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sci.electronics.design

Started by Glenn July 24, 2013
Read a little about isolated Cuk converters. Why are they not used 
instead of Buck, boost, Buck-boost converters? They work best with CCM 
but can of cause also use DCM. The original patents are expired:

http://boostbuck.com/TheFourTopologies.html
The 1:1 transformer is gapless. The input/output-transformer must have a 
gap:
http://www.boostbuck.com/IsolationoftheCukConverter.html
http://www.boostbuck.com/BypassingaCapacitor.html
http://www.boostbuck.com/GoodLookingMagnetics.html

Cuk topology is current loading/dumping, which means both input and 
output ripple is a lot easier to tame. Hey there is an inductor for 
"free" in series with the input and output.

( Here only the basic unisolated Cuk is described: 
http://en.wikipedia.org/wiki/%C4%86uk_converter )

I have only found one (non-isolated) Cuk chip:
http://www.ti.com/product/lm2611
http://www.ti.com/lit/ds/symlink/lm2611.pdf

-

It is even possible couple the input/output inductor to (almost) zero 
input ripple.

-

The "worst"/"impossible" Cuk to design seems to be the Integrated 
Magnetics Cuk Converter (IMCC, "DC transformer") because of "the two RHP 
zeros". Why is that a problem? Can the control be some AI? In DCM a each 
cycle can be done separately so you have full control? Note: The IMCC is 
the 1:1 transformer and input/output-transformer integrated.

It is called a DC transformer because of (almost) zero input and output 
ripple".

-

boostbuck.com: Easy Design of the Boostbuck Family of Converters: Beef:
http://www.boostbuck.com/Beef.html
Quote: "...Gus: I visited Dr. Cuk at his Irvine laboratories not long 
ago--he is an old mentor and friend of mine. He told me himself that the 
original patents on his converter had expired. His company has patents 
on further mods to the topology still in effect, but the original 
topology is no longer patented. It is this original that I deal with on 
my site...Gus: Nothing on my website is patented..."

home.netvigator.com: Cuk converter:
http://home.netvigator.com/~blessyou/cuk.html
Citat: "...The Cuk converter is a new SMPS topology at this moment. It 
include higher efficiency, low input and output current ripple, minimal 
RFI, small size and weight..."


T.S. Finnegan (January, 1991). "Cúk: the best SMPS" (på English). 
Electronics World & Wireless World ISSN: 0959-8332 Discontinued in 1995. 
Continued by Electronics World (ISSN: 1365-4675).: pp.69--72. Look at 
table at page 71. Quote: "...
The table below gives the effective primary and secondary copper losses, 
and the transistor and diode stress levels for the three types of 
converter, operating under identical conditions, for three different 
output voltages. The Cúk converter is more efficient and has lower 
stress levels in almost every respect
..."

Terrence Finnegan (July, 1991). "Design brief: 60W Cuk converter". 
Electronics World & Wireless World ISSN: 0959-8332 Continued by 
Electronics World (ISSN: 1365-4675).: pp.596--600.


Ćuk, Slobodan; Middlebrook, R. D. (June 8, 1976). "A General Unified 
Approach to Modelling Switching-Converter Power Stages" (PDF). 
Proceedings of the IEEE Power Electronics Specialists Conference 
(Cleveland, OH.): pp.73-86:
http://www.ee.bgu.ac.il/~kushnero/temp/guamicuk.pdf

Glenn
I saw someting very similar used to generate/regulate the Vs source in a pl=
asma TV. Then main advantage I see in such a circuit is much lower peak cur=
rents. Within its limitations I think it is useful for quite a few things, =
but I doubt it would be the best choic for something with wildly changind c=
urrent demands when you want the voltage to e regulated rock solid.=20

Of course that closely describes just what is needed for the Vs in a plasma=
 TV and they made it work. I think part of the reason they chose it is beca=
use they are dealing with so much EMI in those things it is ridiculous. I m=
ean, when you look at a flat panel TV and it has a metal back cover, it is =
a plasma, not an LCD. They would not use one ounce of metal if they could a=
void it but they have no choice. There is even a conductive glass screen in=
 front with grounding fingers all the way around it. I'm pretty sure it is =
also a UV filter. Don't break them things, they look expensive.
On 2013-07-27, jurb6006@gmail.com <jurb6006@gmail.com> wrote:
> I saw someting very similar used to generate/regulate the Vs source in a plasma TV. Then main advantage I see in such a circuit is much lower peak currents. Within its limitations I think it is useful for quite a few things, but I doubt it would be the best choic for something with wildly changind current demands when you want the voltage to e regulated rock solid. > > Of course that closely describes just what is needed for the Vs in a >plasma TV and they made it work. I think part of the reason they chose >it is because they are dealing with so much EMI in those things it is >ridiculous. I mean, when you look at a flat panel TV and it has a >metal back cover, it is a plasma, not an LCD.
Bullshit. eg: Panasonic Viera TH-L32E3Z Infact I've not seen a single LCD flat panel display that didn't have a metal back Many had a plastic cover over the metal back.
> They would not use one ounce of metal if they could avoid it but they have > no choice.
you're ovbiouslty making this shit up. -- &acirc;&scaron;&sbquo;&acirc;&scaron;&fnof; 100% natural --- news://freenews.netfront.net/ - complaints: news@netfront.net ---