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AUTOMATIC VOLTAGE REGULATOR
TECHNICAL FIELD
The present invention relates to an automatic voltage regulator, particularly
to an
automatic voltage regulator capable of precisely controlling an output voltage
level by
using a toroidal autotransformer.
BACKGROUND
An automatic voltage regulator using a toroidal autotransformer can be
implemented using various regulator windings. However, the output voltage of
such a
regulator is always determined by the winding of its primary and secondary
coils. Thus,
in order to output various voltages, an automatic voltage regulator using a
toroidal
autotransformer is designed to wind coils according to the desired voltage or
have
several output taps.
For example, as illustrated in Fig. 1, an autotransformer can be designed to
have a
plurality of taps (a, b, c) on a field winding (200) excited in a main winding
(100) so as
to output various voltage levels. If the toroidal autotransformer is so
designed that in
case where 220V is applied to the main winding (100), 20V is applied to both
ends of
the main winding (100) and each tap of the field winding (200) reduces the
voltage by
5V, the toroidal autotransformer can supply 200V from the first tap (a), 205V
from the
second tap (b), and 210V from the third tap (a), to an output terminal.
As such, conventional automatic voltage regulators supply discrete output
voltages with a large deviation between the voltages. For example, in the
example as
described above, each of the output voltages with a deviation of 5V, i.e.,
each of 200V,
205V and 210V, is selectively supplied. Accordingly, conventional automatic
voltage
regulators cannot provide precise voltage control.
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As such, conventional automatic voltage regulators, providing low precision,
are
very inconvenient for users. We will explain this in more detail with an
example of a
power saving device using an automatic voltage regulator providing low
precision.
In the case of a high-story apartment, a distribution board is installed in a
basement.
About 235V is supplied to the first floor, but the supply voltage decrease as
the floor
gets higher, and as a result, about 205V is supplied to the 15th floor. In
general, an
electronic appliance can operate in a stable manner when a voltage of 205V is
supplied.
Thus, in case where each house uses a power saving device which decreases the
voltage
by about IOV, it is not ensured that a house supplied with a voltage of 215V
or lower
will obtain at least the minimum voltage required for providing stable
operation, 205V,
due to the use of an inappropriate power saving device. Meanwhile, in the case
of the
highest floor, it is necessary to increase the voltage level so that a stable
voltage can be
supplied in a consistent manner.
That is, in the case of a high-story apartment, there is a large deviation in
the system
voltage provided to a consumer between low floors and high floors. The floors
of a
high-story apartment are classified into floors where the voltage needs to be
reduced to
save power and floors where the voltage needs to be increased so that a stable
voltage
can be supplied. However, conventional automatic voltage regulators are not
capable
of supplying voltage levels with such a large deviation between them while
controlling
the voltages precisely, and accordingly users have suffered great
inconvenience.
The present invention solves the problems of conventional technology; the
present
invention provides an automatic voltage regulator capable of precisely
controlling the
voltage level and thereby of supplying an appropriate voltage.
Meanwhile, in order for a conventional automatic voltage regulator to operate
in a
power electronic system, complex features such as a main transformer,
excitation
transformer, detection transformer, highly sensitive effective value detection
circuit,
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high speed A/D transform circuit, triac switching circuit, etc. are required.
As a result,
conventional automatic voltage regulators have such high prices that they are
used in a
special case such as an experiment requiring expensive laboratory equipments.
Thus, a
general user cannot afford such regulators, and thus the conventional
regulators do not
have marketability.
In addition, because such complex devices cannot operate normally if the
frequency
and level of a system voltage changes, conventional automatic voltage
regulators have
to be manufactured in consideration of electricity environment.
In contrast, the automatic voltage regulator of the present invention has a
simple
structure which does not use a power semiconductor circuit, and thus can
control
voltage precisely regardless of electricity environment.
Meanwhile, the reason why conventional automatic voltage regulators
selectively
output discrete output voltage levels with a large deviation between them is
because the
regulators output an output voltage from a tap fixedly placed on a second ary
coil.
The reason for the technical limitation is because a very limited range of
winding
methods have been used for a toroidal core. In the current process of
producing a
toroidal core, a main winding is wound on a toroidal core, and then a coil of
a certain
thickness is wound on the main winding to form field windings where
input/output taps
are formed. If a non-conductive coil is inserted between the main winding and
field
windings of a toroidal core, problems occur such as generation of fumes from
the
inserted coil. Thus, in this process, only field windings serially connected
by taps and
a main winding are used.
The present invention is to improve such a winding method for conventional
toroidal
cores and thereby to output various levels of inductive voltages.
SUMMARY
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The present invention was conceived to solve said problems of conventional
technology. The objective of the present invention is to provide an automatic
voltage
regulator capable of outputting continuous voltage levels and thereby of
controlling
voltage precisely.
The above objective of the present invention can be achieved by providing an
automatic voltage regulator for converting an input voltage applied to an
input terminal
and outputting the converted input voltage to an output terminal according to
the present
invention, comprising: a main winding unit having one end thereof connected to
the
input terminal and the other end thereof connected to the output terminal, and
having a
plurality of main windings and a plurality of first switches for switching so
that the
plurality of main windings are selectively serially connected; a field winding
excited in
at least one of the main windings connected serially by the first switches of
the main
winding unit; a second switch for selectively connecting one end of the field
winding to
either a reference potential or the output terminal; a third switch for
connecting the other
end of the field winding to either the reference potential or the input
terminal; and a
control unit which regulates the level of an output voltage output to the
output terminal
by switching control of the plurality of first switches, the second switch,
and the third
switch.
In addition, said automatic voltage regulator of the present invention further
comprises
a level measurement unit for measuring the level of the input voltage inputted
to the
input terminal, and wherein the control unit is configured to be able to: if a
predetermined target voltage is higher than the level of the input voltage
measured by
the level measurement unit, switch control the plurality of first switches in
response to a
voltage difference between the predetermined target voltage and the measured
level of
the input voltage, control the second switch to connect the one end of the
field winding
to the reference potential, and control the third switch to connect the other
end of the
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field winding to the input terminal, and if the predetermined target voltage
is lower than
the level of the input voltage, switch control the plurality of first switches
in response to
the difference between the predetermined target voltage and the measured level
of the
input voltage, control the second switch to connect the one end of the field
winding to
the output terminal, and control the third switch to connect the other end of
the field
winding to the reference potential.
In addition, said automatic voltage regulator of the present invention may
further
comprise a user input unit for inputting the predetermined target voltage from
the user.
In addition, preferably, said automatic voltage regulator of the present
invention further
comprises a bypass path for causing the input voltage to bypass the main
winding unit;
and a bypass switch for switching a connection condition for the bypass path,
and
wherein if the level of the input voltage corresponds to the predetermined
target voltage,
the automatic voltage regulator is configured to turn on the bypass switch to
cause the
input voltage to bypass the main winding unit.
In addition, according to the present invention, the field winding is wound on
a
toroidal core, the plurality of main windings wind the field winding, and the
plurality of
main windings are wound on the toroidal core so as not to overlap.
The objective of the present invention can be achieved by another embodiment
of the
present invention, an automatic voltage regulator for converting an input
voltage
inputted to an input terminal to output the converted input voltage to an
output terminal,
comprising: a main winding unit having one end thereof connected to the input
terminal
and the other end thereof connected to the output terminal, and having a
plurality of
main windings and a plurality of first switches for switching so that the
plurality of
main windings are selectively serially connected; a field winding excited in
at least one
of the main windings connected serially by the first switches of the main
winding unit;
and a control unit which regulates the level of an output voltage output to
the output
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terminal by switching control of the plurality of first switches, the second
switch, and
the third switch.
The automatic voltage regulator further comprises a level measurement unit for
measuring the level of an input voltage inputted to the input terminal, and if
the
predetermined target voltage is lower than the level of the input voltage, the
control unit
switch controls the plurality of first switches in response to a voltage
difference between
the target voltage and the measured level of the input voltage.
In addition, the automatic voltage regulator of the present invention further
comprises a bypass path to cause the input voltage to bypass the main winding
unit; and
a bypass switch for switching a connection condition for the bypass path, and
if the
level of the input voltage corresponds to the predetermined target voltage,
the automatic
voltage regulator is configured to turn on the bypass switch to cause the
input voltage to
bypass the main winding unit.
BRIEF DESCRIPTION OF DRAWINGS
Fig. 1 is a schematic drawing of the circuit for explaining that in
conventional
toroidal transformers, a plurality of voltage levels are output from a
plurality of tabs of
the field winding.
Fig. 2 is a schematic drawing of the internal structure of the automatic
voltage
regulator capable of regulating the output voltage to the voltage
corresponding to
1 [turn] according to the first embodiment of the present invention.
Fig. 3 is a schematic drawing of the internal structure of the automatic
voltage
regulator according to the second embodiment of the present invention.
Fig. 4 and Fig. 5 are schematic drawings for explaining the winding method of
the
toroidal transformer used in the embodiments of the present invention.
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DETAILED DESCRIPTION
The embodiments of the present invention are explained in detail with
reference to
the accompanying drawings.
Fig. 2 is a schematic drawing of the internal structure of the automatic
voltage
regulator according to the first embodiment of the present invention.
Referring to Fig.2, the automatic voltage regulator is configured to comprise
a
main winding unit (1) having a plurality of main windings (14-1 an) and a
plurality of
first switches (lbo-lbn), a field winding (2), a second switch (3), a third
switch (4), a
bypass switch (5), a level measurement unit (6), an input unit (7) and a
control unit (8).
The main winding unit (1) has one end connected to an input terminal (L 1) to
which an input voltage applies and the other end connected to an output
terminal (L2).
The circuit connection between both ends (connection among the main windings
(1ao-lan)) is determined according to how the plurality of first switches (lbo-
lbn) are
switch connected. That is, as illustrated, depending on whether the first
switches
(1 bo,.,1 bn) are connected to one end of the main windings (14-la,,), it is
determined
whether the corresponding main windings (lao-lan) are comprised as one element
of a
serial circuit connecting both ends of the main winding unit (1). Hereinafter,
it is
referred to as a "serial mode" where the first switches (1 bo,.,1 bn) are
connected to one
end of the main windings (lao-lan) so that the main windings (lao-lan) become
one
part of the serial circuit to increase the total number of main windings,
whereas it is
referred to as an "insulating mode" where the main windings (1 ao-l an) are
insulated
from the serial circuit.
By switching control of the plurality of first switches (lbo-lbn) in the
serial mode
or insulating mode individually, the main windings (1 a0. 1 an) comprised in
the serial
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circuit which connects both ends of the main winding unit (1) can be selected,
and
thereby the total number of main windings comprised in the serial circuit can
be
controlled.
In particular, in the present embodiment, the plurality of main windings (1 ao-
1 an)
are formed to have turns of 20=1, 21=2, 22=4, 23=8, ..., 2 T(turns) (here, n
is a natural
number). Thus, by combining the main windings (1a-4a) to form a serial
circuit, the
total number of main windings of the serial circuit between both ends of the
main
winding unit (1) can be regulated so as to correspond to a natural number
within
expressible range. For example, if n is 10, the number of main windings can be
regulated to have turns corresponding to any natural number between 1 2047.
The field winding (2) is excited in the main windings (1 ao- 1 an) serially
connected
between both ends of the main winding unit (1). Therefore, the turns of the
field
winding (2) are fixed, but the level of voltage at which to excite the field
winding (2)
varies depending on the total number of main windings comprised in the serial
circuit of
the main winding unit (1).
The second switch (3) is designed to selectively connect one end (2a) of the
field
winding (2) to either a reference potential (N) or the output terminal (L2),
and in this
connection, the third switch (4) is designed to selectively connect the other
end (2b) of
the field winding (2) to either the reference potential (N) or the input
terminal (LI).
To be specific, if the second switch (3) is switched to connect one end (2a)
of the
field winding (2) to the output terminal (L2), the third switch (4) is
inevitably switched
to connect the other end (2b) of the field winding (2) to the reference
potential (N). In
contrast, if the second switch (3) is switched to connect one end (2a) of the
field
winding (2) to the reference potential (N), the third switch (4) is inevitably
switched to
connect the other end (2b) of the field winding (2) to the input terminal
(LI).
This is for conversion between a mode where an inductive voltage formed in the
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field winding (2) is added to the input voltage (hereinafter, "addition mode")
and a
mode where the inductive voltage is subtracted from the input voltage
(hereinafter,
"subtraction mode"). In the following description, details are given to
explain which
mode is used under which condition. Here, details are given to explain that
the second
switch (3) and the third switch (4) are interlocked in a certain way and
switched for
conversion between these modes.
In the present experimental example, an embodiment is explained where the
winding direction of the field winding (2) and main windings (lao-lan) are
uniformly
fixed to a toroidal core, and particularly, if one end (2a) of the field
winding (2) is
connected to the output terminal (L2) and the other end is connected to the
reference
potential (N), the field winding (2) and the main windings (lao-lan) are wound
to
operate in subtraction mode.
Referring to Fig. 2 again, the bypass switch (5) is configured to directly
connect
the input terminal (L 1) to the output terminal (L2) or insulate the input
terminal (L 1)
from the output terminal (L2), and provides a path for bypassing for the input
voltage
when a user attempts to output the input voltage without change.
The level measurement unit (6) is configured to measure the level of voltage
inputted through the input terminal (L 1), and a peak value, or an rms value,
is measured
and output.
The input unit (7) is configured to receive a target voltage from a user that
the user
attempts to output, and is variously implemented as a panel where an input
switch such
as an up-down key is formed, a receiving device for receiving a remote control
instruction, etc. The target voltage may be a value stored as default or
previously
inputted by the user, or a value newly revised during operation.
The control unit (8) compares the input voltage measured at the level
measurement unit (6) and the target voltage, and performs switching control
operation
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of the first-third switches (lbo-lb,,, 3, 4) and bypass switch (5) to adjust
the input
voltage to the target voltage.
Focusing on the operation of the control unit (8), the overall operation of
the
automatic voltage regulator illustrated in Fig. 2. will be explained according
to the target
voltage and the input voltage.
For better understanding, experimental data as shown in below <Table 1> will
be
referred to. <Table 1> shows experimental data showing how the total turns of
the
main winding unit (1) are determined as the input voltage is inputted between
187V and
220V under the condition where the turns of the field winding (2) are fixed at
SOOT and
the target voltage is set to 220V.
Number
Target Input Voltage of main Voltage
voltage voltage difference windings to be regulation
required
220 0 Bypass 0.0%
219 1 2 0.5%
218 2 5 0.9%
217 3 7 1.4%
216 4 9 1.8%
215 5 12 2.3%
214 6 14 2.7%
22OV
213 7 16 3.2%
212 8 19 3.6%
211 9 21 4.1%
210 10 24 4.5%
209 11 26 5.0%
198 22 37 10.0%
187 33 88 15.0%
<Table 1>
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i) If the target voltage (220V) is identical to the input voltage (220V) -
bypass
mode:
The input voltage is controlled to be output without change. To this end, the
control unit (8) turns on the bypass switch unit (5) to cause the input
voltage to bypass
the main winding unit (1) and be output to the output terminal (L2). (Refer to
the first
line of Table 1)
ii) If the target voltage (220V) is higher than the input voltage - addition
mode:
The input voltage must be boosted to the target voltage.
To this end, the control unit (8) controls the first-third switches and bypass
switch
(5) to cause the input voltage to be boosted for output.
To be specific, the control unit (8) turns off the bypass switch (5), controls
the
second switch (3) to connect one end (2a) of the field winding (2) to the
reference
potential (N), and controls the third switch (4) to connect the other end (2b)
of the field
winding (2) to the input terminal (L1) (addition mode).
Meanwhile, the control unit (8) regulates the level of the inductive voltage
of the
field winding (2) which is the size of added voltage so as to compensate the
difference
between the level of the input voltage measured at the level measurement unit
(6) and
the target voltage. To achieve this, the control unit (8) calculates the total
turns of the
main winding unit (1) that can induce the voltage corresponding to the voltage
difference, and controls the first switches (lbo-lbõ) so that the main
windings (lao-laõ)
to be combined according to the calculation form a serial circuit. That is,
the control
unit (8) selectively switch controls the corresponding first switches (lbo-
lbõ) to the
serial mode or insulating mode so that the combination of main windings
corresponds to
the total calculated turns.
Referring to <Table 1>, it can be confirmed that as the input voltage gets
lower
than the target voltage 220V and the voltage difference increases, the turns
of the
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overall main winding unit (1), i.e., the sum of the turns of the main windings
(1 ao-1 aõ)
serially connected, should increase to increase the level of voltage induced
to the field
winding (2) and thus make voltage compensation possible. For example, in case
the
input voltage is 219 V, the voltage difference is IV and the number of main
windings to
be required is 2T, whereas in case the input voltage is 210V, the voltage
difference is
l OV and the number of main windings to be required is 24 T.
iii) If the target voltage is lower than the input voltage - subtraction mode:
The control unit (8) controls the first-third switches and bypass switch (5)
to
cause the input voltage to be subtracted for output.
To be specific, the control unit (8) turns off the bypass switch (5), controls
the
second switch (3) to connect one end (2a) of the field winding (2) to the
output terminal
(L2), and controls the third switch (4) to connect the other end (2b) of the
field winding
(2) to the reference potential (N).
Meanwhile, the control unit (8) regulates the level of the inductive voltage
of the
field winding (2), which is the size of subtracted voltage, so as to
compensate the
difference between the level of the input voltage measured at the level
measurement unit
(6) and the target voltage. To achieve this, the control unit (8) calculates
the total turns
of the main winding unit (1) that can induce the voltage corresponding to the
voltage
difference, and controls the first switches (1 bo-l bn) so that the main
windings (1 ao- Ian)
to be combined according to the calculation form a serial circuit. That is,
the control
unit (8) selectively switch controls the corresponding first switches (1bo-
lbn) in the
serial mode or insulating mode so that the combination of main windings
corresponds to
the total calculated turns.
Referring to <Table 1> again, it can be understood that the number of main
windings to be required is proportional to the absolute value of the
difference between
the target voltage and the input voltage. Therefore, whether the input voltage
is higher
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or lower than the target voltage merely relates to the switching mode of the
second
switch (3) and the third switch (4), but is not a factor that modifies the
number of main
windings to be required.
Comparing `voltage difference,' `voltage regulation' and `number of main
windings to be required' among the columns at <Table 1>, it can be understood
that they
are proportional to one another. That is, as the voltage difference is
greater, the voltage
level to be compensated is greater. Thus, it can be understood that the total
number of
main windings should be controlled to increase in order to increase the
inductive
voltage of the field winding (2).
In addition, <Table 1> shows that the voltage difference of less than IV as
well as
the difference of IV unit can be compensated, and it may vary depending on the
turns
and core capacity of the field winding (2). Therefore, the control unit (8)
stores data on
the voltage difference and the number of main windings to be required
according to
specifications in advance, and based on the stored data, the control unit (8)
can
selectively switch control the first switches (1 bo-1 bn) to serial mode or
insulating mode.
The constitution of Fig. 2 according to the first embodiment of the present
invention can be understood to be variously modified within the scope of the
present
invention.
For example, it can be understood that for the turns of the main windings
(lay-1 aõ), other combinations can be possible instead of 2k (k=0, 1, 2, 3,
...). For
example, once the turns and core capacity of the field winding (2) are
determined, it is
possible to decide on the number of the turns of the main windings (lao-laõ)
so as to
correspond to the voltage difference of 2'[V] (j=0, 1, 2, 3 ...). In this
case, it is difficult
to regulate the voltage of less than IV, but it is possible to compensate the
voltage
difference of IV unit.
Further, it can be understood that the turns of the field winding (2) may not
be
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fixed. In this case, it is necessary to properly select the number of turns
for the main
windings and field windings, which may be experimentally determined in
advance.
According to other embodiments of the present invention, in case the number of
turns of the main windings is not determined in advance according to the
voltage
difference, it is possible to increase or decrease the turns serially
connected after
measuring the level of the output voltage and evaluating the measured value to
find the
appropriate turns.
As explained above, under the environment of poor electric power supply where
the input voltage does not reach the rated voltage of electric appliance as
well as under
the environment where power saving is required, the automatic voltage
regulator of the
present invention can provide rated voltage by automatically boosting input
voltage.
The present invention can selectively boost or reduce the output voltage by
switching the second switch (3) and the third switch (4), and greatly improve
the extent
of boosting and reducing by switching the first switches (1 bo- 1 bõ ).
Fig. 3 is a schematic drawing of the circuit of the automatic voltage
regulator
according to the second embodiment of the present invention, which is almost
the same
internal structure as in Fig. 2. Thus, focusing on the differences in the
structural
characteristics between Fig. 3, and Fig. 2 and the first embodiment, a second
embodiment will be explained.
Referring to Fig. 3, one end of the field winding is fixedly connected to the
output
terminal, and the other end is fixedly connected to the reference potential.
Therefore, as mentioned in relation to the first embodiment, the automatic
voltage
regulator of Fig. 3 is used only for reducing the input voltage or allowing it
a bypass,
but cannot be used for boosting the input voltage.
Said limitation on usage results from consideration of actual industrial
usage, such
as consumers' demands for saving power, infrastructure where electric power
supply is
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stable, etc.
Although options on the mode of operation are limited compared to those of the
first embodiment, the automatic voltage regulator of the second embodiment is
the same
as that of the first embodiment, in that it is capable of operation in the
aforementioned
subtraction mode and precise control down to 1 [V].
Fig. 4 and Fig. 5 are schematic diagrams for explaining the windings of a
toroidal
transformer according to the first and second embodiments of the present
invention.
Referring to Fig. 4, the field winding (2) is wound so as to be distributed
all over a
toroidal core first. Next, as illustrated in Fig. 5, a plurality of main
windings (lao-laõ)
are wound on the field winding (2), i.e., coils are wound to cover the field
winding (2)
so as not to overlap. Each of the main windings (lao-laõ) is configured to
have a
starting point and terminating point of the winding, and the plurality of main
windings
(1 ao-1 aõ) are counted and distinguished by the unit consisting of the
starting point and
terminating point.
As explained above, conventional toroidal transformers were configured to
remove a tab so as to be capable of obtaining different levels of inductive
voltage, with
the field winding (2) wound on the main windings (1 ao- 1 an), and thereby,
the degree of
boosting and reducing of voltage is fixed and extremely limited.
In contrast, in the toroidal transformer according to the present invention,
the main
windings (1a'-4a) are distributed and wound on the field winding (2) so as not
to
overlap, and thus it can obtain various levels of output voltage, which
provides a wide
choice of selections compared to conventional toroidal transformers.
As described above, the present invention has precise voltage control to
enable the
output of the voltage level desired by the user, and precisely carries out a
variety of
applications of power saving and voltage booster. In particular, the present
invention
can boost/reduce the input voltage to provide a desired target voltage within
an error
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range of 1 volt or less.
Also, the present invention comprises a simple relay switching circuit and
excludes semiconductor switching devices, thereby being capable of operating
adaptively in different system environments without an additional
modification.
Further, the present invention does not form many output tabs or auxiliary
coils,
and can regulate the voltage in a broader range, and at the same time can
accurately
output any values within the voltage regulation band.
In addition to the embodiments illustrated and described above, a person
having
ordinary knowledge in the art to which the present invention pertains can
understand
that various modifications of the present embodiments can be practiced without
deviating the technological spirit or principle of the present invention.
For example, the first switch of the present invention is to flexibly
determine the
turns of the main windings serially connected within a circuit, and thus can
be placed at
different positions unlike from the positions in Fig. 2 and Fig. 3. To be
specific, even if
a plurality of tabs are placed on the main windings, and any one of these tabs
is
connected to either the input terminal or output terminal, the winding of the
main
windings can be selectively modified.
Therefore, the present invention must be interpreted to include all cases
where the
first switch is arranged to determine the final turns of the main windings,
and such
modifications must be understood to be within the scope of the present
invention.
The scope of invention will be determined by the accompanying claims and their
equivalents.
INDUSTRIAL APPLICABILITY
The present invention can be usefully applied to all electronic equipment
requiring
a stable voltage.
CA 02722764 2010-10-27
(PCT/KR2009/001772) 17
