Problem Set 10 for Resonant Techniques in Power Electronics | ECEN 5817, Assignments of Electrical and Electronics Engineering

Download Problem Set 10 for Resonant Techniques in Power Electronics | ECEN 5817 and more Assignments Electrical and Electronics Engineering in PDF only on Docsity! Problem Set 10 Power Electronics 3 Spring, 2006 1 Design of a flyback converter using a zero-voltage switching quasi-square wave resonant switch. Figure 1 illustrates a flyback converter based on the quasi-square wave zero-voltage switching resonant switch analyzed in class. The transformer magnetizing inductance operates as the resonant tank inductor. The transformer leakage inductances are much smaller than the magnetizing inductance, and can be neglected. The MOSFET and diode output capacitances are modeled in Fig. 1 by the single lumped capacitance C ; this capacitance functions as the tank capacitance of the QSW-ZVS resonant switch. Out- put filter capacitance C F is large and has negligible ripple. (a) Write the complete set of equations that can be solved to find the steady-state output voltage V . It is not necessary to re-derive the QSW-ZVS equations that were derived in lecture. (b) It is desired to design the converter to operate with the following: V g = 30 V Output: 45 V at 60 W Switching frequency: 500 kHz Turns ratio n = 0.5 Q = Load / Characteristic impedance = 5. (Be sure to refer both quantities to the same side of the transfomer.) Choose element values to achieve the required design. Specify: µ, f 0 , R 0 , L , C , and the resulting peak inductor current. Refer all quantities to the primary side of the transformer. 2 Analysis of a quasi-square wave zero-voltage switching resonant switch that employs a synchronous rec- tifier . Figure 2 illustrates a buck converter containing a synchronous rectifier. This converter employs an extension of the quasi-square wave resonant switch, to achieve zero-voltage switching of both the origi- + – L + V – Vg 1:n CF R C Fig. 1 QSW-ZVS flyback converter of Problem 1. + – CrVg D1 D2Q1 + v2(t) – i1(t) i2(t) + v1(t) – Lr C R + V – I Q2 Fig. 2 Quasi-square wave buck converter employing a synchronous rectifier, Problem 2.