_1&matchedProduct=STY60NM50

They aren't giving it away though.$27.97 Canadian $$.


>Right now my design is at 100khz and filtering isn't an issue. Going
>higher may make that choke a tad smaller or the same size if nothing is
>availble as a replacement.
>
>CCM is suppose to be a tad less in switching noise than DCM.
>
>Good luck
>
>Cheers
>
>
>
>
From: JosephKK on 8 Jul 2010 00:29
On Tue, 06 Jul 2010 10:23:23 -0700, Fred Abse
<excretatauris(a)invalid.invalid> wrote:

>On Tue, 06 Jul 2010 09:04:48 -0400, Hammy wrote:
>
>> A massed
>> produced inductor isnt going to use oversized cooper
>
>Must be a barrel choke.

Shooting from the hip?
From: Joerg on 9 Jul 2010 17:42
Tim Williams wrote:
> "Hammy" <spam(a)spam.com> wrote in message
> news:lln8369bn0fev7tloce22487ao0gcl2keh(a)4ax.com...
>> This paper all be it's 6 years old shows comparision of rectifier
>> technologies in CCM boost and its really not worth paying for a SIC
>> device until you start getting over 1kW output power.
>>
>> http://mysite.valuebound.com/boseresearch/resources/designconsiderations.pdf
>>
>
> Like I said to Joerg, why don't they make 1A SiC's? They'd be
> cheaper than the big suckers, certainly not as cheap as a UF4007, but
> if you have to rectify a Tesla coil, what else are you going to do?
>

Huh? I've never seen one less than an amp. Cree makes really fat SiC
diodes such as this one but you've got to have deep pockets:

http://www.cree.com/products/pdf/CPW3-1700S010.pdf

[...]

--
Regards, Joerg

http://www.analogconsultants.com/

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