MEV


 

 

Mechatronics, Electrical Power, and Vehicular Technology 04 (2013) 75-80 
 

Mechatronics, Electrical Power, and 
Vehicular Technology 

 
e-ISSN:2088-6985 
p-ISSN: 2087-3379 

Accreditation Number: 432/Akred-LIPI/P2MI-LIPI/04/2012 

 

 

www.mevjournal.com 
 

© 2013 RCEPM - LIPI All rights reserved 
doi: 10.14203/j.mev.2013.v4.75-80 

DESIGN AND IMPLEMENTATION OF BATTERY CHARGER WITH  
POWER FACTOR CORRECTION USING SEPIC CONVERTER AND  

FULL-BRIDGE DC-DC CONVERTER 
 

Moh. Zaenal Efendi a,*, Novie Ayub Windarko a, M. Faisal Amir a 
aDepartment of Electrical Engineering, Politeknik Elektronika Negeri Surabaya, 

Kampus PENS, Keputih Sukolilo, Surabaya 
 

Received 18 October 2013; Received in revised form 14 November 2013; Accepted 15 November 2013 
Published online 24 December 2013 

 

Abstract 
This paper presents a design and implementation of a converter which has a high power factor for battery 

charger application. The converter is a combination of a SEPIC converter and a full-bridge DC-DC converter 
connected in two stages of series circuit. The SEPIC converter works in discontinuous conduction mode and it 
serves as a power factor corrector so that the shape of input current waveform follows the shape of input voltage 
waveform. The full-bridge DC-DC converter serves as a regulator of output voltage and operates at continuous 
conduction mode. The experimental results show that the power factor of this converter system can be achieved up 
to 0.96. 

 
Keywords: SEPIC converter, full-bridge DC-DC converter, discontinuous conduction mode, power factor 
correction, battery charger. 

 
I. INTRODUCTION 

Most of modern electronic applications are 
equipped with battery which works as energy 
storage. Battery charger can be developed using 
conventional diode rectifier. However, this type 
of rectifier produces harmonics and low power 
factor. The harmonics and power factor are 
recognized as sources of disturbance in power 
quality issues. Many researchers have been 
conducting research to develop rectifiers having 
low harmonics and high power factor. 
Furthermore, the rectifier should produce low 
output voltage ripple to reduce losses in battery 
charger.  

Several methods for reducing high harmonics 
and improving power factors of rectifier circuit 
above have been proposed in several ways, such 
as installing passive filter and Power Factor 
Correction (PFC) converter. Some researchers 
have proposed to install a passive filter by using 
an inductor on the system [1]. However, this 
solution may increase the size and the weight of 
the rectifier which operates in low frequency of 

50–60 Hz. Some other researchers have proposed 
power factor correction converter to increase the 
power factor of AC-DC conversion. This system 
can be developed by two stage power factor 
correction converter which commonly uses pre-
regulator buck [2,9], pre-regulator boost [5,8], 
pre-regulator buck-boost [3,4], and others 
[6,10,11,12]. 

This paper proposes a high power factor 
battery charger. The charger consists of 
combination of two converters connected in two 
stages of series circuit. The series converters are 
SEPIC converter and full-bridge DC-DC 
converter. The block diagram of the proposed 
converter system is shown in Figure 1. 

 
II. CIRCUIT CONFIGURATION 

One of the methods for improving low power 
factor is to install a SEPIC converter as a power 
factor corrector. The SEPIC converter is series 
connected to a full bridge DC-DC converter in 
two stages which is shown in Figure 2. The 
SEPIC converter is operated in discontinuous 
conduction mode so that it will have a high 
power factor and operate as a voltage follower. 

* Corresponding Author. 
E-mail: zen@eepis-its.edu / zenefendi@gmail.com 

http://dx.doi.org/10.14203/j.mev.2013.v4.75-80


M. Z. Efendi et al. / Mechatronics, Electrical Power, and Vehicular Technology 04 (2013) 75-80 
 

 

76 

This operation principle means that the input 
current waveform follows the input voltage 
waveform [5]. Thus, the power factor will be 
close to unity. 

The circuit of SEPIC converter in Figure 3 
consists of two inductors (i.e., the first inductor is 
in input (L1) and the second inductor is in output 
(L2)). It operates in discontinuous conduction 
mode and is used to improve the power factor. 
The shape of input current waveform, which is 
shown in Figure 4, is represented by L1’s current. 
By assuming the output current (Io), the input 
current ( ii) is determined in Equation 1 [6].  

DItV
L
TD

ti otii ⋅+⋅
⋅

= ωsin
2

)( )(
1

2
 (1) 

where D is duty cycle, T is the switching period, 
Vi is the input voltage and Io is the output current. 

According to Equation 1, the SEPIC converter 
is operated in discontinuous conduction mode 
and in constant duty cycle, then the current ii(t) 
follows the shape of input voltage waveform and 
it means the SEPIC converter acts as a PFC 
converter. 

To obtain the function of PFC, SEPIC 
converter is designed to operate in discontinuous 
conduction mode with the following steps [6].  

Assume that M is ratio of the output voltage 
( oV ) and the input voltage ( iV ), then: 

𝑀𝑀 = 𝑉𝑉𝑜𝑜
𝑉𝑉𝑖𝑖

 (2) 

Ka is conduction parameter and Ka,crit is critical 
conduction parameter which are determined by: 

𝐾𝐾𝑎𝑎,𝑐𝑐𝑐𝑐𝑖𝑖𝑐𝑐 =
1

2(𝑀𝑀)2
 (3) 

which Ka<Ka,crit. Then  

𝐷𝐷 = √2  ∙ 𝑀𝑀 ∙  �𝐾𝐾𝑎𝑎  (4) 

The values of L1 and L2 which operate in 
discontinuous mode are determined by using 
Equation 5 and Equation 6.  

𝐿𝐿1 =
𝑉𝑉1  ∙ 𝐷𝐷 ∙ 𝑇𝑇
𝐼𝐼𝑐𝑐𝑖𝑖𝑟𝑟

 (5) 

and L2 can be obtained from 

AC-DC     
Full-wave 
Rectifier

SEPIC 
CONVERTER
(PFC Converter)

DC-DC
FULLBRIDGE 
CONVERTER
(DC Regulator)

LOAD

 
Figure 1. Block diagram of SEPIC converter and full- bridge DC-DC converter connected in series circuit 

 

Vs Ci

Cs

D1

i s

Q
1

Li

L1 C1

L2 C2

Q2 Q4

Q3 Q5

L3

Co R

D2 D4

D3 D5

Tr

 
Figure 2. Circuit of a SEPIC converter and a full-bridge DC-DC converter connected in the two stage of series circuit 

 

 
 

Cs

D1

Q1

L1 C1

L2Vi(t) Ci

ii Li

C2 R

IoiL1

 
 

Figure 3. Circuit of SEPIC converter 
 

DT

T

t

t

iL

D1T

Io

1

 
Figure 4. Inductor current and output current 

 



 M. Z. Efendi et al. / Mechatronics, Electrical Power, and Vehicular Technology 04 (2013) 75-80 
 
 

 

77 

𝐿𝐿2 =
𝐿𝐿1𝐿𝐿𝑒𝑒𝑒𝑒
𝐿𝐿1−𝐿𝐿𝑒𝑒𝑒𝑒

 (6) 

The equivalent inductance Leq from both 
inductors can be determined as: 

𝐿𝐿𝑒𝑒𝑒𝑒 =
𝑅𝑅 ∙ 𝑇𝑇 ∙ 𝐾𝐾𝑎𝑎

2
 (7) 

where R is resistive load and Irip is peak to peak 
of input current. The intermediate capacitor C1 is 
determined by assuming that resonant frequency 
of C1, L1, and L2 must be higher than the 
fundamental frequency. Therefore, the resonant 
frequency of C1 and L2 must be lower than the 
switching frequency [10]. The value of C1 can be 
obtained from: 

𝐶𝐶1 =
1

𝜔𝜔𝑐𝑐
2 (𝐿𝐿1 +𝐿𝐿2 )

 (8) 

Furthermore, the full-bridge DC-DC converter 
which is shown in Figure 5 serves as DC voltage 
regulator. It is designed in normal operation 
which consider to Equation 9 to Equation 11.  

Assume that d is duty cycle, then: 

𝑑𝑑 = 𝑁𝑁1𝑥𝑥 𝑉𝑉𝑜𝑜
2 𝑥𝑥 𝑁𝑁2𝑥𝑥 𝑉𝑉𝑖𝑖𝑖𝑖

 (9) 

The filter inductor can be obtained from: 

𝐿𝐿𝑐𝑐𝑐𝑐𝑖𝑖 =
(1−𝑑𝑑)

4
 𝑥𝑥 𝑅𝑅 𝑇𝑇 (10) 

And, the filter capacitor is 

𝐶𝐶𝑜𝑜 = (1 − 𝑑𝑑)𝑥𝑥
𝑉𝑉𝑜𝑜

32 𝐿𝐿𝑜𝑜𝑓𝑓2  ∆𝑉𝑉𝑜𝑜
 (11) 

 
III. IMPLEMENTATION AND 

EXPERIMENT 
To verify the design that has already been 

discussed, the converter system was built using 
the following parameters which are shown in 
Table 1 and Table 2. 

The above parameters are designed 
parameters for the converter to deliver unity 
power factor and to verify the function of battery 
charger. In this experiment, a conventional 
rectifier and a SEPIC converter are compared to 
verify the effectiveness of the design criteria. 
First test was done by providing 120 Vdc from 
full wave rectifier to full-bridge converter.  

The observed parameters are input current, 
harmonic spectrum, power factor and 
performance of full-bridge DC-DC converter. 
Figure 6 shows the values of the input current 
waveform, and the harmonic spectrum of input 
current and Figure 7 shows the value of power 
factor. Data in this experiment was obtained 
using Fluke 41B. By providing dc voltage source 
of 120 V from full wave rectifier, the 
experimental results show that the system has a 
low power factor (0.69) and high harmonic 
distortion of 70.8% of THD. 

Second experiment system was done using the 
proposed system as shown in Figure 2. Figure 8 
shows the values of the input current waveform, 
and the harmonic spectrum of input current and 
Figure 9 shows the value of power factor. The 
experimental results verify that the converter 
system has high power factor of 0.96 and 
harmonic distortion decreases to 24.2% of THD.  

Q2 Q4

Q3 Q5

L3

Co R

D2 D4

D3 D5

Tr
Vin

 
 

Figure 5. Fullbridge DC-DC converter circuit 
 

 
Table 2. 
Parameters of full-bridge DC-DC converter 

Parameter Value 

Input voltage 120 Volt 

Switching frequency 25 kHz 

Inductor L3 860 μH 

Diode D2, D3, D4, D5 
(ultra fast recovery diode) STTH 1B0L0BCWG 

Switch Q2-5 IGBT  

Transformer Tr N11:N12= 48:43 

Capacitor Co 86 μF ,450 Volt 
 

 

 
Table 1. 
Parameters of SEPIC converter 

Parameter Value 

AC input voltage 220 Volt 

Output voltage 120 Volt 

Switching frequency 25 kHz 

Inductor L1 2.6 mH 

Inductor L2 83 μH 

Diode D1 (ultra fast recovery diode) STTH 1B0L0BCWG 

Switch Q1 IGBT  

Capacitor C1 2 μF,1000 Volt 

Capacitor C2 680 μF,450 Volt 
 



M. Z. Efendi et al. / Mechatronics, Electrical Power, and Vehicular Technology 04 (2013) 75-80 
 

 

78 

Table 3 shows the experiment data of varying 
load and PFC results. This experiment is done by 
operating the proposed system with input AC 
voltage source of 220 V. The load is increased by 
around 0.5 A step. The converter can deliver 
power factor up to 0.96 which is close to unity. 
The largest power factor is 0.96 when the output 
current is 3.14 A. These results verify that the 
converter can be operated as PFC. 

Furthermore, Figure 10 shows the value of the 
power factor according to load and shows the 
trends of data in Table 3. Overall hardware 
experimental results obtained a high power 
factor. Based on data above, the correction of 
power factor is achieved from 0.69 to 0.96.  

After the experiment of PFC had already 
done, then characteristic of battery charging were 
going to be observed. There are two parameters 
which must be concerned about battery charging. 
The first parameter is the charging current and it 
should be kept to around 10% to 30% of the 
capacity of the battery (Ah: Ampere-hours) and 
the second parameter is the charging voltage and 
it should be set to 2.3 - 2.4 Volt per 2 Volt cell. 
For example a 12 Volt battery (6 cells of 2 Volt) 

is charged at 6 × 2.3 = 13.8 Volt to at 6 × 2.4 = 
14.4 Volt. 

The battery used for this experiment has a 72 
Volt of voltage that consists of 6 pieces of 12 
Volt of battery or 36 cells of 2 Volt. The capacity 
of battery that is used for this experiment is 20 
Ah (Ampere-hours). So, to meet the requirement 
of charging voltage and charging current, the 
output voltage of converter system is adjusted at 
87 Volt (36 cells times 2.4 Volt) and produces 
the charging current about 3.14 A or 10% of the 
capacity. Charging characteristic is shown in 
Figure 11. According to this figure we know that 
the battery charger can work well. 

 
 

 
 

Figure 6. Input current waveform and its parameter analysis 
of conventional rectifier 

 
 

 
 

Figure 7. Power analysis of conventional rectifier 
 

 
 

 
 

Figure 8. Input current waveform and its parameter analysis 
of SEPIC converter 

 
 

 
 

Figure 9. Power analysis of SEPIC converter 
 

Table 3. 
Overall systems performance 

Vin (V) Iin (A) Vo (V) Io (A) pF 

217 0.54 87 0.56 0.87 

218 0.83 87 1.13 0.94 

220 1.32 87 1.68 0.95 

218 1.71 87 2.15 0.96 

216 2.33 87 2.8 0.96 

220 2.48 87 3.14 0.96 
 



 M. Z. Efendi et al. / Mechatronics, Electrical Power, and Vehicular Technology 04 (2013) 75-80 
 
 

 

79 

IV. CONCLUSION 
This paper has already discussed about the 

design and implementation of a combination of 
SEPIC converter and full bridge DC-DC 
converter for battery charger application with 
power factor correction. The experimental results 
have confirmed that this converter provides high 
power factor correction up to 0.96. This converter 
can be used for battery charger application such 
as electric vehicle and electronic appliances.  

 
ACKNOWLEDGEMENT 

This research was funded by Research Unit of 
Politeknik Elektronika Negeri Surabaya (PENS) 
to Energy and Transportation Research Centre, 
budgeting year of 2013. We would thank 
chairman and staff of Research Unit of PENS for 
supporting to publish this paper. 

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[3] M. C. Ghanem, K. Al-Haddad, G. Roy, “A 
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[4] Y.M. Jiang, F.C. Lee, “A new control scheme 
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Figure 10. Chart of pF vs output current 
 

 

 
 

Figure 11. Characteristic of battery charging 
 

0.7

0.75

0.8

0.85

0.9

0.95

1

0.56 1.13 1.68 2.15 2.8 3.14

pF

Iout (A)

2.4
2.5
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2.7
2.8
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3
3.1

0
1.

32
2.

64
3.

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.1

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.1

2
22

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4

23
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6
25

.0
8

26
.4

27
.7

2
29

.0
4

Ch
ar

gi
ng

 c
ur

re
nt

 (A
)

Charging time (minute)



M. Z. Efendi et al. / Mechatronics, Electrical Power, and Vehicular Technology 04 (2013) 75-80 
 

 

80 

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	Introduction
	Circuit Configuration
	Implementation and Experiment
	Conclusion
	Acknowledgement
	References