The Ćuk converter (pronounced Chook; sometimes incorrectly spelled Cuk, Čuk or Cúk) is a type of DC-DC converter that has an output voltage magnitude that is either greater than or less than the input voltage magnitude. It is essentially a boost converter followed by a buck converter with a capacitor to couple the energy.
By varying the duty cycle of the mosfet we can increase or decrease the DC input voltage by a factor of -D/(1-D) (where D is the duty cycle) but with opposite polarity. In the example we have set the duty cycle at 66.7% so with 10V at the input we expect that after the transients settle out to have -20V at the output.
If you want to change the duty cycle just change the
width of all voltage pulse sources (6.67% is 66.7% duty cycle and 10% is 100% duty cycle).
