>> Did anyone find this interesting? I spent a while photocopying it 
>> in the
>> library, scanning it, converting it to PDF.. :-)

> Sure, but cuk is quite known, I'm using it because could be quiet.

The circuit that Martin referenced seemed to cover a little more than 
basic CUK.

Not having played with CUK in practice I may be missing something 
that's in most CUK implementations BUT these circuits had a polynomial 
relationship between duty-cycle and voltage ratio allowing a much 
wider than usual input:output voltage ratio and/or a much wider 
control range.

They are effectively two buck converters in series with the first 
being "passive" and being driven by the current pulses from the second 
active stage

The author also makes the point that any buck converter with pulsating 
current input can be preceded by a  passive  buck stage and thereby 
achieve an N^2 voltage transformation ratio. Which would often be 
useful.

Having an eg N^2 ratio for a say 300 volt to 12 volt converter would 
allow each stage to have sqrt(300/12) ~= 5:1 conversion. eg 1st stage 
is 300V:60 Volt and second 60V:12V. This could have substantial 
advantages in inductor design over a single stage system.



        Russell 

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