JP2001145357A - Ac-dc converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the size and to facilitate increase in the capacity of the converter. SOLUTION: In the AC-DC converter, an additional switching circuit 3B, an additional circulating diode 16B and an additional DC reactor 17B having the same constitution as that of a switching circuit 3A are connected in parallel with the circuit 3A, a circulating diode 16A and a DC reactor 17A between a filter 2 and a smoothing capacitor 18, the switching phase of the circuit 3B is delayed by π/2 [rad] to the circuit 3A, and the circuits 3A, 3B are controlled ON, OFF. Thus, a low order harmonic current at the output side of the filter 2 can be suppressed, and the inductance of the reactor and the electrostatic capacity of the capacitor for constituting the filter 2 can be reduced. Therefore, the filter 2 is reduced in size, the converter can be reduced in size and increased in its capacity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC-DC converter for improving an input power factor by controlling an AC input current in a sine wave form.
It belongs to the C converter.

[0002]

2. Description of the Related Art Input power supplies such as switching regulators
The part consists of a rectifier diode and a smoothing capacitor.
A rectifier circuit of a capacitor input type is generally used. I
However, a rectifier circuit of the capacitor input type
Charge the smoothing capacitor only near the maximum value of the current input current.
Flow, the conduction angle of the input current waveform is narrow and the input force
There was a problem that the rate was as low as about 0.6. So, for example,
As shown in FIG. 4, the input current is controlled by controlling the AC input current in a sine wave shape.
Step-down AC-DC converter with improved power factor
Have been. The AC-DC converter shown in FIG.
And a three-phase AC power supply (1)
Connected to the filter circuit (2)
The first to sixth as three pairs of switching elements
IGBT (Insulated Gate Bipolar Transistor) (4
-9) and the first to sixth IGBTs (4 to 9) in series.
1st to 6th backflow as continuous backflow prevention rectifier
Prevention diode (10-15) and filter circuit (2)
Switching circuit (3) connected to the output terminal of
Rectification for reflux connected between the output terminals of the switching circuit (3)
A reflux diode (16) as an element and a reflux diode
Smoothing core connected to DC (16) via DC reactor (17)
The current I flowing through the capacitor (18) and the DC reactor (17) _L
Is the voltage V corresponding to the current_LCurrent detection to detect as
Unit (19), U-phase, V-phase and W-phase from three-phase AC power supply (1)
AC input voltage V_U, V_V, V_WPhase voltage detection
The lance (20) and the detection voltage V of the phase voltage detection transformer (20)
_U, V_V, V_WAnd the detection voltage V of the current detector (19)_LAnd smooth
Voltage V of capacitor (18)_DCAccording to the switching circuit
Gate ends of the first to sixth IGBTs (4 to 9) in (3)
The first to sixth on / off control signals V_G1, V_G2;
V_G3, V_G4; V_G5, V_G6To the first to sixth IGBTs
(4 to 9) on / off control circuit (21).
You.

As shown in FIG. 5, a control circuit (21) includes a reference power supply (22) for generating a reference voltage V _RD for defining a reference value of a DC output voltage _VDC output from both ends of a smoothing capacitor (18).
A first error amplifier (23) for comparing the voltage _VDC of the smoothing capacitor (18) with the reference voltage V _RD of the reference power supply (22) and outputting an error voltage signal V _E1 thereof; and a current detector ( A second error amplifier (24) for comparing the detected voltage _VL of the first error amplifier (19) with the output signal _VE1 of the first error amplifier (23) and outputting the error voltage signal _VE2 ; and a phase voltage detecting transformer. (20) Detection voltage V _U , V
U-phase, V-phase and W-phase current reference signals V _RUV , V _RVW , V based on _V , V _W and the output signal V _E2 of the second error amplifier (24).
A phase current reference signal generating circuit for generating a _RWU (25), triangular wave oscillation that generates a triangular wave signal V _T of the three-phase AC power source (1) sufficiently higher than the frequency (50-60 Hz) of (1-100 kHz) Circuit (26) and the phase current reference signal generation circuit (25)
Phase, the current reference signal V _RUV V-phase and W-phase, V _RVW, V _RWU the triangular wave oscillation circuit (26) of each phase current is compared with the triangular wave signal V _T of the PWM modulation signal V _PUV, V _PVW, V P that outputs _PWU
The WM comparators (27), (28), (29) and the PWM modulation signals V _PUV , V _PVW , V of the PWM comparators (27), (28), (29)
"1" _PWU, "0" or 3 values of the line current pulse signal V _SU "-1" _{(= V PUV -V PWU),} V SV (= V PVW -V P UV), V
_SW (= V _PWU -V _PVW ) line current pulse converter (3
0) and the values of the line current pulse signals V _SU , V _SV , and V _SW , respectively, to determine the first to sixth IGBs of the switching circuit (3).
The first to sixth on / off signals applied to each gate terminal of T (4 to 9)
Off control signal _{V G1, V G2; V G3} , V G4; V G5, constructed from a control signal output circuit for outputting a V _G6 (31).

[0004] The control signal output circuit (31) is provided for each line current pulse.
Signal V_SU, V_SV, V_SWWhen either is “1”,
First, third or fifth IGBT on the positive side of the corresponding arm
(4), (1), (3) or (3)
5 ON / OFF control signal V_G1, V _G3, V_G5To the high (H) level
And the first, third or fifth IGBTs (4), (6), (8)
Turn on. In addition, each line current pulse signal V_SU, V_SV,
V_SWIf either of the two is "-1", the corresponding
The second, fourth or sixth IGBT (5), (7), (9) on the negative side of the
, Fourth or sixth ON / OFF applied to the gate terminal of
Control signal V_G2, V_G4, V_G6To the high (H) level
2. Turn on the fourth or sixth IGBT (5), (7), (9)
I do. Further, each line current pulse signal V_SU, V_SV, V_SWAny of
Is 0, the positive side of the corresponding arm and
Negative first and second IGBTs (4,5), third and fourth
IGBT (6,7) or fifth and sixth IGBT (8,9)
First, second, third and fourth or fifth
And the sixth on / off control signal V_G1, V_G2; V_G3, V_G4; V
_G5, V_G6Is set to a low (L) level, and the first and
Second IGBT (4,5), third and fourth IGBT (6,7) or
Turns off the fifth and sixth IGBTs (8, 9).

The operation of the AC-DC converter shown in FIG. 4 is as follows. For example, as shown in FIG. 6A, when the U-phase AC input current I _U of the three-phase AC power supply (1) is in the positive half cycle, the detection voltage _{VL of the} current detector (19) and the phase voltage detection are detected. the detected voltage _{V U,} V V, V _W and the first on-off control signal V _G1 control circuit that is PWM-modulated according to the voltage V _DC of the smoothing capacitor (18) of use transformer (20) (21) From the control signal output circuit (31) to the first IGBT in the switching circuit (3).
The signal is input to the gate terminal of (4), and the first IGBT (4) is turned on / off. At the same time, the second IGBT (5)
Second on / off control signal V input to the gate terminal of
_G2 is constant at a low level, and the second IGBT (5) is turned off. Also, three-phase when the AC input current I _U of the U-phase negative half cycle of the AC power source (1), the detected voltage V _L and the phase voltage detection voltage detecting transformer (20) of the current detector (19) V _U ,
V _V, V _W and the second on-off control signal V _G2 control circuit (21) the control signal output circuit (31) from the switching circuit in which the PWM modulation in response to the voltage V _DC of the smoothing capacitor (18) Input to the gate terminal of the second IGBT (5) in (3),
The second IGBT (5) is turned on and off. At the same time, the first on / off control signal V _G1 input to the gate terminal of the first IGBT (4) becomes constant at a low level, and the first IGBT (4) is turned off. Thus, the current I _U0 input to the U-phase arm of the switching circuit (3) has a positive / negative pulse current waveform having a _peak value I _U0P as shown in FIG. 6B. The positive-negative pulse-shaped current I _U0 input to the U-phase arm of the switching circuit (3) has a low-order harmonic component removed by the filter circuit (2), and becomes a sinusoidal current having only a fundamental component. The V-phase arm and the W-phase arm perform substantially the same operation as described above. However, when the first IGBT (4) of the U-phase arm is on, one of the fourth IGBT (7) of the V-phase arm or the sixth IGBT (9) of the W-phase arm is on. , Second IG of U-phase arm
When BT (5) is on, the third IGB of the V-phase arm
One of T (6) and the fifth IGBT (8) of the W-phase arm is turned on.

Therefore, for example, a switching circuit (3)
When the first IGBT (4) of the U-phase arm and the fourth IGBT (7) of the V-phase arm are on, the three-phase AC power supply (1)
U-phase output, filter circuit (2), first backflow prevention diode (10), first IGBT (4), DC reactor (1
7), smoothing capacitor (18) and load (32), fourth IGB
T (7), fourth backflow prevention diode (13), filter circuit (2), current flows through the V-phase output path of three-phase AC power supply (1), and energy is accumulated in DC reactor (17). And the smoothing capacitor (18) is charged. Thereafter, when the first IGBT (4) of the U-phase arm of the switching circuit (3) is turned off, the stored energy of the DC reactor (17) and the charge of the smoothing capacitor (18) are released, and the DC reactor (1) is released.
7), current flows through the path of the smoothing capacitor (18), the load (32), and the return diode (16). When the second IGBT (5) of the U-phase arm and the third IGBT (6) of the V-phase arm of the switching circuit (3) are in the ON state, the V-phase output of the three-phase AC power supply (1), Filter circuit (2), third backflow prevention diode (12), third IGBT (6), DC reactor
(17), smoothing capacitor (18) and load (32), second IG
Current flows through the path of the BT (5), the second backflow prevention diode (11), the filter circuit (2), and the U-phase output of the three-phase AC power supply (1), and energy is stored in the DC reactor (17). And the smoothing capacitor (18) is charged. Thereafter, when the second IGBT (5) of the U-phase arm of the switching circuit (3) is turned off, the stored energy of the DC reactor (17) and the charge of the smoothing capacitor (18) are released, and the DC reactor (1) is released.
7), current flows through the path of the smoothing capacitor (18), the load (32), and the return diode (16). Switching circuit (3)
And fourth IGBTs (6, 7) and W
When the fifth and sixth IGBTs (8, 9) of the phase arm perform on / off operations, or the first and second IGBTs (4, 5) and the W-phase arm of the U-phase arm of the switching circuit (3) In the case where the fifth and sixth IGBTs (8, 9) perform on / off operations, substantially the same operation as described above is performed. Thus, the flow at a constant level of the DC current I _L DC reactor (17) as shown in FIG. 6 (C), the DC output voltage V _DC is generated across the smoothing capacitor (18).

The first to sixth IGs of the switching circuit (3)
Smoothing capacitor (18) by ON / OFF operation of BT (4-9)
DC output voltage _VDC output from both ends of the control circuit (2
The first error amplifier (23) in (1) compares the reference voltage V _RD of the reference power supply (22) with the DC output voltage _VDC and the reference voltage V _RD.
Of the error voltage signal V _E1 is outputted from the first error amplifier (23). The error voltage signal _VE1 of the first error amplifier (23) is compared with the detection voltage _{VL of} the DC reactor (17) detected by the current detector (19) in the second error amplifier (24),
Error voltage signal V _E2 of the error voltage signal V _E1 and the detection voltage V _L
Is output from the second error amplifier (24). The error voltage signal V _E2 of the second error amplifier (24) is _supplied to a phase voltage detection transformer.
The phase voltage reference signal generation circuit (25) is input together with the detection voltages V _U , V _V , and V _{W of} (20), and the phase current reference signal is generated based on the detection voltages V _U , V _V , and V _W and the error voltage signal V _E2. The signal generation circuit 25 outputs U-phase, V-phase, and W-phase current reference signals V _RUV , V _RVW , and V _RWU as shown in FIG. The U-phase, V-phase and W-phase current reference signals V _RUV ,
V _RVW and V _RWU are the PWM comparators (27), (28) and (29)
Are respectively compared with a triangular wave signal V _T of the triangular wave oscillation circuit (26) in, when the current reference signal V _RUV, the relationship between V _RVW, V _RWU a triangular wave signal V _T of _{V RUV, V RVW, V RWU} <V T PWM modulation signals V _PUV , V _PVW , V D as shown in FIGS. _7B , _7C , and _7D , which become low when V _RUV , V _RVW , and V _RWU > V _{T. PWU sets} each PWM comparator (27), (2
8), output from (29). Each PWM comparator (27), (2
The PWM modulation signals V _PUV , V _PVW and V _PWU of (8) and (29) are converted by the line current pulse conversion circuit (30) into line currents as shown in FIGS. 7 (E), (F) and (G), respectively. Pulse signal V _PUV −V _PWU = V _SU ; V
It is converted to _{V PWU -V PVW = V SW;} PVW -V PUV = V SV.
Line current pulse signals V _SU and V of the line current pulse conversion circuit (30)
_The control signal output circuit (31) determines the values of _SV and V _{SW, that} is, “1”, “0” or “−1”, respectively, and the control signal output circuit (31) outputs the switching circuit (3). First to
_{V G3, V G4;; V} G5, V G6 are respectively assigned first to sixth on-off control signal V _G1, V _G2 to the sixth gate terminal of each of IGBT (4 to 9) of the.

[0008] Thus, U-phase, V-phase and W-phase of the AC input voltage V _U of the current I _L and the three-phase AC power source flows through the DC reactor (17) (1), V V, V W and a smoothing capacitor (18 ), The first to sixth IGBTs (4 to 9) in the switching circuit (3) are turned on and off by the control circuit (21) in accordance with the DC output voltage _VDC at both ends of the three-phase AC power supply (1). ) From the filter circuit
The AC input currents I _U0 , I _V0 , I _W0 flowing to the U-phase, V-phase and W-phase arms of the switching circuit (3) via (2) are controlled in a sine wave form, and from both ends of the smoothing capacitor (18). The output DC output voltage _VDC is maintained at a constant level.

In the AC-DC converter shown in FIG. 4, an AC input current I flowing from a three-phase AC power supply (1) to a U-phase, V-phase and W-phase arm of a switching circuit (3) via a filter circuit (2). _U0 , I _V0 and I _W0 are controlled in a sine wave form, and the DC output voltage V output from both ends of the smoothing capacitor (18).
_{Since DC} is maintained at a constant level, the input power factor is approximately 1.0
And a stable DC output voltage _VDC can be obtained.

[0010]

By the way, FIG.
In the AC-DC converter, each of the switching circuits (3)
U-phase, V-phase and W-phase currents I input to the phase arm_U0,
I_V0, I_W0Is modulated by PWM as shown in FIG.
The resulting positive and negative pulse current waveforms are obtained. Therefore, the switch
U-phase, V-phase input to each arm of the
W-phase current I_U0, I _V0, I_W0Contains many low-order harmonics and
The peak value is also large, so the resources constituting the filter circuit (2)
Actuator inductance and capacitor capacitance
The value becomes large, and the filter circuit (2) becomes large. this
Therefore, it becomes an obstacle when downsizing the AC-DC converter.
In particular, in large-capacity AC-DC converters,
Road (2) is quite large, making its design extremely difficult
Met.

Accordingly, an object of the present invention is to provide an AC-DC converter that can be reduced in size and can be easily increased in capacity.

[0012]

SUMMARY OF THE INVENTION AC-DC according to the present invention
The converter is a filter circuit connected to the AC power supply (1)
(2) and the switching circuit connected to the filter circuit (2)
(3A) and the output terminal of the switching circuit (3A).
DC to the rectifier for reflux (16A) and the rectifier for reflux (16A)
Smoothing capacitor (1) connected via reactor (17A)
8) and has the same configuration as the switching circuit (3A)
Additional switching circuit (3B) and DC reactor (17
An additional DC reactor (17B) having the same configuration as (A)
And a switching circuit (3A) and a DC reactor (1
7A) in parallel with additional switching circuit (3B) and additional DC
Reactor (17B) and filter circuit (2) and smoothing capacitor
(18), DC reactor (17A) and additional
The current flowing through the DC reactor (17B) (I_L) Depending on the level
Switching circuit (3A) and additional switching circuit (3
By turning on and off B), the AC power supply (1)
The switching circuit (3A) and the attachment via the filter circuit (2)
AC input current flowing through the additional switching circuit (3B) (I _U0, I
_V0, I_W0) As a sine wave and a smoothing capacitor (1
8) Constant voltage DC output (V_DC). This
The AC input current (I _U0, I_V0,
I_W0), The lower harmonics contained in the
Is approximately 倍 times as high. Therefore, the filter times
The reactor and capacitor that make up the path (2)
Therefore, the filter circuit (2) can be made smaller and the AC-DC
It is possible to reduce the size of the inverter. Also, switch
Additional switch having the same configuration as the switching circuit (3A)
Switch (3B) and additional DC reactor (17B)
Connected in parallel with the switching circuit (3A) and DC reactor (17A).
Therefore, it is easy to obtain a large capacity AC-DC converter.
Can be.

In one embodiment of the present invention, the switching circuit (3A) and the additional switching circuit (3B) include a plurality of pairs of switching elements (4A-9A; 4B-9
B) and a plurality of switching elements (4A to 9A; 4B to 9B) and a rectifying element (10A to 15
A; 10B to 15B).

Further, in one embodiment of the present invention, in addition to the level of the current (I _L ) flowing through the DC reactor (17A) and the additional DC reactor (17B), the voltage (V _U , V _V ,
V _W ) and the voltage (V _DC ) of the smoothing capacitor (18), the switching circuit (3A) and the additional switching circuit (3B) are turned on / off. This allows the switching circuit to be switched from the AC power supply (1) through the filter circuit (2).
(3A) and the AC input current (I _U0 , I _V0 , I _W0 ) flowing to the additional switching circuit (3B) are controlled to a more accurate sine wave, and a more stable constant-voltage DC output from the smoothing capacitor (18).
(V _DC ).

In a modified embodiment of the present invention, a plurality of additional switching circuits (3B) and a plurality of additional DC reactors (17B) are combined with a filter circuit (2) and a smoothing capacitor (18).
And a switching circuit (3A) and a plurality of additional switching circuits (3B) depending on the level of the current (I _L ) flowing through the DC reactor (17A) and the plurality of additional DC reactors (17B). Of the switching circuit (3) from the AC power supply (1) via the filter circuit (2)
A) and the AC input currents (I _U0 , I _V0 , I _W0 ) flowing through the plurality of additional switching circuits (3B) are controlled in a sinusoidal manner, and a constant-voltage DC output (V _DC ) is supplied from the smoothing capacitor (18). Take out. As a result, low-order harmonics contained in the AC input current (I _U0 , I _V0 , I _W0 ) on the output side of the filter circuit (2) are further suppressed, and the peak value of the pulse-like current is reduced by the switching circuit (3A). And by the number of stages of the plurality of additional switching circuits (3B). For this reason, the reactors and capacitors constituting the filter circuit (2) are further reduced in size to make the filter circuit (2)
Can be further reduced in size. Further, a plurality of additional switching circuits (3B) having the same configuration as the switching circuit (3A) and a plurality of additional DC reactors (17B) are connected to a filter circuit (2).
Since it is connected between the capacitor and the smoothing capacitor (18), an AC-DC converter having a larger capacity can be easily obtained.

Further, in one embodiment of the present invention or a modified embodiment of the present invention, the number of stages of the switching circuit (3A) and the additional switching circuit (3B) is determined with respect to one switching cycle of the switching circuit (3A). A switching circuit that shifts the switching phase by an angle corresponding to the reciprocal multiple
(3A) and the additional switching circuit (3B) are turned on / off. As a result, low-order harmonics included in the AC input current (I _U0 , I _V0 , I _W0 ) on the output side of the filter circuit (2) are further suppressed, and the peak value of the pulse-like current is reduced by the switching circuit.
(3A) and the number of stages of the plurality of additional switching circuits (3B) are reciprocal times, and the switching frequency is the number of stages of the switching circuit (3A) and the plurality of additional switching circuits (3B). Therefore, the values of the inductance of the reactor and the capacitance of the capacitor constituting the filter circuit (2) can be reduced according to the number of stages of the switching circuit (3A) and the plurality of additional switching circuits (3B). Therefore, the size of the filter circuit (2) can be further reduced in accordance with the number of stages of the switching circuit (3A) and the plurality of additional switching circuits (3B).

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an AC-DC converter according to the present invention will be described.
One embodiment of an inverter will be described with reference to FIGS.
You. However, in these drawings, the locations shown in FIGS.
The qualitatively the same parts are denoted by the same reference numerals, and their description is omitted.
Abbreviate. As shown in FIG. 1, AC-DC of the present embodiment
The converter has the same configuration as the switching circuit (3A).
Additional switching circuit (3B), additional reflux diode
Switch (16B) and additional DC reactor (17B)
Circuit (3A), reflux diode (16A) and DC reactor
Filter circuit (2) and smoothing capacitor (18) in parallel with the filter (17A)
And additional to the switching circuit (3A)
Set the switching phase of the switching circuit (3B) to π / 2 [ra
d], the current I flowing through the DC reactor (17A)
_L1And the current I flowing through the additional DC reactor (17B)_L2With
Sum current I_LSwitching circuit (3A) and
On / off control of additional switching circuit (3B)
There are features. Therefore, in the control circuit (21) of the present embodiment,
Is output from the control signal output circuit (31) as shown in FIG.
First to sixth on / off control signals V_A1~ V_A6Phase of
FIG. 5 shows a delay circuit (33) for delaying the signal by π / 2 [rad].
Provided in the control circuit (21) and output from the control signal output circuit (31).
First to sixth ON / OFF control signals V_A1~ V_A6Yo
The first to sixth on-phases that are delayed by π / 2 [rad]
OFF control signal V_B1~ V_B6Is added via the delay circuit (33)
First to sixth IGBTs (4B to 9B) of switching circuit (3B)
To each gate terminal. In addition, the current of the present embodiment
The detector (19) detects the current I flowing through the DC reactor (17A)._L1
And the current I flowing through the additional DC reactor (17B)_L2Sum with
Current I_LIs the voltage V corresponding to the current _LDetected as
In addition, a reflux diode (16A) and additional reflux diode
The negative line between the load (16B) and the smoothing capacitor (18).
Are the DC reactor (17A) and the additional DC
DC reactor (34A) and additional DC
The flow reactor (34B) is connected. Other circuit structure
The configuration is almost the same as the conventional AC-DC converter shown in FIG.
It is.

Next, the operation of the AC-DC converter shown in FIG. 1 will be described. For example, when the AC input current I _U of the U phase of the three-phase AC power source (1) shown in FIG. 3 (A) is a positive half cycle, the current detector (19) of the detected voltage V _L and the phase voltage detecting transformer (20) of the detected voltage _{V U,} V V, V _W and control of the first on-off control signal V _A1 that is PWM-modulated according to the voltage V _DC control circuit (21) of the smoothing capacitor (18) From the signal output circuit (31) to the first IGBT (4) in the switching circuit (3A).
The first IGBT (4A) of the switching circuit (3A) is turned on and off by being input to the gate terminal of (A). At the same time, the second on / off control signal V _A2 input to the gate terminal of the second IGBT (5A) of the switching circuit (3A) becomes constant at a low level, and the second IGBT (5A) of the switching circuit (3A) becomes constant.
The BT (5A) is turned off. Further, when the AC input current I _U of the U phase of the three-phase AC power source (1) is negative half cycle, the current detector (19) of the detected voltage V _L and the phase voltage detecting transformer (2
The detected voltage V _U of 0), _V V, V _W and the second on-off control signal of the control signal V _A2 is the control circuit (21) within which is PWM-modulated according to the voltage V _DC of the smoothing capacitor (18) The input from the output circuit (31) to the gate terminal of the second IGBT (5A) of the switching circuit (3A), the second IGB of the switching circuit (3A)
T (5A) is turned on and off. At the same time, the first on / off control signal V _A1 input to the gate terminal of the first IGBT (4A) of the switching circuit (3A) becomes constant at a low level, and the first IGBT of the switching circuit (3A) becomes low. (4A) is turned off. Thus, the current I _U1 input to the U-phase arm of the switching circuit (3A) has a positive / negative pulse current waveform as shown in FIG. 3 (B).

On the other hand, when the U-phase AC input current I _{U of the} three-phase AC power supply (1) shown in FIG. 3A is during a positive half cycle, the first IGBT ( The first ON / OFF control signal delayed by π / 2 [rad] from the control signal output circuit (31) in the control circuit (21) via the delay circuit (33) is connected to the gate terminal of 4B). V _B1 is input and the switching phase of the additional switching circuit (3A) is delayed by π / 2 [rad] with respect to the first IGBT (4A) of the switching circuit (3A).
The first IGBT (4B) of B) is turned on / off. At the same time, the second IGB of the additional switching circuit (3B)
The second on / off control signal V _B2 input to the gate terminal of T (5B) becomes constant at a low level, and the second IGBT (5B) of the additional switching circuit (3B) is turned off. Also,
When the AC input current I _U of the U phase of the three-phase AC power source (1) is negative half cycle, the second IGB additional switching circuit (3B)
The gate terminal of T (5B) has a second ON / OFF delayed by π / 2 [rad] from a control signal output circuit (31) in the control circuit (21) via a delay circuit (33). The control signal V _B2 is input, the switching phase is delayed by π / 2 [rad] with respect to the second IGBT (5A) of the switching circuit (3A), and the second IGBT (5B) of the additional switching circuit (3B) is delayed. ) Is turned on and off. At the same time, additional switching circuits (3
B) The first input to the gate terminal of the first IGBT (4B)
The on / off control signal V _B1 is low and constant, and the first IGBT (4B) in the additional switching circuit (3B) is turned off. As a result, as shown in FIG. 3C, the current I input to the U-phase arm of the additional switching circuit (3B)
_U2 has a positive / negative pulse current waveform delayed by π / 2 [rad] with respect to the current I _U1 input to the U-phase arm of the switching circuit (3A) shown in FIG.

Therefore, the positive and negative pulse current I _U1 input to the U-phase arm of the switching circuit (3A) and the positive and negative pulse current I _U input to the U-phase arm of the additional switching circuit (3B) The sum of _U2 and I _U1 + I _U2 is the filter circuit
Since the current I _U0 on the output side of (2) is obtained, a convex current waveform in which low-order harmonics are suppressed is obtained as shown in FIG. _{3D, and the peak} value I _U0P of the pulse-shaped current is 1 / At the same time, the switching frequency doubles. The current I _U0 on the output side of the filter circuit (2) shown in FIG. _3D has a sine-wave current consisting of only the fundamental wave component, with the harmonic component removed by the filter circuit (2). The V-phase arm and the W-phase arm of each switching circuit (3A, 3B) perform substantially the same operation as described above. However, in any of the switching circuits (3A, 3B), when the first IGBT (4) of the U-phase arm is in the ON state, the fourth IGBT (7) of the V-phase arm or the sixth IGBT (7) of the W-phase arm. IG
When any one of the BTs (9) is on and the second IGBT (5) of the U-phase arm is on, the third IGBT (6) of the V-phase arm or the fifth IGBT of the W-phase arm Any one of (8) is turned on. The details of the basic operation of the main circuit and the operation of the control circuit (21) other than those described above are substantially the same as those of the conventional AC-DC converter shown in FIG.

In the AC-DC converter of the present embodiment, the switching phase of the additional switching circuit (3B) connected in parallel with the switching circuit (3A) is set to π / 2.
[Rad] with only delays, by controlling on and off according to the level of the sum current I _L between the current I _L2 flowing to additional DC reactor current I _L1 flowing to DC reactor (17A) (17B), The low-order harmonics of the U-phase, V-phase, and W-phase currents I _U0 , I _V0 , I _W0 at the output side of the filter circuit (2) are suppressed, and the _peak values I _U0P , I _V0P , I of pulsed currents are suppressed.
_W0P becomes 1/2 times and the switching frequency becomes 2 times. As a result, the inductance of the reactor constituting the filter circuit (2) and the value of the capacitance of the capacitor become 1/2 ² times = 1/4 times, and the external shape of these components is reduced. Can be downsized. Further, the first to sixth IGs constituting each switching circuit (3A, 3B)
Since the maximum value of the current flowing through the BT (4A to 9A; 4B to 9B) is also halved, the size of each IGBT (4A to 9A; 4B to 9B) and the size of each switching circuit (3A, 3B) are reduced. Can be Therefore, the size of the filter circuit (2) and each of the switching circuits (3A, 3B) can be reduced, and the size of the AC-DC converter can be reduced. Further, since the switching circuit (3), the reflux diode (16), and the DC reactor (17) shown in FIG. 4 are connected in two stages in parallel, a large-capacity AC-DC converter can be easily obtained. .

The embodiments of the present invention are not limited to the above-described embodiments, and various modifications are possible. For example, in the above-described embodiment, an embodiment in which an IGBT (insulated gate bipolar transistor) is used as a switching element forming the switching circuit (3) has been described.
(MOS type field effect transistor), a junction type bipolar transistor or a J-FET (junction type field effect transistor) can also be used. Further, in the above embodiment, the switching circuit (3), the reflux diode (16), and the DC reactor (17) are connected in two stages in parallel between the filter circuit (2) and the smoothing capacitor (18). As shown, 2
It is also possible to connect more than one stage in parallel. In this case, the switching phase of each stage of the switching circuit (3) is an angle corresponding to the reciprocal multiple of the number of stages of the switching circuit (3) with respect to one switching cycle of the switching circuit (3),
That is, π / n [rad] (n: the number of stages of the switching circuit (3))
If the on / off control is performed by shifting each time, the filter circuit (2)
The _peak values I _U0P , I _V0P , I _W0P of the U-phase, V-phase and W-phase pulse-like currents I _U0 , I _V0 , I _W0 at the output side are 1 / n times and the switching frequency is n times. Become. Therefore, the inductance of the reactor constituting the filter circuit (2) and the value of the capacitance of the capacitor become 1 / n ² times, which can be further reduced as compared with the above embodiment. There is an advantage that the size can be further reduced according to the number of stages in 3). Further, the switching circuit (3), the reflux diode (16), and the DC reactor (17) are connected in two or more stages between the filter circuit (2) and the smoothing capacitor (18). An AC-DC converter with an even larger capacity can be obtained. Further, it can be easily understood that the present invention can be applied not only to the case of the AC-DC converter for three-phase AC but also to the case of an AC-DC converter for single-phase AC or multi-phase AC of three or more phases.

[0023]

According to the present invention, by connecting a switching circuit (3) and a DC reactor (17) at least two stages in parallel between a filter circuit (2) and a smoothing capacitor (18), The low-order harmonic current at the output side of the circuit (2) can be suppressed, and the inductance of the reactor and the capacitance of the capacitor constituting the filter circuit (2) can be reduced. As a result, the size of the AC-DC converter can be reduced, and the design of a large-capacity AC-DC converter becomes easy.

[Brief description of the drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of an AC-DC converter according to the present invention.

FIG. 2 is a circuit block diagram showing an internal configuration of a control circuit in FIG.

FIG. 3 is a waveform chart showing currents at various parts of a main circuit of the AC-DC converter of FIG.

FIG. 4 is an electric circuit diagram showing a conventional AC-DC converter.

5 is a circuit block diagram showing an internal configuration of a control circuit in FIG.

6 is a waveform chart showing currents at various parts of a main circuit of the AC-DC converter of FIG.

FIG. 7 is a timing chart showing signals of various parts of the control circuit of FIG. 5;

[Explanation of symbols]

(1) ... three-phase AC power supply (AC power supply), (2) filter circuit, (3), (3A) switching circuit, (3B) additional switching circuit, (4-9), (4A-9A; 4B-9B)
First to sixth IGBTs (switching elements), (10
~ 15), (10A ~ 15A; 10B ~ 15B) ・ ・ First to sixth backflow prevention diodes (backflow prevention rectifiers), (16), (16A) ・ ・
Reflux diode (reflux rectifier), (16B) additional reflux diode, (17), (17A) DC reactor, (17B) additional DC reactor, (18) smoothing capacitor , (19) ... current detector, (20) ... phase voltage detection transformer, (21) ... control circuit, (22) ... reference power supply, (23) ... first error amplifier, (24) 2nd
Error amplifier, (25) ・ ・ Phase current reference signal generation circuit,
(26) ・ ・ Triangle wave oscillation circuit, (27), (28), (29) ・ ・ PWM
Comparator, (30) ・ ・ Line current pulse conversion circuit, (31)
..Control signal output circuit, (32) load, (33) delay circuit, (34A) DC reactor, (34B) additional DC reactor

Claims (5)

[Claims] A filter circuit connected to an AC power supply;
An AC-DC converter comprising: a switching circuit connected to the filter circuit; a rectifying element for reflux connected between output terminals of the switching circuit; and a smoothing capacitor connected to the rectifying element for reflux via a DC reactor. In the DC converter, an additional switching circuit having the same configuration as the switching circuit and an additional DC reactor having the same configuration as the DC reactor are connected, and the additional switching circuit is connected in parallel with the switching circuit and the DC reactor. A switching circuit and the additional DC reactor are connected between the filter circuit and the smoothing capacitor, and the switching circuit and the additional switching are switched according to a level of a current flowing through the DC reactor and the additional DC reactor. By controlling the circuit on / off, An AC-DC converter for controlling an AC input current flowing from the AC power supply through the filter circuit to the switching circuit and the additional switching circuit in a sine wave shape, and extracting a constant-voltage DC output from the smoothing capacitor. . 2. The switching circuit and the additional switching circuit each include a plurality of pairs of switching elements connected in a bridge, and a backflow prevention rectifying element connected in series with each of the plurality of pairs of switching elements. Item 7. The AC-DC converter according to Item 1. 3. The switching circuit and the additional switching circuit according to at least one of a voltage of the AC power supply and a voltage of the smoothing capacitor in addition to a level of a current flowing through the DC reactor and the additional DC reactor. The AC-DC converter according to claim 1, wherein the AC-DC converter performs on / off control. 4. A current flowing through the DC reactor and the plurality of additional DC reactors, wherein the plurality of additional switching circuits and the plurality of additional DC reactors are connected between the filter circuit and the smoothing capacitor. The on / off control of the switching circuit and the plurality of additional switching circuits according to the level of the AC current flowing from the AC power supply to the switching circuit and the plurality of additional switching circuits via the filter circuit. The AC-control according to any one of claims 1 to 3, wherein the input current is controlled in a sine wave shape, and a DC output of a constant voltage is taken out from the smoothing capacitor.
DC converter. 5. The switching circuit and the additional switching circuit by shifting a switching phase by an angle corresponding to a reciprocal multiple of the number of stages of the switching circuit and the additional switching circuit with respect to one switching cycle of the switching circuit. The AC-DC converter according to any one of claims 1 to 4, wherein on / off control of the AC-DC converter is performed.