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Regulated Power Supply

Regulated Power Supply

A d.c. power supply which maintains the production voltage constant irrespective of a.c. mains oscillations or loading variations is known as regulated d.c. power supply.

Regulated Power Supply


A regulated power supply consists of an ordinary power supply and

voltage regulating device.

Fig-1 shows the block illustration of a regulated power force.

The output of ordinary power supply is fed to the voltage controller 

which produces the final affair.

The production voltage remains constant whether the cargo current changes 

or there are fluctuations in the input a.c. voltage.


Fig-2 shows the complete circuit of a regulated power force using zener diode as a voltage regulating device.

As you can see, the regulated power force is a combination of three circuits viz
(i) ground rectifier (ii) a capacitor sludge C and (iii) zener voltage controller.

The ground therapy converts the motor secondarya.c. voltage ( point P) into palpitating voltage ( point Q).

d.c. affair voltage ( point R). 

Ultimately, the zener voltage controller performs two functions. 

Originally, it reduces the variations in the filtered affair voltage.

Secondly, it keeps the affair voltage (Vout)
nearly constant whether the cargo current changes or there's change in inputa.c. voltage.

Fig-3 shows the waveforms at varied stages of regulated power force. 


Note that ground therapy and capacitor sludge constitute an ordinary power force.

Still, when voltage regulating device is add to
this ordinary power force, it turns into a regulated power force.


In practice, this type of controller is infrequently use.

The primary problem with the simple zener controller is the
fact that the zener wastes a tremendous quantum of power.

Practical voltage controllers contain a number of separate and/
or integrated active bias. 

Nonetheless, this circuit gives an idea about the regulated power force.

Need of Regulated Power Supply

In an ordinary power force, the voltage regulation is poor i.e. d.c. affair voltage changes appreciably with cargo current. 

Also, affair voltage also changes due to variations in the input a.c. voltage.

This is due to the following reasons

(i) In practice, there are considerable variations in a.c. line voltage caused
by outside factors beyond our control.

This changes the d.c. affair voltage.

Utmost of the electronic circuits will refuse to work satisfactorily on similar affair
voltage oscillations.

This necessitates to use regulated d.c. power force.

(ii) The internal resistance of ordinary power force is fairly large (> 30Ω). 

Thus, affair voltage is markedly affected by the quantum of cargo
current drawn from the force.

These variations in d.c. voltage may beget erratic operation of electronic circuits.

Thus, regulatedd.c. power force is the only result in similar situations.

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