Electrical, Computer, and Biomedical Engineering Department
CEN 304 Electronic Devices and Circuits
Course Project
INSTRUCTORS: Dr. Mohamed Jama, Dr. Yazan Dweiri, Dr. Ahmed Ali, Dr.
Abdelrahman Adam, and Eng. Jamal Alsoufi
GRADE DISTRIBUTION: Report (8%) + Demo (4%) + Project Exam (3%)
TITLE: Design of a 6-V Lead-Acid Battery Charger Using a Discrete Series Pass
Regulator with Voltage-Feedback Control
PROJECT DESCRIPTION
In this project, the students are expected to design, simulate, and implement a 6-V lead-
acid battery charger based on a discrete series pass regulator with a voltage feedback
loop. The design will employ a Zener diode to establish a stable reference, an error
amplifier transistor to compare the sampled output against this reference, and a pass
transistor operating in the linear region to regulate the charging voltage and current
delivered to the battery. Through circuit analysis, simulation, and practical
implementation, students will gain hands-on experience with linear regulator design,
operation, and testing. Performance will be evaluated under varying input voltages and
load conditions, while highlighting the role of feedback in achieving voltage
regulation.
OBJECTIVES
a) To design, simulate, and implement a 6-V lead-acid battery charger using a
discrete series pass regulator with a voltage feedback loop.
b) To evaluate the regulator’s performance under varying input voltages and load
conditions through simulations and hardware testing, measuring key parameters
such as regulation percentage, output resistance, and efficiency.
c) To provide students with practical experience in component sizing, feedback
control, and safe battery charging practices, while encouraging innovation
through optional enhancements and competition-based demonstration.
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PROCEDURE
To achieve the project’s objectives, the following stages will be undertaken:
Simulation Stage (Before Hardware Implementation)
a) Simulate the circuit in LTSpice or Multisim or any other simulation tool.
b) Perform DC Sweep Simulation by Sweeping input voltage from 10 V to 30 V
and observe regulated output.
c) Confirm correct operation of the feedback loop, error amplifier transistor, and
pass transistor before hardware build.
Component Selection and Sizing
Before hardware construction, students must justify component ratings:
Transistors: Collector current ≥ 1 A, adequate power dissipation (e.g., 𝑃𝐷 = 𝑉𝐶𝐸 𝐼𝐶 ).
Resistors: Choose based on 𝑃 = 𝐼 2 𝑅, with at least 2× safety margin (e.g., ≥10 W for
dummy load wirewound resistors).
Zener diode: Stable voltage reference (e.g., 𝑉𝑍 = 5.1 V), proper power rating.
Capacitors: Input/output filtering with adequate voltage margin.
Note: Component selection justification must be included in the project report.
Circuit Construction
Assemble the discrete series pass regulator with:
a) Zener diode reference.
b) Error amplifier BJT with Zener.
c) Power BJT pass transistor (on heatsink).
d) Voltage divider feedback network.
e) Digital voltmeter and ammeter (LED modules) to display output voltage and
current.
Circuit Testing
a) Open-Loop Test: Without battery connected, sweep input from 10 V to 30 V
using a DC supply. Record output voltage to confirm regulation.
b) Load Testing with Power Resistors: Replace the battery with 5 Ω, 10 Ω, 15 Ω,
20 Ω dummy load resistors (≥10 W).
c) Measure output voltage and current for each load.
d) Verify voltage regulation under varying load conditions.
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Performance Evaluation
Voltage Regulation Percentage:
𝑉𝑁𝐿 − 𝑉𝐹𝐿
%𝑉𝑅 = × 100
𝑉𝐹𝐿
Output Resistance:
∆𝑉𝑜
𝑅𝑜 =
∆𝐼𝑜
(measured at fixed input voltage with varying load).
Efficiency (at various input and output operating points):
𝑃𝑜
𝜂= × 100
𝑃𝑖𝑛
where
𝑃𝑜 = 𝑉𝑜 𝐼𝑜 and 𝑃𝑖𝑛 = 𝑉𝑖𝑛 𝐼𝑖𝑛
Battery Charging Test
a) After validation with simulations and dummy loads, connect the 6 V, 4.5 Ah
lead-acid battery.
b) Monitor charging voltage (~6.8–7.0 V full charge) and current in real time.
Optional Bonus Features (extra grades)
a) LED-Based Charging Status Indicator
Red LED → charging.
Green LED → fully charged (desired voltage reached).
b) PCB Fabrication
Design and implement a PCB prototype.
Safety Notes
• Battery Chemistry Limitation: This charger is intended only
for sealed or flooded lead-acid batteries. It is not suitable for
lithium-ion batteries, which require a controlled CC–CV
algorithm, protection circuitry, and precise voltage cutoff.
Using this design for lithium-ion charging is unsafe and
strictly prohibited.
• Testing Precautions: The circuit can supply currents up to 1 A. Students must
exercise vigilance during testing, ensure proper heatsinking of the pass
transistor, use adequately rated resistors, and avoid touching live components to
prevent burns or accidental short circuits.
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PROJECT DELIVERABLES
Phase 1: Simulation Report & Files
1. Simulation Report (Simple Format)
a) A short report (no IEEE format needed).
b) Sections:
• Title
• Introduction (project goal, short description of circuit)
• Simulation Results (with screenshots of LTSpice/Multisim waveforms, operating
point, DC sweep plots)
• Discussion (brief explanation of the results)
• Conclusion (main findings and next steps)
2. Simulation Files
a) Complete LTSpice or Multisim files.
b) Both operating point and DC sweep included.
c) Circuits properly labeled and annotated.
Phase 2: Final Report and Demo
1. Project Report (in IEEE Double-Column Conference Proceedings
Template). The report must be written using the standard IEEE
conference paper format (double column). Required sections:
a) Title, Abstract, and Keywords
b) Introduction:
• Project significance and objectives.
• Brief literature review of related regulator/battery charger designs.
• Outline of the report structure
c) Materials and Methods
• Analytical analysis of series pass regulator with voltage feedback loop
• Component sizing and justification (including power ratings and calculations)
• Bill of Materials (BOM)
• Circuit schematic (simulation and hardware versions)
• Hardware implementation details (breadboard/PCB)
• Testing procedure (simulation, open-loop test, dummy loads, battery test)
d) Results and Discussion
• Key findings with measured and simulated data
• Comparative tables (e.g., simulated vs. measured values)
• Graphical plots (e.g., Vout vs. load current, efficiency vs. load)
• Analysis of regulator performance under varying conditions
e) Conclusions
• Summary of work developed
• Challenges faced during design, testing, and measurement
• Circuit shortcomings (e.g., low efficiency, thermal dissipation)
• Possible improvements (e.g., heat management, SMPS alternative, charging
algorithms for other battery types)
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f) References
• Include at least 5–10 relevant references from reputable sources (IEEE Xplore,
textbooks, datasheets, application notes, and journal articles).
• References must follow IEEE citation style.
2. Short Demo Video (1 Minute)
• Record a concise 1-minute demonstration video. The video should be clear,
well-lit, and narrated briefly to highlight the key outcomes.
3. Final Demo & Competition
• A live demo session will be held in the lab in competition format.
• Teams will present and demonstrate their charger circuits.
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IMPORTANT DATES
Phase 1 Due Date: October 15, 2025
Phase 2 Due Date: November 15, 2025
Competition Date: Will be announced by your instructor.
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SAMPLE ILLUSTRATIONS
Figure 1: Basic Series Pass Transistor Regulator Circuit with Voltage Feedback
Figure 2: Series Pass Transistor Regulator Circuit with Voltage Feedback and output current limiting
capability.
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Figure 3: LTSpice Simulated Series Pass Transistor Regulator Circuit with Voltage Feedback and
output current limiting capability and filtering capacitors.
USEFUL RESOURCES
https://learnabout-electronics.org/Downloads/Power%20Supplies%20Module%2002.pdf
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