Switching Amplifier

Abstract

The present invention increases the output voltage of a switching amplifier in situations where the power source voltage is limited.　This switching amplifier is equipped with a first and a second switch for opening and closing in a complementary manner, and a capacitor, both ends of which are inputs to a power combiner. The capacitor is connected at both ends to the output ends of the first and second switches. The capacitor receives a supply from the power source according to the operation of the first and second switches. As a result, the load of the capacitor is used as a charge pump, is used to alternatingly boost or step-down the output voltage via the operating frequency of the switching amplifier, and generates a square wave voltage, the wave height of which is controlled.

Description

[Technical field]

[0001] The present technology relates to a switching amplifier, and more particularly to a switching amplifier that performs step-up or step-down. [Background technology]

[0002] There are two types of switching amplifiers known in general: Class D and Class E. In principle, switching amplifiers are highly efficient, and therefore they are increasingly being used in communication amplifiers for mobile devices in recent years. However, the increase in mobile devices has worsened communication conditions. For this reason, the output power of power amplifiers is required to be high. However, there is an upper limit to the battery voltage, such as lithium-ion batteries, used in mobile devices. When the power supply voltage supplied to the amplifier is fixed, in order to increase the output power of the amplifier, it is necessary to lower the impedance of the amplifier and load and increase the output current of the amplifier. In order to increase the output power, lowering the circuit impedance and increasing the output current is often disadvantageous in terms of efficiency. For example, the loss due to the parasitic resistance of the wiring increases in proportion to the increase in output current. In addition, when lowering the load impedance, the number of matching elements increases, and signal passage loss generally increases. In other words, when increasing the output power, Class D amplifiers, which output the power supply voltage as it is, have the side effect of increasing the loss associated with the increase in output current. In contrast, a Class E amplifier can boost the output voltage by designing the resonant impedance of the matching circuit to be high, even if the power supply voltage is limited, and can increase the output power without increasing the output current.

[0003] In this respect, the class E amplifier can be said to be an excellent amplifier with low loss in realizing a high-output power amplifier. However, the degree of boost of the output voltage of the class E amplifier is greatly influenced by the resonant impedance of the matching circuit. Here, consider the case where the antenna of a transmitter using a class E amplifier is brought close to metal. The proximity of the antenna to the metal may cause the antenna impedance to deviate significantly from the standard 50 ohms. If the impedance of the antenna changes, the resonant impedance of the matching circuit of the class E amplifier changes. The output voltage of the class E amplifier may be boosted unexpectedly due to the change in the resonant impedance, which may cause the amplifier to break down. In other words, to realize a low-loss high-output amplifier, the output voltage boosting action is effective in preventing the output current from increasing, but the amount of boost must be controlled to a constant amount regardless of the external environment. Therefore, a charge pump circuit has been proposed as a representative technology for obtaining a controlled voltage boost (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-164386 A Summary of the Invention [Problem to be solved by the invention]

[0005] According to the above-mentioned charge pump circuit, the boost amount can be controlled to be constant by charging a constant charge to the capacitance using the rectification effect of the diode or a switching element. However, power loss occurs in the diode or switching element during charging. Furthermore, power consumption occurs in controlling the switching element. That is, in the boost of a general charge pump, the boost amount is controlled to be constant, but the area increases due to circuit elements other than the amplifier, power loss occurs, and power consumption for control occurs. In addition, a class D amplifier using a negative power supply and a positive power supply is also common, which is equivalent to controlling the boost amount to be constant, but a power supply circuit is required to generate the negative voltage, which increases both the area and power consumption. Thus, there is a problem that power consumption increases or the reliability of the amplifier is sacrificed in order to increase the output power of the amplifier in a situation where the power supply voltage is limited.

[0006] The present technology was developed in consideration of these circumstances, and aims to increase the output voltage of a switching amplifier in a situation where the power supply voltage is limited. [Means for solving the problem]

[0007] The present technology has been made to solve the above-mentioned problems, and a first aspect thereof is a switching amplifier including first and second switches that open and close complementarily, and a capacitance having both ends connected to output terminals of the first and second switches to receive a power supply.

[0008] In addition, in the first aspect, the capacitor may further include a first impedance element connected between one end of the capacitor and a power supply terminal, and a second impedance element connected between the other end of the capacitor and a ground terminal, thereby providing an effect of supplying power to the capacitor via the first and second impedance elements to charge it.

[0009] Also, in this first aspect, the first switch may have an input end connected to a power supply terminal and an output end connected to the other end of the capacitance, and the second switch may have an input end connected to a ground terminal and an output end connected to the one end of the capacitance.

[0010] In addition, in the first aspect, the power amplifier may further include a power combiner that combines power of signals supplied from both ends of the capacitance and supplies the result from an output terminal to a load.

[0011] In addition, in the first aspect, the power combiner may include first and second capacitors having both ends of the capacitance connected to the respective input terminals and a terminal to which the output terminals are coupled as the output terminal, thereby achieving the effect of realizing the power combiner by the first and second capacitors.

[0012] In addition, in the first aspect, the power combiner may include the first and second capacitors instead of the capacitance, thereby providing an effect of imparting the role of the capacitance to the first and second capacitors of the power combiner.

[0013] In the first aspect, the power combiner may include a transformer instead of the first and second impedance elements, thereby providing an effect that the power combiner is realized by the transformer.

[0014] In addition, in the first aspect, the power combiner may include first and second grounded-gate transistors, each of which has both ends of the capacitance connected to its respective source and has a terminal connecting the drains of the first and second grounded-gate transistors as the output terminal, thereby making the grounded-gate transistors function as switches to make the combined voltage the same as the source voltage.

[0015] In the first aspect, the first and second switches may include first and second transistors that open and close complementarily. This provides an effect that the first and second switches are realized by the first and second transistors.

[0016] In the first aspect, the first and second switches may further include a first common-gate transistor cascode-connected to the first transistor and a second common-gate transistor cascode-connected to the second transistor, thereby providing an effect of dividing the voltage applied to each transistor.

[0017] In the first aspect, the first and second switches may include first and second common-gate transistors that open and close complementarily, thereby providing an effect of dividing the voltage applied to each transistor.

[0018] In addition, in the first aspect, the first and second switches may be further connected to both ends of the capacitance, so that the first and second switches and the capacitance are connected in a plurality of stages, thereby providing an effect of increasing the voltage that is ultimately output. [Brief description of the drawings]

[0019] [Figure 1] 1 is a diagram illustrating an example of a basic configuration of a switching amplifier according to an embodiment of the present technology; [Diagram 2] 1 is a diagram illustrating an example of an overall configuration of a switching amplifier according to an embodiment of the present technology; [Diagram 3] 4A and 4B are diagrams illustrating an example of an output waveform of a switching amplifier according to an embodiment of the present technology. [Figure 4] 11 is a diagram illustrating a modification of a switching amplifier according to an embodiment of the present technology. [Diagram 5] 1 is a diagram illustrating a first example of a switching amplifier according to an embodiment of the present technology. [Figure 6]11 is a diagram illustrating a second example of a switching amplifier according to an embodiment of the present technology. FIG. [Figure 7] FIG. 11 is a diagram illustrating a third example of a switching amplifier according to an embodiment of the present technology. [Figure 8] FIG. 11 is a diagram illustrating a fourth example of a switching amplifier according to an embodiment of the present technology. [Figure 9] FIG. 13 is a diagram illustrating a fifth example of a switching amplifier according to an embodiment of the present technology. [Figure 10] FIG. 13 is a diagram illustrating a sixth example of a switching amplifier according to an embodiment of the present technology. [Figure 11] FIG. 13 is a diagram illustrating a seventh example of a switching amplifier according to an embodiment of the present technology. [Figure 12] FIG. 13 is a diagram illustrating an eighth example of a switching amplifier according to an embodiment of the present technology. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, modes for carrying out the present technology (hereinafter, referred to as embodiments) will be described. The description will be made in the following order. 1.Basic configuration 2. Working Example

[0021] <1.Basic configuration> [Switching amplifier configuration] 1 is a diagram showing an example of a basic configuration of a switching amplifier according to an embodiment of the present technology. The switching amplifier includes switches 110 and 120, inductors 210 and 220, and a capacitor 230.

[0022] The switches 110 and 120 are switches that open and close complementarily. An output terminal of the switch 110 is connected to one end on the negative side of the capacitance 230. A power supply terminal is connected to an input terminal of the switch 110, as described below. An output terminal of the switch 120 is connected to one end on the positive side of the capacitance 230. A ground terminal is connected to an input terminal of the switch 120, as described below.

[0023] The inductors 210 and 220 are an example of an impedance element that passes direct current to charge the capacitance 230. The inductor 210 is connected between one end on the positive side of the capacitance 230 and a power supply terminal. The inductor 220 is connected between one end on the negative side of the capacitance 230 and a ground terminal. In this example, the inductors 210 and 220 are shown as an example of an impedance element, but other elements may be used. In that case, it is necessary that the inductors have a high impedance to high-frequency signals and a low impedance to low-frequency signals (direct current). It is also necessary that the inductors are not affected by the voltage ranges of the power supply potential and the ground potential, that is, that they do not have voltage dependency.

[0024] Capacitor 230 is an element that functions as a charge pump by storing electric charge via inductors 210 and 220. That is, in this switching amplifier, the electric charge stored in capacitor 230 is used to control the amount of step-up and step-down of the output voltage.

[0025] FIG. 2 is a diagram illustrating an example of an overall configuration of a switching amplifier according to an embodiment of the present technology.

[0026] This switching amplifier includes a power combiner 300 in the subsequent stage of the above-mentioned basic configuration. A power supply terminal is connected to an input terminal of a switch 110, and a ground terminal is connected to an input terminal of a switch 120.

[0027] The power combiner 300 combines the power of the signals supplied from both ends of the capacitance 230, and supplies the combined power to the load 400 from an output terminal.

[0028] The amount of steady-state charge stored in capacitance 230 is determined by the voltage applied to capacitance 230 and the capacitance value. Therefore, the amount of boost and drop of the output voltage to power combiner 300 is controlled to a constant value. The charge stored in capacitance 230 is used as a charge pump to alternately boost and drop the output voltage at the operating frequency of the switching amplifier.

[0029] [Switching amplifier output] FIG. 3 is a diagram illustrating an example of an output waveform of a switching amplifier according to an embodiment of the present technology.

[0030] Here, the voltage at one end of the positive side of capacitance 230 is referred to as V_N, and the current flowing through one end of the positive side of capacitance 230 is referred to as I_N. Furthermore, the voltage at one end of the negative side of capacitance 230 is referred to as V_P, and the current flowing through one end of the negative side of capacitance 230 is referred to as I_P. In the figure, "a" indicates the voltage V_P at one end of the negative side of capacitance 230. "b" in the figure indicates the voltage V_N at one end of the positive side of capacitance 230. "c" in the figure indicates the current I_P flowing through switch 110. "d" in the figure indicates the current I_N flowing through switch 120.

[0031] In state (1), switch 110 is on and switch 120 is off. In this case, voltage V_P at one end on the negative side of capacitance 230 is the power supply voltage VDD. At this time, a potential difference of VDD occurs between both ends of capacitance 230 due to the charged charge, so voltage V_N at one end on the positive side of capacitance 230 is twice the potential of VDD.

[0032] In state (2), the switch 110 is in an OFF state, and the switch 120 is in an ON state. In this case, the voltage V_N at one end on the positive side of the capacitance 230 is at the ground potential. At this time, a potential difference of VDD occurs between both ends of the capacitance 230 due to the charged charge, so the voltage V_P at one end on the negative side of the capacitance 230 is −VDD.

[0033] Therefore, by connecting switches 110 and 120 to both ends of capacitance 230 and opening and closing them complementarily to repeat state (1) and state (2), a square wave voltage with a peak value controlled like a class D amplifier is generated. That is, the voltage is boosted at one end on the positive side of capacitance 230 and dropped at one end on the negative side of capacitance 230, and each node becomes an in-phase square wave voltage with an amplitude of 2VDD.

[0034] As a result, the currents I_P and I_N flowing through the switches 110 and 120 have a push-pull relationship. The power combiner 300 combines the power thus generated. Therefore, the current flowing through the load 400 becomes a sine wave that is a combination of c and d in the figure.

[0035] [Variations] FIG. 4 is a diagram showing a modification of the switching amplifier according to the embodiment of the present technology.

[0036] The basic configuration of the switching amplifier described above may be cascaded in multiple stages as in this modified example. That is, the switches 110 and 120 may be further connected to both ends of the capacitance 230, and the switches 110 and 120 and the capacitance 230 may be connected in multiple stages. This makes it possible to increase the voltage that is ultimately output.

[0037] <2. Implementation form> [First Example] FIG. 5 is a diagram illustrating a first example of a switching amplifier according to an embodiment of the present technology.

[0038] In this first embodiment, the power combiner 300 includes capacitances 310 and 320. That is, in this first embodiment, the power combiner 300 is realized by capacitive coupling. In this case, no DC current flows to the load 400, and only the AC component is transmitted.

[0039] [Second Example] FIG. 6 is a diagram illustrating a second example of a switching amplifier according to an embodiment of the present technology.

[0040] In the second embodiment, the capacitance 230 is removed from the first embodiment. In this case, the capacitances 310 and 320 of the power combiner 300 play the same role as the capacitance 230. That is, the series-connected capacitances 310 and 320 function as the capacitance 230 and also realize capacitive coupling to the load 400. Therefore, the capacitance 390 between the power combiner 300 and the load 400 may not be necessary.

[0041] [Third Example] FIG. 7 is a diagram illustrating a third example of a switching amplifier according to an embodiment of the present technology.

[0042] In the third embodiment, the power combiner 300 includes transformers 311 and 321. That is, in the third embodiment, the power combiner 300 includes the inductors 210 and 220 and is configured to be magnetically coupled (transformer coupled) with the load 400.

[0043] As a result, in the third embodiment, it becomes possible to transform not only AC components but also DC components.

[0044] [Fourth Example] FIG. 8 is a diagram illustrating a fourth example of a switching amplifier according to an embodiment of the present technology.

[0045] In the fourth embodiment, the power combiner 300 includes MOS transistors 312 and 322. The source of the transistor 312 is connected to one end on the positive side of the capacitance 230, and the base is connected to a power supply terminal. The source of the transistor 322 is connected to one end on the negative side of the capacitance 230, and the base is connected to a ground terminal. The drains of the transistors 312 and 322 are connected to each other and to a load 400 via a capacitance 390.

[0046] As a result, in the fourth embodiment, the MOS transistors 312 and 322 can function as switches to make the maximum and minimum values ​​of the combined voltage the same as the input voltage.

[0047] [Fifth Example] FIG. 9 is a diagram illustrating a fifth example of a switching amplifier according to an embodiment of the present technology.

[0048] In the fifth embodiment, the switches 110 and 120 include common-source transistors 111 and 121. An AC signal is input to the gates of the transistors 111 and 121 via a buffer 130, and the transistors 111 and 121 function as switches that open and close in a complementary manner in accordance with the AC signal.

[0049] [Sixth Example] FIG. 10 is a diagram illustrating a sixth example of a switching amplifier according to an embodiment of the present technology.

[0050] In the sixth embodiment, the switches 110 and 120 include transistors 111, 112, 121, and 122. Here, the transistors 111 and 112 are cascode-connected. That is, the configuration includes a common-source transistor 111 and a common-gate transistor 112 connected to each other. Similarly, the transistors 121 and 122 are cascode-connected. This allows the voltage applied to each transistor to be divided, and each transistor can be protected.

[0051] [Seventh Example] FIG. 11 is a diagram illustrating a seventh example of a switching amplifier according to an embodiment of the present technology.

[0052] In the seventh embodiment, the switches 110 and 120 include inverters 131 and 132 instead of the transistors 111 and 121 in the sixth embodiment. This makes it possible to divide the voltage applied to each transistor more accurately than in the sixth embodiment.

[0053] [Eighth embodiment] FIG. 12 is a diagram illustrating an eighth example of a switching amplifier according to an embodiment of the present technology. In FIG.

[0054] In the eighth embodiment, the inverters 131 and 132 in the seventh embodiment are combined into one inverter 133. However, logically, the two are equivalent.

[0055] As described above, according to the embodiment of the present technology, the capacitor 230 is charged via the inductors 210 and 220, and the switches 110 and 120 are complementarily opened and closed, so that the capacitor 230 can function as a charge pump. This allows a square wave voltage with a controlled wave height to be generated, and the output voltage of the switching amplifier can be increased in a situation where the power supply voltage is limited.

[0056] The output current and output voltage waveform of the switching amplifier according to the embodiment of the present technology are the same as those of a class D amplifier. However, compared to a normal class D amplifier, the output voltage is boosted, so the output power increases. If the voltage charged to the capacitance 230 is VDD as in the above example, the output voltage amplitude doubles, so the output power becomes four times. Even though the output power becomes four times, the switch size of the amplifier does not change, so the input power for driving the amplifier does not change. In other words, the power added efficiency (power efficiency obtained by dividing the ratio of the output power to the input power by the power consumption), which is a performance index of the power amplifier, increases dramatically. In addition, since the switch size of the amplifier does not change, it contributes to reducing the chip area.

[0057] The above-mentioned embodiment shows an example for realizing the present technology, and the matters in the embodiment and the matters specified in the claims correspond to each other. Similarly, the matters specified in the claims and the matters in the embodiment of the present technology having the same name correspond to each other. However, the present technology is not limited to the embodiment, and can be realized by applying various modifications to the embodiment within the scope of the gist of the technology.

[0058] It should be noted that the effects described in this specification are merely examples and are not limiting, and other effects may also be obtained.

[0059] The present technology can also be configured as follows. (1) first and second switches that open and close complementarily; a capacitance having both ends connected to the output terminals of the first and second switches to receive power; A switching amplifier comprising: (2) a first impedance element connected between one end of the capacitance and a power supply terminal; a second impedance element connected between the other end of the capacitance and a ground terminal; The switching amplifier according to (1) above, further comprising: (3) the first switch has an input end connected to a power supply terminal and an output end connected to the other end of the capacitance; The second switch has an input terminal connected to a ground terminal and an output terminal connected to the one terminal of the capacitance. The switching amplifier according to (2) above. (4) A power combiner is further provided for combining the power of the signals supplied from both ends of the capacitance and supplying the power to a load from an output terminal. The switching amplifier according to (3) above. (5) The power combiner includes first and second capacitors, both ends of which are connected to the input terminals of the capacitance, and a terminal where the output terminals are joined is the output terminal. The switching amplifier according to (4) above. (6) The power combiner includes the first and second capacitors instead of the capacitance. The switching amplifier according to (5) above. (7) The power combiner includes a transformer instead of the first and second impedance elements. The switching amplifier according to (4) above. (8) The power combiner includes first and second gate-grounded transistors, each of which has both ends of the capacitance connected to its respective source and has a terminal connecting the drains of the first and second gate-grounded transistors as the output terminal. The switching amplifier according to (4) above. (9) The first and second switches include first and second transistors that open and close in a complementary manner. A switching amplifier according to any one of (1) to (8). (10) The first and second switches further include a first common-gate transistor cascode-connected to the first transistor and a second common-gate transistor cascode-connected to the second transistor. The switching amplifier according to (9) above. (11) The first and second switches include first and second common-gate transistors that open and close in a complementary manner. A switching amplifier according to any one of (1) to (10). (12) The first and second switches are further connected to both ends of the capacitance, and the first and second switches and the capacitance are connected in a plurality of stages. A switching amplifier according to any one of (1) to (11). [Explanation of symbols]

[0060] 110, 120 Switch 111, 112, 121, 122 Transistors 130 Buffer 131~133 Inverter 210, 220 Inductor 230 capacity 300 Power combiner 310, 320 capacity 311, 321 Trans 312, 322 transistors 390 capacity 400 Load

Claims

1. First and second switches that open and close complementarily, A capacitor having both ends connected to the output terminals of the first and second switches to receive the supply of an input power source and output an output voltage, A first impedance element connected between one end of the capacitor and a power source terminal, having a high impedance with respect to a high-frequency signal and a low impedance with respect to a low-frequency signal, A second impedance element connected between the other end of the capacitor and a ground terminal, having a high impedance with respect to the high-frequency signal and a low impedance with respect to the low-frequency signal, and comprising: A power source terminal to which the input power source is applied is connected to the input terminal of the first switch, A ground terminal is connected to the input terminal of the second switch A switching amplifier.

2. The output terminal of the first switch is connected to the other end of the capacitor, The output terminal of the second switch is connected to the one end of the capacitor The switching amplifier according to Claim 1.

3. Further comprising a power combiner that performs power combination on the output voltage supplied from both ends of the capacitor and supplies the combined power to a load The switching amplifier according to Claim 2.

4. The power combiner includes first and second capacitors having both ends of the capacitor connected to respective input terminals and their output terminals coupled, and having an output terminal as an output terminal The switching amplifier according to Claim 3.

5. The power combiner includes first and second gate-grounded transistors having both ends of the capacitor connected to respective sources and their drains coupled, and having an output terminal as an output terminal The switching amplifier according to Claim 3.

6. The first and second switches include first and second transistors that open and close complementarily The switching amplifier according to Claim 1.

7. The first and second switches further include a first gate-grounded transistor cascode-connected to the first transistor and a second gate-grounded transistor cascode-connected to the second transistor The switching amplifier according to Claim 6.

8. The first and second switches include first and second gate-grounded transistors that open and close complementarily The switching amplifier according to Claim 1.

9. The first and second switches are further connected to both ends of the capacitor, and the first and second switches and the capacitor are connected in multiple stages The switching amplifier according to Claim 1.

10. First and second switches that open and close complementarily, A power combiner in which both ends of a capacitance formed by connecting first and second capacitors in series are connected to the output ends of the first and second switches to receive the supply of an input power supply, and power combination is performed on the output voltage supplied from both ends of the capacitance to supply the combined power to a load, A first impedance element connected between one end of the capacitance and a power supply terminal, having a high impedance with respect to a high-frequency signal and a low impedance with respect to a low-frequency signal, A second impedance element connected between the other end of the capacitance and a ground terminal, having a high impedance with respect to the high-frequency signal and a low impedance with respect to the low-frequency signal, A power supply terminal to which the input power supply is applied is connected to the input end of the first switch, A ground terminal is connected to the input end of the second switch Switching amplifier.

11. First and second switches that open and close complementarily, A capacitance whose both ends are connected to the output ends of the first and second switches to receive the supply of an input power supply and output an output voltage, A power combiner that performs power combination on the output voltage supplied from both ends of the capacitance and supplies it to a load from an output terminal, The power combiner includes A first transformer having a primary winding connected between one end of the capacitance and a power supply terminal, having a high impedance with respect to a high-frequency signal and a low impedance with respect to a low-frequency signal, A second transformer having a primary winding connected between the other end of the capacitance and a ground terminal, having a high impedance with respect to the high-frequency signal and a low impedance with respect to the low-frequency signal, A power supply terminal to which the input power supply is applied is connected to the input end of the first switch, A ground terminal is connected to the input end of the second switch, The secondary winding of the first transformer and the secondary winding of the second transformer are connected in series with each other Switching amplifier.

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