Class C Chopper is a combination of and Class C Chopper Class A Class B Choppers. For first quadrant operation, is ON or conducts. CH1 D2 For second quadrant operation, is ON or conducts. CH2 D1 When is ON, the load current is positive. CH1 The output voltage is equal to & the load receives power from the source. ‘V’ When is turned OFF, energy stored in inductance forces current to flow CH1 L through the diode and the output voltage is zero. D2 Current continues to flow in positive direction. When is triggered, the voltage forces current to flow in opposite direction CH2 E through L and . CH2 The output voltage is zero. On turning OFF , the energy stored in the inductance drives current through diode CH2 and the supply D1 Output voltage is the input current becomes negative and power flows from load to V, source. Average output voltage is positive Average output current can take both positive and negative values. Choppers should not be turned ON simultaneously as it would resultt CH1 & CH2 Class D Chopper Class D is a two quadrant chopper. When both and are triggered simultaneously, the output voltage and CH1 CH2 vO = V output current flows through the load. When and are turned OFF, the load current continues to flow in the same CH1 CH2 direction through load, and , due to the energy stored in the inductor L. D1 D2 Output voltage . vO = - V Average load voltage is positive if chopper ON time is more than the OFF time Average output voltage becomes negative if . tON < tOFF Hence the direction of load current is always positive but load voltage can be positive or negative.
Class C Chopper Class C Chopper is a combination of Class A and Class B Choppers. For first quadrant operation, CH1 is ON or D2 conducts. For second quadrant operation, CH2 is ON or D1 conducts. When CH1 is ON, the load current is positive. The output voltage is equal to ‘V’ & the load receives power from the source. When CH1 is turned OFF, energy stored in inductance L forces current to flow through the diode D2 and the output voltage is zero. Current continues to flow in positive direction. When CH2 is triggered, the voltage E forces current to flow in opposite direction through L and CH2 . The output voltage is zero. On turning OFF CH2 , the energy stored in the inductance drives current through diode D1 and the supply Output voltage is V, the input current becomes negative and power flows from load to source. Average output voltage is positive Average output current can take both positive and negative values. Choppers CH1 & CH2 should not be turned ON simultaneously as it would resultt Class D Chopper Class D is a two quadrant chopper. When both CH1 and CH2 are triggered simultaneously, the output voltage vO = V and output current flows through the load. When CH1 and CH2 are turned OFF, the load current continues to flow in the same direction through load, D1 and D2 , due to the energy stored in the inductor L. Output voltage vO = - V . Average load voltage is positive if chopper ON time is more than the OFF time Average output voltage becomes negative if tON < tOFF . Hence the direction of load current is always positive but load voltage can be positive or negative.
U6_L37-Class-C-Chopper.docx