Question

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 L1 Np: N BH621BH62 D, V1 Load C1 100p 45 Vrms D3 BH62 18H62 D4 Control Circuit Switch S Figure 1. A switch-mode DC power supply As explained in section 8.5 of the textbook, 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: N. Assume all ideal components including the isolating transformr 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.

Answer 1

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