 Open Access
 Authors : Anziya Nazeer , Dr. S. Karthikumar
 Paper ID : IJERTV9IS050192
 Volume & Issue : Volume 09, Issue 05 (May 2020)
 Published (First Online): 13052020
 ISSN (Online) : 22780181
 Publisher Name : IJERT
 License: This work is licensed under a Creative Commons Attribution 4.0 International License
A High Voltage Gain Switched Capacitor based Boost DCDC Converter
Ms. Anziya Nazeer
P G Scholar
Electrical and Electronics Engineering Department Ilahia Collage of Engineering and Technology Muvattupuzha
Dr. S. Karthikumar
Professor and HOD
Electrical and Electronics Engineering Department Ilahia Collage of Engineering and Technology Muvattupuzha
Abstract:This paper, going to propose a high voltage gain switched capacitor based boost DC to DC. For reducing the stress of the diodes, MOSFETs and conduction loss on the switches, uses small duty cycle. This converter has an advantage of high voltage gain and a simple structure. The converter can make 300V output from a 50V input with a duty cycle of 17%. MATLAB/SIMULINK R2017a is used for simulation works. From the analysis a voltage gain of 6 is obtained at 360W output. Based on the simulation results analysis is done. Arduino microcontroller is employed to produce the switching pulses for the control circuit . To verify the performance and operating principle output voltage of 300V and input voltage of 50V with output power of 360W prototype is constructed and the results are validated.
Keywords Boost converter, dualswitch, switched capacitor, non isolated DCDC converter, high voltage gain continuous conduction mode (CCM).

INTRODUCTION
DCDC converter with high gain has increasing demands in recent days. High stepup DCDC converter is a class of converter switch can boost a low voltage to a relatively high voltage. As we known, the output voltage of fuel cell stacks, single PV module, battery sources, or the super capacitors is relatively low; it should be boosted to a high voltage to feed the ac grid or other applications like un interruptible power supplies, new energy vehicles, and so on.Lots of research works have been done to provide a high stepup without an extremely high duty ratio. The isolated converters can boost the voltage ratio by increasing the turns ratio of the high frequency transformer. However,the leakage inductor should be handled carefully; otherwise, it will cause voltage spike across the power switches or diodes. Moreover, isolated DC DC converters have the shortages in system volume and efficiency due to multistage DCACDC conversion
F. L. Tofoli [2] introduced a stepup DCDC topologies that feature high eciency, reduced stress, low cost, simplicity and robustness. W Li [3] introduced a power system for the downstream DCAC gridconnected inverter which require a DCDC converter to step up the low voltage of fuel cell or PV to a high bus voltage. Y. P. Siwakoti [4] introduced a new DCDC converter, derived from the traditional Ysource network. The proposed circuit inherits all the advantages of the Ysource including very high boost capability and exibility to choose multiple circuit parameters to tune the gain. MinhKhai Nguyen, TruongDuy Duong, and Young
Cheol Lim [1] proposes boost dcdc converter which employs the use of switched capacitor. It consists of two switches S1, S2, three diodes D0, D1, and D2 and one inductor L and three capacitors C0, C1 and C2. Vg is the input voltage and output voltage is denoted as V0. Figure 1 shows a typical arrangement of the converter. The circuit is analysed on continuous conduction mode carries some assumptions such as all devices are ideal and lossless, the capacitor values are large, the current owing through the inductor decrease or increase linearly.
Fig. 1.Switched Capacitor Based Converter
In mode 1, switch S1, S2 are turned on. At the same time diode D0 will conduct and diodes D1, D2 and D3, will not conduct. The inductor L gets charged and the capacitor C1 C2 will discharges its energy. D*T is the time duration taken for this mode, where T and D shows its switching period and duty cycle of the converter. Both the switches are turned o in mode 2. The diodes D1 and D2will conduct and diode D0 will not conduct. The time duration for this mode is D*(1 D).During this mode the energy stored in the inductor L will discharges , and the energy will stored in capacitors C1 and C2. In order to improve the voltage gain of the circuit pointed above modified the circuit by adding a switched inductor circuit in the input side. By adding switched inductor circuit in the input, it is observed that the gain can improved to 6. There is no any difference in designing aspects.

PROPOSED CONVERTER
Proposed high voltage gain Switched capacitor based boost DCDC converter is shown in fig.2. It consists couple of power switches (S1 and S2), two inductors (L1 and L2), three
capacitors (C0 C2), seven power diodes (D0 D6) and a resistive load (R).
state. D*T is the time duration taken for this mode, where T and D shows its switching period and duty cycle of the converter. By applying KVL in Fig. 3(a) the following formula is derived:
L diL1 L
diL2 V V
(1)
1 dt
2 dt
g C1
V0 Vg VC1 VC 2
(2)
Fig. 2. Proposed converter
The following assumptions are taken consideration while designing the converter:
Mode 2: Figure 3(b) shows the operating mode 2. S1 and S2 switches are turned OFF at this mode. The diodesD1, D2, D3 and D6 will conduct and the diodes D0, D4 and D5 are block the current flow. (1 D)*T is the time duration taken for this mode. During this mode, the inductor L1 and L2 are discharged through the diodes D1, D2, D3 and D6 while capacitors C1 and C2 are charged through the same path, and the following formula is derived:

All components are taken as ideal and lossless;
L diL1 L
diL2 V V

To maintain the constant capacitor voltage, capacitance of
the capacitors are made high; and
1 dt
2 dt
g C1
(3)

The current in the inductor will increases or decreases
VC1
VC2
(4)
linearly.
The circuit diagram of the high voltage gain switched
Substitute equation (1) to equation (4) after applying volt balance law to the inductor gives the following equation:
capacitor based boost DCDC converter in continues
V V V
(5)
conduction mode is shown in figure 2.


OPERATING PRINCIPLES
The working of the circuit can be explained by 2 modes of
C1 C2 g
Proposed converters Outputvoltage gain in the CCM can be obtained by substituting equation (5) in equation (2) and is shown in equation(6):
operation. Figure 3(a) and 3(b) shows the operating modes of
high voltage gain switched capacitor based boost DC DC converter in continues conduction mode .Switches S1 and S2,
GCCM V0
Vg
3 2D 1 2D
(6)
will turned on in mode one and off in mode 2.
The output current of the proposed converter is equal to the average current of the diode D0. By applying KCL in node A of Figure 2, average inductor current of the converter is as follows
IL IL Iin I0
(7)
1 2

DESIGN CONSIDERATIONS

Voltage and Current Stress on the Switches
By analyzing the operating mode, the input current is equal to the switch current (IS) in mode 1, and is equal to the inductor current in mode 2; following equation shows the average input current:
Po
Iin Vg DIS (1 D)IL
(8)
The peak current of the switches S1 and S2can find out by substituting equation (7) in (8) and is as follows:
IS
P0
D3 2DVg
(9)
Fig. 3. Operating modes of the high gain switched capacitor based boost DC DC converter: (a) mode 1 (b mode 2.

Voltage and Current Stresses on the Diode D0
The peak current of the diode D0 is calculated based on the operation in mode 1 shown in figure 3(a) is as follows:
Mode 1 : Fig. 3(a) shows the circuit .diagram in mode 1. SwitchesS1 and S2 are turned ON in this mode. The
ID0
IS IL1 IL2
(10)
switches allows a path to charge the inductor L1 and L2 and
discharge the capacitors C1 and C2.The diodes D0, D4, and D5 are forwardbiased, and the diodes D1, D2 and D3 is in blocked

Inductor Selection
Using equation (1), we can calculate the peaktopeak inductor current .By considering the ripple current of the
inductor IL = ri%IL the value of the inductor should be as follows:
D*1 D*3 2D*T*V2
TABLE 1. SIMULATION PARAMETERS
L1
g
ri %*1 2D*P0
(11)
Similarly,
D*1 D*3 2D*T*V2
Parameter
Values
Output voltage
300 V
Input voltage
50 V
Output power
450 W
Capacitors C1, C2
C0
C1, C2 22 ÂµF/100 V 110 ÂµF/450 V
Inductor L1,L2
0.5 mH
Switching frequency
50 kHz
Parameter
Values
Output voltage
300 V
Input voltage
50 V
Output power
450 W
Capacitors C1, C2
C0
C1, C2 22 ÂµF/100 V 110 ÂµF/450 V
Inductor L1,L2
0.5 mH
Switching frequency
50 kHz
L2
g
ri %*1 2D*P0
(12)

Capacitor Selection
The capacitor voltage ripple is considered while designing the capacitor value. By analysing the current flow, the switch S1speak current and current flow in capacitor C1 in mode 1 is seems to be same. The peak current of the diode D0is equal to the current ow in the capacitor C2, therefore the equations be like:
IC1
IC2
P0
D 3 2DVg
P0
D 3 2DVg

IL
(13)
(14)
The capacitances for the capacitor C1 and C2 of the converter is as follows: by considering capacitor peaktopeak voltage ripple, the capacitor voltage is restricted in amount by rv%:
1 2DTP0
Fig. 4. Simulink model of proposed converter
The simulation results of the high voltage gain switched capacitor based boost DCDC converter is shown in the
C1
C2
r %3 2DV2
V g
V g
0
0
1 2D2 TP
V g
V g
r % 3 2DV2
(15)
(16)
following gures.
The switching frequency is 50 kHz. The gate pulse of main power device has xed duty cycle of 17%.
It can be seen from the Figure 5(a) and Figure 5(b) and 5(c) that the output current is 1.2A, the output voltage V0 is about 300 V and output power is 360W. This allows high voltage
The output current in mode 2 is equal to the current ow in
output capacitor C0as shown in figure 3(b).The C0 capacitance is designed so as to reduce the ripple on the output voltage.
1 D(1 2D)2 TP
gain of lowstress converter. The output voltage has a ripple of 0.2%.As shown in Figs. 5(f) and 5(g), the voltage of the capacitor C1 and C2 is boosted to 129V.
C0
0
V g
V g
r %3 2DV2
(17)


SIMULATION RESULTS
The simulation parameters of high voltage gain switched capacitor based boost DC DC converter is given in table 1. An input voltage Vin of 50V gives an output voltage VO of 300V for an output power PO of 360W. The switches are MOSFET/Diode with constant switching frequency of 50 KHz. The duty cycle of switches is taken as D = 0.17. The high voltage gain switched capacitor based boost DC DC converter is simulated in MATLAB/SIMULINK by choosing the parameters listed in table 1 and the Simulink model is shown in figure 4
Figure 5:(a)Output Current (b) Output Voltage (c) Output Power (d) Voltage Stress S1 (e) Voltage Stress S2 (f) Voltage across C0 (g) Voltage across C1 (h) Voltage across C2
Figure 6: (a) Voltage across D0 (b) Voltage across D1 (c) Voltage across D2 (d) Voltage across D3 (e) Voltage across D4 (f) Voltage across D5 (g) Voltage across D6

ANALYSIS
The analysis of high voltage gain Switched capacitor based boost DCDC converter is carried out by considering parameters like voltage gain, eciency and duty cycle etc.
Fig.7.Voltage gain Vs duty cycle
A typical curve for the voltage gain Vs duty cycle is shown in gure 7. For a duty cycle of 17% the eciency is 97 % .
A typical curve for the eciency Vs duty cycle is shown in gure 8. For a duty cycle of 17% the eciency is 97%. Thus the eciency of a switched Capacitor DCDC Converter decreases with increase in the duty ratio.
Fig. 8. Eciency Vs duty cycle
The comparison of modified converter with conventional SCDC converter is given in table 2.
TABLE 2. COMPARISON
Parameter
SCDC
converter
Proposed converter
No of inductors
1
2
Output current ripple
0.2A
0.2A
Voltage gain
4
6
Output voltage ripple
0.4V
0.2V
No of capacitors
3
3
Switches
2
2
Output voltage
200V
300V
Output Power
200W
360W
Output Current
1A
1.2A
Input Voltage
50V
50V
A prototype of high voltage gain switched capacitor based boost dc dc converter with input voltage of 50V is implemented. The top view of the experimental setup is shown in Figure 9. It consists of control circuit, driver circuit and power circuit. Control circuit is composed of Arduino microcontroller and its power supply. The control pulses for MOSFET switches are generated using Arduino microcontroller. The pulses from microcontroller are amplified by driver circuit. It also provides isolation between control and power circuit.
Fig.9.Experimental Setup

CONCLUSION
High voltage gain Switched capacitor based boost DC DC converter boost input voltage to a very high Value, moreover it has low switch voltage stress, and conduction loss on the power switches. The switches and diodes have relatively low voltage stresses and hence the switching and conduction losses are reduced. It achieves an improved overall eciency. The input and output voltages of the converter verify the high boost voltage gain. The converter has an eciency of 97% and voltage gain of 6.A duty ratio of up to 0.17 is suitable for this converter so as to keep the voltage stress across the switches and diodes to a safe limit. The converter can be used for applications with high output voltage and can handle small output current. Moreover it can be used as LED driver and can be also used in solar system .High voltage gain Switched capacitor based boost DC DC converter can be also introduced in dc motor drives, electric automobiles ,and
marine hoists. Moreover it is used in high voltage low current applications such as accelerating purpose in cathode ray tube
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