DC-AC Power Inverter

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DC-AC Power Inverter
Design II, Spring 2004 Final Presentation
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Team Members
Min-Chiat Wee Team Leader
Daniel Martin Team Leader
Faculty Advisor Dr. Yaroslav Koshka
Dustin Bailey
Jason Horner
Industrial Advisor Dr. Mark Kinsler
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Objective

• Design a switch-mode power supply that converts
  12 VDC to 120 VAC
• Pure sinusoidal waveform with 60 Hz frequency
• 300 W continuous output power

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Problem Statement

• Problems
• Inexpensive inverters only produce a Modified
  Sine Wave
• Pure sine wave inverters have a high cost per
  watt ratio
• Solution
• An inexpensive inverter that produces a near
  perfect sine wave output

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Output Comparisons
Senior Design Packaged Product
Wal-Mart Modified Sine Wave
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Design Constraints
Name Description
Voltage Convert 12VDC to 120 VAC
Power Provide 300 W continuous
Efficiency gt 90 efficiency
Waveform Pure 60 Hz sinusoidal
Total Harmonic Distortion lt 5 THD
Physical Dimensions 8 x 4.75 x 2.5
Cost 175.00
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Main Components
12 VDC Input (from vehicle battery)
PWM Control Circuit
Half-bridge Converter
Transformer
Full-bridge Inverter
Sinusoidal PWM Controller
Low-pass Filter
120 VAC, 60 Hz, 300 W Output
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PWM Control Circuit
12 VDC Input (from vehicle battery)
PWM Control Circuit
Half-bridge Converter
Transformer
Full-bridge Inverter
Sinusoidal PWM Controller
Low-pass Filter
120 VAC, 60 Hz, 300 W Output
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PWM Control Circuit

• Produces two complementary pulses to control
  half-bridge transistors
• Changed driver from IR2181 to IR2184

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PWM Control Circuit Output
Prototype
Packaged Product
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Half-bridge Converter
12 VDC Input (from vehicle battery)
PWM Control Circuit
Half-bridge Converter
Transformer
Full-bridge Inverter
Sinusoidal PWM Controller
Low-pass Filter
120 VAC, 60 Hz, 300 W Output
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Half-bridge Converter

• Chops the 12 VDC to produce a 12 V, 100 kHz,
  square pulse

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Half-bridge Converter Output
Prototype
Packaged Product
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Transformer
12 VDC Input (from vehicle battery)
PWM Control Circuit
Half-bridge Converter
Transformer
Full-bridge Inverter
Sinusoidal PWM Controller
Low-pass Filter
120 VAC, 60 Hz, 300 W Output
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Step-Up Transformer

• Steps up voltage from
• 12 VAC (100kHz) to 340 VAC
• Customized transformer purchased and tested

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Transformer Load Handling Troubles

• Our first purchased transformer lost power due to
  a flux imbalance in the core
• Suggested Quick Fixes
• putting a capacitor in series with the primary
  winding of the transformer
• take the hardware off, take the cores apart, and
  put a gap (with paper) in between the two E-cores
  
• Required WCM to build another transformer

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Transformer Test Results
Transformer Output Voltage without Load Output Voltage with Load
Prototype 140 VAC 12 VAC
WCM Transformer 1 354 VAC 24 VAC
WCM Transformer 2 347 VAC 339 VAC

• Tests conducted using input from Half Bridge
  transistors (12VAC, 100kHz)
• 10 Measurements where taken and averaged

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DC-DC Converter Output
Packaged Product
Simulation
170 VDC
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Sinusoidal PWM Controller
12 VDC Input (from vehicle battery)
PWM Control Circuit
Half-bridge Converter
Transformer
Full-bridge Inverter
Sinusoidal PWM Controller
Low-pass Filter
120 VAC, 60 Hz, 300 W Output
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Sinusoidal PWM Controller

• Produces two sets of varying pulses 180 degrees
  out of phase with 18kHz switching frequency.
• Programmed 500ns of dead-time into the switching
  pulses.

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Sinusoidal PWM Controller Output
Packaged Product
Prototype
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Full-bridge Inverter
12 VDC Input (from vehicle battery)
PWM Control Circuit
Half-bridge Converter
Transformer
Full-bridge Inverter
Sinusoidal PWM Controller
Low-pass Filter
120 VAC, 60 Hz, 300 W Output
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Full-bridge Inverter

• Converts 170 VDC to a 120 Vrms, 60 Hz, sine wave

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Full Bridge Inverter Output (unfiltered)
Simulation
Packaged Product
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Frequency Spectrum Before Filtering
Simulation
Packaged Product
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Low-pass Filter
12 VDC Input (from vehicle battery)
PWM Control Circuit
Half-bridge Converter
Transformer
Full-bridge Inverter
Sinusoidal PWM Controller
Low-pass Filter
120 VAC, 60 Hz, 300 W Output
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Low-pass Filter

• 2nd order L-C filter
• Filters to retain a 60 Hz fundamental frequency
• Few components
• Handle current
• Wind inductor (fine tune)
• 64 turns of 18 AWG wire

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Frequency Spectrum After Filtering
Simulation
Packaged Product
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Final Output Testing
Simulation
Packaged Product
12VDC to 120VAC - PASS
60Hz Sinusoidal - PASS
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THD Constraint

• The Total Harmonic Distortion of a signal is the
  ratio of (a) the sum of the powers of all
  harmonic frequencies above the fundamental
  frequency to (b) the power of the fundamental
  frequency. 6
• Measurements for calculating the THD were made at
  the output of a device under no load.

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Component Costs
Item Item Quantity Price Per Quantity 10,000 Total Price
PCB Board PCB Board 1 X 6.00
PCB On-Board Components MOSFETs, Drivers, PWM Chips, PIC, Capacitors, Inductors, Resistors, Diodes, ETC. X X 23.38
PCB Off-Board Components Outlet 1 0.79 0.79
PCB Off-Board Components Cigarette Lighter Adapter 1 1.80 1.80
PCB Off-Board Components Switch 1 1.01 1.01
PCB Off-Board Components LED 1 0.05 0.05
PCB Off-Board Components Fan 1 1.20 1.20
PCB Off-Board Components Air Inlet Filter 1 0.20 0.20
PCB Off-Board Components Assorted Nuts and Bolts X 0.58 0.58
Case Case 1 7.10 7.10
Total 42.11
RETAIL PRICE 168.44 168.44 168.44 168.44
175 Cost Constraint - PASS
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PCB Layout
Midterm PCB
Final PCB
8 x 4.75 x 2.5 Size Constraint - FAIL
PCB Dimensions 7.5 x 6.5 x 2.5
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Efficiency and Power Constraints
300 Watts Continuous Power - FAIL
gt90 Efficiency - PASS
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Packaging
Midterm Packaging
Final Packaging
8 x 4.75 x 2.5 Size Constraint - FAIL
Final Packaging Size 9 x 6.5 x 2.5
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Packaged Product vs. Design Constraints
Name Design Constraint Packaged Product Results Pass/Fail
Voltage Convert 12VDC to 120 VAC 12VDC to 120VAC Pass
Power Provide 300 W continuous lt100 W continuous Fail
Efficiency gt 90 efficiency gt91 efficient Pass
Waveform Pure 60 Hz sinusoidal 60 Hz sinusoidal Pass
Total Harmonic Distortion lt 5 THD about 7 Fail
Physical Dimensions 8 x 4.75 x 2.5 9 x 6.5 x 2.5 Fail
Cost 175.00 168.44 Pass
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Acknowledgements

• Dr. Yaraslov Koshka
• Dr. Mark Kinsler
• Dr. Joseph Picone
• Dr. Mike Mazzola
• Dr. Raymond Winton
• Dr. Herb Ginn
• Jim Gafford
• Robin Kelley
• Len Cox
• Jessie Thomas
• Mike Wilson

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Any Questions?

• ???

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References

1. M. Brown, Power Supply Cookbook, 2nd ed. Boston
   Newnes, 2001.
2. I. R. Gottlieb, Design Build Electronic Power
   Supplies, Pennsylvania Tab Books, 1991.
3. Alan Sharps Home Page, Online. Available
   http//www.alansharp.co.uk/
4. Design of Switch Mode Power Supplies, Online.
   Available http//henry.fbe.fh-darmstadt.de/smps_e
   /smps_e.asp
5. M. P. Marcus, Switching Circuits For Engineers,
   3rd ed. New Jersey Prentice-Hall, Inc., 1975.
6. Definition total harmonic distortion, Online.
   Available http//www.its.bldrdoc.gov/fs-1037/dir-
   037/_5509.htm