Circuit analysis is an important professional course mainly

for the students in electromagnetic education. These students

just touch university courses, too much systematic and esoteric

knowledge is difﬁcult t o a ttract s tudents a ttention. Besides,

the traditional teaching methods generally regard theoretical

knowledge as the focus of the entire semester. The equally

important practical hands-on courses are placed at the end of

the whole teaching process or be ﬁnished a s a ﬁ nal re port by

students. Due to the forgetting of the theoretical knowledge

and the difﬁculty o f t he ﬁ nal ta sk, th e st udents do no t have

sufﬁcient b asic k nowledge a nd t heoretical r eserves t o the

experimental report so that students do not think enough

about the entire teaching experiment and have their unique

innovations in the course tasks, which leads to little gains in

the learning of analog

circuit courses. To get bette r quality

of classroom teaching and deliver high quality integrated

circuit talents to the country, it is necessary to take into

account student’s knowledge absorption ability and improve

learning enthusiasm in curriculum education. Therefore, this

work proposes an innovative course teaching method of “self-

learning as the mainstay, supplemented by circuit examples”,

which allows students into the learning process of electronic

circuits. The combination of theoretical knowledge and circuit

examples can enable students to better grasp and digest the

knowledge they have learned [1], [2], [3], [4]. The

simulation tool Multisim is used in this course teaching

method, which allows students to consolidate their knowledge

and get in touch with the design and simulation of electronic

circuits in advance, [5], [6].

Fig. 1. The circuit of capacitor charging and discharging.

The innovation course teaching method combines speciﬁc

circuit examples and theoretical knowledge to increase the

interaction with students and improve student’s attention and

enthusiasm. The simulation tool Multisim enhances student’s

hands-on ability and broadens student’s thinking and explo-

ration ability. Based on effective knowledge teaching, students

can be more involved in the entire teaching process. This case

study takes “capacitor charging and discharging analysis” as an

example to describe this innovation course teaching method:

Firstly, a speciﬁc p roblem i n r eal l ife i s i ntroduced t o elicit

a related circuit example; Secondly, the key knowledge is

reviewed again based on full preview before class; Next, a

speciﬁc c ircuit i s d esigned step by step based on the problem

and the key knowledge; Finally, the software tool Multisim is

used to simulate and analyze the designed circuit.

Traditional electronic circuit teaching methods spend much

time on the detailed explanation of theoretical knowledge

to ensure that students have a correct understanding of the

knowledge of the book. In the entire traditional teaching pro-

cess, the teachers only repeat the content on the presentation

document, and the students can only learn passively and lack

the opportunity to learn independently. This case study takes

“capacitor charging and discharging analysis” as an example,

the traditional electronic circuit teaching methods give the

capacitor charging and discharging circuit shown in Fig.1

directly and conduct circuit analysis: During the capacitor

charging period, the switch S1 is closed and the switch S2 is

opened so that the capacitor C is charged by the power supply

Vs through the resistor R1; During the capacitor discharging

period, the switch S1 is opened and the switch S2 is closed

so that the capacitor C is discharged through the resistor R2.

The traditional electronic circuit teaching methods give the

circuit structure directly and explain the circuit characteristics.

A Case Study about Innovative Electromagnetic Engineering

Education based on Capacitor Charging and Discharging

HUA FAN

School of Electronic Science and Engineering, University of Electronic Science and Technology of China,

Chengdu, CHINA

Abstract:—Capacitor charging and discharging is basic knowledge in electromagnetic education. This work proposes an

innovative course teaching method of “self-learning as the mainstay, supplemented by circuit examples”, which can

improve the student’s knowledge absorption and enthusiasm in the class. The simulation tool Multisim is used as an

auxiliary software to strengthen the connection between theory and practice, which reviews the knowledge they have

learned and helps students to develop the habit of using simulation software to assist their learning. This innovative course

teaching method improves the role of students in the classroom and cultivates the ability of students to learn independently

and practice automatically, lays a foundation for the design of electromagnetic theories in the future.

Keywords:

Circuits Theory, Circuits Experiment Course; Education in Circuits, Applied Electromagnetics, Circuits and Systems

Received: April 16, 2022. Revised: February 23, 2023. Accepted: March 17, 2023. Published: April 25, 2023.

1. Introduction

2. Innovative Course Learning Method

WSEAS TRANSACTIONS on CIRCUITS and SYSTEMS

DOI: 10.37394/23201.2023.22.6

Hua Fan

E-ISSN: 2224-266X

Volume 22, 2023

Sensor Delay

switch

Room-light off

LED on

Fig. 2. Schematic diagram of the delay switch circuit.

The knowledge in the book is repeated in the traditional course

teaching methods. The students have not learned knowledge

outside the textbook so that there is no enthusiasm for learning

by repeated knowledge. This proposed innovative teaching

method abandons the traditional teaching method of “teacher

only speaks, students only listen”, and divides the course

teaching process into problem introduction, key knowledge

review, circuit examples, and Multisim simulation.

With the rapid development of modern technology, ad-

vanced technology is increasingly applied to daily life, such as

autonomous driving and home automation. In our daily life,

we may encounter some problems of forgetting to turn off

room lights and some other electrical appliances after going

out, causing energy waste and even leaving safety hazards. To

avoid these problems, a delay switch circuit is proposed here

shown in Fig.2. When we go out to close the door, the sensor

in the lock is triggered. The door-closing signal is transmitted

by the sensor to the delay switch module. After a certain

period, the lights or some other electrical appliances in the

room shut down which reduces energy waste and eliminates

safety hazards.

Before entering the class teaching formally, the common

circuit example in daily life is introduced ﬁrstly so that

students are exposed to the learning in this class and be

guided to think about the relationship between the delay switch

module and the capacitor charging and discharging. During

the next course period, the students can follow the teacher’s

teaching with questions and

gradually solving their doubts by

key knowledge “capacitor charging and discharging”, which

can make the knowledge more speciﬁc and profound.

Since the proposed course teaching method needs to spend

enough time on the analysis of speciﬁc circuit examples and

simulation veriﬁcation by the simulation tool Multisim, the

teacher does not give a detailed explanation of the theoretical

knowledge of the textbook. This class teaching method pays

more attention to the process of students self-preparation

and releases class pre-preparation homework in time. The

students need to prepare and complete the pre-preparation

report independently. The key knowledge and the problems

encountered by the students during the pre-preparation process

are organized into a speciﬁc document. This document is

recorded in the usual grades. This class teaching method

mainly lists the important key knowledge in the book on the

presentation document, and the teacher guides the students to

familiarize themselves with the key knowledge again and lay

Fig. 3. The animation schematic diagram of capacitor charging and

discharging.

the foundation for the subsequent analysis of specific circuit

examples. The animation schematic diagram of capacitor

charging and discharging is shown in Fig.3.

This class teaching method takes “capacitor charging and

discharging analysis” as an example to introduce the charging

and discharging characteristics as an important energy storage

element. As a basic component of integrated circuits, the ca-

pacitor is widely used in various fields. For example, capacitor

as an energy storage unit is widely used in capacitive ADC

arrays in SAR ADC, [7], (Successive Approximation

Analog-to-Digital converter): During the SAR ADC sampling

period, the input signal is sampled by the capacitive array

and stored in the capacitor array in the form of charge;

During the SAR ADC conversion period, the digital logic

of the SAR ADC controls the switch array of the capacitive

array to compare the input signal with the specific binary

voltage thresholds.

In the key knowledge review, the three characteristics of

capacitors are listed on the presentation document: (1) Ca-

pacitors store charge and electrical energy; (2) Capacitors

block DC signals and pass AC signals; (3) Capacitor voltage

can not be changed suddenly. After understanding the three

characteristics of capacitors, the students are guided to review

the capacitor charging and discharging circuit shown in Fig.1.

Based on the full preview, the students are guided to review

the circuit characteristics in

Fig.1 simplify and consolidate key

knowledge.

In addition to the boring review of capacitor charging

and discharging circuits, animation demonstrations have also

been introduced into this course teaching method. The an-

imation demonstrates the charging and discharging process

and describes the flow of charge and the change of the

capacitor voltage during the charging process and discharging

process. The animation demonstration also enables students

to learn and consolidate the process of capacitor charging

and discharging again, laying the foundation for the following

specific circuit example analysis.

Circuit example analysis is an innovative part of this

classroom teaching method. This proposed course teaching

method designs relevant speciﬁc electronic circuits based on

key knowledge and the introduced problems. The students

are guided to conduct a circuit analysis step by step. The

key knowledge is applied to speciﬁc circuit examples, which

improves the circuit analysis ability based on familiar key

knowledge again and also enhances the student’s enthusiasm

in learning. At the end of the speciﬁc circuit example, a

period is given for the students to raise questions about the

2.1 Problem Introduction

2.2 Key Knowledge Review

2.3 Circuit Examples

WSEAS TRANSACTIONS on CIRCUITS and SYSTEMS

DOI: 10.37394/23201.2023.22.6

Hua Fan

E-ISSN: 2224-266X

Volume 22, 2023

100

100k

61.3k

out

36k

V =5V

LED

1k

100 F



comparator

Fig. 4. Capacitive delay switch.

circuit example and discuss the raised questions in groups. The

students give their own opinions about these problems and the

teacher summarizes and answers these questions finally,

[8], [9].

According to the delay switch diagram shown in Fig.2, this

class teaching method designs a 10s capacitive delay switch

module according to the circuit characteristics of capacitor

charging and discharging. First, the capacitor discharging

circuit is determined as the delay timer circuit and the time

constant in the discharging circuit is equal to 10s; Then, a

capacitor charging circuit is designed to store enough charge

for the capacitor discharging circuit to discharge; Next, a

comparator is introduced to compare the output voltage of the

discharging circuit and the threshold voltage. When the output

voltage of the discharging circuit is less than the threshold

voltage, the output signal of the comparator is submitted in

the next control module. Finally, the control signal of the

comparator controls the switch close, thereby the LED light

is on in the output circuit. The design circuit diagram of the

entire delay switch is shown in Fig.4.

The circuit example of this course teaching method adopts

the new teaching method of “ﬁrst d ivided, t hen t otal”. Taking

the capacitive delay switch as an example, the whole design is

divided into various modules and designed step by step ﬁrstly,

and then these divided modules are combined to complete the

total delay switch circuit: Firstly, the core part of the delay

module should be designed ﬁrst. A ccording t o t he c oncept of

the capacitor charging and discharging in the key knowledge

review section, the time constant of the discharging circuit is

used as in the time delay module, so the value of capacitance

and resistance in the discharging circuit should meet the

time constant of 10s. Secondly, the capacitor discharging

circuit is used as a delay module, so a capacitor charging

circuit is designed to quickly charge the capacitor for the

capacitor discharging circuit. According to the review of key

knowledge, the charging speed of a capacitor is related to

its time constant. Therefore, it is determined to add a small

resistance element to the capacitor charging circuit for fast

charging. Thirdly, detecting when the discharge voltage of the

capacitor discharging circuit falls at its time constant has also

become a problem, so a voltage comparator is introduced. A

threshold voltage is connected at the positive terminal of the

comparator, which value is exactly the discharge voltage at its

time constant of the discharging circuit, and then the output

(a) (b)

Fig. 5. Application examples of capacitor charging and discharging:(a)

Camera ﬂash; (b) Super-capacitor bus.

voltage of the discharging circuit is connected to the negative

terminal input of the comparator, when the comparator detects

the output voltage of the discharging circuit is less than the

threshold voltage, a changing comparator output signal is

obtained. Lastly, the switch controlled by the output signal of

the comparator makes the LED light on in the output display

circuit, and the whole design of the entire capacitive delay

switch is completed. In this circuit example, the comparator

module is used, which is particularly important for the basis

of analog circuits. However, this course teaching method does

not focus on the internal structure of the comparator but the

characteristics of the comparator.

This course teaching method introduces two more appli-

cation examples, one is the camera ﬂash, and the other is

the super-capacitor, as shown in Fig.5. The camera ﬂash

uses capacitor charging and discharging to quickly release the

energy stored in the capacitor to produce a ﬂash.

Ordinary capacitors have high discharging power, but the

energy density of the ordinary capacitor is generally less than

0.1Wh/kg, which is difﬁcult to be used as an energy storage

element in real life. Therefore, the super-capacitor combines

the high discharging power of the capacitor and the powerful

charge storage capacity of the lithium battery. Super-capacitor

is generally used in wind power pitch systems and super-

capacitive battery systems for new energy vehicles. The super-

capacitor bus applies super-capacitors to the energy storage

system. Each time the bus stops and waits for guests to get on

and off the bus, the super-capacitor bus extends the bracket

to connect the platform power supply and the super-capacitive

battery system for fast charging. In just a few tens of seconds

of waiting time, the platform power supply can charge the

super-capacitive battery system and the stored energy is far

enough for the bus to drive to the next bus station.

This case study represents three common circuit examples

of capacitors: capacitor delay switch module, camera ﬂash,

and super-capacitor application. The key knowledge learned

in the classroom is quickly and accurately applied to actual

application examples, which not only consolidate the learned

knowledge but also enhance student’s learning enthusiasm.

Since the electronic circuit course is very practical, more

students are required to complete the circuit design inde-

pendently. If hardware experiments are used, there are the

2.4 Multisim Simulation

WSEAS TRANSACTIONS on CIRCUITS and SYSTEMS

DOI: 10.37394/23201.2023.22.6

Hua Fan

E-ISSN: 2224-266X

Volume 22, 2023

100Ω

100µF

100kΩ

61.3kΩ

36kΩ

S1 键 = A

0.9mA 0A

1kΩ

LED

键 = B comparator

OPAMP_5T_VIRTUAL

Fig. 6. Multisim simulation diagram of capacitive delay switch.

following problems: (1) Because the hardware components

are too complex and the hands-on ability requirements are

high that make students lack interest and initiative in learn-

ing; (2) Because students are not clear about the principle,

there are contingency and blindness in the operation process,

which causes a high damage rate to the equipment and make

the experimental project fail to complete. Therefore, how to

complete the simulation of circuit examples in a short time

with high quality and quantity has become a problem that

needs to be solved in classroom teaching. With the rapid

popularization of computer technology, the use of computer

simulation software to analyze, simulate, and optimize cir-

cuits has become an effective method. The use of Multisim

software in the course teaching process not only reduces the

experimental cost of course design but also greatly improves

the classroom teaching efficiency and student’s learning ability,

which effectively stimulates student’s interest in learning,

[10], [11].

The use of Multisim can enable students to have a direct

impact on circuit construction and circuit results before doing

hardware experiments, and understand the impact of various

circuit components in electronic circuits on the performance

of the entire circuit. This enables students to have a deeper

understanding of the experimental content and master the

theoretical knowledge of electronic circuits. After the simu-

lation experiment is completed, the circuit is built and tested

on the test bench, and the simulation and measured results

are compared and analyzed. Through the combination of

simulation experiments and physical experiments, students can

master common circuit solutions and improve their ability

to analyze complex circuits. In the teaching method, the

Multisim software helps students develop the learning habit of

combining theoretical knowledge and simulation veriﬁcation

and lay a good foundation for the design of integrated circuits.

According to speciﬁc c apacitive d elay m odule i n t he last

part, the students independently select the corresponding com-

ponents to build the circuit and simulate in Multisim. The

speciﬁc d elay s witch c ircuit i s s hown i n Fig.6.

Since a comparator is used in this circuit example that the

students have not touched, the comparator model (OPAMP-5T-

VIRTUAL) is given to reduce the interference problem in the

process of building the circuit. During the circuit simulation

process, the teacher walks around and observes the student’s

construction process. Finally, students organize the simulation

circuit, simulation results, and problems in the simulation

process into a speciﬁc document, which becomes a part of the

usual performance assessment. Besides, the use of Multisim

simulation software is difﬁcult for students. Therefore, at the

beginning of formal course teaching, one class time is used

to lead students to familiarize and use Multisim software for

subsequent course teaching.

Circuit analysis is the ﬁrst professional course for freshmen

in engineering education and an innovative teaching method

of “self-learning as the mainstay, supplemented by circuit

examples” is proposed in this work. This course teaching

method repeats the key knowledge simply and designs a

speciﬁc circuit according to a problem in real life, and the

designed circuit is simulated by Multisim software, which can

effectively improve

astudent’s professional level and innovation

ability. This proposed teaching method promotes student’s

knowledge learning and the effectiveness of simulation ver-

iﬁcation learning.

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3. Conclusion

References

WSEAS TRANSACTIONS on CIRCUITS and SYSTEMS

DOI: 10.37394/23201.2023.22.6

Hua Fan

E-ISSN: 2224-266X

Volume 22, 2023

Contribution of Individual Authors to the

Creation of a Scientific Article (Ghostwriting

Policy)

The author contributed in the present research, at all

stages from the formulation of the problem to the

final findings and solution.

Sources of Funding for Research Presented in a

Scientific Article or Scientific Article Itself

No funding was received for conducting this study.

Conflict of Interest

The author has no conflict of interest to declare that

is relevant to the content of this article.

Creative Commons Attribution License 4.0

(Attribution 4.0 International, CC BY 4.0)

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_US

WSEAS TRANSACTIONS on CIRCUITS and SYSTEMS

DOI: 10.37394/23201.2023.22.6

Hua Fan

E-ISSN: 2224-266X

Volume 22, 2023