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ECEN 405 Assignment 3
Due: 1 April
Worth: 3%
1. Design a buck converter to produce an output voltage of 18V across a 10Ω load
resistor. The output voltage ripple must not exceed 0.5%. The DC supply is a 48V.
Design for continuous inductor current. Specify the duty ratio, the sizes of the
inductor and the capacitor, peak voltage rating of each device, and the rms current
in the inductor and the capacitor.
2. In a buck converter, L = 25µH, and is operating in DC steady state under the
following conditions: Vin = 42V, D = 0.3, Po = 24W and fs = 400kHz. Assume ideal
components.
i. Calculate the critical value of the inductance L such that this Buck converter
remains in the CCM at and above Po = 5W under all values of input voltage
Vin in the range from 24V to 50V.
ii. With input voltage varying between 24V and 50V, for each input, the duty
ratio is adjusted to keep the output voltage constant at its nominal value (Vin
= 42V, D = 0.3). Calculate the minimum value of the inductance L that will
keep the converter in CCM at Po = 5W.
3. Assignment question in Lab 3.