Aerospace and Electronic Systems Magazine March 2017 - 30

Feature Article:

DOI. No. 10.1109/MAES.2017.150261

Design and Implementation of Closed-Loop Control
System for Buck Converter Using Different Techniques
Magdy Saoudi, Ahmed El-Sayed, Hamid Metwally, Zagazig University, Zagazig, Egypt

INTRODUCTION
Comparing between different techniques for the design and implementation of closed-loop control systems for buck converters is
carried out. Controllers used for this comparison are integral, proportional plus integral (PI) controllers and artificial intelligence are
represented in fuzzy logic controller (FLC) and tuned fuzzy logic
controller (TFLC). Design and implementation of a control system
demand the role of effective techniques that offer simple and pragmatic solutions in society to meet the performance requirements
despite system disturbances and uncertainties [1]. The occurrence
of nonlinear phenomena in buck converters makes their analysis
and control difficult [2]. Classical linear techniques have stability
limitations around the operating points [1]-[3]. Hence digital and
nonlinear stabilizing control methods must be applied to ensure
large-signal stability [3]. Fuzzy control has also been employed
to control buck converters because of its simplicity, simplicity of
design and simplicity of implementation [4], [5]-[10]. Fuzzy controllers are easily suited to nonlinear time-variant systems and do
not require an accurate mathematical model for the system being
controlled. They are usually designed based on expert knowledge
of the converters [5]. In this survey, the design procedures of integral, proportional plus integral, fuzzy logic, and tuned fuzzy logic
controllers are presented.

DISCUSSION
MATHEMATICAL MODEL OF BUCK CONVERTER
The buck converter has an output voltage that is lower than the
input voltage. Figure 1 shows the buck converter with a voltage
controller and here it is assumed that all components are ideal and
the load consists of a resistor with resistance R. The converter has
an output low-pass filter consisting of an inductor with induc-

Table 1.

The Proposed Buck Converter Parameters

THE PROPOSED BUCK CONVERTER
The buck converter topologies with parameters are given in Table
1. These parameters have been obtained through trial and error
that verify equation vout/vg=0.5 when the value of the duty cycle is
50% to illustrate the result of each controller type on this converter performance. The proposed controller design procedures can
be generally applied to any buck converter topology for stability
enhancement, and output voltage regulation over a wide range of
operating conditions. The effect of the on-line changes of referAuthors' current address: M. Saoudi, H. Metwally, Electrical Power and Machines, Zagazig University, Sharkia, 44762
Egypt; A. El-Sayed, Engineering Management, Zagazig University, Sharkia, 44762 Egypt. E-mail: (eng_ahm_2014@yahoo.
com).
Manuscript received November 26, 2015, revised March 21,
2016, May 16, 2016, and ready for publication May 22, 2016.
Review handled by H. Liu.
0885/8985/17/$26.00 © 2017 IEEE
30

ence voltage on the output voltage regulation is discussed. In the
case of integral and proportional plus integral controllers, values
of integral gain (Ki) for the integral controller and proportional
and integral gains (Kp&Ki) for the PI controller are determined
from MATLAB. Then these gains are used in mikroC and Proteus
programs for buck converter design. In the case of fuzzy logic,
the controller determines the operating condition from the measured values and takes the appropriate control actions using the
rule base created from the expert knowledge. In the case of tunes,
the FLC uses a proportional plus integral and derivative (PID)
controller for tuning the output of FLC to improve the output
voltage configuration.

Variable

Parameter

Value

Vg(V)

Source input
voltage

Fs(KHz)

Switching
frequency

L(mH)

Magnetizing
inductance

C(μF)

Output filter
capacitance

100

Rc(mΩ)

Equivalent
series
resistance
(ESR) of
capacitor

R(Ω)

Load resistance

IEEE A&E SYSTEMS MAGAZINE

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MARCH 2017

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