Sir Hadeed sir,
I am designing MPPT controller for solar pv panels, kindly i wanted to ask you about the operation of Cuk converter the out put of cuk is also negative. so is there any method that the duty cycle of dc-dc converters automatically changes with the time? like i have seen in some reference papers that they do some feed back to the controller to change the duty cycle with time.. plz need your help regarding this .. i would really appreciate ur effort.
there are several books on this topic. generally this circuit is not used for BUCK/BOOST operation. designers use regular topologies of buck and boost for these specific tasks. The answer to this question is very well discussed in the book i mentioned above.
well if you need a positive voltage then add an other BUCK/BOOST circuit with 52% duty cycle (Since at 50 % due to losses in circuit elements output will be slightly less then input).
Secondly the circuit elements needs redesigning if you disturb the input voltages to a very large extent. Theoretically it must give us infinite output voltage at 100 % duty cycle but it never happens because of the fact that practically there are always losses in circuit elements
@manjunath: This type of DC DC converter is also known as polarity inverting converter(For more information on DC DC Converter please refer to Switching power supply design by Abraham I pressman). The output is always inverted .So there is nothing wrong with this circuit.