Yeah I came to know the answer. Since in Multisim, the switches are interactive in nature so, in order to set the switching frequency, we have to use a transistor and apply a Clock Voltage to its source. We can then set the desired frequency in clock voltage source and get the required output.
I am a new user of Multisim and I am trying to make a buck converter. In other softwares, such as pspice I was able to control the switching frequency by editing properties but in Multisim, most of the switches are user interactive. I want to set frequency of 50 Hz in a switch. Kindly help me...