International Journal of Emerging Technology in Computer Science & Electronics (IJETCSE)
ISSN: 0976-1353 Volume 13 Issue 2 –MARCH 2015.
Improved Performance of a Single Stage Voltage
Power Factor Correction Converter for LED Lamp
Driver
R.Kannan
Final year M.Tech
Kansel1410@gmail.com
S.Thamizharasi
R.Sivakumar
Assistant Professor
thamizh9490@gmail.com
Assistant Professor
avisramuk24988@gmail.com
Electrical Drives and Control
Department of Electrical and Electronics Engineering
Dr.S.J.S.Paul Memorial College of Engineering &Technology, Puducherry.
Abstract: Recent developments in LEDs permit them to be used
in environmental and task lighting. LED lamp need controlled
direct current electrical Power, an appropriate circuit is required
to convert alternating current from the supply to the regulated
low voltage direct current used by the LEDs. So a power
converter is required to control the operation of LED lamp.
Power converters involve diode rectifiers with large capacitor to
reduce DC voltage ripple. The filter capacitor reduces the ripple
present in the output voltage but draw non-sinusoidal line
current which reduces the power factor. This paper deals with a
power factor corrected (PFC) improved power quality based
LED lamp driver. The proposed driver consists of a PFC Boost
converter using Fuzzy logic controller which operates in
continuous conduction mode with output voltage regulation. A
new fuzzy logic control strategy for boost PFC is presented in
this paper. Here the controlling action was established through a
fuzzy Logic controller. The proposed Fuzzy Logic control system
is a two input one output Fuzzy Logic Controller. The proposed
PFC control is derived based on Boost converter operates at
continuous conduction mode and the switching frequency is
much higher than the line frequency. This Proposed system is
validated through MATLAB/SIMULINK platform.
Keywords: Power factor correction, Total harmonic distortion,
Boost converter, Fuzzy logic control, continuous conduction mode.
I.INTRODUCTION
As light-emitting diodes (LEDs) have many advantages such
as small size, high luminous efficiency, long lifetime, fast
response, and excellent color rendering, they have been
widely used in many lighting applications. LEDs are
environmentally friendly devices compared with conventional
fluorescent lamps that require mercury and may produce
pollution. Therefore, in pursuit of energy-saving and pollution
free light sources, LEDs have gradually replaced fluorescent
lamps and have become increasingly and more widely used
[1-4].
LEDs are operated from a low voltage DC supply. In
general lighting applications, the LED lamps have to operate
from universal AC input, so an AC–DC converter is needed to
drive the LED lamp [5]. The efficient drive not only performs
unity power factor (PF), but also regulates LED current [6].
The rectifier with filter capacitor is called a conventional AC–
DC utility interface. Although a filter capacitor significantly
suppresses the ripples from the output voltage, it introduces
distortions in the input current and draws current from the
supply discontinuously, in short pulses [7]. This introduces
several problems including reduction in available power, and
the line current becomes non-sinusoidal which increases the
total harmonic distortion (THD) and increases losses. This
results in a poor power quality, voltage distortion, and poor PF
at input ac mains [8–9]. With the development of PFC
converters, a sinusoidal line current can be made in phase with
the line voltage, and this PFC circuit achieves the
requirements of the international harmonic standards. For all
lighting products and input power higher than 25 W, AC–DC
LED drivers must comply with line current harmonic limit set
by IEC61000-3-2 class C [10]. Single- stage PFC topologies
are the most suitable converters for lighting applications, as
PFC and regulator circuits can be merged together. They have
high efficiency, a near unity PF, simple control loop, and a
small size. In reality, the switching frequency is much higher
than the line frequency, and the input AC current waveform is
dependent on the type of control being used [11]. The inductor
is assumed to be operated in continuous conduction mode
(CCM) which is implemented using hysteresis current control
method. In this paper, a power factor corrected (PFC) AC-DC
Boost converter operating in CCM (Continuous Conduction
Mode) is proposed for LED driver. In solid state LED driver,
power factor corrected (PFC) AC-DC converter improves the
input power facto and reduces total harmonic distortion of AC
mains current (THD) and also maintains constant lamp
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International Journal of Emerging Technology in Computer Science & Electronics (IJETCSE)
ISSN: 0976-1353 Volume 13 Issue 2 –MARCH 2015.
voltage for the stable operation of LED lamp. Since PFC
converter is operated at high switching frequency, it reduces
the size and weight of passive components like inductor and
capacitor.
II. NECESSITY OF POWER FACTOR IMPROVEMENT
Power Factor vs. Harmonic Reduction:
Power factor is a figure of merit that measures how
effectively power is transmitted between a source and load
network. It always has a value between zero and one. The
unity power factor condition occurs when the voltage and
current waveforms have the same shape, and are in phase.
Power factor is defined as the cosine of the angle between
voltage and current in an ac circuit. If the circuit is inductive,
the current lags behind the voltage and power factor is
referred to as lagging. However, in a capacitive circuit, current
leads the voltage and the power factor is said to be leading.
Power factor can also be defined as the ratio of active power
to the apparent power .The active power is the power which is
actually dissipated in the circuit resistance. The reactive
power is developed in the inductive reactance of the circuit.
Power factor = (Active power)/ (Apparent power)
(1)
A load with a low power factor draws more current than a
load with a high power factor for the same amount of useful
power transferred. The higher currents increase the energy
lost. So power factor improvement is required
Assuming an ideal sinusoidal input voltage source, the
Power factor can be expressed as the product of the distortion
factor and the displacement factor, as given by equation (3).
The distortion factor Kd, is the ratio of the fundamental root
mean- square (RMS) current (Irms(1)) to the total RMS
current (Irms). The displacement factor KΦ is the cosine of the
displacement angle (φ) between the fundamental input current
and the input voltage. For sinusoidal voltage and non
sinusoidal current, equation (1) can be expressed as:
P.F =
∅
=
cosΦ = kd cosΦ
P.F = Kd kΦ
(2)
(3)
The distortion factor Kd is given by the following equation:
Kd = I rms (1) / I rms
(4)
The displacement factor KΦ is given by the following
Equation:
KΦ = cos φ
factor, it means that the converter absorbs apparent power
higher than the active power. This means that the power
source has a higher VA rating than what the load needs. In
addition, the harmonic currents generated by the converter in
the power source affects other equipment[12]
(5)
The displacement factor KΦ can be made unity with a
capacitor or inductor, but making the distortion factor Kd unity
is more difficult. When a converter has less than unity power
The following equations link total harmonic distortion to
power factor.
THD (%) = 100×
Kd =
(%)
− 1
(6)
(7)
²
Therefore, when the fundamental component of the input
current is in phase with the input voltage, KΦ = 1. Then we
have,
PF = Kd KΦ = Kd
Then
P.F =
(%)
²
(8)
(9)
The purpose of the power factor correction circuit is to
minimize the input current distortion and make the current in
phase with the voltage. When the power factor is not equal to
1, the current waveform does not follow the voltage
waveform. This result not only in power losses, but may also
cause harmonics that travel down the neutral line and disrupt
other devices connected to the line.
III.POWER FACTOR CORRECTION TECHNIQUE
The single-phase diode rectifier associated with the boost
converter, as shown in Fig. 1(d), is widely employed in active
PFC. In principle, the combination of the diode bridge
rectifier and a dc-dc converter with filtering and energy
storage elements can be extended to other topologies, such as
buck, buck-boost, and Cuk converter [13]. The boost topology
is very simple and allows low-distorted input currents, with
almost unity power factor using different dedicated control
techniques. Typical strategies are hysteresis control, average
current mode control and peak current control [14]. More
recently, one cycle control and self control have also been
employed.
Some strategies employed three levels PWM AC/DC
converter to compensate the current harmonics generated by
the diode rectifier. Some strategies employed active power
filter to compensate the harmonic current generated by the
non-linear load. Disadvantages of these strategies are; (a) for
each nonlinear load, one separate converter should be
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International Journal of Emerging Technology in Computer Science & Electronics (IJETCSE)
ISSN: 0976-1353 Volume 13 Issue 2 –MARCH 2015.
employed, (b) due to presence of more switching devices used
in some strategies, switching losses occurs is more, as the
switching losses depend upon the no of switching devices
(c) some strategies use very complex control algorithm. To
overcome all these type of problems, a new power factor
correction technique using PFC boost converter is proposed.
IV.PROPOSED POWER FACTOR CORRECTION
TECHNIQUE
One of topologies most commonly used to deal with this
problem so is called single phase boost converter. The
simplified boost converter circuit is shown in figure 2.
The boost inductor in the boost converter circuit is in series
with the ac power line. This topology inherently accepts a
wide input voltage range without an input voltage selector
switch. The equivalent circuits of the system are derived based
on the “on” and “off” states of the converter switch and shown
in figure 2-a and figure 2-b respectively.
Fig (1) shows the block diagram of PFC Boost converter
with fuzzy logic controller. In this technique two control loops
are used outer loop is voltage that tracks the output voltage
while inner loop is current loop that tracks the inductor
current.
Figure 2(a).on state switching
AC
Input
Diode
Bridge
Rectifier
Boost
Converter
Circuit
LED
String
VO
Vin
IL
HCC/AMCC
Pulse
Generator
+/-
Figure 2(b) .off state switching
The output voltage of a boost converter should be higher
than the peak value of the maximum input voltage. Only the
single–phase boost converter circuit operating in the
continuous conduction mode is discussed with hysteresis
control techniques in this study.
Ref
voltage
Fuzzy logic
Controller
B. Hysteresis Current mode control technique
Figure 1.Block diagram for proposed system
A. Boost converter
There are different topologies used in PFC converters. The
topology used in this study, is an ac-dc boost converter. Many
applications require an ac-dc conversion from the line voltage.
In its most simple form, this conversion is performed by
means of a bridge rectifier and a bulk capacitor. The bulk
capacitor filters the rectified voltage and provides certain
energy storage in case of a line failure. But resultant line
current pulsates, causing a low power factor due to its
harmonics and its displacement with respect to the line
voltage. In many applications, this low quality in the power
usage is not acceptable above certain power levels, and the
corresponding standards require improved technical solutions.
HCMC techniques has the constant on-time and the
constant–off time control, in which only one current command
is used to limit either the minimum input current or the
maximum input current [15-17]. A simple diagram of a typical
hysteresis current controller is shown in Fig.3.
151
(a). Functional diagram
International Journal of Emerging Technology in Computer Science & Electronics (IJETCSE)
ISSN: 0976-1353 Volume 13 Issue 2 –MARCH 2015.
Figure 2
boost
Input voltage (VDC)
Output voltage (VO)
Duty Ratio (D)
Inductor (L)
Capacitance(C)
Load Resistor (R)
Switching Frequency
24V
60V
0.6
3mH
3000µF
1500 Ω
28Khz
Table I
Simulation parameter of boost converter
.Basic
converter
V. INTRODUCTION TO FUZZY LOGIC
CONTROLLER
(b). Current and PWM waveforms
Figure 3. General hysteresis current control scheme
The boost inductor current is continuously compared with
the reference current waveform (which is obtained from the
voltage control loop) and the error signal (after amplification)
is fed into a hysteresis comparator. When the actual inductor
current goes above the reference current by the comparator
hysteresis band, the comparator change its state to switch off
the boost switch and the current ramp goes down. When the
actual current goes below the reference current by the
comparator hysteresis band, it changes state again and turns
the boost switch on. Thus, the inductor current is always
maintained within ±H, where 2H is the total hysteresis band.
L. A. Zadeh presented the first paper on fuzzy set theory in
1965. Since then, a new language was developed to describe
the fuzzy properties of reality, which are very difficult and
sometime even impossible to be described using conventional
methods. Fuzzy set theory has been widely used in the control
area with some application to dc-to-dc converter system. A
definitions and the control rule set; a decision-making logic
which, simulating a human decision process, infer the fuzzy
control action from the knowledge of the control rules and
linguistic variable definitions; a defuzzification interface
which yields non fuzzy control action from an inferred fuzzy
control action [18].
C. Design consideration
If output voltage is represented as Vo and input voltage is
represented as VDC, the duty ratio (D) of a typical boost
converter is given by
D=
(10)
The inductor can be designed using the equation (11)
L=
!.# ( $#)%
%&
Figure 4. General structure of the fuzzy logic controller on
closed-loop system
(11)
Where f – switching frequency and R- Load resistance.
The value of capacitance is given by
C=
.#
&∆ .!
Where ∆V is output voltage ripple.
(12)
The fuzzy control systems are based on expert knowledge
that converts the human linguistic concepts into an automatic
control strategy without any complicated mathematical model
[19]. Simulation is performed in buck converter to verify the
proposed fuzzy logic controllers.
A. Fuzzy Logic Membership Functions:
The ac-dc converter is a nonlinear function of the duty cycle
because of the small signal model and its control method was
applied to the control of boost converters. Fuzzy controllers
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International Journal of Emerging Technology in Computer Science & Electronics (IJETCSE)
ISSN: 0976-1353 Volume 13 Issue 2 –MARCH 2015.
do not require an exact mathematical model. Instead, they are
designed based on general knowledge of the plant. Fuzzy
controllers are designed to adapt to varying operating points.
Fuzzy Logic Controller is designed to control the output of
boost ac-dc converter using Mamdani style fuzzy inference
system. Two input variables, error (e) and change of error (de)
are used in this fuzzy logic system. The single output variable
(u) is duty cycle of PWM output.
Negative Big, NS: Negative Small, ZO: Zero Area, PS:
Positive small and PB: Positive Big and its parameter [10].
These fuzzy control rules for error and change of error can be
referred in the table that is shown in Table II as per below:
Table II
Table rules for error and change of error
Figure 5.The Membership Function plots of error
e/Ce NB
NM
NS
Z
PS
PM
PB
NB
NB
NB
NB
NB
NM
NS
Z
NM
NB
NB
NB
NM
NS
Z
PS
NS
NB
NB
NM
NS
Z
PS
PM
Z
NB
NM
NS
Z
PS
PM
PB
PS
NM
NS
Z
PS
PM
PB
PB
PM
NS
Z
PS
PM
PB
PB
PB
PB
Z
PS
PM
PB
PB
PB
PB
VI. SIMULATION RESULT AND DISCUSSION
Case 1 Boost converter with conventional PI controller:
The simulation of the power factor correction converter is
done using PI controller and various parameters are analyzed.
The PI controller is manually tuned. Fig 8 shows the
Matlap/simulink Model of Boost converter with conventional
PI controller
Figure 6. The Membership Function plots of change error
Figure 7. The Membership Function plots of duty ratio
B. Fuzzy Logic Rules:
The objective of this dissertation is to control the output
voltage of the boost converter. The error and change of error
of the output voltage will be the inputs of fuzzy logic
controller. These 2 inputs are divided into five groups; NB:
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International Journal of Emerging Technology in Computer Science & Electronics (IJETCSE)
ISSN: 0976-1353 Volume 13 Issue 2 –MARCH 2015.
Figure 10. Output voltage wave form
As above fig 9 shows the input voltage and input current of
boost converter with conventional PI controller. Fig 10 shows
output voltage of the boost converter with conventional PI
controller
Figure 8. Matlap/simulink Model of Boost converter with
conventional PI controller
Figure 11. THD Analysis of source current with boost
converter using conventional PI controller
Fig 11 shows the FET Analysis of source current with
Boost converter using Conventional PI controller, we get
5.25%.
Case 2 Proposed Boost Converter with Fuzzy Logic
Controller
Figure 12 shows the Matlap/Simulink Model of Proposed
Boost Converter with Fuzzy Logic Controller.
Figure 9. Input voltage and current wave form
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International Journal of Emerging Technology in Computer Science & Electronics (IJETCSE)
ISSN: 0976-1353 Volume 13 Issue 2 –MARCH 2015.
The output voltage and the current waveform shown if Fig 14
shows that the voltage and current gets controlled nearer to the
reference value using the fuzzy controller.
Figure 12. Matlap/Simulink Model of Proposed Boost
Converter with Fuzzy Controller
Figure 15. THD Analysis of source current with Proposed
Boost Converter Using Fuzzy Logic Controller
Fig 15 Shows the FET Analysis of Source Current with
Proposed Boost converter using Fuzzy Logic Controller, we
get 4.81%.
VI CONCLUSION
Figure 13. Input voltage and Input current wave form
A variety of circuit topologies and control methods have been
developed for the PFC application. Here presented one new
and interesting AC/DC boost-type converters for PFC
applications with conventional & Intelligence controller.
Without using any dedicated converter, one converter can be
used to eliminate the harmonic current generated by the other
non-linear load. With the help of simulation study, it can be
concluded that, this configuration removes almost all lower
order harmonics, hence with this configuration we can achieve
power factor nearer to unity, THD less than 5%, using Fuzzy
controller we get fast dynamic response. However, this
technique can be limited to application where the non-linear
load (pulsating) current is less and fixed. THD Analysis of
both controllers well within IEEE Standards
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Figure 14. Output current and Output voltage wave form
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