21-05-2014, 11:47 AM
POWER SUPPLY
POWER SUPPLY .pptx (Size: 1.35 MB / Downloads: 23)
NEED OF POWER SUPPLY
Almost all electronic devices used in electronic circuits need a dc source of power to operate.
For portable low-power systems batteries may be used, but their operating period is limited.
POWER SUPPLY
Electronic equipment is energized by a power supply:
>Derived from the standard industrial or domestic ac supply by transformation, rectification, and filtering.
>The combination of a transformer, a rectifier and a filter constitutes an ordinary dc power supply
UNREGULATED POWER SUPPLY
This power supply does not produce a constant output.
It consists of:
> A.C Power supply
> Transformer
> Rectifier
> Filter
Transformer
In India, single-phase ac supply is available at 230 V. a small dc voltage, in the range of 2—24 volts is required for the operation of different electronic circuits, So a small step-down transformer is used at the beginning which reduces the voltage level according to the needs.
Filter
A filter block which reduces the ripples (ac components) from the rectifier output voltage.
The filter is a device which passes dc component to the load and blocks ac components of the rectifier output.
Regulated Power Supply
Regulated power supply is an electronic circuit that is designed to provide a constant dc voltage of predetermined value across load terminals irrespective of ac mains fluctuations or load variations.
Series or linear Voltage regulator
A simple series voltage regulator using an NPN transistor and a OP-AMP working as Comparator. This circuit is called a series regulator because collector and emitter terminals of the transistor are in series with the load.