INTERNATIONAL JOURNAL FOR RESEARCH IN EMERGING SCIENCE AND TECHNOLOGY, VOLUME-3, ISSUE-7, JUL-2016
E-ISSN: 2349-761
Analysis, Design and Simulation of DC-DC Boost
Converter
Lovepreet Kaur Grewal1 and Navdeep Kaur Brar 2
1
M.tech, Department of Electrical Engineering, Baba Banda Singh Bahadur Engineering College, Fatehgarh Sahib,
Punjab, India
1
lovepreet.grewal8@gmail.com
2
Professor, Department of Electrical Engineering, Baba Banda Singh Bahadur Engineering College, Fatehgarh Sahib,
Punjab, India
2
navdeep.kaur@bbsbec.ac.in
ABSTRACT
The objective of this paper is to analyze, design and simulate the Boost (step-up) switching converter. The converter performance
such as load voltage, currents in capacitor and inductor, ripples of voltages and currents, etc. are analyzed and derived under
continuous operations. The design of the converter is performed to step-up the input voltage 12 v to an output voltage of 24 v.
LTspice IV programs are used to simulate the Boost switching converter operation using a very high speed MOSFET as a switch
with 20 KHz switching frequency. The simulated results are compared with theoretical and the percentage error is found to be
very small.
Keywords— Boost converter, Spice simulations.
1. INTRODUCTION
high frequency to convert a dc input voltage VIN into a dc
Dc-dc power converters are employed in a variety of
output voltage VOUT, and (ii) a control unit, which is used to
applications, including power supplies for Personal computers,
control the ON/OFF operation of the switching element of said
office equipment, spacecraft power systems, laptop computers,
switching power supply unit.[5]
and telecommunications equipment, as well as dc motor
LTspice IV is a high performance SPICE simulator, schematic
drives. The input to a dc-dc converter is an unregulated dc
capture and waveform viewer with enhancements and models
voltage Vg. The converter produces a regulated output voltage
for easing the simulation of switching regulators.
V, having a magnitude (and possibly polarity) that differs from
enhancements to SPICE have made simulating switching
Vg.
regulators extremely fast compared to normal SPICE
The dc-dc converter is a dc power supply that is small,
simulators, allowing the user to view waveforms for most
lightweight & highly efficient, and uses a semiconductor
switching regulators in just a few minutes. LTspice IV is
switching element. It can response quickly and suitable to
freeware computer software implementing a SPICE simulator
changes in input voltage within the scope of normal operating
of
conditions to return to the normal operating state. It is
manufacturer Linear Technology (LTC). LTspice IV provides
comprised of (i) switching power supply unit which, can turn
a schematic capture and waveform viewer with enhancements
ON/OFF switching elements that can be turned ON/OFF at
and models to speed the simulation of switching regulators.
VOLUME-3, ISSUE-7, JUL-2016
electronic
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circuits,
produced
by
Our
semiconductor
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INTERNATIONAL JOURNAL FOR RESEARCH IN EMERGING SCIENCE AND TECHNOLOGY, VOLUME-3, ISSUE-7, JUL-2016
E-ISSN: 2349-761
Supplied with LTspice IV are macro models for 80% of LTC's
instantaneously, the voltage in the inductor reverses its
switching regulators and operational amplifiers, transistors,
polarity in an attempt to maintain a constant current. The
MOSFETs, and passive components.[1]
current which was flowing through the switching transistor
will now flow through L, C, diode D and load. The inductor
2. THEORY OF BOOST CONVERTER
current decreases until the switching transistor is turned on
The Boost converter is capable of providing as output voltage
again during the next cycle. The inductor delivers its stored
that is greater than the input voltage. It is also known as a step-
energy to the output capacitor, C, and charges it up via D to a
up converter. A boost converter using a MOSFET transistor as
higher voltage than input voltage, V S. This energy supplies the
the switching transistor is shown in Fig-1.
current and replenishes the charge drained away during the on
time.
Fig-1: Circuit diagram of Boost converter
The operation of the boost converter can be divided into two
modes:
Mode 1 (0 < t < ton)
Mode 1 begins when the switching mosfet, M1, is switched on
at a time t = 0 and it terminates at t = ton. The equivalent
Fig-3: Waveforms of converter
circuit for mode 1 is shown in Fig-2. The diode D is reverse
biased since the voltage drop across the drain-source junction
of the switching transistor is smaller than the output voltage.
The output current during this interval is supplied entirely
from the output capacitor, C, which is choose large enough to
supply the load current during ton with a minimum specified
The equations for boost converter are given as below:
diL / dt = (VO – VS ) / L …………………………………….(3)
dVO/ dt = ( IL – VO / R) / C ……………………………........(4)
If the current flowing through the inductor falls to zero before
the next turn-on of the switching transistor, M1, the Boost
converter is said to be operating in the discontinuous mode. To
drop in output current.
The equations for boost converter are given as below:
diL / dt = VS / L ……………………………………………..(1)
dVO/ dt = ( IL – VO / R) / C ...………………………….........(2)
ensure that the Boost converter is operates in continues mode
the inductor L must be less than critical inductor, LC, which
given by:
LC = RD (1-D)2 / 2 fS ………………………………….......(5)
Where R= load resistance
D= duty cycle
fs= switching frequency
3. Design of boost switching converter
The design of the converter is performed to step-up the input
voltage of 12V to an output voltage of 24V. The following
Fig-2: Operating states
parameters are required for the design of the Boost converter:
Mode 2 (ton < t ≤ T)
Input voltage (VS) = 12V,
Mode 2 begins when the switching transistor, M1, is switching
off at t = ton. The equivalent circuit for this mode is shown in
Fig-2. Since the current in the inductor cannot change
VOLUME-3, ISSUE-7, JUL-2016
Output voltage (VO) = 24V,
Switching frequency (fS) = 20 KHz,
Maximum load current (IOmax) = 2A,
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INTERNATIONAL JOURNAL FOR RESEARCH IN EMERGING SCIENCE AND TECHNOLOGY, VOLUME-3, ISSUE-7, JUL-2016
E-ISSN: 2349-761
Maximum inductor current (ILmax) = 4.25A,
theoretical waveforms. The response of the output voltage is
Minimum inductor current (ILmin) = 0.5A,
under damped and reaches its steady – state voltage in about
Ripple in the output voltage (dVO) = 1.2V,
1.4 ms. The simulated output ripple voltage is about 0.75 V.
Ripple in the output current (dIO) = 0.03A,
The average output voltage is found to be 23.151V compared
Load resistance (R) = 20 ohm.
with the theoretical of 24V.
We get the value of parameters from equation (1) and (2) as:
Fig-6 shows the inductor voltage is a square wave while the
L=80µH
capacitor voltage is the same wave of the output waveform.
C=42µF
LC=62.5µH
Also the converter operates in continuous conduction mode as
L ˂ LC
4. SIMULATION RESULTS
LTspice IV version 4.23i 2016 simulation programs are used
to simulate the considered Boost switching converter. Fig-4
shows the Spice models of the Boost switching converter.
Fig-6: Simulated waveforms of the pulse width modulation
voltage, inductor voltage and capacitor voltage
Fig-4: Proposed model
Fig-7: Expand view of the inductor and capacitor currents
along with the switching pulses
Fig-5: Simulation waveforms of the output voltage, pulse
Fig-7 shows expand view of the input inductor and output
width modulation voltage and the input voltage
capacitor currents along with the switching pulses. The input
Fig-5 shows the simulation waveforms of the output voltage,
inductor current is under damped with maximum value of
pulse width modulation voltage and the input voltage of the
4.2A and minimum value of 0.6A with a ripple current of 3.6A
simulated Boost converter. It can be noted that the simulated
and therefore the percentage error with the theoretical results
waveforms are similar to each other and consistent with the
are very small.
VOLUME-3, ISSUE-7, JUL-2016
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INTERNATIONAL JOURNAL FOR RESEARCH IN EMERGING SCIENCE AND TECHNOLOGY, VOLUME-3, ISSUE-7, JUL-2016
Fig-8 shows the waveforms of current passing through
3.
E-ISSN: 2349-761
CONCLUSIONS
inductor, capacitor, diode (Id), and output current (Io). It can
In this paper, the analysis and simulations of 12v/24v Boost
be noted that the output current reaches its steady state value
switching converter is presented. The converter performance
of 1.156A after 1.5ms and has a very small ripple of 0.036A.
such as load voltage, capacitor and inductor currents, voltages
and currents ripples, etc. are analyzed and derived theoretically
under continuous operation. The design of the converter is
performed to step-up the input voltage 12v to an output
voltage of 24v. LTspice IV programs are used to simulate the
switching converter using a very high speed MOSFET as a
switch with 20 KHZ switching frequency. The simulated
waveforms are consistent with the theoretical waveforms and
the percentage error between simulated and theoretical results
is found to be very small.
REFERENCES
[1]
Linear Technology. LTSpice IV.
[2]
http://www.linear.com/designtools/software/
[3]
Ned Mohan, Tore M. Undeland, William P. Robbins,
―Power Electronics: Converters, Applications, and
Design‖, 3rd Edition, Wiley.
Fig-8: Simulated waveforms of current passing through
[4]
inductor, capacitor, diode and output current
Rashid, M. H. (Ed), (2007): Power Electronics
Handbook: Devices, Circuits, and Applications.
A comparison between the theoretical and simulation results is
shown in Table-1.
Florida: Elsevier Inc.
[5]
TABLE-1
Mohammed Abdulla Abdulsada, ―Analysis, Design
and
Parameters
Theoretical
Simulation
Input Voltage
12V
12V
PWM Voltage
5V
5V
Output Voltage
24V
23.13V
Ripple in Output
Voltage
1.2V
1.09V
Simulation
Switching
of
Converter‖,
12v/24v
International
Boost
Journal
of
Engineering Sciences & Research Technology,
Volume 3, no. 6, June 2014, pp. 836-846.
[6]
Christophe P. Basso, ―Switch-Mode Power Supplies
Spice Simulations and Practical Designs‖, McGrawHill companies, USA, 2008.
Ripple in Inductor
Current
3.75A
3.702A
Maximum
Inductor Current
4.25A
4.142A
Minimum
Inductor Current
0.5A
0.44A
Output Current
1.2A
1.156A
Ripple in Output
Current
0.03A
0.036A
[7]
Wikipedia, the Free Encyclopedia, ―Boost Converter
(online),
Available
from
http://en.wikipedia.org/wiki/Boost converter‖.
[8]
Shafinaz A. Lopa1, S. Hossain, M. K. Hasan and T.
K. Chakraborty, ―Design and Simulation of DC-DC
Converters‖,
International
Research
Journal
of
Engineering and Technology (IRJET), Volume 3
Issue 1, Jan-2016, pp. 63-70.
Table-1: Comparison between Theoretical and Simulation
results
VOLUME-3, ISSUE-7, JUL-2016
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