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.

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