FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
POWER CONVERTING APPARATUS AND AIR CONDITIONER;
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION ORGANISED
AND EXISTING UNDER THE LAWS OF JAPAN, WHOSE ADDRESS IS 7-3,
MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO 100-8310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED.
2
DESCRIPTION
5 Field
[0001] The present invention relates to a power
converting apparatus and an air conditioner capable of
preventing or reducing inrush current generated at power-on.
10 Background
[0002] A device such as an outdoor unit of an air
conditioner including a circuit for power conversion
includes an inrush current prevention circuit that prevents
or reduces inrush current generated at power-on from doing
15 damage to the components. The inrush current prevention
circuit can be implemented by arranging a resistor or a
positive temperature coefficient (PTC) thermistor having
resistance varying depending on temperature between an
alternating-current (AC) power supply and a rectifier. In
20 a case of preventing or reducing inrush current by a
resistor or a PTC thermistor, power loss occurs due to
power consumption by the resistor. In order to solve this
problem, an invention taught in Patent Literature 1
prevents or reduces inrush current by providing a current
25 limiting capacitor between the AC power supply and the
rectifier such that current flow through the current
limiting capacitor to the rectifier for a while after
power-on and charge a smoothing capacitor provided on an
output side of the rectifier. In addition, after charging
30 of the smoothing capacitor is terminated, the current
supply path is switched so that current flows to the
rectifier, bypassing the current limiting capacitor.
3
Citation List
Patent Literature
[0003] Patent Literature 1: Japanese Patent Application
Laid-open No. 2008-136316
5
Summary
Technical Problem
[0004] The invention taught in Patent Literature 1 needs
to additionally provide the capacitor for preventing or
10 reducing inrush current, which increases the circuit size.
[0005] The present invention has been made in view of
the above, and an object thereof is to provide a power
converting apparatus capable of preventing or reducing
inrush current while avoiding an increase in circuit size.
15
Solution to Problem
[0006] To solve the aforementioned problems and achieve
the object, a power converting apparatus according to the
present invention includes a diode bridge that converts
20 first AC power supplied from an AC power supply into DC
power, a main circuit capacitor that smooths the DC power,
an inverter that converts the DC power smoothed by the main
circuit capacitor into second AC power and supplies the
second AC power to a load, and at least one capacitor that
25 reduces a noise component included in the first AC power.
The power converting apparatus also includes a path
switching unit that switches a charging path for the main
circuit capacitor so that current output from the AC power
supply flows into the main circuit capacitor via the
30 capacitor from when supply of the first AC power starts
until a voltage of the main circuit capacitor reaches a
predetermined voltage, and that the current output from the
AC power supply flows into the main circuit capacitor
4
without passing through the capacitor after the voltage of
the main circuit capacitor reaches the predetermined
voltage.
Advantageous Effects 5 of Invention
[0007] According to the present invention, an effect of
achieving a power converting apparatus capable of
preventing or reducing inrush current while avoiding an
increase in circuit size is produced.
10
Brief Description of Drawings
[0008] FIG. 1 is a diagram illustrating an example of a
configuration of a power converting apparatus according to
a first embodiment.
15 FIG. 2 is a diagram illustrating a first charging path
of main circuit capacitors of the power converting
apparatus according to the first embodiment.
FIG. 3 is a diagram illustrating a second charging
path of the main circuit capacitors of the power converting
20 apparatus according to the first embodiment.
FIG. 4 is a graph illustrating an example of a change
in voltage after power-on of the main circuit capacitors of
the power converting apparatus according to the first
embodiment.
25 FIG. 5 is a graph illustrating the relation of
voltages of respective capacitors included in the power
converting apparatus according to the first embodiment.
FIG. 6 is a diagram illustrating an example of a
configuration of a power converting apparatus according to
30 a third embodiment.
FIG. 7 is a diagram illustrating an example of
hardware for implementing a control circuit of the power
converting apparatus according to each of the embodiments.
5
Description of Embodiments
[0009] A power converting apparatus and an air
conditioner according to certain embodiments of the present
invention will be described in detail below 5 with reference
to the drawings. Note that the present invention is not
limited to the embodiments.
[0010] First Embodiment
FIG. 1 is a diagram illustrating an example of a
10 configuration of a power converting apparatus according to
a first embodiment of the present invention.
[0011] A power converting apparatus 100 according to the
present embodiment is connected to a power supply 1 that is
a three-phase four-wire alternating-current (AC) power
15 supply. The power converting apparatus 10 converts first
AC power supplied from the power supply 1, into second AC
power to be supplied to a load, which is not illustrated.
In the following description, the three phases of threephase
AC power output from the power supply 1 will be
20 referred to as a first phase, a second phase, and a third
phase, where appropriate. The load that is not illustrated
in FIG. 1 is a motor for driving a compressor of an air
conditioner, a motor for driving a blower fan of an air
conditioner, or the like.
25 [0012] The power converting apparatus 100 includes
capacitors 2 to 4, 9 to 11, 17A, and 17B, resistors 5 to 7,
18A, and 18B, a common coil 8, relays 13, 14, and 20, a
diode bridge 15, a direct-current (DC) reactor 16, an
inverter 19, and a control unit 21.
30 [0013] The capacitor 2 and the resistor 5 each have one
end connected to an output point of the first phase of the
power supply 1, and the other end connected to a neutral
point of the power supply 1. The capacitor 3 and the
6
resistor 6 each have one end connected to an output point
of the second phase of the power supply 1, and the other
end connected to the neutral point of the power supply 1.
The capacitor 4 and the resistor 7 each have one end
connected with an output point of the 5 third phase of the
power supply 1, and the other end connected to the neutral
point of the power supply 1. While the phase to which the
capacitor 2 and the resistor 5 are connected is referred to
as the first phase, this is only for convenience of
10 explanation.
[0014] AC powers of the first to third phases output by
the power supply 1 are input to the diode bridge 15 via
lines connected to the output points of the individual
phases. In addition, the capacitors 9 to 11 for noise
15 component reduction are connected between the neutral point
and the output points of the first to third phases of the
power supply 1. One end of the capacitor 9 is connected to
a first line that is a line interconnecting the output
point of the first phase of the power supply 1 and an input
20 point of the first phase of the diode bridge 15. The other
end of the capacitor 9 is connected to a neutral line. The
capacitor 9 is a capacitor for reducing the noise component
on the first line. One end of the capacitor 10 is
connected to a second line that is a line interconnecting
25 the output point of the second phase of the power supply 1
and an input point of the second phase of the diode bridge
15. The other end of the capacitor 10 is connected to the
neutral line. The capacitor 10 is a capacitor for reducing
the noise component on the second line. One end of the
30 capacitor 11 is connected to a third line that is a line
interconnecting the output point of the third phase of the
power supply 1 and an input point of the third phase of the
diode bridge 15. The other end of the capacitor 11 is
7
connected to the neutral line. The capacitor 11 is a
capacitor for reducing the noise component on the third
line.
[0015] In addition, the common coil 8 for reducing
common mode noise flowing through the first 5 line to third
lines and the neutral line is provided between the
capacitors 2 to 4, the resistors 5 to 7 and the capacitors
9 to 11 described above.
[0016] The capacitors 2 to 4, 9 to 11, the resistors 5
10 to 7, and the common coil 8 illustrated in FIG. 1 are
elements provided for reducing noise components included in
AC power output from the power supply 1. Similar elements
are also provided in typical power converting apparatuses.
Note that the resistor 5 to 7 also function to balance
15 voltages applied to the capacitor 2 to 4.
[0017] The diode bridge 15 rectifies AC power supplied
from the power supply 1 to thereby convert the AC power
into DC power. Specifically, the diode bridge 15 converts
the first AC power supplied from the power supply 1, into
20 DC power. The DC power output from the diode bridge 15 is
supplied to the inverter 19. The inverter 19 converts the
input DC power into the second AC power, and supplies the
second AC power to the load, which is not illustrated.
[0018] The DC reactor 16, the capacitors 17A and 17B,
25 which are main circuit capacitors, and the resistors 18A
and 18B are provided between the diode bridge 15 and the
inverter 19. The DC reactor 16 and the capacitors 17A and
17B are provided for smoothing DC power output from the
diode bridge 15. The resistors 18A and 18B are provided
30 for adjusting the balance of voltages charged in the
capacitors 17A and 17B and for discharging the capacitors
17A and 17B.
[0019] The DC reactor 16 has one end connected to an
8
output point on the positive side of the diode bridge 15
and the other end connected to an input point on the
positive side of the inverter 19. One end of the capacitor
17A and one end of the resistor 18A are also connected to
the other end of the DC reactor 16. 5 One end of the
capacitor 17B is connected to the other end of the
capacitor 17A, and one end of the resistor 18B is connected
to the other end of the resistor 18A. The other end of the
capacitor 17B and the other end of the resistor 18B are
10 connected to an output point on the negative side of the
diode bridge 15 and an input point on the negative side of
the inverter 19. In addition, a short circuit is defined
between a connection point interconnecting the capacitors
17A and 17B and a connection point interconnecting the
15 resistors 18A and 18B.
[0020] The relay 13, which is a first relay, is provided
on the second line, and has one end connected to the common
coil 8 and the other end connected to one end of each of
the diode bridge 15 and the capacitor 10. Namely, the
20 relay 13 is provided between the common coil 8 on the
second line and the connection point of the second line
connected to the capacitor 10. The relay 13 is controlled
by the control unit 21.
[0021] The relay 14, which is a second relay, is
25 provided on the third line, and has one end connected to
the common coil 8 and one end of the capacitor 11. The
relay 14 has the other end connected to the diode bridge 15.
Namely, the relay 14 is provided between the diode bridge
15 on the third line and the connection point of the third
30 line connected to the capacitor 11. The relay 14 is
controlled by the control unit 21.
[0022] The relay 20, which is a third relay, is provided
on the neutral line, and has one end connected to the
9
capacitor 9 and the other end connected to the capacitor 10.
Namely, the relay 20 is provided between the connection
point of the neutral line connected to the capacitor 9 and
the connection point of the neutral line connected to the
capacitor 10. When the relay 20 5 is turned off, the
capacitors 10 and 11 are disconnected from the neutral line.
The relay 20 is controlled by the control unit 21.
[0023] The control unit 21 controls each of switching
elements (which are not illustrated) of the inverter 19,
10 and controls the relays 13, 14, and 20. The control unit
21 is configured to operate upon receiving power supply
from a power supply circuit, which is not illustrated. The
power supply circuit converts power supplied from the power
supply 1 into DC voltage necessary for the control unit 21
15 and supplies the DC voltage to the control unit 21. The
control unit 21 constitutes, together with the relays 13,
14, and 20, a path switching unit for switching charging
paths of the capacitors 17A and 17B.
[0024] Next, a description will be made as to operation
20 of the power converting apparatus 100 when the power
converting apparatus 100 is powered on, that is, when
supply of AC power from the power supply 1 to the power
converting apparatus 100 starts.
[0025] Before the power converting apparatus 100 is
25 powered on, the relays 13, 14, and 20 are open. When the
power converting apparatus 100 is powered on with the
relays 13, 14, and 20 open, power is supplied taking
alternately a path illustrated in FIG. 2 and a path
illustrated in FIG. 3, thereby charging the capacitors 17A
30 and 17B. Specifically, in a case of a first charging path
201 illustrated in FIG. 2, current output from the power
supply 1 to the first line flows to the second line via a
diode corresponding to the first phase among three diodes
10
provided on the positive side of the diode bridge 15, the
DC reactor 16, the capacitors 17A and 17B, and a diode
corresponding to the second phase among three diodes
provided on the negative side of the diode bridge 15,
further flows to the third line via the 5 capacitor 10 and
the capacitor 11, and then returns to the power supply 1.
In addition, in a case of a second charging path 202
illustrated in FIG. 3, current output from the power supply
1 to the third line flows to the second line via the
10 capacitor 11 and the capacitor 10, further flows to the
first line via a diode corresponding to the second phase
among the three diodes provided on the positive side of the
diode bridge 15, the DC reactor 16, the capacitors 17A and
17B, and a diode corresponding to the first phase among the
15 three diodes provided on the negative side of the diode
bridge 15, and then returns to the power supply 1. In this
manner, the capacitors 17A and 17B are charged through the
two paths.
[0026] Assume that the capacitance of the capacitors 10
20 and 11 and the capacitance of the capacitors 17A and 17B
provided on the two charging paths satisfy the relation
expressed by formula (1).
(the capacitance of the capacitors 10 and 11) << (the
capacitance of the capacitors 17A and 17B) ... (1)
25 [0027] In the case of power-on under such a condition,
the capacitors 17A and 17B of the power converting
apparatus 100 are charged by an amount of charge received
by the capacitors 10 and 11. As expressed by the formula
(1), because the capacitance of the capacitors 10 and 11 is
30 much smaller than that of the capacitors 17A and 17B, the
voltage charged in the capacitors 17A and 17B is small.
Thus, in the power converting apparatus 100, the charging
operations using the two charging paths described above are
11
repeated every power supply period, and the capacitors 17A
and 17B are thus charged over a time of a few tens of
seconds as illustrated in FIG. 4. FIG. 4 is a graph
illustrating an example of a change in voltage of the
capacitors 17A and 17B after power-on, 5 which are the main
circuit capacitors of the power converting apparatus 100
according to the first embodiment. The voltage illustrated
in FIG. 4 is a voltage across the capacitors 17A and 17B
connected in series, that is, a sum of the voltage of the
10 capacitor 17A and the voltage of the capacitor 17B, and is
applied to the inverter 19.
[0028] In the charging operations described above, it
takes time from power-on until the voltage across the
capacitors 17A and 17B reaches a voltage necessary for the
15 inverter 19, which is a predetermined voltage. This is
because current flowing into the capacitors 17A and 17B is
limited to a value corresponding to the capacitance of the
capacitors 10 and 11. Thus, in the power converting
apparatus 100, the time taken from power-on until the
20 voltage across the capacitors 17A and 17B reaches the
predetermined voltage becomes longer, but is not a problem
because it takes more time for the power converting
apparatus 100 to perform an initialization process in
starting the operation. The initialization process herein
25 includes a process of communication with a board, which is
not illustrated, a process of obtaining information output
from respective sensors, which are not illustrated, a
process of checking whether or not abnormality is present
in a voltage detecting circuit and a current detecting
30 circuit, which are not illustrated, and the like. Note
that, if the charging time until the voltage of the
capacitors 17A and 17B reaches the predetermined voltage is
longer the time taken for the initialization process, a
12
display unit, which is not illustrated, may display a
waiting state to inform a user that it will take some time
before the operation starts.
[0029] In addition, because the first charging path 201
illustrated in FIG. 2 and the second 5 charging path 202
illustrated in FIG. 3 include the capacitors 10 and 11
having a capacitance smaller than that of the capacitors
17A and 17B and the current flowing into the capacitors 17A
and 17B is limited to a value corresponding to the
10 capacitance of the capacitors 10 and 11, an inrush current
generated when the power supply 1 is turned on is prevented
or reduced.
[0030] When charging of the capacitors 17A and 17B is
terminated, the control unit 21 controls the relays 13, 14,
15 and 20 in order that the capacitors 10 and 11 having been
used for preventing or reducing inrush current are used for
the original purpose, that is, in order that the capacitors
10 and 11 are used as capacitors for noise component
reduction. Specifically, the control unit 21 first turns
20 the relay 20 on. As illustrated in FIG. 5, when the
capacitors 17A and 17B, which are main circuit capacitors,
are sufficiently charged, the voltage across the capacitors
10 and 11 is small. The relay 20 is switched on in this
state, so as to prevent or reduce inrush current into the
25 capacitors 10 and 11 upon switching of the connection, and
start use of the capacitors 10 and 11 as capacitors for
noise component reduction. Thereafter, the control unit 21
switches the relays 13 and 14 on, and powers of the first
to third phases output by the power supply 1 are thus
30 supplied to the diode bridge 15. Specifically, the
charging path of the capacitors 17A and 17B is switched to
a third charging path that does not include the capacitors
10 and 11.
13
[0031] As described above, the power converting
apparatus 100 according to the present embodiment includes
the capacitors 9 to 11, which are capacitors for noise
component reduction connected between the neutral line and
the first to third lines for supplying, to 5 the diode bridge
15, the individual AC powers of three phases output from
the power supply 1, which is a three-phase four-wire AC
power supply, the relay 13 provided on the second line, the
relay 14 provided on the third line, the relay 20 provided
10 on the neutral line, the capacitors 17A and 17B, which are
main circuit capacitors, and the control unit 21 that
controls the relays 13, 14, and 20. In addition, the power
converting apparatus 100 uses capacitors provided for
reducing noise components, as capacitors for preventing or
15 reducing inrush current to the main circuit capacitors, the
inrush current being generated when the power supply 1 is
turned on. Specifically, in the power converting apparatus
100, the control unit 21 controls the relays to switch the
charging path of the main circuit capacitors, so that the
20 capacitors 10 and 11 are included in the charging path of
the main circuit capacitors from when the power supply 1 is
turned on until the voltage of the main circuit capacitors
reaches the predetermined voltage, and that the capacitors
10 and 11 are not included in the charging path of the main
25 circuit capacitors after the voltage of the main circuit
capacitors reaches the predetermined voltage. As a result,
inrush current at power-on can be prevented or reduced. In
addition, while the invention taught in Patent Literature 1
uses one capacitor (current limiting capacitor) for
30 preventing or reducing inrush current, and three relays
(two power supply switches and one current limiting switch)
for switching the path through which current flows to
prevent or reduce inrush current, the power converting
14
apparatus 100 according to the present embodiment is
capable of preventing or reducing inrush current without
providing an additional capacitor for preventing or
reducing inrush current. The power converting apparatus
100 can thus prevent or reduce inrush current 5 at power-on
while avoiding an increase in circuit size.
[0032] Second Embodiment
The power converting apparatus 100 described in the
first embodiment is configured to have no resistor for
10 balancing voltages inserted with respect to the capacitors
10 and 11 included in the charging paths (the first
charging path 201 and the second charging path 202) of the
main circuit capacitors, the charging paths being provided
before the voltage of the main circuit capacitors reaches
15 the predetermined voltage. Depending on the capacitance
ratio of the capacitors 10 and 11, the voltage may be
biased to one capacitor, with the result that the voltage
of the capacitor 10 and the voltage of the capacitor 11 may
become imbalanced. Thus, in a case where the voltages are
20 imbalanced and the voltage of the capacitor 10 or 11
exceeds a withstand voltage, resistors for balancing the
voltages may be provided in parallel with the capacitors 10
and 11. In addition, a resistor for balancing power
supplies may also be provided in parallel with the
25 capacitor 9 that is not included in the charging paths of
the capacitors.
[0033] As described above, the power converting
apparatus according to the second embodiment includes
resistors provided for balancing the voltages of the
30 capacitors provided for reducing noise components and
included in the charging paths of the main circuit
capacitors immediately after power-on. This can prevent or
reduce the voltage of one of the capacitors included in the
15
charging path of the main circuit capacitor from becoming
high and exceeding a withstand voltage immediately after
power-on.
[0034] Third Embodiment
FIG. 6 is a diagram illustrating 5 an example of a
configuration of a power converting apparatus according to
a third embodiment of the present invention. The power
converting apparatuses 100 according to the first and
second embodiments is each configured to convert a first AC
10 pose supplied from the power supply 1, which is a threephase
four-wire AC power supply, into a second AC power and
supply the second AC power to a load. In contrast, the
power converting apparatus 101 according to the third
embodiment illustrated in FIG. 6 converts single-phase AC
15 power supplied from the power supply 31, into a second AC
power, and supplies the second AC power to a load. In the
present embodiment, the single-phase AC power supplied from
the power supply 31 is the first AC power.
[0035] The power converting apparatus 101 includes
20 capacitors 32 and 37, relays 33 and 34, a diode bridge 35,
a DC reactor 36, a resistor 38, an inverter 39, and a
control unit 41.
[0036] The capacitor 32 has one end connected to the
power supply 31, and the other end connected to the relay
25 34. The capacitor 32 is provided for reducing a noise
component included in the first AC power.
[0037] The relay 33 has one end connected to a
connection point interconnecting the capacitor 32 and the
power supply 31, and the other end connected to the diode
30 bridge 35. The relay 34 includes a first terminal, a
second terminal, and a third terminal, and the capacitor 32
is connected to the first terminal. The second terminal of
the relay 34 is connected to the power supply 31 and the
16
diode bridge 35. The third terminal of the relay 34 is
connected to the diode bridge 35.
[0038] The diode bridge 35 rectifies AC power supplied
from the power supply 31 to convert the AC power into DC
power. Specifically, the diode bridge 5 35 converts the
first AC power supplied from the power supply 31 into DC
power. The DC power output from the diode bridge 35 is
supplied to the inverter 39. The inverter 39 converts the
input DC power into the second AC power, and supplies the
10 second AC power to the load, which is not illustrated.
[0039] The DC reactor 36, the capacitor 37, which is a
main circuit capacitor, and the resistor 38 are provided
between the diode bridge 35 and the inverter 39. The DC
reactor 36 and the capacitor 37 are provided to smooth DC
15 power output from the diode bridge 35. The resistor 38 is
provided to discharge the charged capacitor 37.
[0040] The DC reactor 36 has one end connected to an
output point on the positive side of the diode bridge 35,
and the other end connected to an input point on the
20 positive side of the inverter 39. One end of each of the
capacitor 37 and the resistor 38 is also connected to the
DC reactor 36. The other end of each of the capacitor 37
and the resistor 38 is connected to an output point on the
negative side of the diode bridge 35 and an input point on
25 the negative side of the inverter 39.
[0041] The control unit 41 controls each of switching
elements (which are not illustrated) of the inverter 39,
and controls the relays 33 and 34. The control unit 41 is
configured to operate upon receiving power supply from a
30 power supply circuit, which is not illustrated. The power
supply circuit converts power supplied from the power
supply 31 into DC voltage necessary for the control unit 41
and supplies the DC voltage to the control unit 41. The
17
control unit 41 constitutes, together with the relays 33
and 34, a path switching unit for switching charging paths
of the capacitor 37.
[0042] Next, a description will be made as to operation
of the power converting apparatus 5 101 when the power
converting apparatus 101 is powered on, that is, when
supply of AC power from the power supply 31 to the power
converting apparatus 101 starts.
[0043] Before the power converting apparatus 101 is
10 powered on, the relay 33 is open and the relay 34 is in a
connection state in which the capacitor 32 is inserted in
series between the power supply 31 and the diode bridge 35.
When the power converting apparatus 101 is powered on in
this state, the capacitor 37 is charged through a charging
15 path provided for reducing a noise component and including
the capacitor 32. Specifically, the capacitor 37 is
charged through two charging paths described below. Of the
two output points of the power supply 31, the output point
to which the capacitor 32 and the relay 33 are connected
20 will be referred to as a first output point and the other
will be referred to as a second output point. In charging
the capacitor 37 through a first charging path, current is
output from the first output point of the power supply 31,
flows into the capacitor 37 via the capacitor 32, the relay
25 34, a first positive-side diode, which is one of two diodes
provided on the positive side of the diode bridge 35, and
the DC reactor 36, and further returns to the power supply
31 via a first negative-side diode, which is one of two
diodes provided on the negative side of the diode bridge 35.
30 In addition, in charging the capacitor 37 through a second
charging path, current is output from the second output
point of the power supply 31, flows into the capacitor 37
via a second positive-side diode, which is the other of the
18
two diodes provided on the positive side of the diode
bridge 35, and the DC reactor 36, and further returns to
the power supply 31 via a second negative-side diode, which
is the other of the two diodes provided on the negative
side of the diode bridge 35, the 5 relay 34, and the
capacitor 32.
[0044] Assume that the capacitance of the capacitor 32
and the capacitance of the capacitor 37 satisfy the
relation expressed by formula (2).
10 (the capacitance of the capacitor 32) << (the
capacitance of the capacitor 37) ... (2)
[0045] The time taken from when the power converting
apparatus 101 is powered on until the voltage of the
capacitor 37 reaches a predetermined voltage, that is, a
15 voltage necessary for the inverter 39 is a few tens of
seconds in a manner similar to the case where the power
converting apparatus 100 according to the first embodiment
is powered on. The time is not a problem, as in the power
converting apparatus 100 according to the first embodiment.
20 In addition, inrush current into the capacitor 37 generated
at power-on is prevented or reduced.
[0046] When charging of the capacitor 37 is terminated,
the control unit 41 controls the relays 33 and 34 in order
that the capacitor 32 having been used for preventing or
25 reducing inrush current are used as a capacitor for noise
component reduction. Specifically, control unit 41 first
switches the contact point of the relay 34. Subsequently,
the control unit 41 turns the relay 33 on, so that the
capacitor 32 is connected in parallel with the diode bridge
30 35. When the capacitor 37 is sufficiently charged, the
voltage across the capacitor 32 is small, and inrush
current into the capacitor 32 when the contact point of the
relay 34 is switched is thus prevented or reduced.
19
[0047] For the power converting apparatus 101 according
to the present embodiment, as described above, the
capacitor 32, which is provided for reducing a noise
component included in the AC power output from the power
supply 31 that is a single-phase AC power 5 supply, is used
as a capacitor for preventing or reducing inrush current
into the capacitor 37, which is a main circuit capacitor,
the inrush current being generated when the power supply 31
is turned on. Specifically, the power converting apparatus
10 101 switches the charging path of the capacitor 37, which
is the main circuit capacitor, so that the capacitor 32 is
included in the charging path of the main circuit capacitor
from when the power supply 31 is turned on until the
voltage of the main circuit capacitor reaches the
15 predetermined voltage, and that the capacitor 32 is not
included in the charging path of the main circuit capacitor
after the voltage of the main circuit capacitor reaches the
predetermined voltage. As a result, it becomes possible to
prevent or reduce inrush current at power-on while avoiding
20 an increase in circuit size.
[0048] Next, a description will be made as to hardware
for implementing the control unit 21 of the power
converting apparatus 100 and the control unit 41 of the
power converting apparatus 101 described above. The
25 control unit 21 and the control unit 41 are implemented by
processing circuitry that is electronic circuitry. The
processing circuitry for implementing the control unit 21
and the control unit 41 may be dedicated hardware or a
control circuit including a memory and a processor for
30 executing programs stored in the memory.
[0049] In a case where the processing circuitry is
implemented by dedicated hardware, the processing circuitry
is an application specific integrated circuit (ASIC), a
20
field programmable gate array (FPGA), or a circuit
combining such circuits, for example.
[0050] Alternatively, in a case where the processing
circuitry is implemented by a control circuit, the control
circuit can be processing circuitry having 5 a configuration
illustrated in FIG. 7 including a processor 91 and a memory
92, for example. The processor 91 is a central processing
unit (CPU; also referred to as a central processing device,
a processing device, a computing device, a microprocessor,
10 a microcomputer, or a digital signal processor (DSP)), a
system large scale integration (LSI), or the like. In
addition, the memory 92 is a random access memory (RAM), a
read only memory (ROM), a flash memory, an erasable
programmable ROM (EPROM), an electrically erasable
15 programmable ROM (EEPROM; registered trademark) or the like.
[0051] In the case where the control units 21 and 41 are
implemented by the control circuit having the configuration
illustrated in FIG. 7, the control units 21 and 41 are
implemented by the processor 91 executing programs for
20 operating as the respective units. Specifically, the
programs are stored in advance in the memory 92, and the
control units 21 and 41 are implemented by the processor 91
by reading the programs from the memory 92 and executing
the programs.
25 [0052] The configurations presented in the embodiments
above are examples of the present invention, and can be
combined with other known technologies or can be partly
omitted or modified without departing from the scope of the
present invention.
30
Reference Signs List
[0053] 1, 31 power supply; 2 to 4, 9 to 11, 17A, 17B,
32, 37 capacitor; 5 to 7, 18A, 18B, 38 resistor; 8 common
21
coil; 13, 14, 20, 33, 34 relay; 15, 35 diode bridge; 16,
36 DC reactor; 19, 39 inverter; 21, 41 control unit; 100,
101 power converting apparatus; 201 first charging path;
202 second charging path.
5
22
We Claim :
1. A power converting apparatus comprising:
a diode bridge to convert first AC power supplied from
an AC power supply, into DC power;
a main circuit capacitor to smooth 5 the DC power;
an inverter to convert the DC power smoothed by the
main circuit capacitor into second AC power and supply the
second AC power to a load;
at least one capacitor to reduce a noise component
10 included in the first AC power; and
a path switching unit to switch a charging path for
the main circuit capacitor so that current output from the
AC power supply flows into the main circuit capacitor via
the capacitor from when supply of the first AC power starts
15 until a voltage of the main circuit capacitor reaches a
predetermined voltage, and that the current output from the
AC power supply flows into the main circuit capacitor
without passing through the capacitor after the voltage of
the main circuit capacitor reaches the predetermined
20 voltage.
2. The power converting apparatus according to claim 1,
wherein
after the voltage of the main circuit capacitor
25 reaches the predetermined voltage, the capacitor is used to
reduce the noise component.
3. The power converting apparatus according to claim 1 or
2, wherein
30 the at least one capacitor comprises a plurality of
capacitors,
the current output from the AC power supply flows into
the main circuit capacitor via the plurality of the
capacitors from when supply of the first AC power is
started until the voltage of the main circuit capacitor
reaches the predetermined voltage, and
a resistor connected in parallel with each of the
plurality 5 of capacitors
to become balance
4. The power converting apparatus according to any one of
claims 1 to 3, wherein
10 power.
5. The power converting apparatus according to claim 1 or
2, wherein the first AC power is single
15 6. An air conditioner comprising:
the power converting apparatus according to any one of
claims 1 to 5; and
a motor to receive supply of t
drive a compressor or a blower fan.