International Journal of Inventions in Reasearch, Engineering Science and Technology (IJIREST),Vol.1,No.1,April 2014
ISSN(Print):2348-7399
ISSN(Online):2348-8077
STUDY AND SIMULATION ANALYSIS OF SINGLE
ENDED PRIMARY INDUCTANCE
voltage source, aCONVERTER
switch, a diode, an inductor,
a
capacitor
and
a
resistive
load.
This
converter
is
also
Amit Patel 1, Kamal Singh 2, Sandeep
Kumar
Singh 3 converter because the voltage
called the
step-down
Department of Electrical
Engineering
across
the inductor opposes supply voltage. The circuit
Bhagwant Institute of Technology, Muzaffarnagar1,3diagram
Radha Govind
of buckEngineering
converter isCollege,
shown inMeerut
figure21.
amitpatel1287@gmail.com1, kamalsingh32@gmail.com2, san62638@gmail.com3
Abstract: This paper presents study and simulation
analysis of Single Ended Primary Inductance
Converter (SEPIC) dc-dc converter. The paper
introduces the power converters with an overview of
different types of basic dc-dc converters. Also brief
applications of the dc-dc converters are described.
The working of SEPIC converter is explained with
advantages and disadvantages. The simulink models
of open loop and closed loop for SEPIC converter is
designed and simulated. The output voltage and
current waveforms without and with using PI
controller are obtained.
Fig. 1 Circuit diagram of buck converter
When switch turns on current flows from the source
through switch to inductor L, then capacitor C0 and
finally to the resistive load R. As current flows through
L, a magnetic field is build up, causing energy to be
stored
in the inductor. When switch is turned off, energy stored
in the inductor supplies current to the resistive load
through diode D. The voltage across the load is a
fraction of input voltage. This fraction is known as duty
cycle (D). Thus the output voltage of buck converter can
be varied as the fraction of input voltage by varying the
switching duty cycle.
The boost converter has similar structure as the
buck converter, only the difference is that it has
components arranged in different manner. The output of
boost is always greater than input voltage therefore the
boost converter is used when higher output voltage is
required than the input voltage. It is also known as stepup converter because the voltage across inductor L adds
to the input supply voltage to step-up the voltage above
input voltage. figure 2 shows the circuit diagram of
boost converter.
Keywords — SEPIC converter, MATLAB Simulink,
Dc-dc power conversion, PI controller.
I.
INTRODUCTION
The power converters are the electronic
circuits which are used for the conversion, control and
conditioning of electric power. The power range may be
from mill watts to megawatts as in electro mobile
phones and in electric power transmission system
simultaneously. Electronic devices and control circuits
must be highly robust to achieve a high useful life and
the total efficiency of the power electronic circuits must
be as high as possible. The most common technology in
all the electronic converters is switched mode power
converters. Switched mode power converters convert
the voltage input to another voltage signal by storing the
input energy and them releasing that energy to the
output at a different voltage as per switching operation.
The most common classification of power conversion
systems is based on the waveforms of input and output
signals. Thus power converters are classified as ac to dc
converters, dc to ac converters, ac to ac converters and
dc to dc converters. There are different kinds of dc-dc
converters used for several years for different
applications. Some of the applications require high
voltages while some require low voltages. Depending
on the application dc-dc converters are divided as Buck
converters, Boost converters, Buck-boost converters,
Cuk converters and SEPIC converters. The brief
introduction of these dc-dc converters is introduced in
this section.
In buck converter, the average output voltage is
less than the input voltage. Buck converter is made of a
Fig. 2 Circuit diagram of boost converter
When switch is turned on current flows through
inductor L and switch, Thus storing the energy in the
inductor in magnetic field. There is no current flowing
through diode D and the load current is supplied through
the charge stored in capacitor C0. When switch is turned
off, the inductor L opposes any drop in current. Thus the
inductor voltage adds to the source voltage, thus
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International Journal of Inventions in Reasearch, Engineering Science and Technology (IJIREST),Vol.1,No.1,April 2014
ISSN(Print):2348-7399
ISSN(Online):2348-8077
was stored in L1. When switch is turned on again, CS
discharges through L2 into the load, with L2 and C0
acting as smoothing filter, whereas at the same time
energy is being stored in L1.
stepping up the output voltage. The current now flows
from the source through inductor L, diode D and the
load, and then charging the capacitor again.
The Buck-boost converter is the combination
of buck and boost converter. The components of buckboost converter are similar but arranged in different way
to provide step up and step down voltage. The circuit
diagram of buck-boost converter is shown below:-
II. SEPIC CIRCUIT AND OPERATION
Single ended primary inductor converter
(SEPIC) is a type of converter that allows the electrical
potential i.e. voltage at its output to be greater than or
less than to that at its input. The output of the SEPIC
converter is controlled by the duty cycle of the switch.
The SEPIC converter exchanges energy between the
capacitors and inductors in order to convert from one
voltage to another. The amount of energy exchanged is
controlled by switch S. The energy to increase the
current in inductor L1 coming from the input source.
The power circuit of the SEPIC converter is presented in
figure
5.
Fig. 3 Circuit diagram of buck-boost converter
When the switch is turned on, there is path between the
inductor L and voltage source. As current flows through
the inductor L, energy is stored in magnetic field. The
diode D is reverse biased so no current flows through
the diode D to the load .The capacitor C supplies the
load current. When the switch is turned off, the path
between the inductor L and voltage source is broken.
The stored energy in the inductor L generates a voltage
which forward biases the diode D and current flows into
load and capacitor causing recharging the capacitor.
The buck, boost and buck-boost converters all
transfer the energy between input and output using the
inductor, thus building the voltage across the inductor
where as The cuk converter transfers the energy through
the capacitor. The output of cuk converter is inverted
and the circuit configuration is the combination of buck
and boost converters as in buck-boost converter. figure
4 shows the block diagram of cuk converter.
Fig. 5 Circuit diagram of SEPIC converter
When the switch is on then switch acts like a short
circuit, and the instantaneous voltage across capacitor
CS is approximately Vi, the voltage across inductor L2 is
approximately –Vi. Therefore, the capacitor CS supplies
the energy to increase the magnitude of the current in
inductor L2 and thus increase the energy stored in L2.
When switch S is turned off, the current in
capacitor CS becomes the same as the current in
inductor L1, since inductors do not allow instantaneous
changes in current. The power is delivered to the load
from both L2 and L1. CS, however is being charged by
L1 during this off cycle, and will in turn recharge L2
during the on cycle. The ratio between the input and
output is
D
Vo
= 1−D
(1)
Vi
III. ADVANTAGES AND
DISADVANTAGES OF SEPIC
Fig.4 Circuit diagram of cuk converter
When the switch is turned on, the path of swich is
shorted whereas the diode D0 is open circuited .The
current flows through inductor L1 and energy is stored
in magnetic field in inductor. When switch is turned off,
thus the path across the switch is open circuited. The
diode conducts and the current flows from voltage
source, through inductor L1, diode D0 and charging
capacitor CS by transferring to it some of the energy that
The advantages of SEPIC converter are given below: The output voltage can be less than or greater
than the input voltage.
 having non-inverted output i.e. the output
voltage is of the same polarity as the input
voltage.
 The output stage rectifier diode is used as a
reverse blocking diode.
36
International Journal of Inventions in Reasearch, Engineering Science and Technology (IJIREST),Vol.1,No.1,April 2014
ISSN(Print):2348-7399
ISSN(Online):2348-8077
 the isolation between its input and output i.e.
provided by a capacitor in series.
The disadvantages of SEPIC converter are given
below: circuit complexity because two inductors and
two capacitors are needed.
 extra conduction loss in the switch.
MULTIPLIER CAPACITOR,CM
660nF
OUTPUT CAPACITOR,Co
500μF
SWITCHING FREQUENCY,fS
48kHz
GRID FREQUENCY,fG
50Hz
The values of PI controller parameters are selected by
using the trial and error method. PI controller
parameters for the SEPIC converter obtained by trial
and error method are as follows:Proportional Gain, Kp = 0.2
Integral Gain, Ki = 0.000002
IV. APPLICATIONS OF DC-DC CONVERTERS
The different types of applications of the dc-dc
converters are given below:
 Used in high performance dc drive systems like
electric traction, electric vehicles and machine
tools.
 Used in radar and ignition systems.
 Used as photo voltaic arrays, fuel cells or wind
turbines.
 Used in drivers where the breaking of dc motor
is desired like transportation system with
frequent stops.
 In the utility ac grid as backup source of energy
like battery pack.
 In uninterrupted power supplies to adjust the
level of a rectified grid voltage to that of back
up source.
 In solar systems and in high brightness light
emitting diodes.
 In computer power supplies, battery chargers,
dc motor power systems and in different
industrial applications.
Fig.6 The open loop Simulink model of SEPIC
converter
V. SIMULATION RESULTS
The designed parameters of the SEPIC system is given
in table-1. The open loop and closed loop Simulink
models for the SEPIC converter is shown in figure 6 and
7. The single phase 115V, 50 Hz ac voltage is the input
of the SEPIC. Open loop and closed loop output voltage
and current waveforms of SEPIC are shown in figures
from 8 to 15 respectively. Different parameters of the
SEPIC are given table-1.
Table-1: Parameters of the SEPIC.
MODEL
PARAMETERS
VALUES
INPUT VOLTAGE,Vi
115V
OUTPUT VOLTAGE,Vo
345V
INDUCTOR,L1
1mH
INDUCTOR,L2
500μH
SERIES CAPACITOR,CS
660nF
Fig.7 The closed loop Simulink model of SEPIC
converter
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International Journal of Inventions in Reasearch, Engineering Science and Technology (IJIREST),Vol.1,No.1,April 2014
ISSN(Print):2348-7399
ISSN(Online):2348-8077
Fig.12 Output voltage waveform of closed loop SEPIC
converter with Vref =700V
Fig.8 Output voltage waveform of open loop SEPIC
converter
Fig.13 Output current waveform of closed loop SEPIC
converter with Vref =700V
Fig.9 Output current waveform of open loop SEPIC
converter
Fig.14 Output voltage waveform of closed loop SEPIC
converter with Vref =200V
Fig.10 Output voltage waveform of closed loop SEPIC
converter with Vref =345V
Fig.15 Output current waveform of closed loop SEPIC
converter with Vref =200V
Fig.11 Output current waveform of closed loop SEPIC
converter with Vref =345V
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International Journal of Inventions in Reasearch, Engineering Science and Technology (IJIREST),Vol.1,No.1,April 2014
ISSN(Print):2348-7399
ISSN(Online):2348-8077
V. CONCLUSIONS
[8]
The SEPIC converter is designed and
simulated. The converter model is simulated on
Simulink for open loop as well as closed loop. The PI
controller is used to control the output voltage of the
SEPIC which gives the controlled variation of output
voltage. The output voltage varies from 200V to 700V
efficiently with the help of PI controller. The closed
loop waveforms show that the rise time and peak time
of the output signals are less than that the output
waveforms of open loop system. Thus SEPIC converter
works as a good dc-dc converter with high output
voltage variation.
2003.
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