Download General Problem Statement

Multiple-output, Variable-output DC
Power Supply
May03-22
Team Members:
Erik Johnson
Joel Jorgensen
Peter Holm
Philip Schulz
Clients – Prof. Patterson, Prof. Lamont
Faculty Advisor – Dr. Allan Potter
April 30th, 2003
Presentation Overview
Problem statement and solutions
 Summary of activities
 Resource requirements
 Summary of progress
 Questions

General Problem Statement
Develop a power supply with the following
voltages: +1.5V,  3.0V, +3.2V, +4.5V, 
5.0V, +6.0V, +7.5V, +9.0V,  12.0V,
+15.0V, +18.0V, +24.0V
 Output 2 + voltage outputs and 2 + voltage
outputs simultaneously
 Produce for a low cost (~$150)
 Allow a maximum current of 1A through
each set of terminals

Solution Approach
Develop general design
 Simulate and test on CAD program
 Order parts
 Assemble
 Test
 Modify and re-test if necessary

Operating Environment

Standard laboratory conditions
– Indoors
– Approximately 24 degrees Celsius

Standard 120V, 60 Hz wall output
End Users and Uses

Users
– Research and design students
– Faculty

Uses
– Power and test design projects
– Produce a small current at many voltages
– Provide several voltages simultaneously
Assumptions and Limitations

Assumptions
– All four outputs will be used simultaneously
– Power supply will be used indoors at room temp
– Power supply will be powered by 120V, 60 Hz

Limitations
– Output current limited to 1A max per output
– Total cost must be below $150
– Input must be 120V at 60 Hz
End Product Description
4 selectable output voltage terminal sets
 Maximum current of 1A per output
 Output voltage selected by rotary knobs
 Digital readout of voltage, current and
wattage
 Fuses for power supply protection

End Product
Present Accomplishments
Schematic simulated and successful
 Successfully implemented transformer and
bridge rectifiers on circuit board
 Successfully implemented +/- voltages on
circuit board
 Examined methods of implementing
positive only voltages

Approaches to the Design
Recycle/modify/incorporate existing
insufficient power supplies
 Create and design an original power supply

– Use store-bought voltage converters
– Design and create voltage converters
» Flyback converter
» Buck converters
» LM317T/LM337T voltage regulators
Project Definition Activities

The power supply specs were expanded
from the original to include the following:
– +3.2V, +7.5V, +15V, and +18V
– 2 + voltage outputs and 2 + voltage outputs
– Ammeter and voltmeter
Research Activities

The need for more voltage outputs was
researched.
– It was found that the additional voltages of
+3.2V, +7.5V, +15V, and +18V would be useful
for small home electronics

Also researched various power supply
designs for ideas to implement in the final
product.
LM317T/LM337T Voltage
Regulators
Adjustable output down to +1.2v
 Adjustable current limiting feature
 Line regulation typically .01%/V
 Load regulation typically .1%
 80 dB ripple rejection

TL494 PWM Control Circuit
Up to 200 kHz oscillator frequency
 Feedback allows voltage and current
regulation

Design Activities
Different implementation schematics tested
 Because the LM317T/LM337T voltage
regulators are not in the Workbench/Pspice
libraries, the circuits were physically tested

120V TX1 24V
D1
C1
1n
V1
120V ac
0V dc
D3
R1
D2
D4
10
0
24V
1
V = +24V
2
100uH
D13
V = +12.0V
100uH
5.1u
24.00
D13
5.1u
12.37
V = +6.0V
100uH
D13
5.1u
6.09
V = +3.2V
100uH
D13
5.1u
3.22
V = +1.5V
100uH
D13
1
5.1u
V = +18V
2
100uH
D13
1.51
V = +9.0V
100uH
5.1u
18.41
D13
5.1u
9.21
V = +4.5V
100uH
D13
1
5.1u
V = +15V
2
100uH
D13
4.55
V = +7.5V
100uH
5.1u
15.43
D13
5.1u
7.64
D1
120V TX1 12.5V
D3
1
U9
IN
2
C7
C9
C1
V1
120V ac
0V dc
2200u
D2
0
0
2200u
LM337T
V reg
OUT
V = -3.0V
R9
.1u
120
0
D4
C10
1u
0
R8
C8
10u
1032
0
D7
1
U9
1
U9
IN
2
C7
0
2200u
LM317T
V reg
OUT
C7
V = +12.0V
C9
R9
C10
240
1u
D6
.1u
IN
2
0
0
2200u
C9
.1u
120
0
0
C7
0
2200u
LM317T
V reg
OUT
V = +5.0V
R9
C10
240
1u
D6
.1u
0
0
720
0
D7
IN
C7
V = +3.0V
C9
2200u
0
LM317T
V reg
OUT
R9
C10
D6
.1u
240
0
R11
C8
10u
336
0
1u
0
C9
2200u
0
LM337T
V reg
OUT
V =
-12.0V
C10
R9
.1u
120
0
R11
C8
10u
336
0
R10
2
IN
2
C7
C9
C8
10u
1
U7
360
2064
1
U7
IN
1u
0
0
D7
2
C10
R10
C8
10u
0
1
U9
V = -5.0V
R9
R8
C8
10u
LM337T
V reg
OUT
1u
0
Personnel Effort Budget
Team Members
Paper Work
Research
Design
Construction
Totals
Est.
Act.
Est
Act.
Est.
Act.
Est.
Act.
Est.
Act.
Erik Johnson
8
10
21
14
32
25
12
13
73
58
Joel Jorgensen
5
27
25
13
34
26
13
14
77
76
Peter Holm
9
25
15
7
25
22
14
8
63
58
Philip Schulz
7
10
18
8
28
27
12
12
65
53
27
72
79
42
119
100
51
47
278
265
Totals
Financial Budget
Item
Original Estimated Cost
Cost to Date
Poster
$50.00
$50.00
Case
$14.99
$0.00
Transformers
$35.53
$21.94
Resistors/capacitors/diodes
$26.80
$21.18
Cooling fan
$9.99
$8.99
Switches, dials, and terminals
$25.00
$6.21
Meters ($10.25 each)
$30.75
$0.00
Variable voltage regulator
$4.00
$3.90
$197.07
$112.22
Total
Project Schedule
Project Schedule, cont.
Project Evaluation



Done on a scale of: incomplete = 0%, to complete = 100%
Milestones:
Define problem
100%
Determine solution
100%
Design power supply
95%
Order parts and assemble
75%
Test
75%
Revise and retest if necessary
75%
Release
0%
Overall Status: Prototype
Commercialization
Estimated cost to produce: $100 - $200
 Estimated sales price: $400 - $1000
 It is anticipated that this product would have
a very large market

– Versatile
– Financially viable
Recommendations for
Additional Work
Finish original implementation
 Develop a commercial version
 Add power factor correction
 Make each set of terminals fully isolated
 Make current limitation adjustable

Lessons Learned

What worked
– Team worked well at brainstorming, designing
– Advisor was helpful when we got stuck
– Regular, scheduled meeting

What did not work
–
–
–
–
–
Collaborating on reports and poster
Weekly status reports
Ordering parts
Gaining the necessary knowledge
Advisor absence for extended period of time
Lessons Learned (cont)

Technical knowledge gained
–
–
–
–

How power supplies work
How DC-DC converters work
How transformers work
How to use Workbench
Things to do differently
– Put more time into research early on
Risks and Risk Management

Illness
– Follow good health practices
– Take on some of the sick member’s workload among
the other members

Accidents such as electrocution or fire
– Follow high voltage safety procedures when
assembling
– Cut power, use First Aid, call 911, put out fire

Losing a team member
– Be such a good team that nobody wants to leave
– Divide the work among the remaining members, seek
assistance from colleagues
Summary



Problem: Replace the current power supplies with a
single versatile tool
Approach: Consider several different alternatives by
which multiple voltages can be provided
simultaneously by a single power supply
Solution: Provide two plus/ground terminals and
two plus/minus/ground terminals whose voltage can
be set independently of the others. Also provide
meters to display the voltage, current, and wattage of
the selected set of terminals
What questions do you have?