Multiple-Output, Variable-Output DC Power Supply - Phase 2 May 04-08 http://seniord.ee.iastate.edu/may0408/

Multiple-Output, Variable-Output DC Power Supply Client Senior Design Dr. Lamont Prof Patterson Advisors Dr. Potter Dr. Ajjarapu Team Members Benjamin Voetberg, EE Fares Karadsheh, EE Trung Nguyen, EE Darrell Long, EE Senior Design :: May 04-08

Overview Project objectives & guidelines Design Approach End Result Create low cost dc power supply Range of voltages Design Approach ac to dc End Result What the team accomplished Budget Price comparison Layout of cost Schedule Project Evaluation Risk and Risk Management Senior Design :: May 04-08

Project Objectives & Guidelines The project is to design a DC power supply that provides power at various voltages +/- voltages will include 5V, 6V, 12V, 18V +/common voltages will include 1.5V, 3.0V, 3.2V, 3.3V, 4.5V, 5V, 6V, 7.5V, 9V, 12V, 15V, 18V, 24V Voltmeter and Ammeter to display output values Between 2 to 4 output terminals. Senior Design :: May 04-08

Project Objectives and Guidelines Cont. Operating Environment Indoor use for senior design projects Intended users/uses Students enrolled in EE/CprE senior design Possibility for use in freshman and sophomore level labs Used to test senior design projects that require DC voltage Assumptions/Limitations Powered by a 120V, 60Hz wall outlet +/- 1% ripple output voltage Function with +/- 5% of wall outlet voltage Output current not to exceed 1A on each terminal Senior Design :: May 04-08

Design Approach Definitions PWM : Pulse Width Modulation Duty Ratio (D) : Time ON divided by the total time Lm : Magnetizing Inductance of a transformer For the simulation, 2 choice: Pspice: Available and have a lot of parts Electronic Work Bench : Easy and more visual Sample from the simulation Electronic Work Bench was used to simulate the design Senior Design :: May 04-08

Design Approach Buck Converter Simple ac/dc conversion Convert ac to dc using bridge rectifier Buck converter is used to vary the voltage to get desired voltage output Buck converter output Vo=Vs*D Buck converter diagram

Design Approach Flyback Converter Not able to make 1.5-24 volts directly from 120 V Use a flyback converter Flyback converter output equation Vo=Vs(D/(1-D)) N2/N1 Senior Design :: May 04-08

Design Approach PWM Output equations: Vo=Vs(D/(1-D)) N2/N1 (Flyback) Vo=Vs*D ( Buck ) PWM : Generate a square wave. (see figure) Trig.source Comparator The Reason behind using Flyback then a __buck converter is to create an isolation. Senior Design :: May 04-08

Design Approach Taken A commercial power supply to replace bridge rectifier flyback converter. Power supply eliminates problems Current and the voltage regulation Difficulty finding transformer Saved time Even with changes still functions as the simulation Buck converter still used to vary voltage to get desired output Senior Design :: May 04-08

Variable Buck Converter The new design Fixed Buck Converter TL499ACD Variable Outputs 120 VAC Wall outlet 48VDC 25VDC High Freq. Switch Variable Buck Converter Power Supply Senior Design :: May 04-08

End Product Options Low cost system Useful to senior design teams Client wants for power supply Low cost system Useful to senior design teams Portable Power Supply # of +/- terminals # of + terminals Meters Option #1 1 Ammeter Voltmeter Option #2 2 Option #3 Senior Design :: May 04-08

Commercial Power Supply Astrodyne ® Power Supply Regulated Output 85-265 VAC input Overload Voltage protection Short Circuit Protection EMI Filter Senior Design :: May 04-08

Fixed Buck Converter Switch components Motorola SG3527A Pulse Width Modulator Control Circuit Fixed duty ratio, 44 VDC to 25 VDC Sends square wave to MOSFET DRIVER Maxim MA4428 Dual High-speed 1.5A MOSFET Driver Drivers both a N-channel and P-channel MOSFET to achieve the desired switching speed

Texas Instruments TL499A circuit Wide-Range Power-Supply Controllers R1, R2, R3 create a comparison voltage Voltage varied by changing potentiometer Minimum output voltage is 2.5 volts. Maximum output voltage is 24 volts

Digital Display Maxim ICL7107 3 1/2 Digit A/D Converter Connected across the output Displays output voltage to 1/10 accuracy 2 double digit 7 segment LED displays

Future Work Recommendations A phase to finalize the project Necessary future work Negative voltages Voltage regulation Circuit protection Other future work Variable current Voltage zero at start up Auto zeroing voltmeter Senior Design :: May 04-08

Financial Comparison Agilent 3631a triple output power supply 80 watts + 25 V at 1 A +6 V at 6 A $ 1200 Proam universal ac-dc adaptor 9 watts + 1.5, 3, 4.5, 6, 7.5, 9, 12 V at .5 A $ 9.00 Our design now 24 watts 2.5 to 24 V at 1 A $ 120 ~ 20-30 seconds Senior Design :: May 04-08

Personal Time Commitment Paper work Research Design Construction Total Darrel Long 25 41 42 24 134 Fares Karadsheh 20 48 47 14 131 Trung Nguyen 22 43 132 Benjamin Voetberg 51 45 137 90 184 195 65 534 Slide time ~20-30 seconds Senior Design :: May 04-08

First Semester Schedule Senior Design :: May 04-08

Second Semester Schedule Senior Design :: May 04-08

Project Evaluation Identify possible designs to implement, completed and choose one Design hardware completed Hardware specifications completed Circuit simulations completed Test hardware almost complete Documentation completed Senior Design :: May 04-08

Lessons Learned What went well What didn’t go well Communication Within the team With company representatives Teamwork What didn’t go well Unspecific project, time constraint for meeting with clients Simulation of the circuit Hardware implementation Technical knowledge gained Simulation experienced gained Power electronics knowledge Senior Design :: May 04-08

Risk and Risk Management Anticipated risks Team scheduling Loss of team member, advisor, or clients Unanticipated risks Simulation complications Hardware implementation Unable to use certain designs because of cost Senior Design :: May 04-08

Closing Summary Variable dc output of 2.5 to 24 volts Meets client specifics Provides extra voltage values Digital voltmeter Accurately provides output voltage Design is a solid base to further expand Negative voltages Circuit protection Voltage regulation Senior Design :: May 04-08

Questions? Senior Design :: May 04-08