DC-AC Power InverterTeam MembersAbstractProblem StatementDesign ConstraintsMain ComponentsPWM Control CircuitPWM ControllerPWM Oscilloscope WaveformHalf-bridge ConverterSlide 11Half-bridge Oscilloscope ReadingsTransformerStep Up TransformerDC-DC Converter SchematicDC-DC Converter TestingSinusoidal PWM ControllerSinusoidal PWM CircuitSoftware Flow DiagramSinusoidal PWM Drive PulsesFull-bridge InverterSlide 22Simulation vs. Actual (unfiltered)Frequency Spectrum Before FilteringLow-pass FilterSlide 26DC-AC Full-bridge Inverter SchematicFinal Output TestingFrequency Spectrum After FilteringComponent CostsPCB LayoutPackagingStatus and GoalsAcknowledgementsAny Questions?DC-AC Power Inverter DC-AC Power Inverter Design II, Spring 2004Midterm PresentationTeam Members Team Members Daniel MartinDustin BaileyMin-Chiat WeeTeam LeaderJason HornerFaculty AdvisorDr. Yaroslav KoshkaIndustrial Advisor: Dr. Mark KinslerAbstractAbstract•Design a switch-mode power supply that converts 12 VDC to 120 VAC•Pure sinusoidal waveform with 60 Hz frequency•300 W continuous outputProblem StatementProblem 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 outputDesign ConstraintsDesign ConstraintsName DescriptionVoltage Convert 12VDC to 120 VACPower Provide 300 W continuousEfficiency > 90% efficiencyWaveform Pure 60 Hz sinusoidalTotal Harmonic Distortion < 5% THDPhysical Dimensions 8” x 4.75” x 2.5” Cost $175.00Main ComponentsMain ComponentsFull-bridge InverterSinusoidal PWMControllerLow-passFilterPWM ControlCircuitHalf-bridgeConverterTransformer12 VDC Input(from vehicle battery)120 VAC,60 Hz, 300 WOutputPWM Control CircuitPWM Control CircuitFull-bridge InverterSinusoidal PWMControllerLow-passFilterPWM ControlCircuitHalf-bridgeConverterTransformer12 VDC Input(from vehicle battery)120 VAC,60 Hz, 300 WOutputPWM ControllerPWM 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 regulationPWM Oscilloscope WaveformPWM Oscilloscope WaveformPrototype Device as BuiltHalf-bridge ConverterHalf-bridge ConverterFull-bridge InverterSinusoidal PWMControllerLow-passFilterPWM ControlCircuitHalf-bridgeConverterTransformer12 VDC Input(from vehicle battery)120 VAC,60 Hz, 300 WOutputHalf-bridge ConverterHalf-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 ΩHalf-bridge Oscilloscope ReadingsHalf-bridge Oscilloscope ReadingsDevice As BuiltPrototypeTransformerTransformerFull-bridge InverterSinusoidal PWMControllerLow-passFilterPWM ControlCircuitHalf-bridgeConverterTransformer12 VDC Input(from vehicle battery)120 VAC,60 Hz, 300 WOutputStep Up TransformerStep 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 constraintsDC-DC Converter SchematicDC-DC Converter SchematicDC-DC Converter TestingDC-DC Converter TestingSimulationDevice As BuiltSinusoidal PWM ControllerSinusoidal PWM ControllerFull-bridge InverterSinusoidal PWMControllerLow-passFilterPWM ControlCircuitHalf-bridgeConverterTransformer12 VDC Input(from vehicle battery)120 VAC,60 Hz, 300 WOutputSinusoidal PWM CircuitSinusoidal 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 pulseSoftware Flow DiagramSoftware Flow DiagramInitialize all variablesCount0 = 300 (300 duty cycles)Has duty cycle been reached?Output 1 = high, Output 2 = lowRead duty cycle table (increment pointer) Output 1 = low, Output 2 = high300 duty cycle values?Decrement Count0 by 1Duty cycle and sampling period timerOne Sampling Period?no yesyesnoyesnoSinusoidal PWM Drive PulsesSinusoidal PWM Drive PulsesDevice As BuiltSimulationFull-bridge InverterFull-bridge InverterFull-bridge InverterSinusoidal PWMControllerLow-passFilterPWM ControlCircuitHalf-bridgeConverterTransformer12 VDC Input(from vehicle battery)120 VAC,60 Hz, 300 WOutputFull-bridge InverterFull-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 ΩSimulation vs. Actual (unfiltered)Simulation vs. Actual (unfiltered)Simulation Device As BuiltFrequency Spectrum Before FilteringFrequency Spectrum Before Filtering18 kHz18 kHz60 HzSimulation Device As Built60 HzLow-pass FilterLow-pass FilterFull-bridge InverterSinusoidal PWMControllerLow-passFilterPWM ControlCircuitHalf-bridgeConverterTransformer12 VDC Input(from vehicle battery)120 VAC,60 Hz, 300 WOutputLow-pass FilterLow-pass Filter•2nd order L-C filter–Filters to retain a 60 Hz fundamental frequency–Few components–Handle current–Wind inductor (fine tune)DC-AC Full-bridge Inverter SchematicDC-AC Full-bridge Inverter SchematicFinal Output TestingFinal Output TestingSimulation PrototypeFrequency Spectrum After FilteringFrequency Spectrum After FilteringSimulation Device As BuiltComponent CostsComponent CostsItem Quantity (perunit10,000) PricePIC18F252 1 $2.66 $2.66transformer 1 $2.20 $2.20driver 2 $1.80 $3.60inductor 1 $1.71 $1.71capacitor 1 $1.59 $1.59inductor 1 $1.59 $1.59MC34025 1 $1.40 $1.40MOSFET 2 $1.17 $2.34capacitor 1 $1.17 $1.17MOSFET 2 $0.79 $1.5840 MHz oscillator 1 $0.70 $0.70diode 5 $0.33 $1.65capacitor 2 $0.20 $0.40capacitor 5 $0.11 $0.55Misc. x $17.81 $17.81capacitor 2 $0.10 $0.20resistor 1 $0.02 $0.02diode 1 $0.02 $0.02Total $41.19PCB LayoutPCB LayoutDimensions: 7.5” x 6.5” x 2.5”PackagingPackagingStatus and GoalsStatus and Goals•Continue working with PCB•Fine tune filter•Improve packaged appearance•Attempt to further reduce costsAcknowledgementsAcknowledgements•Dr. Yaraslov Koshka•Dr. Mark Kinsler•Dr. Mike Mazzola•Dr. Raymond Winton•Dr. Herb Ginn•Jim Gafford•Robin Kelley•Len Cox•Jessie ThomasAny Questions?Any Questions?
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