In this activity, you will write the third part of your term paper.
Explain why we need a rectifier and a forward converter to make a DC power supply.
Please go through the given instructions and write a paper on switch-mode DC power supplies. Please see detailed instructions for requirements from the term paper document below. Use illustrations if necessary.
Your paper needs to answer the following questions along with your comments and discussion.
In this part of the term paper, design a single-phase switch-mode DC power supply with a forward converter. Provide answers to the questions below.
Please combine the single-phase full-wave rectifier from part two of your term paper with a forward converter to produce a switch-mode DC power supply, as shown below. The output of the bridge rectifier serves as input to the forward converter.
As explained, a forward converter is a popular switched mode power supply (SMPS) circuit that is used for producing isolated and controlled DC voltage from the unregulated DC input supply. It consists of a fast switching device ‘S' along with its control circuitry, a transformer with its primary winding connected in series with switch ‘S' to the input supply, and a rectification and filtering circuit for the transformer secondary winding. The load is connected across the rectified output of the transformer secondary. It is basically a DC-DC buck converter (as seen in part one of the term paper) with the addition of a transformer for output voltage isolation and scaling. When switch ‘S' is turned on, input DC gets applied to the primary winding and simultaneously a scaled voltage appears across the transformer secondary. When switch ‘S' is turned off, the primary as well as the secondary winding currents are suddenly brought down to zero. Current through the filter inductor and the load continues without any abrupt change. Diode ‘D2' provides the freewheeling path for this current. The DC output is similar to that of a buck converter multiplied by the transformer winding ratio:
Vout = DVIN x Ns/Np
Assume all ideal components including the isolating transformer, Ns/Np = 2 and switch frequency is 16.7 kHz as in part one of the term paper. Design this switch-mode DC power supply by doing the following:
• Determine the duty ratio D so that the DC output to the load is 12 v. Draw the waveform of the input AC voltage V1, bridge rectifier output (see part two of the term paper; this is also the input to the forward converter), voltage after diode D1, and voltage at the load (with all harmonics blocked).
• Explain why a transformer still works even with a DC input to the forward converter.
• Explain the function of diode D1.
Please include all necessary circuit diagrams or block diagrams in your paper. Please also draw the necessary waveforms together with your comments or discussion.
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.
Keep the following points in mind:
• The efficiency of a buck DC-DC converter.
• The principle of a buck DC-DC converter.