Q1. Design a buck converter with the following specifications:
Input voltage between 11 V and 15 V, output voltage 1.8 V, output current 20 A, inductor current ripple less than or equal to 2 A, output voltage ripple less than or equal to 0.018 V, switching frequency 100 kHz.
a) Find L, C such that the specifications are met over the whole input voltage range.
b) Verify your design using simulation.
c) Find the current and voltage ratings for the diode and the switch in this converter, then find an appropriate diode and MOSFET for this converter based on the ratings.
d) Suppose someone else has designed a buck converter for the specifications in this problem and chosen an inductor value of 47 μH and a capacitor value of 220 μF.
Determine what switching frequency is needed to meet the ripple specifications.
Q2. A buck converter has been designed for 5 V input, 1 V output, with an inductance 10 μH and a switching frequency of 350 kHz.
a) Determine the load resistance and power for critical conduction mode.
b) Determine the duty ratio required to maintain a 1 V output as resistance increases by a factor of 10 from the critical conduction load.
c) Verify your results using simulations.
d) Sketch the curve of duty ratio vs. resistance for maintaining 1 V output voltage for R ε [1, 100]Ω