Question

Give a block diagram of a power supply unit with all components. Explain briefly why the capacitive input filter is preferred over the choke input filter?

Answer 1

At the input of power supply a transformer is used to step down the voltage as per need and is known as power transformer. It is followed by a diode circuit called rectifier the pulsating DC output of the rectifier is fed to the filter circuit which remove the pulsation and smooth it out. at the end a regulator is used to obtain regulated DC at the output.

the output of a rectifier is pulsating and contain steady DC component with undesirable repels if such a pulsating DC is given to the electronic circuit it will produce Hum disturbance. Therefore the AC component or ripples has to be kept away from the load this is achieved by using a filter circuit in between the rectifier and the load. The capacitive input filter is preferred over choke input filter because capacitor not only remove the AC component from the output but it also improves the output voltage the smoothness and magnitude of output voltage depend upon the constant CRload the longer the time period the stadia the output voltage this can be achieved by using a large value of capacitor. It also increases the average magnitude of output voltage because of its charging and discharging action Where as the output voltage at the load is slightly reduced because of the drop in the resistance of the inductor the inductor is more bulky and large in size occupies more space and increase the weight of the filter circuit.