Write the first part of term paper. In this part of the term paper, you will explain why we need DC-DC converters and how to build a buck DC-DC converter.
Carefully review these detailed instructions for requirements for the term paper. Use illustrations if necessary to complete the assignment.
Your paper needs to answer the following questions, along with your comments and discussion:
1. Why DC-DC converters?
A buck converter is a specific type of DC-DC power electronic converter whose goal is to efficiently step down DC voltage to a lower level with minimal ripple. Consider an application that requires 0-100mA at 5V. Assume that you only have access to a +15V power supply. The simplest solution is to use a voltage divider, shown as follows:
Calculate the efficiency of this circuit and comment on it. Now, if we use a buck converter with an efficiency of 92%, see below:
Calculate the amount of power wasted and compare that to the voltage divider circuit above.
2. Buck converter calculations
A buck converter can be seen in the following figure where the transistor can be represented by a switch:
· If the switching frequency is given as 16.7 kHz, VIN =15v, and the output is 5v as in section 1, draw the waveform of Vs2 and indicate the duty ratio D. Vout = DVIN. If the output needs to increase, will D increase or decrease?
· Note that the waveform of Vs2 is a square wave that contains the DC output Vout as well as harmonics. The lowest harmonic has the frequency of 16.7 kHz (from Fourier series expansion), which is also the switching frequency. Also, note that LC in the above converter circuit consists of a second order low pass filter with a corner frequency of To significantly reduce the harmonics, must be much less than the switching frequency. Why? Assume =0.1*switching frequency, calculate L and C (assume one and calculate the other).
Please include all necessary circuit diagrams or block diagrams in your paper. Please also draw the necessary waveforms together with your comments or discussions.
Your paper should be at least two pages, typed single-spaced, using 12-point font and 1-inch margins on the top, bottom, right, and left. You should use the APA guidelines for writing and citations.