电子工程考试代写 This is an open-book and open-notes exam. You may use any calculator and a laptop as a book reader. You may not communicate with
This is an open-book and open-notes exam. You may use any calculator and a laptop as a book reader. You may not communicate with anybody during the exam. You have 2 hours and 30 minutes to solve the following 3 problems:
Problem 1. (34%)
Design a flyback dc-dc converter that provides a regulated 12V from an 8 to 14V dc input source. The load resistance is within the range of one to five ohms. The output voltage ripple should be limited to 1%. Specify all component values, and calculate current and voltage stresses for devices. Assume ideal components except rC for ripple calculations.
Problem 2. (33%) 电子工程考试代写
A buck converter operates in DCM at duty ratio D = 0.6 and delivers 5 Amps to a resistance of 5Ω. The filter inductance is L = 1µH. The power switch on-resitance is 0.05Ω, and the Schottky power diode has 0.4V voltage drop with 0.02Ω forward resistance. The inductor loss can modeled by 0.1Ω equivalent series resistance (ESR). The ESR of the capacitor is 20 miliohms. Select a suitable switching frequency for DCM operation. Calculate efficiency of this converter. What is the input voltage to this converter? Neglect switching and gate-drive losses.
Problem 3. (33%) 电子工程考试代写
A boost converter with an input voltage of 10V and output of 40V supplies resistance 10Ω. Its switching frequency is 250kHz, inductor L = 50µH, and capacitor C = 330µF. Sketch inductor and capacitor currents marking all characteristic points and slopes. Calculate the rms value of the capacitor current. Assume ideal components.