It is desired to convert 60 Hz 120 Vac (rms) to 240 Vac (rms), to power a 1 kW ac load. Although…

It is desired to convert 60 Hz 120 Vac (rms) to 240 Vac (rms), to power a 1 kW ac load. Although a conventional 60 Hz ac transformer could beused in this application, such a transformer is large and heavy. Instead, it is decided to use a boost converter switching at 100 kHz, as illustrated in Fig. 1.This converter is small and lightweight. It operates at constant duty cycle of approximately 0.5, so thatv(t) = 2vg(t). The elementsL

andCare chosen to filter the switching harmonics and have smallswitching ripples; however, they have negligible effect on the 60 Hz components of the waveforms. The load is a linear impedance

(a )

Realize the switches using SPST ideal switches, and explicitly define the

voltage and current of each switch.

(b)

Express the on-state current and off-state voltage of each SPST switch in

terms of the converter inductor currents, capacitor voltages, and/or input source voltage.

(c)

Solve the converter to determine the inductor currents and capacitorvoltages, as in chapter2.

(d)

Determine the polarities of the switch on-state currents and off-state

voltages. Do the polarities vary with time?

(e)

State how each switch can be realized using transistors and/or diodes, andwhether the realizationrequires single-quadrant, current-bidirectional twoquadrant, voltage-bidirectional two-quadrant, or four-quadrant switches. Sketch a schematic of the converter powerstage, which includes your realization of the switching elements using semiconductor power devices