International Journal of Research Science and Engineering (ISSN: 2212 4012) Volume 4 –Issue.9,
September 2015
SIMULATION AND IMPLEMENTATION OF BUCK CONVERTER WITH TAPPED
INDUCTOR
S.Veeramani #1, S.K.Subramanian #2, Mr.Nirmalraj M.E
#1 Bachelor of Engineering, #2 Bachelor of Engineering #3 Assistant Professor
Department of Electrical & Electronics Engineering,
Sathyabama University,Chennai Tamil Nadu,India
veera_om82@yahoo.co.in, subbu.race@gmail.com
ABSTRACT
Tapped-inductor buck converters allow great improvements in the performance of 12V-input
voltage regulator modules (VRMs). A novel digital adaptive voltage positioning (digital AVP)
technique with dual-voltage-loop was proposed. Good transient performance had been achieved
without using complicated control. The stepping inductance method is implemented by replacing
the conventional inductor in a buck converter by two inductors between in series. One has large
inductance and the other has small inductance. The inductor with small inductance will take over the
output inductor during transient load change and speed up dynamic response. Tapped-inductor buck
converters can provide large step-down ratios at high efficiency and are well suited in support
power supplies for modular multilevel converter cells supplying gate drive units etc. The output
inductor of the conventional buck converter is replaced by a tapped inductor and an auxiliary
switch to achieve fast transient response. Usually, the proposed converter works as a
conservative buck converter with very large output inductance during the steady state to reduce
the output current ripple. Once the transient load change appears, the auxiliary switch is turned
ON in order to speed up the dynamic process by plummeting the equivalent output
inductance.A10-V output voltage buck converter with maximum 30-A output current has been
built and tested. The experimental results demonstrated the effectiveness of the proposed
converter, which also means that the proposed arrangement shows great possible for fast fleeting
comeback voltage regulator applications.
Keywords: Buck converter, fast transient, tapped inductor, voltage regulator
converters share the load current equally and
INTRODUCTION
stably. Parallel modules are usually
Generally, the paralleling of power
nonidentical due to finite tolerances in the
converter modules offers a number of
power stage and control parameters. If
advantages over a single, high-power,
special provisions are not made to distribute
centralized power supply. Paralleling of
the load current equally among paralleling
standardized converter modules is an
modules, then it is possible that one or more
approach that is used widely in distributed
units may have an excessive load current.
power systems for both front-end and load
This causes higher thermal stress on specific
converters. A desirable characteristic of a
units and reduces the system reliability.
parallel supply system is that individual
International Journal of Research Science and Engineering (ISSN: 2212 4012) Volume 4 –Issue.9,
September 2015
Advance in electronic systems demand
corresponding advances in power supply
technology. Power supplies must be
increasingly reliable and efficient, and
power density requirements are increasing
as well. In particular, advances in computer
technology require increasing currents at
lower
voltages.
Single
high-current
converters have problems such as heat
dissipation,
expensive
high-power
components and failure protection circuits.
A better method of meeting these demands
is to employ several individual converters
that share the load requirements; hence, the
topic of multiple module power supply
(MMPS) systems is currently of great
interest. Modular power systems have many
desirable properties.
First, the thermal design of high-current,
low-voltage systems is simplified, since one
may use multiple low-power converters in
parallel to meet the total power requirements
of a given system. Second, changes in power
specification can be met with changes in the
number of modules, rather than the design of
a new converter. Third, MMPSs can be
useful in high reliability systems. The
redundancy possible with multiple converter
modules provides greater system reliability,
since an individual module failure does not
mean a system failure. The repair of such
systems is simplified since on-line
replacement of faulty modules is possible.
Also, since individual converters handle
low-power levels, component stresses are
low and converter life is lengthened.
RELETED WORKS
In [1] Zhihong Ye, Ray-Lee Lin and Fred C.
Lee et al presents, Paralleling of
standardized converter modules is an
approach that is used widely in distributed
power systems for both front-end and load
converters. A desirable characteristic of a
parallel supply system is that individual
converters share the load current equally and
stably. Parallel modules are usually
nonidentical due to finite tolerances in the
power stage and control parameters. If
special provisions are not made to distribute
the load current equally among paralleling
modules, then it is possible that one or more
units may have an excessive load current.
In [2] Xunwei Zhou, PengXu, and Fred C.
Lee et al presents, Voltage Regulator
Module will need a large amount of extra
decoupling and output filter capacitors to
meet future requirements, which will
basically make the existing VRM topologies
impractical. As a candidate topology, the
interleaved quasi square-wave VRM
exhibits very good performance, such as a
fast transient response and a very high
power density. The difficulty with the
application of the interleaved parallel
technology is the current-sharing control. In
this paper, a novel current-sensing and
current-sharing technique is proposed. With
this technique, current sharing can be
controlled simply in parallel converters
without a current transformer and currentsensing resistors.
In [3] John S. Glaser, and Arthur F. Witulski
et al presents, The origin of the dc current
International Journal of Research Science and Engineering (ISSN: 2212 4012) Volume 4 –Issue.9,
September 2015
sharing problem of parallel-converter
systems and the dual problem of voltage
sharing in series-converter systems. Both
problems may be studied by examining the
output plane (output current versus output
voltage) of a particular converter. It is
shown that strict current source behavior is
unnecessary for good current sharing in
parallel-converter systems. Furthermore,
broad classes of converters whose output
voltage is load-dependent, i.e., those that
have a moderate value of output resistance,
all exhibit good voltage- and current-sharing
characteristics. Such converters are often
suitable for ax b arrays of converters that
can meet a large range of power-conversion
requirements.
In [5] Michael T. Zhang, Milan M.
Jovanovi´c,,and Fred C. Y. Lee et al
presents, Analysis, design, and evaluation of
different interleaving techniques for the
forward
converter
are
presented.
Specifically, the performance of the onechoke interleaving approach is compared
with the two-choke interleaving approach.
The results of the analysis are verified
experimentally on two 5-V/20-A interleaved
dc/dc converters. In addition to physically
distributing the magnetics and their power
losses and thermal stresses, paralleling also
distributes power losses and thermal stresses
of the semiconductors due to a smaller
power processed through the individual
paralleled power stages.
In [4] Oun Lee, Shin-Young Cho, and GunWoo Moon et al presents, A new interleaved
buck converter having low switching losses
and improved step-down conversion ratio,
which is suitable for the applications where
the input voltage is high and the operating
duty is below 50%. It is similar to the
conventional IBC, but two active switches
are connected in series and a coupling
capacitor is employed in the power path,
such as C´uk, Sepic, and Zeta converters.
The proposed IBC shows that since the
voltage stress across all the active switches
is half of the input voltage before turn-on or
after turn-off when the operating duty is
below 50%, the capacitive discharging and
switching
losses
can
be
reduced
considerably. This allows the proposed IBC
to have higher efficiency and operate with
higher switching frequency.
Interleaved multiple buck converters
The interleaved multiple buck converters are
very popular in high-current fast transient
applications. The interleaved operation
mode reduces the equivalent output inductor
of the dc–dc converters; hence, it shows
good dynamic performance during the
transient state. However, some issues still
remained such as the high conduction losses
and stresses causing by the large peak
current in each branch of the interleaved
multiple converter. A buck converter with
stepping inductance for fast transient
response can be found. With two extra small
MOSFETs and diodes added, the stepping
inductor converter is very suitable for fast
transient application. During the transient
state, the stepping inductor circuit works to
short circuit the output inductor by a
hysteresis controller. However, the control
International Journal of Research Science and Engineering (ISSN: 2212 4012) Volume 4 –Issue.9,
September 2015
strategies are relatively complicated
comparing with the one in the conventional
buck converter.
Buck converter with tapped converter
A buck converter with stepping inductance
for fast transient response can be found.
With two extra small MOSFETs and diodes
added, the stepping inductor converter is
very suitable for fast transient application.
During the transient state, the stepping
inductor circuit works to short circuit the
output inductor by a hysteresis controller.
However, the control strategies are relatively
complicated comparing with the one in the
conventional buck converter. The voltage
regulator buck converter with a tapped
inductor for fast transient response
applications is proposed in this letter. The
extra auxiliary switch was added to change
the equivalent output inductance. The
proposed converter was able to perform not
only fast transient response during the
transient state but also low current ripple at
the steady state. The prototype of a 300-W
buck converter is built and tested to verify
the effectiveness of the proposed adjustable
inductor and the corresponding fast transient
response.
Inductor prototypes
A first prototype was made with the high
and low voltage windings distributed in two
layers as shown in Fig
Fig 3 Tapped inductor winding layout, first
prototype. High-voltage winding (Np) in red
and low-voltage winding (Ns) in blue
It was anticipated that the leakage
inductance would be low as the radial
displacement of the windings was small. A
second prototype was made with high and
low voltage windings of equal axial length.
Also, a first order interleaving was utilized
to minimize the leakage inductance. The
insulation between the layers is made from
three layers of 65 μm polyimide film tape
which can withstand the electric field stress
and has excellent resistance to partial
discharge degradation. The film tape extends
approximately 4mm on each side of the
winding layers to provide sufficient creep
age distance.
Inductor characterization and testing
Figure 1 Buck Converter with Tapped
Inductor
The inductor magnetizing inductances and
leakage inductances were measured at 10
kHz and 1V using a WK TMPO 4230 LCRmeter. The leakage inductance was
measured by short circuiting one part of the
International Journal of Research Science and Engineering (ISSN: 2212 4012) Volume 4 –Issue.9,
September 2015
winding and measuring the inductance of the
other part.
Fig. 4. Tapped inductor winding layout,
second prototype. High-voltage winding
(Np) in red and low-voltage winding (Ns) in
blue
BLOCK DIAGRAM
Input
Supply
Step Down
Transformer
Rectifier
Voltage
Regulator
Microcontroller
Filter
Driver Circuit
Tapped
Inductor
Load
Auxiliary
Switch
Buck
Converter
Unit
Conventional
unit
Fig 2 Block Diagram
that the conversion has a very wide range of
variation as compared with before.
The intented application for the inductor is
tapped-inductor buck converters with
current injection which allows soft
switching of the main switch. The current
injection is achieved by allowing the current
in the synchronous rectifier reverse and
reaches a negative value before turning off.
At turn-off of the synchronous rectifier the
energy stored in the inductor will charge the
stray and snubber capacitors of the main
switch and, if sufficient energy is stored,
drive the voltage over the main switch to
zero, which allows a soft turn on. In cases
with non-negligible leakage inductance the
voltage over the synchronous rectifier can
reach destructive levels. The energy stored
in the leakage inductance must thus be
absorbed by the synchronous switch stray
and snubber capacitance to clamp the
voltage. The inductors were tested in a
boost-configuration circuit to evaluate the
effect of the leakage inductance. For the
switching test it is not necessary to use a
high voltage supply, instead only an
appropriately sized (150 pF) snubber
capacitor was connected between the
inductor high voltage lead and the negative
supply rail as shown in Fig
Tapped converter
The tapped converter of the classical
switched-mode power converter is an
extension of the conventional switched
mode power converters. Using the tapped
configuration, the control parameter of the
converter can be using tapping. It is found
Fig 5 Tapped Inductor Circuit
International Journal of Research Science and Engineering (ISSN: 2212 4012) Volume 4 –Issue.9,
September 2015
Basic buck topology
The basic topology consists of 4 components
which are active switching devices, diode,
inductor and output capacitor. The
nomenclature of transistor-tapped is referred
to the tapping of the inductor is connected to
the active devices. Similar definition is used
for the diode tapped and rail tapped.
For electronic and industrial equipment
requiring non−isolated, offline, low power
outputs, the simple buck converter appears
ideal; however, the large differential
input−to−output voltage can be problematic
in terms of very low converter duty cycle,
peak−to−average switching current ratios,
and overall conversion efficiency. This
application presents a solution that will
overcome many of these issues without
additional electronic circuitry. The solution
involves a modification to the buck inductor
in which a tap is added to the winding and
the buck freewheeling diode is connected to
the tap.
Tapped inductor buck converter topology
The dynamic response of the dc–dc
converters is also required to maintain the
output voltage constant at the presence of
variations or fluctuations in the load current.
To characterize this feature, we should
investigate the closed-loop transfer function
from the load current to output voltage (also
named output impedance). As the output
impedance becomes smaller, the dc– dc
converter resembles an ideal voltage source
more closely. The output impedance starts
with a very small magnitude at low
frequencies and gradually increases until it
approaches a constant value at high
frequencies determined by the ESR of the
output capacitor.
A vital component in this converter is the
tapped inductor itself. From circuit
simulations and preliminary experiments it
was found that the leakage inductance of the
tapped inductor should be minimized in
order to optimize the efficiency of the
converter. As will be shown below, design
of such an inductor is not trivial. It is the
intention of this paper to describe the design
process of such an inductor and to build and
evaluate a first series of prototypes. Both the
design process and the evaluation focus on
the minimization of the leakage inductance,
and it is experimentally verified that leakage
inductances of the order of 0.8 percent are
achievable.
Tapped-inductor buck converter
Fig 6 Tapped Inductor buck converter
topology
The tapped-inductor buck converter is one
of the simplest topologies with an extended
duty cycle. The biggest advantage of the
tapped inductor buck converter over other
International Journal of Research Science and Engineering (ISSN: 2212 4012) Volume 4 –Issue.9,
September 2015
proposed topologies is the fact that it only
involves a slight modification of the original
buck converter.
minimize the leakage inductance, in other
cases extensive interleaving must be used to
obtain low leakage.
CONCLUSION
REFERENCE
A novel voltage regulator buck converter
with a tapped inductor for fast transient
response applications is proposed. Analysis,
design, and performance evaluations of two
interleaved forward converters with
common output-filter inductor (one-choke
approach) and separate output-filter
inductors (two-choke
approach)
are
presented. Several attempts were pursued
earlier to model the self-oscillating
converters, and being able to accurately
capture only the low-frequency behavior
without the effect of switching delay. It was
shown that the system is of the second order,
and the effect of switching delay in smallsignal sense is minimal justifying the use of
rather simple models in predicting
accurately the dynamics of the associated
converter.
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With the tapped inductor and auxiliary
switch, the proposed converter is able to
achieve faster transient response comparing
to the conventional buck converter.
Meanwhile, the control circuit and method
of the auxiliary switch are simple and low
cost. The detailed simulated analysis and
experimental results demonstrated the
effectiveness of the proposed converter. It
has been shown that such a tapped-inductor
fast transient method is very suitable for all
types of the dc–dc converter with basic LC
output filter. If cost and size restrictions
allow, a large core should be used in order to
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