JP3419448B2 - Three-phase 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 a three-phase AC-DC converter having a switching circuit and an insulation transformer for converting three-phase AC power into DC power.

[0002]

2. Description of the Related Art When an insulating rectifier for use in a battery charger or the like is constructed, an insulating transformer is provided on the commercial frequency side, and a rectifying circuit and a PWM switching circuit for voltage adjustment are provided on the secondary side of the transformer. , The transformer gets bigger. In order to solve this problem, P is added to the three-phase AC power supply.
A WM rectifier, that is, an AC-DC converter is connected, a DC link capacitor is connected between the output terminals of this converter, an inverter having a transformer is connected to the output stage of the DC link capacitor, and a rectifying / smoothing circuit is provided at the output stage of the inverter. Sometimes. In this case, since the transformer is a high-frequency transformer with small loss, the size can be reduced.

[0003]

However, the converter,
Since a DC link capacitor, an inverter, a transformer, and a rectifying / smoothing circuit are required, a portion other than the transformer becomes large, and a loss occurs in each circuit, which makes it difficult to improve the overall efficiency.

Therefore, an object of the present invention is to reduce the size of a three-phase AC-DC converter having an insulation transformer and a switching circuit.

[0005]

The present invention for solving the above problems and achieving the above objects includes a first, a second and a third AC input terminal connected to a three-phase AC power supply, and the first and second AC input terminals. A first AC-DC converter connected to the first and second AC input terminals, a second AC-DC converter connected to the second and third AC input terminals, and the first and third
AC third connected to the AC input terminals of - a DC converter, the first, second and third exchanges - a control circuit for a DC converter, the first, second and third exchanges - DC converter Common smoothing capacitor connected to the DC output terminal of
A capacitor and each of the first, second and third AC-DC converters has a primary winding and a secondary winding.
A transformer that, the three-phase to the primary winding of the transformer
An AC Sui <br/> etching circuit for applying intermittently an AC voltage of the AC power source, an insulated converter and a full-wave rectifier circuit for rectifying a voltage of the secondary winding of the transformer, The control circuit controls the AC switching circuit so as to improve the power factor of the 3-phase AC power at the first, second and third AC input terminals. The present invention relates to a DC converter.

As described in claim 2, the first,
First second and third AC input terminals, having a voltage detection circuit for detecting a voltage between the second and third lines, the control circuit, the first, second and third exchanges -It is desirable to have means for selectively suspending one of the DC converters to which the lowest line voltage is input. Further, according to a third aspect of the present invention, the control circuit includes the first and second control circuits.
And a means for shifting the switching timing of the AC switching circuits of the two AC-DC converters operating in the third AC-DC converter. Further, as shown in claim 4, wherein the control circuit, the first, second and third exchanges - DC converter - the data
A first, a second and a third duty ratio command generator for generating first, second and third duty ratio command values indicating the duty ratio of the AC switching circuit; and a first sawtooth wave having a rising slope. Sawtooth wave generating means for selectively generating a second sawtooth wave having a falling slope, the first, second and third duty ratio command values and the first
Or comparing the second sawtooth wave with the first, second and third PW
Forming an M control signal to generate the first, second and third AC-
First, second and third comparators for supplying to the AC switching circuit of the DC converter, and two of the first, second and third AC-DC converters operating within The sawtooth generator for supplying the first sawtooth wave to the comparator for one of the two and the second sawtooth wave to the comparator for the other of the two units. It is desirable to have means for controlling. Further, as shown in claim 5, wherein the control circuit, the first, second and third alternating current -
The first, second, and third duty ratio command value generators that generate the first, second, and third duty ratio command values indicating the duty ratio of the AC switching circuit of the DC converter are in phase with each other. A sawtooth wave generating means for selectively generating first and second sawtooth waves different by 180 degrees, the first, second and third duty ratio command values and the first or second sawtooth wave First by comparison,
First, second and third PWM control signals are formed and supplied to the AC switching circuits of the first, second and third AC-DC converters. And the comparator for one of the two operating in the first, second and third AC-DC converters, the first sawtooth wave being supplied to the comparator. Means for controlling the sawtooth wave generating means to supply the second sawtooth wave to the comparator for the other of the two.

[0007]

According to the inventions of the respective claims, the alternating voltage is interrupted by the alternating- current switching circuit on the primary side of the insulating transformer,
Since the AC-DC conversion can be performed only by rectifying and smoothing the output of the secondary winding, the AC-DC converter has a simple structure as a whole and the efficiency is improved. In addition, each line voltage of the three-phase AC is converted into DC by the first, second, and third AC-DC converters, and the output terminals of these are converted into a common voltage.
Since it is connected to the smoothing capacitor , it is possible to obtain a DC output that compensates for changes in the line voltage, and smoothness is improved. Also, the input power factor can be improved. Further, according to the invention of claim 2, since the converter to which the lowest line voltage among the three-phase line voltages is input is stopped,
It is possible to improve efficiency. That is, a converter with a low input voltage is inefficient, and a converter with a high input voltage is efficient. According to the second aspect of the present invention, since two highly efficient units are selected and operated, the overall efficiency is also increased. Also,
Since it is not necessary for the converter to operate in a region where the input voltage is low, the input voltage range of the converter can be narrowed. According to the invention of claims 3 to 5, the PWM
By shifting the timing of switching by the control signal, smoothness can be improved and power ripples generated when power is supplied to the load can be reduced.

[0008]

Embodiments of the present invention will now be described with reference to the drawings.

[0009]

[First Embodiment] The alternating current of the first embodiment shown in FIG.
The DC converter includes first, second and third AC input terminals 1
r, 1s, 1t, first, second and third converters 2, 3, 4, a common control circuit 5, a common smoothing capacitor 6, a pair of DC output terminals 7a, 7b, and an input. Voltage detection circuit 8, output voltage detection circuit 9, and current detector 1
0, 11, 12 and reactor 1 for removing high frequency components
It consists of 3, 14, and 15.

First, second and third AC input terminals 1r,
1s and 1t are for inputting R-phase, S-phase, and T-phase voltages of three-phase alternating current having a commercial frequency (50 Hz or 60 Hz).

The first, second and third converters 2, 3,
Reference numeral 4 is a PWM insulation type converter having a PWM switching circuit, an insulation transformer, and a rectification circuit, respectively.
The input lines 16 and 17 of the first converter 2 are connected to the first and second AC input terminals 1 via the reactors 13 and 14.
It is connected to r and 1s and converts the first line voltage Vrs between the R phase and the S phase into a DC voltage. The input lines 18 and 19 of the second converter 3 are connected to the second and third AC input terminals 1s and 1t via the reactors 14 and 15, respectively, and the second line between the S phase and the T phase is connected. The inter-voltage Vst is converted into a DC voltage. Input line 2 of third converter 4
0 and 21 are the first and third via the reactors 13 and 15.
Connected to the AC input terminals 1r and 1t of the T phase and R
The third line voltage Vtr between the phases is converted into a DC voltage.
The DC output lines 22, 23 of the first converter 2 and the second
The DC output lines 24 and 25 of the converter and the DC output lines 26 and 27 of the third converter 4 are connected in parallel to each other and to the smoothing capacitor 6. The smoothing capacitor 6 is connected to the pair of DC output terminals 7a and 7b. Electric power is supplied to the load 7 between the output terminals 7a and 7b through the smoothing capacitor 6. Although FIG. 1 shows a pair of DC output terminals 7a and 7b and one load 7, a plurality of DC output terminals can be provided to connect a plurality of loads.

First, second and third AC input terminals 1r,
The input voltage detection circuit 8 connected to 1s and 1t detects the R, S and T phase voltages Vr, Vs and Vt of the three-phase AC voltage,
This is sent to the control circuit 5 on lines 28, 29 and 30. For ease of explanation, the input and output of the input voltage detection circuit 8 are indicated by the same symbols.

The output voltage detection circuit 9 connected to the pair of DC output terminals 7a and 7b detects the output voltage V0 between the output terminals 7a and 7b and sends it to the control circuit 5 through the line 31. For ease of explanation, the input and output of the output voltage detection circuit 9 are indicated by the same symbols.

First, second and third current detectors 10, 1
1, 12 are the first, second and third converters 2, 3, 4
The converter input currents Irs, Ist, and Itr are detected and sent to the control circuit 5 through lines 32, 33, and 34.
Note that the current detectors 10, 11, and
Twelve inputs and outputs are shown with the same symbols.

The control circuit 5 includes three-phase AC input terminals 1r, 1
1st, 2nd so that the power factor in s and 1t approaches 1
And a PWM control signal for controlling a switching circuit included in the third converter 2, 3, 4.
Converters 2, 3, 4 by lines 35, 36, 37
Send to.

FIG. 2 shows the details of the first, second and third converters 2, 3, 4 of FIG. Since the first, second and third converters 2, 3 and 4 have the same circuit configuration,
The same circuit elements are designated by the same reference numerals, and the subscript a,
b, c depending on the first, second and third converters 2,
Distinguish between 3 and 4. Further, the configuration of the first converter 2 will be described, and the description of the second and third converters 3 and 4 will be omitted. The first converter 2 includes an insulating transformer 40a having a primary winding 41a and a secondary winding 42a, and first and second switches 43a and 4a each including a field effect transistor.
4a and the first and second primary side diodes 45a, 46
a and the first and second secondary side diodes 47a and 48a
And an AC capacitor 49a. Primary winding 41a
A series circuit of the first and second switches 43a and 44a is connected between the R-phase input line 16 and the S-phase input line 17. First and second switches 43a, 44a
Are connected in opposite polarities. The first and second primary side diodes 45a and 46a are connected in reverse directional parallel to the first and second switches 43a and 44a. The first and second primary side diodes 45a and 46a may be built-in diodes or parasitic diodes of the first and second switches 43a and 44a formed of FETs. The combination of the first and second switches 43a and 44a and the first and second primary side diodes 45a and 46a constitutes an AC switch circuit, and is composed of an AC positive direction half-wave and a negative direction half-wave. Both can be turned on and off. The AC capacitor 49a is connected between the pair of AC input lines 16 and 17, and includes the first and second switches 43a and 4a.
The high frequency component generated by turning on / off 4a is removed. The secondary winding 42a has a center tap, and the center tap is connected to the DC output line 23 on the negative side. First
The second secondary side diodes 47a and 48a are connected between one end and the other end of the secondary winding 42a and the positive side output line 22. Therefore, the first and second secondary diodes 47a and 48a form a full-wave rectifier circuit.

The first and second switches 43a and 44a are turned on at a frequency sufficiently higher than the frequency of the input AC voltage.
Turn off. First during the positive half-wave of the input AC voltage
When the switch 43a is turned on, the line 16,
A current flows through the path of the primary winding 41a, the first switch 43a, the second primary side diode 46a, and the line 17, and
On the secondary side, the first secondary side diode 47a conducts. When the second switch 44a is turned on during the negative half-wave of the AC voltage, the path of the line 17, the second switch 44a, the first primary side diode 45a, the primary winding 41a, and the line 16 A current flows through the second secondary side diode 48a on the secondary side. The second and third converters 3 and 4 operate similarly to the first converter 2. However, since the input voltages of the first, second and third converters 2, 3, and 4, that is, the first, second and third line voltages Vrs, Vst, Vtr have different phases, the first, second The power supply from the second and third converters 2, 3, 4 changes with time.

FIG. 3 shows the control circuit 5 of FIG. 1 in detail. The control circuit 5 has (1) a function for controlling the output voltage V0 to be constant, (2) a function for controlling the input power factor to 1, (3)
It has a function of selectively driving the first, second, and third converters 2, 3, and 4.

A reference voltage generator 50, a voltage fluctuation detecting subtracter 51, and a current amplitude command calculator 52 are provided for executing the constant voltage control. The subtracter 51 outputs the DC output voltage V0 of the line 31 from the reference voltage V01 of the reference voltage generator 50.
Subtract 0. Based on the output of the subtracter 51, the current amplitude command calculator 52 generates a current amplitude command value I0 for keeping the output voltage V0 constant. The current amplitude command value I0 can also be called an output voltage control command value. In this embodiment, since the DC output voltage is achieved by controlling the current on the AC side, I0 is called the current amplitude command value.

According to the common current amplitude command value I0, the first,
First, second and third multipliers 53, 54, 55 are provided for controlling the second and third converters 2, 3, 4. First, second and third multipliers 53, 5
4, 55 are R, S, and T-phase voltages Vr, which are supplied from lines 28, 29, and 30 and are composed of the sine wave shown in FIG.
By multiplying Vs and Vt by the current amplitude command value I0, FIG.
The first, second and third phase current command values I0r, I0s,
Output I0t. This phase current command value I0r, I0s, I0t
Is a three-phase AC signal corresponding to the target current command value for approximating the AC input current to a sine wave, setting the power factor to 1, and setting the output voltage V0 to the target value.

The computing unit 56 uses the R, S, and T phase current command values I
The first, second and third converter current command values Ia, Ib and Ic corresponding to 0r, I0s and I0t are obtained.
In order to create a flag as a control signal used in the calculator 56, the first, second and third subtractors 57, 5
8, 59 and a comparison calculator 60 are provided. The first subtractor 57 converts the R-phase voltage Vr on the line 28 to the line 29.
Is subtracted from the S-phase voltage Vs to obtain the RS voltage, that is, the first line voltage Vrs. The second subtractor 28 uses S on line 29
Subtract T-phase voltage Vt of line 30 from phase voltage Vs to obtain S
The voltage between T, that is, the second line voltage Vst is obtained. The third subtracter 59 converts the T-phase voltage Vt on the line 30 to the R-phase on the line 28.
The voltage between TRs, that is, the third line voltage V by subtracting the phase voltage Vr
ask for tr. FIG. 4B shows the first, second and third line voltages Vrs, Vst and Vtr.

A comparison calculator 60 as a flag creating means.
Is the first, second and third line voltages Vrs, Vst, V obtained from the first, second and third subtractors 57, 58, 59.
The absolute values of tr are compared with each other, the first flag 1 is generated when the first line voltage Vrs is the lowest, and the second line voltage Vst is generated.
The second flag 2 is generated when is the lowest, and the third flag 3 is generated when the third line voltage Vtr is the lowest. Figure 4
(D) shows a flag obtained from the comparison calculator 60. As is clear from this, t0 to t1 section (0 ° to 60 °)
And the first flag 1 is obtained in the interval t3 to t4 (180 ° to 240 °) and the interval t1 to t2 (60 ° to 12).
0 °) and t4 to t5 interval (240 ° to 300 °), the second flag 2 is obtained, and t2 to t3 interval (120 °).
(° -180 °) and t5-T6 section (300 ° -360)
The third flag 3 is obtained in (). That is, the first,
The relationship between the second and third line voltages Vrs, Vst, Vtr and the flag can be expressed by the following equation (1). When Vst <Vrs <Vtr or Vst>Vrs> Vtr, flag = 1. When Vrs <Vst <Vtr or Vrs>Vst> Vtr, flag = 2. When Vrs <Vtr <Vst or Vrs>Vtr> Vst, flag = 3 ... ( 1)

The computing unit 56 is the first and second units shown in FIG.
And the third phase current command values I0r, I0s, I0t and FIG.
The following arithmetic processing is executed based on the flag of FIG.
The first, second and third converter current command values Ia shown in
, Ib, Ic are output. When the flag is 1, Ia = 0 Ib = I0s Ic = -I0r When the flag is 2, Ia = -I0s Ib = 0 Ic = I0t When the flag is 3, Ia = I0r Ib = -I0t Ic = 0 ... ... (2)

In the above equation (2), when the converter current command values Ia, Ib, Ic are zero, the converters 2, 3, 4 corresponding to these are controlled to stop.

Absolute value calculator 6 connected to calculator 56
1, 62, 63 are absolute values Ia ', Ib', Ic of the first, second and third inverter current command values Ia, Ib, Ic.
′ Is to be obtained.

In order to implement the unity power factor control, the first, second and third converter current detection signal lines 32, 3 are provided.
The first, second, and third low-pass filters 6 are provided at 3, 34.
4, 65, 66 are connected. Low pass filter 6
Reference numerals 4, 65 and 66 remove high frequency ripples due to switching contained in the first, second and third converter currents Irs, Ist and Itr. The first, second and third absolute value calculators 67, 68 and 69 connected to the first, second and third low pass filters 64, 65 and 66 are the first and the first high frequency components removed. The absolute values Irs', Ist ', Itr' of the second and third converter currents Irs, Ist, Itr are obtained.

The fourth, fifth and sixth subtractors 70, 71,
72 is the first, second, and third converter current command values I obtained from the absolute value calculators 61, 62, 63 on one side.
First, second and third converter currents Irs, Ist, Itr obtained from absolute value calculators 67, 68, 69 on the other side from absolute values Ia ', Ib', Ic 'of a, Ib, Ic. Of the error signal Id by subtracting the absolute values Irs', Ist 'and Itr' of
to obtain a, Idb, and Idc. That is, the fourth, fifth and sixth subtractors 70, 71 and 72 are error signal forming calculators for calculating Ia'-Irs' = Ida Ib'-Ist '= Idb Ic'-Itr' = Idc. is there.

The fourth, fifth and sixth subtractors 70, 71,
The first, second, and third duty ratio command generators 73, 74, and 75 connected to 72 amplify or calculate the first, second, and third error signals Ida, Idb, and Idc to perform the first operation. , Switches 43a, 44a of the second and third converters 2, 3, 4
The duty ratio command values Pa of 43b, 44b, 43c and 44c,
It is for obtaining Pb and Pc. The first, second and third duty ratio command values Pa, Pb and Pc have values proportional to the first, second and third error signals Ida, Idb and Idc. However, the first, second and third duty ratio command generators 73, 7
4, 75 are controlled by the output of the comparison calculator 60 as a flag generator. When the flag is 1, the first duty factor command value Pa becomes zero, and when the flag is 2, the second duty factor command value Pa. When Pb becomes zero and the flag is 3, the third duty ratio command value Pc becomes zero. When the duty ratio command value is zero, converters 2, 3, 4 are turned off.

The sawtooth wave generator 76 has a frequency of a sawtooth wave Va for forming a PWM pulse, which is sufficiently higher than the input AC voltages Vr, Vs and Vt (for example, 20 to 20), as schematically shown in FIG. 5A. It occurs at 150kHz). In FIG. 5A, the lowest saw wave Va is set to zero, and the highest saw wave command value Pa.
, Pb, Pc are set larger.

First, second and third PWM comparators 7
7, 78, 79 are command values Pa, Pb obtained from the first, second and third duty factor generators 73, 74, 75,
Pc and the sawtooth wave Va of the sawtooth wave generator 76 are compared as shown in FIG. 5A to form the PWM control signals Ga, Gb and Gc shown in FIGS. 5B, 5C and 5D. Line these 3
The switches 43a, 44 of FIG.
a, 43b, 44b, 43c, 44c. In this embodiment, a high level PWM pulse for turning on the switches 43a, 44a, etc. is generated when Pa, Pb, Pc are larger than the sawtooth wave Va. First PW
The M control signal Ga is supplied by the line 35 to the control terminals of both the first and second switches 43a, 44a of the first converter 2. The second PWM control signal Gb is supplied by line 36 to the control terminals of both the first and second switches 43b, 44b of the second converter 3.
The third PWM control signal Gc is supplied to the first and second switches 43c and 44c of the third converter 4 via the line 37.
Is supplied to both control terminals. Lines 35 and 3
Reference numerals 6 and 37 are connected to the switches 43a to 44c via a well-known switch driving circuit (not shown).

With respect to the R phase, the P of the first converter 2 is in the 0 ° -60 ° section and the 180 ° -240 ° section.
Since the WM control signal Ga is kept at zero, the switch 43
a and 44a are not ON-controlled. Similarly, 60 ° to 12
In the 0 ° section and the 240 ° -300 ° section, the PWM control signal Gb of the second converter 3 is maintained at zero and the switch 4
3b and 44b are not turned on. Also, 120 ° to 1
In the 80 ° section and the 300 ° to 360 ° section, the PWM control signal Gc of the third converter 4 is kept at zero and the switches 43c and 44c are not turned on. Since the input periods of the first, second and third converters 2, 3, 4 are all lower than the input voltage of the operating converter, the idle periods of the converters 2, 3, 4 are stopped. Does not deteriorate the supply performance of DC power. The converter with the higher input voltage of the two converters in operation generates a higher DC voltage than the converter with the lower input voltage. Therefore, when the switches are turned on at the same time, the smoothing capacitor 6 and the load 7 are connected to each other. The current supply is from the higher converter. First, second and third converters 2, 3, 4
Performs AC-DC conversion in both the positive half-wave and the negative half-wave of the AC input voltage, so the combined output of the first, second and third converters 2, 3, 4 is a three-phase full-wave rectifier. Similar to the waveform, it has a small ripple.

Input currents Irs, I of the converters 2, 3, 4
The st and Itr are controlled so as to follow the sine wave converter current command values Ia, Ib, and Ic of the same phase as the sine wave input voltage waveforms Vr, Vs, and Vt of the converters 2, 3, and 4. Therefore, the input power factor of each converter 2, 3, 4 and the power factor at the entire input terminals 1r, 1s, 1t are controlled so as to approach 1, and the input current waveform becomes an approximate sine wave with few harmonic components. .

When the DC output voltage V0 becomes higher than the target value V01, for example , the output of the output voltage control subtractor 51 becomes low and the current amplitude command value I0 decreases, which results in the duty factor command values Pa and Pb. Pc is also reduced, the width of the PWM pulse is narrowed, the output voltage of the converters 2, 3, 4 is reduced, and the voltage V0 of the DC output terminals 7a, 7b is returned to the target value. When the output voltage V0 becomes lower than the target value V01, the operation reverse to that when it becomes high is performed.

This embodiment has the following advantages. (1) Since the AC side and the DC side are electrically insulated by the high frequency transformers 40a, 40b, 40c of the first, second and third converters 2, 3, 4, the transformer 40a,
The sizes of 40b and 40c can be reduced as compared with the low frequency transformer. (2) Connect the first, second and third converters 2 , 3, 4
The three- phase AC input terminals 1r, 1s, and 1t are dispersedly connected to each other, and these DC output terminals are connected in parallel to each other. Therefore, the first, second, and third line voltages Vrs, Vst, and Vtr are connected. Of the first, second and third converters 2, 3,
DC power can be sequentially supplied from No. 4. As a result, it is possible to supply electric power that is three times the electric power capacity of one converter. Therefore, it is possible to prepare three compact converters having a relatively small power capacity and supply three times as much power as one converter. For example, when configuring a 3 kW AC-DC converter according to the conventional method,
A 3KW three-phase converter, a 3KW insulated three-phase or single-phase inverter, and a 3KW rectifier circuit are required, and the overall size becomes large. On the other hand, in this embodiment, 1K
Since 3 KW of DC power can be supplied by three W insulating converters, the overall size and cost can be reduced. (3) First, second and third converters 2, 3, 4
Are configured to switch both positive and negative half-waves of the alternating voltage, and transformers 40a, 40
Since the full-wave rectification circuit is provided on the secondary side of b and 40c, it is possible to perform both rectification and PWM control with one converter, and the overall configuration of the AC-DC converter is significantly increased. It can be simplified and miniaturized. (4) Since the first, second, and third converters 2, 3, and 4 are sequentially paused at intervals of 60 degrees of the sine wave input AC voltage, power loss can be reduced.

[0035]

[Second Embodiment] Next, referring to FIG. 6 and FIG.
The AC-DC converter of the embodiment will be described. However, FIGS. 6 and 7 and FIGS. 8 to 1 showing another embodiment described later.
8, the same parts as those in FIGS. 1 to 5 or parts that are the same as each other are designated by the same reference numerals and the description thereof will be omitted. Also,
For common parts in the second and subsequent embodiments, refer to FIGS.

The AC-DC converter of FIG. 6 detects the first, second and third currents provided in the input lines of the first, second and third converters 2, 3 and 4 in FIG. The reactors 10, 11, and 12 to the main power supply lines of R, S, and T phases connected to the first, second, and third AC input terminals 1r, 1s, and 1t, and the modified control circuit 5a is connected. The structure is the same as that of FIG. 1 except for the above.

In FIG. 6, the first, second and third current detectors 10, 11 and 12 are R, S and T phase currents passing through the first, second and third AC input terminals 1r, 1s and 1t. Ir, I
s, It are detected and sent to the control circuit 5a by lines 32, 33 and 34. In order to simplify the drawing, FIG.
In, the lines 32, 33 and 34 are divided.

As shown in detail in FIG. 7, the control circuit 5a includes first, second and third converter currents Irs, Ist, Itr instead of the low pass filters 64, 65, 66 of FIG.
To obtain the first, second and third converter current calculators 64 ', 65' and 66 ', and other components are the same as those in FIG. First converter current calculator 64 '
Is connected to the lines 32 and 33, the second converter current calculator 65 'is connected to the lines 33 and 35, and the third converter current calculator 65' is connected to the lines 33 and 35.
Converter current calculator 66 'is connected to lines 32 and 35. Further, in order to selectively obtain the current detection signal based on the same flag as in FIG.
And third converter current calculators 64 ', 65', 6
A comparison calculator 60 for flag generation is connected to 6 '.

The first converter current calculator 64 'outputs the following first converter current Irs according to the value of the flag. That is, the arithmetic unit 64 'has Irs when the flag = 1.
= 0, flag = 2, Irs = -Is, and flag = 3, Irs = Ir.

The second converter current calculator 65 'outputs the second converter current Ist shown below according to the value of the flag. That is, the computing unit 65 'outputs I when the flag = 1.
When st = Is and flag = 2, Ist = 0 and when flag = 3, Ist = -It is output.

The third converter current calculator 66 'outputs the following third converter current Itr according to the value of the flag. That is, the computing unit 66 'outputs I when the flag = 1.
When tr = -Ir and flag = 2, Itr = It and flag = 3
At the time of, Itr = 0 is output.

The first, second and third converter currents Irs, Ist, I obtained from the arithmetic units 64 ', 65', 66 '.
tr is sent to the same absolute value calculators 67, 68, 69 as in FIG. Thereby, the control circuit 5 of the second embodiment of FIG.
a can perform the same control as the control circuit 5 of the first embodiment of FIG. As a result, the same effects as those of the first embodiment can be obtained by the second embodiment.

[0043]

[Third Embodiment] In the AC-DC converter of the third embodiment, the control circuit 5 of the AC-DC converter of the first embodiment shown in FIG. 1 is modified into a control circuit 5b shown in FIG. Other than this, the configuration is the same as that of FIG.

The control circuit 5b of FIG. 8 corresponds to the control circuit 5 of FIG.
The first, second, and third sawtooth wave correctors 81, 82, and 83 are added to the above, and the other configurations are the same as those in FIG. The first, second, and third sawtooth wave correctors 81, 82, and 83, which function as a part of the sawtooth wave generator, are provided with the sawtooth wave generator 76 and the first,
It is connected between the second and third comparators 77, 78 and 79. Further, the comparison calculator 6 as a flag generating means.
0 is the first, second, and third sawtooth wave correctors 81, 82, 83
It is connected to the.

The first sawtooth wave corrector 81 saws at the t0 to t1 (0 ° to 60 °) interval and the t3 to t4 (180 ° to 240 °) interval in which the flag shown in FIG. The generation of the wave Va is stopped, and the flag becomes 2. t1 to t2 (60 ° to
120 °) section and t4 to t5 (240 ° to 300 °)
In the section, a sawtooth wave Va having a rising slope shown in FIG. 9 (A) is generated and the flag becomes 3 t2 to t3 (120 ° to 180)
.Degree.) And t5 to t6 (300.degree. To 360.degree.), A sawtooth wave Vb having a falling slope shown in FIG. 9C is generated. The second sawtooth wave corrector 82 generates a sawtooth wave Vb having a falling slope in FIG. 9C in the sections t0 to t1 and the sections t3 to t4 in which the flag is 1, and the flags are t1 to t2 in which the flag is 2. Section and t4
The generation of the sawtooth wave is stopped in the section up to t5, and the sawtooth wave Va having the rising slope is generated in the sections t2 to t3 and t5 to t6 where the flag is 3. The flag of the third sawtooth wave corrector 83 is 1
A sawtooth wave Va having a rising slope is generated in the sections t0 to t1 and t3 to t4, and a sawtooth wave Vb having a falling slope is generated in the sections t1 to t2 and t4 to t5 where the flag is 2.
The generation of the sawtooth wave is stopped in the t2 to t3 section and the t5 to t6 section where the flag is 3. The relationship between the outputs H1, H2 and H3 of the first, second and third sawtooth wave correctors 81, 82 and 83 and the sawtooth wave in each section is as follows. Flag 1 t0 to t1
And t3 to t4 section H1 = 0 H2 = Vb H3 = Va flag 2 t1 to t2 and t4 to t5 section H1 = Va H2 = 0 H3 = Vb flag 3 t2 to t3 and t5 to t6 section H1 = Vb H2 = Va H3 = 0 Note that Va and Vb have a relationship of Vb = -Va. Also, the outputs H1, H2, H of the sawtooth wave correctors 81, 82, 83
Instead of making 3 zero, it can be modified to generate a sawtooth wave Va or Vb. Zero of the outputs H1, H2, H3 means the suspension of the converter, but in synchronization with this, the duty factor command values Pa, Pb, Pc also become zero, so that the PWM control pulse is output from the comparators 77, 78, 79. Does not occur.

The comparators 77, 78, 79 of FIG. 8 operate similarly to those of FIG. 3, and PWM the lines 35, 36, 37.
Send a control signal. FIG. 9 shows inputs and outputs of the first and third comparators 77 and 79 in a part of the interval t1 to t2 (60 ° to 120 °) of FIG. The sawtooth wave Va having the rising slope shown in FIG. 9A and the sawtooth wave Vb having the falling slope shown in FIG. 9C are generated in synchronization with each other and have opposite slopes.
Each of the comparators 77, 78, 79 has a duty ratio command value Pa, Pb,
It is formed so as to generate a positive pulse when Pc is higher than the sawtooth wave Va or Vb. Therefore, in the case of the sawtooth wave Va having a rising slope in FIG. 9A, PWM is performed at t1, t3, t5, etc. synchronized with the rising of the slope voltage as shown in FIG. 9B.
When the pulse generation starts and the sawtooth wave Vb has a falling slope shown in FIG. 9C, the PWM pulse is generated from t2, t4, etc. in the middle of the falling slope as shown in FIG. 9D. The PWM pulse ends at t3, t5, etc. which are started and synchronized with the end of the inclination. As is clear from the comparison between FIG. 9B and FIG. 9D, the overlap period between the output pulse of the one comparator 77 and the output pulse of the other comparator 79 is eliminated or reduced. The PWM pulse generation period is converters 2, 3, 4
Power supply period, the power supply to the smoothing capacitor 6 in FIG. 1 can be dispersed, and the ripple becomes smaller than that in the first embodiment. That is, in the first embodiment, the first, second and third comparators 77, 7
Since the sawtooth wave Va having the same rising slope is input to 8 and 79, the first, second and third PWM control signals Ga and Gb are input.
, Gc pulses rise synchronously, the overlap of PWM pulses increases, and the ripple of the voltage of the smoothing capacitor 6 increases. On the other hand, in the third embodiment,
As is apparent from FIGS. 9B and 9D, overlapping of the PWM control pulses on the time axis is suppressed, power is supplied to the smoothing capacitor 6 in a state where the rest period is short, and ripples are reduced. The same effect as the t1 to t2 section can be obtained in a section other than the t1 to t2 section of FIG. 4 shown in FIG. Also, the same effect as that of the first embodiment can be obtained by the third embodiment.

[0047]

[Fourth Embodiment] In the AC-DC converter of the third embodiment, the control circuit 5 of the AC-DC converter of the first embodiment shown in FIG. 1 is modified into a control circuit 5c shown in FIG. Other than that, the configuration is the same as that of FIG.

The control circuit 5c shown in FIG. 10 differs from the control circuit 5 shown in FIG. 3 in that the first, second and third sawtooth wave selectors 81 ', 82',
83 'is added and the other structure is the same as that of FIG. First, second and third sawtooth wave selectors 81 ', 8
2'and 83 'denote first and second sawtooth wave generators 76 and 7
6a and the first, second and third comparators 77, 78, 79. Further, the comparison calculator 60 as a flag generating means is provided with the first, second and third sawtooth wave selectors 8.
1 ', 82', 83 '.

The first sawtooth wave generator 76 generates the first sawtooth wave Va shown in FIG. 11A as in the first to third embodiments. The second sawtooth wave generator 76a generates the second sawtooth wave Vb 'shown in FIG. 11 (C). This second sawtooth wave Vb '
Corresponds to the first sawtooth wave Va phase-shifted by 180 degrees.

The first, second and third sawtooth wave selectors 81 ',
Reference numerals 82 ′ and 83 ′ are supplied from the comparison calculator 60.
In response to the flag shown in (D), the first and second sawtooth waves Va
, Vb '. The relationship between the flag of FIG. 4D and the first and second sawtooth waves Va and Vb 'is as follows. In the sections t0 to t1 and t3 to t4 in which the flag is 1, the first sawtooth wave selector 81 'outputs zero or selects one of the first and second sawtooth waves Va and Vb'. , The second sawtooth wave selector 82 'selects the second sawtooth wave Vb' and the third sawtooth wave selector 83 'selects the first sawtooth wave Va. Flag is 2
In the intervals t1 to t2 and t4 to t5, the first sawtooth wave selector 82 'selects the first sawtooth wave Va and the second sawtooth wave selector 82' outputs zero or the first sawtooth wave Va. And the second sawtooth wave V
Either a or Vb 'is selected and the third sawtooth wave selector 8 is selected.
3'selects the second sawtooth wave Vb '. In the sections t2 to t3 and t5 to t6 where the flag is 3, the first sawtooth wave selector 81 'selects the second sawtooth wave Vb' and the second sawtooth wave selector 82 'to the first sawtooth wave selector. Select the wave Va and select the third sawtooth wave selector 8
3'outputs zero or the first and second sawtooth waves Va, V
Select one of b '.

FIG. 11 shows inputs and outputs of the first and third comparators 77 and 79 in a part of the section t1 to t2 of FIG. The first comparator 77 compares the first sawtooth wave Va and the first duty ratio command value Pa as shown in FIG. 11A, and compares the first PWM control signal Ga with the first PWM control signal Ga in FIG. 11B. Is output.
The third comparator 79 compares the second sawtooth wave Vb 'with the third duty ratio command value Pc as shown in FIG.
The third PWM control signal Gc shown in (D) is output. The pulse of the first PWM control signal Ga rises at t1, t4, etc. in synchronization with the first sawtooth wave Va, and the second PWM control signal G
The pulse of b rises at t3, t5, etc. in synchronization with the second sawtooth wave Vb '. Therefore, in the fourth embodiment as well as in the third embodiment, PWM between a plurality of PWM control signals is performed.
A pulse shift occurs, and the ripple reduction effect of the output voltage V0 can be obtained as in the third embodiment. Of course, the fourth embodiment also has the same effect as the first embodiment.

[0052]

[Fifth Embodiment] In the AC-DC converter of the fifth embodiment, the control circuit 5 of the AC-DC converter of the first embodiment shown in FIG. 1 is modified into a control circuit 5d shown in FIG. Other than that, the configuration is the same as that of FIG.

The control circuit 5d of FIG. 12 is similar to the control circuit 5 of FIG. 3 in that the first, second and third sawtooth wave correctors 81, 82 and 83 are provided.
Is added, and the other components are the same as those in FIG.
The first, second and third sawtooth wave correctors 81, 82 of FIG.
83 is a sawtooth wave generator 76 and the first, second and third comparators 7
It is connected between 7, 78 and 79. Also, the first
The first, second and third subtractors 57, 58 and 59 for obtaining the second and third line voltages Vrs, Vst and Vtr are
It is connected to the second and third sawtooth wave correctors 81, 82 and 83.

First, second and third sawtooth wave correctors 81, 8
Reference numerals 2 and 83 selectively send out the falling slope sawtooth wave Vb in the same manner as shown by the same reference numerals in FIG. 8 showing the third embodiment. However, the first, second and third sawtooth wave correctors 81, 82 and 83 shown in FIG.
And the first, obtained from the third subtractors 57, 58, 59,
The second and third line voltages Vrs, Vst, Vtr are used to determine the selection of rising and falling sawtooth waves Va, Vb.

FIG. 13 illustrates the selection of the rising slope and falling slope saw waves Va and Vb by the first, second and third saw wave correctors 81, 82 and 83. FIG. 13 (A)
-(F) are the same as FIGS. 4 (A)-(F), and FIG.
(G), (H) and (I) represent outputs H1, H2 and H3 of the first, second and third sawtooth wave correctors 81, 82 and 83, respectively. First
The sawtooth wave corrector 81 of the first embodiment, as shown in FIG.
Is higher than the second and third line voltages Vst and Vtr in the positive half-wave, the period t1 to t3 (60 ° to 1).
A rising slope sawtooth wave Va is generated at 80 °), and the absolute value of the first line voltage Vrs in the negative half-wave is higher than the absolute values of the second and third line voltages Vst and Vtr during the period t4. ~ T6
A falling slope sawtooth wave Vb is generated at (240 ° to 360 °). As shown in FIG. 13 (H), the second sawtooth wave corrector 82 has a period t0 between the first and third line voltages Vrs, Vtr in the positive half-wave of the second line voltage Vst. t2 (0
.Degree..about.60.degree.) And t5.about.t6 (300.degree. To 360.degree.), A rising slope sawtooth wave Va is generated, and the absolute value of the second line voltage Vrs in the negative half wave is the first and third lines. Voltage V
A falling slope sawtooth wave Vb is generated in a period t2 to t4 (120 ° to 240 °) higher than the absolute values of rs and Vtr. As shown in FIG. 13I, the third sawtooth wave corrector 83 has a period t3 in which the third line voltage Vts is higher than the first and second line voltages Vrs, Vst in the positive half-wave. ~ T5 (180 ° ~ 3
(00 °), a rising ramp saw wave Va is generated, and the absolute value of the third line voltage Vtr in the negative half-wave is higher than the absolute value of the first and second line voltages Vrs, Vst t0. ~ T2
A falling slope sawtooth wave Vb is generated at (0 ° to 120 °).
The rising slope saw wave Va of the fifth embodiment is the same as that shown in FIG. 9 (A), and the falling slope saw wave Vb is shown in FIG. 9 (C).
Is the same as that shown in.

Also according to the fifth embodiment, two sawtooth waves Va
, Vb are used, the overlapping of PWM pulses is suppressed as in FIG. 9, and the ripple of the output voltage V0 can be reduced. The fifth embodiment also has the same effect as the first embodiment.

[0057]

[Sixth Embodiment] An AC-DC converter according to a sixth embodiment is constructed such that the first, second and third converters 2, 3 shown in FIG.
4 is the first, second and third converters 2a, 3 of FIG.
a and 4a, and the control circuit 5 of FIG. 1 and FIG.
The control circuit 5e is modified to the same as that of the first embodiment shown in FIG.

The first, second and third converters 2a, 3a and 4a in FIG. 14 are push-pull converters. Taking the first converter 2a as an example, in the first converter 2a, the primary winding of the transformer 40a 'has a center tap and is divided into a winding 41a and a winding 41a'. The winding 41a and the first and second switches 43a and 44a that form one half of the push-pull circuit and the first
2 and the second diodes 45a and 46a are formed in the same manner as those indicated by the same reference numerals in FIG. 2, and are connected between the converter input lines 16 and 17 in the same manner as in FIG. The circuit including the winding 41a ', the third and fourth switches 43a' and 44a ', and the third and fourth diodes 45a' and 46a ', which form the other half of the push-pull circuit, is similar to the one half. And is connected between the input lines 16 and 17. The first and second switches 43a and 44a and the third and fourth switches 43a 'and 44a' are alternately on / off controlled. First between the input lines 16 and 17
When the positive half wave of the line voltage Vrs is input to the first and second switches 43a and 44a,
Current flows in the path of the line 16, the second switch 44a, the first diode 45a, the winding 41a, and the line 17,
A voltage in the direction in which the diode 47a conducts is generated in the secondary winding 42a. When the third and fourth switches 43a 'and 44a' are turned on in the positive half-wave period, the line 16, the fourth switch 44a ', and the third diode 45 are turned on.
current flows in the path of a ', winding 41a', and line 17,
A voltage in the direction in which the diode 48a conducts is generated in the secondary winding 42a. 2 during the negative half-wave period of the input voltage Vrs
A voltage in the opposite direction to that at the time of the positive half-wave is generated in the next winding 42a. The secondary side of the transformer 40a 'has the same configuration as that of FIG. 2 except that it has a smoothing reactor 80a. The second and third converters 3a and 4a are formed in the same manner as the first converter 2a.

As shown in FIG. 15, the control circuit 5e for controlling the push-pull circuit newly includes a second sawtooth wave generator 76a and fourth, fifth and sixth comparators 77 ', 78'.
79 'is provided, and the rest is substantially the same as that of FIG. However, the first sawtooth wave generator 76 of FIG. 15 outputs the first sawtooth wave Va ′ corresponding to the odd sawtooth wave of the sawtooth wave Va shown in FIG. 5A as shown in FIG. 16A. The second sawtooth wave generator 76a of FIG. 15 is formed so as to generate a second sawtooth wave Vb 'corresponding to the even sawtooth wave of the sawtooth wave Va of FIG. First, second and third comparators 77,
78 and 79 are the first, second and third duty ratio command values Pa
, Pb, Pc and the first sawtooth wave Va 'are compared,
First and second switches 43a, 44a, 43b, 44b, 43 of the second and third converters 2a, 3a, 4a.
c, 44c for controlling PWM control signals Ga, Gb
, Gc are generated. Fourth, fifth and sixth comparators 7
Reference numerals 7 ', 78' and 79 'denote first, second and third duty ratio command generators 73, 74 and 75 and a second sawtooth wave generator 76a.
Connected to the first, second and third duty ratio command values Pa
, Pb, Pc and the second sawtooth wave Vb 'are compared to obtain the first,
Third and fourth switches 43a ', 44a', 43b ', 44 of the second and third converters 2a, 3a, 4a.
PWM control signals Ga ', Gb', Gc 'for controlling b', 43c ', 44c' are generated. Although FIG. 16 shows the inputs and outputs of the first and fourth comparators 77, 77 'of FIG. 15, other comparators operate similarly.

As shown in FIGS. 14 to 16, the sixth, fourth, and third embodiments in which the first, second, and third converters 2a, 3a, and 4a are push-pull converters have the same effects as those of the first embodiment. Obtainable.

[0061]

[Seventh Embodiment] An AC-DC converter according to a seventh embodiment is configured so that the first, second and third converters 2, 3 shown in FIG.
4 is the first, second and third converters 2b, 3 of FIG.
b and 4b, and a modified control circuit 5f is provided, and the rest is the same as that of the first embodiment shown in FIG.

The first, second and third converters 2b, 3b and 4b in FIG. 17 are half bridge type converters. Taking the first converter 2b as an example, the first converter 2b includes a primary winding 41a of a transformer 40a.
Has one end connected to one input line 16 via one AC switch circuit composed of the first and second switches 43a and 44a and the first and second diodes 45a and 46a, and the third and The fourth switch 43a ',
44a 'and third and fourth diodes 45a', 46
It is connected to the other input line 17 through the other AC switch circuit composed of a '. The other end of the primary winding 41a is connected to one input line 16 via one resonance first capacitor 81a and to the other input line 17 via a resonance second capacitor 82a. It is connected. The secondary side of the transformer 41a is the same as in FIG. When the first and second switches 43a and 44a are on-controlled in the positive half-wave period of the input AC voltage, the first capacitor 81a, the first switch 43a, the first diode 46a, and the primary winding 41a. The current in the first direction flows through the path. When the third and fourth switches 43a 'and 44a' are turned on in the positive half-wave period, the second capacitor 82a, the primary winding 41a, the third switch 43a ', and the fourth diode are turned on. A current in the second direction flows through the path 46a '. When the first and second switches 43a and 44a are ON-controlled in the negative half-wave period of the input AC voltage, the first capacitor 81a and the primary winding 4
1a, a second switch 44a, a first diode 45a
The current in the second direction flows in the path of. When the third and fourth switches 43a 'and 44a' are turned on during the negative half-wave period, the second capacitor 82a, the fourth switch 44a ', the third diode 45a', and the primary winding Line 41
A current in the first direction flows in the path a. Therefore, the voltage can be obtained in the secondary winding 42a in both the positive half wave and the negative half wave of the input AC voltage. The second and third converters 3b and 4b operate similarly to the first converter 2b.

The control circuit 5f of FIG. 18 transforms the duty factor command calculators 73, 74, 75 of the control circuit 5 of FIG. 3 into frequency command calculators 73 ', 74', 75 ', and the output stage has a third circuit. First, second and third gate signal generators 91, 92, 93
And NOT circuits 94, 95, and 96, and the other configurations are the same as those in FIG. First of FIG. 17,
The second and third converters 2b, 3b, 4b include the inductances of the primary windings 41a to 41c and the capacitor 81a.
To 81c, 82a to 82c are resonance type converters, and therefore, even if the duty ratios of the first to fourth switches are kept constant at 50%, the secondary winding side can be changed by changing the switching frequency. The amount of power supplied to the Therefore, control of the DC output voltage V0 can be achieved by controlling the switching frequency. Also,
The magnitude of the converter input current can be achieved by controlling the switching frequency. The frequency command calculators 73 ', 74', 75 'for executing frequency control are based on the outputs of the subtractors 70, 71, 72 in the previous stage, like the duty factor command calculators 73, 74, 75 in FIG. The frequency command values Fa, Fb, Fc are created. The first, second, and third gate signal generators 91, 92, 93 have frequency command values Fa,
A control pulse having a duty ratio of 50% is generated at a frequency designated by Fb and Fc. The repetition frequency of the control pulse is, for example, 20 to 150 kHz. First including a control pulse,
The second and third control signals Ga, Gb, Gc are the first, second and third converters 2b, 3b, 4b of FIG.
And the second switches 43a, 44a, 43b, 44b,
It is supplied to the gates 43c and 44c. The first, second and third NOT circuits 94, 95 and 96 connected to the gate signal generators 91, 92 and 93 are phase inversion signals of the first, second and third control signals Ga, Gb and Gc. Ga ', Gb
', Gc' are formed, and the first to third converters 2b,
3b and 4b third and fourth switches 43a ', 44
It is supplied to the gates of a ', 43b', 44b ', 43c' and 44c '.

The same effects as those of the first embodiment can be obtained by the seventh embodiment.

[0065]

[Modification] The present invention is not limited to the above-described embodiment, and the following modifications are possible. (1) First, second and third converters 2, 3, 4,
Converter types other than 2a, 3a, 4a, 2b, 3b, 4b can be used. For example, the first in FIG.
And second capacitors 81a to 81c, 82a to 82c
Is a capacitor for voltage division, and the first to fourth switches 4
PWM control of 3a-44a '43b-44b' and 43c-44c 'is possible. Further, a pair of AC switches similar to the first to fourth switches can be connected to the positions of the first and second capacitors 81a and 82a to form a bridge converter. (2) Push-pull converters 2a and 3 in FIG.
a, 4a and the half-bridge converter 2 of FIG.
Also in b, 3b, and 4b, the current detection can be the R, S, and T phase current detection as in FIG. 6, and the control circuit side can convert to the converter current as in FIG. 7. (3) Push-pull converters 2a and 3 in FIG.
Also in a and 4a, the PWM control signal can be created by combining the rising and falling sawtooth waves in the same manner as in FIG. (4) Push-pull converters 2a, 3 in FIG.
Also in a and 4a, as shown in FIG.
Two sawtooth waves can be used to form the PWM signal. In addition, the resonant converters 2b, 3b, 4b of FIG.
Alternatively, also in the bridge converter, the switching phases of the R, S, and T phases can be shifted. (5) An analog-to-digital converter (ADC) may be provided at the input stage of the control circuits 5 to 5f so that the control circuit has a digital circuit configuration.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an AC-DC converter according to a first embodiment.

FIG. 2 is a circuit diagram showing in detail the first, second and third converters of FIG.

FIG. 3 is a circuit diagram showing the control circuit of FIG. 1 in detail.

FIG. 4 is a waveform diagram showing a state of each part of FIG.

5 is a waveform diagram schematically showing the input and output of the comparator of FIG.

FIG. 6 is a circuit diagram showing an AC-DC converter according to a second embodiment.

FIG. 7 is a circuit diagram showing a control circuit of FIG.

FIG. 8 is a circuit diagram showing a control circuit of a third embodiment.

9 is a waveform diagram schematically showing the input and output of the comparator of FIG.

FIG. 10 is a circuit diagram showing a control circuit according to a fourth embodiment.

11 is a waveform diagram schematically showing the input and output of the comparator of FIG.

FIG. 12 is a circuit diagram showing a control circuit according to a fifth embodiment.

13 is a waveform diagram showing a state of each part of FIG.

FIG. 14 is a circuit diagram showing an AC-DC converter of a sixth embodiment.

FIG. 15 is a circuit diagram showing the control circuit of FIG. 14 in detail.

16 is a waveform diagram schematically showing the input and output of the comparator of FIG.

FIG. 17 is a circuit diagram showing an AC-DC converter according to a seventh embodiment.

FIG. 18 is a circuit diagram showing the control circuit of FIG. 17 in detail.

[Explanation of symbols]

1r, 1s, 1t Three-phase AC input terminals 2 to 2b, 3 to 3b, 4 to 4b First, second and third converters 5 to 5f Control circuit 6 Smoothing capacitor

Claims (5)

(57) [Claims] 1. A first, second, and third AC input terminal connected to a three-phase AC power supply, and a first AC-DC converter connected to the first and second AC input terminals, A second AC-DC converter connected to the second and third AC input terminals; a third AC-DC converter connected to the first and third AC input terminals; second and third exchanges - a control circuit for a DC converter, the first, second and third exchanges -; and a common smoothing capacitor connected to the DC output terminal of the DC converter, wherein the first , second and third exchanges - each DC converter, intermittently a transformer having a primary winding and a secondary winding, an AC voltage of the three-phase AC power source to the primary winding of the transformer An AC switching circuit for applying the voltage; and the transformer Wherein an insulating converter that includes a full-wave rectifier circuit for rectifying a voltage of the secondary winding, the control circuit, the force of the first, three-phase AC power in the second and third AC input terminals The exchange to improve the rate
A three-phase AC-DC converter that controls a flow switching circuit. Wherein said first, first second and third AC input terminals, having a voltage detection circuit for detecting a voltage between the second and third lines, said control circuit, said first The three-phase according to claim 1, further comprising means for selectively suspending one of the first, second and third AC-DC converters to which the lowest line voltage is input. AC-DC converter. 3. The control circuit comprises two AC-DC converters operating in the first, second and third AC-DC converters.
The three-phase AC-DC converter according to claim 2, further comprising means for shifting a switching timing of the AC switching circuit of the DC converter. Wherein said control circuit, said first, second and third exchanges - DC converter - first indicating the duty ratio of the AC switching circuit of data, the second and third duty ratio command value First, second and third duty factor command value generators, and sawtooth wave generating means for selectively generating a first sawtooth wave having a rising slope and a second sawtooth wave having a falling slope, The first, second, and third duty ratio command values are compared with the first or second sawtooth wave to form first, second, and third PWM control signals, and the first, second and third PWM control signals are formed. First, second and third comparators for supplying the AC switching circuits of the second and third AC-DC converters, and among the first, second and third AC-DC converters The comparator for one of the two operating at
For controlling the sawtooth wave generating means so as to supply the second sawtooth wave to the comparator for the other of the two units. The three-phase AC-DC converter according to claim 2. Wherein said control circuit, said first, second and third exchanges - DC converter - first indicating the duty ratio of the AC switching circuit of data, the second and third duty ratio command value First, second and third duty ratio command value generators to be generated, sawtooth wave generating means for selectively generating first and second sawtooth waves having phases different from each other by 180 degrees, the first, The first, second and third PWM control signals are formed by comparing the second and third duty ratio command values with the first or second sawtooth wave to form the first, second and third PWM control signals. First, second and third comparators for supplying the alternating current switching circuit of the alternating current-direct current converter, and operating in the first, second and third alternating current-direct current converters 2. The first to the comparator for one of the pedestals
For controlling the sawtooth wave generating means so as to supply the second sawtooth wave to the comparator for the other of the two units. The three-phase AC-DC converter according to claim 2.