FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
[See section 10, Rule 13]
POWER CONVERSION APPARATUS, MOTOR DRIVE APPARATUS, AND
REFRIGERATION CYCLE APPARATUS;
MITSUBISHI ELECTRIC CORPORATION, A CORPORATION
ORGANISED AND EXISTING UNDER THE LAWS OF JAPAN, WHOSE
ADDRESS IS 7-3, MARUNOUCHI 2-CHOME, CHIYODA-KU, TOKYO
1008310, JAPAN
THE FOLLOWING SPECIFICATION PARTICULARLY DESCRIBES THE
INVENTION AND THE MANNER IN WHICH IT IS TO BE PERFORMED

2
DESCRIPTION
Field
[0001] The present disclosure relates to a power
5 conversion apparatus that converts alternating-current
power into desired power and also relates to a motor drive
apparatus and a refrigeration cycle apparatus.
Background
10 [0002] There is a conventional power conversion
apparatus that converts alternating-current power supplied
from an alternating-current power supply into desired
alternating-current power and supplies the desired
alternating-current power to a load in an air conditioner
15 or another apparatus. For example, in a technique
disclosed in Patent Literature 1 for a power conversion
apparatus as a control apparatus for an air conditioner,
alternating-current power supplied from an alternatingcurrent power supply is rectified by a diode stack as a
20 rectification unit and is further smoothed by a smoothing
capacitor. The smoothed power is converted by an inverter
composed of a plurality of switching elements into desired
alternating-current power for output to a compressor motor
as a load.
25
Citation List
Patent Literature
[0003] Patent Literature 1: Japanese Patent Application
Laid-open No. H07-71805
30
Summary
Technical Problems
[0004] However, a problem with the above-described

3
conventional technique is that a large current flows into
the smoothing capacitor, thus accelerating aging
degradation of the smoothing capacitor. To address this
problem, increasing capacitance of the smoothing capacitor
5 for restraining variation of ripple in a capacitor voltage
or using a smoothing capacitor with a greater tolerance to
ripple-induced degradation is a conceivable method but
causes increased costs of capacitor parts and causes the
apparatus to have an increased size.
10 [0005] The present disclosure has been made in view of
the above, and an object of the present disclosure is to
obtain a power conversion apparatus that enables its
increase in size to be restrained while restraining
degradation of a capacitor to be used for smoothing.
15
Solution to Problems
[0006] To solve the problem and achieve the object
described above, a power conversion apparatus according to
the present disclosure includes: a rectification and boost
20 unit rectifying a first alternating-current power supplied
from a commercial power supply and boosting a voltage of
the first alternating-current power; a capacitor connected
to output terminals of the rectification and boost unit; an
inverter that is connected across the capacitor, converts
25 power output from the rectification and boost unit and the
capacitor into a second alternating-current power, and
outputs the second alternating-current power to a load
including a motor; and a control unit performing operation
control on the rectification and boost unit, and performing
30 operation control on the inverter to cause the second
alternating-current power that includes a pulsation based
on a pulsation of power that flows into the capacitor from
the rectification and boost unit to be output from the

4
inverter to the load, to restrain a current that flows into
the capacitor.
Advantageous Effects of Invention
5 [0007] The power conversion apparatus according to the
present disclosure produces effects of enabling its
increase in size to be restrained and restraining
degradation of the capacitor that is used for smoothing.
10 Brief Description of Drawings
[0008] FIG. 1 is a diagram illustrating an exemplary
configuration of a power conversion apparatus according to
a first embodiment.
FIG. 2 is a diagram illustrating examples of currents
15 as well as an example of a capacitor voltage across a
capacitor in a smoothing unit in a comparative example in
which the current output from a boost unit has been
smoothed by the smoothing unit, causing the current that
flows into an inverter to be constant.
20 FIG. 3 is a diagram illustrating examples of the
currents as well as an example of the capacitor voltage
across the capacitor in the smoothing unit when a control
unit of the power conversion apparatus according to the
first embodiment has reduced the current that flows into
25 the smoothing unit through operation control of the
inverter.
FIG. 4 is a flowchart illustrating the operation of
the control unit of the power conversion apparatus
according to the first embodiment.
30 FIG. 5 is a diagram illustrating an example of a
hardware configuration that implements the control unit of
the power conversion apparatus according to the first
embodiment.

5
FIG. 6 is a diagram illustrating an exemplary
configuration of a power conversion apparatus according to
a second embodiment.
FIG. 7 is a diagram illustrating an exemplary
5 configuration of a power conversion apparatus according to
a third embodiment.
FIG. 8 is a diagram illustrating an exemplary
configuration of a refrigeration cycle apparatus according
to a fourth embodiment.
10
Description of Embodiments
[0009] With reference to the drawings, a detailed
description is hereinafter provided of a power conversion
apparatus, a motor drive apparatus, and a refrigeration
15 cycle apparatus according to embodiments of the present
disclosure.
[0010] First Embodiment.
FIG. 1 is a diagram illustrating an exemplary
configuration of a power conversion apparatus 1a according
20 to a first embodiment. The power conversion apparatus 1a
is connected to a commercial power supply 110 and a
compressor 315. The power conversion apparatus 1a converts
a first alternating-current power at a power supply voltage
Vs that is supplied from the commercial power supply 110
25 into a second alternating-current power having a desired
amplitude and a desired phase and supplies the second
alternating-current power to the compressor 315. The power
conversion apparatus 1a includes a voltage and current
detection unit 501, a rectification unit 130, a reactor 120,
30 a boost unit 600, a voltage detection unit 502, a smoothing
unit 200, an inverter 310, current detection units 313a and
313b, and a control unit 400. The rectification unit 130,
the reactor 120, and the boost unit 600 of the power

6
conversion apparatus 1a compose a rectification and boost
unit 700. The power conversion apparatus 1a and a motor
314 included in the compressor 315 compose a motor drive
apparatus 2a.
5 [0011] The voltage and current detection unit 501
detects a voltage value and a current value of the first
alternating-current power at the power supply voltage Vs
that is supplied from the commercial power supply 110 and
outputs the detected voltage and current values to the
10 control unit 400. The rectification unit 130 includes a
bridge circuit composed of rectifier elements 131 to 134,
and rectifies the first alternating-current power at the
power supply voltage Vs that is supplied from the
commercial power supply 110 and outputs the power rectified.
15 The rectification unit 130 performs full-wave rectification.
The reactor 120 is connected between the rectification unit
130 and the boost unit 600. The boost unit 600 includes a
switching element 611 and a rectifier element 621. The
boost unit 600 turns on and off the switching element 611
20 under control of the control unit 400, boosts the power
output from the rectification unit 130, and outputs the
boosted power to the smoothing unit 200. In the present
embodiment, the control unit 400 performs on the boost unit
600 full pulse amplitude modulation (PAM) control that
25 continuously switches the switching element 611. With the
boost unit 600, the power conversion apparatus 1a performs
power factor improvement control for the commercial power
supply 110 and causes a capacitor voltage Vdc across a
capacitor 210 of the smoothing unit 200 to be higher than
30 the power supply voltage Vs. With the rectification unit
130 and the boost unit 600, the rectification and boost
unit 700 rectifies the first alternating-current power
supplied from the commercial power supply 110 and boosts

7
the voltage of the first alternating-current power supplied
from the commercial power supply 110. In the rectification
and boost unit 700 according to the present embodiment, the
rectification unit 130 and the boost unit 600 are connected
5 in series.
[0012] The voltage detection unit 502 detects a voltage
value of the power boosted by the boost unit 600 and
outputs the detected voltage value to the control unit 400.
The smoothing unit 200 is connected to output terminals of
10 the boost unit 600 via the voltage detection unit 502. The
smoothing unit 200 includes a capacitor 210 as a smoothing
element and smooths the power boosted by the boost unit 600.
Examples of the capacitor 210 include an electrolytic
capacitor and a film capacitor, among others. The
15 capacitor 210 has such capacitance as to smooth the power
rectified by the rectification unit 130. The smoothing
causes voltage across the capacitor 210 to not assume a
full-wave rectified waveform of the commercial power supply
110, but a waveform that includes a direct-current
20 component with voltage ripple based on a frequency of the
commercial power supply 110 superimposed and does not
pulsate significantly. A main frequency component of this
voltage ripple is a component that is double the frequency
of the power supply voltage Vs when the commercial power
25 supply 110 is single-phase or six times the frequency of
the power supply voltage Vs when the commercial power
supply 110 is three-phase. If the power input from the
commercial power supply 110 and the power that is output
from the inverter 310 do not change, the amplitude of this
30 voltage ripple is determined by the capacitance of the
capacitor 210. For example, the voltage ripple generated
across the capacitor 210 pulsates in a range such that its
maximum value is less than twice its minimum value.

8
[0013] The inverter 310 is connected across the
smoothing unit 200, namely the capacitor 210. The inverter
310 includes switching elements 311a to 311f and
freewheeling diodes 312a to 312f. The inverter 310 turns
5 on and off the switching elements 311a to 311f under
control of the control unit 400, converts power output from
the rectification and boost unit 700 and the smoothing unit
200 into the second alternating-current power that has the
desired amplitude and the desired phase, and outputs the
10 second alternating-current power to the compressor 315.
Each of the current detection units 313a and 313b detects a
value of one of three phase currents that are output from
the inverter 310 and outputs the detected current value to
the control unit 400. By obtaining the values of the two
15 phase currents of the values of three phase currents that
are output from the inverter 310, the control unit 400 is
enabled to calculate a value of a remaining one of the
three phase currents that are output from the inverter 310.
The compressor 315 is a load including the motor 314 that
20 drives a compression mechanism. The motor 314 rotates
according to the amplitude and the phase of the second
alternating-current power supplied from the inverter 310,
effecting compression operation. If, for example, the
compressor 315 is a hermetic compressor that is used in an
25 air conditioner or another apparatus, load torque of the
compressor 315 can often be considered a constant torque
load.
[0014] The arrangement of the configurations that is
illustrated in FIG. 1 is an example. The power conversion
30 apparatus 1a is not limited to the example arrangement of
the configurations that is illustrated in FIG. 1. The
rectification and boost unit 700 does not have to include
the reactor 120, depending where the reactor 120 is

9
disposed. In a description below, the voltage and current
detection unit 501, the voltage detection unit 502, and the
current detection units 313a and 313b may all be referred
to as the detection units. The voltage and current values
5 detected by the voltage and current detection unit 501, the
voltage value detected by the voltage detection unit 502,
and the current values detected by the current detection
units 313a and 313b may be referred to as the detection
values.
10 [0015] The control unit 400 obtains the voltage and
current values of the first alternating-current power at
the power supply voltage Vs from the voltage and current
detection unit 501, the voltage value of the power boosted
by the boost unit 600 from the voltage detection unit 502,
15 and the current values of the second alternating-current
power with the desired amplitude and the desired phase that
has been obtained as a result of the conversion by the
inverter 310 from the current detection units 313a and 313b.
The control unit 400 uses the detection values detected by
20 the detection units in controlling the operation of the
boost unit 600 of the rectification and boost unit 700 or,
more specifically, the on and off switching of the
switching element 611 of the boost unit 600. Moreover, the
control unit 400 uses the detection values detected by the
25 detection units in controlling the operation of the
inverter 310 or, more specifically, the on and off
switching of the switching elements 311a to 311f of the
inverter 310. In the present embodiment, the control unit
400 controls the operation of the rectification and boost
30 unit 700. The control unit 400 performs the power factor
improvement control on the first alternating-current power
supplied from the commercial power supply 110 and average
voltage control for the capacitor 210 of the smoothing unit

10
200 through the operation control of the rectification and
boost unit 700. Moreover, the control unit 400 performs
the operation control on the inverter 310 to cause the
second alternating-current power that includes a pulsation
5 based on a pulsation of the power that flows into the
capacitor 210 of the smoothing unit 200 from the
rectification unit 130 to be output from the inverter 310
to the compressor 315, which is the load. The pulsation
based on the pulsation of the power that flows into the
10 capacitor 210 of the smoothing unit 200 refers to, for
example, a pulsation that changes depending on, for example,
a frequency of the pulsation of the power that flows into
the capacitor 210 of the smoothing unit 200. In this way,
the control unit 400 restrains a current that flows into
15 the capacitor 210 of the smoothing unit 200. The control
unit 400 does not have to use all the detection values
obtained from the detection units. The control unit 400
may use part of the detection values in the control.
[0016] A description is provided next of how the control
20 unit 400 of the power conversion apparatus 1a operates. In
the power conversion apparatus 1a according to the present
embodiment, a load that is generated by the inverter 310
and the compressor 315 can be regarded as the constant load.
A description below is based on the assumption that a
25 constant current load is connected to the smoothing unit
200 when viewed in terms of a current that is output from
the smoothing unit 200. Herein, as illustrated in FIG. 1,
a current that flows from the boost unit 600 refers to the
current I1, a current that flows into the inverter 310
30 refers to the current I2, and the current that flows from
the smoothing unit 200 refers to the current I3. The
current I2 is the current as a combination of the current
I1 and the current I3. The current I3 can be expressed as

11
a difference between the current I2 and the current I1,
that is to say, the current I2 minus the current I1. The
current I3 has a positive direction in a discharge
direction of the smoothing unit 200 and a negative
5 direction in a charge direction of the smoothing unit 200.
In other words, there are cases where the current flows
into and flows out of the smoothing unit 200.
[0017] FIG. 2 is a diagram illustrating examples of the
currents I1 to I3 and an example of the capacitor voltage
10 Vdc across the capacitor 210 in the smoothing unit 200 in a
comparative example in which the current output from the
boost unit 600 has been smoothed by the smoothing unit 200,
causing the current I2 that flows into the inverter 310 to
be constant. The current I1, the current I2, the current
15 I3, and the capacitor voltage Vdc that is generated across
the capacitor 210 in accordance with the current I3 are
illustrated from the top in this order. A vertical axis
for each of the currents I1, I2, and I3 represents the
current value, and a vertical axis for the capacitor
20 voltage Vdc represents the voltage value. Every horizontal
axis represents time t. Although a carrier component of
the inverter 310 is actually superimposed on the currents
I2 and I3, this is omitted here. The same applies to what
follows. As illustrated in FIG. 2, if the current I1 that
25 flows from the boost unit 600 has been smoothed enough by
the smoothing unit 200 in the power conversion apparatus 1a,
the current I2 that flows into the inverter 310 becomes a
constant current value. However, the current I3 that flows
into the capacitor 210 of the smoothing unit 200 is large
30 and causes degradation of the capacitor 210. Therefore,
the control unit 400 of the power conversion apparatus 1a
according to the present embodiment controls the current I2
that flows into the inverter 310, that is to say, controls

12
the operation of the inverter 310 in order to reduce the
current I3 that flows into the smoothing unit 200.
[0018] FIG. 3 is a diagram illustrating examples of the
currents I1 to I3 and an example of the capacitor voltage
5 Vdc across the capacitor 210 in the smoothing unit 200 when
the control unit 400 of the power conversion apparatus 1a
according to the first embodiment has reduced the current
I3 that flows into the smoothing unit 200 through the
operation control of the inverter 310. The current I1, the
10 current I2, the current I3, and the capacitor voltage Vdc
that is generated across the capacitor 210 in accordance
with the current I3 are illustrated from the top in this
order. A vertical axis for each of the currents I1, I2,
and I3 represents the current value, and a vertical axis
15 for the capacitor voltage Vdc represents the voltage value.
Every horizontal axis represents time t. Through the
operation control of the inverter 310 to cause the current
I2, such as illustrated in FIG. 3, to flow into the
inverter 310, the control unit 400 of the power conversion
20 apparatus 1a is capable of reducing frequency components in
the current that flows into the smoothing unit 200 from the
boost unit 600, thus reducing the current I3 that flows
into the smoothing unit 200, as compared with the example
of FIG. 2. Specifically, the control unit 400 performs the
25 operation control on the inverter 310 to cause the current
I2 that includes a pulsating current whose main component
is a frequency component of the current I1 to flow into the
inverter 310.
[0019] The frequency component of the current I1 is
30 determined by a frequency of an alternating current
supplied from the commercial power supply 110, the
configuration of the rectification unit 130, and a
switching speed of the switching element 611 in the boost

13
unit 600. Therefore, the control unit 400 enables a
frequency component of the pulsating current that is
superimposed on the current I2 to be a component having a
predetermined amplitude and a predetermined phase. The
5 frequency component of the pulsating current that is
superimposed on the current I2 has a waveform similar to
that of the frequency component of the current I1. As the
control unit 400 brings the frequency component of the
pulsating current that is superimposed on the current I2
10 closer to the frequency component of the current I1, the
control unit 400 enables the current I3 that flows into the
smoothing unit 200 to reduce and enables a pulsating
voltage that is generated in the capacitor voltage Vdc to
reduce.
15 [0020] The pulsation control of the current that flows
into the inverter 310 by the control unit 400 through the
operation control of the inverter 310 is equivalent to
pulsation control of the second alternating-current power
that is output from the inverter 310 to the compressor 315.
20 Through the operation control of the inverter 310, the
control unit 400 causes the pulsation included in the
second alternating-current power that is output from the
inverter 310 to become smaller than the pulsation of the
power that is output from the rectification and boost unit
25 700. In order for the voltage ripple of the capacitor
voltage Vdc, namely the voltage ripple generated across the
capacitor 210 to be smaller than voltage ripple that will
be generated across the capacitor 210 if the second
alternating-current power that is output from the inverter
30 310 does not include the pulsation based on the pulsation
of the power that flows into the capacitor 210, the control
unit 400 performs amplitude and phase control on the
pulsation included in the second alternating-current power

14
that is output from the inverter 310. The case where the
second alternating-current power that is output from the
inverter 310 does not include the pulsation based on the
pulsation of the power that flows into the capacitor 210
5 refers to control, such as illustrated in FIG. 2.
[0021] The alternating current that is supplied from the
commercial power supply 110 is not particularly limited and
may be single-phase or three-phase. The control unit 400
only has to determine the frequency component of the
10 pulsating current that is superimposed on the current I2 on
the basis of the first alternating-current power that is
supplied from the commercial power supply 110.
Specifically, the control unit 400 controls a pulsating
waveform of the current I2 that flows into the inverter 310
15 to a shape obtained by adding a direct-current component to
a pulsating waveform whose main component is a frequency
component that is double a frequency of the first
alternating-current power if the first alternating-current
power that is supplied from the commercial power supply 110
20 is single-phase or six times the frequency of the first
alternating-current power if the first alternating-current
power that is supplied from the commercial power supply 110
is three-phase. The pulsating waveform is, for example, a
shape defined by absolute values of a sine wave or sine
25 wave-shaped. In this case, the control unit 400 may add at
least one of frequency components that are integer
multiples of a frequency of the sine wave as a prespecified
amplitude to the pulsating waveform. The pulsating
waveform may be rectangular wave-shaped or triangular-wave
30 shaped. In this case, the control unit 400 may set
amplitude and phase of the pulsating waveform as
prespecified values.
[0022] The control unit 400 may use the voltage across

15
the capacitor 210 or the current flowing into the capacitor
210 in calculating a pulsating quantity of the pulsation to
be included in the second alternating-current power, which
is output from the inverter 310, or may use the voltage or
5 the current of the first alternating-current power supplied
from the commercial power supply 110 in calculating a
pulsating quantity of the pulsation to be included in the
second alternating-current power, which is output from the
inverter 310.
10 [0023] When causing, through the control of the inverter
310, the second alternating-current power that includes a
frequency component different from a frequency component of
the first alternating-current power that is supplied from
the commercial power supply 110 to be output from the
15 inverter 310 to the compressor 315, the control unit 400
may superimpose, on a drive signal that turns on and off
the switching element 611 of the boost unit 600, the
frequency component to be included in the second
alternating-current power that is output from the inverter
20 310 to the compressor 315. In other words, the control
unit 400 performs the operation control on the
rectification and boost unit 700 or, more specifically, the
operation control on the switching element 611 of the boost
unit 600 to cause the power that includes the variable
25 frequency component among power pulsations of the second
alternating-current power that is output from the inverter
310 to the compressor 315 to be output from the
rectification and boost unit 700. The variable frequency
component is other than the frequency component that is
30 double the frequency of the first alternating-current power
if the first alternating-current power that is supplied
from the commercial power supply 110 is single-phase or six
times the frequency of the first alternating-current power

16
if the first alternating-current power that is supplied
from the commercial power supply 110 is three-phase. The
control unit 400 may control the variable frequency
component with a command value for the commercial power
5 supply 110. The variable frequency component may be
controlled by the control unit 400 not to be up to a 40th
order component that is an integer multiple of the
frequency of the first alternating-current power supplied
from the commercial power supply 110 or to be less than or
10 equal to a specified value (for example, a desired standard
value).
[0024] With reference to a flowchart, a description is
provided of the operation of the control unit 400. FIG. 4
is a flowchart illustrating the operation of the control
15 unit 400 of the power conversion apparatus 1a according to
the first embodiment. The control unit 400 obtains
detection values from the detection units of the power
conversion apparatus 1a (step S1). On the basis of the
obtained detection values, the control unit 400 performs,
20 on the inverter 310, the operation control that reduces the
current I3 that flows into the smoothing unit 200 (step S2).
On the basis of the obtained detection values, the control
unit 400 performs the operation control on the boost unit
600 to perform the power factor improvement control for the
25 commercial power supply 110 and the average voltage control
on the capacitor voltage Vdc across the capacitor 210 of
the smoothing unit 200 (step S3).
[0025] A description is provided next of a hardware
configuration of the control unit 400 of the power
30 conversion apparatus 1a. FIG. 5 is a diagram illustrating
an example of the hardware configuration that implements
the control unit 400 of the power conversion apparatus 1a
according to the first embodiment. The control unit 400 is

17
implemented with a processor 91 and a memory 92.
[0026] The processor 91 is a central processing unit
(CPU) (also referred to as a processing unit, an arithmetic
unit, a microprocessor, a microcomputer, a processor, or a
5 digital signal processor (DSP)) or a system large-scale
integration (LSI). The memory 92 is, for example, a
nonvolatile or volatile semiconductor memory such as a
random-access memory (RAM), a read-only memory (ROM), a
flash memory, an erasable programmable read-only memory
10 (EPROM), or an electrically erasable programmable read-only
memory (EEPROM) (registered trademark). The memory 92 is
not limited to these and may be a magnetic disk, an optical
disk, a compact disk, a mini disk, or a digital versatile
disc (DVD).
15 [0027] As described above, according to the present
embodiment, the control unit 400 of the power conversion
apparatus 1a performs the operation control on the inverter
310 on the basis of the detection values obtained from the
detection units to superimpose the pulsating frequency
20 component based on the frequency component of the current
I1 flowing from the rectification unit 130 on the current
I2 that flows into the inverter 310, thus reducing the
current I3 that flows into the smoothing unit 200. Since
the current I3 that flows into the smoothing unit 200 is
25 reduced thus, the power conversion apparatus 1a is enabled
to use a capacitor with a smaller tolerance to ripple
current than in a case where the control according to the
present embodiment is not performed. Since the power
conversion apparatus 1a reduces the pulsating voltage in
30 the capacitor voltage Vdc, the capacitor 210 to be
installed is enabled to have a smaller capacitance than in
the case where the control according to the present
embodiment is not performed. In cases where, for example,

18
the smoothing unit 200 includes a plurality of the
capacitors 210, the power conversion apparatus 1a enables
the smoothing unit 200 to have a reduced number of
capacitors 210.
5 [0028] Since the pulsation included in the second
alternating-current power is caused, through the operation
control of the inverter 310, to become smaller than the
pulsation of the power that is output from the
rectification unit 130, the power conversion apparatus 1
10 enables the pulsating component superimposed on the current
I2 that flows into the inverter 310 to be restrained from
becoming excessive. Superimposing the pulsating component
increases an effective value of the current that passes
through, for example, the inverter 310 and the motor 314
15 compared to a state in which the pulsating component is not
superimposed. However, the pulsating component to be
superimposed is restrained from becoming excessive, thus
enabling provision of a system that restrains current
capacity of the inverter 310, loss increase in the inverter
20 310 and loss increase in the motor 314, among others.
[0029] With the control according to the present
embodiment, the power conversion apparatus 1a is capable of
restraining vibration of the compressor 315 that is caused
by the pulsation of the current I2.
25 [0030] Since the boosting by the boost unit 600
increases the capacitor voltage Vdc across the capacitor
210, the power conversion apparatus 1a enables the inverter
310 to have a wider output voltage range. The control unit
400 of the power conversion apparatus 1a superimposes the
30 pulsating frequency component that is included in the
second alternating-current power to be output from the
inverter 310 on the drive signal for the switching element
611 of the boost unit 600. In this way, the control unit

19
400 is capable of reducing pulsations of the current I3 and
the capacitor voltage Vdc that are caused by this frequency
component.
[0031] Second Embodiment.
5 In a second embodiment, a description is provided of a
power conversion apparatus including a rectification and
boost unit that has a circuit configuration different from
that of the rectification and boost unit 700 of the power
conversion apparatus 1a according to the first embodiment.
10 [0032] FIG. 6 is a diagram illustrating an exemplary
configuration of the power conversion apparatus 1b
according to the second embodiment. Compared with the
power conversion apparatus 1a according to the first
embodiment illustrated in FIG. 1, the power conversion
15 apparatus 1b has the rectification and boost unit 701 in
place of the rectification and boost unit 700. The power
conversion apparatus 1b and the motor 314 that is included
in the compressor 315 compose a motor drive apparatus 2b.
The rectification and boost unit 701 includes the switching
20 elements 611 to 614, and those rectifier elements 621 to
624 that are connected in parallel with the switching
elements 611 to 614, respectively. The rectification and
boost unit 701 turns on and off the switching elements 611
to 614 under control of the control unit 400, rectifies and
25 boosts a first alternating-current power output from the
commercial power supply 110, and outputs the boosted power
to the smoothing unit 200. In the present embodiment, the
control unit 400 performs on the rectification and boost
unit 701 full PAM control that continuously switches the
30 switching elements 611 to 614. With the rectification and
boost unit 701, the power conversion apparatus 1b performs
power factor improvement control for the commercial power
supply 110 and causes the capacitor voltage Vdc across the

20
capacitor 210 of the smoothing unit 200 to be higher than
the power supply voltage Vs.
[0033] The control unit 400 obtains a voltage value and
a current value of the first alternating-current power at
5 the power supply voltage Vs from the voltage and current
detection unit 501, a voltage value of the power boosted by
the rectification and boost unit 701 from the voltage
detection unit 502, and current values of a second
alternating-current power with a desired amplitude and a
10 desired phase that has been obtained as a result of
conversion by the inverter 310 from the current detection
units 313a and 313b. The control unit 400 uses the
detection values detected by the detection units in
controlling the operation of the inverter 310 or, more
15 specifically, the on and off switching of the switching
elements 311a to 311f of the inverter 310. Moreover, the
control unit 400 uses the detection values detected by the
detection units in controlling the operation of the
rectification and boost unit 701 or, more specifically, the
20 on and off switching of the switching elements 611 to 614
of the rectification and boost unit 701. By performing the
operation controls on the rectification and boost unit 701
and the inverter 310, the control unit 400 obtains the same
effects as described in the first embodiment.
25 [0034] The power conversion apparatus 1b otherwise
operates similarly to the power conversion apparatus 1a
according to the first embodiment. In this case, the power
conversion apparatus 1b is also capable of obtaining the
same effects as the power conversion apparatus 1a according
30 to the first embodiment.
[0035] Third Embodiment.
In a third embodiment, a description is provided of a
power conversion apparatus including a rectification and

21
boost unit that has a circuit configuration different from
the circuit configurations of the rectification and boost
unit 700 of the power conversion apparatus 1a according to
the first embodiment and the rectification and boost unit
5 701 of the power conversion apparatus 1b according to the
second embodiment.
[0036] FIG. 7 is a diagram illustrating an exemplary
configuration of the power conversion apparatus 1c
according to the third embodiment. Compared with the power
10 conversion apparatus 1a according to the first embodiment
illustrated in FIG. 1, the power conversion apparatus 1c
has the rectification and boost unit 702 in place of the
rectification and boost unit 700. The power conversion
apparatus 1c and the motor 314 that is included in the
15 compressor 315 compose a motor drive apparatus 2c. The
rectification and boost unit 702 includes the reactor 120,
the rectification unit 130, and a boost unit 601. While
the boost unit 600 is connected downstream of the
rectification unit 130, that is to say, in series with the
20 rectification unit 130 in the power conversion apparatus 1a
according to the first embodiment, the boost unit 601 is
connected in parallel with the rectification unit 130 in
the power conversion apparatus 1c according to the third
embodiment. The boost unit 601 includes the rectifier
25 elements 621 to 624 and the switching element 611. The
boost unit 601 turns on and off the switching element 611
under control of the control unit 400, boosts a first
alternating-current power output from the commercial power
supply 110, and outputs the boosted power to the
30 rectification unit 130. In the present embodiment, the
control unit 400 performs, on the boost unit 601 of the
rectification and boost unit 702, simple switching control
that switches the switching element 611 one or more times

22
in a half cycle of a frequency of the first alternatingcurrent power supplied from the commercial power supply 110.
With the boost unit 601, the power conversion apparatus 1c
performs power factor improvement control for the
5 commercial power supply 110 and causes the capacitor
voltage Vdc across the capacitor 210 of the smoothing unit
200 to be higher than the power supply voltage Vs.
[0037] The control unit 400 obtains the voltage and
current values of the first alternating-current power at
10 the power supply voltage Vs from the voltage and current
detection unit 501, the voltage value of the power
rectified by the rectification unit 130 from the voltage
detection unit 502, and the current values of the second
alternating-current power with the desired amplitude and
15 the desired phase that has been obtained as a result of the
conversion by the inverter 310 from the current detection
units 313a and 313b. The control unit 400 uses the
detection values detected by the detection units in
controlling the operation of the inverter 310 or, more
20 specifically, the on and off switching of the switching
elements 311a to 311f of the inverter 310. Moreover, the
control unit 400 uses the detection values detected by the
detection units in controlling the operation of the boost
unit 601 or, more specifically, the on and off switching of
25 the switching element 611 of the boost unit 601. By
performing the operation controls on the boost unit 601 and
the inverter 310, the control unit 400 obtains the same
effects as described in the first embodiment.
[0038] The power conversion apparatus 1c otherwise
30 operates similarly to the power conversion apparatus 1a
according to the first embodiment. In this case, the power
conversion apparatus 1c is also capable of obtaining the
same effects as the power conversion apparatus 1a according

23
to the first embodiment. Compared with the power
conversion apparatus 1a according to the first embodiment
and the power conversion apparatus 1b according to the
second embodiment, the number of times the switching is
5 performed is small in the power conversion apparatus 1c,
thus the power conversion apparatus 1c enables reduced loss
and reduced noise. Since the rectification unit 130 and
the boost unit 601 are connected in parallel, when no
switching of the switching element 611 takes place in the
10 boost unit 601 under the condition that the switching is
unnecessary, the power conversion apparatus 1c has a
smaller number of elements for conduction, enabling reduced
loss.
[0039] Fourth Embodiment.
15 FIG. 8 is a diagram illustrating an exemplary
configuration of a refrigeration cycle apparatus 900
according to a fourth embodiment. The refrigeration cycle
apparatus 900 according to the fourth embodiment includes
the power conversion apparatus 1a described in the first
20 embodiment. The refrigeration cycle apparatus 900 may
include the power conversion apparatus 1b described in the
second embodiment or the power conversion apparatus 1c
described in the third embodiment in place of the power
conversion apparatus 1a. The refrigeration cycle apparatus
25 900 according to the fourth embodiment is applicable to a
product with a refrigeration cycle, such as an air
conditioner, a refrigerator, a freezer, or a heat pump
water heater. In FIG. 8, constituent elements with the
same functions as those in the first embodiment have the
30 same reference characters as in the first embodiment.
[0040] The refrigeration cycle apparatus 900 has the
compressor 315 with the internal motor 314 in the first
embodiment, a four-way valve 902, an indoor heat exchanger

24
906, an expansion valve 908, and an outdoor heat exchanger
910 connected via refrigerant piping 912.
[0041] The compressor 315 internally includes a
compression mechanism 904 that compresses a refrigerant and
5 the motor 314 that runs the compression mechanism 904.
[0042] The refrigeration cycle apparatus 900 is capable
of operating for heating or cooling through switching
operation of the four-way valve 902. The compression
mechanism 904 is driven by the motor 314 that is controlled
10 at variable speed.
[0043] In the operation for heating, as indicated by
solid line arrows, the refrigerant is pressurized and
discharged by the compression mechanism 904 and returns to
the compression mechanism 904 through the four-way valve
15 902, the indoor heat exchanger 906, the expansion valve 908,
the outdoor heat exchanger 910, and the four-way valve 902.
[0044] In the operation for cooling, as indicated by
dashed line arrows, the refrigerant is pressurized and
discharged by the compression mechanism 904 and returns to
20 the compression mechanism 904 through the four-way valve
902, the outdoor heat exchanger 910, the expansion valve
908, the indoor heat exchanger 906, and the four-way valve
902.
[0045] In the operation for heating, the indoor heat
25 exchanger 906 acts as a condenser to release heat, and the
outdoor heat exchanger 910 acts as an evaporator to absorb
heat. In the operation for cooling, the outdoor heat
exchanger 910 acts as a condenser to release heat, and the
indoor heat exchanger 906 acts as an evaporator to absorb
30 heat. The expansion valves 908 depressurizes and expands
the refrigerant.
[0046] The above configurations illustrated in the
embodiments are illustrative, can be combined with other

25
techniques that are publicly known, and can be partly
omitted or changed without departing from the gist. The
embodiments can be combined together.
5 Reference Signs List
[0047] 1a, 1b, 1c power conversion apparatus; 2a, 2b,
2c motor drive apparatus; 110 commercial power supply;
120 reactor; 130 rectification unit; 131 to 134, 621 to
624 rectifier element; 200 smoothing unit; 210 capacitor;
10 310 inverter; 311a to 311f, 611 to 614 switching element;
312a to 312f freewheeling diode; 313a, 313b current
detection unit; 314 motor; 315 compressor; 400 control
unit; 501 voltage and current detection unit; 502 voltage
detection unit; 600, 601 boost unit; 700, 701, 702
15 rectification and boost unit; 900 refrigeration cycle
apparatus; 902 four-way valve; 904 compression mechanism;
906 indoor heat exchanger; 908 expansion valve; 910
outdoor heat exchanger; 912 refrigerant piping.

We Claim:
[Claim 1] A power conversion apparatus comprising:
5 a rectification and boost unit rectifying a first
alternating-current power supplied from a commercial power
supply and boosting a voltage of the first alternatingcurrent power;
a capacitor connected to output terminals of the
10 rectification and boost unit;
an inverter that is connected across the capacitor,
converts power output from the rectification and boost unit
and the capacitor into a second alternating-current power,
and outputs the second alternating-current power to a load
15 including a motor; and
a control unit performing operation control on the
rectification and boost unit, and performing operation
control on the inverter to cause the second alternatingcurrent power that includes a pulsation based on a
20 pulsation of power that flows into the capacitor from the
rectification and boost unit to be output from the inverter
to the load, to restrain a current that flows into the
capacitor.
25 [Claim 2] The power conversion apparatus according to claim
1, wherein
the control unit performs power factor improvement
control on the first alternating-current power supplied
from the commercial power supply and average voltage
30 control for the capacitor through operation control of the
rectification and boost unit.
[Claim 3] The power conversion apparatus according to claim

27
1 or 2, wherein
the control unit performs operation control on the
inverter to cause a pulsation included in the second
alternating-current power that is output from the inverter
5 to become smaller than a pulsation of power that is output
from the rectification and boost unit.
[Claim 4] The power conversion apparatus according to any
one of claims 1 to 3, wherein
10 the control unit performs amplitude and phase control
on a pulsation included in the second alternating-current
power that is output from the inverter to cause voltage
ripple generated across the capacitor to be smaller than
voltage ripple that is generated across the capacitor if
15 the second alternating-current power that is output from
the inverter does not include a pulsation based on a
pulsation of power that flows into the capacitor.
[Claim 5] The power conversion apparatus according to any
20 one of claims 1 to 4, wherein
the control unit performs amplitude and phase control
on a pulsation included in the second alternating-current
power that is output from the inverter to cause current
ripple that flows into and out of the capacitor to be
25 smaller than current ripple that is generated through the
capacitor if the second alternating-current power that is
output from the inverter does not include a pulsation based
on a pulsation of power that flows into the capacitor.
30 [Claim 6] The power conversion apparatus according to any
one of claims 1 to 5, wherein
the rectification and boost unit includes
a rectification unit including a plurality of

28
rectifier elements, and
a boost unit including a rectifier element and a
switching element that is turned on and off under control
of the control unit, and
5 the rectification unit and the boost unit are
connected in series or parallel.
[Claim 7] The power conversion apparatus according to any
one of claims 1 to 5, wherein
10 the rectification and boost unit includes
a plurality of switching elements that are turned on
and off under control of the control unit, and
a plurality of rectifier elements connected in
parallel with the plurality of switching elements,
15 respectively.
[Claim 8] The power conversion apparatus according to any
one of claims 1 to 7, wherein
the control unit performs operation control on the
20 rectification and boost unit to cause the power that
includes a variable frequency component among pulsations
included in the second alternating-current power that is
output from the inverter to be output from the
rectification and boost unit, the variable frequency
25 component being other than a frequency component that is
double a frequency of the first alternating-current power
if the first alternating-current power is single-phase or
six times a frequency of the first alternating-current
power if the first alternating-current power is three-phase.
30
[Claim 9] The power conversion apparatus according to claim
8, wherein

29
the control unit controls the variable frequency
component with a command value for the commercial power
supply.
5 [Claim 10] The power conversion apparatus according to
claim 8, wherein
the variable frequency component is controlled by the
control unit to be prevented from being up to a 40th order
component that is an integer multiple of a frequency of the
10 first alternating-current power or to be less than or equal
to a specified value.
[Claim 11] The power conversion apparatus according to
any one of claims 1 to 10, wherein
15 the capacitor is an electrolytic capacitor or a film
capacitor.
[Claim 12] The power conversion apparatus according to
any one of claims 1 to 11, wherein
20 voltage ripple generated across the capacitor has a
maximum value less than twice a minimum value of the
voltage ripple.
[Claim 13] The power conversion apparatus according to
25 any one of claims 1 to 12, wherein
the rectification and boost unit performs full-wave
rectification, and a voltage generated across the capacitor
assumes a shape that is not a full-wave rectified waveform
of the commercial power supply.
30
[Claim 14] A motor drive apparatus comprising the power
conversion apparatus according to any one of claims 1 to 13.

[Claim 15] A refrigeration cycle apparatus comprising
the power conversion apparatus according to any one of
claims 1 to 13.
5