Class: Senior Secondary School 2 (SS2 / SSS2)
Term: Second Term
Week: 6
Age: 16 years
Duration: 45 minutes
Subject: Basic Electronics
Curriculum Theme: Basic Electronics
Previous Lesson: Power Supply Unit: Types of Voltage Regulators, Series Voltage Regulator and Transistorized Voltage Regulator.
Topic: POWER SUPPLY UNIT
Subject Matter: Meaning of POWER SUPPLY UNIT, operation of voltage regulators (series voltage regulators and transistorized electronic voltage regulator), constructing a full-wave rectifier circuit with a transistorized voltage regulator.

Specific Objectives

By the end of the lesson, pupils should be able to:

Cognitive Domain:

Define a Power Supply Unit (PSU).
Explain the principle of operation of a voltage regulator.
Identify the components of a full-wave rectifier with a transistorized voltage regulator.

Affective Domain:

Appreciate the importance of stable DC power in electronic circuits.
Show interest in practical electronic circuit construction.

Psychomotor Domain:

Outline the steps involved in constructing a full-wave rectifier circuit with a transistorized voltage regulator.
Participate in the demonstration of building the circuit.

Collaborate with peers during practical demonstrations.

Reference Materials

The following resources were used in planning this lesson:

Senior Secondary Schools Education Curriculum
State Unified Scheme of Work
Basic Electronics for Senior Secondary Schools, Book 2
https://www.allaboutcircuits.com/textbook/semiconductors/chpt-9/voltage-regulators/
https://www.elprocus.com/full-wave-rectifier-circuit-diagram-working/

Instructional Materials

The teacher will teach this lesson with the aid of:

Project board
Diodes
Resistors
Transformer
Connecting wires
Transistorized voltage regulator (e.g., LM7805)
Multimeter

Rationale for the Lesson

This lesson enables pupils to understand how electronic devices receive stable and regulated power. It is important for pupils to learn about power supply units and voltage regulators as they are fundamental components in almost all electronic circuits, ensuring proper and safe operation of devices.

Prerequisite/Previous Knowledge

Pupils should have prior knowledge of basic electronic components like resistors, capacitors, diodes, and transistors, as well as the concept of rectification.

Lesson Content/Board Summary

POWER SUPPLY UNIT (PSU)

Meaning of Power Supply Unit (PSU)

A Power Supply Unit (PSU) is an electronic circuit or device that converts alternating current (AC) from the mains electricity to a stable direct current (DC) voltage required to power electronic components and devices. PSUs typically consist of a transformer, rectifier, filter, and voltage regulator.

Operation of Voltage Regulators

A voltage regulator is an electronic circuit that maintains a constant DC output voltage despite fluctuations in the input voltage or changes in the load current. This ensures a stable and reliable power supply for electronic devices.

Types of Voltage Regulators:

Series Voltage Regulators: These regulators have the control element (e.g., a transistor) connected in series with the load. They vary their resistance to maintain a constant output voltage.
Transistorized Electronic Voltage Regulator: This type uses a transistor as the main control element, often in conjunction with Zener diodes or integrated circuit (IC) regulators (e.g., LM78xx series) to provide a stable output voltage. The transistor either acts as a series pass element or a shunt element to control the voltage.

Constructing a Full-Wave Rectifier Circuit with a Transistorized Voltage Regulator

A full-wave rectifier converts the entire AC input waveform into a pulsating DC output. When combined with a transistorized voltage regulator, it provides a stable and smooth DC voltage. The basic steps for constructing such a circuit include:

Transformer Stage: Reduces the AC mains voltage to a lower AC voltage.
Rectifier Stage: Converts the low AC voltage into pulsating DC using diodes (e.g., in a bridge rectifier configuration).
Filter Stage: Smooths out the pulsating DC into a ripple-free DC using capacitors.
Regulator Stage: Uses a transistorized regulator (e.g., an LM78XX series IC or a discrete transistor circuit with a Zener diode) to maintain a constant output voltage, removing any remaining ripples and compensating for load changes.
Output Stage: Provides the regulated DC output to the load.

Key Components: Transformer, Diodes (e.g., 1N4007), Filter Capacitor (e.g., 1000µF), Voltage Regulator IC (e.g., LM7805 for 5V output) or transistors with Zener diode, Output Capacitor (e.g., 0.1µF).

Teaching Methods/Instructional Techniques

Discussion, Lecture, Demonstration, Question and Answer, Visual Aids

Instructional Procedures

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: The teacher greets the pupils, reviews the previous lesson on rectifiers, and introduces the new topic: Power Supply Unit and Voltage Regulators.
Pupils’ Activity: Pupils respond to greetings and recall previous knowledge.
Learning Point: Pupils are prepared for the new lesson.

Step 2: Meaning of Power Supply Unit (PSU)

Time: 7 minutes
Teaching Skill: Explanation/Definition
Teacher’s Activity: The teacher defines a Power Supply Unit (PSU) and explains its primary function in electronic circuits.
Pupils’ Activity: Pupils listen attentively and take notes on the definition of PSU.
Learning Point: Pupils understand what a PSU is and its importance.

Step 3: Operation of Voltage Regulators

Time: 10 minutes
Teaching Skill: Explanation/Illustration
Teacher’s Activity: The teacher explains the general principle of operation of a voltage regulator and discusses the need for stable voltage. The teacher also introduces different types of voltage regulators, focusing on series voltage regulators.
Pupils’ Activity: Pupils listen, ask questions, and contribute to the discussion on voltage stability.
Learning Point: Pupils grasp the function and types of voltage regulators.

Step 4: Transistorized Electronic Voltage Regulator

Time: 8 minutes
Teaching Skill: Detailed Explanation
Teacher’s Activity: The teacher explains the specific operation of a transistorized electronic voltage regulator, mentioning how transistors are used to maintain constant output voltage. The teacher can show a simple circuit diagram.
Pupils’ Activity: Pupils observe the circuit diagram and take notes on the operation of transistorized regulators.
Learning Point: Pupils understand the role of transistors in voltage regulation.

Step 5: Construction Demonstration

Time: 10 minutes
Teaching Skill: Demonstration/Practical Application
Teacher’s Activity: The teacher demonstrates the construction of a full-wave rectifier circuit with a transistorized voltage regulator on a project board, showing the layout, wiring steps, and identification of components. The teacher explains the function of each component during the build.
Pupils’ Activity: Pupils observe the demonstration, identify the components, and note the construction steps.
Learning Point: Pupils learn the practical steps for building the circuit.

Step 6: Practical Application and Safety

Time: 5 minutes
Teaching Skill: Guidance/Safety Instruction
Teacher’s Activity: The teacher emphasizes safety precautions during circuit construction and testing. The teacher also highlights potential applications of the constructed power supply unit.
Pupils’ Activity: Pupils pay attention to safety instructions and ask questions about applications.
Learning Point: Pupils learn about safety and practical uses of the circuit.

Step 7: Evaluation/Review

Time: 5 minutes
Teaching Skill: Questioning/Assessment
Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

What is a Power Supply Unit (PSU)?
Explain the main function of a voltage regulator.
Mention two types of voltage regulators.
List three key components required to construct a full-wave rectifier circuit with a transistorized voltage regulator.

Pupils’ Activity: Pupils answer orally and in writing.
Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 5 minutes
Teaching Skill: Summarization/Assignment
Teacher’s Activity: The teacher summarizes the key points of the lesson, reiterating the importance of PSUs and voltage regulators. The teacher then gives an assignment for pupils to research different types of IC voltage regulators.
Pupils’ Activity: Pupils listen to the summary and copy the assignment.
Learning Point: Pupils consolidate their learning and prepare for future topics.

Lesson Keywords

Power Supply Unit (PSU) – An electronic circuit that converts AC to stable DC.
Voltage Regulator – A circuit that maintains a constant output voltage despite input or load changes.
Rectifier – A circuit that converts AC to pulsating DC.
Transistor – A semiconductor device used for amplification or switching, often in regulators.
Series Regulator – A voltage regulator where the control element is in series with the load.

Differentiation

For pupils who grasp concepts quickly, the teacher can encourage them to research advanced voltage regulator circuits. For those who need more support, the teacher will provide simplified diagrams and individual guidance during the demonstration, focusing on identifying key components and their basic functions.

Note for teachers using this lesson plan

Ensure all instructional materials are readily available and in good working condition before the lesson. Emphasize safety precautions during the practical demonstration, especially when dealing with electrical components. Encourage active participation and questions from pupils to foster a deeper understanding of the concepts.