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DC-AC Power Inverter Design II, Spring 2004 Midterm Presentation.

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Presentation on theme: "DC-AC Power Inverter Design II, Spring 2004 Midterm Presentation."— Presentation transcript:

1 DC-AC Power Inverter Design II, Spring 2004 Midterm Presentation

2 Team Members Daniel Martin Dustin Bailey Min-Chiat Wee Team Leader Jason Horner Faculty Advisor Dr. Yaroslav Koshka Industrial Advisor: Dr. Mark Kinsler

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

4 Problem Statement Problems: –Inexpensive inverters are very inefficient due to a high harmonic content of the output signal –Pure sine wave inverters have a high cost per watt ratio Solution: –An inexpensive inverter that produces a near perfect sine wave output

5 Design Constraints NameDescription VoltageConvert 12VDC to 120 VAC PowerProvide 300 W continuous Efficiency> 90% efficiency WaveformPure 60 Hz sinusoidal Total Harmonic Distortion< 5% THD Physical Dimensions8” x 4.75” x 2.5” Cost$175.00

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

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

8 PWM Controller Produces two complementary pulses to control half-bridge transistors Problem: – Voltage dropped less than 170VDC when the input voltage was decreased Solution: –A feedback network was added for voltage regulation

9 PWM Oscilloscope Waveform PrototypeDevice as Built

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

11 Half-bridge Converter Chops the 12 VDC to produce a 12 V, 100 kHz, square pulse Problem: –IRF740A MOSFETs has an Rds(on) = 0.55Ω, resulting in high power losses. Solution: –Chose IRF530 MOSFETs with an Rds(on) = 0.16 Ω

12 Half-bridge Oscilloscope Readings Device As Built Prototype

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

14 Step Up Transformer Steps up voltage from 12 VAC to 340 VAC Problem: –Initial transformer had high internal capacitance leading to failure of device Solution: –Custom ordered a transformer to fit our design constraints

15 DC-DC Converter Schematic

16 DC-DC Converter Testing Simulation Device As Built

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

18 Sinusoidal PWM Circuit Last Semester: PIC18F452 – too many unused ports Insufficient dead-time in PIC program caused cross- conduction in full-bridge inverter This Semester: Chose PIC18F252 – fewer unused ports Programmed 500ns between each control pulse

19 Software Flow Diagram Initialize all variables Count0 = 300 (300 duty cycles) Has duty cycle been reached? Output 1 = high, Output 2 = low Read duty cycle table (increment pointer) Output 1 = low, Output 2 = high 300 duty cycle values? Decrement Count0 by 1 Duty cycle and sampling period timer One Sampling Period? noyes no yes no

20 Sinusoidal PWM Drive Pulses Device As Built Simulation

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

22 Full-bridge Inverter Converts 170 VDC to a 120 Vrms, 60 Hz, sine wave IRF740A MOSFETs –Vdss = 400 V –Id = 10 A –Rds(on) = 0.55 Ω

23 Simulation vs. Actual (unfiltered) SimulationDevice As Built

24 Frequency Spectrum Before Filtering 18 kHz 60 Hz SimulationDevice As Built 60 Hz

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

26 Low-pass Filter 2 nd order L-C filter –Filters to retain a 60 Hz fundamental frequency –Few components –Handle current –Wind inductor (fine tune)

27 DC-AC Full-bridge Inverter Schematic

28 Final Output Testing SimulationPrototype

29 Frequency Spectrum After Filtering SimulationDevice As Built

30 Component Costs ItemQuantity (per unit 10,000)Price PIC18F2521$2.66 transformer1$2.20 driver2$1.80$3.60 inductor1$1.71 capacitor1$1.59 inductor1$1.59 MC340251$1.40 MOSFET2$1.17$2.34 capacitor1$1.17 MOSFET2$0.79$ MHz oscillator1$0.70 diode5$0.33$1.65 capacitor2$0.20$0.40 capacitor5$0.11$0.55 Misc.x$17.81 capacitor2$0.10$0.20 resistor1$0.02 diode1$0.02 Total $41.19

31 PCB Layout Dimensions: 7.5” x 6.5” x 2.5”

32 Packaging

33 Status and Goals Continue working with PCB Fine tune filter Improve packaged appearance Attempt to further reduce costs

34 Acknowledgements Dr. Yaraslov Koshka Dr. Mark Kinsler Dr. Mike Mazzola Dr. Raymond Winton Dr. Herb Ginn Jim Gafford Robin Kelley Len Cox Jessie Thomas

35 Any Questions? ???


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