09-05-2012, 12:59 PM
MICROCONTROLLER BASED PROGRAMMABLE DC-DC CONVERTER
DC DC.pdf (Size: 23.85 KB / Downloads: 41)
SINOPSIS:
The conversion of one DC level in to another DC level is known as DC-DC
converter. The output of the converter may be a step-down or step-up of a supplied DC
level. This kind of DC-DC converters are widely used in industries, Navy ships, railways,
etc; the main aim of this converter is to drive the various types of electronic equipments,
generally used in the ships & trains.
The proposed project work is designed to generate multiple DC levels from a
single supply source. The input source to this converter can be either from a solar panel
or from a battery. This converter is designed to operate at 12V DC. Using variable
voltage regulator at the converter output, different DC levels are derived. +3V, +5V, +9V,
+12V, +15V and +20V are the programmed outputs designed internally. Since it is
called as programmable, Micro controller chip is used for selecting the desired output
from the converter. A small keyboard is interfaced with micro controller, there by the
required voltage can be obtained from the converter by pressing the select key. A twodigit
display system is designed and it is also interfaced with micro controller, such that
output voltage can be displayed. Since the system is having six channels, six different
voltage levels can be displayed. Whenever any particular channel is selected through
keyboard, that particular voltage will be displayed automatically.
Here the controller is playing major role for selecting the voltage as well as controlling
the relays. By varying the reference voltage at adjust pin of LM 317 variable voltage
regulator, output voltage can be varied. For this purpose, potential dividing network is
designed and this network is connected through the relay contacts. By varying the value
of resistance in the network, output voltage also can be varied linearly. Since the operating
frequency is very high, using ferrite core can minimize output transformer size.
The converter is designed with PWM IC 3524. This is a most popular IC having all
required features for designing inverters, converters, SMPS etc; provision is made in
the oscillator, such that frequency and duty cycle can be varied linearly. Hear the
operating frequency is 20 KHz approximately, there by size and weight of entire power
system can be reduced. The PWM oscillator designed with 3524 offers dual inverted
outputs, the advantage of inverted outputs is, efficiency can be increased and continuous
output can be obtained.
The driver stage is designed using power MOSFETS, and it is configured in
push-pull mode of operation, so that no load current can be decreased and efficiency
can be increased. The output of the drive stage is fed to main out put transformer, this is
a step-up transformer with center-tapped primary generates 30V AC. The output of the
transformer is rectified & filtered, feed back loop is made for the regulated out put.