JPH08149812A - Rectification device - Google Patents

Abstract

PURPOSE: To improve power factor, suppress ripple current, extend the life of a smoothing capacitor, and reduce capacity. CONSTITUTION: In a rectification device where a diode bridge 2 for all-wave rectification is connected between the terminals of an AC power supply 1 and at the same time a smoothing capacitor 3 is connected between the positive voltage terminal and negative voltage terminal of the diode bridge 2, a reactor 4 and a forward-connected diode 5 are serially connected between the positive voltage terminal of the diode bridge 2 and the smoothing capacitor 3 and a reactor 7 and a capacitor 8 are serially connected in parallel with the serially connected circuit of the reactor 4 and the diode 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rectifier, and more particularly to a rectifier capable of achieving a high power factor.

[0002]

2. Description of the Related Art Conventionally, with the use of inverters in air conditioners, lighting equipment, etc., there has been a rapid increase in the load of rectifiers that generate a large amount of harmonics in comparison with conventional AC loads such as motors and incandescent lamps. When such a rectifier load is used, the current will contain harmonics, which will affect the commercial power supply and cause voltage distortion in the power system, leading capacitors, transformer humming, and ignition. Such a problem is occurring.

Against this background, there has been a strong demand for improving the power factor of the rectifier and reducing the harmonic current. 2. Description of the Related Art Conventionally, there is a device (called a charge pump circuit) shown in FIG. 7 as a rectifying device that can achieve improvement in power factor. In this device, a pair of capacitors 63 and 64 are connected in parallel between a positive voltage terminal and a negative voltage terminal of a diode bridge 62 connected between terminals of an AC power supply 61, and the positive and negative voltages of both capacitors 63 and 64 are connected. A reactor 65 and a diode 65a are connected in series between the voltage terminals. The capacitor 64 is a smoothing capacitor. Further, the inductance component and the resistance component of the power source impedance are indicated by 66 and 67, respectively.

FIG. 8 shows the AC power supply voltage Es and the voltage Vr across the output terminals of the diode bridge 62 in the device shown in FIG.
ec, power supply current Is, current Ic flowing through the capacitor 63
1, current IL2 flowing through the reactor 65, capacitor 64
Ic2 flowing through the capacitor, voltage Vd across the terminals of the capacitor 64
It is a figure which shows the time change of c. As is clear from this figure, the charge is accumulated in the capacitor 63 in the period modeI, and is accumulated and discharged in the capacitor 63 in the subsequent period modeII, so that the conduction angle of the input current is increased and the power factor is improved. Can be made. Specifically, the power supply voltage is 200 V, the DC load is 2.2 kW, the inductance component of the power supply impedance is 450 μH, the resistance component of the power supply impedance is 0.38 Ω, the inductance of the reactor 65 is 4 mH, and the capacitance of the capacitor 63 is 15
0 μF, the capacitance of the smoothing capacitor 64 is 1800
When each is set to μF, the power factor can be improved to about 90%. However, since the power source impedance and the capacitor 63 form a series resonance circuit, a higher harmonic current is involved.

FIG. 9 is an electric circuit diagram showing a rectifying device capable of further improving the power factor. In this device, the capacitor 63 of the device of FIG. 7 is replaced with a series resonance circuit in which the capacitor 63 and a reactor 68 are connected in series (charge pump type high power factor diode rectifier circuit, Kazuyuki Hori, Isao Takahashi,
(See 1993 Hokuriku Branch Union Conference on Electrical Engineering). FIG.
0 is the AC power supply voltage Es in the device shown in FIG. 9, the voltage Vrec between the output terminals of the diode bridge 62, the power supply current Is, the current IL1 flowing through the reactor 68, and the reactor 65.
Current IL2 flowing through the capacitor Ic and current Ic flowing through the capacitor 64
2 is a diagram showing a time change of the voltage Vdc between terminals of the capacitor 64. FIG. This device includes a condenser 63 and a reactor 6
The series resonance circuit with 8 can increase the electric charge accumulated in the capacitor 63 in the period modeI and further improve the power factor. Specifically, when the inductance of the reactor 68 is set to 4 mH and other constants are set in the same manner as in the rectifier of FIG. 7, the power factor can be improved to about 95%. Further, since the reactor having the inductance larger than the inductance component of the power source impedance is connected in series when the capacitor 63 is turned on, it is possible to prevent the generation of high-order harmonic current.

[0006]

When the rectifier having the configuration shown in FIG. 7 is adopted, the power factor can be improved as described above, but the inductance component of the power source impedance and the capacitance of the capacitor 63 are connected in series. Since the resonance circuit is formed, there is a problem that high-order harmonic current is generated.

When the rectifier having the structure shown in FIG. 9 is adopted, the power factor can be further improved as described above.
Since the capacitor 64 is charged in the period modeII following the period modeI, the input current to the capacitor 64 becomes a large ripple current equivalent to that of the conventional rectifier, and is restricted by both the capacitor life and the DC voltage pulsation. A large capacity capacitor must be adopted as the capacitor 64 (specifically, in the case of FIGS.
(About Arms).

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a rectifying device capable of improving a power factor, reducing a high-order harmonic current, and reducing a capacitor ripple current. It is intended to be provided.

[0009]

A rectifying device according to claim 1,
A reactor and a forward-connected diode are connected in series between the positive voltage terminal of the diode bridge and the smoothing capacitor, and the reactor and the capacitor are connected in series in parallel with the series connection circuit of the reactor and the diode.

According to another aspect of the rectifying device of the present invention, the second reactor, the first reactor, and the diodes connected in series are serially connected in this order between the positive voltage terminal of the diode bridge and the smoothing capacitor. A capacitor is connected in series in parallel with a series connection circuit of one reactor and a diode. In the rectifier of claim 3, a first reactor and a diode connected in series are connected in series between the positive voltage terminal of the diode bridge and the smoothing capacitor, and a series connection circuit of the first reactor and the diode is provided. The capacitors are connected in series in parallel, and the second reactor is connected in series with the AC power supply.

[0011]

According to the rectifier of claim 1, since the series resonance circuit is constituted by the series connection circuit of the reactor and the capacitor and the smoothing capacitor, and the capacitance of the smoothing capacitor is remarkably large. The resonance frequency of the series resonance circuit becomes substantially equal to the resonance frequency of the series connection circuit, so that the power factor can be improved and high-order harmonic current can be reduced as in the rectifier of FIG. And in FIG.
In the rectifier of No. 1, the smoothing capacitor is not charged in the period modeI, and
The smoothing capacitor was charged only in I, but in the present invention, since the series connection circuit of the reactor and the capacitor and the smoothing capacitor are connected in series, the smoothing capacitor is also in the period modeI. Is charged. Further, since the series connection circuit of the reactor and the diode connected in the forward direction and the series connection circuit of the reactor and the capacitor do not form a parallel resonance circuit, it is possible to speed up the flow of current when the rectifier circuit is turned on. it can. Therefore, the conduction angle of the input current can be increased to improve the power factor, and the peak value of the rectifier circuit input current can be reduced to reduce the ripple current as the conduction angle of the input current is increased. You can

In the rectifier according to the second aspect of the present invention, the second reactor, the capacitor, and the smoothing capacitor form a series resonance circuit, and the capacitance of the smoothing capacitor is extremely large. The resonance frequency of the series connection circuit composed of the reactor and the capacitor becomes substantially equal to the resonance frequency of the series connection circuit, so that the power factor can be improved and the higher-order harmonic current can be reduced as in the rectifier of FIG. Then, in the rectifying device of FIG. 9, the period mod
Although the smoothing capacitor is not charged in eI and the smoothing capacitor is charged only in the period modeII, in the present invention, the capacitor and the smoothing capacitor are connected in series. Therefore, the smoothing capacitor is charged even in the period modeI. Since the series connection circuit of the first reactor and the diode connected in the forward direction and the capacitor do not form a parallel resonance circuit, it is possible to speed up the flow of current when the rectifier circuit is turned on. Therefore,
The conduction angle of the input current can be increased to improve the power factor, and moreover, the peak value of the rectifier circuit input current can be reduced and the ripple current can be reduced with the increase of the conduction angle of the input current. . Also, since both reactors are connected in series in the charging circuit for the capacitor,
The inductance of the first reactor can be reduced.

In the rectifier according to the third aspect of the present invention, the series resonance circuit is constituted by the second reactor, the capacitor, and the smoothing capacitor which are connected in series with the AC power source, and the capacitance of the smoothing capacitor is remarkably high. Because it's big
The resonance frequency of the series connection circuit including the second reactor and the capacitor connected in series with the AC power supply is substantially equal to the resonance frequency of the series connection circuit, improving the power factor as well as the rectifier of FIG. The harmonic current can be reduced. Then, in the rectifying device of FIG.
In I, the smoothing capacitor was not charged, and the smoothing capacitor was charged only in the period modeII, but in the present invention, the capacitor and the smoothing capacitor are connected in series. Therefore, the smoothing capacitor is charged even in the period modeI. Since the series connection circuit of the first reactor and the diode connected in the forward direction and the capacitor do not form a parallel resonance circuit, it is possible to speed up the flow of current when the rectifier circuit is turned on. Therefore,
The conduction angle of the input current can be increased to improve the power factor, and moreover, the peak value of the rectifier circuit input current can be reduced and the ripple current can be reduced with the increase of the conduction angle of the input current. . Also, since both reactors are connected in series in the charging circuit for the capacitor,
The inductance of the first reactor can be reduced. Further, since the second reactor is connected in series with the AC power source, the rectifier main body portion from the diode bridge to the smoothing capacitor can be downsized.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings showing embodiments. FIG. 1 is an electric circuit diagram showing an embodiment of the rectifying device of the present invention. In this rectifier, a diode bridge 2 for full-wave rectification is connected between terminals of an AC power source 1, and a smoothing capacitor 3 is connected between a positive voltage terminal and a negative voltage terminal of the diode bridge 2. ing. A series connection circuit 6 of a first reactor 4 and a diode 5 connected in order is connected between a positive voltage terminal of the diode bridge 2 and a smoothing capacitor 3, and a second reactor 7 and a capacitor 8 are connected.
The serial connection circuit 9 is connected in parallel with the serial connection circuit 6. In addition, in FIG. 1, 10 and 11 respectively indicate an inductance component and a resistance component of the power source impedance. Further, Es is an AC power supply voltage, Is is a power supply current, Vrec is a voltage between the output terminals of the diode bridge 2, IL1 is a current flowing through the series connection circuit 9, IL2 is a current flowing through the series connection circuit 6, and Ic2. Indicates a current flowing through the smoothing capacitor 3, and Vdc indicates a terminal voltage of the smoothing capacitor 3.

FIG. 2 shows the AC power supply voltage Es, the power supply current Is, and the voltage Vre between the output terminals of the diode bridge 2.
c, the current IL1 flowing through the series connection circuit 9, the current IL2 flowing through the series connection circuit 6, the current Ic2 flowing through the smoothing capacitor 3, and the inter-terminal voltage Vdc of the smoothing capacitor 3.
It is a figure which shows the time change of. In this rectifier, the second reactor 7, the capacitor 8 and the smoothing capacitor 3 form a series resonance circuit. However, since the smoothing capacitor 3 has a significantly larger electrostatic capacitance than the capacitor 8, Therefore, the combined capacitance of both capacitors 3 and 8 becomes substantially equal to the electrostatic capacitance of the capacitor 8, and the resonance frequency f of this series resonance circuit is given by the formula 1.

[0016]

[Equation 1]

However, L1 is the inductance of the second reactor 7, and C1 is the capacitance of the capacitor 8. Also,
Since the inductance L1 of the second reactor 7 is larger than the inductance component of the power source impedance, it is possible to reduce high-order harmonic currents as in the rectifier shown in FIG. Further, since the series resonance circuit has the smoothing capacitor 3 connected in series with the series connection circuit 9 of the second reactor 7 and the capacitor 8, if only the capacitor 8 is used in the charging period modeI for the capacitor 8. No
The smoothing capacitor 3 is also charged through the series connection circuit 6. Then, in the discharging period modeII of the capacitor 8, the smoothing capacitor 3 is further charged by the difference between the discharging current of the capacitor 8 and the current of the first reactor 4. Further, when the rectifier circuit is not conducting, the diode 5 connected between the first reactor 4 and the capacitor 8 prevents the series connection circuits 6 and 9 from forming a parallel resonance circuit. To start the flow of electric current at. Therefore, the conduction angle of the input current of the smoothing capacitor 3 can be increased, and the power factor can be improved. Further, since the conduction angle of the input current of the smoothing capacitor 3 is enlarged, the peak value of the input current of the rectifier circuit can be reduced and the ripple current can be reduced.

Further, the power source voltage is 200 V, the DC load is 2.2 kW, the inductance component of the power source impedance is 450 μH, and the resistance component of the power source impedance is 0.3.
The power factor is improved to 94% when 8Ω, the inductance of the first reactor 4 and the second reactor 7 is set to 4 mH, the capacitance of the capacitor 8 is set to 150 μF, and the capacitance of the smoothing capacitor 3 is set to 1800 μF. It was possible to reduce the ripple current to 7 Arms.

[0019]

Second Embodiment FIG. 3 is an electric circuit diagram showing another embodiment of the rectifying device of the present invention. This rectifier has a capacitor 8
Is connected in parallel with the series connection circuit 6, and the second reactor 7 is connected in series with the series connection circuit 6, which is the only difference from the embodiment of FIG. Further, FIG. 4 shows the AC power supply voltage Es and the power supply current I.
s, the voltage Vrec between the output terminals of the diode bridge 2,
A current Ic1 flowing through the capacitor 8, a current IL2 flowing through the series connection circuit 6, and a current I flowing through the smoothing capacitor 3.
It is a figure which shows the time change of the voltage Vdc between terminals of c2 and the capacitor | condenser 3 for smoothing.

In this rectifying device, during the charging period modeI of the capacitor 8, the same operation as in the embodiment of FIG. 1 is performed and the smoothing capacitor 3 is also charged. However, the smoothing capacitor 3 is connected to the second reactor 7 and the first
Since the charging is performed through the reactors 4 in series, the inductance of the first reactor 4 can be reduced by the amount of the second reactor 7 interposed in series. Then, in the discharge period modeII of the capacitor 8,
Discharge is performed only through the first reactor 4. Therefore, in order to make the resonance cycle of the charging current of the capacitor 8 equal to the total charging cycle, the capacitance of the capacitor 8 must be increased. However, considering the volume, weight, cost, etc., the smaller size of the first reactor 4 is more effective, so that the increase in the capacitance of the capacitor 8 is not particularly inconvenient.

Further, in this rectifying device, the second reactor 7 is connected in series to the first reactor 4 constituting the discharging circuit of the capacitor 8, so that the output terminal of the diode bridge 2 is cut off when the input current is cut off. Voltage Vr
Although ec rises and the conduction angle of the input current of the smoothing capacitor 3 is slightly narrowed as compared with the rectifier of FIG. 1, the power factor can be sufficiently improved and the ripple current can be reduced. Specifically, the capacitance of the capacitor 8 is 260 μF
And the other constants were set in the same manner as in the rectifier of FIG. 1, the power factor could be improved to 93% and the ripple current could be reduced to 8 Arms.

[0022]

Third Embodiment FIG. 5 is an electric circuit diagram showing still another embodiment of the rectifying device of the present invention. This rectifier is different from the rectifier of FIG. 3 in that the second reactor 7 is connected in series with the AC power supply 1. Therefore, in the case of this embodiment, the same operation as that of the rectifying device of FIG. 3 is achieved, and the AC power supply voltage Es, the power supply current Is, the voltage Vrec between the output terminals of the diode bridge 2, and the current Ic flowing through the capacitor 8 are obtained.
1, the current IL2 flowing through the series connection circuit 6, the current Ic2 flowing through the smoothing capacitor 3, and the inter-terminal voltage Vdc of the smoothing capacitor 3 are also as shown in FIG. As a result, the power factor can be sufficiently improved and the ripple current can be reduced similarly to the rectifier of FIG. Specifically, when each constant was set in the same manner as in the rectifier of FIG. 3, the power factor could be improved to 93%, and the ripple current could be reduced to 8 Arms.

Further, in this embodiment, since the second reactor 7 is connected to the AC power source 1 in series,
The degree of freedom in arranging the second reactor 7 with respect to the rectifier main body portion from the diode bridge 2 to the smoothing capacitor 3 is increased, and the rectifier main body portion can be downsized. Usually, an electrolytic capacitor that can obtain a large capacity is used as the smoothing capacitor 3. The life of the electrolytic capacitor is defined by the effective value of the ripple current as is well known in the art, and the smaller the capacitance, the smaller the allowable ripple current. Therefore, by adopting the rectifying device of the present invention, the life is extended, The capacity can be reduced.

When the rectifying device of FIGS. 3 and 5 is adopted, the ribble current can be reduced from 12 Arms to 8 Arms (about 2/3) as compared with the case where the rectifying device of FIG. 9 is adopted. Assuming, for example, that an electrolytic capacitor having a life characteristic shown in FIG. 6 (allowable ripple is 13.9 A) is used, the ripple reduction rate (applied ripple current / allowable ripple) is shown in FIG. It becomes 0.86 and 0.58 for each of the five rectifiers, and the life can be doubled. Specifically, assuming that the ambient temperature is 60 ° C., the life of the rectifier of FIG. 9 is about 12,000 hours, while the life of the rectifier of FIGS. 3 and 5 is about 21 hours. 1,000 hours.

When an inverter for driving a compressor motor such as an air conditioner is used as the load of the rectifier, the DC voltage ripple has a small voltage pulsation from the viewpoint of preventing abnormal vibration of the compressor. Is desired. From this viewpoint, the ripple voltage of the rectifier shown in FIG.
If the capacity of the smoothing capacitor 64 is determined so as to be equal to the ripple voltage of the rectifier of FIG. 1, 1.5 times the capacity of the smoothing capacitor 3 of the rectifier of FIG. 1 (specifically, other constant When set as described above, it becomes 2700 μF).

Therefore, by reducing the ripple current, the smoothing capacitor 3 has a longer life and a smaller capacity (smaller size).
It can be seen that

[0027]

According to the invention of claim 1, it is possible to reduce high-order harmonic currents, to enlarge the conduction angle of the input current to improve the power factor, and to increase the conduction angle of the input current. Along with this, there is a unique effect that the peak value of the rectifier circuit input current can be reduced and the ripple current can be reduced.

According to the second aspect of the present invention, higher harmonic currents can be reduced, the conduction angle of the input current can be increased to improve the power factor, and further, the conduction angle of the input current can be increased. As a result, the peak value of the rectifier circuit input current can be reduced to reduce the ripple current, and the inductance of the first reactor can be reduced. The invention of claim 3 can reduce high-order harmonic currents,
The conduction angle of the input current can be expanded to improve the power factor, and moreover, the peak value of the input current of the rectifier circuit can be reduced and the ripple current can be reduced with the expansion of the conduction angle of the input current. Further, it is possible to reduce the inductance of the first reactor, and further it is possible to reduce the size of the rectifying device main body portion from the diode bridge to the smoothing capacitor.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of a rectifying device of the present invention.

2 is an AC power supply voltage Es in the rectifier of FIG.
Power supply current Is, voltage between output terminals of diode bridge V
rec, the current IL1 flowing through the series connection circuit 9, the current IL2 flowing through the series connection circuit 6, the current Ic2 flowing through the smoothing capacitor, and the inter-terminal voltage Vdc of the smoothing capacitor.
It is a figure which shows the time change of.

FIG. 3 is an electric circuit diagram showing another embodiment of the rectifying device of the present invention.

4 is an AC power supply voltage Es in the rectifier of FIG.
Power supply current Is, voltage between output terminals of diode bridge V
FIG. 6 is a diagram showing a temporal change of rec, a current Ic1 flowing through a capacitor, a current IL2 flowing through a series connection circuit, a current Ic2 flowing through a smoothing capacitor, and a voltage Vdc between terminals of the smoothing capacitor.

FIG. 5 is an electric circuit diagram showing still another embodiment of the rectifying device of the present invention.

FIG. 6 is a diagram showing an example of life characteristics of an electrolytic capacitor.

FIG. 7 is an electric circuit diagram showing an example of a conventional rectifying device.

8 is an AC power supply voltage Es in the rectifier of FIG.
Voltage Vrec between output terminals of diode bridge, power supply current Is, current Ic1 flowing in capacitor, current IL2 flowing in reactor, current Ic flowing in smoothing capacitor
FIG. 2 is a diagram showing a time change of a voltage Vdc between terminals of a smoothing capacitor.

FIG. 9 is an electric circuit diagram showing another example of a conventional rectifying device.

10 is an AC power supply voltage E in the rectifier of FIG.
s, voltage Vrec between output terminals of diode bridge, power supply current Is, current IL1 flowing in reactor 68, current IL2 flowing in reactor 65, current Ic2 flowing in smoothing capacitor, voltage Vdc between terminals of smoothing capacitor
It is a figure which shows the time change of.

[Explanation of symbols]

 1 AC power supply 2 Diode bridge 3 Smoothing capacitor 4 First reactor 5 Diode 7 Second reactor 8 Capacitor

Claims (3)

[Claims] 1. A diode bridge (2) for full-wave rectification is connected between terminals of an AC power supply (1), and smoothing is performed between a positive voltage terminal and a negative voltage terminal of the diode bridge (2). In the rectifying device to which the capacitor (3) is connected, the reactor (4) and the diode (5) connected in series are connected in series between the positive voltage terminal of the diode bridge (2) and the smoothing capacitor (3). A rectifier, which is connected, and in which a reactor (4) and a diode (5) are connected in series with a reactor (7) and a capacitor (8) in series. 2. A diode bridge (2) for full-wave rectification is connected between terminals of an AC power source (1), and smoothing is performed between a positive voltage terminal and a negative voltage terminal of the diode bridge (2). In the rectifying device to which the capacitor (3) is connected, the second reactor (7), the first reactor (4) and the forward reactor (4) are provided between the positive voltage terminal of the diode bridge (2) and the smoothing capacitor (3). The diode (5) connected is serially connected in this order, and the capacitor (8) is serially connected in parallel with the series connection circuit of the first reactor (4) and the diode (5). Rectifier. 3. A diode bridge (2) for full-wave rectification is connected between terminals of an AC power source (1) and smoothing is performed between a positive voltage terminal and a negative voltage terminal of the diode bridge (2). In the rectifying device to which the capacitor (3) is connected, the first reactor (4) is provided between the positive voltage terminal of the diode bridge (2) and the smoothing capacitor (3).
And a diode (5) connected in series are connected in series, and the first reactor (4) and the diode (5) are connected.
A capacitor (8) is connected in series with the series connection circuit of, and a second reactor (7) is connected in series with the AC power supply (1).
A rectifying device characterized by being connected to.