I helped translate output, ripple, load, tolerance, and component-rating requirements into a rectifier, filter, and Zener-regulator circuit that could be simulated, prototyped, and measured.
For EEET-213, my team designed a linear power supply around a supplied 120 VAC-to-12.6 VAC transformer. The required output was +6.2 VDC within ±10% from no load to 60 mA, with no more than 50 mV peak-to-peak ripple and a green LED power indicator. We used calculations and datasheets to select components, evaluated the design across input and load variations in Multisim, and then built and tested the circuit in the lab.
Technical details
How the system works.
A closer look at the architecture, implementation decisions, and validation behind this project.
01
Turning specifications into a circuit
The assignment defined both normal operation and boundary conditions. The AC input could vary from 110 to 130 VAC at 60 Hz, while the DC output had to remain within the 6.2 V ±10% window as the load changed from 0 to 60 mA. Ripple at the output could not exceed 50 mV peak to peak.
I approached the design as four connected stages: the non-center-tapped step-down transformer, silicon rectifier, smoothing filter, and Zener regulator. Treating the stages separately made it possible to calculate the voltage and current available to the next stage, then verify the entire supply as one system.
02
Component selection and derating
The available parts included 1N4004 rectifier diodes, a 1N4735A 6.2 V Zener diode, 5% half-watt resistors, stocked capacitors, and a green LED. Component values were selected from the required output and load range rather than copied from a fixed schematic.
The design review extended beyond nominal values. I checked rectifier-diode peak inverse voltage and forward current, the filter capacitor's maximum voltage, resistor power dissipation, and the Zener and LED current or power limits. These checks established operating margin under both nominal and worst-case input and load conditions.
Rectifier diodes: forward current and peak inverse voltage
Filter capacitor: voltage rating and ripple performance
Resistors: worst-case power dissipation
Zener diode and LED: current and power limits
03
Multisim verification
Before prototyping, we created a detailed schematic and parts list and simulated the complete supply in Multisim. One required troubleshooting step was correcting Multisim's 1N4735 model: the library component was configured for 5.1 V even though the physical 1N4735A and its datasheet specify a 6.2 V Zener voltage.
We varied the source across the 110-to-130 VAC input range and evaluated the output over the full load range. The simulation was used to check DC output, ripple, and component stress at nominal and worst-case conditions rather than validating a single operating point.
04
Prototype and measurement
After the simulation met the design targets, we assembled the supply using the available laboratory components. I used the oscilloscope to document output voltage and ripple at the minimum- and maximum-load conditions, selecting the appropriate coupling and measurement settings for each reading.
A digital multimeter supported the component-level checks, including voltage, current, and power calculations. We also verified that the green LED indicator operated as intended and that its current-limiting network stayed within the expected range.
05
Theory, simulation, and hardware
The final analysis compared theoretical values, Multisim results, and measured data for the rectifier diodes, filter capacitor, Zener network, indicator circuit, output voltage, and ripple. Percent-error calculations made differences visible instead of treating the simulation as an exact prediction.
We investigated discrepancies by considering real diode behavior, component tolerances, transformer and source characteristics, loading, and measurement setup. That comparison was the central engineering result: a design is not complete when the schematic works at one nominal point; it must remain within specification across its operating range and be supported by documented measurements.
Engineering approach
From idea to working system.
01
Define the operating envelope
We converted the input range, output tolerance, load range, ripple limit, and indicator requirement into measurable design targets.
02
Select and rate components
We calculated component values, consulted datasheets, and checked electrical stress with practical derating margins.
03
Simulate worst cases
We corrected the Zener model and swept source and load conditions to verify voltage, ripple, and component limits in Multisim.
04
Build and measure
We prototyped the supply, documented oscilloscope and multimeter readings, and confirmed operation at the load extremes.
05
Reconcile the results
We compared theory, simulation, and experimental data, calculated error, and explained meaningful discrepancies.
Technical highlights
What this project demonstrates.
01
+6.2 VDC output target with ±10% tolerance
02
0–60 mA operating load range
03
50 mVpp maximum output ripple
04
110–130 VAC input-range simulation
05
Worst-case component derating checks
06
Theory-to-simulation-to-hardware comparison
What I learned
This project taught me to treat specifications, component ratings, simulation, and laboratory measurements as one continuous design process. The most useful result was learning to defend a circuit with worst-case analysis and measured evidence—not just a nominal schematic.