SMPS Cuk converters

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:

The 1:1 transformer is gapless. The input/output-transformer must have a gap:

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:

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I have only found one (non-isolated) Cuk chip:

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

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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, 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.

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boostbuck.com: Easy Design of the Boostbuck Family of Converters: Beef:

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:

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.

?uk, 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:

Glenn

Two important note:

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The (incl. isolated) Cuk converter can "easily" be modified to be bidirectional - just exchanged the diode for a power MOSFET - and some more control circuit.

The second power MOSFET can also be used for

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It is even possible to make AC Cuk converters - and the patents are still active:

Feb 1, 2008 Bridgeless PFC Boosts Low-Line Efficiency:

Dr. Slobodan Cuk:

Part 1: Jul 1, 2010, True Bridgeless PFC Converter Achieves Over 98% Efficiency,

0.999 Power Factor:

Part 2: Aug 1, 2010, True Bridgeless PFC Converter Achieves Over 98% Efficiency,

0.999 Power Factor: Part 2:

With schematic: Part 3: Oct 1, 2010, Single-Stage Isolated Bridgeless PFC Converter Achieves Over 98% Efficiency, 0.999 Power Factor:

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Application Characteristics of an Experimental RB-IGBT (Reverse Blocking IGBT) Module:

A High Efficiency Indirect Matrix Converter Utilizing RB-IGBTs:

/Glenn

I disagree with this part:

It's impractical to do things like efficiency estimates by hand, what with variable frequency, ohmic losses, switching losses, diode and ESR losses, snubbers, all that. Instinct and Spice can optimize a circuit fast.

They use more expensive magnetics, for one.

--

John Larkin                  Highland Technology Inc 
www.highlandtechnology.com   jlarkin at highlandtechnology dot com    

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