JPH0614549A - Nonlinear impedance circuit and single-phase rectifying circuit - Google Patents

Abstract

PURPOSE:To improve the power factor on power source side without needing any control operation and remove the harmonic ingredients of an input current, in a single-phase rectifying circuit which varies the impedance of a circuit, according to the polarity of a current or voltage, by simple constitution. CONSTITUTION:A diode D2 and a capacitor C2 are connected in series between output terminals T1 and T2, and a diode D3 is connected to both ends of the series circuit consisting of the capacitor C1 and the diode D2. A nonlinear impedance circuit 10 is constituted by connecting a diode D1 to both ends of the series circuit consisting of the diode D2 and the capacitor C2. Two nonlinear impedance circuits 10 and 10' are connected to one end of an AC power source through an AC reactor La and the positive and negative DC output terminals of a rectifying circuit, and the other end of the AC power source AC is connected to the junction between diodes D13 and D14 in series.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-linear impedance circuit whose impedance changes according to the polarity of current or voltage, and a single-phase rectifier circuit using this non-linear impedance circuit.

[0002]

2. Description of the Related Art As is well known, single-phase rectifier circuits include home appliances and other office automation equipment, factory automation equipment, small electrical equipment,
Widely used in lighting equipment. The AC input current of this rectifier circuit contains many harmonics, causing problems such as giving radio noise to surrounding electrical equipment and destroying the power factor improving capacitor. For this reason, recently, legal regulations for harmonics of this kind have begun to be examined.
On the other hand, since the AC input current of the single-phase rectifier circuit flows only during a period when the AC power supply voltage is above a certain value, the power factor on the power source side is poor and there is a strong demand for improvement of this power factor.

Under the above background, various circuits have been conventionally provided to improve the power factor and the waveform on the power source side. For example, a reactor is inserted on the input side (power source side) of a single-phase rectifier circuit. To increase the flow width of the AC input current to improve the power factor and waveform.Connect a step-up chopper for current control after the single-phase rectifier circuit, and use this chopper to control the AC input current as a sine wave. A method of controlling the AC input current in a sinusoidal manner as a converter by regenerating the current control inverter is known.

[0004]

However, the above method is convenient because it does not require control, but it has a drawback that the harmonic content contained in the AC input current is large and the regulation is not satisfied. Moreover, although the method can sufficiently comply with the regulation, a control circuit for switching control of the semiconductor switch element of the chopper or the inverter is required.
There is a problem that the device configuration including the main circuit becomes complicated and expensive, and switching noise and switching loss occur, resulting in poor efficiency.

Here, the inventor has noticed that by combining a diode and a capacitive impedance element or an inductive impedance element, it is possible to realize a non-linear impedance circuit whose impedance changes according to the polarity of current or voltage. It was found that the above problem can be solved by applying the non-linear impedance circuit to the single-phase rectifier circuit. That is, an object of the present invention is to provide a non-linear impedance circuit having a simple structure, and by using this circuit, a harmonic component of an AC input current can be obtained without requiring control of a switch element or the like. Another object of the present invention is to provide a single-phase rectifier circuit that has a simple structure, high efficiency, and a low cost, as well as being eliminated and improving the power factor on the power supply side.

[0006]

In order to achieve the above object, a nonlinear impedance circuit according to the present invention has a first structure.
And n (n is an integer of 2 or more) impedance elements and (n-1) diodes, all of which are capacitive impedance elements or inductive impedance elements, are alternately connected in series between the second output terminal and the second output terminal. Then, among the connection points of each impedance element and the diode, from the one closest to the first output terminal, the second output terminal and the first output terminal are alternately connected to the respective output terminals through the respective diodes. It is connected. Here, all impedance elements are composed of capacitors having the same capacitance value or reactors having the same inductance value.

The single-phase rectifier circuit according to the present invention includes an AC power supply, at least two diodes connected in series with each other on the output side of the AC power supply, and a DC output terminal between both ends of the series circuit of these diodes. A single-phase rectifier circuit, which includes a connected electrolytic capacitor and supplies DC power to a load connected between the DC output terminals, includes two non-linear impedance circuits, and each first output of the non-linear impedance circuits. The terminals are respectively connected to the positive and negative DC output terminals, the second output terminals of the nonlinear impedance circuit are collectively connected to one end of the AC power supply, and the other end of the AC power supply is connected to the two diodes. It is connected to a series connection point.

In the above single-phase rectifier circuit, a single-phase diode bridge is connected to the output side of the AC power source, one of the AC input terminals is connected to each second output terminal of the nonlinear impedance circuit, and It is preferable to connect the other of the AC input terminals to the other end of the AC power supply.
Furthermore, it is desirable to connect one end of the AC power source to each second output terminal of the nonlinear impedance circuit via an AC reactor.

[0009]

In the nonlinear impedance circuit of the present invention, when the impedance element is a capacitor, the combined capacitance value changes according to the polarity of the current flowing between the output terminals.
When the impedance element is a reactor, the combined inductance value changes according to the polarity of the voltage applied between the output terminals. Thereby, the impedance of the circuit can be changed according to the polarity of the current or the voltage.

In the single-phase rectifier circuit of the present invention, the non-linear impedance circuits are respectively connected between one end of the AC power source and the positive and negative DC output terminals so that the AC input current can flow without any control operation. The flow width is increased so that the current flows in almost the same phase as the power supply voltage, and the power factor on the power supply side can be made approximately 1. At the same time, the harmonic components contained in the AC input current are also reduced, and the current waveform is improved. In particular,
If an AC reactor is added to the output side of the AC power supply, a further waveform improving action can be obtained.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first non-linear impedance circuit of the present invention.
An example is shown. In the figure, the first and second output terminals T _1, T between ₂ and capacitor C ₁ as a capacitive impedance element, a diode D _2, a capacitor C ₂
And are connected in series. Between the output terminal T ₂ (the anode diode D ₂₎ and the second capacitor C ₁ and the connection point diode D _2, the diode D ₁ is connected with the polarity shown. Further, the connection point of the diode D ₂ and the capacitor C ₂ (cathode of the diode D ₂ ) and the first
A diode D ₃ is connected between the output terminal T ₁ and the output terminal T ₁ with the polarity shown. Here, has a capacitance value of the capacitor C _1, C ₂ expressed as the code as C _1, C _2, these capacitance values are the same C ₁ = C ₂ = C.

Next, the operation of this embodiment will be described. In addition, the voltage and the current have the positive direction in the direction of FIG. Now
Assuming that the capacitors C ₁ and C ₂ are both charged to the voltage E, the discharge current i is the path of the terminal T ₂ → the diode D ₁ → the capacitor C ₁ → the terminal T ₁ and the terminal T ₂ → the capacitor C ₂ →
The voltage e flows between the diode D _{3 and the} terminal T ₁ and if the forward voltage drop in the diode is ignored, the terminal voltage e = E. That is, when viewed from the output terminals T ₁ and T ₂ , the capacitors C ₁ and C ₂ are connected in parallel, so that the combined capacitance value is 2C as shown in FIG.

On the contrary, when the current i flows in the negative direction,
The path of the charging current i is terminal T ₁ → capacitor C ₁ → diode D ₂ → capacitor C ₂ → terminal T ₂ and the output terminal T ₁ ,
As seen from T ₂ , the capacitors C ₁ and C ₂ are connected in series, and the combined capacitance value becomes C / 2 as shown in FIG. 2, and the terminal voltage e = 2E. However, in this circuit, since the diodes D ₁ , D ₂ , and D ₃ are connected in series in the forward direction between the output terminals T ₁ and T ₂ , the terminal voltage e must be e ≧ 0 to prevent a short circuit. is necessary.

As described above, according to this embodiment, the output terminal T
_Since the combined capacitance value of the circuit can be changed by changing the polarity of the current i flowing between ₁ and T ₂ , the nonlinear impedance circuit can be easily realized.

FIG. 3 shows a second embodiment of the non-linear impedance circuit, which is provided with capacitors C _{1 to} C ₃ having a three-stage structure in place of the capacitors C ₁ and C ₂ having a two-stage structure in the first embodiment. Is. Note that D _{1 to} D ₆ are diodes. According to this embodiment, according to the same principle as in the first embodiment, as shown in FIG. 4, the combined capacitance value of the circuit is 3C (current i is positive) or C / 3 (current i) depending on the polarity of the current i. i can be changed to a negative polarity).

In each of the above embodiments, generally n
(N is an integer of 2 or more) capacitors are alternately connected in series via (n-1) diodes, and the connection points of the capacitors and the diodes are arranged in order from the _one closest to the _first output terminal T ₁ . The two output terminals T ₂ and the first output terminal T ₁ may be connected to the output terminals T ₂ and T ₁ in this order via diodes. When using n capacitors, the combined capacitance value can be changed between n · C and C / n.

Next, FIGS. 5 and 6 show third and fourth embodiments of the nonlinear impedance circuit. In these embodiments, the impedance elements are replaced with reactors as the electric dual circuits of the first and second embodiments. That is, in the third embodiment of FIG. 5, the capacitors C ₁ and C ₂ in the first embodiment are replaced with reactors L ₁ and L ₂ , and the polarities of the diodes D ₁ and D ₃ are changed. The fourth embodiment of FIG. 6 is based on the third embodiment, and similarly to the second embodiment, the reactors L _{1 to} L ₃ having a three-stage structure.
It is equipped with.

Of these, the basic operation of the third embodiment will be described. In this circuit, the combined inductance value changes according to the polarity of the voltage e applied between the terminals T ₁ and T ₂ . Similarly to the above, assuming that the inductance values of the reactors L ₁ and L ₂ are L ₁ = L ₂ = L, when the voltage e is applied with a positive polarity, the reactors L ₁ and L ₂ are connected in parallel, and thus the combined inductance value is Is L / 2, and when the voltage e is applied with a negative polarity, the reactors L ₁ and L ₂ are connected in series, so the combined inductance value is 2L. Assuming that the current flowing through the reactors L ₁ and L ₂ is a constant value I ₀ , the current i flowing between the terminals T ₁ and T ₂ is i = 2 when e> 0.
When I ₀ and e <0, i = I ₀ . Here, the direction of the current i is constant.

As described above, in the third embodiment, the terminals T ₁ ,
The composite inductance value of the circuit can be changed only by changing the polarity of the voltage e applied between T ₂ and the nonlinear impedance circuit can be easily realized. The above operation is basically the same for the fourth embodiment. Also in these embodiments, generally, n reactors and (n-1) diodes are alternately connected in series between the output terminals T ₁ and T ₂ , and each connection point is a predetermined output terminal T ₂ or T _1. It is possible to obtain a predetermined function and effect by connecting to each of them via a diode. When using n reactors, it is possible to change the combined inductance value between L / n and n · L.

Next, a first embodiment of a single-phase rectifier circuit according to the present invention will be described as an application example of the above-mentioned nonlinear impedance circuit with reference to FIG. This single-phase rectifier circuit expands the flow width of the AC input current of the rectifier circuit by connecting the above-mentioned non-linear impedance circuit to the AC input side of the rectifier circuit, thereby improving the power supply side power factor and input current waveform. It was done.

In FIG. 7, AC is an AC power source (instantaneous value e
= E _m sin ωt), and both ends of the AC reactor La
Is connected to the AC input terminal of the single-phase diode bridge 20 composed of the diodes D _{11 to} D ₁₄ . An electrolytic capacitor C _d and a load LD are connected in parallel with each other at the DC output terminal of the diode bridge 20.

[0022] Further, between the positive electrode and the negative electrode of the connection point of the diodes D _11, D ₁₂ in the diode bridge 20 and the DC output terminal, the non-linear impedance circuit 10, 10 of FIG. 1 described above 'is connected There is. That is,
In each of the nonlinear impedance circuits 10 and 10 ′, each first output terminal T ₁ is connected to the positive electrode and the negative electrode of the DC output terminal,
The second output terminals T ₂ are collectively connected to the diodes D ₁₁ and D ₁₂
Of the AC reactor La (non-power source side terminal of the AC reactor La). The other end of the AC power supply AC is a diode D
It is connected to the connection point of ₁₃ and D ₁₄ .

[0023] In this embodiment, the non-linear impedance circuit 10 and 10 'is constituted by a circuit connected two-stage _{capacitor, C 1, C 2, C} 1', C 2 ' are capacitors, D ₁ to D ₃ , D ₁ ′ to D ₃ ′ represent diodes. Here, the capacitance values of the capacitors C ₁ , C ₂ , C ₁ ′ and C ₂ ′ are all equal C ₁ = C ₂ = C ₁ ′ = C ₂ ′ = C.

Next, the operation of this embodiment will be described. This circuit operates symmetrically for each half cycle of the power supply voltage.
The half cycle in which the power supply voltage e is positive will be described below.
When the power supply voltage e enters into a positive half cycle, the AC input current i _a flows in the path of the AC reactor La → capacitor C ₂ ′ → diode D ₂ ′ → capacitor C ₁ ′ → diode D ₁₄ so that the lower arm is nonlinear. The capacitors C ₂ ′ and C ₁ ′ of the impedance circuit 10 ′ are charged in series. This charging operation is performed until the input voltage becomes maximum for each of the capacitors C ₂ ′ and C ₁ ′ whose combined capacitance value is C / 2 as described above, and the capacitors C ₂ ′ and C ₁ ′ are respectively The voltage is _Em
It is charged until it becomes / 2.

On the other hand, looking at the nonlinear impedance circuit 10 of the upper arm, the capacitors C ₁ and C ₂ are charged up to E _m / 2 in the negative half cycle of the power supply voltage e by the charging operation similar to the above. Therefore, assuming that the voltage of the electrolytic capacitor C _d is E _d in the positive half cycle of the power supply voltage e, the diodes D ₁ , D ₃ , and D ₁₄ become conductive when e = E _d −E _m / 2. Begin to supply current to the DC side.

That is, in this embodiment, as soon as the power supply voltage e enters the positive half cycle, the capacitor C ₁ ′,
A charging current i _a of C ₂ ′ flows, and then e = E _d −E _m / 2
Since the current i _{a in the} same direction as the discharge currents of the capacitors C ₁ and C ₂ continues to flow from the point of becoming, the AC input current i _a
Of the electric current i _a at the zero cross point of the voltage e (n = 0, 1, 2, ...).
Can be drained from. As a result, the power factor on the power supply side can be made approximately 1, and the harmonic components of the current can be suppressed. Further, by adding the AC reactor La, it is possible to obtain a further waveform improving action.

[0027] The diode D _1, D _3, D capacitor C _1, C ₂ of the upper arm is discharged with an electrical connection _14, the power supply voltage positive of each capacitor C ₁ before the end half period of e, C ₂ The diode D ₁₁ becomes conductive when the voltage of V becomes zero. After that, the current i _d is supplied to the DC side through the diodes D ₁₁ and D ₁₄ by the operation of the normal single-phase rectification circuit. Capacitor C ₁ ′,
AC input current i _a as when charging C ₂ ′ or C ₁ , C ₂
Is not supplied to the side of the load LD, the discharge current due to the charge accumulated in the electrolytic capacitor C _d is supplied to the load LD, so that the continuity of the load current i _d can be maintained.

In the above embodiment, the diodes D ₁₁ and D ₁₂ in the diode bridge 20 are the diodes D ₁ to D _1, respectively.
Because it is connected in parallel to the D ₃ and D ₁ '~D _3', by omitting the diode D _11, D ₁₂ diodes D ₁ ~
The function can be replaced by D ₃ and D ₁ ′ to D ₃ ′, which can reduce the number of parts. However, considering the voltage drop due to each of the three diodes, the number of elements increases, but the diode D ₁₁ ,
It can be said that it is preferable to use D ₁₂ as it is.

The inventor has set the effective value of the power supply voltage e to 100 [V] and the AC reactor La to 4.
3 [mH], capacitors C ₁ , C ₂ , C ₁ ′ and C ₂ ′ are 15
7 [μF], electrolytic capacitor C _d is 4000 [μF],
A simulation was performed with the load current i _{d set} to 10 [A], and the effect of improving the power factor and the current waveform was confirmed. Figure 8 is a waveform of the power supply voltage e, Fig. 9 shows respective waveforms of the AC input current i _a, from these figures, the AC input current i _a
It can be seen that the waveform of is almost sinusoidal and the power factor is improved. Further, FIG. 10 is a frequency spectrum of the AC input current, and the numeral in the graph is the amplitude [A] of each harmonic current. From this figure, the third harmonic, the fifth
It is clear that the proportion of harmonic components such as harmonics is greatly reduced.

Further, FIG. 11 shows the power factor, the DC output voltage E _d , of the single-phase rectifier circuit of the embodiment of FIG. 7 and the conventional single-phase rectifier circuit having no nonlinear impedance circuits 10 and 10 '.
An AC input current load characteristics were compared respectively (effective value) I _a view, the present invention (2), is shown prior techniques as (1). As is clear from this figure, in the present invention, the input power factor is 0.981 at the maximum and the efficiency is 97%, and power factor improvement and efficiency improvement are achieved.

FIG. 12 is a comparison result between the present invention and the prior art by the same method as FIG. 11, and shows the fundamental wave I ₁ and the third harmonic wave I ₁ included in the AC input current (effective value) I _{a. 3} ,
The current amplitude of the fifth harmonic I ₅ is shown. According to the present invention, for both the third harmonic I ₃ and the fifth harmonic I ₅ ,
IEC (International Electrotechnical Commi)
ssion) harmonic regulation value (shown by the broken line in the figure).

FIG. 13 shows a second embodiment of the single-phase rectifier circuit. This embodiment shows a nonlinear impedance circuit 1
0A and 10A 'are composed of the two-stage inductances L ₁ , L ₂ , L ₁ ′ and L ₂ ′ shown in FIG. 5, and the diodes D ₁₁ and D ₁₂ of the diode bridge 20 in FIG. It is omitted. The operation of this embodiment is basically the same as that of the embodiment of FIG.
As is clear from the waveform diagram of FIG. 14, in this embodiment, when e <E _d (e _L <0), i = I _{0 When} e> E _d (e _L > 0), i = 2I ₀ Becomes Where e _L is the voltage across each inductance,
I ₀ is a current flowing through each inductance. Also in this embodiment, the power factor on the power supply side can be made approximately 1,
Moreover, the AC input current waveform can be improved.

[0033]

As described above, according to the nonlinear impedance circuit of the present invention, when the impedance element is a capacitor, the combined capacitance value changes according to the polarity of the current flowing between the output terminals, and the impedance When the element is a reactor, the combined inductance value changes according to the polarity of the voltage applied between the output terminals. As a result, a non-linear circuit in which the impedance of the circuit changes according to the polarity of current or voltage can be realized with a simple configuration, and can be applied to various circuits including a single-phase rectifier circuit.

Further, according to the single-phase rectifier circuit of the present invention, the non-linear impedance circuit is connected between one end of the AC power source and the positive and negative DC output terminals of the rectifier circuit, so that the AC input current flows through. The width is increased and the AC input current flows in substantially the same phase as the power supply voltage, and the power factor on the power supply side can be made approximately 1. At the same time, the harmonic components contained in the AC input current are also reduced, and the current waveform is improved. These actions and effects are realized without using a power converter such as a chopper or an inverter as in the past and without requiring any control operation, so that it is possible to reduce the size and weight of the entire circuit and reduce the cost. And switching noise will not occur.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of a nonlinear impedance circuit according to the present invention.

FIG. 2 is an operation explanatory diagram of the embodiment of FIG.

FIG. 3 is a circuit diagram showing a second embodiment of a nonlinear impedance circuit.

FIG. 4 is an operation explanatory diagram of the embodiment in FIG.

FIG. 5 is a circuit diagram showing a third embodiment of a nonlinear impedance circuit.

FIG. 6 is a circuit diagram showing a fourth embodiment of a nonlinear impedance circuit.

FIG. 7 is a circuit diagram showing a first embodiment of a single-phase rectifier circuit of the present invention.

FIG. 8 is a waveform diagram of a power supply voltage in the embodiment of FIG.

9 is a waveform diagram of an AC input current in the embodiment of FIG.

10 is a frequency spectrum of an AC input current in the embodiment of FIG.

FIG. 11 is a diagram for explaining the effect of the embodiment of FIG.

FIG. 12 is a diagram for explaining the effect of the embodiment of FIG.

FIG. 13 is a circuit diagram showing a second embodiment of the single-phase rectifier circuit.

FIG. 14 is a voltage and current waveform diagram of each part in the embodiment of FIG.

[Explanation of symbols]

T _1, T ₂ output terminals _{C 1 ~C 3, C 1 '} ~C 2' capacitor _{L 1 ~L 3, L 1 '} ~L 2' reactor _{D 1 ~D 6, D 1 '} ~D 3', D _{11 to} D ₁₄ Diode C _d Electrolytic capacitor AC AC power supply La AC reactor LD load 10, 10 ', 10A, 10A' Non-linear impedance circuit 20 Diode bridge

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[Procedure amendment]

[Submission date] September 11, 1992

[Procedure Amendment 1]

[Document name to be corrected] Drawing

[Name of item to be corrected] Fig. 13

[Correction method] Change

[Correction content]

[Fig. 13]

Claims (6)

[Claims] 1. Between the first and second output terminals, n (n is an integer of 2 or more) impedance elements and (n-1) impedance elements, all of which are capacitive impedance elements or inductive impedance elements. Diodes are alternately connected in series, and the second output terminal and the first output terminal are arranged in order from the one closest to the first output terminal among the connection points of each impedance element and the diode, through the respective diodes. A non-linear impedance circuit characterized by being connected to each output terminal alternately with. 2. The nonlinear impedance circuit according to claim 1, wherein all the impedance elements are capacitors having the same capacitance value. 3. The nonlinear impedance circuit according to claim 1, wherein all the impedance elements are reactors having the same inductance value. 4. An alternating current power supply, at least two diodes serially connected to each other on the output side of the alternating current power supply, and an electrolytic capacitor connected between direct current output terminals of both ends of the series circuit of the diodes, A single-phase rectifier circuit for supplying DC power to a load connected between output terminals, comprising two nonlinear impedance circuits according to claim 1, 2 or 3, wherein each first output terminal of these nonlinear impedance circuits is provided. The positive and negative DC output terminals are respectively connected, and the second output terminals of the nonlinear impedance circuit are collectively connected to one end of the AC power supply, and
A single-phase rectifier circuit characterized in that the other end of the AC power source is connected to a series connection point of the two diodes. 5. A single-phase diode bridge is provided on the output side of the AC power source, one of the AC input terminals is connected to each second output terminal of the nonlinear impedance circuit, and the other of the AC input terminals is connected to the AC The single-phase rectifier circuit according to claim 4, which is connected to the other end of the power supply. 6. The single-phase rectifier circuit according to claim 4, wherein one end of the AC power supply is connected to each second output terminal of the non-linear impedance circuit via an AC reactor.