REFERENCE 1. N. Mohan, T. M. Undeland, and W.P. Robbins, Power Electronics: Converters, Applications and Design, 3rd Edition, Wiley & Sons, New York, 2003. PROBLEMS Flyback Converters: In a Flyback converter, V = 30V, N₁ = 30 turns, and N₁₂ = 15 turns. The self- inductance of winding 1 is 50 μH, and f₁ = 200 kHz. The output voltage is regulated at V₁ =9V. 8-1 8-2 Calculate and draw the waveforms shown in Fig 8-3 along with the ripple current in the output capacitor, if the load is 27W. For the same duty-ratio as in Problem 8-1, calculate the critical power which makes this converter operate at the border of incomplete and complete demagnetization modes. 8-11 8-3 8-4 Draw the waveforms, similar to those in Problem 8-1, in Problem 8-2. If a Flyback converter is operating in a complete de-magnetization mode, derive the voltage transfer ratio in terms of the load resistance R, the switching frequency fs, the self-inductance L, of winding 1, and the duty-ratio D. Forward converter: in In a Forward converter, V = 30V, N₁ = 10 turns, N₂ = 5 turns, and N₁ = 10 turns. The self-inductance of winding 1 is 150 μH, and the switching frequency fs = 200 kHz. The output voltage is regulated such that V₁ = 5V. The output filter inductance is 50 μН, and the output load is 25W. 8-5 8-6 Calculate and draw the waveforms for v₁, i₁, i, and i̟ in Fig. 8-4b. If the maximum duty ratio needs to be increased to 0.7, calculate N₁/N₁? 8-7 Why is diode D, necessary in Fig 8-4b? Two-Switch Forward Converters In a two-switch Forward converter, V₁ = 30V, N₁/N₂ = 2, and the switching frequency fs = 200 kHz. The output voltage is regulated such that V = 5V. The self-inductance of winding 1 is 150 μH, and the output filter inductance is 50 μH. 8-8 Calculate and draw waveforms if the output load is 200W. 8-9 Why is the duty-ratio in this converter limited to 0.5? Full-Bridge Converters 8-10 In a Full-bridge converter shown in Fig. 8-8, consider the output current through the filter inductor to be ripple-free dc. V,,, =30V, f=200 kHz, and N₁/N24. The output voltage is regulated such that V = 5V. Calculate the PWM waveforms in this converter. Assume the transformer ideal.