Engineering Design Project: A 12V Fixed Dual Power Supply for Lab Use

Desklib provides past papers and solved assignments for students. This project details the design of a 12V fixed dual power supply.

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Designing a Product that Meets Customer’s Requirements
12V Fixed Dual Power Supply
DESIGNING A
PRODUCT THAT
MEETS
CUSTOMER’S
REQUIREMENTS
3/22/2019
ABSTRACT
This document presents the design of a ±12V
fixed dual power supply to be used on test bench
for testing Op Amp Circuits in lab.
March 22, 2019

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Designing a Product that Meets Customer’s Requirements
Table of Contents
1 Stakeholder’s Needs Assessment..........................................................................................5
1.1 User’s Design Requirements.............................................................................................5
1.2 Prioritization of User’s Requirements...............................................................................5
1.3 Target Specifications According to User’s Requirements................................................5
1.4 Power Supply Design Process...........................................................................................6
1.4.1 Block Diagram...........................................................................................................6
1.4.2 Design Flow Chart.....................................................................................................7
1.4.3 Design Schedule........................................................................................................7
1.4.4 Critical Path Analysis................................................................................................8
1.5 Benchmarking...................................................................................................................8
2 Possible Technical Solutions.................................................................................................9
2.1 Concepts Generation.........................................................................................................9
2.1.1 CPT1..........................................................................................................................9
2.1.2 CPT2..........................................................................................................................9
2.2 Concepts Evaluation.......................................................................................................10
2.3 Concept Selection...........................................................................................................10
2.4 Software and Hardware Standards to Make Design Choices.........................................11
2.5 Design Improvement Scope............................................................................................11
3 Industry Standard Technical Design.................................................................................12
3.1 Final Concept Elements..................................................................................................12
3.2 Concluding Design Curbs...............................................................................................12
3.3 Roles of Specifications....................................................................................................13
3.4 Compliance, Risk, and Safety Management...................................................................13
3.5 Effectiveness Leading to Full Compliance.....................................................................13
12V Fixed Dual Power Supply March 22, 2019

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Designing a Product that Meets Customer’s Requirements
4 Design Presentation.............................................................................................................15
4.1 Customer Feedback.........................................................................................................15
4.2 Design Improvements in Response to Feedback............................................................16
5 Conclusion............................................................................................................................16
6 References.............................................................................................................................17
Appendix 1: Power Supply Schematics.....................................................................................18
Appendix 2: PCB Layout............................................................................................................19
Appendix 3: Case Design (3D Model)........................................................................................20
Appendix 4: Power Supply 3D View..........................................................................................21
12V Fixed Dual Power Supply March 22, 2019

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Designing a Product that Meets Customer’s Requirements
List of Figures
Figure 1: Block Diagram.................................................................................................................6
Figure 2: Design Process.................................................................................................................7
Figure 3: (left) CPT1 (right) CPT2..............................................................................................10
Figure 4: FMEA Two-Path Model................................................................................................11
Figure 5: Design Improvement......................................................................................................11
Figure 6: Design Elements.............................................................................................................12
Figure 7: Specs Role in the Design Process..................................................................................13
Figure 8: Compliance Safety Risk Management Issues Handling Diagram.................................13
Figure 9: Line Regulation (Vin vs Vout )......................................................................................14
Figure 10: Load Regulation (Vout vs Iout)...................................................................................14
Figure 11: Design Presentation......................................................................................................15
List of Tables
Table 1: User Requirements............................................................................................................5
Table 2: Prioritization of User Requirements..................................................................................5
Table 3: Specifications....................................................................................................................5
Table 4: Benchmarking Data...........................................................................................................8
Table 5: Evaluation of Concepts....................................................................................................10
Table 6: Software and Hardware Choices.....................................................................................11
Table 7: Efficiency Comparison....................................................................................................15
Table 8: Effectiveness Comparison...............................................................................................15
Table 9: Did you find out the product you looked for?.................................................................15
Table 10: Did the staff satisfy your questions on the product?.....................................................16
Table 11: Are you satisfied with the product performance and aesthetics according to the product
requirement?..................................................................................................................................16
12V Fixed Dual Power Supply March 22, 2019

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Designing a Product that Meets Customer’s Requirements
1 Stakeholder’s Needs Assessment
1.1 User’s Design Requirements
Table 1: User Requirements
Power Supply Category Fixed, Dual
Output Voltage ±12V, Constant Output Voltage
Ripple Very Low Output Ripple Voltage
Regulation Zener or IC Regulators
Function Regulated Power Supply For Testing Op-Amp Circuits in Lab
1.2 Prioritization of User’s Requirements
 Importance Scale: 1-50
 Features Rank: 1-10
Table 2: Prioritization of User Requirements
Customer’s
Requirements
Importance Portable User-Friendly Durable Flexible
Very Low Ripple in
Output Voltage
86 4 5 3 9
IC Regulators 72 5 6 3 8
Zener Regulators 22 3 4 4 7
Fixed, Dual Output 55 6 5 5 8
Raw Score 1,100 1,225 837 1,944
Prioritization
Ranks
3 2 4 1
1.3 Target Specifications According to User’s Requirements
Table 3: Specifications
Input Voltage 240VAC
Output Voltage ±12VDC, Fixed
Output Current 350mA
Power Rating 4.2W
Weight 6 kg
Dimensions 5 ₓ 9 ₓ 12 in
12V Fixed Dual Power Supply March 22, 2019

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Designing a Product that Meets Customer’s Requirements
Ripple ≤ 4mVrms
Ambient Temperature 0-50℃
Earth Connection Yes
Dual Output LED Indication Yes
Board Connections Screw Terminal
Connectors
1.4 Power Supply Design Process
There are four main steps to gain dual constant output DC voltages.
I. The transformer steps down voltages from AC high voltage mains to a desired low AC
voltage level.
II. The rectifier converts AC to DC output, however, this DC output is pulsating with
significant ripple voltages.
III. Smoothing Capacitors even out the pulsating output obtained from the rectifier.
IV. Regulator eliminates ripple in rectifier’s output voltages and hence gives a constant fixed
voltage (Wang et al, 2016).
1.4.1 Block Diagram
Considering the above design elements into account, user’s requirement of fixed and regulated
output will be obtained through the following steps shown in the diagram below;
Figure 1: Block Diagram
12V Fixed Dual Power Supply March 22, 2019

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Designing a Product that Meets Customer’s Requirements
1.4.2 Design Flow Chart
Figure 2: Design Process
1.4.3 Design Schedule
ID Task Name Duration Start
1 Initial Meeting with Stakeholders 1 day Mon
3/25/19
2 Requirements 1 day Tue 3/26/19
3 Design Analysis 2 days Tue 3/26/19
4 Conceptual Design Generation 1 day Thu 3/28/19
5 Final Design Considerations 1 day Fri 3/29/19
6 Modeling and Prototyping 4 days Fri 3/29/19
7 Testing and Feedback 5 days Tue 4/2/19
8 Final meeting and product
presentation
3 days Tue 4/9/19
W T F S S M T W T F S S M T W T F S S M T W T F
Mar 17, '19 Mar 24, '19 Mar 31, '19 Apr 7, '19
12V Fixed Dual Power Supply March 22, 2019

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Designing a Product that Meets Customer’s Requirements
1.4.4 Critical Path Analysis
Requirements
Start: 3/26/19 ID: 2
Finish: 3/26/19 Dur: 1 day
Res:
Design Analysis
Start: 3/26/19 ID: 3
Finish: 3/27/19 Dur: 2 days
Res:
Conceptual Design Generation
Start: 3/28/19 ID: 4
Finish: 3/28/19 Dur: 1 day
Res:
Final Design Considerations
Start: 3/29/19 ID: 5
Finish: 3/29/19 Dur: 1 day
Res:
Modeling and Prototyping
Start: 3/29/19 ID: 6
Finish: 4/3/19 Dur: 4 days
Res:
Testing and Feedback
Start: 4/2/19 ID: 7
Finish: 4/8/19 Dur: 5 days
Res:
Final meeting and product presentation
Start: 4/9/19 ID: 8
Finish: 4/11/19 Dur: 3 days
Res:
Initial Meeting with Stakeholders
Start: 3/25/19 ID: 1
Finish: 3/25/19 Dur: 1 day
Res:
1.5 Benchmarking
The final specifications of our product in contrast to the industrially available similar products
can be seen in the table below;
Table 4: Benchmarking Data
Specifications Product Under
Consideration
– Fixed Dual
Power Supply
Cebek FE-9
(CFE009)
Symmetrical
Power
Supply
Cebek FE-21
(CFE021)
Symmetrical
Power Supply
Cebek FE-160
(CFE160)
Symmetrical
Power Supply
Cebek FE-170
(CFE170)
Symmetrical
Power Supply
Input Voltage 230 ~ 240 VAC 230 ~ 240
VAC
230 ~ 240 VAC 230 ~ 240 VAC 230 ~ 240 VAC
Output Voltage ±12VDC ±12VDC ±12VDC ±12VDC ±12VDC
Output Current 350mA 500mA 800mA 270mA 600mA
Ripple 4mV max 10mV max 10mV max 5mV max 5mV max
Module
Dimensions
96x50x30 mm 93x56x25
mm
93x56x25 mm 107x87.5x35 mm 107x87.5x43 mm
Earth Connection
for Chassis Ground
Yes No No No No
Dual Output LED
Indication
Yes Yes Yes Yes Yes
Screw Terminal
Connectors
Yes Yes Yes Yes Yes
12V Fixed Dual Power Supply March 22, 2019

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Designing a Product that Meets Customer’s Requirements
2 Possible Technical Solutions
2.1 Concepts Generation
Initially, 18 concepts were generated out of we were able to focus on 3 main concepts that can be
useful regarding our final design. Each of them is discussed below;
2.1.1 CPT1
The first prototype we developed, was transformerless capacitive power supply giving dual 12V
output. Three capacitors in parallel were used to drop down the voltage level from 230VAC to
24VAC. Bridge rectifier of 1N4007 x 4 diodes was used for rectification giving an output of
24VDC. Smoothing capacitor was mounted to smooth out the ripple output of the rectifier. A
Zener diode 15V/1W was used for regulation fixing the output voltage from 24VDC to 12VDC.
We used LED for output indication. Limiting resistor R3 is most important without which Zener
diode would have been destroyed. After testing this prototype, we realize that this type of power
supply can be destroyed if the power supply section fails because it doesn’t have any galvanic
isolation from mains nor any earth chassis. The regulation was so weak that when the power
supply voltages changed, the output became unstable. Moreover, it is useful only for applications
operating under 100mA current so it is not recommended for heavy current inductive loads. The
circuit schematic is shown in the most left of figure3.
2.1.2 CPT2
In this design, we used a transformer which is 18-0-18V - 1A and steps down 110VAC~220VAC
to 18VAC. C3 and C4 are ceramic capacitors 100nF/50V each. C1, C2 are 2200μF/35V each,
and C5, C6 are 220μF/35V each. C1, C2, C3, C4 filter and stabilize the output of bridge rectifier
which is 100V/1A rectifier. Separate diodes are not used to make a bridge rectifier. C5, C6
stabilize the output of the voltage regulator and reduce the remaining ripple voltages. The circuit
schematics are shown in the right of figure3. When we tested this prototype, our team came up
with some improvements to be done. The output was not smooth enough regarding customer’s
requirement of very low ripple voltage. There should be an earthed chassis to provide a
transformer with protection from high incoming voltages. The output should have been indicated
through LEDs for professional product design. Ripple voltages must be reduced to a lower level
and for this capacitor values must be changed. The output current is relatively high while we
want to make a supply which can test the op-amp circuits. So the transformer must also be
replaced with some low-level current ratings. Moreover, regulator produces a substantial loss if
12V Fixed Dual Power Supply March 22, 2019

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Designing a Product that Meets Customer’s Requirements
there is a large difference between its input and output and most of the loss occurs in the form of
heat when even the large heat sinks cannot make enough contribution to saving the regulator
from being destroyed (Ma et al, 2015).
Figure 3: (left) CPT1 (right) CPT2
2.2 Concepts Evaluation
Above-mentioned tested concepts are being evaluated keeping in view of the final design
requirements. Each parameter is given a rating “+” if its performance is better than a reference
parameter. However, if the parameter’s performance is not good as compare to the reference
design requirement, it is given a rating as “-“.
Table 5: Evaluation of Concepts
Parameters CPT1 CPT2
Longevity - +
Safety - +
Affordable + -
Reconfigurable - +
Easy to Scheme + +
Constant Output - +
Smoothing - +
Voltage Stabilization - -
Regulation - -
Protection from Electric Shock - -
2.3 Concept Selection
Recently, we compared two conceptual designs with the reference design parameters and ranked
them according to their importance. Then the final concept is being selected through comparing
both CPT1’s and CPT2’s most significant and least significant factors. For this, we prepared a
high-level FMEA two-path model shown below.
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Designing a Product that Meets Customer’s Requirements
Figure 4: FMEA Two-Path Model
Keeping in view of this diagram CPT2 is more useful for final design considerations after some
improvements mentioned above.
2.4 Software and Hardware Standards to Make Design Choices
Table 6: Software and Hardware Choices
Software Circuit Schematics Electronics Lab
Hardware Case Design AutoCAD
PCB Design Electronics Lab
2.5 Design Improvement Scope
Figure 5: Design Improvement
12V Fixed Dual Power Supply
Proper Functioning Areas
Regulators are working fine
Bridge Rectifier choice doesn't need any
improvement
Transformer choice is also good in terms of
providing more durability to power supply
Areas to be Improved
Earth Chassis must be provided in order to
provide protection against high main voltages.
Heat Sink must surround the regulators to keep
them cool against highly warm environment
March 22, 2019

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Designing a Product that Meets Customer’s Requirements
3 Industry Standard Technical Design
3.1 Final Concept Elements
After conceptual modelling, screening, and evaluation, we came up to conclude the following
elements as final design components;
Figure 6: Design Elements
 For a fully integrated circuit schematics and 3D view, see the appendix of this report.
3.2 Concluding Design Curbs
Linear voltage regulator regulates the input voltage behaving as a variable resistance between
input and output and hence provides a precise output voltage. But it has low efficiency ~ 45%,
and also large heat sink is required while still, the chances of heating up are there. If the power
supply is being built for high current applications, cost and efficiency will still be the main
limitations (Sen et al, 2016).
12V Fixed Dual Power Supply March 22, 2019