Design and Analysis of SEPIC Converter for Battery Charging Applications – Part I – Simulation Studies

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 09 Issue: 06 | June 2022 www.irjet.net p-ISSN: 2395-0072
© 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 1199
Design and Analysis of SEPIC Converter for Battery Charging
Applications – Part I – Simulation Studies
Siddalingaradhya H M1, Nalini S2
1PG Student, Department of EEE, Dr.AIT, Bengaluru, Karnataka, India
2Associate Professor, Department of EEE, Dr.AIT, Bengaluru, Karnataka, India
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ABSTRACT – In this paper, the design of sepic converter
for battery charging applications is presented. The design
procedure of sepic converter is analysed and its operation
under varying input voltage is studied. A voltage
regulation control circuit is added with PI controller and
the results are studied with different reference voltages.
The results of the proposed inverter is provided with
MATLAB/Simulink software.
I. INTRODUCTION
In past, the dc-dc converter topologies are designed for
the microgrids, filters, electric vehicles, etc., are
introduced. The most commonly used converter
topologies are boost converter, buck converter,
buckboost converters [1]. Among this, buckboost is
preferred mostly due to the adaptability and also ability
to provide both buck and boost operations. Also it
provides path to the study of various converter
structures in which the voltage sources are used for
charging the passive elements such as inductors,
capacitors, etc by providing the switching gate pulses in
order to get the required output . In recent times, sepic
converter replace the buckboost converters as the sepic
converter is able to provide output continuous current
even though at input side it is discontinuous[2]. Various
passive elements such as inductor, capacitor, etc and
active devices such as power electronic switches are
used in designing the sepic converter. Lower ESRs
(Equivalent Series Resistors), Non inverted load voltage
and current, ripple minimization etc, are few advantages
of sepic converter. The variations in the input voltage
leads to the variation in load voltages which affects the
loads. This causes the need of voltage regulation circuit
which provides constant output voltage irrespective of
the changes in the input voltages[3]. A voltage mode
control loop with PI controller provides the regulation of
output voltage under varying input voltage conditions.
In this paper, a sepic converter is designed and analysed
for battery charging applications. A PI controller based
voltage mode control loop is introduced to control the
load voltage by providing variations in reference
voltage[4]. The sepic converter is simulated in both open
loop and closed loop conditions.
II SEPIC CONVERTER:
The sepic converter circuit is shown in Fig 1 below:
Fig 1 Sepic Converter Circuit
SEPIC converter is similar to buck boost converter
topology with non inverting output. It is comprised of
two inductors connected with a coupling capacitor and a
switch. The sepic converter’s operational modes are
provided below:
Mode 1:
In this mode, the power electronic switch is turned ON
and both L1 and L2 are getting charged and the coupling
capacitor C2 is discharging. The equivalent circuit for
mode 1 of sepic converter is shown in Fig 2 below:
Fig 2 Sepic converter Mode 1 operational circuit
The voltage equation for this mode is provided below[5]:
Because the average voltage of VCs is equal to VIN [6]

Mode 2:
In this, the power electronic switch is turned ON and
both the inductors L1 and L2 are getting discharged and
the coupling capacitor C2 starts charging. The equivalent
circuit for mode 2 of sepic converter is shown in Fig 3
below:
Fig 3 Sepic converter Mode 2 operational circuit
The output voltage for mode2 is provided below:
The duty ratio of the sepic converter is calculated by
The inductors are calculated by:
The ripple current calculation of the inductors are
provided below:
The coupling capacitor is designed with the equation
provided below:
The load side capacitor value is designed as follows:
The ripple voltage of load side capacitor is provided by
the following equation:
III. CONTROL STRATEGY OF DC-DC CONVERTER
In this, the load voltage is controlled with the gate pulses
generated by the control circuit (which is shown in Fig 4)
and provided to the sepic converter. The feedback
voltage is measured from the load and compared with
the reference voltage[7]. The error dc voltage is obtained
as follows:
The generated load voltage error is provided to the
voltage controller, which generates the duty ratio as
shown below:
Where k is the sample time. The duty ratio output from
controller is subjected to pwm by comparing it with
carrier signal of higher frequency to generate the
pulses[8].
When 𝑀𝐶<𝑉𝐶, switch is turned ON
When 𝑀𝐶≥𝑉𝐶, switch is turned OFF
Fig 4 Control loop for the dc-dc converter
IV. SIMULATION RESULTS
The sepic converter with openloop pulse generation is
shown below in Fig 5:
Fig 5 Simulation circuit for open loop sepic converter
In this, the dc voltage source of 12V provides supply to
the load of 8-14V using sepic converter with switching
frequency of 30KHz.

A resistance of 100Ω is provided as load. The pulses are
generated based on the duty ratio provided as 0.5. The
load voltage in Fig 6 is as follows:
Fig 6 Open loop output voltage
The sepic converter with closed loop pulse generation in
Fig 7 is as follows:
Fig 7 Sepic converter with closed loop control
In this, the dc voltage source of 12V provides supply to
the load of 8-14V using sepic converter with switching
frequency of 30KHz.
The pulses are generated based on the duty ratio
generated by PI controller. The load voltage in Fig 8 is as
follows:
Fig 8 Output voltage with reference 8V
In this, the sepic converter is functioning as buck
converter. The reference voltage is varied to 14V and the
load voltage measured in Fig 9 is as follows:
Fig 9 Output voltage with reference 14V
In this, the sepic converter is functioning as boost
converter.
V. CONCLUSION
A sepic converter is designed and analysed for battery
charging applications and presented. The simulation
work is carried out for both open loop and closed loop. A
PI controller based voltage mode control loop is
introduced to control the load voltage by providing
variations in reference voltage in the range of 8-14V with
the input voltage of 12V. The sepic converter is
simulated in both buck and boost mode operations.
REFERENCES
[1] Sree, L., Umamaheswari, M.G.: ‘A Hankel matrix
reduced order SEPIC model for simplified
voltage control optimization and MPPT’, Sol.
Energy, 2018, 170, pp. 280–292
[2] Banaei, M.R., Sani, S.G.: “Analysis and
implementation of a new SEPIC based single-
switch buck–boost DC–DC converter with
continuous input current”, IEEE Trans. Power
Electron., 2018, 33, (12), pp. 10317–10325
[3] Singh, A.K., Pathak, M.K.: “Single-stage ZETA-
SEPIC-based multifunctional integrated
converter for plug-in electric vehicles”, IET
Electr. Syste. Transp., 2018, 8, (2), pp. 101–111
[4] A New High Step-up Gain SEPIC Converter for
Renewable Energy Applications Sajad Arab
Ansari1 , Amirreza Mizani , Javad Shokrollahi
Moghani, and Abbas Shoulaie 2019 10th
International Power Electronics, Drive Systems
and Technologies Conference (PEDSTC) 12-14
February, Shiraz University, Iran
[5] A Modified SEPIC Converter With High Static
Gain For Renewable Applications. Roger Gules,
Member IEEE, Walter Meneghette dos Santos,
Flavio Aparecido dos Reis, Eduardo Felix Ribeiro

Romaneli and Alceu André Badin, Member IEEE
November 2019
[6] Design and Implementation of a New SEPIC-
Based High Step-Up DC/DC Converter for
Renewable Energy Applications. Reza
Moradpour, Hossein Ardi and Abdolreza
Tavakoli.February 2018.
[7] A modified sepic-Based High Step-Up DC-DC
Converter with Quasi-Resonant Operation for
Renewable Energy Applications. Sara
Hasanpour, Student Member, IEEE, Alfred
Baghramian and Hamed Mojallali November
2018.
[8] Wei GU “Designing a sepic converter” national
semiconductor application note 1484 June 2007
[9].Unnat Pinsopon and Chanin and Chanin
Bunlaksananusom “modeling of a sepic
converter operating in continuous conduction
mode”, Institute of Technology Ladkrabang
(KMITL), chalongkrung Rd.Ladkrabang,Bangkok

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Design and Analysis of SEPIC Converter for Battery Charging Applications – Part I – Simulation Studies