At the "6to" level, the PDF includes introductory problems on soft-switching converters (ZVS/ZCS). These are the most difficult problems, often requiring solving second-order differential equations for the resonant tank (L-C circuit).
Example: "A Buck converter has $V_in=20V$, $V_out=5V$, $L=100\mu H$, $f_s=100kHz$. Calculate the duty cycle and current ripple." At the "6to" level, the PDF includes introductory
Typical Problem: "A single-phase full-wave controlled rectifier feeds an R-L load. The source is 220Vrms at 50Hz. The firing angle (α) is 60°. Determine: a) Average output voltage, b) RMS current, c) Power factor, d) Distortion factor." Example: "A Buck converter has $V_in=20V$
Barrado’s Twist: Instead of a pure R-L load, the problem adds a back EMF (counter-electromotive force) simulating a DC motor. You must calculate if the rectifier is in continuous or discontinuous conduction. b) RMS current