Working principle of step down chopper RL load(highly inductive)
A buck converter (dc-dc) is shown in Figure. A diode (termed as freewheeling) is used to allow the load current to flow through it, when the switch (i.e., a device) is turned off. The load is inductive (R-L) one. Also a diode (termed as freewheeling) is used to allow the load current to flow through it, when the switch (i.e., a device) is turned off. The load is inductive (R-L) one. Due to the load inductance, the load current must be allowed a path, which is provided by the diode; otherwise, i.e., in the absence of the above diode, the high induced emf of the inductance, as the load current tends to decrease, may cause damage to the switching device. If the switching device used is a thyristor, this circuit is called as a step-down chopper, as the output voltage is normally lower than the input voltage. When chopper is ON, supply is connected across load. Current flows from supply to load. When chopper is OFF, load current continues to flow in the same direction through FWD due to energy stored in inductorâ€˜Lâ€™ . Load current can be continuous or discontinuous depending on the values of â€˜Lâ€™ and duty cycle â€˜dâ€™ For a continuous current operation, load current varies between two limits Imax and Imin. When current becomes equal to Imax the chopper is turned-off and it is turned-on when current reduces to Imin.
Average output Voltage: