Transcript Slide 1

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
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Benjamin Voetberg, EE
Fares Karadsheh, EE
Trung Nguyen, EE
Darrell Long, EE
Senior Design :: May 04-08
Overview
 Project objectives & guidelines
 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
Sample from the
simulation
 For the simulation, 2 choice:
 Pspice: Available and have a lot of
parts
 Electronic Work Bench : Easy and
more visual
Electronic Work Bench was
used to simulate the design
Senior Design :: May 04-08
Design Approach Buck Converter
 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
Simple ac/dc conversion
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
The new design
120 VAC
48VDC
Fixed Buck
Converter
High Freq.
Switch
Wall outlet
Power Supply
TL499ACD
25VDC
Variable
Outputs
Variable Buck
Converter
Senior Design :: May 04-08
End Product Options
 Client wants for power
# of +/terminals
supply
 Low cost system
Useful to senior
design teams
 Portable Power
Supply
# of +
terminals
Meters
Option #1
1
1
Ammeter
Voltmeter
Option #2
1
2
Ammeter
Voltmeter
Option #3
2
2
Ammeter
Voltmeter
Senior Design :: May 04-08
Commercial Power Supply
 Astrodyne ® Power Supply
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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
Senior Design :: May 04-08
Personal Time Commitment
Paper
work
Research
Design Construction Total
Darrel Long
Fares
Karadsheh
Trung
Nguyen
Benjamin
Voetberg
25
20
41
48
42
47
24
14
134
131
22
41
43
24
132
25
51
45
14
137
Total
90
184
195
65
534
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
 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