b-10.dc-ac pure sine wave inverter using bubba oscillator
TRANSCRIPT
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DC/AC Pure Sine WaveInverter
Section-B:
Batch No: 10
ANIL .R(07241A0258)MAHENDRA.P(07241A0275)
VAMSI KRISHNA.L(07241A02B4)
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Inverter
Power inverters are devices which can convert
electrical energy of DC form into that of AC.
On the market today are two different types of power
inverters, modified sine wave and pure sine wave
generators. These inverters differ in their outputs,
providing varying levels of efficiency and distortion
that can affect electronic devices in different ways.
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OUR OBJECTIVE
Our goal is to fill a niche which seems to be lacking
in the power inverters market, one for a fairly
efficient, inexpensive inverter with a pure sine wave
output.
Utilizing PWM and analog components, the output
will be a clean sinusoid, with very little switching
noise, combined with the inexpensive manufacturing
that comes with an analog approach.
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COMPOSITION
The major task of generating a pure sine wave is viewedas the summation of outputs obtained from:
Bubba oscillator(Reference sine wave generator)
Carrier wave generator Pulse width modulation
H-bridge with MOSFET drivers
Snubber circuit and filters
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Bubba Oscillator
The Bubba Oscillator is a circuit that provides a
filtered sine wave of any frequency the user desires
based upon the configuration of resistors and
capacitors in the circuit. The circuit completes this task with four operational
amplifiers that either buffer or amplify the signal and
produce a total 180 shift.
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Output
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Carrier Wave Generator
Generating a sine wave at 50Hz requires both the
reference sine wave and a carrier wave at the
switching speed of the power supply.
Carrier waves can be either saw tooth or triangularsignals; in this case, a triangular wave will be used.
The operation of this device is based on basic Schmitt
Trigger and Integrator circuits.
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Output
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Pulse Width Modulation
Analog PWM control requires the generation of both
reference and carrier signals that feed into a
comparator which creates output signals based on the
difference between the signals. The reference signal is sinusoidal and at the
frequency of the desired output signal, while the
carrier signal is often either a sawtooth or triangular
wave at a frequency significantly greater than the
reference.
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When the carrier signal exceeds the reference, the comparator
output signal is at one state, and when the reference
is at a higher voltage, the output is at its second state.
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H-Bridge Configuration
An H-bridge converter is a switching configuration
composed of four switches in an arrangement that
resembles an H.
By controlling different switches in the bridge, apositive, negative, or zero potential voltage can be
placed across a load.
The use of P-channel MOSFETs on the high side and
N-Channel MOSFETs on the low side is easier.
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H-Bridge with N-channel
MOSFETS
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The MOSFET driver on the left side of the bridge will
receive a square wave and the right side will receive the
PWM signal.
Square wave will control the polarity of the output sine wave,
while the PWM signal will control the amplitude.
Now, using an H-Bridge MOSFET configuration, and
utilizing both the above PWM signal and the square wave
generated, we can obtain unfiltered output signal at the load.
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Snubber circuit
One of the major factors in any electronic device is its
ability to protect itself from surges that could damage
the circuitry.
In the case of the inverter, inductive loads can causespecial problems
To combat this problem snubber circuits can reduce
or eliminate any severe voltages and currents.
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Filters
In this inverter , we preferpassive filter than active
filters.
L-C filter
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Block diagram of pure sine wave
inverter
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Total Circuit Diagram
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Final Output at the filter
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Applications
The purpose of a DC/AC power inverter is typically to take
DC power supplied by a battery, such as a 12 volt car battery,
and transform it into a AC power source emulating the power
available at an ordinary household electrical outlet.
Power inverters are used today for many tasks like powering
appliances in a car such as cell phones, radios and televisions.
They also come in handy for consumers who own camping
vehicles, boats and at construction sites where an electric grid
may not be as accessible to hook into.
Inverters allow the user to provide AC power in areas where
only batteries can be made available, allowing portability and
freeing the user of long power cords.
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Simulation part of
the circuits
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Simulation of bubba oscillator
circuit
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Output
R = 33Kohm, C = 100nF then Freq = 50HZ
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R = 26.7Kohm, C = 100nF then Freq = 60HZ
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R = 15Kohm, C = 150nF then Freq = 70HZ
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Simulation of carrier wave circuit
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OutputRtot = 100 Kohm , C = 200 pF, Freq = 2 KHZ
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Rtot = 8.2 Kohm , C = 100 pF, Freq = 50 KHZ
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Rtot = 50 Kohm , C = 150 pF, Freq = 8 KHZ
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Simulation of PWM circuit
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Output
B.O : R=33Kohm, C=100nF
C.G : Rtot = 50Kohm , C= 200pF
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B.O : R=26.7Kohm, C=100nF
C.G : Rtot = 50Kohm , C= 150pF
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B.O : R=15Kohm, C=150nF
C.G : Rtot = 100Kohm , C= 200pF
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B.O : R=15Kohm, C=150nF
C.G : Rtot = 8.2Kohm , C= 100pF
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List of major components
Op amps:
LM348
TL084MC3302
IR2110(Mosfet driver)
IR549P Mosfet
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LM348
Pin diagram : Ratings :
Supply voltage :
Vcc : -18 to +18 V
Input voltage :Vi : -18 to +18 V
Differential Input Voltage :
Vi(Diff) : 36 V
Operating & storage
Temperature :
0 to +70 C & -65 to 150 C
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TL084
Pin Diagram : Ratings :
Supply voltage :
Vcc : -18 to +18 V
Input voltage :
Vi : -15 to +15 V
Differential Input Voltage :
Vi(Diff) : -30 to +30 V
Power Dissipation :
P(tot) : 680mw
Operating & storageTemperature :
0 to +70 C & -65 to 150 C
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MC3302
Pin Diagram : Ratings :
Supply voltage :
Vcc : -15 to +15 V
Input Differential VoltageRange :
Vidr : 30 V
Power dissipation :
Pd: 1 W
Operating & storage
Temperature :
-40 to 85 C & -65 to 150 C
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IR2110
Pin Diagram : Ratings :
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Hardware work
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Bubba Oscillator
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Carrier wave generator
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PWM pulse generator
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H-Bridge configuration of MOSFETS
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Output of bubba oscillator circuit
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Output of carrier wave generator
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Conclusion
After the total connections of internal
circuits,the obtained reference sine wave and
triangular waves are sent to the PWM
generator circuit,from which the accuratePWM pulses are obtained with disturbances
which couldnt properly drive the MOSFET
drivers to give the desired output.
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Scope of the project
This project is a stepping stone to a cheaperand efficient pure sine wave inverter.
Using the data collected in this report as well
as the schematics and recommendations theproduct produced here can be improved
upon.
Simple additions such as circuit protection anda closed loop control system could greatly
improve the performance of this project.