Dr. Unnikrishnan P.C. Professor, EEE EE305 Power Electronics Dr. Unnikrishnan P.C. Professor, EEE

Step-Up Chopper

Step-Up Chopper Chopper Switch kept ON for tON . The inductor current increases and energy is stored in the inductor As the chopper is turned OFF at t= tON, the free wheeling diode is forward biased. The energy stored in the inductor and source voltage cause a current through the diode and the load. The energy stored in the inductor is thus transferred to the load Voltage appearing across the load is (VS+vL) , hence the name step-up Chopper

Analysis Mode 1:Chopper switch is turned ON

Analysis Mode 1:Chopper switch is turned ON

Analysis Mode 2:Chopper switch is turned OFF

Analysis Mode 2:Chopper switch is turned OFF Since 0<  <1, the output voltage, VO is always greater than the supply voltage, VO. When =0, VO = VS

Output Voltage Vs Duty Ratio