Dual Forward-Flyback Converter - Introduction to Power Electronics | ECEN 5797, Assignments of Electrical and Electronics Engineering

Download Dual Forward-Flyback Converter - Introduction to Power Electronics | ECEN 5797 and more Assignments Electrical and Electronics Engineering in PDF only on Docsity! SC , be, ECENSI97 Selihen { Problem 2 a oe ec ENt97 1 Dual forward/flyback converter | The converter illustrated below has been proposed as an approach that allows one converter to simultaneously regulate two independent outputs. In addition, it allows the transformer of the forward converter to operate over a wider range of duty cycles than in the conventional approach. Lf The main output (that produces voltage Vi) constitutes the secondary side of a forward converter, and is designed to operate in continuous conduction mode (CCM) for all expected values of load resistance Ry. A controller adjusts the transistor duty cycle D as necessary to maintain V, at the desired value. The auxiliary output (that produces voltage V;) constitutes the secondary side of a flyback converter, and is designed to operate in discontinuous conduction mode (DCM) for ali expected values of load resistance Rs. The controller adjusts the switching frequency £ as necessary to maintain Vat the desired value. ‘The three-winding transformer has turns ratio 1:1:1, with magnetizing inductance L2. (a) For the case when output 1 operates in CCM and output 2 operates in DCM, find the expressions for the steady-state output voltage Vi and V2, as functions of the transistor duty cycle D, the switching frequency , and circuit element values as appropriate. (b) Derive the conditions for which output 1 operates in CCM and output 2 operates in DCM. © Does the transformer reset correctly (ie, do the volt-seconds balance) when D> 0.5? (d) Select values for £; and Lz so that the converter behaves as described above, and meets the following requirements: 20V < V<30V Ourpur t: Vj = 12 V, max current = 2 A, min current = 1 A Ourput 2: V; = 36 V, max current = 0.2 A, min current = 0.1 A Choose Ly such that the maximum switching frequency is 300 kHz. Choose , such that its current ripple Ai is 0.4 A under worst case conditions, and is less than 0.4 A under all other conditions. For your design, compute the range of switching frequencies and duty cycles over which the converter will operate.  v= DNs Vi D No zie FS Ra b> Mode beandowy Oxtpst Li ecm Ai, = VV OT = DD. VT: Ly a aL, - VN DN. Tr ats = by charap kalance on Cc, Ly CEM opershon | T, > Sh > w > Pe. Dp Ny Ts Ry al, > ab / 3 ’ a > Kk, > D RTs 7? wi K\= alu RTs Oatpst AY DCM then ov [pat o2. operates w com, we ast DY =O Vy by yolt- wecond balance on ban ond D'Iy = = No by charge balances on Co. ore  so Im = Se = DS DtRe pie Re ak Aims Ve DS aby tay Aim > Tm => NobTs Dvs5 Alm DP? Re 2 ) 1 Oyo Se s Or with Kg = 2be Re15 (2) Yes the voll- sec ands balance ow Lay oe all Dade \ land less ef as well) . The £4, back ondpict ts obfeiy COME M wode voltage Ny adiushs as wecesSary Lance ov" Lia . pol} - second bo (4) Chose valves of Lian Ll, ® sahshy opt 1 w= 2) mex D5 2 min b= So 6G R412. outpat Ri Va= 3G wax T= 0.2, wm D0.) Se (tor 2Ry 4 Boo wr way {= Zoo kha At Zoth “han conpak i of variahay ef D awd fs, Dutpat 4 delonawes dahy cycle yariahan “Hersh V= Dv; > d= ve Vy may Da H=ou Ath De Ss ot Oubyit QA deler mes surehing Fepacner wandhing ! v= Diy 3 ~ /ye\® Re > 2 Je =) {.= —) sre z m “S bat dvs =\, Se ‘ . and hence fo Fe fe a> MAK fe occurs at R= 30-2 ta ) = geo big: cheese wn (F Ee = (BY 2S = tom Nx 2 “2 wax fs,