Principle of chopper circuit

It is a simple chopper circuit.
In this manner, a chopped load voltage is obtained from a constant dc supply of magnitude Vs . In this chopper is represted by a switch SW inside dotted rectangle, which may be turned-on or turned-off as desired. For the sake of highlighting the principle of choper operation The circuitry used for controlling the on,off periods of this switch is not shown. During the period Ton, chopper is on and load voltage is equal to source voltage Vs. During the interval Toff, chopper is off, load current flows through the freewheeling diode FD. As a result, load terminals are short circuited by FD and load voltage is therefore zero during Toff. In this manner, a chopper dc voltage is produced at the load terminals. The load current is continuous. During Ton, load current rises whereas durin Toff load current decays.
The load voltage controlled by varying duty cycle.