GATE 2022 EE – Question 61
The steady state current flowing through the inductor of a DC-DC buck boost converter is given in the figure below. If the peak-to-peak ripple in the output voltage of the converter is 1 V, then the value of the output capacitor, in $\mu$F, is ________. (round off to nearest integer)
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Correct answer: 168
Explanation
The inductor current ramps up for $20\ \mu$s and down for $30\ \mu$s, so $D=\frac{20}{50}=0.4$, with the average inductor current $14$ A (between 12 A and 16 A). In a buck-boost converter the load current is $I_o=(1-D)I_L=0.6\times14=8.4$ A. During the on-time the capacitor alone supplies this current, so $\Delta V=\frac{I_oDT}{C}$ gives $C=\frac{8.4\times20\ \mu\text{s}}{1\text{ V}}=168\ \mu$F.