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GATE 2015 EE – Question 18

Power Electronics · DC to DC conversion: Buck, Boost and Buck-Boost Converters · 1 mark · Numerical answer

In the following chopper, the duty ratio of switch S is 0.4. If the inductor and capacitor are sufficiently large to ensure continuous inductor current and ripple free capacitor voltage, the charging current (in Ampere) of the 5 V battery, under steady-state, is ________.

A 20 V source feeds a buck chopper made of switch S, a freewheeling diode, an inductor L and a capacitor C. The load is a $3\ \Omega$ resistor in series with a 5 V battery.

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Correct answer: 1

Explanation

A buck converter gives an output voltage of $D \times V_{in} = 0.4 \times 20 = 8$ V. The $3\ \Omega$ resistor and the 5 V battery are in series across this output, so the battery charging current is $\frac{8 - 5}{3} = 1$ A.