JP3367100B2 - AC-DC converter - Google Patents

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 that controls an AC input current in a sinusoidal manner to improve an input power factor, and in particular, an AC-DC converter capable of simplifying a control circuit and achieving high efficiency and low noise. Belongs to DC converter.

[0002]

2. Description of the Related Art A capacitor input type rectifying circuit including a rectifying diode and a smoothing capacitor is generally used in an input power source such as a switching regulator. However, in the capacitor input type rectifier circuit, the charging current flows to the smoothing capacitor only near the maximum value of the sinusoidal AC input current, so the conduction angle of the input current waveform is narrow and the input power factor is low at around 0.6. was there. Therefore, for example, as shown in FIG. 7, a step-down AC-DC converter has been proposed which controls an AC input current in a sine wave shape to improve the input power factor. The AC-DC converter shown in FIG. 7 has a filter circuit (2) having a reactor and a capacitor and connected to a three-phase AC power source (1), and three pairs of switching elements bridge-connected (bridge-connected). 1st to 6th
Power conversion IGBT (insulated gate bipolar transistor) (4,5; 6,7; 8,9) and first to sixth power conversion I
First to sixth backflow preventing diodes (10 to 1) as backflow preventing rectifying elements connected in series with each of the GBTs (4 to 9)
A switching circuit (3) having 5) and connected to the output terminal of the filter circuit (2), and a freewheeling diode (16) as a freewheeling rectifying element connected between the output terminals of the switching circuit (3). And the DC diode (1
Smoothing capacitor (18) connected via (7), current detector (19) that detects current I _L flowing in DC reactor (17) as voltage V _L corresponding to the current, and three-phase AC power supply ( 1)
Input voltage V _U , V _V , V _W of U-phase, V-phase and W-phase from
For detecting the phase voltage (20), the detection voltages V _U , V _V , V _{W of} the phase voltage detecting transformer (20) and the current detector (1
9) Detection voltage V _{L and} smoothing capacitor (18) voltage V _DC
The first to the sixth gate terminals of the first to sixth power conversion IGBTs (4 to 9) in the switching circuit (3) are
Sixth on-off control signal _{V G1, V G 2; V} G3, V G4; V G5,
First to sixth power conversion IGBTs (4 to 9) by applying V _G6
And a control circuit (21) for controlling ON / OFF.

The control circuit (21) generates a reference voltage V _RD which defines a reference value of the DC output voltage V _DC output from both ends of the smoothing capacitor (18) as shown in FIG.
A first error amplifier (23) for comparing the voltage V _DC of the smoothing capacitor (18) with the reference voltage V _RD of the reference power source (22) and outputting an error voltage signal V _E1 thereof; and a current detector ( A second error amplifier (24) for comparing the detection voltage V _L of 19) with the output signal V _E1 of the first error amplifier (23) and outputting those error voltage signals V _E2 , and a phase voltage detection transformer. (20) Detection voltage V _U , V
_{Based on V} , V _W and the output signal V _E2 of the second error amplifier (24), the U-phase, V-phase and W-phase current reference signals V _RUV , V _RVW , V
A phase current reference signal generation circuit (25) that generates _RWU and a triangular wave oscillation that generates a triangular wave signal V _T with a frequency (1 to 100 kHz) sufficiently higher than the frequency (50 to 60 Hz) of the three-phase AC power supply (1). U of circuit (26) and phase current reference signal generation circuit (25)
PWM reference signals V _PUV , V _PVW , V of the current of each phase by comparing the current reference signals V _RUV , V _RVW , V _RWU of the V, V and W phases with the triangular wave signal V _T of the triangular wave oscillating circuit (26). P that outputs _PWU
WM comparator (27, 28, 29) and each PWM comparator
The PWM modulation signals V _PUV , V _PVW , and V _PWU of (27, 28, 29) are ternary line current pulse signals V _SU (= V _PUV −V _PWU ) of “1”, “0”, or “−1”. , V _SV (= V _PVW −V _PUV ), V _SW (=
Line current pulse conversion comparator (30, 31, 32) for converting into V _PWU −V _PVW ) and each line current pulse signal V _SU , V _SV , V _SW
, A code discriminating circuit (33, 34, 35) for discriminating "1", "0" or "-1" and outputting a high (H) level, zero level or low (L) level voltage signal, respectively. ), And the first to sixth power conversion IGBTs (4,
5; 6,7; 8,9 first to sixth on-off control signal V _G1 to be given to the gate terminals _{of), V G2; V G3,} V G4; V G5, the V _G6 code discriminating circuit ( 33,34,35) U based on the voltage signal level
The phase, V-phase, and W-phase arms are configured to include a classification circuit (36, 37, 38) for separately outputting the positive side and the negative side, respectively.

The classification circuit (36, 37, 38) is a code discrimination circuit (33, 37).
When the output signal of 34, 35) is at a high level, the first, third or fifth power conversion IGBT (4, 6,
8) 1st, 3rd or 5th ON to be applied to the gate terminal
Only the OFF control signals V _G1 , V _G3 , and V _G5 are set to the high level to turn on the first, third, or fifth power conversion IGBT (4, 6, 8). Further, when the output signal of the sign discriminating circuit (33, 34, 35) is at a low level, the negative side second, fourth or sixth power conversion IGBT (5, 7, 9) of the corresponding arm. Second, fourth, or sixth on / off control signal V applied to the gate terminal
Only _G2 , V _G4 , and V _G6 are set to the high level, and the second, fourth, or sixth
The power conversion IGBTs (5, 7, 9) are turned on. Further, when the output signal of the sign discriminating circuit (33, 34, 35) is at the zero level, the positive and negative first and second sides of the corresponding arm are
Power conversion IGBTs (4,5), third and fourth power conversion IGBTs (6, 7) or fifth and sixth power conversion IGBTs
The first and second, third and fourth or fifth and sixth on / off control signals V _G1 and V _G given to the gate terminal of T (8,9)
_G2 ; V _G3 , V _G4 ; V _G5 , V _G6 to low level
Power conversion IGBTs (4,5), third and fourth power conversion IGBTs (6, 7) or fifth and sixth power conversion IGBTs
Turn off T (8,9).

The operation of the AC-DC converter shown in FIG. 7 is as follows. For example, as shown in FIG. 9 (A), when the U-phase AC input current I _U of the three-phase AC power supply (1) is for a positive half cycle, the detection voltage V _{L of the} current detector (19) and the phase voltage detection The first on / off control signal V _G1 PWM-modulated according to the detection voltages V _U , V _V , V _{W of the} transformer (20) and the voltage V _DC of the smoothing capacitor (18) is in the control circuit (21). Sorting circuit (36)
To the first IGB for power conversion in the switching circuit (3)
Input to the gate terminal of T (4), and the first IG for power conversion
The BT (4) is turned on / off. At the same time, the second on / off control signal V _G2 input to the gate terminal of the second power conversion IGBT (5) from the classification circuit (36) becomes low level constant, and the second power conversion IGBT is turned on. (5) is turned off. When the U-phase AC input current I _{U of} the three-phase AC power supply (1) is in a negative half cycle, the detection voltage V _L of the current detector (19) and the detection voltage of the phase voltage detection transformer (20) are detected. V _U ,
The second on / off control signal V _G2 PWM-modulated according to V _V , V _{W and} the voltage V _DC of the smoothing capacitor (18) is output from the classification circuit (36) in the control circuit (21) to the switching circuit (3 ) Is input to the gate terminal of the second power conversion IGBT (5), and the second power conversion IGBT (5) is turned on and off. At the same time, the first ON / OFF input from the classification circuit (36) to the gate terminal of the first power conversion IGBT (4).
The off control signal V _G1 becomes low level and constant, and the first power conversion IGBT (4) is turned off. As a result, the current I _U0 input to the U-phase arm of the switching circuit (3) has a positive / negative pulse current waveform with a _peak value I _U0P as shown in FIG. 9 (B). The positive and negative pulsed 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 sine wave current having only a fundamental wave component. The operations similar to those described above are performed for the V-phase arm and the W-phase arm.

U-phase and V supplied from the three-phase AC power supply (1)
FIG. 10 shows waveforms of AC input voltages V _U , V _V , and V _W of phase W and phase _W.
(A) and the minute periods T ₁ , T ₂ , T ₃ , T shown in FIG.
Shows the switching waveform S ₁ to S ₆ of the first to sixth power conversion IGBT of (4-9) at ₄ in FIGS 10 (B) ~ (G). That is, in the minute period T ₁ shown in FIG.
The polarities of the V-phase and W-phase AC input voltages V _U , V _V , and V _W are V _U >
Since 0> V _W > V _V and the magnitude relationship of the absolute value levels of the respective voltages V _U , V _V , V _W is V _U > V _V > V _W, they are shown in FIGS. 10 (B) and (E). Thus, the first power conversion IGBT (4) on the positive side of the U-phase arm and the fourth power conversion IGBT (7) on the negative side of the V-phase arm are turned on. After that, during the ON period of the first power conversion IGBT (4), the fourth power conversion I
When the GBT (7) is turned off, the sixth power conversion IGBT (9) on the negative side of the W-phase arm is turned on as shown in FIG. 10 (G). Then, the minute period T shown in FIG.
₂ , the U-phase, V-phase, and W-phase AC input voltages V _U , V _V , V _W
Has a polarity of V _U >0> V _V > V _W , and the absolute value levels of the voltages V _U , V _V , and V _W are V _U > V _W > V _V.
As shown in FIGS. 10 (B) and 10 (G), the first power conversion IGBT (4) on the positive side of the U-phase arm and the sixth power conversion IGBT (9) on the negative side of the W-phase arm are turned on. It becomes a state. After that, during the ON period of the first power conversion IGBT (4), the sixth
When the power conversion IGBT (9) of FIG.
As shown in (E), the fourth power conversion IGBT (7) on the negative side of the V-phase arm is turned on. Further, the fine period T ₃ shown in FIG. 10 (A), and the U-phase AC input voltage of the V-phase and W-phase V _U, V _V, the polarity of V _W is _V V>0> V _U> V _W The magnitude relationship between the absolute value levels of the voltages V _U , V _V , and V _W is V _V > V _W > V _U
Therefore, as shown in FIGS. 10D and 10G, the third power conversion IGBT (6) on the positive side of the V phase arm and the sixth power conversion IGBT (on the negative side of the W phase arm) 9) is turned on. Thereafter, when the sixth power conversion IGBT (9) is turned off during the on period of the third power conversion IGBT (6), as shown in FIG. The second power conversion IGBT (5) is turned on. Furthermore, FIG.
In the minute period T ₄ shown in 0 (A), the polarities of the U-phase, V-phase, and W-phase AC input voltages V _U , V _V , and V _W are V _V > V _W >0> V _U and each voltage V The magnitude relationship between the absolute value levels of _U , V _V , and V _W is V _U
Since> V _V > V _W , the second power conversion IGBT (5) on the negative side of the U-phase arm and the third side on the positive side of the V-phase arm as shown in FIGS. 10 (C) and (D). The power conversion IGBT (6) is turned on. Then, the second power conversion IGBT
When the third power conversion IGBT (6) is turned off during the on period of (5), the fifth power conversion IGBT (8) on the positive side of the W-phase arm is shown in FIG. 10 (F). Turns on.

Here, the first power conversion IGBT (4) on the positive side of the U-phase arm and the fourth power conversion IGBT (7) on the negative side of the V-phase arm of the switching circuit (3) are in the ON state. When, the U-phase output of the three-phase AC power supply (1), the filter circuit (2),
First backflow prevention diode (10), first power conversion I
GBT (4), DC reactor (17), smoothing capacitor (18)
And a load (39), a fourth power conversion IGBT (7), a fourth
Current flows through the reverse current prevention diode (13), the filter circuit (2), the V-phase output path of the three-phase AC power supply (1), energy is accumulated in the DC reactor (17), and the smoothing capacitor (18) is also stored. Is charged. After that, when the first power conversion IGBT (4) on the positive side 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. Current flows through the path of the DC reactor (17), the smoothing capacitor (18), the load (39), and the free wheeling diode (16). In addition, the negative side second power conversion IG of the U-phase arm of the switching circuit (3)
BT (5) and third IG for power conversion on the positive side of the V-phase arm
When the BT (6) is on, the V-phase output of the three-phase AC power supply (1), the filter circuit (2), and the third backflow prevention diode (1
2), the third power conversion IGBT (6), the DC reactor (1
7), smoothing capacitor (18) and load (39), second power conversion IGBT (5), second backflow prevention diode (11),
Current flows through the U-phase output path of the filter circuit (2) and the three-phase AC power supply (1), energy is accumulated in the DC reactor (17), and the smoothing capacitor (18) is charged. After that, when the second power conversion IGBT (5) on the negative side of the U-phase arm of the switching circuit (3) is turned off, the DC reactor is turned on.
The stored energy of (17) and the electric charge of the smoothing capacitor (18) are released, and a current flows through the path of the DC reactor (17), the smoothing capacitor (18), the load (39), and the free wheeling diode (16). Third and fourth V-phase arms of switching circuit (3)
When the power conversion IGBT (6, 7) and the fifth and sixth power conversion IGBTs (8, 9) of the W-phase arm are turned on / off, or when the switching circuit (3) is connected to the U-phase arm 1
Also, when the second power conversion IGBTs (4,5) and the fifth and sixth power conversion IGBTs (8, 9) of the W-phase arm are turned on / off, substantially the same operation is performed. As described above, the DC current I _L having a constant level as shown in FIG. 9C flows through the DC reactor (17), and the smoothing capacitor (18)
A DC output voltage V _DC is generated at both ends of the.

First to sixth powers of the switching circuit (3)
Smoothing control is performed by turning on / off the conversion IGBTs (4 to 9).
DC output voltage V output from both ends of capacitor (18)_DCIs
In the first error amplifier (23) in the control circuit (21), the reference power source (2
2) Reference voltage V_RDDC output voltage V_DCAnd base
Sub-voltage V_RDError voltage signal V_E1Is the first error amplifier (23)
Is output from. Error voltage signal of the first error amplifier (23)
V_E1Is a current detector (19) in the second error amplifier (24).
Detection voltage V of DC reactor (17) detected by_LWhen
Compared, the error voltage signal V_E1And the detection voltage V_LError of
Pressure signal V_E2Is output from the second error amplifier (24). First
Error voltage signal V of the error amplifier (24) of 2_E2Is the phase voltage detection
Voltage (V) for transformer (20)_U, V_V, V_WWith phase current base
Input to the quasi-signal generating circuit (25) and detect voltage V_U, V_V, V_W
And the error voltage signal V_E2Phase current reference signal generation based on
Path (25) to U phase, V phase and W phase as shown in FIG. 11 (A)
Current reference signal V_RUV, V_RVW, V_RWUIs output. Aiden
Flow reference signal generator (25) U-phase, V-phase and W-phase current source
Quasi signal V_RUV, V_RVW, V_RWUIs the PWM comparator (2
7, 28, 29), the triangular wave signal V of the triangular wave oscillator (26)_T
And the current reference signal V_RUV, V_RVW, V_RWU
And triangular wave signal V_TRelationship with V_RUV, V_RVW, V_RWU<V_Tof
Sometimes it goes low and V_RUV, V_RVW, V_RWU> V_TWhen
11B, 11C and 11D, which are at a high level,
WM modulated signal V_PUV, V_PVW, V_PWUEach PWM comparator
It is output from the data (27,28,29). Each PWM comparator (2
7,28,29) PWM modulation signal V_PUV, V_PVW, V_PWUIs it
Each line current pulse conversion comparator (30, 31, 32)
Line current pulse as shown in Fig. 11 (E), (F), and (G) respectively
Signal V_PUV-V_PWU= V_SU; V_PVW-V_PUV= V_SV; V_PWU
-V_PVW= V_SWIs converted to. For each line current pulse conversion
Line current pulse signal V of the comparator (30, 31, 32)_SU, V_SV, V
_SWAre those values in the code discrimination circuit (33, 34, 35), that is,
"1", "0" or "-1" is discriminated and the code discrimination circuit
(33,34,35) High level, zero level depending on each value
A bell or low level voltage signal is output. Sign discrimination times
Each voltage signal output from the line (33, 34, 35) is
37, 38) respectively, based on the level of each voltage signal.
On the positive and negative sides of the U-phase, V-phase and W-phase arms respectively.
Sorted first and second, third and fourth and fifth and
Sixth on / off control signal V_G1, V_G2; V_G3, V_G4; V_G5,
V_G6From each classification circuit (36,37,38) to switching circuit (3)
The first and second, third and fourth and fifth and sixth electrodes of
For the gate terminals of the force conversion IGBTs (4,5; 6,7; 8,9)
Be granted.

As described above, the current I _L flowing through the DC reactor (17), the U-phase, V-phase and W-phase AC input voltages V _U , V _V , V _{W of the} three-phase AC power supply (1) and the smoothing capacitor (18 first to sixth power conversion IGBT (4 to 9) the control circuit of the switching circuit (3) in accordance to the DC output voltage V _DC across the) (2
ON / OFF control by 1), U phase, V of switching circuit (3) from three-phase AC power supply (1) through filter circuit (2)
AC input currents I _U0 , I _V0 , I _W0 flowing in the W-phase and W-phase arms
Is controlled to have a sine wave shape, and the DC output voltage V _DC output from both ends of the smoothing capacitor (18) is maintained at a constant level.

In the AC-DC converter shown in FIG. 7, an AC input current I flowing from the three-phase AC power source (1) through the filter circuit (2) to the U-phase, V-phase and W-phase arms of the switching circuit (3). DC output voltage V output from both ends of the smoothing capacitor (18) while _U0 , I _V0 and I _W0 are controlled in a sine wave _{shape
Since DC} is maintained at a constant level, the input power factor is approximately 1.0.
The DC output voltage V _{DC that} is highly stable and stable can be obtained.

[0011]

By the way, in the AC-DC converter shown in FIG. 7, the power conversion IGBT (4, 6, 8; on the positive or negative side of each phase arm of the switching circuit (3)).
When any one of 5,7,9) is in the ON state, the power conversion IGBT (5, 7,
9; 4, 6, 8) to turn off one of the
(33, 34, 35) and the sorting circuit (36, 37, 38) are required, and there is a drawback that the configuration of the control circuit (21) becomes complicated. The power conversion IGBT (4,6) is turned on or off when the positive or negative power conversion IGBT (4,6,8; 5,7,9) of each phase arm of the switching circuit (3) is turned on or off. Since the voltage between the collector and emitter terminals of (8,5; 7,9) does not become 0 V, there is a drawback that switching loss occurs, conversion efficiency is lowered, and noise is generated.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an AC-DC converter which can simplify a control circuit and can achieve high efficiency and low noise.

[0013]

AC-DC according to the present invention
The converter includes a switching circuit (3) connected to the AC power supply (1) and a DC reactor (17) in the switching circuit (3).
And a smoothing capacitor (18) connected via the smoothing capacitor (18), and a DC output is taken out from the smoothing capacitor (18). The switching circuit (3) consists of multiple pairs of switching elements connected in a bridge.
(4,5; 6,7; 8,9) and multiple pairs of switching elements (4,5; 6,7;
Backflow prevention rectifiers (10, 9) connected in series with each
~ 15) and. Connect a free-wheeling rectifier (16) between the switching circuit (3) and the smoothing capacitor (18), and connect between the main terminals of multiple pairs of switching elements (4,5; 6,7; 8,9). A zero voltage circuit (49) for switching the voltage to a low level is a switching circuit.
It is connected between (3) and the return rectifying element (16). Controls two switching elements (4,5; 6,7; 8,9) facing each other of a plurality of pairs of switching elements (4,5; 6,7; 8,9) at the same time and controls the zero voltage circuit. (49) sets the voltage between both main terminals of the switching elements (4,5; 6,7; 8,9) of multiple pairs to a low level, and then switches the switching elements (4,5; 6,7; 8 of multiple pairs). , 9) is turned on to control the switching circuit from the AC power supply (1).
Controls the AC input current (I _U0 , I _V0 , I _W0 ) flowing in (3) in a sine wave shape and outputs a constant voltage DC from the smoothing capacitor (18).
Take out (V _DC ). Negative side switching element of each pair (5, 7,
The backflow prevention rectifiers (10 to 15) connected in series with 9) prevent the backflow of the AC input current (I _U , I _V , I _W ) from the AC power supply (1). Negative side switching element (5, 7,
No reverse current flows in 9). Therefore, the positive side switching element (4, 6, 8) and the negative side switching element (5, 7,
9) can be turned on / off at the same time for each pair, so a separate circuit (36, 37, 38) for separating the control signal into positive and negative sides is not required, and the control terminals of each switching element (4 to 9) The number of ON / OFF control signals (V _{G1 to} V _G6 ) applied to
The configuration of (21) can be simplified. Along with this, AC power supply (1)
AC current (I _U0 , I
_V0 , I _W0 ) can be controlled in a sinusoidal manner to increase the input power factor to approximately 1.0 and a constant voltage DC output from the smoothing capacitor (18).
(V _DC ) can be taken out. When the switching elements (4, 6, 8) of the switching circuit (3) are turned off, the stored energy of the DC reactor (17) and the charge of the smoothing capacitor (18) are released, and the DC reactor (17) and the smoothing capacitor are discharged.
Current can flow through the paths of (18), the load (39), and the return rectifying element (16).

After the voltage between both main terminals of the plural pairs of switching elements (4,5; 6,7; 8,9) is set to a low level by the zero voltage circuit (49), the plural pairs of switching elements (4,5 By turning on (6,7; 8,9), each switching element (4
Since the zero voltage switching (ZVS) is performed when (9 to 9) is turned on, it is possible to reduce the switching loss of each switching element (4 to 9) to achieve high efficiency and low noise.

Further, a plurality of pairs of switching elements (4,5; 6,
7; 8,9) are all turned on at the same time, AC power supply
Only one of the backflow preventing rectifiers (10 to 15) to which the highest voltage is applied from (1) becomes conductive, and the other backflow preventing rectifiers (10 to 15) becomes non-conductive. For this reason, one switching element with a high applied voltage from the AC power supply (1)
Current flows from (4 to 9) and one switching element (4 to 9)
The other switching element with low applied voltage after turning off
If the ON state of (4 to 9) is maintained, the current supplied from the AC power supply (1) will cause the switching element (4 to
Commute to 9) naturally. Therefore, each line current pulse signal
(V _SU , V _SV , V _SW ) code discrimination circuit (33,34,3
Since 5) becomes unnecessary, the configuration of the control circuit (21) can be further simplified.

Further, after the voltage between both main terminals of the plural pairs of switching elements (4,5; 6,7; 8,9) is set to a low level by the zero voltage circuit (49), the plural pairs of switching elements ( 4,5; 6,7;
When switching any one of the pair (8, 9) to the ON state with a delay, a switching element (4 to 9) to which a high voltage is applied from the AC power supply (1) and a switching element (4 to 9) to which a low voltage is applied. 4-9), the switching element (4-9) with a low applied voltage is delayed by the ON period of the switching element (4-9) with a high applied voltage to switch to the ON state. The current supplied from the power source (1) can be surely commutated to the switching elements (4 to 9) having a high applied voltage.

Further, a switching circuit (3) of a number corresponding to the number of phases of the AC power supply (1), a DC reactor (17) of the same number as the switching circuit (3), a filter circuit (2) and a smoothing capacitor (18). When connected in parallel with the AC power supply (1), the number of switching circuits (3) corresponding to the number of phases of the AC power supply (1) is set to a single-phase bridge configuration, and the switching circuit (3) is connected to the phase of the AC power supply (1). Since it can be turned on and off for each, switching circuit (3)
Also, the structure of the control circuit (21) can be simplified, and a large capacity DC output can be obtained. Control circuit (21) for simultaneously turning on / off two opposing switching elements (4,5; 6,7; 8,9) of a plurality of pairs of switching elements (4,5; 6,7; 8,9) Is an absolute value detection circuit (40,41,42) that generates output signals to a plurality of pairs of switching elements (4,5; 6,7; 8,9), and an absolute value detection circuit (40,41,42) A line current pulse conversion comparator (30, 31, 32) for applying an output to the current reference signal (V _RUV ,
And a phase current reference signal generation circuit (25) for generating V _RVW , V _RWU ) and _applying it to the line current pulse conversion comparators (30, 31, 32).

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of an AC-DC converter according to the present invention will be described below with reference to FIGS. However, in these drawings, the substantially same parts as those shown in FIGS. 7 to 11 are designated by the same reference numerals, and the description thereof will be omitted. As shown in FIGS. 1 and 2, the AC-DC converter of the present embodiment is the conventional AC-DC converter shown in FIG.
Sign discriminating circuit (33, 34, 35) in converter control circuit (21)
And the sorting circuit (36, 37, 38) is replaced with the absolute value detection circuit (40, 41, 42), and switching is performed by the output signal V _A1 , V _A2 , V _A3 of each absolute value detection circuit (40, 41, 42). The first and second power conversion IGBTs (4,5), the third and fourth power conversion IGBTs (6, 7) and the fifth and sixth power conversion IGBTs (6, 7) facing each other in the circuit (3) The feature is that ON / OFF control is performed simultaneously for each pair of (8, 9). That is, each absolute value detection circuit (40, 4
1, 42) output signals V _A1 , V _A2 , V _A3 are respectively applied to the first and second power conversion IGBTs (4, 4) in the switching circuit (3).
5), the third and fourth power conversion IGBTs (6, 7) and the fifth and sixth power conversion IGBTs (8, 9) are applied to the respective gate terminals as ON / OFF control signals. Further, as shown in FIG. 1, first to sixth power conversion IGBTs are used.
The first to sixth snubber capacitors (43 to 48) are connected between the collector and emitter terminals of T (4 to 9), respectively, and between the switching circuit (3) and the free wheeling diode (16). A zero voltage circuit (49) is provided. Zero Voltage Circuit (49)
Consists of 8 diodes (50-57) and 2 primary windings (58
a, 58b) and a transformer (58) having a secondary winding (58c), and 2
Two commutation IGBTs (59, 60) and a resonance capacitor (61)
And a commutation control circuit (62). The two commutation IGBTs (59, 60) are turned on by the commutation control circuit (62).
The free wheeling diode (16) is controlled to be turned off, and the zero voltage circuit (49) is operated immediately before turning on the first to sixth power conversion IGBTs (4 to 9) in the switching circuit (3).
The voltage across both ends of the DC link voltage, that is, the DC link voltage V _DL becomes approximately 0V. The other circuit configuration is the conventional AC-DC shown in FIG.
It is almost the same as the converter.

Next, the operation of the AC-DC converter shown in FIG. 1 will be described. Waveforms of U-phase, V-phase, and W-phase AC input voltages V _U , V _V , and V _W supplied from the three-phase AC power supply (1) are shown in FIG. Period T ₁ , T ₂ ,
First to sixth power conversion IGBs shown in FIG. 1 at T ₃ and T ₄ .
The switching waveforms S _{1 to} S ₆ of T (4 to 9) are shown in FIG.
It shows in (B)-(G). As shown in FIG. 3A, the minute period T
U phase at _1, V-phase and W-phase of the AC input voltage V _U, V _V, the AC input voltage V _U of V _W, V _V, the magnitude relation between the absolute value level of _{V W V U> V V>} V _Since it is _W , as shown in FIGS. 3 (B) and (C) and FIGS. 3 (D) and (E), the first and second U-phase arms are
The power conversion IGBTs (4,5) and the third and fourth power conversion IGBTs (6, 7) of the V-phase arm are simultaneously turned on. After that, the first and second power conversion IGs
Third and fourth power conversion I during the on period of BT (4,5)
When the GBT (6,7) is turned off at the same time, FIG. 3 (F) and
As shown in (G), the fifth and sixth power conversion IGBTs (8, 9) of the W-phase arm are simultaneously turned on. Then, U-phase in a minute period T ₂ shown in FIG. 3 (A), V-phase and W-phase of the AC input voltage _{V U,} V V, the magnitude relationship of the absolute value level of V _W is V _U
> V _W > V _V , so that FIG. 3 (B) and (C) and FIG.
As shown in (F) and (G), the first and second power conversion IGBTs (4,5) of the U-phase arm and the fifth and sixth power conversion IGBTs (8, 9) of the W-phase arm. Are turned on at the same time. Thereafter, the first and second power conversion IGBs
The fifth and sixth power conversion IGs during the ON period of T (4,5)
When BT (8,9) is turned off at the same time, the data shown in FIG.
As shown in (E), the third and fourth power conversion IGBTs (7) of the V-phase arm are simultaneously turned on. Also, FIG.
The magnitude relationship between the absolute value levels of the U-phase, V-phase, and W-phase AC input voltages V _U , V _V , and V _{W in} the minute period T ₃ shown in (A) is V _V >.
Since V _W > V _U , FIG. 3 (D) and (E) and FIG. 3 (F)
And (G), the third and fourth power conversion IGBTs (6, 7) of the V-phase arm and the fifth and sixth of the W-phase arm.
The power conversion IGBTs (8, 9) are simultaneously turned on. Then, the third and fourth power conversion IGBTs
5th and 6th power conversion IGB during the ON period of (6, 7)
When T (8,9) is turned off at the same time, the signals shown in FIGS.
As shown in FIG. 1, the first and second power conversion I of the U-phase arm
GBT (4,5) is turned on at the same time. Furthermore, FIG. 3 (A)
U-phase in a minute period T ₄ shown in, V-phase and W-phase of the AC input voltage V _U, V _V, the magnitude relation between the absolute value level of V _W V _U> V _V
> V _W , therefore, as shown in FIGS. 3 (B) and (C) and FIGS. 3 (D) and (E), the first and second power conversion IGBTs (4,5) of the U-phase arm and The third and fourth power conversion IGBTs (6, 7) of the V-phase arm are simultaneously turned on. After that, the first and second power conversion IGBTs (4,
Third and fourth power conversion IGBTs during the ON period of 5)
When (6, 7) are turned off at the same time, as shown in FIGS. 3 (F) and (G), the fifth and sixth power conversion IGs of the W-phase arm
BT (8,9) is turned on at the same time.

In the minute period T ₁ shown in FIG. 3 (A), the first and second power conversion IGBTs (4,5) of the U-phase arm and the third and third V-phase arm of the switching circuit (3). Four
When the power conversion IGBTs (6, 7) are turned on, the relationship between the absolute value levels of the U-phase, V-phase, and W-phase voltages V _U , V _V , and V _W of the three-phase AC power supply (1) is V. because it is _{U> V V> V W,} U -phase output of the three-phase AC power source (1), the filter circuit (2), the first backflow prevention diode (10), the first power conversion IGBT (4) ,
DC reactor (17), smoothing capacitor (18) and load (3
9), the fourth power conversion IGBT (7), the fourth backflow prevention diode (13), the filter circuit (2), the current flows through the V-phase output path of the three-phase AC power supply (1), and the DC Energy is accumulated in the reactor (17) and the smoothing capacitor (18) is charged. At this time, the current flowing from the U-phase output of the three-phase AC power supply (1) through the filter circuit (2) to the negative side of the U-phase arm of the switching circuit (3) is the second reverse current prevention diode (11).
Blocked by. In addition, the U-phase output of the three-phase AC power supply (1) to the filter circuit (2), the first backflow prevention diode (10) of the switching circuit (3), and the first power conversion IGBT.
The current flowing to the positive side of the V-phase arm via (4) is blocked by the third backflow prevention diode (12). Therefore, the second negative side of the U-phase arm in the switching circuit (3)
No reverse current flows in the power conversion IGBT (5) and the third power conversion IGBT (6) on the positive side of the V-phase arm.

First and second power conversion I of the U-phase arm
The 3rd and 4th of the V-phase arm during the ON period of GBT (4,5)
When the power conversion IGBTs (6, 7) are simultaneously turned off, the fifth and sixth power conversion IGBTs of the W-phase arm
(8, 9) are turned on at the same time, the U-phase output of the three-phase AC power supply (1), the filter circuit (2), and the first backflow prevention diode
(10), 1st power conversion IGBT (4), DC reactor
(17), smoothing capacitor (18) and load (39), sixth power conversion IGBT (9), sixth backflow prevention diode (1
5), the filter circuit (2), the current flows through the W-phase output path of the three-phase AC power supply (1). As a result, energy is continuously accumulated in the DC reactor (17) and the smoothing capacitor (1
8) is charged. At this time, from the U-phase output of the three-phase AC power supply (1) to the filter circuit (2), the first backflow prevention diode (10) of the switching circuit (3), and the first power conversion IGBT.
The current flowing to the positive side of the W-phase arm via T (4) is blocked by the fifth backflow prevention diode (14), so that the fifth positive-side current of the W-phase arm in the switching circuit (3) is blocked. A reverse current does not flow in the power conversion IGBT (8).

After that, when all the power conversion IGBTs (4 to 9) of the switching circuit (3) are turned off, the stored energy of the DC reactor (17) and the electric charge of the smoothing capacitor (18) are discharged, and the DC reactor is discharged. (17), smoothing capacitor (1
A current flows through the route of 8), the load (39), and the free wheeling diode (16). Other minute periods T ₂ , T ₃ , T shown in FIG.
_In the case of ₄ , the operation is similar to the above. As a result, a constant level DC current I _L flows through the DC reactor (17), and a DC output voltage V _DC is generated across the smoothing capacitor (18).

The DC output voltage V _DC output from both ends of the smoothing capacitor (18) by the on / off operation of the first to sixth power conversion IGBTs (4 to 9) of the switching circuit (3) is
In the first error amplifier (23) in the control circuit (21), the reference power source (2
Is compared with a reference voltage V _RD 2), the error voltage signal V _E1 of the DC output voltage V _DC and reference voltage V _RD is the first error amplifier (23)
Is output from. The error voltage signal V _E1 of the first error amplifier (23) is supplied to the current detector (19) in the second error amplifier (24).
Is compared with the detected voltage V _L detected DC reactor (17), the error voltage signal V _E2 of the error voltage signal V _E1 and the detection voltage V _L is outputted from the second error amplifier (24). The error voltage signal V _E2 of the second error amplifier (24) is input to the phase current reference signal generation circuit (25) together with the detection voltages V _U , V _V and V _W of the phase voltage detection transformer (20) and detected. Voltage V _U , V _V , V _W
And the phase current reference signal generation circuit (25) outputs current reference signals V _RUV , V _RVW and V _RWU of U phase, V phase and W phase as shown in FIG. 4 (A) based on the error voltage signal V _E2 . To be done. The U-phase, V-phase, and W-phase current reference signals V _RUV , V _RVW , and V _RWU of the phase current reference signal generation circuit (25) are _supplied to the PWM comparators (27, 2).
8, 29) is compared with the triangular wave signal V _T of the triangular wave oscillator circuit 26, respectively, and the relationship between the current reference signals V _RUV , V _RVW , V _RWU and the triangular wave signal V _T is V _RUV , V _RVW , V _RWU < PWM modulation signal V _PUV , as shown in FIGS. _4B , _4C , and _4D , which has a low level when V _T , and has a high level when V _RUV , V _RVW , V _RWU > V _T V _PVW and V _PWU are PWM comparators (27, 2
It is output from (8,29). Each PWM comparator (27, 28, 2
The PWM modulation signals V _PUV , V _PVW , and V _PWU of 9) are respectively obtained by the line current pulse conversion comparators (30, 31, 32) in FIG.
Line current pulse signal V _PUV − as shown in (E), (F) and (G)
V _PWU = V _{S U} ; V _PVW -V _PUV = V _SV ; V _PWU -V _PVW = V
Converted to _SW . Each line current pulse conversion comparator (3
The line current pulse signals V _SU , V _SV and V _SW of (0, 31, 32) are input to the absolute value detection circuits (40, 41, 42), respectively, and are input to the absolute value detection circuits (40, 41, 42) shown in FIGS.
The output signals V _A1 , V _A2 , V _A3 of the absolute value detection circuit (40, 41, 42) as shown in (J) are respectively the first and second IGBTs (4) of the U-phase arm of the switching circuit (3). , 5), the third and fourth IGBTs (6,7) of the V-phase arm and the fifth IGBT of the W-phase arm.
And a gate terminal of the sixth power conversion IGBT (8, 9) for each arm.

The outline of the operation of the zero voltage circuit (49) is as follows. Two commutation control circuits (62) for commutation I
When the control signal V _Z shown in FIG. 5A is applied to each gate terminal of the GBT (59, 60) and the two commutation IGBTs (59, 60) simultaneously change from the off state to the on state, the gate signal shown in FIG. ), The voltages V _CE1 and V _CE2 between the collector and emitter terminals of the two commutation IGBTs (59, 60) drop to 0V. At the same time, the two primary windings (58a, 58b) of the transformer (58) and the first to sixth snubber capacitors (43 to 48) in the switching circuit (3) resonate to cause two commutation IGBTs. A resonance current flows in (59, 60), and the currents I _C1 and I _C2 flowing in each commutation IGBT (59, 60) rise in a sinusoidal shape as shown in FIG. 5 (C). As a result, the first to sixth parts in the switching circuit (3) are
From the snubber capacitors (43,45,47; 44,46,48) of the six diodes (50,50) connected to the positive and negative sides of each phase arm.
52,54; 51,53,55) and two commutation IGBTs (59,60) through the two primary windings (58a, 58b) of the transformer (58), each primary winding Energy is stored in (58a, 58b). At this time, the resonance capacitor (61) is charged to the DC output voltage V _DC with the polarity shown. In the above state, FIG. 5 (A)
When the voltage level of the control signal V _Z of the commutation control circuit (62) is changed from the high (H) level to the low (L) level to turn the two commutation IGBTs (59, 60) from the on state to the off state, Since the energy accumulated in the two primary windings (58a, 58b) of the transformer (58) is released, the two commutation IGBTs (59, 6)
A ringing voltage is generated between the collector and emitter terminals of (0), and the voltages V _CE1 and V _CE2 between the collector and emitter terminals of the two commutation IGBTs (59, 60) rise as shown in FIG. 5 (B). , It converges to a constant value while damping vibration. As a result, a voltage in the positive direction is generated in the secondary winding (58c) of the transformer (58), the resonance capacitor (61) is charged through the diode (56) with the opposite polarity to that shown in the drawing, and the resonance capacitor (61) is charged. The voltage across the capacitor (61) becomes approximately 0V. At this time, the voltage across the free wheeling diode (16), that is, the DC link voltage V _DL is approximately 0 V.
Therefore, the voltage between the collector and emitter terminals of the first to sixth power conversion IGBTs (4 to 9) of the switching circuit (3) becomes approximately 0V. Therefore, within this period, the control circuit
The output signals V _A1 , V _A2 , V _A3 of (21) are changed from low level to high level as shown in FIG. 5 (D), and the first to sixth power conversion IGBTs (4) in the switching circuit (3) are , 5; 6,7; 8,9) from the off state to the on state, the first to sixth power conversion I
Zero voltage switching (ZVS) occurs when the GBTs (4 to 9) are turned on. Further, when the first to sixth power conversion IGBTs (4 to 9) are turned off, the first to sixth snubber capacitors (43 to 48) act as snubbers to operate the first to sixth power conversions. Since the voltage between the collector and emitter terminals of the IGBTs (4 to 9) for use rises gradually from approximately 0V,
Zero voltage switching is performed even when the sixth power conversion IGBT (4 to 9) is turned off.

In the AC-DC converter of the present embodiment, the switching circuit (3) includes the first to sixth power conversion I.
Two power conversion IGs of GBT (4,5; 6,7; 8,9) facing each other
By simultaneously turning on / off the BTs (4,6,8; 5,7,9), the U-phase and V-phase of the switching circuit (3) from the three-phase AC power supply (1) through the filter circuit (2) First to sixth backflow prevention in which the backflows of the AC input currents I _U , I _V , and I _W flowing in the W-phase and W-phase arms are connected in series with the first to sixth power conversion IGBTs (4 to 9) Since it is blocked by the diode (10-15) for
The second, fourth and sixth power conversion I on the negative side of each phase arm
No reverse current flows through GBT (5,7,9). Therefore, the positive side first of each phase arm of the switching circuit (3),
The third and fifth power conversion IGBTs (4,6,8) and the negative second, fourth and sixth power conversion IGBTs (5,7,9) are simultaneously turned on / off for each pair. Since it can be controlled, the classification circuit (36, 37, 38) shown in FIG. 8 is unnecessary, and the on / off control signal V _G1 given to each gate terminal of the first to sixth power conversion IGBTs (4 to 9) is eliminated. It is possible to simplify the configuration of the control circuit (21) by halving the number of V _G6 . Along with this, the switching circuit from the three-phase AC power supply (1) through the filter circuit (2).
AC input current I _U0 , I _V0 , I _W0 flowing in each phase arm of (3)
Can be controlled in a sinusoidal manner to increase the input power factor to approximately 1.0, and a smooth DC output voltage V from the smoothing capacitor (18).
_DC can be taken out. Also a switching circuit
By the zero voltage circuit (49) provided on the output side of (3),
6th power conversion IGBT (4,5; 6,7; 8,9) collector
By switching the first to sixth power conversion IGBTs (4,5; 6,7; 8,9) to the ON state after the voltage between the emitter terminals has dropped to approximately 0 V, each power conversion IGBT (4 9-9), the zero voltage switching is performed, so that the switching loss of each power conversion IGBT (4-9) can be reduced to achieve high efficiency and low noise.

The present embodiment can be modified. For example, instead of the triangular wave oscillating circuit (26) that generates the triangular wave signal V _T in the control circuit (21), the output frequency is the same and proportionally increases linearly from the minimum value to the maximum value, and then from the maximum value. A sawtooth wave oscillation circuit that generates a sawtooth wave signal that sharply drops toward a minimum value is provided, and the first to sixth switching circuits (3) are synchronized with the falling edge of the sawtooth wave signal of the sawtooth wave oscillation circuit.
All the power conversion IGBTs (4,5; 6,7; 8,9) may be switched from the off state to the on state at the same time. That is, in the minute period T ₁ of the U-phase, V-phase, and W-phase AC input voltages V _U , V _V , and V _W of the three-phase AC power supply (1) shown in FIG. First to sixth power conversion IGs in the switching circuit (3) of (G)
As shown in the switching waveforms S _{1 to} S ₆ of BT (4 to 9), when all the power conversion IGBTs (4 to 9) are turned from the off state to the on state at the same time, the U phase in the switching circuit (3) The highest voltage is applied to the anode terminal of the first backflow prevention diode (10) of the arm to make it conductive, and the second to sixth backflow prevention diodes (11 to 15) become non-conductive. . At this time, W in the switching circuit (3)
Since the lowest voltage is applied to the cathode terminal of the sixth backflow prevention diode (15) of the phase arm, as shown in FIG.
A current flows through the first power conversion IGBT (4) and the sixth power conversion IGBT (9) as shown by the hatched portion (G). Therefore, a current flows from the first power conversion IGBT (4) of the U-phase arm having a high applied voltage from the three-phase AC power supply (1), and the first power conversion IGBT (4) is turned off at time t ₁ . If the sixth power conversion IGBT (9) of the W-phase arm having a low applied voltage is kept in the ON state after the state becomes the state, the switching circuit (from the three-phase AC power supply (1) through the filter circuit (2) ( The current supplied to 3) is the first power conversion I of the U-phase arm as shown by the hatched portions in FIGS. 6 (B) and (F).
Fifth IGBT for power conversion from GBT (4) to W-phase arm
Commute to (8) naturally. In the minute period T ₂ shown in FIG. 6 (A), the second power conversion IGBT (5) of the U-phase arm having a high applied voltage from the three-phase AC power supply (1) is also used, as described above.
Current flows from the second IGBT for power conversion at time t ₂ .
If the fifth power conversion IGBT (8) of the W-phase arm having a low applied voltage is held in the ON state after (5) is turned off, the filter circuit (2) is removed from the three-phase AC power supply (1). The current supplied to the switching circuit (3) via the
As indicated by the hatched area in FIG. 5, the power is naturally commutated from the second power conversion IGBT (5) of the U-phase arm to the sixth power conversion IGBT (9) of the W-phase arm. Therefore, the code discriminating circuit (33, 34, 35) shown in FIG. 8 is unnecessary, and the configuration of the control circuit (21) can be further simplified.

Further, in the embodiment shown in FIG. 6, the low voltage is applied to the first and second power conversion IGBTs (4,5) of the U-phase arm to which a high voltage is applied from the three-phase AC power source (1). The fifth and sixth power conversion IGBTs (8,
When the voltage difference with 9) is small, the voltage between collector-emitter terminals of all power conversion IGBTs (4-9) is set to approximately 0V by the zero voltage circuit (49), and then the W-phase with a low applied voltage is applied. The fifth and sixth power conversion IGBTs (8, 9) of the arm are connected to the first and second power conversion IGs of the U-phase arm having a high applied voltage.
By switching to the ON state by delaying the ON period of BT (4,5), the three-phase AC power supply (1) to the filter circuit (2)
To surely commutate the current supplied to the switching circuit (3) from the first power conversion IGBT (4) of the U-phase arm to the fifth power conversion IGBT (8) of the W-phase arm. You can

The embodiment of the present invention is not limited to the above-mentioned embodiments, and various modifications can be made. For example, in the above-described embodiment, a mode in which a power conversion IGBT (insulated gate type bipolar transistor) is used as a switching element forming the switching circuit (3) is shown, but a MOS-FET (MOS type field effect transistor), Junction type bipolar transistor or J-FET
(Junction type field effect transistor) or the like can also be used.
In the above embodiment, the three-phase AC power supply (1) is connected to the switching circuit (3) having a three-phase bridge configuration via the filter circuit (2).
(3) The freewheeling diode (16) and the DC reactor (17) may be connected in parallel between the filter circuit (2) and the smoothing capacitor (18) as one set. In this case, the three switching circuits (3) have a single-phase bridge configuration, and each switching circuit (3) can be turned on / off for each phase of the three-phase AC power supply (1). Also, the structure of the control circuit (21) can be simplified, and a large capacity DC output can be obtained. Further, it can be easily understood that the present invention can be applied not only to the case of the three-phase AC power supply but also to the case of the single-phase AC power supply or the multi-phase AC power supply having three or more phases.

[0029]

According to the present invention, since the positive side switching element and the negative side switching element in the switching circuit are simultaneously turned on / off for each pair, the control sequence of the switching operation of each switching element is simplified. And the configuration of the control circuit can be simplified. If a zero-voltage circuit is provided on the output side of the switching circuit, the zero-voltage circuit reduces the voltage between the main terminals of the multiple pairs of switching elements to a low level and then turns on the multiple pairs of switching elements. By switching, zero voltage switching is performed when each switching element is turned on, so that switching loss of each switching element is reduced and AC-
It is possible to improve the conversion efficiency of the DC converter and suppress the generation of switching noise.

[Brief description of 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 diagram showing the voltage of each phase of the three-phase AC power supply in FIG. 1 and the switching operation of each power conversion IGBT.

FIG. 4 is a time chart showing signals of respective parts of the control circuit of FIG.

5 is a waveform diagram showing the voltage and current of each part of the zero-voltage circuit shown in FIG.

FIG. 6 is a waveform diagram showing a voltage of each phase of a three-phase AC power supply and a switching operation of each power conversion IGBT according to a modified embodiment of the present invention.

FIG. 7 is an electric circuit diagram showing a conventional AC-DC converter.

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

9 is a waveform diagram showing currents in respective parts of the main circuit of the AC-DC converter shown in FIG.

10 is a waveform diagram showing the voltage of each phase of the three-phase AC power supply in FIG. 7 and the switching operation of each power conversion IGBT.

FIG. 11 is a time chart showing signals of respective parts of the control circuit of FIG.

[Explanation of symbols]

(1) ・ ・ Three-phase AC power supply (AC power supply), (2) ・ ・ Filter circuit, (3) ・ ・ Switching circuit, (4-9) ・ ・ First
~ 6th IGBT (switching element), (10 ~ 15)
・ First to sixth backflow prevention diodes (backflow prevention rectifiers), (16) ・ ・ Recirculation diodes (recirculation rectifiers), (17) ・ DC reactors, (18) ・ ・ Smoothing capacitors, (19) ・ ・ Current detector, (20) ・ ・ Phase voltage detection transformer, (21) ・ ・ Control circuit, (22) ・ ・ Reference power supply, (23) ・ ・ First error amplifier, (24) ..Second error amplifier, (25) .. Phase current reference signal generation circuit, (26).
・ Triangular wave oscillation circuit, (27,28,29) ・ ・ PWM comparator, (30,31,32) ・ ・ Line current pulse conversion comparator, (33,34,35) ・ ・ Sign discrimination circuit, (36,37) , 38) ...
Classification circuit, (39) ・ ・ Load, (40,41,42) ・ ・ Absolute value detection circuit, (43〜48) ・ ・ First to sixth snubber capacitors, (49) ・ ・ Zero voltage circuit, (50 to 57) ・ ・ Diode, (58) ・ ・ Transformer, (58a, 58b) ・ ・ Primary winding,
(58c) ・ ・ Secondary winding, (59,60) ・ ・ IGBT for commutation,
(61) ・ ・ Resonant capacitors, (62) ・ ・ Commutation control circuit

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-6-205585 (JP, A) JP-A-8-19261 (JP, A) JP-A-5-83928 (JP, A) Special table 10- 505218 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H02M 7/12 H02M 7/219

Claims (5)

(57) [Claims] 1. An AC-DC converter, comprising: a switching circuit connected to an AC power supply; and a smoothing capacitor connected to the switching circuit via a DC reactor, wherein a DC output is extracted from the smoothing capacitor. Has a plurality of pairs of switching elements connected in a bridge and a backflow preventing rectifier element connected in series with each of the plurality of pairs of switching elements, and is provided between the switching circuit and the smoothing capacitor for return. A rectifying element is connected, and a zero-voltage circuit for setting the voltage between both main terminals of the plurality of pairs of switching elements to a low level is connected between the switching circuit and the return rectifying element, and the plurality of pairs of switching elements. The two switching elements facing each other are simultaneously turned on / off, and the zero voltage circuit causes the switching After the voltage between both main terminals of the pair of switching elements is set to a low level, the plurality of pairs of switching elements are turned on to control an AC input current flowing from the AC power source to the switching circuit in a sine wave shape and smoothed. An AC-DC converter characterized by extracting a constant voltage DC output from a capacitor. 2. The AC-DC converter according to claim 1, wherein all the plurality of pairs of switching elements are turned on at the same time. 3. The zero voltage circuit reduces the voltage between both main terminals of the plurality of pairs of switching elements to a low level, and then the one of the plurality of pairs of switching elements.
3. The A according to claim 1, wherein the pair is turned on with a delay.
C-DC converter. 4. The number of the switching circuits corresponding to the number of phases of the AC power supply, and the same number of the DC reactors as the switching circuits are connected in parallel between the filter circuit and the smoothing capacitor. The AC-DC converter according to any one of 3 above. 5. A control circuit for simultaneously ON / OFF controlling two switching elements facing each other of the plurality of pairs of switching elements, an absolute value detection circuit for generating an output signal to the plurality of pairs of switching elements, and the absolute value detection circuit. 5. A line current pulse conversion comparator for giving an output to a value detection circuit, and a phase current reference signal generation circuit for generating a current reference signal and giving it to the line current pulse conversion comparator. The AC-DC converter according to item 1.