Question

Question 1 For the flyback converter shown in Fig. 1, Vin is 30 V, Vout is 8 V, the output power is 30 w, 30 turns are fitted to winding Ww1, 15 turns are fitted to winding W2, the inductance of W1, L1, is 50 uH and the switching frequency is 200 kHz. The flyback converter operates in continuous conduction mode. Calculate the time for which S1 is switched on a. b. Calculate Aisı during the time S1 is switched on c. Calculate is1_min, isı_pk, is2_min and is2_pk, as shown in Fig. 2 d. Calculate the minimum blocking voltage rating needed for S2, assuming no transient voltages are generated when it switches on and off. S2 Vin Vout Load W2 C Si Fig. 1 is_pk is min isl_pk i min Fig. 2

Answer 1

+ly BACK Conuerter i. AN S2 HhoS 301S Load Yout -bvolt utyra tio Let D be Vin Ton doo KHz Ton 3T L's. NN2 in for fyback Convester N2 Lis dotted teminal ofwinding then when Switeh s y on, dot teminal wiil ngatie polamfy have negative po lanfy S2 W2 So haue si is off also therefore izo egual to zero So 3o y Cwifeh on oltage demss w, duuig

smnzياin t T isimin- T Nin t 1s2-p Ismin when Switch s, is on then Szis o across it- Vs,- 2-No the veverse -Vo -N Vin Kalue of clty rati the Caleulating

(39 3,6 1 -2 8-8D- 1SD tia D= 8 duty 3 (4) Time S, s on To n Ton =1.73913 s T= 200x 103 during VLw Vin: Lun at on diu Ais - (501) 30 = Ton 30 x 73513 x1 Ais,= aiw, = A 91X as (c) Let averye Curent thaugh nduitr Lw, be IĻ SouTLe Cument: (I') ( So flows for o time only. Soure curent in aas assumed to be ideal ave au companents Seuve pwer = output power z 30 w So Vin(T)30

IL = 30 IL 23 Q-B 75 A So wp Is_pK = IL Is, Pr o 43478 = 3.39 67 A <. 87S Iwmin Is,_min = IL-Aiw, s 875- 1-o4378 Ts, _min a d.3531 A duting (S. Swifch s S tts when So (Curent 4houh Sw ifch NL N2 N2 S is of in ductor Lurent il fows hen thogh primayin duig Such tha N2

So N2 = 6.793 A isspe So Зо 1 ismin sin = N_(\Lw,)min = is2_m Nou N2 Nz. 4.7062A 30 x.3 S31 Sa ainaffstate mode i.e blacking S, is in ': when Fiven by doss it Vs, is -Vo -N21 vin NI 'IS 30 = 23 volts So СяраЫе to block 3olts So Suith S2 Shol Id be voltge of te Teverse