U.S. patent application number 14/329425 was filed with the patent office on 2014-10-30 for converter circuit and motor drive control apparatus, air-conditioner, refrigerator, and induction heating cooker provided with the circuit.
This patent application is currently assigned to MITSUBISHI ELECTRIC CORPORATION. The applicant listed for this patent is MITSUBISHI ELECTRIC CORPORATION. Invention is credited to Kazunori Hatakeyama, Kazunori Sakanobe, Takuya SHIMOMUGI, Yosuke Shinomoto, Michio Yamada.
Application Number | 20140320059 14/329425 |
Document ID | / |
Family ID | 41721157 |
Filed Date | 2014-10-30 |
United States Patent
Application |
20140320059 |
Kind Code |
A1 |
SHIMOMUGI; Takuya ; et
al. |
October 30, 2014 |
CONVERTER CIRCUIT AND MOTOR DRIVE CONTROL APPARATUS,
AIR-CONDITIONER, REFRIGERATOR, AND INDUCTION HEATING COOKER
PROVIDED WITH THE CIRCUIT
Abstract
A converter circuit capable of being compact and light-weight
and capable of reducing switching loss, a motor drive control
apparatus, an air-conditioner, a refrigerator, and an induction
heating cooker provided with the circuit. The converter circuit
including: a step-up converter including a rectifier, a step-up
reactor, a switching element, and a reverse current prevention
element; a step-up converter having a step-up reactor, a switching
element, and a reverse current prevention element and connected in
parallel with the step-up converter; switching control unit that
controls switching elements; and a smoothing capacitor that is
provided at the output of the step-up converters. The switching
control unit switches the current mode of the current flowing
through the step-up reactors into any of a continuous mode, a
critical mode, and a discontinuous mode based on a predetermined
condition.
Inventors: |
SHIMOMUGI; Takuya; (Tokyo,
JP) ; Shinomoto; Yosuke; (Tokyo, JP) ;
Sakanobe; Kazunori; (Tokyo, JP) ; Yamada; Michio;
(Tokyo, JP) ; Hatakeyama; Kazunori; (Tokyo,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MITSUBISHI ELECTRIC CORPORATION |
Chiyoda-ku |
|
JP |
|
|
Assignee: |
MITSUBISHI ELECTRIC
CORPORATION
Tokyo
JP
|
Family ID: |
41721157 |
Appl. No.: |
14/329425 |
Filed: |
July 11, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13058401 |
Feb 10, 2011 |
8817506 |
|
|
PCT/JP2009/055109 |
Mar 17, 2009 |
|
|
|
14329425 |
|
|
|
|
Current U.S.
Class: |
318/801 ;
363/89 |
Current CPC
Class: |
H05B 6/06 20130101; Y02B
70/10 20130101; H02M 7/06 20130101; H02M 1/4225 20130101; Y02B
70/126 20130101; H02M 2003/1586 20130101; H02P 27/06 20130101; H02M
3/1584 20130101 |
Class at
Publication: |
318/801 ;
363/89 |
International
Class: |
H02M 7/06 20060101
H02M007/06; H02P 27/06 20060101 H02P027/06 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 1, 2008 |
JP |
2008-223646 |
Claims
1-8. (canceled)
9. A converter circuit, comprising: a rectifier that rectifies an
AC voltage; at least a converter section that is connected with an
output of said rectifier and has a reactor, a switching element,
and a reverse current prevention element; switching control means
that controls said switching element; and a smoothing capacitor
that is provided at an output of said converter section, wherein at
a predetermined value or in a predetermined range of an output
voltage of said converter section, a current mode of a current
flowing through said reactor is controlled by said switching
control means and is one of at least two modes among a critical
mode, a discontinuous mode, and a continuous mode.
10. The converter circuit of claim 9, further comprising: one or
more converter sections that are connected with the output of said
rectifier, each of the one or more converter sections has a
reactor, a switching element, and a reverse current prevention
element, and each of the one or more converter sections is
connected with said at least one converter section in parallel.
11. The converter circuit of claim 10, wherein said switching
control means controls switching of said switching element and said
switching element in each of the one or more converter sections so
as to create a predetermined phase difference in the current
flowing through said reactor and said reactor in each of the one or
more converter sections.
12. The converter circuit of claim 11, wherein said switching
control means controls switching of said switching element and said
switching element in each of the one or more converter sections so
that the phase difference of the currents flowing through said
reactor and said reactor in each of the one or more converter
sections randomly varies within a predetermined range.
13. A motor drive control apparatus, comprising: the converter
circuit of claim 9; an inverter circuit that converts a DC output
voltage of said converter circuit to an AC voltage; and inverter
drive means that drives said inverter circuit.
14. An air-conditioner, comprising: the motor drive control
apparatus of claim 13; and a motor that is driven by said motor
drive control apparatus.
15. A refrigerator, comprising: the motor drive control apparatus
of claim 13; and a motor that is driven by said motor drive control
apparatus.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of prior
application Ser. No. 13/058,401 filed Feb. 10, 2011, which is a
National Stage of Application No. PCT/JP2009/055109 filed Mar. 17,
2009, the entire contents of each of which are incorporated by
reference herein.
TECHNICAL FIELD
[0002] The present invention relates to a converter circuit and a
motor drive control apparatus, an air-conditioner, a refrigerator,
and an induction heating cooker provided with the circuit.
BACKGROUND ART
[0003] Conventionally, a step-down converter and a
step-up/step-down converter as well as a step-up converter are
usually used as a power factor correction (PFC) circuit.
[0004] In order to achieve a small and light-weighted converter
circuit, a converter circuit is proposed including "a rectification
circuit whose input is an AC power source, a first step-up
converter circuit connected to the output of the rectification
circuit and having at least a first reactor, first switching means
and a first diode, a second step-up converter circuit connected to
the first step-up converter circuit in parallel and having at least
a second reactor, second switching means and a second diode, and a
smoothing capacitor connected to outputs of the first step-up
converter circuit and the second step-up converter circuit." (For
example, refer to Patent Literature 1) [0005] Patent Literature 1:
Japanese Patent No. 2008-86107 (claim 1)
SUMMARY OF INVENTION
Technical Problem
[0006] When employing a step-up converter, or a step-down converter
and a step-up/step-down converter as a power factor correction
circuit, it is necessary to operate a current flowing through a
reactor as a continuous mode. Therefore, the reactor having a large
inductance is needed and a small and light-weighted circuit cannot
be achieved disadvantageously.
[0007] With a configuration in which a plurality of systems of a
converter circuit is connected in parallel, switching loss becomes
large disadvantageously.
[0008] The present invention is made to solve the above-mentioned
problems and its object is to provide a small light-weighted
converter circuit capable of reducing switching loss and a motor
drive control apparatus, an air-conditioner, a refrigerator, and an
induction heating cooker having the circuit.
Solution to Problem
[0009] The converter circuit according to the present invention
includes a rectifier to rectify AC voltages, a first converter
section that is connected with the output of the rectifier and has
a first reactor, a first switching element, and a first reverse
current prevention element, a second converter section that is
connected with the output of the rectifier, that has a second
reactor, a second switching element, and a second reverse current
prevention element, and that is connected in parallel to the first
converter section, switching control means that controls the first
and the second switching elements, and a smoothing capacitor
provided at the output of the first and the second converter
sections. The switching control means switches the current mode of
the current flowing through the first and the second reactors into
any of a continuous mode, a critical mode, and a discontinuous mode
based on a predetermined condition.
Advantageous Effects of Invention
[0010] Since the present invention includes a first converter
section and a second converter section connected with the first
converter section in parallel, an inductance required for a reactor
can be made small, allowing to achieve a small light-weighted
reactor.
[0011] Switching loss can be reduced because a current mode of the
current flowing through the first and the second reactors can be
switched to any of a continuous mode, a critical mode, and a
discontinuous mode based on a predetermined condition.
BRIEF DESCRIPTION OF DRAWINGS
[0012] FIG. 1 is a configuration diagram of a converter circuit
according to Embodiment 1 of the present invention.
[0013] FIG. 2 is a diagram showing an electric signal and a current
waveform of each part at a continuous mode operation of the
converter circuit.
[0014] FIG. 3 is a diagram showing the electric signal and the
current waveform of each part at a discontinuous mode operation of
the converter circuit.
[0015] FIG. 4 is a diagram showing the electric signal and the
current waveform of each part at a critical mode operation of the
converter circuit.
[0016] FIG. 5 is a configuration diagram of the converter circuit
according to Embodiment 2 of the present invention.
[0017] FIG. 6 is a diagram illustrating the current waveform of the
converter circuit.
[0018] FIG. 7 is a diagram illustrating switching operation of a
current mode according to Embodiment 2 of the present
invention.
[0019] FIG. 8 is a configuration diagram of the converter circuit
according to Embodiment 2 of the present invention.
[0020] FIG. 9 is a configuration diagram of the converter circuit
according to Embodiment 3 of the present invention.
[0021] FIG. 10 is a configuration diagram of the converter circuit
according to Embodiment 4 of the present invention.
[0022] FIG. 11 is a configuration diagram of the converter circuit
according to Embodiment 4 of the present invention.
[0023] FIG. 12 is a configuration diagram of a motor drive circuit
according to Embodiment 6 of the present invention.
[0024] FIG. 13 is a configuration diagram of an air-conditioner
according to Embodiment 7 of the present invention.
[0025] FIG. 14 is a configuration diagram of a refrigerator
according to Embodiment 8 of the present invention.
[0026] FIG. 15 is a configuration diagram of an induction heating
cooker according to Embodiment 9 of the present invention.
[0027] FIG. 16 is a diagram showing a configuration of a step-down
converter and a step-up/step-down converter.
REFERENCE SIGNS LIST
[0028] 1 commercial power supply [0029] 2 rectifier [0030] 2a-2d
rectifying diode [0031] 3a-3c step-up converter [0032] 4a-4c
step-up reactor [0033] 5a-5c switching element [0034] 6a-6c reverse
current prevention element [0035] 7 switching control means [0036]
8 smoothing capacitor [0037] 9a, 9b opening and closing means
[0038] 10 load [0039] 11 inverter circuit [0040] 11a-11f switching
element [0041] 12 motor [0042] 13 load circuit [0043] 14 induction
heating coil [0044] 15 resonance capacitor [0045] 20 current
detection means [0046] 30 output power detection means [0047] 40
opening and closing control means [0048] 50 inverter drive means
[0049] 310 outdoor unit [0050] 311 refrigerant compressor [0051]
312 blower [0052] 320 indoor unit [0053] 400 refrigerator [0054]
401 refrigerant compressor [0055] 402 cooling compartment [0056]
403 cooler [0057] 404 blower
DESCRIPTION OF EMBODIMENTS
Embodiment 1
[0058] FIG. 1 is a configuration diagram of a converter circuit
according to Embodiment 1 of the present invention.
[0059] In FIG. 1, a rectifier 2 that rectifies AC voltage of the
commercial power supply 1 is constituted by a bridge connection of
four rectifying diodes 2a-2d. To the output of the rectifier 2, a
step-up converter 3a, which is a first converter section, and a
step-down converter 3b, which is a second converter section, are
connected in parallel.
[0060] The step-up converter 3a is constituted by a step-up reactor
4a, which is a first reactor, a switching element 5a, which is a
first switching element composed of, for example, an IGBT
(Insulated Gate Bipolar Transistor), and a reverse current
prevention element 6a, which is a first reverse current prevention
means composed of such as a fast recovery diode. The step-up
converter 3b is constituted by a step-up reactor 4b, which is a
second reactor, a switching element 5b, which is a second switching
element composed of, for example, the IGBT, and the reverse current
prevention element 6b, which is a second reverse current prevention
element composed of, for example, the fast recovery diode.
Inductance values of the step-up reactors 4a and 4b are mentioned
later.
[0061] Switching of the switching elements 5a and 5b is controlled
by switching control means 7 and the output of the rectifier 2 is
boosted.
[0062] Switching elements 5a and 5b are provided with a diode FWD
(Free Wheeling Diode), which is connected in inverse-parallel,
respectively. The diode prevents the switching element 5 from being
broken caused by a surge generated when the switching element 5
turns off.
[0063] In the present embodiment, descriptions will be given to the
case where the first and second converter sections are step-up
converters 3a and 3b, respectively. However, the present invention
is not limited thereto. An arbitrary switching converter may be
applied such as a step-up converter, a step-down converter, and a
step-up/step-down converter.
[0064] For example, as shown in FIG. 16(a), the step-down converter
may be used for the first and the second converter sections.
Alternatively, the step-up/step-down converter may be used for the
first and the second converter sections.
[0065] The output of the step-up converter 3a and the step-up
converter 3b is smoothed by a smoothing capacitor 8. To the output
of the step-up converters 3a and 3b, a load (not shown) is
connected and the smoothed output of the step-up converters 3a and
3b is applied.
[0066] Next, descriptions will be given to an inductance value of
the step-up reactors 4a and 4b (hereinafter, simply referred to as
a "step-up reactor 4" unless discriminated).
[0067] The inductance value L of the step-up reactor 4 configured
as the above is defined by formula 1 as follows.
L = V in 2 2 P in K f c V o - 2 V in V o Formula 1 ##EQU00001##
[0068] where, fc is a switching frequency, Vin an input voltage, Vo
an output voltage, Pin an input power ripple rate, and K a current
ripple rate.
[0069] As shown by Formula 1, the larger the current ripple rate K
of the current flowing through the step-up reactor 4, the smaller
the inductance value L. Accordingly, since by making the current
flowing through the step-up reactor 4 to be the peak critical mode
or discontinuous mode (to be mentioned later), the current value
becomes larger than the average current value to increase the
current ripple rate K, the inductance value L required for the
step-up reactor 4 can be made small. Hence, the value obtained from
the above Formula 1 is used for the inductance value L of the
step-up reactor 4 when the current flowing through the step-up
reactor 4 is made to be the critical mode or the discontinuous
mode.
[0070] Descriptions will be given to the behavior and operation of
the converter circuit configured above as follows.
[0071] As shown in FIG. 1, the AC voltage of the commercial power
supply 1 is rectified by the rectifier 2. The output of the
rectifier 2 is branched into two current paths by the step-up
converters 3a and 3b connected in parallel. The branched current
flows through the step-up reactors 4a and 4b. Switching of the
switching elements 5a and 5b is controlled by switching control
means 7 and the output of the rectifier 2 is boosted. The switching
control means 7 controls switching of the switching elements 5a and
5b to control a current mode and a phase difference of the current
flowing into the step-up reactors 4a and 4b. The switching
operation will be mentioned later.
[0072] FIG. 2 is a diagram showing an electric signal and a current
waveform of each part at a continuous mode operation of the
converter circuit. FIG. 3 is a diagram showing an electric signal
and a current waveform of each part at a discontinuous mode
operation of the converter circuit. FIG. 4 is a diagram showing an
electric signal and a current waveform of each part at a critical
mode operation of the converter circuit.
[0073] Next, switching operation of the step-up converters 3a and
3b will be explained.
[0074] When the switching element 5a turns on in the step-up
converter 3a, conduction of a reverse current prevention element 6a
is suspended and rectified voltage by the rectifier 2 is applied to
the step-up reactor 4a. On the other hand, when the switching
element 5a turns off, the reverse current prevention element 6a is
made to conduct electricity and a reversed voltage is induced in
the step-up reactor 4a to when the switching element 5a turns
on.
[0075] Thus, the current flowing through the step-up reactor 4a
linearly increases when the switching element 5a turns on and
linearly decreases when the switching element 5a turns off.
[0076] In the step-up converter 3b, the current flowing through the
step-up reactor 4b linearly increases when the switching element 5b
turns on and linearly decreases when the switching element 5b turns
off as well.
[0077] In the switching operation of the switching elements 5a and
5b (hereinafter, simply referred to as "switching element 5" unless
discriminated) as shown in FIG. 2, the operation condition in which
the current flowing through the step-up reactor 4 does not become 0
(zero) even if being reduced, is called a continuous mode. On the
other hand, as shown in FIG. 3, the operation condition, in which
an interval exists where the current flowing through the step-up
reactor 4 decreases to 0 (zero), is called a discontinuous mode.
The operation condition, in which the switching element 5 turns on
at the moment when the current flowing through the step-up reactor
4 decreases to 0 (zero) while the switching element 5 turns off, is
called a critical mode from a meaning that it is a boundary between
the continuous mode and the discontinuous mode.
[0078] As mentioned above, the inductance value L of the step-up
reactor 4 employs a value defined when the current flowing through
the step-up reactor 4 is made to be the critical mode or the
discontinuous mode. As shown in FIGS. 4 and 3, switching of the
switching elements 5a and 5b is controlled by the switching control
means 7 such that the current flowing through the step-up reactors
4a and 4b becomes the critical mode or the discontinuous mode.
[0079] The switching control means 7 controls the current flowing
through the step-up reactors 4a and 4b with a phase shift so that a
predetermined phase difference is created (for example, a phase
difference of 180 degrees constant, respectively) as shown in FIGS.
3 and 4.
[0080] Thus, while the input currents before being branched into
two current paths by the step-up converters 3a and 3b that have
operated as the critical mode or the discontinuous mode in each
step-up reactors 4a and 4b, respectively are added to operate as
the continuous mode.
[0081] As mentioned above in the present embodiment, the step-up
converter 3 is made to have two systems and operated such that the
current flowing each step-up reactor 4 becomes the critical mode
the critical mode or the discontinuous mode. Therefore, two
components are necessary that constitutes each step-up converter 3.
However, since the current flowing through the step-up reactor 4
has a large current ripple against the average current value, the
inductance value L required for the step-up reactor 4 can be made
small, achieving the step-up reactor 4 to be small and
light-weighted.
[0082] Thereby, material cost of the step-up reactor 4 itself can
be reduced, wiring can be reduced by making step-up reactor 4
on-board, and noise-resistance can be improved.
[0083] Compared with a single system step-up converter 3, the small
step-up reactor 4 can be provided by dividing itself into two,
allowing design intending to improve degree-of-freedom of
installing components in the circuit, to improve assembling
efficiency, and to reduce mistakes.
[0084] Further, by making the step-up reactor 4 occupying a greater
part of circuitry capacity small and light-weighted, it becomes
possible to reinforce merits such as to make the product itself
small and light-weighted.
[0085] By making the product itself small, it becomes possible to
make packaging of the relevant product light-weighted and small to
achieve reduction in packaging volume.
[0086] In the step-up converter 3, an FWD is provided in
inverse-parallel to the switching elements 5a and 5b. Because of
this, the switching element 5 can be protected from breakdown
caused by a surge generated in the wiring impedance where one end
of the step-up reactor 4, one end of the switching element 5, and
one end of the reverse current prevention element 6 are connected
when the switching element 5 turns off.
[0087] Since the current flowing through the step-up reactor 4 is
controlled with phase shift, the input current can be operated in
the continuous mode while each step-up reactor 4 is operated in the
critical mode or the discontinuous mode. Harmonics currents of the
input current can be suppressed, resultantly.
[0088] When comparing with the single system step-up converter 3 in
the discontinuous mode or the critical mode, the current flowing
through each element of the step-up converter 3 is almost halved,
therefore, a small capacity element can be selected for the step-up
reactor 4, the switching element 5, and the reverse current
prevention element 6.
[0089] As mentioned above, the input current is an addition of
currents flowing through the step-up reactors 4a and 4b. Thereby,
if the phase difference of currents flowing the step-up reactors 4a
and 4b is controlled by 180 degrees (reverse phase) in the
switching control means 7, the level of the current ripple of the
input current becomes the smallest, allowing to reduce
high-frequency components of the input current. Then, the frequency
of the current ripple of the input current is twice the switching
frequency.
[0090] A case is conceivable where the current ripple of the input
current causes noises or vibrations at the doubled frequency of the
switching frequency when controlling the phase difference by 180
degrees (reverse phase). In this case, by controlling the phase
difference of the current flowing through the step-up reactors 4a
and 4b to randomly vary within a predetermined range such as a
random value around 180 degrees instead of 180 degrees constant,
the component of the doubled switching frequency can be reduced and
the noise can be suppressed.
[0091] An example will be explained of method for generating a
random value of the phase difference. Inside the switching control
means 7, in the phase difference difference calculation section
(not shown) that obtains random numbers in the range of, for
example, -1 to 1 from a random number generation section (not
shown), a difference of the phase difference is calculated by
multiplying the maximum value 180 degrees of the difference of the
phase difference by the random number. Here, by adding the
difference to the phase difference 180 degrees, a random number
centering around 180 degrees is obtained as phase difference of the
current flowing through the step-up reactors 4a and 4b.
[0092] Thereby, it becomes possible to suppress the current ripple,
noises or vibrations dependent on the switching frequency without
making each switching frequency of the switching elements 5a and 5b
different.
[0093] When employing random numbers for the phase difference, some
case is conceivable where the tone of noises is felt as if the
level of the sound were totally increased from the sound having a
rising peak. Then, by narrowing the range of the random number
obtained from a random number generation section, such as, -0.5 to
0.5 or -0.3 to 0.3, noise level and tone can be adjusted.
Embodiment 2
[0094] In Embodiment 1, operation is performed so that the current
mode flowing through the step-up reactor 4 becomes the critical
mode or the discontinuous mode. In Embodiment 2, by switching the
current mode during operation, operation taking advantage of each
current mode is possible.
[0095] Here, descriptions will be given to characteristics of each
current mode.
[0096] When controlled by the continuous mode, the current ripple
is smaller than the critical mode and the discontinuous mode,
allowing to suppress the generation of harmonics components of the
input current. On the other hand, the switching frequency becomes
higher than the critical mode and the discontinuous mode, causing a
large switching loss in the switching element 5 and the reverse
current prevention element 6.
[0097] When operated in the critical mode, the current ripple rate
becomes smaller than the discontinuous mode, enabling generation of
the high-frequency components of the input current to be
suppressed. On the other hand, the switching frequency becomes
higher than the discontinuous mode, causing a large switching loss
in the switching element 5 and the reverse current prevention
element 6.
[0098] When operated in the discontinuous mode, since the current
ripple in the input current is larger compared with the continuous
mode and the critical mode, suppressing effect of the harmonics
components of the input current is small. On the other hand, the
switching frequency becomes lower than the critical mode and the
discontinuous mode, causing a small switching loss in the switching
element 5 and the reverse current prevention element 6.
[0099] Thus, the switching control means 7 in Embodiment 2 switches
the mode of the current flowing through the step-up reactors 4a and
4b into any of the continuous mode, the critical mode, and the
discontinuous mode based on a predetermined condition.
[0100] The predetermined condition to switch the current mode and
concrete examples will be explained.
[0101] Firstly, as the predetermined condition to switch the
current mode, operation based on the input current will be
explained.
[0102] FIG. 5 is a configuration diagram of the converter circuit
according to Embodiment 2 of the present invention.
[0103] In FIG. 5, the converter circuit further includes current
detection means 20 that detects the input current input to the
step-up converters 3a and 3b in addition to the configuration of
the above Embodiment 1.
[0104] The other configuration is the same as that of Embodiment 1,
and the same signs will be given to the same configuration.
[0105] The inductance value L of the step-up reactor 4 employs the
value defined by the above Formula 1 when the current flowing
through the step-up reactor 4 is in the critical mode. The critical
mode is switched to the discontinuous mode to be mentioned later.
Therefore, it is necessary to define the value L in the critical
mode in which the current ripple is smaller.
[0106] Based on the above configuration, the switching control
means 7 switches the mode of the current flowing through the
step-up reactor 4 based on the magnitude (level) of the input
current detected by current detection means 20.
[0107] The switching control means 7 is set with 30% of the peak
value of the input current being a threshold, for example. When the
magnitude (level) of the detected input current is equal to or
larger than the threshold, switching of the switching element 5 is
controlled so that the current flowing through the step-up reactor
4 becomes the critical mode. On the other hand, when the magnitude
(level) of the detected input current is less than the threshold,
switching of the switching element 5 is controlled so that the
current flowing through the step-up reactor 4 becomes the
discontinuous mode.
[0108] FIG. 6 is a diagram illustrating the current waveform of the
converter circuit. FIG. 7 is a diagram illustrating switching
operation of the current mode according to Embodiment 2 of the
present invention.
[0109] In FIGS. 6 and 7, the current waveform and switching
waveform of the step-up reactor 4a shown in FIG. 4 are expressed
with the time axis being magnified. Waveforms shown in FIGS. 6 and
7 are typically shown for expressing the switching operation, not
being the actually measured waveforms. The switching frequency of
the switching element 5 is substantially shorter than that of the
commercial power supply 1 (input voltage waveform).
[0110] As shown in FIG. 6, the current in the critical mode varies
in proportion to the input voltage input to the step-up converter
3a. The switching frequency becomes low in the vicinity of the peak
of the current and high in the vicinity of the zero cross
point.
[0111] FIG. 7 shows the current waveform and switching waveform
when the current mode is switched based on the above operation. As
shown in FIG. 7, in the vicinity of the peak of the current, the
operation becomes the critical mode, and in the vicinity of the
zero cross point the discontinuous mode.
[0112] From the above operations, in the vicinity of the peak
region where the input current is large, the switching frequency
becomes high compared with the discontinuous mode by making the
current mode to be the critical mode, however, contribution of the
input current to the suppression of harmonics components is large
in the critical current mode. Accordingly, the effect of
suppressing the harmonics components can be maintained.
[0113] In the vicinity of the zero cross where the input current is
small, when compared with the critical mode, the effect of
suppressing the harmonics components becomes smaller by making the
current to be the discontinuous mode, however, the switching loss
can be decreased by reducing the switching frequency.
[0114] In the above, explanations are given to the case where the
threshold is 30% of the input current, however, the present
invention is not limited thereto. For example, by setting the
threshold larger such as 50% of the input current, the range of the
discontinuous mode can be expanded, allowing to reduce much more
switching loss.
[0115] Further, by setting the threshold smaller such as 10% of the
input current, the range of the critical mode can be expanded,
allowing to reduce much more harmonics components of the input
current.
[0116] Next, operation based on the switching frequency will be
explained as the predetermined condition to switch the current
mode.
[0117] As shown in the above FIG. 6, in the operation of the
critical mode, the switching frequency cannot be kept constant, but
being low in the vicinity of the peak of the input current and
being high in the vicinity of the zero cross. Thus, switching
control means 7 switches the mode of the current flowing through
the step-up reactors 4a and 4b based on the switching frequency of
the switching element 5.
[0118] With the switching control means 7, a predetermined
frequency is set as the threshold in advance. In the switching
control of the switching element 5, if the switching frequency is
less than the threshold, the mode of the current flowing through
the step-up reactor 4 is switched into the critical mode. On the
other hand, if the switching frequency is equal to or larger than
the threshold, the mode of the current flowing through the step-up
reactor 4 is switched into the discontinuous mode.
[0119] From the above operations, in the vicinity of the peak
region where the switching frequency is low, the switching
frequency becomes high compared with the discontinuous mode by
making the current mode to be the critical mode, however,
contribution of the input current to the suppression of harmonics
components is large in the critical mode. Accordingly, the effect
of suppressing the harmonics components can be maintained.
[0120] In the vicinity of the zero cross where the switching
frequency is high, when compared with the critical mode, the effect
of suppressing the harmonics components becomes smaller, however,
the switching loss can be decreased by reducing the switching
frequency.
[0121] If the threshold of the switching frequency set at the
switching control means 7 is made to conform to the specification
of the switching element 5, the switching element 5 can be
prevented from breakdown and used in more suitable environment.
[0122] Next, operation based on the output voltage will be
explained as the predetermined condition to switch the current
mode.
[0123] In the operation of the critical mode, the higher the load,
the lower the switching frequency for the output voltage. Thereby,
the switching control means 7 switches the current mode flowing
through the step-up reactor 4 based on the output voltage.
[0124] FIG. 8 is a configuration diagram of a converter according
to Embodiment 2 of the present invention.
[0125] In FIG. 8, the converter circuit is further provided with
output power detection means 30 that detects the output power of
the step-up converters 3a and 3b in addition to the configuration
of Embodiment 1. The other configurations are the same as that of
Embodiment 1. The same signs will be given to the same
configurations.
[0126] Like FIG. 5, the inductance L of the step-up reactor 4
employs the value defined by the above formula 1 when the current
flowing therethrough is made to be the critical mode.
[0127] With the configuration above, the switching control means 7
switches the current mode flowing through the step-up reactor 4
based on the output voltage detected by the output power detection
means 30.
[0128] A predetermined output power is set at the switching control
means 7 as the threshold. When the detected output power is equal
to or larger than the threshold, the switching element 5 is
controlled such that the current mode flowing through the step-up
reactor 4 becomes the critical mode. When the detected output power
is less than the threshold, the switching element 5 is controlled
such that the current mode flowing through the step-up reactor 4
becomes the discontinuous mode.
[0129] From the above operations, in the case of high load, the
switching frequency is high compared with the discontinuous mode by
making the current mode to be the critical mode, however,
contribution of the input current to the suppression of harmonics
components is large in the critical current mode. Accordingly, the
effect of suppressing the high-frequency components can be
maintained.
[0130] In the case of low load, when compared with the critical
mode, the effect of suppressing the harmonics components becomes
smaller by making the current mode to be the disconnection mode,
however, the switching loss can be decreased by reducing the
switching frequency.
[0131] When providing a threshold with the above-mentioned input
current and the switching frequency, and the current mode is
switched based on the output voltage like the above, since
switching of the current mode is less frequent than the case where
the current mode is frequently switched within a time period of the
power source, a simpler program can perform the control.
[0132] Next, descriptions will be given to operations based on the
circuit efficiency as predetermined conditions for switching the
current mode.
[0133] In the low-load area, the circuit efficiency improves with
the increase in the output voltage. However, in the high-load area,
the circuit efficiency sometimes decreases. Thereby, the switching
control means 7 switches the current mode flowing through the
step-up reactor 4 based on the circuit efficiency.
[0134] The converter circuit includes the current detection means
20 shown in the above-mentioned FIG. 5 and the output power
detection means 30 shown in the above-mentioned FIG. 8. The other
configurations are the same as that of Embodiment 1.
[0135] Based on the above-mentioned configuration, with the
switching control means 7, the predetermined circuit efficiency is
set as the threshold.
[0136] The switching control means 7 obtains the circuit efficiency
based on the detected input current and the output power. Then, if
the obtained circuit efficiency is less than the threshold, when
the mode of the current flowing through the step-up reactor 4 is
the critical mode, it is switched into the discontinuous mode. When
the continuous mode, it is switched into the critical mode or the
discontinuous mode.
[0137] Through the above-mentioned operations, when the circuit
efficiency is lowered, the switching frequency is reduced to
decrease the switching loss and the circuit efficiency can be
improved.
[0138] Next, as the predetermined condition for switching the
current mode, operations will be explained based on the output
voltage, the output voltage command, or the changed values of the
output voltage command.
[0139] When the output voltage command is changed against the
step-up converter 3, the ripple of the input current is changed.
Therefore, the switching control means 7 switches the mode of the
current flowing through the step-up reactor 4 based on the output
voltage, the output voltage command, of the changed values of the
output voltage command.
[0140] Into the switching control means 7, information on the
output voltage command that specifies the output voltage of the
step-up converter 3 is input. Then, the switching control means 7
controls the switching element 5 according to the input output
voltage command to specify the output voltage of the step-up
converter 3.
[0141] In the switching control means 7, a predetermined value or a
range is preset as a threshold, with which the current ripple
becomes large against the output voltage, the output voltage
command, or the changed values of the output voltage. The other
configurations are the same as that of Embodiment 1.
[0142] For the inductance value L of the step-up reactor 4, a value
defined by the above formula 1 is employed when the current flowing
through the step-up reactor 4 is in the continuous mode. The object
is to make it operate in the continuous mode in which the current
ripple is smaller.
[0143] Based on the above-mentioned configuration, the switching
control means 7 switches the mode of the current flowing through
the step-up reactor 4 into the continuous mode when the output
voltage, the output voltage command, or the changed value of the
output voltage command is the predetermined value or in the region
where the current ripple becomes large.
[0144] Through the above-mentioned operations, when the output
voltage command is changed and the current ripple becomes large,
the current can be switched into the continuous mode where the
current ripple is smaller to be able to suppress the harmonics
component.
Embodiment 3
[0145] In the above-mentioned Embodiments 1 or 2, descriptions are
given to the case where the step-up converter has two systems. In
Embodiment 3, the converter of three or more systems will be
employed.
[0146] FIG. 9 is a configuration diagram of the converter circuit
according to Embodiment 3 of the present invention.
[0147] As shown in FIG. 9, the converter circuit in Embodiment 3
includes the step-up converter 3c connected with the step-up
converters 3a and 3b in parallel in addition to the configuration
of Embodiment 1.
[0148] The step-up converter 3c is constituted by the step-up
reactor 4c, which is the reactor of the present invention, and such
as IGBT, a switching element 5c, which is a switching element of
the present invention, such as a fast recovery diode, and a reverse
current prevention element 6c, which is a reverse current
prevention element of the present invention. The other
configurations are the same as that of Embodiment 1. The same signs
will be given to the same configurations.
[0149] Such a configuration allows the input current, which is an
addition of currents flowing through each step-up reactor 4, to
have much smaller current ripple to further improve the harmonics
current suppression effect.
[0150] The current flowing through the step-up reactor 4, switching
element 5, reverse current prevention element 6 of each step-up
converter 3 becomes further smaller and elements having further
smaller capacity can be selected.
[0151] FIG. 9 shows a case where the step-up converter 3 has three
systems, however, the present invention is not limited thereto. The
step-up converter 3 may be connected for an arbitrary number (N)
that is three systems or more in parallel.
[0152] As explained in the above Embodiment 1, the input current is
the addition of currents flowing through each step-up reactor 4.
For example, when N systems of the step-up converter are connected
in parallel, the current ripple of the input current becomes
minimum at 360/N degrees. Thereby, the current ripple frequency of
the input current becomes N times of the switching frequency.
[0153] Then, the current ripple of the input current may cause
noises at the frequencies which is N times of the switching
frequency. Thereby, by controlling the phase difference of the
current flowing through each step-up reactor to be made to change
only for several times in the vicinity of 360/N, components of N
times of the switching frequency can be reduced and noises can be
suppressed.
[0154] The change of the phase difference can be changed at random
by a phase difference difference calculation section and the like
within a predetermined area like the above Embodiment 1.
[0155] The larger the number of the system of the step-up converter
3, the smaller the current ripple of the input current.
Accordingly, the harmonics components suppression effect of the
input current can be improved. A noise filter can be made
small.
[0156] The current flowing through the step-up reactor 4, switching
element 5, reverse current prevention element 6 can be made smaller
and elements having much smaller capacity can be selected.
[0157] The mode of the current flowing through the step-up reactor
4 can be switched into any of the continuous mode, the critical
mode, or the discontinuous mode based on trade-off between the
number (N) of the system of the step-up converter 3 and the current
mode. For example, a variety of configurations are possible such as
a configuration operable under the continuous mode when focusing on
the suppression effect of the harmonics components, the
configuration operable under the critical mode when focusing on
small and light-weighted type, a configuration operable under the
discontinuous mode when focusing on low loss.
Embodiment 4
[0158] FIG. 10 is a configuration diagram of the converter circuit
according to Embodiment 4 of the present invention. in FIG. 10, the
rectifier 2 that rectifies the AC voltage of the commercial power
supply 1 is configured to bridge-connect four rectifying diodes 2a
to 2d. To the output of the rectifier 2, the step-up converter 3a
and the step-up converter 3b are connected in parallel.
[0159] The step-up converter 3a is composed of the step-up reactor
4a, switching element 5a such as an IGBT, the reverse current
prevention element 6a such as a fast recovery diode.
[0160] The step-up converter 3b is also composed of the step-up
reactor 4b, the switching element 5b such as an IGBT, the reverse
current prevention element 6bv such as a fast recovery diode.
[0161] The switching elements 5a and 5b are controlled by the
switching control means 7 to boost the output of the rectifier 2.
The inductance L of the step-up reactors 4a and 4b employs the
values defined by the above formula 1 when the current flowing
therethrough is made to be the critical mode or discontinuous mode
like the above-mentioned Embodiment 1.
[0162] Switching elements 5a and switching elements 5b are provided
with a FWD connected in inverse-parallel, respectively. The diode
prevents the switching element 5 from being broken caused by a
surge generated when the switching element 5 turns off.
[0163] In the present embodiment, the step-up converter 3 is not
limited, but any switching converter can be applied such as a
step-up converter, a step-down converter, a step-up/step-down
converter.
[0164] The output of the step-up converter 3a and the step-up
converter 3b is smoothed by the smoothing capacitor 8. To the
output of the step-up converters 3a and 3b, a load (not shown) is
connected and the output of the smoothed step-up converters 3a and
3b is applied.
[0165] To the output side of the step-up converter 3a, opening and
closing means 9a is provided composed of a switching element that
opens and closes the output of the step-up converter 3a. To the
output side of the step-up converter 3b, opening and closing means
9b is provided composed of a switching element that opens and
closes the output of the step-up converter 3b. The opening and
closing control means 40 is provided that controls the opening and
closing of the opening and closing means 9a and 9b.
[0166] Descriptions will be given to the behavior and operation of
the converter circuit configured above as follows.
[0167] If both opening and closing means 9a and 9b are on state,
the circuit configuration is the same as that of the above
Embodiment 1. The AC voltage of the commercial power supply 1 is
rectified by the rectifier 2 like the above Embodiment 1. The
output of the rectifier 2 is branched into two current paths by the
step-up converters 3a and 3b connected in parallel. The branched
current flows into the step-up reactors 4a and 4b, switching of the
switching elements 5a and 5b being controlled by the switching
control means 7, and the output of the rectifier 2 being boosted.
The switching control means 7 controls switching of the switching
elements 5a and 5b to control the current mode and phase difference
of the current flowing through the step-up reactors 4a and 4b. The
switching operation is the same as that of the above Embodiment
1.
[0168] When both opening and closing means 9a and 9b are on-state,
the same effect as the above Embodiment 1 can be obtained.
[0169] Next, descriptions will be given to switching operation of
use conditions of the step-up converters 3a and 3b by the opening
and closing means 9a and 9b.
[0170] As shown in FIG. 10, the converter circuit of the present
embodiment is provided with the opening and closing means 9a and 9b
controlled by the opening and closing control means 40.
[0171] The opening and closing control means 40 opens and closes at
least either of the opening and closing means 9a or 9b based on a
predetermined condition to operate both or either of the step-up
converters 3a or 3b. That is, when the opening and closing means 9a
is made to on and the opening and closing means 9b is made to off,
the step-up converter 3a can be made to be a used state and the
step-up converter 3b can be made to be a stop state. Alternatively,
when the opening and closing means 9a is made to off and the
opening and closing means 9b is made to on, the step-up converter
3a can be made to be the stop state and the step-up converter 3b
can be made to be the used state.
[0172] Switching of use conditions of the step-up converters 3a and
3b by the opening and closing means 9a and 9b (hereinafter, simply
referred to as "use conditions") is performed by providing a
threshold value with the input current level, the switching
frequency, the circuit efficiency, the output power, and so on.
Descriptions will be given to the predetermined condition to switch
the use conditions and concrete examples thereof as follows.
[0173] Firstly, as the predetermined condition for switching the
use conditions, the operation based on the input current will be
explained.
[0174] In addition to the configuration of the above-mentioned FIG.
10, current detection means 20 is provided that detects the input
current input to the step-up converters 3a and 3b like the
above-mentioned Embodiment 2 (FIG. 5).
[0175] The opening and closing control means 40 switches on-off of
the opening and closing means 9a and 9b based on the magnitude
(level) of the input current detected by the current detection
means 20.
[0176] The opening and closing control means 40 is set with 30% of
the peak value of the input current being the threshold, for
example. When the magnitude (level) of the detected input current
is equal to or larger than the threshold, both opening and closing
means 9a and 9b are made to be on and both step-up converters 3a
and 3b are made to be in the used state.
[0177] On the other hand, when the magnitude (level) of the
detected input current is less than the threshold, either the
opening and closing means 9a or 9b is made to be on and the other
off, and either step-up converters 3a or 3b is made to be in the
used state.
[0178] Through the above-mentioned operations, in the vicinity of
the peak having a large input current, since the input current is
divided into the route of the step-up converter 3a and the route of
3b by making both of them to be a used condition, the current
flowing through the components of each step-up converter 3 can be
suppressed.
[0179] In the vicinity of the zero cross having a small input
current, by making either the step-up converter 3a or 3b to be the
used condition, no operation loss occurs in the step-up converter 3
under the stop state, allowing to reduce circuit loss.
[0180] Next, descriptions will given to operations based on the
switching frequency as the predetermined condition for switching
the use conditions.
[0181] As shown in Embodiment 2 (FIG. 6), the switching frequency
cannot be made to be constant during the operation in the critical
mode. While the switching frequency is low in the vicinity of the
peak of the input current, it is high in the vicinity of the zero
cross. Thereby, the opening and closing control means 40 switches
on-off of the opening and closing means 9a and 9b based on the
switching frequency of the switching element 5.
[0182] In the opening and closing control means 40, a predetermined
frequency is set as a threshold. Into the opening and closing
control means 40, information on the switching frequency is input
from the switching control means 7. If the switching frequency is
less than the threshold, both opening and closing means 9a and 9b
becomes on and both step-up converters are made to be the used
state.
[0183] On the other hand, if the switching frequency is equal to or
more than the threshold, either opening and closing means 9a or 9b
becomes on and the other off, and either step-up converter 3a or 3b
becomes the used state.
[0184] Through the above-mentioned operations, in the region having
a low switching frequency, since the input current is divided into
the route of the step-up converter 3a and the route of 3b by making
both of them to be a used state, the current flowing through the
components of each step-up converter 3 can be suppressed.
[0185] In the region where the switching frequency is high, by
making either the step-up converter 3a or 3b to be a used state, no
operation loss occurs in the step-up converter 3 under the stop
state, allowing to reduce circuit loss.
[0186] If the threshold of the switching frequency set at the
opening and closing control means 40 is set according to the
specification of the switching element 5, for example, the
switching element 5 can be prevented from breakdown and used under
more favorable environment.
[0187] Next, descriptions will be given to operations based on the
output voltage as the predetermined condition for switching the use
conditions.
[0188] During the operation in the critical mode, regarding the
output power, the higher the load, the lower the switching
frequency. Therefore, the opening and closing control means 40
switches on-off of the opening and closing means 9a and 9b based on
the output power.
[0189] In addition to the above-mentioned configuration of FIG. 10,
like Embodiment 2 (FIG. 8) the above, the output power detection
means 30 is provided that detects the output power of the step-up
converters 3a and 3b.
[0190] The opening and closing control means 40 switches on-off of
the opening and closing means 9a and 9b based on the output power
detected by the output power detection means 30.
[0191] With the opening and closing control means 40, a
predetermined output power is set as a threshold in advance. When
the detected output power is equal to or larger than the threshold,
both opening and closing means 9a and 9b are turned on and both
step-up converters 3a and 3b are made to be the used state.
[0192] On the other hand, when the detected output power is less
than the threshold, either opening and closing means 9a or 9b is
turned on and the other off, and either step-up converter 3a or 3b
is made to be the used state.
[0193] Through the above-mentioned operations, in the case of the
high load, since the input current is divided into the route of the
step-up converter 3a and the route of 3b by making both of them to
be the used state, the current flowing through the components of
each step-up converter 3 can be suppressed.
[0194] In the case of the low load, by making either the step-up
converter 3a or 3b to be the used state, no operation loss occurs
in the step-up converter 3 under the stop state, allowing to reduce
circuit loss.
[0195] While the current mode is frequently switched within a power
source cycle in the case where a threshold is provided for the
above-mentioned input current and the switching frequency, the
frequency of on-off switching is low for the opening and closing
means 9a and 9b when the current mode is switched based on the
output power like the above, allowing to perform control with a
simpler program.
[0196] Next, descriptions will be given to operations based on the
circuit efficiency as the predetermined condition for switching the
use condition.
[0197] In the low load area, the circuit efficiency increases as
the output power increases, however, in the high load area, the
circuit efficiency sometimes decreases. Therefore, the opening and
closing control means 40 switches on-off of the opening and closing
means 9a and 9b based on the circuit efficiency.
[0198] In addition to the above-mentioned configuration of FIG. 10,
the current detection means 20 and the output power detection means
30 are provided. With the opening and closing control means 40, a
predetermined circuit efficiency value is set as a threshold in
advance.
[0199] The opening and closing control means 40 obtains the circuit
efficiency based on the detected input current and the output
power. When the obtained circuit efficiency value is less than the
threshold, either opening and closing means 9a or 9b is turned on,
the other off, and either step-up converter 3a or 3b is made to be
the used state. On the other hand, when the circuit efficiency
value is equal to or larger than the threshold, both opening and
closing means 9a and 9b are turned on and both step-up converters
3a and 3b are made to be the used state.
[0200] Through the above-mentioned operations, by making either
step-up converter 3a or 3b to be in the used state when the circuit
efficiency is decreased, no operation loss occurs in the step-up
converter 3 under the stop state, allowing to improve the circuit
efficiency.
[0201] Next, as the predetermined condition for switching the use
condition, operations will be explained based on the output
voltage, the output voltage command, or the changed values of the
output voltage command.
[0202] When changing the output voltage command against the step-up
converter 3, the current ripple of the input current changes as
well. Thereby, the opening and closing control means 40 switches
on-off of the opening and closing means 9a and 9b based on the
output voltage, the output voltage command, or the changed value of
the output voltage command.
[0203] To the switching control means 7, the output voltage command
that sets the output voltage of the step-up converter 3 is input.
The switching control means 7 controls the switching element 5
according to the output voltage command to set the output voltage
of the step-up converter 3.
[0204] To the opening and closing control means 40, information on
the output voltage command is input. To the opening and closing
control means 40, the predetermined value or range is set in
advance as the threshold, for which the current ripple becomes
large against the output voltage, the output voltage command, or
the changed values of the output voltage command.
[0205] The opening and closing control means 40 turns both opening
and closing means 9a and 9b on and makes both step-up converters 3a
and 3b to be used state when the output voltage, the output voltage
command, or the changed value of the output voltage command is the
predetermined value or in the area.
[0206] Through the above-mentioned operations, by making both
step-up converters 3a and 3b to be the used state, the current
ripple of the input current can be made small and harmonic
components can be suppressed when the output voltage command
changes and the current ripple increases.
[0207] Next, descriptions will be given to operations of switching
by an arbitrary period as the predetermined condition for switching
the use condition.
[0208] If the use condition is maintained for both or either
step-up converter 3a or 3b, the temperature increases of each
element constituting the step-up converter 3. Thereby, the opening
and closing control means 40 switches on-off of the opening and
closing means 9a and 9b at an arbitrary period to switch the used
state and the stop state of the step-up converters 3a and 3b at an
arbitrary period.
[0209] Through such operations, temperature rise in the step-up
reactor 4, switching element 5, and reverse current prevention
element 6 constituting the step-up converter 3 can be suppressed
and the converter circuit can be more efficiently operated.
[0210] By suppressing temperature rise in each element, breakdown
of elements due to excess operation temperature can be prevented
and long term usage becomes possible.
[0211] In Embodiment 4, by adjusting the phase difference of the
current flowing through the step-up reactors 4a and 4b to be 180
degrees or a random value centering around 181 degrees, harmonics
of the input current and noise vibrations caused by the current
ripple can be suppressed.
[0212] In Embodiment 4, the case where the step-up converter 3 has
two systems is explained. However, the present invention is not
limited thereto, but a plurality of systems may be connected in
parallel for the step-up converter 3 as shown in FIG. 11, for
example. Through such a configuration, the same effect as
Embodiment 3 can be obtained.
Embodiment 5
[0213] In the above Embodiment 2, the current mode flowing through
the step-up reactors 4 is switched based on the predetermined
condition. In Embodiment 4, the use condition of the step-up
converters 3a and 3b is switched based on the predetermined
condition. In Embodiment 5, the switching of the use condition of
the step-up converters 3a and 3b and the switching of the current
mode flowing through the step-up reactors 4 are performed
simultaneously based on the predetermined condition.
[0214] Descriptions will be given to the predetermined condition to
switch the used condition and the current mode and concrete
examples thereof as follows. The configuration of the converter
circuit in Embodiment 5 is the same as that in Embodiment 4.
[0215] Firstly, as the predetermined condition for switching the
use condition and the current mode, operations will be explained
based on the input current.
[0216] Like the above Embodiment 4, when the magnitude (level) of
the input current detected by the current detection means 20 is
equal to or larger than the threshold, the opening and closing
control means 40 turns both opening and closing means 9a and 9b on
and makes both step-up converters 3a and 3b to be used state. The
switching control means 7 controls the switching of the switching
element 5 so that the current mode flowing through the step-up
reactor 4 is made to be the critical mode or the discontinuous
mode.
[0217] When the magnitude (level) of the detected input current is
less than the threshold, the opening and closing control means 40
turns either opening and closing means 9a or 9b on and the other
off to make either step-up converter 3a or 3b to be used state. The
switching control means 7 controls the switching of the switching
element 5 so that the current mode flowing through the step-up
reactor 4 is made to be the continuous mode.
[0218] Through such operations, in the area near the peak where the
input current is large, by making both step-up converters 3a and 3b
to be used state and making the current mode to be the critical
mode or the discontinuous mode, not only the current flowing
through components of each step-up converter 3 can be suppressed,
but also the current ripple flowing through the step-up reactor 4
can be made large, and the switching loss can be reduced because of
the decrease in the switching frequency.
[0219] In the area near the zero cross where the input current is
small, by making either the step-up converter 3a or 3b is made to
be the used state and the current to be the continuous mode, no
operation loss occurs in the step-up converter 3 under the stop
state, allowing the circuit loss to be reduced, and at the same
time, the ripple of the input current is made small, allowing the
harmonics component to be suppressed.
[0220] Next, descriptions will be given to operations based on the
switching frequency as the predetermined condition for switching
the use condition and the current mode.
[0221] Like the above Embodiment 4, when the switching frequency is
less than the threshold, the opening and closing control means 40
turns both opening and closing means 9a and 9b on and makes both
step-up converters 3a and 3b to be used state. The switching
control means 7 controls the switching of the switching element 5
so that the current mode flowing through the step-up reactor 4 to
be the critical mode or the discontinuous mode.
[0222] When the switching frequency is equal to or larger than the
threshold, the opening and closing control means 40 turns either
opening and closing means 9a or 9b on and the other off and makes
either step-up converter 3a or 3b to be used state. The switching
control means 7 controls the switching of the switching element 5
so that the current flowing through the step-up reactor 4 to be the
continuous mode.
[0223] Through such operations, in the area where the switching
frequency is low, by making both step-up converters 3a and 3b to be
used state and making the current mode to be the critical mode or
the discontinuous mode, the current flowing through components of
each step-up converter 3 can be suppressed, and at the same time,
the current ripple flowing through the step-up reactor 4 can be
made large, allowing the switching loss to be reduced because of
the decrease in the switching frequency.
[0224] In the area where switching frequency is high, by making
either step-up converter 3a or 3b to be the used state, and making
the current to be the continuous mode, no operation loss occurs in
the step-up converter 3 under the stop state, the circuit loss
being reduced, the ripple of the input current being made small,
allowing the harmonics components to be suppressed.
[0225] Next, descriptions will be given to operations based on the
output voltage as the predetermined condition for switching the use
condition and the current mode.
[0226] Like the above Embodiment 4, when the magnitude of the
output power detected by the output power detection means 30 is
equal to or larger than the threshold, the opening and closing
control means 40 turns both opening and closing means 9a and 9b on
and makes both step-up converters 3a and 3b to be used state. The
switching control means 7 controls the switching of the switching
element 5 so that the current mode flowing through the step-up
reactor 4 to be the critical mode or the discontinuous mode.
[0227] When the magnitude of the detected output power is less than
the threshold, the opening and closing control means 40 turns
either opening and closing means 9a or 9b on and the other off and
makes either step-up converter 3a or 3b to be used state. The
switching control means 7 controls the switching of the switching
element 5 so that the current mode flowing through the step-up
reactor 4 to be the critical mode or the discontinuous mode.
[0228] Through such operations, in the case of high load, by making
both step-up converters 3a and 3b to be used state, the current
flowing through components of each step-up converter 3 can be
suppressed, and by making the current to be the critical mode or
the discontinuous mode, the switching loss can be reduced because
of the decrease in the switching frequency.
[0229] In the case of low load, by making either step-up converter
3a or 3b to be the used state, and making the current to be the
continuous mode, no operation loss occurs in the step-up converter
3 under the stop state, loss of the circuit being reduced, the
ripple of the input current being made small, allowing the
harmonics components to be suppressed.
[0230] Next, descriptions will be given to operations based on the
circuit efficiency as the predetermined condition for switching the
use condition and the current mode.
[0231] Like the above Embodiment 4, when the circuit efficiency is
less than the threshold, the opening and closing control means 40
turns either opening and closing means 9a or 9b on and the other
off, and makes either step-up converter 3a or 3b to be used state.
The switching control means 7 switches the current flowing through
the step-up reactor 4 to the discontinuous mode when it is in the
critical mode and vice versa.
[0232] Through such operations, in the case where the circuit
efficiency decreases, by making either step-up converter 3a or 3b
to be used state, no operation loss occurs in the step-up converter
3 under the stop state, and the circuit efficiency can be improved.
When the circuit efficiency decreases, the circuit efficiency can
be improved by reducing the switching frequency to decrease the
switching loss.
[0233] Next, descriptions will be given to operations based on the
output voltage, the output voltage command, or the changed values
of the output voltage command as the predetermined condition for
switching the use condition and the current mode.
[0234] Like the above Embodiment 4, to the switching control means
7, the output voltage command is input that sets the output voltage
of the step-up converter 3. Based on the output voltage command,
the switching control means 7 controls the switching element 5 to
set the output voltage of the step-up converter 3.
[0235] When the output voltage, the output voltage command, or the
changed values of the output voltage command are the predetermined
value or range where the current ripple becomes large, the opening
and closing control means 40 makes both opening and closing means
9a and 9b to be on and makes both step-up converter 3a and 3b in
the used state. The switching control means 7 controls the
switching of the switching element 5 so that the current flowing
through the step-up reactor 4 becomes the continuous mode.
[0236] Through such operations, when the current ripple increases
because of the change in the output voltage command, the ripple of
the input current can be made to be small and harmonics components
can be suppressed by making both step-up converters 3a and 3b to be
the used state and making the current mode to be the continuous
mode.
[0237] In the above descriptions, according to the predetermined
conditions such as the level of the input current, switching
frequency, circuit efficiency, or output power, the use condition
and the current mode are switched. However, the current mode may be
switched according to the opening closing conditions of the opening
and closing means 9a and 9b.
[0238] That is, based on the opening closing conditions of the
opening and closing means 9a and 9b, the switching control means 7
may be adapted to switch the current flowing through the step-up
reactors 4a and 4b into any of the continuous mode, the critical
mode, and the discontinuous mode.
[0239] For example, when both opening and closing means 9a and 9b
are on state and both step-up converters 3a and 3b are in the used
state, the current flowing through the step-up reactor 4a and 4b is
made to be the critical mode or the discontinuous mode. On the
other hand, when either opening and closing means 9a or 9b is on
state and the other off state, and either step-up converter 3a or
3b is in the used state, the current flowing through the step-up
reactor 4 under the used state is made to be the continuous
mode.
[0240] Through such operations, when both step-up converters 3a and
3b are in the used state, by making the current to be the critical
mode or the discontinuous mode, the switching loss can be reduced.
At the same time, since the input current becomes an addition of
two current paths by the step-up converters 3a and 3b and operates
under the continuous mode, the ripple of the input current can be
made small to suppress the harmonics components.
[0241] By making either step-up converter 3a or 3b in the used
state and making the current to be the continuous mode, no
operation loss occurs in the step-up converter 3 under the stop
state, and the loss in the circuit can be reduced. Since the
step-up converter 3 under the used state operates in the continuous
mode, the ripple of the input current can be made small and
harmonics components can be suppressed.
[0242] In Embodiment 5, like the above Embodiment 1, by adjusting
the phase difference of the current flowing through the step-up
reactors 4a and 4b to be 180 degrees or a random value centering
therearound, harmonics components of the input current and noises
or vibrations caused by the current ripple can be suppressed.
[0243] In Embodiment 5, descriptions are given to the case where
the step-up converter 3 includes two systems. However, the present
invention is not limited thereto, and a plurality system of the
step-up converter 3 may be connected in parallel like Embodiment 3.
Through such a configuration, the same effect as the above
Embodiment 3 can be obtained.
Embodiment 6
[0244] In Embodiment 6, an example of configuration is shown where
a motor drive control apparatus is made to be an object load
regarding the converter circuit of the above Embodiments 1 to
5.
[0245] FIG. 12 is a configuration diagram of the motor drive
control apparatus according to Embodiment 6 of the present
invention.
[0246] In FIG. 12, the rectifier 2 that rectifies the AC voltage of
the commercial power supply 1 is constituted by four
bridge-connected rectifying diodes 2a to 2d. To the output of the
rectifier 2, the step-up converters 3a and 3b are connected in
parallel.
[0247] The step-up converter 3a is constituted by a step-up reactor
4a, a switching element 5a such as an IGBT, and a reverse current
prevention element 6a such as a fast recovery diode. The step-up
converter 3b is constituted by the step-up reactor 4b, the
switching element 5b such as the IGBT, and the reverse current
prevention element 6b such as a fast recovery diode, as well.
[0248] By switching control means 7, the switching of the switching
elements 5a and 5b is controlled and the output of the rectifier 2
is boosted.
[0249] An FRD is provided which is connected in inverse-parallel
with the switching elements 5a and 5b, respectively. The FRD
prevents the switching element 5 from breakdown by the surge that
is generated when the switching element 5 turns off.
[0250] In the present embodiment, the step-up converter 3 is not
limited, but any switching converter may be applied such as a
step-up converter, a step-down converter, a step-up/step-down
converter.
[0251] The output of the step-up converters 3a and 3b is smoothed
by the smoothing capacitor 8. A load 10 is connected with the
output of the step-up converters 3a and 3b and the smoothed output
of the step-up converters 3a and 3b is applied.
[0252] The load 10 is constituted by an inverter circuit 11 that
converts the output of the step-up converters 3a and 3b into AC
voltage and a motor 12 connected with the inverter circuit 11.
[0253] The inverter circuit 11 is constituted by bridge-connected
switching elements 11a to 11f. In each switching element 11a to
11f, a fast recovery diode is built-in in inverse-parallel. The
built-in fast recovery diode functions to flow a free-wheeling
current when the switching elements 11a to 11f turn off. The
inverter circuit 11 is subjected to PWM control, for example, by
the inverter drive means 50 to convert input DC voltage into AC
voltage having arbitrary voltages and frequencies to drive the
motor 12.
[0254] The motor drive control apparatus is constituted by the
converter circuit, the inverter circuit 11, and inverter drive
means 50.
[0255] In FIG. 12, descriptions are given to a case where the load
10 composed of the inverter circuit 11 and the motor 12 is provided
with the converter circuit of Embodiment 1. However, the present
invention is not limited thereto, but the load 10 composed of the
inverter circuit 11 and the motor 12 may be provided with any
configuration of the above Embodiments 1 to 5.
[0256] It goes without saying that the same effect as the above
Embodiments 1 to 5 can be obtained by operating the motor 12 with
such a configuration.
Embodiment 7
[0257] FIG. 13 is a configuration diagram of an air-conditioner
according to Embodiment 7 of the present invention.
[0258] In FIG. 13, an air-conditioner according to the present
embodiment includes an outdoor unit 310 and an indoor unit 320. The
outdoor unit 310 includes a refrigerant compressor 311 that is
connected with a refrigerant circuit, not shown, and configures a
refrigerant cycle and a blower 312 for the outdoor unit that blows
in a heat exchanger, not shown. The refrigerant compressor 311 and
the blower 312 for the outdoor unit are driven by a motor 12 that
is controlled by the motor drive control apparatus according to the
above Embodiment 6. It goes without saying that the same effect as
the above Embodiments 1 to 6 can be obtained by operating the motor
12 with such a configuration.
Embodiment 8
[0259] FIG. 14 is a configuration diagram of a refrigerator
according to Embodiment 8 of the present invention.
[0260] As shown in FIG. 14, a refrigerator 400 includes a
refrigerant compressor 401 that configures a refrigeration cycle
connected with a refrigeration circuit, not shown, and a cool air
circulation blower 404 that that sends cool air generated in a
cooler 403 installed in a cooling compartment 402 to refrigerating
compartment, freezing compartment, and the like. The refrigerant
compressor 401 and the cool air circulation blower 404 are driven
by the motor 12 that is controlled by the motor drive control
apparatus according to the above Embodiment 6. It goes without
saying that the same effect as the above Embodiments 1 to 6 can be
obtained by operating the motor 12 with such a configuration.
Embodiment 9
[0261] In Embodiment 9, an example of configuration is shown when
an induction heating cooker is made to be an object load regarding
the converter circuit of the above Embodiments 1 to 5.
[0262] FIG. 15 is a configuration diagram of the induction heating
cooker according to Embodiment 9 of the present invention.
[0263] In FIG. 15, the rectifier 2 that rectifies the AC voltage of
the commercial power supply 1 is constituted by four
bridge-connected rectifying diodes 2a to 2d. To the output of the
rectifier 2, the step-up converters 3a and 3b are connected in
parallel.
[0264] The step-up converter 3a is constituted by a step-up reactor
4a, a switching element 5a such as an IGBT, and a reverse current
prevention element 6a such as a fast recovery diode. The step-up
converter 3b is constituted by the step-up reactor 4b, the
switching element 5b such as the IGBT, and the reverse current
prevention element 6b such as the fast recovery diode, as well.
[0265] By switching control means 7, the switching of the switching
elements 5a and 5b is controlled and the output of the rectifier 2
is boosted.
[0266] An FRD is provided which is connected in inverse-parallel
with the switching elements 5a and 5b, respectively. The FRD
prevents the switching element 5 from breakdown by the surge that
is generated when the switching element 5 turns off.
[0267] In the present embodiment, the step-up converter 3 is not
limited, but any switching converter may be applied such as a
step-up converter, a step-down converter, a step-up/step-down
converter.
[0268] The output of the step-up converters 3a and 3b is smoothed
by the smoothing capacitor 8. A load 10 is connected with the
output of the step-up converters 3a and 3b and the smoothed output
of the step-up converters 3a and 3b is applied.
[0269] The load 10 is constituted by an inverter circuit 11 that
converts the output of the step-up converters 3a and 3b into AC
voltage and a load circuit 13 connected with the inverter circuit
11.
[0270] The inverter circuit 11 is constituted by bridge-connecting
switching elements 11a to 11f.
[0271] The inverter circuit 11 is driven by the inverter drive
means 50 to convert the DC voltage smoothed by the smoothing
capacitor 8.
[0272] To the output point of the inverter circuit 11, a load
circuit 13 composed of an induction heating coil 14 and a resonance
capacitor 15 is connected. A high-frequency voltage converted by
the inverter circuit 11 is applied to the load circuit 13. Thereby,
an object to be heated (not shown) mounted on the induction heating
cooker is subjected to induction heating.
[0273] In FIG. 15, a case is shown where the load 10 composed of
the inverter circuit 11 and the load circuit 13 is provided with
the converter circuit of the above Embodiment 1. However, the
present invention is not limited thereto, but the load 10 composed
of the inverter circuit 11 and the load circuit 13 may be provided
with any configuration of the above Embodiments 1 to 5.
[0274] It goes without saying that the same effect as the above
Embodiments 1 to 5 can be obtained by operating the load circuit 13
by such an induction heating cooker.
[0275] For example, as shown in FIG. 12 or 15, when the inverter
circuit 11 is connected as the load, since a large-capacity
switching element used for the switching converter is usually
required, it is difficult to be shared with the switching element
used for the inverter circuit.
[0276] According to Embodiments 1 to 9, the switching elements can
be shared and cost reduction is made possible eventually by
selecting the number of the step-up converters which can be
configured by the switching elements 5 used in the converter
circuit and the switching elements 11a to 11f used in the inverter
circuit 11 having the same capacity.
[0277] In the above, descriptions are given to embodiments of the
present invention. However, the present invention is not limited
thereto, but it goes without saying that it is subject to change
without being limited by embodiments and without departing from the
spirit and scope of the invention such as to employ a three-phase
power source instead of the single phase for the commercial power
supply 1.
* * * * *