High step up switched capacitor inductor dc voltage regulator

1. Proceedings of the International Conference on Emerging Trends in Engineering and Management (ICETEM14)
30-31, December, 2014, Ernakulam, India
261
HIGH STEP UP SWITCHED CAPACITOR INDUCTOR DC
VOLTAGE REGULATOR
SHAHANA JABAR, Mr. JOSE SEBASTIAN T.K
1
Dept. of Electrical & Electronics Eng., Government Engineering College Thrissur,
Kombanaparambil (H), Thodupuzha, Idukki, kerala, India,
2
Dept. of Electrical & Electronics Eng., Government Engineering College Thrissur,
Thalakkottur(H), Aiswaria nagar, West fort,India
ABSTRACT
A new converter using a switched-inductor cell integrated with a switched-capacitor cell within a boost-like
structure is proposed. The converter can achieve a very high dc conversion ratio. It can serve as the front-end dc-dc
converter for a voltage regulator system. The inductors and capacitors are switched in a parallel-series configuration. The
charging circuit of the inductors from the source is separated from the load. A dc analysis of the new circuit leading to
the formula of the dc gain and a breakdown calculation of the losses are given. The proposed Switched Capacitor
Inductor (SCI) converter circuit can meet the high efficiency requirement and simple structure. A small resonant inductor
is used in these converters to limit the current peak caused by switched capacitor. Therefore, the SCI converters have
good performance and high efficiency as well the voltage stress of the converter is reduced. In order to verify the
proposed Switched Capacitor Inductor (SCI) dc-dc converter, modeling and simulation was carried out by using
MATLAB.
Keywords: High Voltage Gain, Switched Capacitor, Switched Inductor
1. INTRODUCTION
The need for a DC/DC converter of this caliber is a great one. The future is looking towards alternative power
sources all of which will need to be regulated in one Form or another. To make this possible, a highly efficient low cost
product will have to be designed. Among all the different converter designs only a few are capable of providing high
power with high efficiency. The basic switched-mode dc–dc converters including buck, boost, buck-boost, cuk, zeta, and
sepic have been used in various electronic applications due to their numerous advantages such as simple structure, good
performance, high efficiency, easy design, and simple control circuit [1]. The resonant converters such as single-ended
and bridge type are also very popular in the last decade [2], [3]. And the basic switched-capacitor (SC) converters also
have wide application as their advantages of nonmagnetic components employed and small size and high power density
[4], [5]. A small resonant inductor has been added in SC converters to eliminate the current peak and achieve soft
switching in [6] and, therefore, the SC Converters have good performance and high step up as well.
In recent years, many researchers are trying to take these types of converters aforementioned into a new type of
combination converters to obtain high step-up voltage gains. Even though these converters have different structures and
can provide different voltage conversion ratios, they have a characteristic in common which is that all of them are
multistage combination of switched-inductor cells and SC cells. Like other cascaded high step-up converters, in which
energy is transferred from one unit to next unit and gradually to output stage, their efficiency is therefore generally not
promising and is equal to the product of Efficiency.
INTERNATIONAL JOURNAL OF ELECTRICAL ENGINEERING &
TECHNOLOGY (IJEET)
ISSN 0976 – 6545(Print)
ISSN 0976 – 6553(Online)
Volume 5, Issue 12, December (2014), pp. 261-269
© IAEME: www.iaeme.com/IJEET.asp
Journal Impact Factor (2014): 6.8310 (Calculated by GISI)
www.jifactor.com
IJEET
© I A E M E

2. Proceedings of the International Conference on Emerging Trends in Engineering and Management (ICETEM14)
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262
In this paper, a high efficiency Switched Capacitor Inductor DC-DC converter is proposed. The converter
composed of the following components: include two energy transfer components, i.e., one Switched Capacitor C1 and
one switched inductor L1, a small resonant inductor Lr that is employed to limit the current peak caused by SC, three
active or passive switches and one output filter capacitor. The greatest feature of these converters is that energy flowing
from input power sources is directly transferred to the two energy transfer components (C1 and L1) and then directly
released to output terminal, i.e., these converters are actually single-stage dc–dc converters rather than like
aforementioned converters obtained high voltage gain by using different cascading methods. When the two energy
transfer components operate in parallel manner during a charging process and then in series manner during a discharging
period, the higher output level can be produced. Similarly, this principle is not only suitable for deriving single-input
converters, but can also be extended to dual-input dc-dc converters that are popularly used in dual-level dc distributional
and renewable energy system. To distinguish the proposed family of converters from conventional SC/SI converters
introduced in literatures, the proposed converters are hence named high gain switched capacitor inductor (SCI)
converters. This paper is organized as follows: Section II introduces the block diagram of proposed voltage regulator
system. Section III introduces the proposed SCI dc-dc converter, which consists the detailed analysis of the operating
principle and oscillation amplitude along with design consideration of SCI converter. Section IV introduces the proposed
high step up SCI dc voltage regulator. Section V introduces the simulation and experimental result discussion of SCI dc-
dc converter. Finally, this paper is concluded in Section VI.
2. PROPOSED VOLTAGE REGULATOR SYSTEM
High step up SCI converter can be used for verity of applications including Battery charger, UPS System with
Renewable Energy Source, Voltage regulator.Switching regulators rapidly switch a series device on and off. The duty
cycle of the switch sets how much charge is transferred to the load. This is controlled by a similar feedback mechanism
as in a linear regulator. Because the series element is either fully conducting, or switched off, it dissipates almost no
power; this is what gives the switching design its efficiency. Switching regulators are also able to generate output
voltages which are higher than the input, or of opposite polarity — something not possible with a linear design.
FIG. 1. PROPOSED VOLTAGE REGULATOR SYSTEM
3. SCI DC-DC CONVERTERS
The proposed SCI dc-dc converter circuit is shown in Figure 2. The circuit uses only one active switch Q and a
very small resonant inductor Lr which is employed to limit the current peak caused by capacitor C1 when the switch Q is
turned ON. The two energy storage components C1 and L1 are alternately connected in parallel and series according to
different switching states. Voltage transfer relationship can be derived and expressed as follows,
0
2
1
in
d
V V
d
−
=
−
(1)

3. Proceedings of the International Conference on Emerging Trends in Engineering and Management (ICETEM14)
30-31, December, 2014, Ernakulam, India
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FIG. 2. HIGH STEP UP SCI CONVERTER
There are two inductors employed in this converter, the energy transfer inductor L1 and the resonant inductor Lr
. The function of L1 is to transfer energy while Lr is just used to limit the current peak caused by the capacitor C1 when
the switch Q is turned ON. Specifically, when switch Q is turned ON, the capacitor C1 begins to be charged or to
discharge, the charging or discharging current will soar to a very high peak at the moment of Q being ON if there are not
any measures to limit it. For this reason, a small inductor Lr is added and connected in series with C1 to form a resonant
tank with the resonant frequency fO = 1/2π √ LrC1 during the switching ON period. With the resonant inductor, the
charging or discharging current of C1 gradually increases from zero when switch Q is turned ON. In order to ensure that
the current changes back to zero before switch Q is turned OFF, the switch conduction time should be longer than half of
a period of the resonant frequency, i.e., dTS > π √ LrC1(where TS and d are the switching cycle period and duty ratio,
respectively).
3.1. Mode of Operation of the Converter
For the SCI converter shown in Fig. 2, there are three working states in one period of switching cycle. Fig. 3
shows its three state circuits and its idealized waveforms are shown in Fig. 4. The following detailed analysis is based on
the assumptions that: all components are ideal, i.e., there are no voltage drop and on-resistance; the inductor L1 operates
in continuous current mode; the output filter capacitor C2 is so large such that the output voltage ripple is ignorable and it
can therefore be seemed as a constant voltage source VO .
3.1.1. State I (t0−t1)
When the switch Q is turned ON, diode D2 is reversely biased. D1 is forward biased and the resonant inductor
Lr is connected in series with C1 to form a resonant tank. The input voltage V1 is developed across the resonant tank that
causes the resonant current iC1 gradually increases from zero in a sinusoidal manner; C1 begins to be charged and its
voltage increases from its minimum value.
FIG. 3. STATE CIRCUITS FOR CONVERTER (A) STATE I (T0 –T1). (B) STATE II (T1 –T2). (C) STATE III
(T2 –T3).

4. Proceedings of the International Conference on Emerging Trends in Engineering and Management (ICETEM14)
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Meanwhile, input voltage is developed across inductor L1 causing a linear increase in current iL1. The state circuit is
shown in Fig. 3(a) and the idealized waveforms are shown in Fig. 4. This status can also be mathematically described as:
1 1 0 0sin ( )c ci I t tω= − (2)
1
1 1 0 0cos ( )
2
c
c
V
V V t tω
∆
= − − (3)
1
1 1 min 0
1
( )L L
V
i I t t
L
−= + − (4)
Where ω0 resonant angular frequency IC1 and ∆VC1 are oscillation amplitudes of the current and voltage of capacitor C1,
respectively, and both are related to the output current; IL1−min is the minimum value of the current flowing through L1.
After Lr and C1 resonate for half of a cycle, the resonant current iC1 falls back to zero and then diode D1 is reversely
biased. The resonance stops and the capacitor voltage reaches to its maximum value at time t, i.e.,
1
1 max 1
2
c
c
V
V V−
∆
= + (5)
3.1.2. State II (t1−t2)
After the resonance stops, the switch Q continues to conduct and the inductor current iL1 continues to rise
linearly as given by (4).There is no current flowing though C1 and its voltage is maintained the maximum value. The
state circuit is shown in Fig. 3(b).This state continues until the switch is turned OFF as shown in Fig. 4 time from t1 to t2,
and then the inductor current iL1 rises to its maximum value.
1
1 max 1 min
1
L L s
V
i I dT
L
− −= + (6)
FIG. 4. SOME IDEALIZED WAVEFORMS FOR A HIGH STEP-UP CONVERTER

5. Proceedings of the International Conference on Emerging Trends in Engineering and Management (ICETEM14)
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3.1.3. State III (t2−t3)
After switch Q is turned OFF, diode D2 is forward biased and D1 is reversely biased. The capacitor C1, the
inductor L1, and input source are connected in series and discharge to VO as shown in Fig. 3(c).The currents flowing
though C1 and L1 are therefore the same and can be expressed as:
0 1 1
1 1 1 min 2
1
( )c
L c L
V V V
i i I t t
L
−
− −
= − = − − (7)
Based on the assumption that the switching frequency is high enough the changes of capacitor voltage VC1 and
discharging current iL1 can be approximated as linear with time, i.e.,
0 1 1
1 1 1 min 2
1
( )c
L c L
V V V
i i I t t
L
−
− −
= − ≈ − − (8)
0
1 1 max 2
1
( )
(1 )
c c
I
V V t t
d C
−≈ − −
−
(9)
At the end of this state, i.e., time t3, the loop current iL1 and the capacitor voltage VC1 both decrease to their minimum
values. And then, the switch Q is turned ON again and the three states will be repeated.
3.2. Design Considerations
Based on the previous analysis, the values ofC1 and Lr can be determined by the design requirements of the
resonant current and voltage. And the value of L1 can be determined by the design requirements of its current ripple. The
design process therefore can be divided into the following steps:
1) Determine the values of the duty ratio and the switching frequency, and then calculate the resonant frequency
according to the condition that the switch conduction time should be longer than half of a period of resonant frequency,
i.e.,
0
1
1 1
22 sr
f
dTL Cπ
= > (10)
2) The value of the capacitor C1 can be calculated by, i.e,
0
1
1
s
C
I T
C
V
=
∆
(11)
3) The resonant inductor Lr hence can be determined by the value of C1 and the resonant frequency, i.e.,
2 2
0 1
1
4
rL
f Cπ
= (12)
4) The value of inductor L1 can be determined by, i.e.,
1
1
1
s
L
V dT
L
I
=
∆
(13)
Where ∆IL1 is the design requirement of the current ripple flowing through L1 .
4. SWITCHED CAPACTOR INDUCTOR DC VOLAGE REGULATOR .
Switched-mode power supply (switching-mode power supply, SMPS, or switcher) is an electronic power supply
that incorporates a switching regulator to convert electrical power efficiently. Like other power supplies, an SMPS
transfers power from a source, like mains power, to a load, such as a personal computer, while converting voltage and
current characteristics.
A feedback circuit (voltage sensor circuit) measures or monitors the output voltage and compares it with a
reference voltage, which shown in the block diagram Fig: 1. serves this purpose. When it is lower than the desired
voltage, it turns on the switch. When the output voltage is above the desired voltage, it turns off the switch. The
advantage of using switching regulators is that they offer higher efficiency than linear regulators. The complete system
overview of high gain SCI DC voltage regulator is shown in Fig 5. Switching pulses to mosfet is produced using The

6. Proceedings of the International Conference on Emerging Trends in Engineering and Management (ICETEM14)
30-31, December, 2014, Ernakulam, India
266
Atmel AVR ATmega8 .AVR is made to operate in Fast PWM Mode (WGM1:0 =3). It is used to create high resolution
PWM waveforms with same frequency, different duty cycle.
FIG. 5. TOTAL SYSTEM OVERVIEW
Three distinct steps used for programming process are writing the code, debugging the code, programming in
AVR. The programming language for microcontrollers is Flowcode V5 for AVR. The flowchart of program for high gain
SCI DC voltage regulator is shown in Fig 6.
FIG. 6. FLOWCHART OF THE PROGRAM
5. SIMULATION AND EXPERIMENTAL RESULTS
5.1. Simulation parameter for the Proposed High Step-Up Regulator
The Closed loop simulation of High step up Switched capacitor inductor converter is made and a prototype of
the converter with closed loop voltage control is made. The following TABLE I shows the component details of
simulation model and prototype circuit of high step up SCI converter which is calculated using equations in design
consideration with ∆Vc=0.03V and ∆IL=0.8A .

7. Proceedings of the International Conference on Emerging Trends in Engineering and Management (ICETEM14)
30-31, December, 2014, Ernakulam, India
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TABLE I. SIMULATION PARAMETER
5.2 .Closed loop simulation of high step up SCI converter (DC voltage regulator)
Figure 7 shows the simulink model of the closed loop high step up SCI converter. Closed loop provides
regulated output voltage for input voltage variation. In closed loop control, the output voltage of converter is compared
with required constant output voltage. The error is given to the PI controller. PI controller parameters are obtained by
trial and error method. The output of PI controller is combined with ramp signal for the main switch.
FIG. 7. SIMULINK MODEL OF THE CLOSED LOOP CONVERTER.
Input Voltage (12-15)V DC
Maximum output Power 5W
Switching Frequency 28kHz
Capacitor C1 2µF
Capacitor C2 1400µF
Inductor L1 450µH
Resonant Inductor Lr 2.7µH
Resistor R 1kΩ

8. Proceedings of the International Conference on Emerging Trends in Engineering and Management (ICETEM14)
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FIG. 8. INPUT & OUTPUT VOLTAGE OF CLOSED LOOP HIGH STEP UP SCI CONVERTER
5.3. Experimental set up and Results discussions for the proposed High step up regulator
A prototype circuit of the closed loop high step-up converter has also been built as shown in Fig. 9 to confirm
the theoretical analysis and simulation results, the experimental results are shown in Fig. 8 when the output is connected
to a 1-k pure resistor load. It is evident that the results agree to and are supported by the preceding analysis and
simulation results.
Output voltage Vo of the converter with input voltage of 12.4V simulated in MATLAB is show in fig 10. The
corresponding experimental result is shown in fig. 11. As can be seen, the output voltage is 74V.The resonant switching
techniques introduced to this converter further improved the performance of converter. When the input powers V1=10V,
load is a 1-k pure resistor, and the switch Q is operated at 28-kHz switching frequency, the output voltage is 74 V.
FIG. 9. EXPERIMENTAL SETUP FIG. 10. SIMULATED OUTPUT VOLTAGE
FIG. 11. EXPERIMENTAL OUTPUT VOLTAGE WITH VIN=12.4V, OUTPUT VOLTAGE VO=74V), UPPER
TRACE: OUTPUT VOLTAGE; LOWER TRACE: INPUT VOLTAGE

9. Proceedings of the International Conference on Emerging Trends in Engineering and Management (ICETEM14)
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6. CONCLUSION
In this project work, a high step up SCI DC voltage regulator is designed simulated and a hardware prototype is
made. High step up SCI DC converter without feedback and High step up SCI inverter circuit are also simulated .The
SCI dc-dc converter give high step up and efficiency compared with conventional SC converter , hence we can apply this
converter for making UPS system with renewable energy sources , voltage regulator etc.
The proposed converters employ two energy transfer components (one SC and one inductor) and do not use the
cascade method like conventional SC/switched-inductor converters. The energy stored in the two components both
directly come from input power sources and then directly been released to output terminal. This design can meet the high
efficiency requirement with a simple structure. A resonance method is used in this paper to limit the current peak caused
by the SC. Detailed analysis and design considerations are also introduced. Compared with traditional switched-mode
converters, the proposed converters can provide higher voltage gains and the switch stress is lower. The SC converter
voltage stress is high because of using more number of switches. In SCI converter used one switch therefore voltage
stress of the converter is reduced. The renewable energy sources can give more efficient power by using SCI dc-dc
converter.
The complete circuit including the high step up SCI converter with microcontroller based voltage control has
been tested to demonstrate the claimed features. This project work has described the basic circuit operating principle,
device selection, and passive component design procedure to achieve the desired high voltage ratio.
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Books
[1] Bert Van Dam “Microcontroller system engineering” and Atmel-2486-8-bit-AVR-microcontroller-ATmega8
datasheet.