GATE 2020 EE – Question 60
In the dc-dc converter circuit shown, switch Q is switched at a frequency of 10 kHz with a duty ratio of 0.6. All components of the circuit are ideal and the initial current in the inductor is zero. Energy stored in the inductor in mJ (rounded off to 2 decimal places) at the end of 10 complete switching cycles is ________.
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Correct answer: 4.95 to 5.05
Explanation
The converter is a buck-boost type. With $T=0.1$ ms, the on-time is 0.06 ms and the inductor current rises by $\frac{50\times0.06\text{ ms}}{10\text{ mH}}=0.3$ A. During the off-time (0.04 ms) the inductor discharges into the $-50$ V output, giving a fall of $\frac{50\times0.04\text{ ms}}{10\text{ mH}}=0.2$ A. The net rise per cycle is $0.1$ A, so after 10 cycles $I=1$ A and $E=\frac12\times10\text{ mH}\times1^2=5$ mJ.