DrexelUniversity
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.
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 DesignCenter - 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.
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:
• IntroductionIntroduce the reader to the project goals. Consider your reader to be another ECE junior who has not yet taken this course.
• Circuit DesignDiscuss 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
• DiscussionProve 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.
• ConclusionsExplain 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.
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
BlockQtyComponentDescription
Rectifier
4diode1N4007
Filter
1capacitor1000 µF, electrolytic
Pre-Regulator
1zener diodesee list
1transistor2N3906, PNP, 350 mW
Regulator
1transistor2N3904, NPN, 350 mW
1zener diodesee list
1darlingtonTIP120, NPN, Ic(max)= 3 A, Vceo = 60 V, PD = 65 W
Zener diodes
1N4728, 3.3 V, 1W
1N4734A, 5.6 V, 1W
1N4736A, 6.8 V, 1W
1