JP2002026779A - Ac/dc separate circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an AC/DC separation circuit that can separate an AC voltage from a DC voltage, without the need for using a large-sized inductor and moreover has a high input impedance. SOLUTION: The AC/DC separate circuit 4 separates an input voltage, consisting of a DC voltage Vdc on which an AC voltage Vac is superimposed into a DC voltage and an AC voltage. The AC voltage Vac passes through a capacitor C1 and enters a noninverting amplifier A1, having a high input impedance, and the AC voltage Vac1 is extracted therefrom. The AC voltages Vac, Vac1 applied across an inductor L1, have the same amplitude and the same phase to make the inductance equivalently infinite. An inverting amplifier A2 inverts the phase of the AC voltage Vac1 and applies the resulting voltage to one end of a series circuit consisting of inductors L2, L3. Thus, the AC component is cancelled from the voltage applied across the series circuit, consisting of the inductors L2, L3, and a DC voltage Vdc1 is extracted from the connecting point of the inductors L2, L3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC / DC separation circuit for separating a DC voltage and an AC voltage from a voltage obtained by superimposing an AC signal voltage on a DC power supply voltage.

[0002]

2. Description of the Related Art Conventionally, a plurality of terminals are connected via a two-wire signal line, data is exchanged between the terminals, and one of the terminals is used as a power supply terminal and the remaining terminals are connected to each other. A data transmission system that supplies power from a power supply terminal to a power receiving terminal has been proposed as a power receiving terminal. As this type of data transmission system, there is a multiplex transmission system for transmitting data by time-division multiplexing. In this type of multiplex transmission system, an AC signal voltage modulated by data is superimposed on a DC power supply voltage at a power supply terminal. 2. Description of the Related Art There has been known a power receiving terminal that simultaneously performs data transmission and power supply by separating a DC power supply voltage and an AC signal voltage. In a data transmission system having such a configuration, an AC / DC separation circuit for separating a DC voltage and an AC voltage is required in a power receiving terminal.

[0003] That is, as shown in FIG.
, An AC voltage Vac as a signal component is superimposed on a DC voltage Vdc as a power supply component and transmitted to the signal line 3, and the power receiving terminal 1 uses an AC / DC separation circuit 4 to generate a DC voltage Vdc1 and an AC voltage Vac1. Is separated, the DC voltage Vdc1 is supplied to the DC load Zdc, and the AC voltage Vac1 is supplied to the AC load Zac. As the simplest circuit configuration as an AC / DC separation circuit, a circuit configuration using one capacitor C and one inductor L can be considered. Since the inductor L has a low impedance with respect to the DC component and a high impedance with respect to the AC component, the DC voltage Vd can be obtained by inserting the inductor L into the path from the signal line 3 to the DC load Zdc.
Since the capacitor C has a high impedance with respect to the DC component and a low impedance with respect to the AC component, the AC voltage Vac1 is extracted by inserting the capacitor C into the path from the signal line 3 to the AC load Zac. It is. In FIG. 8, the AC load Zac means a signal receiving circuit provided in the power receiving terminal 1, and the DC load Zac
dc means a power supply circuit for supplying power required for operation of the power receiving terminal 1.

[0004]

By the way, if the frequency of the AC voltage Vac, which is a signal component, is sufficiently high, the AC / DC separation circuit 4 shown in FIG. Can be used to separate the DC voltage Vdc1 from the AC voltage Vac1, but when the frequency of the AC voltage Vac is relatively low, the inductor L having a large inductance is used.
And a capacitor C having a large capacitance are required.

Further, in the multiplex transmission system having the above-described configuration, a plurality of power receiving terminals 1 are connected to the two-wire signal line 3, so that the input impedance of each power receiving terminal 1 is set via the signal line 3. In order to transmit the AC voltage, which is a signal component, to a distant place and to increase the allowable number of power receiving terminals 1 connectable to the signal line 3, the power receiving terminals 1 for the AC voltage are connected in parallel. Must be as high as possible. In other words, in the AC / DC separation circuit 4 having the configuration shown in FIG. 8, an inductor L having a large inductance and a capacitor C having a large capacitance are required in order to increase the input impedance.

In general, the larger the inductance L, the larger the inductance, and the larger the capacitance of the capacitor C, the larger the capacitance.
Is formed by winding a copper wire around an iron core, so that not only the size is increased but also the mass is significantly increased with the increase in size. As a result, when transmitting a relatively low-frequency AC voltage as a signal component, there is a problem that the size and the mass of the power receiving terminal 1 cannot be avoided. Furthermore, if the inductance of the inductor L increases, the number of turns of the winding also increases, so that the DC resistance due to the winding of the inductor L increases, and the power loss in the inductor L increases. Another problem is that the efficiency is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an AC / DC separation circuit capable of separating an AC voltage and a DC voltage without using a large inductor and having a high input impedance. To provide.

[0008]

According to a first aspect of the present invention, an input voltage in which an AC voltage is superimposed on a DC voltage is separated into a DC voltage and an AC voltage, and the separated AC voltage is supplied to an AC load. And an AC / DC separation circuit for applying a separated DC voltage to a DC load, the AC / DC separation circuit separating an AC voltage from the input voltage and applying the separated AC voltage to the AC load through a buffer having a high input impedance. A DC voltage extracting unit for canceling the AC voltage included in the input voltage by using the extracted AC voltage to separate the DC voltage included in the input voltage and applying the separated DC voltage to the DC load.

According to a second aspect of the present invention, in the first aspect of the present invention, the AC voltage extracting section includes a first capacitor for extracting an AC voltage from the input voltage, and an AC voltage extracted by the first capacitor for one. A first non-inverting amplifier as the buffer for amplifying by a double gain, and the input voltage AC-coupled to the output terminal of the first non-inverting amplifier and the AC voltage output from the first non-inverting amplifier, And a first inductor applied to one end.

A third aspect of the present invention is the second aspect of the present invention, wherein the second non-inverting amplifier is inserted between the output terminal of the first non-inverting amplifier and the first inductor and has a gain of about 1 and can be adjusted.
Are added.

According to a fourth aspect of the present invention, in the first to third aspects of the present invention, the DC voltage extracting section includes: a second inductor to which a voltage corresponding to the input voltage is applied to one end; An inverting amplifier that generates an AC voltage having the same amplitude and opposite phase as the AC voltage applied to the one end of the second inductor using the AC voltage output from the extracting unit;
A third inductor having the same inductance as the second inductor is inserted between the output terminal of the inverting amplifier and the other end of the second inductor, and is taken out from a connection point between the second inductor and the third inductor. A DC voltage is applied to the DC load.

According to a fifth aspect of the present invention, in the first to third aspects of the present invention, in the DC voltage extracting section, a voltage corresponding to the input voltage is applied to one end and the other end is connected to the DC load. The first winding and a second winding to which an AC voltage corresponding to the AC voltage output from the AC voltage output unit is applied are formed by a transformer that is electromagnetically coupled, and the AC voltage applied to the second winding The AC voltage induced in the first winding has the same amplitude as the AC voltage applied to the one end of the first winding of the transformer, has a polarity for canceling the AC voltage, and has a polarity from the other end of the first winding. A DC voltage is applied to the DC load.

According to a sixth aspect of the present invention, in the fourth or fifth aspect of the present invention, the gain is inserted between the output terminal of the AC voltage extracting section and the one end of the second winding of the transformer, and the gain is about 1. And a third non-inverting amplifier which can be adjusted by the above-mentioned method.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) An AC / DC separation circuit 4 according to the present embodiment has the configuration shown in FIG. 1, and is one of the two-wire signal lines 3. Are commonly connected to one of two input terminals of an AC load Zac and a DC load Zdc. An inductor is inserted between the other line of the signal line 3 and the other input terminal of the DC load Zdc, as in the conventional configuration. However, in this embodiment, a series circuit of two inductors L1 and L2 is used as an inductor inserted between the signal line 3 and the DC load Zdc.

On the other hand, the other line of the signal line 3 and the AC load Z
A capacitor C1 and a non-inverting amplifier A1 having a gain of 1 are inserted between the AC and AC, so that an AC voltage, which is a signal component separated through the capacitor C1, is applied to the AC load Zac through the non-inverting amplifier A1. Is configured. That is, the DC voltage as a power supply component of the input voltage to the AC / DC separation circuit 4 applied to the signal line 3 by the power supply terminal 2 is blocked by the capacitor C1, so that the non-inverting amplifier A1 has the signal component. Only a certain AC voltage is input, and the AC voltage V output from the non-inverting amplifier A1 is input.
ac1 is applied to the AC load Zac.

In this embodiment, the capacitor C2 is connected between the connection point between the two inductors L1 and L2 and the output terminal of the non-inverting amplifier A1, and the connection point between the inductors L1 and L2 is connected to the non-inverting amplifier. The output terminal of the amplifier A1 is AC-coupled. The output of the non-inverting amplifier A1 is input to the inverting amplifier A2 having a gain of 1, and the output of the inverting amplifier A2 is applied to one end of the inductor L2 on the DC load Zdc side via the capacitor C3 and the inductor L3.

Next, the operation of the AC / DC separation circuit 4 in this embodiment will be described with reference to FIG. FIG.
(A) to (e) are voltage waveforms at portions corresponding to points a to e shown in FIG. 1, respectively. The voltage applied to the signal line 3 is changed from the DC voltage Vdc to the AC voltage Va as shown in FIG.
c is superimposed and the capacitor C1 blocks the DC voltage and inputs only the AC voltage to the non-inverting amplifier A1, so the AC voltage Vac1 shown in FIG. 2B is output from the non-inverting amplifier A1. You. That is, the AC voltage Vac1
Is applied to the AC load Zac. Here, the phase of the AC voltage Vac1 output from the non-inverting amplifier A1 is the same as the phase of the AC voltage Vac which is a signal component of the voltage applied to the signal line 3. A non-inverting amplifier A
1 has a gain of 1, so the AC voltage Vac and the AC voltage Va
The amplitude is ideally equal to c1.

A point c, which is a connection point between the inductors L1 and L2, is connected via a capacitor C2 to a non-inverting amplifier A1.
, The potential at the point c becomes the sum of the AC voltage Vac1 output from the non-inverting amplifier A1 and the voltage across the capacitor C2. That is, FIG.
As shown in (c), the DC voltage Vdc2 is replaced with the AC voltage Vac2.
And the phase of the AC voltage Vac2 is the AC voltage Vac of the voltage applied to the signal line 3.
And the voltage between both ends of the inductor L1 is changed to a DC voltage (Vdc-Vdc2) and an AC voltage (Vac-Vac
2) is a superimposed voltage. From this, the AC voltage V
If ac2 is equal to the AC voltage Vac, the inductor L1
It can be seen that the AC component can be removed from the voltage between both ends. Under this condition, no AC current flows through the inductor L1, and the impedance of the inductor L1 can be regarded as equivalently infinite with respect to the AC voltage Vac as a signal component. Further, the DC voltage (Vdc-Vdc2) applied between both ends of the inductor L1 becomes a voltage drop due to the DC resistance of the winding of the inductor L1. As is clear from the above description, an AC voltage extracting unit is configured by the capacitors C1 and C2, the non-inverting amplifier A1, and the inductor L1.

On the other hand, the AC voltage Vac3 output from the inverting amplifier A2 is, as shown in FIG.
1 has an opposite phase to the phase of the AC voltage Vac1 output. Here, since the gain of the inverting amplifier A2 is 1, the AC voltage Vac3 and the AC voltage Vac1 ideally have the same amplitude. This AC voltage Vac3 is
3 is applied to one end of the inductor L3 via
The AC component of the potential at the point e, which is the connection point between the two inductors L2 and L3, becomes substantially zero because the AC voltage Vac2 and the AC voltage Vac3 cancel each other. Since the AC voltage Vac2 and the AC voltage Vac3 ideally have the same amplitude, the AC component of the potential at the point e can be made zero by setting the impedances of the inductors L2 and L3 equal. . As a result, the potential at the point e shown in FIG.
As shown in (e), only the DC voltage Vdc1 is applied to the DC load Z.
dc. That is, the inductor L
2, L3, capacitor C3, and inverting amplifier circuit A2 constitute a DC voltage extracting unit. Here, the inductor L2
DC voltage (Vdc2-Vdc1) applied between both ends of
Is a voltage drop due to the DC resistance of the winding of the inductor L2. By providing the capacitor C2, the inflow of DC current from the point c to the non-inverting amplifier A1 is prevented, and by providing the capacitor C3, the inflow of DC current from the point e to the inverting amplifier A2 is prevented. Have been.

As described above, by making the AC components of the voltage applied to both ends of the inductor L1 have the same amplitude and the same phase, the inductance of the inductor L1 can be made equivalently infinite. In this state,
The input impedance of the DC separation circuit 4 is the non-inverting amplifier A
Since the input impedance is determined by the input impedance of 1, the non-inverting amplifier A1 having a high input impedance may be used. For example, the input stage is MOSF which is a voltage control element.
If the non-inverting amplifier A1 composed of ET is used, the input impedance of the non-inverting amplifier A1 can be increased, and as a result, the input impedance of the AC / DC separation circuit 4 can be increased. Further, the AC component of the voltage applied to both ends of the series circuit of the inductor L2 and the inductor L3 is set to the same phase, and the AC component is set to zero at the connection point between the two inductors L2 and L3. Only the removed DC voltage Vdc1 can be applied.

As is apparent from the above-described operation, although the present embodiment requires three inductors L1 to L3, it is not necessary to attenuate the AC component by the impedance of each of the inductors L1 to L3. L1 to L3 each having a small inductance can be used, and as a result, small and lightweight inductors L1 to L3 can be used. In addition, inductor L
1 and L2 have a small inductance, so that the number of turns of the windings can be reduced, and a voltage drop due to the inductors L1 and L2 is reduced. As a result, the power efficiency of the power receiving terminal 1 can be increased as compared with the conventional configuration. Become. In other words,
Since a DC current flows through the inductors L1 and L2, it is desirable to use an inductor having a DC resistance as small as possible.

Theoretically, the gain of each of the non-inverting amplifier A1 and the inverting amplifier A2 may be one. However, in practice, the non-inverting amplifier A1 and the inverting amplifier A2 need The gain of the amplifier A1 and the gain of the inverting amplifier A2 can be adjusted around one time. That is, the AC voltage Va of the voltages applied to both ends of the inductor L1.
By adjusting the gain of the non-inverting amplifier A1 so that c and Vac2 become equal, it becomes possible to increase the input impedance of the AC / DC separation circuit 4. Also,
By adjusting the gain of the inverting amplifier A2 so that the amplitudes of the AC voltages Vac2 and Vac3 among the voltages applied to both ends of the series circuit of the inductors L2 and L3 are equal, the output from the AC / DC separation circuit 4 is obtained. DC voltage Va
The AC component can be removed so that the AC voltage is not included in c1. Note that a phase compensation circuit is added to the non-inverting amplifier A1 and the inverting amplifier A2 as necessary.

(Second Embodiment) This embodiment is similar to FIG.
As shown in FIG. 7, a non-inverting amplifier A3 inserted between the output terminal of the non-inverting amplifier A1 and the capacitor C2 is added to the first embodiment shown in FIG. Other configurations are the same as those of the first embodiment. Non-inverting amplifier A
3 has a gain adjustable near 1 and a non-inverting amplifier A
3 is adjustable.

In the configuration of the first embodiment, the non-inverting amplifier A1 adjusts the voltage applied to both ends of the inductor L1 to increase the input impedance of the AC / DC separation circuit 4, and the DC load is adjusted. The adjustment for removing the AC component from the DC voltage Vdc1 applied to Zdc is performed by the inverting amplifier A2. However, adjusting the non-inverting amplifier A1 affects the output of the inverting amplifier A2. On the other hand, in the configuration of the present embodiment, since the adjustment for increasing the input impedance of the AC / DC separation circuit 4 can be performed by the non-inverting amplifier A3, the AC component from the DC voltage Vdc1 applied to the DC load Zdc is reduced. The adjustment of the inverting amplifier A2 for eliminating the noise can be performed independently without affecting each other, and the adjustment operation is facilitated. Compared with the first embodiment, the configuration of the present embodiment increases the number of components due to the addition of the non-inverting amplifier A3. However, the degree of freedom of adjustment is high, and fine adjustment is possible. This is effective when a higher input impedance is required than in the first embodiment.

(Third Embodiment) The AC / DC separation circuit 4 in the present embodiment has the configuration shown in FIG.
One of the two-wire signal lines 3 has an AC load Zac.
And one of two input terminals of DC load Zdc. Further, the other line of the signal line 3 and the DC load Zd
An inductor is inserted between the input terminal c and the other input terminal as in the conventional configuration. However, in the present embodiment, a series circuit of the inductor L1 and the first winding n1 of the transformer T is used as an inductor inserted between the signal line 3 and the DC load Zdc. As the transformer T, a two-winding type transformer having a turns ratio of 1: 1 is used.

On the other hand, the other line of the signal line 3 and the AC load Z
A capacitor C1 and a non-inverting amplifier A1 having a gain of 1 are inserted between the AC and AC, so that an AC voltage, which is a signal component separated through the capacitor C1, is applied to the AC load Zac through the non-inverting amplifier A1. Is configured. That is, the DC voltage as a power supply component of the input voltage to the AC / DC separation circuit 4 applied to the signal line 3 by the power supply terminal 2 is blocked by the capacitor C1, so that the non-inverting amplifier A1 has the signal component. Only a certain AC voltage is input, and the AC voltage V output from the non-inverting amplifier A1 is input.
ac1 is applied to the AC load Zac.

In this embodiment, one end of a capacitor C2 is connected to the connection point between the inductor L1 and the first winding n1 of the transformer T, and the other end of the capacitor C2 is connected to the non-inverting amplifier A1.
And the connection point between the inductor L1 and the first winding n1 of the transformer T and the output terminal of the non-inverting amplifier A1 are AC-coupled. The non-inverting amplifier A1
Is connected to one end of a second winding n2 of a transformer T via a capacitor C4, and the other end of the second winding n2 of the transformer T is commonly connected to the one line of the signal line 3. When a voltage is applied to the first winding n1 and the second winding n2 of the transformer T so that the capacitor C4 has a positive polarity, the inductor L1 side of the first winding n1 has a positive polarity. The polarity is such that the voltage is induced so that

Next, the operation of the AC / DC separation circuit 4 in the present embodiment will be described with reference to FIG. FIG.
(A) to (d) and (f) represent the points a to
It is a voltage waveform of a part corresponding to d and f. FIG.
(E) is a voltage across the first winding n1 of the transformer T1. The voltage applied to the signal line 3 is obtained by superimposing the AC voltage Vac on the DC voltage Vdc as shown in FIG. 5A. The DC voltage is blocked by the capacitor C1 and only the AC voltage is supplied to the non-inverting amplifier A1. Input, the non-inverting amplifier A
1 outputs an AC voltage Vac1 shown in FIG. That is, the AC voltage Vac1 is applied to the AC load Zac. The AC voltage Vac1 output from the non-inverting amplifier A1 has the same phase as the AC voltage Vac, which is a signal component of the voltage applied to the signal line 3.
Also, since the gain of the non-inverting amplifier A1 is 1, the AC voltage Vac1 and the AC voltage Vac ideally have the same amplitude.

The point c, which is the connection point between the inductor L1 and the first winding n1 of the transformer T, is connected to the output terminal of the non-inverting amplifier A1 via the capacitor C2.
The potential at the point c is the sum of the AC voltage Vac1 output from the non-inverting amplifier A1 and the voltage across the capacitor C2. That is, as shown in FIG. 5C, the AC voltage Vac2 is a voltage obtained by superimposing the AC voltage Vac2 on the DC voltage Vdc2, and the phase of the AC voltage Vac2 is the same as that of the AC voltage Vac among the voltages applied to the signal line 3. And the voltage between both ends of the inductor L1 is changed to the DC voltage (Vdc−Vdc2) by the AC voltage (V
ac-Vac2). From this, if the AC voltage Vac2 is equal to the AC voltage Vac,
It can be seen that the AC component can be removed from the voltage between both ends of the inductor L1. Under this condition, no AC current flows through the inductor L1, and the AC voltage Vac
, The impedance of the inductor L1 can be regarded as equivalently infinite. In addition, the inductor L1
DC voltage (Vdc-Vdc2) applied between both ends of
Is a voltage drop due to the DC resistance of the winding of the inductor L1. As is clear from the above description, the capacitor C
1, C2, the non-inverting amplifier A1, and the inductor L1 constitute an AC voltage extracting unit.

On the other hand, the AC voltage Vac3 applied to the point d through the capacitor C4 is applied to the second winding n2 of the transformer T.
As shown in FIG. 5D, the output voltage Vac1 of the non-inverting amplifier A1 is AC-coupled via a capacitor C4. Therefore, an AC voltage Vac4 having an amplitude and a phase equal to the AC voltage Vac3 as shown in FIG. 5E is induced between both ends of the first winding n1 of the transformer T.
As a result, the potential at the point f, which is one end of the first winding n1 of the transformer T1 on the DC load Zdc side, becomes the voltage Vd at the connection point between the inductor L1 and the transformer T as shown in FIG.
The voltage is obtained by subtracting the AC voltage Vac4 induced in the first winding n1 of the transformer T from c2 + Vac2. Here, since the AC voltage Vac2 and the AC voltage Vac4 are ideally of the same amplitude and the same phase, the DC voltage Vd
c2 only appears, and the DC load Vdc is applied to the DC load Zdc.
Only will be given. The first of the transformer T
DC voltage (Vdc2-V) applied between both ends of the winding n1
dc1) is a voltage drop due to the DC resistance of the first winding n1 of the transformer T. That is, the transformer T and the capacitor C
4 constitutes a DC voltage extracting unit. The capacitor C4 connected to the second winding n2 of the transformer T is not indispensable in the present embodiment, but if the capacitor C4 is provided, the output of the non-inverting amplifier A1 such as offset and drift of the non-inverting amplifier A1 is provided. Even if a DC component is included due to the influence, it is possible to prevent the DC component from flowing to the second winding n2 of the transformer T.

As described above, in the present embodiment, the AC component of the voltage applied to both ends of the inductor L1 has the same amplitude and the same phase, so that the inductance of the inductor L1 can be made equivalently infinite. it can. In this state, since the input impedance of the AC / DC separation circuit 4 is determined by the input impedance of the non-inverting amplifier A1, a high input impedance may be used as the non-inverting amplifier A1. For example, if the non-inverting amplifier A1 in which the input stage is constituted by a MOSFET which is a voltage control element is used, the input impedance of the non-inverting amplifier A1 can be increased, and as a result, the input impedance of the AC / DC separation circuit 4 can be increased. . A DC load Zdc is connected to one end of the inductor L1 via a first winding n1 of the transformer T, and an AC voltage Vac corresponding to the output voltage of the non-inverting amplifier A1 is connected to the second winding n2 of the transformer T.
3, the AC voltage Vac4 that cancels the AC voltage Vac2 included in the potential of the connection point between the inductor L1 and the first winding n1 of the transformer T is induced, so that the first winding n1 of the transformer T is generated. Can apply only the DC voltage Vdc1 from which the AC component has been removed to the DC load Zdc connected to one end of the DC load.

As is apparent from the above-described operation, the present embodiment requires the inductor L1 and the transformer T, but it is not necessary to attenuate the AC component by the impedance of the inductor L1 itself or the impedance of the transformer T itself. As the inductor L1 and the transformer T, those having small inductances can be used, and as a result, the small and lightweight inductor L1 and the transformer T can be used. Further, since the inductance of the inductor L1 and the transformer T is small, the number of turns of the windings can be reduced, and the voltage drop due to the inductor L1 and the transformer T is reduced. As a result, the power efficiency of the power receiving terminal 1 is improved as compared with the conventional configuration. It is possible to increase. In other words, since a DC current flows through the inductor L1 and the transformer T, it is desirable to use a winding having a DC resistance as small as possible.

Theoretically, the gain of the non-inverting amplifier A1 only needs to be one time. However, in practice, the gain of the non-inverting amplifier A1 is compensated for to compensate for the loss inside the AC / DC separation circuit 4. Is adjustable near 1x. That is, the input impedance of the AC / DC separation circuit 4 can be increased by adjusting the gain of the non-inverting amplifier A1 so that the AC voltages Vac and Vac2 among the voltages applied to both ends of the inductor L1 become equal. Will be possible. Note that a phase compensation circuit is added to the non-inverting amplifier A1 as necessary.

(Fourth Embodiment) This embodiment is different from FIG.
As shown in FIG. 7, a non-inverting amplifier A5 inserted between the output terminal of the non-inverting amplifier A1 and the capacitor C4 is added to the third embodiment shown in FIG. Other configurations are the same as those of the third embodiment. Non-inverting amplifier A
5 is a non-inverting amplifier A whose gain is adjustable near 1
5 is adjustable.

In the configuration of the third embodiment, the non-inverting amplifier A1 adjusts the voltage applied to both ends of the inductor L1 to increase the input impedance of the AC / DC separation circuit 4. When the non-inverting amplifier A1 is adjusted, the AC voltage V applied to the second winding n2 of the transformer T is adjusted.
It will affect ac3. On the other hand, in the configuration of the present embodiment, the adjustment for increasing the input impedance of the AC / DC separation circuit 4 is performed by the non-inverting amplifier A1,
Since the adjustment of the voltage applied to the second winding n2 of the transformer T for removing the AC component from the DC voltage Vdc1 applied to the DC load Zdc is adjusted by the non-inverting amplifier A5, the non-inverting amplifier is adjusted after the adjustment of the non-inverting amplifier A1. By adjusting A5, it is possible to remove the influence of the adjustment of the non-inverting amplifier A1 and adjust the voltage applied to the second winding n2 of the transformer T. As a result, the adjustment operation becomes easier. That is, in the configuration of the present embodiment, the number of components increases due to the addition of the non-inverting amplifier A5 as compared with the third embodiment, but the degree of freedom of adjustment is increased and fine adjustment is possible. From the above, when compared with the third embodiment, the DC load Z
The accuracy of separating and extracting the DC voltage Vdc1 applied to dc can be increased. In the present embodiment, the capacitor C4 is used to prevent a DC component generated by offset and drift of the non-inverting amplifiers A1 and A5 from flowing to the second winding n2 of the transformer T, but the capacitor C4 is essential. That is not to say. Other configurations and operations are the same as those of the third embodiment. The same effect can be obtained by changing the combination of the polarities of the two windings of the transformer T and using the one with the reference numeral A5 as an inverting amplifier.

(Fifth Embodiment) This embodiment is similar to FIG.
As shown in FIG. 7, a non-inverting amplifier A3 inserted between the output terminal of the non-inverting amplifier A1 and the capacitor C2 is added to the fourth embodiment shown in FIG. Other configurations are the same as those of the fourth embodiment. Non-inverting amplifier A
3 has a gain adjustable near 1 and a non-inverting amplifier A
3 is adjustable.

In the configuration of the fourth embodiment, the non-inverting amplifier A1 adjusts the voltage applied to both ends of the inductor L1 to increase the input impedance of the AC / DC separation circuit 4, and the DC load is adjusted. Although the adjustment for removing the AC component from the DC voltage Vdc1 applied to Zdc is performed by the non-inverting amplifier A5, the adjustment of the non-inverting amplifier A1 affects the output of the non-inverting amplifier A5. On the other hand, in the configuration of the present embodiment, since the adjustment for increasing the input impedance of the AC / DC separation circuit 4 can be performed by the non-inverting amplifier A3, the AC component from the DC voltage Vdc1 applied to the DC load Zdc is reduced. The adjustment of the non-inverting amplifier A5 for eliminating the noise can be performed independently without affecting each other, thereby facilitating the adjustment operation. Compared with the fourth embodiment, the configuration of the present embodiment increases the number of components due to the addition of the non-inverting amplifier A3. However, since the degree of freedom of adjustment is high, fine adjustment is possible. This is effective when a higher input impedance is required than in the fourth embodiment.

[0038]

According to the first aspect of the present invention, an input voltage in which an AC voltage is superimposed on a DC voltage is received and separated into a DC voltage and an AC voltage. An AC / DC separation circuit for applying a DC voltage to a DC load, wherein the AC voltage is separated from the input voltage and is applied to the AC load through a buffer having a high input impedance. And a DC voltage extractor that cancels the AC voltage included in the input voltage to separate the DC voltage included in the input voltage and applies the separated DC voltage to a DC load.The DC voltage extractor includes an AC voltage extractor. The DC voltage included in the input voltage is extracted by canceling the AC voltage included in the input voltage using the AC voltage extracted by the extraction unit, This configuration does not use a inductor to extract DC voltage, so there is no need to use a large inductor, and it can be applied without changing circuit constants even when the frequency of AC voltage included in the input voltage is relatively low. become. That is, the DC voltage can be separated regardless of the frequency of the AC voltage included in the input voltage. Further, the input impedance with respect to the AC voltage can be secured by the input impedance of the amplifier, and a high input impedance can be secured by using an amplifier having a high input impedance.

According to a second aspect of the present invention, in the first aspect of the present invention, the AC voltage extracting section includes a first capacitor for extracting an AC voltage from the input voltage and an AC voltage extracted by the first capacitor for one. A first non-inverting amplifier as the buffer for amplifying by a double gain, and the input voltage AC-coupled to the output terminal of the first non-inverting amplifier and the AC voltage output from the first non-inverting amplifier, And an AC voltage output from the first non-inverting amplifier is applied to the other end of the first inductor to which an input voltage is applied to one end. 1
Since the AC voltage applied to both ends of the inductor has the same phase and the same amplitude, and no AC current flows through the first inductor, the inductance of the first inductor can be made equivalently infinite. That is, it is possible to secure a high input impedance with respect to the AC voltage. In addition, since the inductance of the first inductor is not used to increase the input impedance of the AC voltage extractor, a small inductor having a relatively small inductance can be used as the first inductor, and the first inductor can be reduced in size and weight. An AC voltage extracting section having high input impedance can be configured using the inductor.

According to a third aspect of the present invention, in the second aspect of the present invention, the second non-inverting amplifier, which is inserted between the output terminal of the first non-inverting amplifier and the first inductor, has a gain of about 1 and can be adjusted.
The amplitude of the AC voltage applied across the first inductor can be adjusted by adjusting the gain of the second non-inverting amplifier. This makes it possible to make adjustment so that no alternating current flows through the inductor, and it is possible to secure a high input impedance even if an inductor having a small inductance is used as the first inductor.

According to a fourth aspect of the present invention, in the first to third aspects of the present invention, the DC voltage extracting section includes: a second inductor to which a voltage corresponding to the input voltage is applied to one end; An inverting amplifier that generates an AC voltage having the same amplitude and opposite phase as the AC voltage applied to the one end of the second inductor using the AC voltage output from the extracting unit;
A third inductor having the same inductance as the second inductor is inserted between the output terminal of the inverting amplifier and the other end of the second inductor, and is taken out from a connection point between the second inductor and the third inductor. A DC voltage is applied to the DC load. A voltage corresponding to an input voltage is applied to one end of a series circuit including a second inductor and a third inductor, and the other end has the same amplitude and opposite phase as the AC voltage. Of the second inductor and the third inductor
No AC voltage is extracted at the connection point with the inductor, and only the DC voltage is extracted. That is,
When extracting a DC voltage from an input voltage obtained by superimposing an AC voltage on a DC voltage, since the impedance of the inductor is not used, a small inductor having a small inductance can be used as the inductor, and a small and lightweight inductor is used. be able to. In addition, since the inductance of the second inductor through which a direct current flows is small, the second inductor can be used with a small number of turns, and as a result, the power consumption by the winding resistance is reduced and high power efficiency is obtained. Can be.

According to a fifth aspect of the present invention, in the first to third aspects of the present invention, in the DC voltage extracting section, a voltage corresponding to the input voltage is applied to one end and the other end is connected to the DC load. The first winding and a second winding to which an AC voltage corresponding to the AC voltage output from the AC voltage output unit is applied are formed by a transformer that is electromagnetically coupled, and the AC voltage applied to the second winding The AC voltage induced in the first winding has the same amplitude as the AC voltage applied to the one end of the first winding of the transformer, has a polarity for canceling the AC voltage, and has a polarity from the other end of the first winding. A DC voltage is applied to the DC load, and by applying a voltage corresponding to an input voltage to a second winding of the transformer, an AC voltage having the same amplitude as the AC voltage is induced in the first winding. Is applied to one end of the first winding. An AC voltage can be induced in the first winding so as to cancel an AC voltage of a voltage corresponding to the input voltage, and an AC voltage is not extracted from the other end of the first winding, and only a DC voltage is extracted. Will be. In other words, since the impedance of the inductor is not used in extracting the DC voltage from the input voltage obtained by superimposing the AC voltage on the DC voltage, a small transformer having a small number of turns can be used as the transformer. Can be used. Moreover, since the number of turns of the first winding of the transformer through which the DC current flows is small,
Power consumption by the winding resistance is reduced, and high power efficiency can be obtained.

According to a sixth aspect of the present invention, in the fourth or fifth aspect of the present invention, the gain is inserted between the output terminal of the AC voltage extracting section and the one end of the second winding of the transformer to have a gain of about 1. And a third non-inverting amplifier that can be adjusted by the above-mentioned method. By adjusting the gain of the third non-inverting amplifier, the amplitude of the AC voltage applied across the second winding of the transformer can be reduced. It is possible to adjust the AC voltage induced in the first winding by adjusting the AC voltage, so that the AC current can be prevented from flowing through the first winding of the transformer. The DC voltage can be reliably separated.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

FIG. 2 is an operation explanatory view of the above.

FIG. 3 is a circuit diagram showing a second embodiment of the present invention.

FIG. 4 is a circuit diagram showing a third embodiment of the present invention.

FIG. 5 is an operation explanatory view of the above.

FIG. 6 is a circuit diagram showing a fourth embodiment of the present invention.

FIG. 7 is a circuit diagram showing a fifth embodiment of the present invention.

FIG. 8 is a block diagram showing a conventional example.

[Explanation of symbols]

 4 AC / DC separation circuit A1 Non-inverting amplifier A2 Inverting amplifier A3 Non-inverting amplifier A5 Non-inverting amplifier C1 Capacitor L1 Inductor L2 Inductor L3 Inductor n1 First winding n2 Second winding T transformer Vac AC voltage Vac1 AC voltage Vdc DC voltage Vdc1 DC voltage Zac AC load Zdc DC load

Claims (6)

[Claims] An input voltage in which an AC voltage is superimposed on a DC voltage is separated into a DC voltage and an AC voltage, and the separated AC voltage is applied to an AC load and the separated DC voltage is applied to a DC load. An AC / DC separation circuit, which separates an AC voltage from the input voltage and supplies the AC voltage to an AC load through a buffer having a high input impedance. An AC / DC separation circuit, comprising: a DC voltage extractor for separating a DC voltage included in the input voltage by canceling an included AC voltage and applying the separated DC voltage to a DC load. A first capacitor for extracting an AC voltage from the input voltage; and a first buffer as the buffer for amplifying the AC voltage extracted by the first capacitor with a gain of one. Non-inverting amplifier and the first
And a first inductor which is AC-coupled to an output terminal of the non-inverting amplifier of the first embodiment, and wherein the input voltage and the AC voltage output from the first non-inverting amplifier are applied to respective one ends. An AC / DC separation circuit as described. 3. A non-inverting amplifier, which is inserted between an output terminal of the first non-inverting amplifier and the first inductor and whose gain can be adjusted around 1 is added. The AC / DC separation circuit according to claim 2. 4. The method according to claim 1, wherein the DC voltage output unit includes: a second inductor to which a voltage corresponding to the input voltage is applied to one end;
An inverting amplifier that generates an ac voltage having the same amplitude and opposite phase as the ac voltage applied to the one end of the second inductor by using the ac voltage output from the ac voltage extracting unit; A second inductor and a third inductor having the same inductance inserted between the other end of the second inductor and a DC voltage extracted from a connection point between the second inductor and the third inductor. The AC / DC separation circuit according to any one of claims 1 to 3, wherein the AC / DC separation circuit is provided. 5. An AC voltage output from the AC voltage extracting unit, wherein the DC voltage extracting unit is configured to apply a voltage corresponding to the input voltage to one end and connect the other end to the DC load. And a second winding to which an AC voltage corresponding to is applied is electromagnetically coupled to the transformer. An AC voltage induced in the first winding by the AC voltage applied to the second winding is applied to the first winding of the transformer. The first voltage has the same amplitude as the AC voltage applied to the one end of the winding and has a polarity for canceling the AC voltage, and
The AC / DC separation circuit according to any one of claims 1 to 3, wherein a DC voltage is applied to the DC load from the other end of the winding. 6. A third non-inverting amplifier, which is inserted between the output terminal of the AC voltage extracting section and the one end of the second winding of the transformer and whose gain can be adjusted around 1, is added. The AC / DC separation circuit according to claim 5, wherein: