14-01-2013, 02:56 PM
design a dc regulated power supply circuit for regulated Voltage of +5V and -5V
dc regulated power supply circuit.docx (Size: 447.09 KB / Downloads: 73)
THEORY:
A regulated power supply is an embedded circuit, or stand alone unit, the function of which is to supply a stable regulated voltage (or less often current), to a circuit or device that must be operated within certain power supply limits. The output from the regulated power supply may be alternating or unidirectional, but is nearly always DC (Direct Current).
Regulated DC power supplies provide accurate DC voltage, which are derived from AC mains. These DC supplies are cheaper in nature than the DC sources from battery . Such supplies provide constant voltage irrespective of load variations for which they are designed. DC power supplies are used extensively in various electronics laboratories,
industries and communication departments to feed DC voltage to the electronic modules.
DESCRIPTION OF COMPONENTS:
The major blocks of power supply are given below
• Transformer
• Bridge Rectifier
• 7805 ,7905 voltage regulator
TRANSFORMER:
A transformer is a power converter that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field through the secondary winding. This varying magnetic field induces a varying electromotive force (EMF), or "voltage", in the secondary winding. This effect is called inductive coupling.
The transformer is based on two principles: first, that an electric current can produce a magnetic field (electromagnetism) and second that a changing magnetic field within a coil of wire induces a voltage across the ends of the coil (electromagnetic induction). Changing the current in the primary coil changes the magnetic flux that is developed. The changing magnetic flux induces a voltage in the secondary coil Ideal transformer equation
DIODE BRIDGE RECTIFIER:
A diode bridge is an arrangement of four (or more) diodes in a bridge circuit configuration that provides the same polarity of output for either polarity of input. When used in its most common application, for conversion of an alternating current (AC) input into a direct current(DC) output, it is known as a bridge rectifier. A bridge rectifier provides full-wave rectification from a two-wire AC input.
In the diagrams below, when the input connected to the left corner of the diamond is positive, and the input connected to the right corner is negative, current flows from the upper supply terminal to the right along the red (positive) path to the output, and returns to the lower supply terminal via the blue (negative) path.
VOLTAG REGULATOR:
Voltage regulators produce fixed DC output voltage from variable DC (a small amount of AC on it). Normally we get fixed output by connecting the voltage regulator at the output of the filtered DC (see in above diagram). It can also used in circuits to get a low
DC voltage from a high DC voltage (for example we use 7805 to get 5V
from 12V). There are two types of voltage regulators: fixed and variable voltage regulator.
In fixed voltage regulators there is another classification
1. +ve voltage regulators
2. -ve voltage regulators
POSITIVE VOLTAGE REGULATOR:
This include 78xx voltage regulators. The most commonly used ones are
7805 and 7812. 7805 gives fixed 5V DC voltage if input voltage is in
(7.5V,20V). You may sometimes have questions like, what happens if
input voltage is <7.5 V or some 3V, the answer is that regulation won't be
proper. Suppose if input is 6V then output may be 5V or 4.8V, but there are
some parameters for the voltage regulators like maximum output current
capability, line regulation etc..