JP2010141522A - Amplifier and communication apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an amplifier which can be downsized by eliminating the use of a choke coil used for the conventional E-class amplifier without losing high efficiency. <P>SOLUTION: The amplifier 100 includes: a filter circuit for interrupting a basic wave component and a secondary higher harmonic component which are included in a current supplied from a power supply; a switching element 104 connected between the filter circuit and ground potential; and a capacitor connected in parallel with the switching element 104 and connected between the filter circuit and the ground potential. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an amplifier and a communication device, and more particularly to a class E amplifier and a communication device including a class E amplifier.

  Conventionally, a class E amplifier, which is a kind of amplifier using a switching element, has been proposed and developed (for example, see Non-Patent Documents 1 to 3). The class E amplifier is ideally 100% efficient by an operation called ZVS (Zero Voltage Switching). ZVS means that even if a current flows through an on-state switching element, the switching element does not consume power if the voltage is zero.

  The class E amplifier is a technology developed in the 1970s as shown in Non-Patent Documents 1 and 2. In recent years, however, as shown in Non-Patent Document 3, attention has been paid to the development of a class E / F amplifier in which the harmonic processing characteristic of class F and inverse class F amplifiers is added to a class E amplifier. Technology. Recently, it has also been proposed to use this class E amplifier in the field of wireless power transmission in which power is transmitted by radio.

US Pat. No. 6,784,732 NO Sokal and ADSokal, “Class-E, a new class of high efficiency tuned single ended switchingpower amplifiers,” IEEE J. Solid-State Circuits, vol. SC-10, NO. 3, pp. 168-176, June 1975 . F. H. Raab, “Idealized Operation of the Class E Tuned Power Amplifier,” IEEE Trans. Circuits and Systems, vol. CAS-24, NO. 12, pp. 725-735, Dec. 1977. Scott D. Kee, IchiroAoki, Ali Hajimiri, and David Rutledge, “The Class-E / F Family of ZVS SwitchingAmplifiers,” IEEE Trans. Microwave Theory and Techniques, vol. 51, NO.6, pp.1677-1690, June 2003.

  However, as described in Non-Patent Documents 1 to 3, choke coils are used in conventional class E amplifiers. If the choke coil is used, there is a problem that the inductor becomes large. As a technique for solving this problem, a technique for replacing a choke coil with a filter is disclosed in Patent Document 1, for example. However, the technique disclosed in Patent Document 1 has a problem in that high efficiency as a class E amplifier is impaired as described later.

  Therefore, the present invention has been made in view of the above problems, and an object of the present invention is to reduce the size by not using a choke coil without impairing the high efficiency as a class E amplifier. It is an object of the present invention to provide a new and improved amplifier and communication apparatus capable of reducing the size of the apparatus.

  In order to solve the above problems, according to an aspect of the present invention, a filter circuit that blocks a fundamental wave component and a second harmonic component included in a supply current from a power supply, and a filter circuit between the ground potential and the filter circuit. An amplifier is provided, comprising: a switching element connected; and a capacitor connected in parallel with the switching element and connected between the filter circuit and a ground potential.

  According to this configuration, the filter circuit cuts off the fundamental wave component and the second harmonic component contained in the current supplied from the power supply, the switching element is connected between the filter circuit and the ground potential, and the capacitor is connected to the switching element. They are connected in parallel and connected between the filter circuit and the ground potential. As a result, it is possible to provide an amplifier that can be reduced in size without impairing high efficiency by blocking the fundamental wave component and the second harmonic component by the filter circuit.

  The filter circuit may include a fundamental wave cutoff circuit that cuts off a fundamental wave component included in the supply current and a second harmonic cutoff circuit that blocks a second harmonic component included in the supply current.

  Each of the fundamental wave cutoff circuit and the second harmonic cutoff circuit may be an LC parallel resonant circuit.

  A load resistor that consumes current from the filter circuit; and an impedance of an inductor included in the fundamental wave cutoff circuit and the second harmonic cutoff circuit is 1 to 10 times the impedance of the load resistor, Also good.

  The fundamental wave cutoff circuit and the second harmonic cutoff circuit may not resonate with the capacitor.

  Moreover, in order to solve the said subject, according to another viewpoint of this invention, a communication apparatus provided with the said amplifier is provided.

  As described above, according to the present invention, it is possible to provide a new and improved amplifier and communication apparatus that can be reduced in size without using a choke coil without impairing high efficiency.

  Exemplary embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In addition, in this specification and drawing, about the component which has the substantially same function structure, duplication description is abbreviate | omitted by attaching | subjecting the same code | symbol.

Further, preferred embodiments of the present invention will be described in detail according to the following order.
<1. Conventional Class E Amplifier>
[1-1. Configuration of conventional class E amplifier]
[1-2. Configuration of conventional class E amplifier]
[1-3. Problems of conventional class E amplifier]
<2. Class E Amplifier According to One Embodiment of the Present Invention>
[2-1. Configuration of Class E Amplifier According to One Embodiment of the Present Invention]
[2-2. Operation of Class E Amplifier According to One Embodiment of the Present Invention]
<3. Communication device including class E amplifier according to one embodiment of the present invention>
<4. Summary>

<1. Conventional Class E Amplifier>
First, before describing a preferred embodiment of the present invention, the configuration and operation of a conventional class E amplifier and the problems of the conventional class E amplifier will be described.

[1-1. Configuration of conventional class E amplifier]
FIG. 3 is an explanatory diagram showing a circuit configuration of a conventional general class E amplifier 10. As shown in FIG. 3, in general, the class E amplifier 10 includes a choke coil 11, a switching element 12, a capacitor C1, a series resonator 13, a phase shift coil Lx, a load resistor R, It is comprised including. The series resonator 13 includes a capacitor C2 and an inductor L2.

  The choke coil 11 is an electronic component that is generally used to block a high-frequency current exceeding a predetermined frequency, and has a function of supplying a direct current I_DC from a power supply VDD. The switching element 12 can be a bipolar transistor, a field effect transistor, or other switching element, and is an element that repeatedly turns on and off in response to a rectangular wave signal with a duty ratio of 50% shown in FIG. When the switching element 12 is on, the switching element current I_TR flows, and when the switching element 12 is off, no current flows.

  A current from the choke coil 11 flows into the capacitor C1 when the switching element 12 is off. At this time, the current flowing through the capacitor C1 is defined as I_C1. The capacitance of the capacitor C1 is C1. The series resonator 13 composed of the capacitor C2 and the inductor L2 has a function of a band-pass filter that passes the output current I_OUT having an operating frequency defined by the capacitor C2 and the inductor L2 and is open at a frequency other than the operating frequency.

  The phase shift coil Lx is a reactance for shifting the fundamental voltage and current with respect to the output current I_OUT. The phase shift coil Lx is provided to satisfy the phase condition required for the class E amplifier. The load resistance R consumes the current phase-shifted by the phase-shift coil Lx.

[1-2. Configuration of conventional class E amplifier]
FIG. 5 shows the switching element current I_TR in the class E amplifier 10 shown in FIG. 3 and the current I_C1 flowing in the capacitor C1 normalized by the direct current I_DC. In FIG. 5, the solid line is the switching element current I_TR, the dotted line is the current I_C1 flowing through the capacitor C1, and the alternate long and short dash line is the direct current I_DC.

  The four currents (I_DC, I_TR, I_C1, I_OUT) shown in FIG. 3 follow Kirchhoff's first law at node A in FIG. Therefore, the remainder obtained by subtracting the output current I_OUT from the direct current I_DC becomes the switching element current I_TR and the current I_C1 flowing through the capacitor C1.

  As shown in FIG. 5, 1.0 [A] always flows through the direct current I_DC. Further, the switching element current I_TR is 0.0 [A] because the switching element 12 is off during the time from 0.0 [s] to 0.5 [s], so that no current flows. When the time is between 0.5 [s] and 1.0 [s], the switching element 12 is turned on, and the switching element current I_TR rises sharply. The switching element current I_TR reaches a peak at about 0.8 [s], and after gradually decreasing, when the time reaches 1.0 [s], the switching element 12 is turned off again, and the switching element current I_TR becomes 0.0. [A].

  The current I_C1 flowing through the capacitor C1 is about 2.0 [A] at time 0.0 [s]. However, if the switching element 12 is turned off between the time of 0.0 [s] and 0.5 [s], the voltage drops to about −0.9 [A] and then returns to 0.0 [A]. While the time is between 0.5 [s] and 1.0 [s], the switching element 12 is turned on, and current flows through the switching element 12, while the current I_C1 flowing through the capacitor C1 is 0.0 [A]. Become.

  When the switching element current I_TR shown in FIG. 5 and the current I_C1 flowing through the capacitor C1 are combined, the center is a sine wave of 1.0 [A]. This sine wave indicates the remainder obtained by subtracting the current I_OUT flowing through the series resonator 13 including the capacitor C2 and the inductor L2 from the direct current I_DC. The sine wave offset 1.0 [A] is equal to the direct current I_DC flowing through the choke coil 11.

  Since the capacitor C1 does not pass a direct current, the current I_C1 flowing through the capacitor C1 is integrated from the time 0.0 [s] to 0.5 [s] to 0.0 [A]. A voltage is generated at the node A in proportion to the amount of charge accumulated in the capacitor C1 by the current I_C1. Therefore, when the switching element 12 is turned off at time 0.0 [s], the voltage at the node A rises sharply from 0.0 [V] as charge is accumulated in the capacitor C1, and the current I_C1 The peak is reached when the waveform becomes zero. After that, the voltage of the node A decreases and returns to 0.0 [V] again at time 0.5 [s]. The voltage at the node A is the switching element voltage V_TR applied to the switching element 12 in the off state.

  In summary, a current flows through the switching element 12 in the on state, and the voltage applied when the switching element 12 is in the on state is 0.0 [V]. Then, no current flows when the switching element 12 is in the off state, and the voltage applied when the switching element 12 is in the off state changes from moment to moment. This is ZVS.

  FIG. 6 is an explanatory diagram illustrating, in a graph, the normalized switching element voltage V_TR applied to the switching element 12 and the switching element current I_TR flowing through the switching element 12. In the graph shown in FIG. 6, the solid line is the switching element voltage V_TR normalized by the power supply voltage V_DD, and the dotted line is the switching element current I_TR normalized by the direct current I_DC. FIG. 6 shows the state of ZVS.

  Thus, the choke coil is used in the conventional class E amplifier. However, when the choke coil is used, there is a problem that the inductor becomes large. This problem becomes a hindrance to downsizing and reducing power consumption when a class E amplifier is used in a device aiming at downsizing and reducing power consumption. As a technique for solving this problem, as described above, Patent Document 1 discloses a technique for replacing a choke coil with a filter.

  FIG. 7 is an explanatory diagram showing a configuration of a conventional class E amplifier 20 disclosed in Patent Document 1 that does not use a choke coil. As shown in FIG. 7, the class E amplifier 20 includes a filter 21, a switching element 22, a capacitor C1, a series resonator 23, a phase shift coil Lx, and a load resistor R. . The filter 21 includes inductors LF1 and LF2 and a capacitor CF1, and the series resonator 23 includes a capacitor C2 and an inductor L2.

  According to Patent Document 1, it is described that the inductor LF1 and the capacitor CF1 included in the filter 21 and the inductor LF2 and the capacitor C1 operate as a two-frequency resonance filter. At the second harmonic, the impedance of the filter 21 is −1 / jωC1. On the other hand, since the impedance of the capacitor C1 is 1 / jωC1, the parallel combined impedance of the filter 21 and the capacitor C1 is infinite, that is, open at the second harmonic, and the filter 21 is short-circuited at the third harmonic.

  Here, Table 1 below shows frequency components obtained by Fourier-transforming the switching element current I_TR and the current I_C1 flowing through the capacitor C1 shown in FIG. 5 to the ninth harmonic.

  As is apparent from Table 1, the switching element current I_TR includes a direct current component, a fundamental wave, and a harmonic component. On the other hand, the current I_C1 flowing through the capacitor C1 does not include a DC component. This is because the capacitor C1 does not pass a direct current. Further, from Table 1, all the harmonic components of I_TR and I_C1 have the same magnitude and are different in phase by 180 degrees. As a result, it can be seen that in the sum of I_TR and I_C1, only the DC component and the fundamental wave component remain, and the harmonic component is zero.

  The occurrence of frequency components as shown in Table 1 can be explained as follows using FIG. In the class E amplifier 10, a continuous flow of the fundamental current I_OUT is generated by the fundamental series resonance filter including the capacitor C2 and the inductor L2. The switching element 12 and the capacitor C1 are in the path of the fundamental current I_OUT, and the switching element 12 is switched on and off by the rectangular wave shown in FIG. Therefore, the fundamental current I_OUT is time-divided into the switching element 12 and the capacitor C1 by a time rate of 50%. Since switching in the time domain is multiplication, the switching element current I_TR and the current I_C1 flowing in the capacitor C1 by the frequency mixing with the higher order harmonics of the rectangular wave are higher order harmonic components as shown in Table 1. Occurs.

  FIG. 8 is an explanatory diagram showing the magnitudes of the frequency components of the switching element current I_TR and the current I_C1 flowing in the capacitor C1 shown in Table 1. In the graph shown in FIG. 8, the horizontal axis indicates the order, and the vertical axis indicates the power spectral density. As shown in FIG. 8, the power spectral density of the third and higher order harmonic components included in I_TR and I_C1 may be as small as about −20 dB compared to the magnitude of the fundamental component obtained by adding I_TR and I_C1. I understand. On the other hand, the power spectral density of the fundamental wave and the second harmonic component is about −2 to −11 dB. Therefore, even if the third and higher order harmonic components are lost, only a small loss is required. However, since the fundamental wave and the second harmonic components are of a size that cannot be ignored, these components cannot be lost in the class E amplifier. .

  However, in the class E amplifier 20 shown in FIG. 7, the second harmonic component contained in the switching element current I_TR is blocked by the resonance between the filter 21 and the capacitor C1, and therefore, the class E amplifier 20 shown in FIG. In addition, the current waveform of the switching element current I_TR is greatly deformed. As a result, in the class E amplifier 20 shown in FIG. 5, the high efficiency of the class E amplifier may be impaired.

  Therefore, an object of the present invention is to reduce the size of the class E amplifier by eliminating the choke coil without impairing the high efficiency.

<2. Class E Amplifier According to One Embodiment of the Present Invention>
[2-1. Configuration of Class E Amplifier According to One Embodiment of the Present Invention]
FIG. 1 is an explanatory diagram showing a configuration of a class E amplifier 100 according to an embodiment of the present invention. Hereinafter, the configuration of a class E amplifier 100 according to an embodiment of the present invention will be described with reference to FIG.

  As shown in FIG. 1, a class E amplifier 100 according to an embodiment of the present invention includes a fundamental wave rejection filter 101, a second harmonic rejection filter 102, a switching element 104, a capacitor C1, and a series resonator. 106, a phase shift coil Lx, and a load resistance R. The fundamental wave blocking filter 101 includes an inductor LF1 and a capacitor CF1, and the second harmonic blocking filter 102 includes an inductor LF2 and a capacitor CF2. The series resonator 106 includes a capacitor C2 and an inductor L2.

  As shown in FIG. 1, the fundamental wave rejection filter 101 and the second harmonic rejection filter 102 according to the present embodiment use an LC parallel resonance circuit. The fundamental wave rejection filter 101 and the second harmonic rejection filter 102 each supply a quasi-direct current I_DC ′ from the power supply VDD, and cut off the fundamental wave component and the second harmonic component in the current supplied from the power supply VDD. Has the function of Therefore, the fundamental wave rejection filter 101 and the second harmonic rejection filter 102 have a role of blocking the fundamental wave and the second harmonic with respect to both of the current flowing through the switching element 104 and the capacitor C1. Here, “quasi-direct current” means that it is not completely direct current but contains a slight alternating current component. Note that capacitors and inductors in the fundamental wave blocking filter 101 and the second harmonic blocking filter 102 are of any capacitance or inductance as long as they can block the fundamental wave component and the second harmonic component. May be.

  As the switching element 104, a bipolar transistor, a field effect transistor, or other switching elements can be used. The switching element 104 is an element that repeatedly turns on and off in response to a rectangular wave having a duty ratio of 50% shown in FIG. When the switching element 104 is on, a switching element current I_TR flows, and when the switching element 104 is off, no current flows.

  When the switching element 104 is off, the current from the fundamental wave blocking filter 101 and the second harmonic blocking filter 102 flows into the capacitor C1. At this time, the current flowing through the capacitor C1 is defined as I_C1.

  The series resonator 106 composed of the capacitor C2 and the inductor L2 has a function of a band-pass filter that passes the output current I_OUT having an operating frequency defined by the capacitor C2 and the inductor L2 and is open at frequencies other than the operating frequency. The phase shift coil Lx is a reactance for shifting the fundamental voltage and current with respect to the output current I_OUT. The phase shift coil Lx is provided to satisfy the phase condition required for the class E amplifier. The load resistance R consumes the current phase-shifted by the phase-shift coil Lx.

  The configuration of the class E amplifier 100 according to one embodiment of the present invention has been described above. Next, the operation of the class E amplifier 100 according to one embodiment of the present invention will be described.

[2-2. Operation of Class E Amplifier According to One Embodiment of the Present Invention]
In describing the operation of the class E amplifier 100 according to an embodiment of the present invention, equations for obtaining the constants of the elements of the class E amplifier 100 shown in FIG. The power supply voltage is VDD, the output power is Po, the angular frequency is ω, and the load Q of the series resonator 106 is QL2. These mathematical expressions are obtained by appropriately modifying the mathematical expressions derived by Non-Patent Document 2.

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・・・（数式２）

・・・（数式３）

・・・（数式４）

・・・（数式５）

... (Formula 1)

... (Formula 2)

... (Formula 3)

... (Formula 4)

... (Formula 5)

  The class E amplifier 100 shown in FIG. 1 is significantly different from the class E amplifier 20 shown in FIG. 5 in that the fundamental rejection filter 101 and the second harmonic rejection filter 102 are not in a resonance relationship with the capacitor C1. Is a point. This means that the fundamental wave component and the second harmonic component included in the current I_C1 flowing through the capacitor C1 are not impaired. Therefore, the class E amplifier 100 shown in FIG. 1 does not impair the fundamental wave component and the second harmonic component contained in the switching element current I_TR and the current I_C1 flowing in the capacitor C1, so the class E amplifier 20 shown in FIG. This has the effect of improving efficiency.

  In the class E amplifier 100 shown in FIG. 1, the impedance of the inductor used in the fundamental wave rejection filter 101 and the second harmonic rejection filter 102 may be about several times the impedance of the load resistor R. More specifically, the impedance of the inductors used in the fundamental wave blocking filter 101 and the second harmonic blocking filter 102 can be 1 to 10 times the impedance of the load resistor R. In a conventional class E amplifier, a choke coil having an impedance about 20 times the load resistance is generally used. Compared to this, the class E amplifier 100 according to the present embodiment has an effect that the inductor can be significantly reduced in size.

  In FIG. 1, the filters are provided in the order of the fundamental wave rejection filter 101 and the second harmonic rejection filter 102, but it goes without saying that the order of these filters may be reversed in the present invention. In this embodiment, the LC parallel resonance circuit is used for the fundamental wave blocking filter 101 and the second harmonic blocking filter 102, but it goes without saying that the present invention is not limited to such an example. That is, the amplifier of the present invention is shown in FIG. 1 as long as it has a function of blocking the current including the fundamental wave and the current including the second harmonic among the current supplied from the power supply VDD. Needless to say, the configuration is not limited.

<3. Communication device including class E amplifier according to one embodiment of the present invention>
Next, a communication apparatus including the class E amplifier 100 according to an embodiment of the present invention will be described. FIG. 2 is an explanatory diagram showing the communication device 200 including the class E amplifier 100 according to the embodiment of the present invention. FIG. 2 also shows a communication device 300 on the receiving side in addition to the communication device 200 on the transmission side provided with the class E amplifier 100.

  As shown in FIG. 2, the communication apparatus 200 includes a class E amplifier 100, a power source 220 that supplies the voltage VDD to the class E amplifier 100, an AC power source 230 that controls switching of the switching element 104 of the class E amplifier 100, , Including. The communication device 200 is a device that wirelessly transmits power to the communication device 300. In the communication device 200, power is amplified by the class E amplifier 100, and radio waves are transmitted from the antenna 210 provided in the communication device 200 to the antenna 310 provided in the communication device 300. The communication device 300 can receive power by demodulating the radio wave received by the antenna 310.

  As described above, by applying the class E amplifier 100 according to the embodiment of the present invention to the communication device 200, it is possible to improve the efficiency in wireless power transmission. The communication apparatus including the class E amplifier 100 according to the embodiment of the present invention has been described above. Needless to say, the configuration of the communication apparatus including the class E amplifier 100 according to the embodiment of the present invention is not limited to that shown in FIG.

<4. Summary>
As described above, the class E amplifier 100 according to the embodiment of the present invention replaces the conventionally used choke coil with the fundamental wave rejection filter 101 and the second harmonic rejection filter 102. Replacing the choke coil with the fundamental wave blocking filter 101 and the second harmonic blocking filter 102 does not impair the efficiency as a class E amplifier even when compared with a conventional class E amplifier, and compared with a conventional class E amplifier. Thus, the inductor can be reduced in size.

  As mentioned above, although preferred embodiment of this invention was described referring an accompanying drawing, it cannot be overemphasized that this invention is not limited to the example which concerns. It will be apparent to those skilled in the art that various changes and modifications can be made within the scope of the claims, and these are naturally within the technical scope of the present invention. Understood.

  The present invention relates to an amplifier and a communication device, and is particularly applicable to a class E amplifier and a communication device including a class E amplifier.

It is explanatory drawing shown about the structure of the class E amplifier 100 concerning one Embodiment of this invention. It is explanatory drawing shown about the communication apparatus 200 provided with the class E amplifier 100 concerning one Embodiment of this invention. It is explanatory drawing shown about the circuit structure of the conventional general class E amplifier 10. FIG. It is explanatory drawing shown about the waveform of the signal applied to a switching element. It is explanatory drawing shown about the switching element electric current and the electric current which flows into the capacitor C1. It is explanatory drawing which shows what normalized the switching element voltage and the switching element current, respectively. It is explanatory drawing shown about the structure of the class E amplifier 20 which does not use the conventional choke coil. It is explanatory drawing which shows the magnitude | size of the frequency component of the switching element electric current and the electric current which flows into the capacitor C1 with a graph.

Explanation of symbols

10, 20, 100 Class E amplifier 11 Choke coil 12, 22, 104 Switching element 101 Fundamental rejection filter 102 Double harmonic rejection filter 200, 300 Communication device C1, C2, CF1, CF2 Capacitors 13, 23, 106 Series resonance Lx Phase shift coil R Load resistance L2, LF1, LF2 Inductor

Claims (6)

A filter circuit that cuts off a fundamental wave component and a second harmonic component contained in a current supplied from a power supply;
A switching element connected between the filter circuit and a ground potential;
A capacitor connected in parallel with the switching element and connected between the filter circuit and the ground potential;
An amplifier. The filter circuit is
A fundamental wave cutoff circuit that cuts off a fundamental wave component included in the supply current;
A second harmonic blocking circuit that blocks a second harmonic component contained in the supply current;
The amplifier of claim 1 comprising:   The amplifier according to claim 2, wherein each of the fundamental wave cutoff circuit and the second harmonic cutoff circuit is an LC parallel resonance circuit. A load resistor that consumes current from the filter circuit;
The amplifier according to claim 3, wherein an impedance of an inductor included in the fundamental wave cutoff circuit and the second harmonic cutoff circuit is 1 to 10 times the impedance of the load resistance.   The amplifier according to claim 3, wherein the fundamental wave cutoff circuit and the second harmonic cutoff circuit do not resonate with the capacitor. A communication apparatus comprising the amplifier according to claim 1.

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