Electrical Engineering Design Project: Variable Power Supply

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Date
DESIGNING A
PRODUCT THAT
MEETS
CUSTOMER’S
REQUIREMENTS
0V ~ 12V Variable Power Supply
Student Name

Contents
Introduction................................................................................................................................3
LO1 Plan a design solution and prepare an engineering design specification in response to a
stakeholder’s design brief and requirements..............................................................................4
a. Produce a design specification from a given design brief..................................................4
b. Explain the influence of the stakeholder’s design brief and requirements in the
preparation of the design specification..................................................................................4
c. Produce a design project schedule with a graphical illustration of the planned activities. 5
d. Evaluate potential planning techniques, presenting a case for the method chosen............5
e. Demonstrate critical path analysis techniques in design project scheduling/planning and
explain its use.........................................................................................................................6
f. Compare and contrast the completed design specification against the relevant industry
standard specification.............................................................................................................8
LO2 Formulate possible technical solutions to address the student-prepared design
specification specifications........................................................................................................9
a. Explore industry’s standard evaluation and analytical tools in formulating possible
technical solutions..................................................................................................................9
b. Use appropriate design techniques to produce a possible design solution.........................9
c. Apply the principles of modelling/ simulation/prototyping, using appropriate software,
to develop appropriate design solutions...............................................................................11
d. Evaluate potential technical solutions, presenting a case for the final choice of solution.
..............................................................................................................................................12
LO3 Prepare an industry-standard engineering technical design report..................................13
a. Prepare an industry-standard engineering technical design.............................................13
b. Assess the presented technical design and identify any potential limitation it may have.
..............................................................................................................................................13
c. Explain the role of design specifications and standards in producing a finished product13
d. Identify any compliance, safety and risk management issues present in the chosen
solution.................................................................................................................................14
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e. Evaluate the effectiveness of the presented industry standard engineering technical
design report for producing a fully compliant finished product..........................................14
LO4 Present to an audience a design solution based on the design report and evaluate the
solution/presentation................................................................................................................16
a. Present the recommended design solution to the identified audience..............................16
b. Explain possible communication strategies and presentation methods that could be used
to inform the stakeholders of the recommended solution....................................................17
c. Reflect on effectiveness of communication strategy in presenting the solution..............17
d. Justify potential improvements to the presented design solution, based on reflection
and/or feedback obtained from the presentation..................................................................18
d. Justify potential improvements to the presented design solution, based on reflection
and/or feedback obtained from the presentation..................................................................19
Conclusion................................................................................................................................20
Appendix..................................................................................................................................21
References................................................................................................................................23
List of Figures
Figure 1 Importance of power supply module requirements.....................................................4
Figure 2 Block diagram of variable power supply.....................................................................6
Figure 3 Gantt chart of project scheduling.................................................................................7
Figure 4 Critical path analysis of project scheduling.................................................................7
Figure 5 Design solution 1 schematic......................................................................................10
Figure 6 Design solution 2 schematic......................................................................................10
Figure 7 Evaluation of design solutions...................................................................................11
Figure 8 Role of design specification in finished product.......................................................14
Figure 9 Presentation of selected design..................................................................................17
Figure 10 Evaluation of presentation strategy.........................................................................18
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Introduction
Bench power supplies are lab grade instruments use for bench testing of different circuit.
These power supplies convert AC voltage to DC voltage, and there are various variants of
bench power supplies available in market. This report discusses different design process of
making a bench power supply. We develop this power supply according to client’s
requirements, and client requires a 0V~12V variable power supply for bench testing. We
acquire design requirements from design brief provided from project manager. We structure
this report according to desired standard. Additionally, we try to comply with industry
standard for developing power supply.
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LO1 Plan a design solution and prepare an engineering design specification
in response to a stakeholder’s design brief and requirements.
a. Produce a design specification from a given design brief.
We are assigned with project of designing a bench power supply for client. Client requires a
bench power supply of 0V~12V variable power supply, which convert AC voltage to DC
voltage. Client requires a power supply which has very output ripple voltage, desired constant
DC voltage output and use of regulator IC’s/Transistor/Zener diode for regulated output
voltage (Huang, 2017).
b. Explain the influence of the stakeholder’s design brief and requirements in the
preparation of the design specification
Keeping in view specifications of power supply, we identify that how important is a
particular component for design process. We conclude from design brief that power supply
module is most important component of power supply unit. In design brief, we provided with
some of the important requirement for power supply module. So, we identifying which
requirement of power supply module is important for design. We assign importance weight
on a scale of 1% to 100%, where 1% being lowest importance and 100% being highest
importance. For that purpose, we choose a pie chart graph (figure 1) to illustrate importance
of requirement for power supply module (Li, 2018).
40%
25%
20%
15%
Voltage Regulators Low Ripples in Voltage Voltage Output Power Supply Type
Figure 1 Importance of power supply module requirements
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To understand the importance of requirements for power supply module, we assign
importance weightage out of 100%. For instance, voltage regulators have 40% of importance
power supply module design. That’s how we assign importance weightage to requirements.
Next, we define some parameters, which will be used for evaluation of design solutions. We
evaluate design on the basis of configuration of components and their assembling.
Additionally, evaluate on the basis of how long unit will last, mobility of unit and cost
effectiveness.
c. Produce a design project schedule with a graphical illustration of the planned
activities.
We conclude some of the design requirements from design brief but for a better
understanding of requirements, we meet a client. In this meeting, we discuss requirements
and how much they important to client. After meeting, we conclude following design
requirement for power supply unit design (Guida, 2019).
 0V ~ 12V variable power supply for bench testing
 Power supply module:
o Input voltage 110V AC ~ 230V AC
o Output voltage 0V DC ~ 12V DC
o Output current 0A ~ 3A
o Expected ripples in voltage ≤ 3mV r.m.s
o Expected output power 40W
o Use of regulator IC’s or Zener diode
o Expected line and load regulation is ±0.5%
o Expected efficiency of module is ~80%
o Use of potentiometer to regulate voltage to desired level
 Other unit design specifications are LED indicator, one fan, heat sink, an input
terminal, and enclosure box for power supply unit.
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d. Evaluate potential planning techniques, presenting a case for the method
chosen.
1.1 Design process of power supply
To design a variable power supply following steps are considered for design:
 Transformer to lower the high AC voltage
 Bridge rectification to convert AC voltage to DC voltage
 Capacitors use to lower the gained DC voltage output after rectification
 Regulators regulate the DC voltage to desired level
 Smoothing is processed to reduced ripples in output DC voltage
 Potentiometer use to divide voltage and make sure of variable voltage
1.2 Design process block diagram
Considering design process discussed in previous section, figure 2 illustrates a block diagram
of power supply (Mutambara, 2017).
Figure 2 Block diagram of variable power supply
e. Demonstrate critical path analysis techniques in design project
scheduling/planning and explain its use.
In this section, we elaborate on how design process will be scheduled. How much time
required to complete a scheduled task? For that purpose, we have prepared a Gantt chart to
schedule our tasks. According to our schedule, our first most task is to meet with client and
develop a better understanding of requirements. After developing a design specification from
meeting, we conduct research analysis to find out how our project can meet standards of
industry. Then we start preparing technical design solution for project design and analyze
them. In analysis phase, we evaluate these designs on the basis of predefined parameters and
select a final design for project. After that, we will develop a design prototype and send it for
feedback. If there is improvement suggestion in feedback than we will update model. In the
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end, a final presentation will be conducted present designed power supply to client and get
his feedback and improvements suggestions for design (Diemert, 2018).
Figure 3 Gantt chart of project scheduling
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Figure 4 Critical path analysis of project scheduling
f. Compare and contrast the completed design specification against the relevant
industry standard specification.
We compare our considered design with other available products in market. This comparison
is shown in table 1.
Table 1 Comparison of considered with other products
Products→
Specifications↓
Design in
Consideration
MeanWell
PS-35-12
UniSource
PS1230
MeanWell
HRP-75-12
Input Voltage 110V AC ~
230V AC
90V AC ~
264V AC
120V AC ~
250V AC
90V AC ~
260V AC
Output
Voltage
0V DC ~ 12V
DC
0V DC ~ 12V
DC
0V DC ~ 12V
DC
0V DC ~ 12V
DC
Output
Current
0A ~ 3A 0A ~ 3A 3A 0A ~ 6A
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Ripple in
Voltage
≤ 3mV r.m.s 4 mV r.m.s ≤5mV r.m.s 4 mV r.m.s
Power Output ~ 40W 36W 60W 75W
Line & Load
Regulation
±0.5% ±0.5% ±5% ±0.3%, ±0.5%
Efficiency ~80% 81% >72% 87%
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LO2 Formulate possible technical solutions to address the student-
prepared design specification specifications.
a. Explore industry’s standard evaluation and analytical tools in formulating
possible technical solutions.
Before designing a possible technical design solution, we are devising a common
methodology for design. Our main focus is power supply module because of module most
important component of power supply unit. To gain a variable output voltage of 0V ~ 12V,
we need a suitable transformer to step down to lower the high AC voltage. Then voltage
passes through Rectifier Bridge to convert it into DC voltage. This gained output voltage pass
through a series of different type capacitors to further lower the output voltage. After this, it
passes through regulator to bring voltage to desired level. As we need 0V ~ 12V output, so
there is a need for a suitable potentiometer to bring minimum voltage to 0V. This output
voltage passes through some extra capacitors or diodes to further smooth out voltage
(Ratwani, 2015).
b. Use appropriate design techniques to produce a possible design solution.
We conduct research on desired specifications to find out suitable components for designing
of module. After that, we develop mock designs for modules and from which three design to
develop module. This develop module will evaluate on predefined parameters and a final
design selected to compliance project design (Zahabi, 2015).
1.1 Design solution 1
Design solution 1 uses a 12V step-down transformer to lower the high input AC voltage. This
reduced voltage passes through 10A bridge rectifier to convert AC voltage to DC voltage.
The gained DC voltage passes through electrolytic capacitor of 3300μF/35V to reduce DC
voltage. For voltage regulation, we use LM350 regulator whose minimum output is 1.25V to
maximum 13.5V. To gain an output of 0V, we put two diodes of 1N5402 (100V/3A) in series
to get a voltage drop to 0V. Also, we general purpose two diodes of 1N4001 (100V/1A) to
protect regulator from reverse current flow in case of a shutdown. A potentiometer of 1k is
used to have a variable output. Design solution 1 has very low output voltage but high
voltage of current flow. So, due this it may give an electric shock to user.
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Figure 5 Design solution 1 schematic
1.2 Design solution 2
In design solution, we use a step-down transformer of 25V-0-25V/5A to reduced high AC
voltage to low voltage. Then using full wave rectifications, bridge rectifier converts AC
voltage to DC voltage. This gained DC voltage filtered using a capacitor of 2200μF/50V.
Filtered voltage fed to LM338 regulator whose has a minimum output of 1.2V and maximum
of 32V. The regulated voltage passes through two tantalum capacitors of 1μF/50V and
10μF/50V respectively to bypass any unwanted residual current and to enhance ripple
rejections. Two diodes placed around LM338 to avoid damage in case reverse current surge.
Additionally, two potentiometers are used to acquire a wide range of output voltage. During
experiment we observe that diode are not able to handle discharge surge of capacitors. Hence
result in damaging the regulator.
Figure 6 Design solution 2 schematic
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