GATE 2014 EE (EE2) – Question 34
An ideal step-up chopper supplies 400 V DC from 250 V DC with continuous inductor current. Switch off-time is 20 µs. Find switching frequency (kHz).
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Correct answer: 31.0 to 31.5
Explanation
For continuous-conduction ideal boost conversion,Vo=Vin/(1−D). Thus the off fraction1−D=250/400=0.625. Since toff=(1−D)T=20µs,T=32µs and f=1/T=**31.25kHz**. The20µsquantity is only the off interval,not the full period.