In a certain application, an unregulated dc input voltage can vary between 18 and 36 V. It is desired to produce a regulated output of 28 V to supply a 2 A load. control circuit automatically adjusts D to maintain the constant output voltage and current. All ideal components.  Hence, a converter is needed that is capable of both increasing and decreasing the voltage. Since the input and output voltages are both positive, converters that invert the voltage polarity (such as the basic buck-boost converter) are not suited for this application.

(1) Sketch the waveforms of the transistor voltage Vds and transistor current IT or (Id for drain current) and give expressions for their peak values. find the numerical maximum value on the sketch for Vds and IT (Id). ignore the effect ripple.

(2) Derive the expression for switching frequency at the converter operates between the CCM and DCM at the boundary. the answer is in terms of D, Vin, L1, L2, iL1, iL2. you may assume L1=L2.