Drexel University
ECE-E352 Analog Electronics
Project I: DC Power Supply
DC Power Supply
In this project you will construct and analyze a DC power supply. An example circuit is
given in Figure 1. You may implement an alternate circuit with the permission of the instructors.
All component types in the example circuit are available in PSpice libraries for simulation.
I. Performance Specifications:
Your circuit must meet the following specifications:
Output Voltage: 9, 10, 11 or 12 Volts (select one), accurate to ±50 mV
Output Power ≥ 1.0 Watt
Output Ripple ≤ 50 mV (peak to peak)
Load Regulation * ≤ 0.2%.
Line Regulation ** ≤ 50 mV/V
No capacitors larger than 1.0 mF (1000 µF)
* Load regulation is defined as (unloaded voltage – loaded voltage)/(unloaded voltage).
Loaded voltage will be tested at 1 Watt output.
** Line regulation will be tested by varying the AC input by 10% and measuring the change of
the dc output voltage. It is calculated as (output voltage – varied voltage)/(output voltage).
II. Tasks
Simulation
1. Your output voltage level will be assigned in lab. Determine the component differences
between your circuit and the example circuit. The provided transformer will provide either
20Vpp or 40Vpp depending on your configuration. A list of active components available is
on the last page. You are free to use other components, but you must purchase them
yourselves. Resistors are available in the lab.
2. Simulate your power supply in Microsim PSpice. Drive your circuit with an ac source(Vsin)
having a frequency of 60 Hz and an amplitude which matches your transformer design.
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Drexel University
ECE-E352 Analog Electronics
Project I: DC Power Supply
3. Use Microsim Probe to verify the critical voltages and currents in your circuit. Compare the
voltages and currents observed to the limits of the components (PIV for diodes, reverse
currents for Zener diodes, etc.) to be sure you are in safe operating regions. You might want
to try your hand at creating performance functions - regulation vs. load resistance, for
example (see p. 334, The Design Center - Analysis - Reference Manual, in room 7-405).
Figure 1. Regulated Linear DC Power Supply
Hint: Simulate your circuit block by block: rectifier, filtered rectifier, pre-regulator, etc. This
will aid your understanding of the circuit and help debug problems later.
4. Determine the simulated output voltage regulation for several load resistances.
Fabrication
0. Obtain characteristic curves for each of the active devices you actually use. Determine the beta
of the transistors and the Vz of the zener diodes. If possible use this information to improve the
accuracy of your Spice models.
1. Construct your circuit on a breadboard. Assemble your circuit carefully - you will only be
given one set of parts. Again, work block by block. This is easier that trying to debug the
entire circuit.
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Drexel University
ECE-E352 Analog Electronics
Project I: DC Power Supply
2. Measure critical voltages and currents. Record these values in a lab notebook. Sketch
important waveforms. Generate hardcopies or screen captures from the HP digital scopes if
possible.
3. Present your power supply to your TA for testing. Each member of the design team must be
prepared to explain any aspect of the operation of the supply to the TA.
Report
Your lab report should have the following sections:
• Introduction
Introduce the reader to the project goals. Consider your
reader to be another ECE junior who has not yet taken
this course.
• Circuit Design
Discuss the performance goals you have chosen and all
important design decisions made. The discussion should
include the transformer, rectifier, preregulator, regulator
and
difference
amplifier
designs.
Include
sample
calculations in an Appendix.
• Simulation Results
• Experimental Results
• Discussion
Prove that your components are operating in safe regions.
Make direct comparisons between simulation predictions
and actual measurements (display simulation results and
experimental measurements on the same plot, for
example). Comment on major differences, if any.
• Conclusions
Explain whether or not you have met your design goals.
Mention what you might have changed to improve your
design.
Your report should be carefully written, with proper grammar and spelling. Make use of
well designed tables and graphs to present your design and measurement information. Each
figure and table used should have a numbered caption, and each should be referenced in the text.
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Drexel University
ECE-E352 Analog Electronics
Project I: DC Power Supply
Variations
You may construct a switching power supply. You will be on your own for this, so be sure
you have access to a good source of detailed design information before you commit to this. See
one of your instructors before you start.
Tentative Parts List
Block
Qty Component
Description
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diode
1N4007
1
capacitor
1000 µF, electrolytic
1
zener diode
see list
1
transistor
2N3906, PNP, 350 mW
1
transistor
2N3904, NPN, 350 mW
1
zener diode
see list
1
darlington
TIP120, NPN, Ic(max)= 3 A, Vceo = 60 V, PD = 65 W
Rectifier
Filter
Pre-Regulator
Regulator
Zener diodes
1N4728, 3.3 V, 1W
1N4734A, 5.6 V, 1W
1N4736A, 6.8 V, 1W
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