About Sine Pulse Width Modulation - PowerPoint PPT Presentation

Title: About Sine Pulse Width Modulation


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Sine Pulse Width Modulation (SPWM)
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Sine Pulse Width Modulation (SPWM)
Introduction

• Sinusoidal PWM has been a very popular technique
  used in AC motor control. This is a method that
  employs a triangular carrier wave modulated by a
  sine wave and the points of intersection
  determine the switching points of the power
  devices in the inverter.
• Though this method is unable to make full use of
  the inverters supply voltage and the
  asymmetrical nature of the PWM switching
  characteristics produces relatively high harmonic
  distortion in the supply it is still popular for
  its simplicity.

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Sine Pulse Width Modulation (SPWM)
Block Diagram
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Sine Pulse Width Modulation (SPWM)
Hardware Requirements

• 8051 series Microcontroller
• MOSFET
• Gate Driver
• Crystal Oscillator
• Toggle Switches
• Resistors
• Capacitors
• Diodes
• Transformer
• Regulator
• Opto-isolators

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Sine Pulse Width Modulation (SPWM)
Software Requirements

• Keil compiler
• Languages Embedded C or Assembly

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Sine Pulse Width Modulation (SPWM)
Power Supply
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Sine Pulse Width Modulation (SPWM)
Power Supply

• The 230V AC supply is first stepped down to 12V
  AC using a step down transformer.
• This is then converted to DC using bridge
  rectifier.
• The AC ripples is filtered out by using a
  capacitor and given to the input pin of voltage
  regulator 7805.
• At output pin of this regulator we get a constant
  5V DC which is used for MC and other ICs in this
  project.

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Sine Pulse Width Modulation (SPWM)
Microcontroller

• It is a smaller computer
• Has on-chip RAM, ROM, I/O ports.

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Sine Pulse Width Modulation (SPWM)
Features of Micro Controller

• 8K Bytes of In-System Programmable (ISP) Flash
  Memory
• 4.0V to 5.5V Operating Range
• Fully Static Operation 0 Hz to 33 MHz
• 256 x 8-bit Internal RAM
• 32 Programmable I/O Lines
• Three 16-bit Timer/Counters
• Eight Interrupt Sources
• Full Duplex UART Serial Channel

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Sine Pulse Width Modulation (SPWM)
Microcontroller Pin Description
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Sine Pulse Width Modulation (SPWM)
Power On Reset Circuit
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Sine Pulse Width Modulation (SPWM)
Opto-Isolator

• Opto coupler is a 6 pin IC. It is a combination
  of 1 LED and a transistor.
• Pin 6 of transistor is not generally used and
  when light falls on the Base-Emitter junction
  then it switches and pin5 goes to zero.
• If input of the diode is zero and other end of
  diode is GND then the output is one.

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Sine Pulse Width Modulation (SPWM)
Opto-Isolator

• When logic zero is given as input then the light
  doesnt fall on transistor so it doesnt conduct
  which gives logic zero as output.
• When logic 1 is given as input then light falls
  on transistor so that it conducts, that makes
  transistor switched ON and it forms short circuit
  this makes the output is logic zero as
  collector of transistor is connected to ground.

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Sine Pulse Width Modulation (SPWM)
MOSFET

• The MOSFET (Metal Oxide Semiconductor Field
  Effect Transistor) is a Voltage controlled
  device.   
• This means that a voltage at the gate control the
  current flows from the drain to the source.
• There are three terminals Gate - connected to
  the input device.
• Drain - connected to the positive, since
  electrons drain away to the positive. Source -
  the source of the electrons.

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Sine Pulse Width Modulation (SPWM)
MOSFET

• USES OF MOSFETS High power devices like motors
  and light bulbs give a large current output for a
  very tiny current input.  
• So a MOSFET can act as the interface between an
  integrated circuit that can give only a tiny
  current, and the motor that takes a big current.
   
• In complimentary pairs they are used in hi-fi
  power amplifiers.  
• They produce less distortion as they are more
  linear than bipolar transistors.
• Integrated circuits, as they can be made very
  compact.

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Sine Pulse Width Modulation (SPWM)
IR2101 Features

• Floating channel designed for bootstrap operation
  Fully operational to 600V Tolerant to negative
  transient voltage dV/dt immune.
• Gate drive supply range from 10 to 20V.
• Undervoltage lockout.
• 3.3V, 5V, and 15V logic input compatible.
• Matched propagation delay for both channels.
• Outputs in phase with inputs (IR2101) or out of
  phase with inputs (IR2102)

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Sine Pulse Width Modulation (SPWM)
IR2101 Description

• The IR2101(S)/IR2102(S) are high voltage, high
  speed power MOSFET and IGBT drivers with
  independent high and low side referenced output
  channels.
• Proprietary HVIC and latch immune CMOS
  technologies enable ruggedized monolithic
  construction.
• The logic input is compatible with standard CMOS
  or LSTTL output, down to 3.3V logic.
• The output drivers feature a high pulse current
  buffer stage designed for minimum driver
  cross-conduction.

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Sine Pulse Width Modulation (SPWM)
Working

• A star lamp load can be used to view the waveform
  only. This project uses an 8051 family
  microcontroller duly interfaced to the
  Opto-isolators for feeding to the bridge drivers.
  3 nos of dual bridge drivers are used to feed 3
  phase bridge inverter with the DC supply
  developed from single phase AC after
  rectification.
• Powering the circuit is achieved by a pair of
  control transformers with bridge rectifier and
  filter capacitors. One set of this power is used
  for the microcontroller and the other one is used
  for driving circuits of the three phase bridge.

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Sine Pulse Width Modulation (SPWM)
The working principle of SPWM includes the
following points

• The frequency of triangular wave is the frequency
  of PWM.
• Frequency of control voltage controls the
  fundamental frequency.
• The peak value of control voltage controls the
  amplitude.
• Modulation Index is defined by
• Where Vao1 Fundamental component of Vao.

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Sine Pulse Width Modulation (SPWM)
The working principle of SPWM includes the
following points

• For Phase A
• If Vcontrol gt Vtriangle then Vao Vd/2.
• If Vcontrol lt Vtriangle then Vao -Vd/2.

• For Phase B
• If Vcontrol gt Vtriangle then Vbo Vd/2.
• If Vcontrol lt Vtriangle then Vbo -Vd/2.
• For Phase C
• If Vcontrol gt Vtriangle then Vco Vd/2.
• If Vcontrol lt Vtriangle then Vco -Vd/2.

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Sine Pulse Width Modulation (SPWM)
Advantage

• The main advantage of PWM is that power loss in
  the switching devices is very low.
• When a switch is off there is practically no
  current, and when it is on, there is almost no
  voltage drop across the switch.
• Power loss, being the product of voltage and
  current, is thus in both cases close to zero.
• PWM also works well with digital controls, which,
  because of their on/off nature, can easily set
  the needed duty cycle.

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Sine Pulse Width Modulation (SPWM)
Applications

• In many industrial applications, Sinusoidal Pulse
  Width Modulation (SPWM), is used to control the
  inverter output voltage.
• SPWM maintains good performance of the drive in
  the entire range of operation between zero and 78
  percent of the value that would be reached by
  square-wave operation.
• If the modulation index exceeds this value,
  linear relationship between modulation index and
  output voltage is not maintained and the
  over-modulation methods are required.

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Sine Pulse Width Modulation (SPWM)
Conclusion

• For the generation of pure sinusoidal signal,
  SPWM is the most popular technique. In SPWM a
  digital waveform is generated and the duty cycle
  is modulated such that the average voltage of the
  waveform is corresponds to a pure sine wave. SPWM
  moves the voltage harmonic components to the
  higher frequencies. The SPWM technique treats
  each modulating voltage as a separate signal and
  compared to the common carrier triangular
  waveform.

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