Modeling approaches for dc–dc converters with switched capacitors

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IEEE SOFTWARE | EMBEDDED | MECHANICAL | ROBOTICS PROJECTS DEVELOPMENT
MODELING APPROACHES FOR DC–DC CONVERTERS WITH SWITCHED
CAPACITORS
By
A
PROJECT REPORT
Submitted to the Department of electronics & communication Engineering in the
FACULTY OF ENGINEERING & TECHNOLOGY
In partial fulfillment of the requirements for the award of the degree
Of
MASTER OF TECHNOLOGY
IN
ELECTRONICS & COMMUNICATION ENGINEERING
APRIL 2016

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CERTIFICATE
Certified that this project report titled “MODELING APPROACHES FOR DC–DC
CONVERTERS WITH SWITCHED CAPACITORS” is the bonafide work of Mr.
_____________Who carried out the research under my supervision Certified further, that to the
best of my knowledge the work reported herein does not form part of any other project report or
dissertation on the basis of which a degree or award was conferred on an earlier occasion on this
or any other candidate.
Signature of the Guide Signature of the H.O.D
Name Name

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DECLARATION
I hereby declare that the project work entitled “MODELING APPROACHES FOR DC–DC
CONVERTERS WITH SWITCHED CAPACITORS” Submitted to BHARATHIDASAN
UNIVERSITY in partial fulfillment of the requirement for the award of the Degree of MASTER
OF APPLIED ELECTRONICS is a record of original work done by me the guidance of
Prof.A.Vinayagam M.Sc., M.Phil., M.E., to the best of my knowledge, the work reported here
is not a part of any other thesis or work on the basis of which a degree or award was conferred on
an earlier occasion to me or any other candidate.
(Student Name)
(Reg.No)
Place:
Date:
ACKNOWLEDGEMENT

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I am extremely glad to present my project “MODELING APPROACHES FOR DC–DC
CONVERTERS WITH SWITCHED CAPACITORS” which is a part of my curriculum of
third semester Master of Science in Computer science. I take this opportunity to express my
sincere gratitude to those who helped me in bringing out this project work.
I would like to express my Director, Dr. K. ANANDAN, M.A.(Eco.), M.Ed., M.Phil.,(Edn.),
PGDCA., CGT., M.A.(Psy.) of who had given me an opportunity to undertake this project.
I am highly indebted to Co-Ordinator Prof. Muniappan Department of Physics and thank from
my deep heart for her valuable comments I received through my project.
I wish to express my deep sense of gratitude to my guide
Prof. A.Vinayagam M.Sc., M.Phil., M.E., for her immense help and encouragement for
successful completion of this project.
I also express my sincere thanks to the all the staff members of Computer science for their kind
advice.
And last, but not the least, I express my deep gratitude to my parents and friends for their
encouragement and support throughout the project.

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ABSTRACT:
Traditional linear techniques are widely used for the control of basic dc–dc converters
due to their simple implementation. However, due to the small-signal validity range of the
models employed, the converters usually perform poorly under large transients, and the dynamic
response can be improved only to a limited extent in order to ensure a stable behavior. On the
other hand, faster dynamic response can be achieved with boundary controllers, which require
faster sensors and more powerful processors. A novel control scheme that combines the
advantages of fixed-frequency pulsewidth modulation with state-plane geometric analysis is
introduced to obtain fast and reliable large-signal response. The natural evolution of the average
state variables is described by a large-signal unified model, which provides the basis to develop a
reliable nonlinear control scheme. The proposed technique is suitable for implementation in low-
cost digital signal processors, using low-bandwidth sensing stages, and it features fast, sleek, and
consistent dynamic response with constant switching frequency

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INTRODUCTION:
Switched capacitor (SC) converters offer several advantages such as light weight, small
size, high power density, and large voltage conversion ratios, which are important for a large
number of applications. For these reasons, increased interest has been given to their design,
modeling, and control.
Many control techniques for power converters are based on nonlinear models; see, for
instance, the extensive compendium of control techniques presented. Such models and,
consequently, their associated nonlinear controllers are able to perform well in wide ranges of
operation compared with linearized models.
However, the conventional approach for the regulation of SC-based converters is a linear
feedback control that is based on approximate small signal linearized models of the circuit
topologies. In some applications, this approach does not make the converters able to respond
well to requirements of regulation in the presence of a wide range of input voltages and load
variations.
Several linear and mixed approaches have been taken in order to achieve an enhanced
dynamic response in basic dc–dc topologies while ensuring a robust behavior. Although very
interesting results have been obtained, the complexity in the implementation is often increased,
and the solutions may not be suitable for cost-sensitive applications.
Nonlinear geometric-based approaches present an appealing alternative in which the
control decisions are based purely on the system operating point. First-order switching surface
controllers have been reported, which provide a reliable response once the sliding mode is
reached.

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Some of the issues involved in the implementation of this technique are: large current
spikes before sliding mode is reached, steadystate error, chattering, and variable switching
frequency . Although successful attempts to solve most of these issues have been presented, the
simplicity of the original concepts is compromised

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EXISTING SYSTEM:
Different approaches have been proposed for the modeling of SC converters, such as
incremental graph approaches, useful for determining steady-state voltage gains. Approaches for
modeling SC are given by considering the inherent losses produced when capacitors are
connected in parallel. A steady-state modeling approach is provided in which SC converters are
analyzed by considering equivalent output impedances.

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PROPOSED SYSTEM:
In this paper, we gather and discuss theory and principles regarding the operation of SC
converters. Moreover, we present a systematic exposition of three modeling approaches for dc–
dc converters with SCs. The procedures are illustrated using a Fibonacci SC converter and the
three switch high-voltage converter. The methods are similar to the classical averaging
techniques that consider equivalent circuits depending on the position of the switches. However,
instead of using the real equivalent series resistor (ESR) lumped in the circuit, we consider the
following: 1) the case with ideal switches where discontinuous signals are allowed; 2) an average
loss modeling based on the results provided; and 3) a reduced-order model based on a voltage-
balancing property

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ADVANTAGES:

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BLOCK DIAGRAM:

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TOOLS AND SOFTWARE USED:
 MPLAB – microcontroller programming.
 ORCAD – circuit layout.
 MATLAB/Simulink – Simulation

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APPLICATIONS:

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CONCLUSION:
A novel PWM-based geometric control scheme was proposed in this paper for the three
basic dc–dc topologies. The three main objectives stated for the proposed control technique are:
to obtain a reliable and consistent transient response, with an enhanced dynamic regulation, and a
simple implementation. These objectives were accomplished by developing a highperformance
low-complexity control scheme, based on an average model (ANTs) that describes the
converters’ large-signal behavior in an intuitive geometric domain. The control decisions are
based in the state-variable location in the geometric plane, which allows a sharp control of
trajectories described by the operating point ensuring reliable behavior. Improvements to the
dynamic regulation are obtained by allowing duty-cycle saturations only for a well-determined
period of time, avoiding large spikes in the inductor current and capacitor voltage. Due to the
average nature of the ANTs, the controller is suitable for implementation in low-cost DSPs using
fixed-frequency PWM, and the bandwidth required for sensing stages is maintained low.
Furthermore, due to the normalized approach adopted, the controller can be implemented for any
combination of LC parameters and input/output voltages maintaining the fast, sleek, and reliable
dynamic response.

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REFERENCES:
[1] J. Abu Qahouq and V. Arikatla, “Online closed-loop autotuning digital controller for
switching power converters,” IEEE Trans. Ind. Electron., vol. 60, no. 5, pp. 1747–1758, May
2013.
[2] M. Peretz and S. Ben-Yaakov, “Time-domain design of digital compensators for PWM DC–
DC converters,” IEEE Trans. Power Electron., vol. 27, no. 1, pp. 284–293, Jan. 2012.
[3] S. Kapat and P. Krein, “Formulation of PID control for DC–DC converters based on
capacitor current: A geometric context,” IEEE Trans. Power Electron., vol. 27, no. 3, pp. 1424–
1432, Mar. 2012.
[4] Y.-C. Lin, D. Chen, Y.-T. Wang, and W.-H. Chang, “A novel loop gainadjusting application
using LSB tuning for digitally controlled DC–DC power converters,” IEEE Trans. Ind. Electron.,
vol. 59, no. 2, pp. 904– 911, Feb. 2012.
[5] A. Oliva, S. Ang, and G. Bortolotto, “Digital control of a voltage-mode synchronous buck
converter,” IEEE Trans. Power Electron., vol. 21, no. 1, pp. 157–163, Jan. 2006.

Modeling approaches for dc–dc converters with switched capacitors

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Modeling approaches for dc–dc converters with switched capacitors