Switching amplifier

Abstract

The present invention increases the output voltage of a switching amplifier in the case of a limited supply voltage. The switching amplifier is provided with a first switch and a second switch which are turned on and off in a complementary manner, and a capacitor whose terminals are used as inputs of a power combiner. The terminals of the capacitor are connected to the output terminals of the first switch and the second switch. Depending on the operation of the first switch and the second switch, the capacitor receives a supply from the power supply. As a result, the load in the capacitor is used as a charge pump, which alternately steps up or steps down the output voltage via the operating frequency of the switching amplifier, thereby generating a rectangular voltage with a controlled wave height.

Description

Technical Field

[0001] This technology relates to switching amplifiers. Specifically, this technology relates to boost or buck switching amplifiers. Background Technology

[0002] Two types of switching amplifiers are generally known: Class D amplifiers and Class E amplifiers. Switching amplifiers are, in principle, highly efficient; therefore, in recent years, they have been increasingly used as communication amplifiers in mobile devices. However, due to the increase in mobile devices, communication conditions have deteriorated. Therefore, there is a need to increase the output power of power amplifiers. However, there is an upper limit to the voltage of batteries used in mobile devices, such as lithium-ion batteries. With a fixed supply voltage to the amplifier, it is necessary to reduce the impedance of the amplifier and the load and increase the amplifier's output current to increase the amplifier's output power. Reducing circuit impedance and increasing output current to increase output power is generally disadvantageous in terms of efficiency. For example, losses due to parasitic resistance in the wiring increase proportionally with the increase in output current. Furthermore, when the load impedance decreases, the number of matching components increases, and signal insertion loss generally increases. That is, Class D amplifiers, which directly output the supply voltage, have the side effect of increased losses due to increased output current when increasing output power. In contrast, in Class E amplifiers, even with a limited supply voltage, the resonant impedance of the matching circuit is designed to be high, allowing for a higher output voltage and increased output power without increasing the output current.

[0003] In this respect, Class E amplifiers can be considered excellent amplifiers with low loss for achieving high output power. However, the boost level of the output voltage of a Class E amplifier is highly dependent on the resonant impedance of the matching circuit. Here, consider the case where the antenna of the transmitter using a Class E amplifier is close to metal. Due to the close contact between the antenna and the metal, the antenna impedance can deviate significantly from the standard value of 50 ohms. When the antenna impedance changes, the resonant impedance of the matching circuit of the Class E amplifier changes. The output voltage of the Class E amplifier is unexpectedly boosted due to the change in resonant impedance, and the amplifier may malfunction. That is, in order to achieve a low-loss, high-output amplifier, the boost operation of the output voltage is effective so as not to increase the output current, but the boost amount needs to be controlled to a constant value regardless of the external environment. In view of this, charge pump circuits have been proposed as a representative technique for achieving controlled boost (see, for example, Patent Document 1).

[0004] Reference List

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2015-164386 Summary of the Invention

[0007] The problem to be solved by the present invention

[0008] According to the charge pump circuit described above, a constant amount of charge is stored in the capacitor using the rectification effect of diodes or switching elements, and the boost voltage can be controlled to be constant. However, power losses occur in the diodes or switching elements when the capacitor is charged. Furthermore, power consumption related to the control of the switching elements occurs. That is, when the voltage is boosted by a common charge pump, the boost voltage is controlled to be constant, but the area, power loss, and power consumption controlled by circuit elements other than the amplifier increase. Furthermore, Class D amplifiers using both negative and positive power supplies are also commonly used, which is equivalent to controlling the boost voltage to be constant. However, such Class D amplifiers require a power supply circuit to generate the negative voltage, increasing both the area and power consumption. As mentioned above, there is a problem: when the amplifier's output power increases under limited power supply voltage conditions, power consumption increases or the amplifier's reliability is compromised.

[0009] Given this situation, this technique has been implemented, and its purpose is to increase the output voltage of a switching amplifier when the power supply voltage is limited.

[0010] Solution to the problem

[0011] This technology is designed to solve the aforementioned problems, and its first aspect provides a switching amplifier comprising: a first switch and a second switch that are turned on and off in a complementary manner; and a capacitor whose two ends are connected to the output terminals of the first switch and the second switch, the capacitor receiving power from a power source.

[0012] Furthermore, the switching amplifier according to the first aspect 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. This configuration provides the effect of supplying power to the capacitor via the first and second impedance elements to charge the capacitor.

[0013] Furthermore, in the switching amplifier according to the first aspect, the first switch may have an input terminal connected to a power supply terminal and an output terminal connected to the other end of a capacitor, and the second switch may have an input terminal connected to a ground terminal and an output terminal connected to one end of a capacitor.

[0014] Furthermore, the switching amplifier according to the first aspect may further include a power synthesizer that combines the power of signals supplied from both ends of a capacitor and supplies the combined power from an output terminal to a load.

[0015] Furthermore, in the switching amplifier according to the first aspect, the power synthesizer may include a first capacitor and a second capacitor, the input terminals of the first capacitor and the second capacitor being respectively connected to the two ends of a capacitor, and the output terminals of the first capacitor and the second capacitor being connected to each other to form a terminal serving as an output terminal. Therefore, the effect of realizing a power synthesizer having a first capacitor and a second capacitor is provided.

[0016] Furthermore, in the switching amplifier according to the first aspect, the power synthesizer may include a first capacitor and a second capacitor instead of a capacitor. This configuration provides the effect of giving the first and second capacitors of the power synthesizer the function of a capacitor.

[0017] Furthermore, in the switching amplifier according to the first aspect, the power synthesizer may include a transformer instead of the first and second impedance elements. This configuration provides the effect of achieving a power synthesizer with a transformer.

[0018] Furthermore, in the switching amplifier according to the first aspect, the power combiner may include a first common-gate transistor and a second common-gate transistor, the sources of which are connected to the two ends of a capacitor, and the drains of which are connected to each other to form a terminal serving as an output terminal. This configuration provides the effect of setting the voltage of the combined power to be the same as the source voltage by allowing the common-gate transistor to act as a switch.

[0019] Furthermore, in the switching amplifier according to the first aspect, the first switch and the second switch may include a first transistor and a second transistor that are turned on and off in a complementary manner. This configuration provides the effect of implementing the first switch and the second switch using the first transistor and the second transistor.

[0020] Furthermore, in the switching amplifier according to the first aspect, the first switch and the second switch may further have a first common-gate transistor connected to the first transistor in a common-source, common-gate configuration and a second common-gate transistor connected to the second transistor in a common-source, common-gate configuration. This configuration provides the effect of voltage division for the voltage applied to each transistor.

[0021] Furthermore, in the switching amplifier according to the first aspect, the first switch and the second switch may include a first common-gate transistor and a second common-gate transistor that are turned on and off in a complementary manner. This configuration provides the effect of voltage division for the voltage applied to each transistor.

[0022] Furthermore, in the switching amplifier according to the first aspect, the first switch and the second switch can be further connected to both ends of a capacitor, and the first switch and the second switch can be connected to the capacitor in multiple stages. This configuration provides the effect of increasing the voltage of the final output. Attached Figure Description

[0023] Figure 1 This is a diagram illustrating an example of a basic configuration of a switching amplifier according to an embodiment of the present technology.

[0024] Figure 2 This is a diagram illustrating an example of the overall configuration of a switching amplifier according to an embodiment of the present technology.

[0025] Figure 3 This is a diagram illustrating an example of the output waveform of a switching amplifier according to an embodiment of the present technology.

[0026] Figure 4 This is a diagram illustrating a modified example of a switching amplifier according to an embodiment of the present technology.

[0027] Figure 5 This is a diagram illustrating a first example of a switching amplifier according to an embodiment of the present technology.

[0028] Figure 6 This is a diagram illustrating a second example of a switching amplifier according to an embodiment of the present technology.

[0029] Figure 7 This is a diagram illustrating a third example of a switching amplifier according to an embodiment of the present technology.

[0030] Figure 8 This is a diagram illustrating a fourth example of a switching amplifier according to an embodiment of the present technology.

[0031] Figure 9 This is a diagram illustrating a fifth example of a switching amplifier according to an embodiment of the present technology.

[0032] Figure 10 This is a diagram illustrating a sixth example of a switching amplifier according to an embodiment of the present technology.

[0033] Figure 11 This is a diagram illustrating a seventh example of a switching amplifier according to an embodiment of the present technology.

[0034] Figure 12 This is a diagram illustrating an eighth example of a switching amplifier according to an embodiment of the present technology. Detailed Implementation

[0035] The modes of implementing this technology (hereinafter referred to as implementation methods) will be described below. The descriptions will be given in the following order.

[0036] 1. Basic Configuration

[0037] 2. Example

[0038] <1. Basic Configuration>

[0039] [Configuration of the switching amplifier]

[0040] Figure 1 This is a diagram illustrating 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 capacitor 230.

[0041] Switches 110 and 120 are switched on and off in a complementary manner. The output terminal of switch 110 is connected to the negative terminal of capacitor 230. Additionally, a power supply terminal is connected to the input terminal of switch 110, as described later. The output terminal of switch 120 is connected to the positive terminal of capacitor 230. Furthermore, as described later, a ground terminal is connected to the input terminal of switch 120.

[0042] Inductors 210 and 220 are examples of impedance elements through which the DC current used to charge capacitor 230 passes. Inductor 210 is connected between the positive terminal of capacitor 230 and the power supply terminal. Inductor 220 is connected between the negative terminal of capacitor 230 and ground. In this example, inductors 210 and 220 are shown as examples of impedance elements, but other elements can be used. In this case, the impedance element needs to have high impedance for high-frequency signals and low impedance for low-frequency signals (DC current). Furthermore, the impedance element needs to be unaffected by the voltage range of the power supply potential and the ground potential, i.e., it should not be voltage dependent.

[0043] Capacitor 230 is a component that stores charge within inductors 210 and 220 and functions as a charge pump. That is, in this switching amplifier, the charge stored in capacitor 230 is used to control the boost and buck of the output voltage.

[0044] Figure 2 This is a diagram illustrating an example of the overall configuration of a switching amplifier according to an embodiment of the present technology.

[0045] The switching amplifier is included in the power synthesizer 300, a subsequent stage in the basic configuration described above. Furthermore, a power supply terminal is connected to the input of switch 110, and a ground terminal is connected to the input of switch 120.

[0046] The power synthesizer 300 combines the power of the signals supplied from both ends of the capacitor 230 and supplies the combined power from the output terminal to the load 400.

[0047] The amount of charge stored in capacitor 230 in a steady state is determined by the voltage applied to capacitor 230 and its capacitance value. Therefore, the boost and buck amounts of the output voltage of the power synthesizer 300 are controlled to constant values. The charge stored in capacitor 230 is used as a charge pump and is used to alternately boost or deboost the output voltage at the operating frequency of the switching amplifier.

[0048] [Output of the switching amplifier]

[0049] Figure 3 This is a diagram illustrating an example of the output waveform of a switching amplifier according to an embodiment of the present technology.

[0050] exist Figure 3 In this circuit, the voltage at the positive terminal of capacitor 230 is called V_N, and the current flowing through the positive terminal of capacitor 230 is called I_N. Furthermore, the voltage at the negative terminal of capacitor 230 is called V_P, and the current flowing through the negative terminal of capacitor 230 is called I_P. Figure 3 The part 'a' represents the voltage V_P at the negative terminal of capacitor 230. Figure 3 The part b represents the voltage V_N at the positive terminal of capacitor 230. Figure 3 The part 'c' represents the current I_P flowing through switch 110. Figure 3 The part d represents the current I_N flowing through switch 120.

[0051] In state (1), switch 110 is on and switch 120 is off. In this case, the voltage V_P at the negative terminal of capacitor 230 is equal to the power supply voltage VDD. Furthermore, due to the stored charge, a potential difference VDD is generated across capacitor 230, causing the voltage V_N at the positive terminal of capacitor 230 to have a potential twice that of VDD.

[0052] In state (2), switch 110 is off and switch 120 is on. In this case, the voltage V_N at the positive terminal of capacitor 230 is equal to the ground potential. In addition, due to the stored charge, a potential difference VDD is generated across capacitor 230, causing the voltage V_P at the negative terminal of capacitor 230 to have a potential of -VDD.

[0053] Therefore, since switches 110 and 120 are connected across capacitor 230 and are turned on and off in a complementary manner to repeat the configuration of states (1) and (2), a rectangular voltage with a controlled wave height in a Class D amplifier is generated. That is, the voltage rises at the positive terminal of capacitor 230 and gradually decreases at the negative terminal of capacitor 230, and the corresponding nodes have rectangular voltages with the same phase and an amplitude of 2VDD.

[0054] As a result, the currents I_P and I_N flowing through switches 110 and 120 have a push-pull relationship. The power synthesizer 300 will generate a power combination in this manner. Therefore, the current flowing through load 400 has a combination... Figure 3 The sine wave is obtained by using c and d in the equation.

[0055] [Variation Example]

[0056] Figure 4 This is a diagram illustrating a modified example of a switching amplifier according to an embodiment of the present technology.

[0057] In this variation, multiple basic configurations of the aforementioned switching amplifiers can be cascaded. That is, switches 110 and 120 can be further connected across capacitor 230, and switches 110, 120, and capacitor 230 can be connected in multiple stages. This allows for an increase in the final output voltage.

[0058] <2. Implementation Method>

[0059] [First Embodiment]

[0060] Figure 5 This is a diagram illustrating a first example of a switching amplifier according to an embodiment of the present technology.

[0061] In this first example, the power synthesizer 300 includes capacitors 310 and 320. That is, in the first example, the power synthesizer 300 is implemented via capacitive coupling. In this case, no direct current flows, and only the alternating current component is transmitted to the load 400.

[0062] [Second Example]

[0063] Figure 6 This is a diagram illustrating a second example of a switching amplifier according to an embodiment of the present technology.

[0064] The second example has a configuration obtained by removing capacitor 230 from the configuration of the first example. In this case, capacitors 310 and 320 of the power synthesizer 300 have a function similar to that of capacitor 230. That is, capacitors 310 and 320 connected in series act as capacitor 230 and achieve capacitive coupling with load 400. Therefore, capacitor 390 between power synthesizer 300 and load 400 can be eliminated.

[0065] [Third Example]

[0066] Figure 7 This is a diagram illustrating a third example of a switching amplifier according to an embodiment of the present technology.

[0067] In this third example, the power synthesizer 300 includes transformers 311 and 321. That is, in the third example, the power synthesizer 300 includes inductors 210 and 220 and is magnetically coupled (transformer coupled) to the load 400.

[0068] Therefore, in the third embodiment, it is possible not only to convert the AC component but also to convert the DC component.

[0069] [Fourth Example]

[0070] Figure 8 This is a diagram illustrating a fourth example of a switching amplifier according to an embodiment of the present technology.

[0071] In the fourth example, the power synthesizer 300 includes MOS transistors 312 and 322. The source of transistor 312 is connected to the positive terminal of capacitor 230, and its base is connected to a power supply terminal. Furthermore, the source of transistor 322 is connected to the negative terminal of capacitor 230, and its base is connected to a ground terminal. The drains of transistors 312 and 322 are connected to each other and to a load 400 via capacitor 390.

[0072] As a result, in the fourth example, MOS transistors 312 and 322 are used as switches, and the maximum and minimum values ​​of the combined power voltage can be set to be the same as the maximum and minimum values ​​of the input voltage.

[0073] [Fifth Case]

[0074] Figure 9 This is a diagram illustrating a fifth example of a switching amplifier according to an embodiment of the present technology.

[0075] In the fifth example, switches 110 and 120 include common-source transistors 111 and 121. An AC signal is input to the gates of transistors 111 and 121 via a buffer 130, and transistors 111 and 121 function as switches that are turned on and off in a complementary manner according to the AC signal.

[0076] [Sixth Case]

[0077] Figure 10 This is a diagram illustrating a sixth example of a switching amplifier according to an embodiment of the present technology.

[0078] In the sixth example, switches 110 and 120 include transistors 111, 112, 121, and 122. Here, transistors 111 and 112 are connected in a common-source, common-gate configuration. That is, the common-source transistor 111 and the common-gate transistor 112 are connected. Similarly, transistors 121 and 122 are also connected in a common-source, common-gate configuration. As a result, the voltage applied to each transistor can be divided, thereby protecting each transistor.

[0079] [Seventh Case]

[0080] Figure 11 This is a diagram illustrating a seventh example of a switching amplifier according to an embodiment of the present technology.

[0081] In the seventh example, switches 110 and 120 include inverters 131 and 132 instead of transistors 111 and 121 in the sixth example above. This allows for a more precise voltage division applied to each transistor compared to the sixth example.

[0082] [Eighth Case]

[0083] Figure 12 This is a diagram illustrating an eighth example of a switching amplifier according to an embodiment of the present technology.

[0084] The eighth instance is provided with an inverter 133 obtained by integrating inverters 131 and 132 from the seventh instance described above. However, the two are logically equivalent.

[0085] As described above, according to the embodiments of this technology, charge is stored in capacitor 230 via inductors 210 and 220, and switches 110 and 120 are turned on and off in a complementary manner, so that capacitor 230 can act as a charge pump. Therefore, a rectangular voltage with controlled waveform height can be generated, and the output voltage of the switching amplifier can be increased when the power supply voltage is limited.

[0086] The output current and output voltage waveforms of the switching amplifier according to this technology are the same as those of a Class D amplifier. However, compared to a conventional Class D amplifier, the output voltage is boosted more, thereby increasing the output power. When the voltage charging capacitor 230 is VDD, as in the example above, the amplitude of the output voltage doubles, thus quadrupling the output power. Although the output power quadruples, the switching size of the amplifier remains unchanged, so the input power used to drive the amplifier remains unchanged. That is, the power boost efficiency (the power efficiency obtained by dividing the ratio of output power to input power by the power consumption), a performance indicator of the power amplifier, is significantly increased. Furthermore, the unchanged switching size of the amplifier helps to reduce the chip area.

[0087] It should be noted that the above embodiments illustrate examples of the present technology, and the matters in the embodiments correspond to the inventive designations in the claims. Similarly, the inventive designations in the claims correspond to matters in the embodiments of the present technology that are represented by the same names as the inventive designations. However, the present technology is not limited to the embodiments, and can be embodied by making various modifications to the embodiments without departing from its spirit.

[0088] Furthermore, the effects described in this specification are illustrative rather than limiting, and may have additional effects.

[0089] It should be noted that this technology may also have the following configurations.

[0090] (1) A switching amplifier, comprising:

[0091] The first and second switches are switched on and off in a complementary manner; and

[0092] The capacitor has its two ends connected to the output terminals of the first and second switches, and it receives power from the power source.

[0093] (2) The switching amplifier according to (1) above further includes:

[0094] The first impedance element is connected between one end of the capacitor and the power supply terminal; and

[0095] The second impedance element is connected to the other end of the capacitor and the ground terminal.

[0096] (3) The switching amplifier described in (2) above,

[0097] The first switch has an input terminal connected to a power supply terminal and an output terminal connected to the other end of a capacitor; and

[0098] The input terminal of the second switch is connected to the ground terminal, and the output terminal of the second switch is connected to one end of the capacitor.

[0099] (4) The switching amplifier according to (3) above further includes:

[0100] A power synthesizer combines the power of signals supplied from both ends of a capacitor and supplies the combined power to the load from the output terminal.

[0101] (5) The switching amplifier described in (4) above,

[0102] The power synthesizer includes a first capacitor and a second capacitor. The input terminals of the first capacitor and the second capacitor are respectively connected to the two ends of the capacitor, and the output terminals of the first capacitor and the second capacitor are connected to each other to form a terminal used as an output terminal.

[0103] (6) The switching amplifier described in (5) above,

[0104] The power synthesizer includes a first capacitor and a second capacitor, but not a full capacitor.

[0105] (7) The switching amplifier described in (4) above,

[0106] The power synthesizer includes a transformer, rather than a first impedance element and a second impedance element.

[0107] (8) The switching amplifier described in (4) above,

[0108] The power synthesizer includes a first common-gate transistor and a second common-gate transistor. The sources of the first common-gate transistor and the second common-gate transistor are connected to the two ends of a capacitor, and the drains of the first common-gate transistor and the second common-gate transistor are connected to each other to form a terminal used as an output terminal.

[0109] (9) The switching amplifier according to any one of (1) to (8) above,

[0110] The first switch and the second switch include a first transistor and a second transistor that are turned on and off in a complementary manner.

[0111] (10) The switching amplifier according to (9) above,

[0112] The first switch and the second switch further have a first common gate transistor connected to the first transistor via a common source and a second common gate transistor connected to the second transistor via a common source and a common gate.

[0113] (11) The switching amplifier according to any one of (1) to (10) above,

[0114] The first switch and the second switch include a first common-gate transistor and a second common-gate transistor that are turned on and off in a complementary manner.

[0115] (12) The switching amplifier according to any one of (1) to (11) above,

[0116] The first switch and the second switch are further connected to the two ends of the capacitor, and the first switch and the second switch are connected to the capacitor in multiple stages.

[0117] List of reference numerals

[0118] 110, 120 switches

[0119] Transistors 111, 112, 121, and 122

[0120] 130 buffer

[0121] Inverters 131 to 133

[0122] 210 and 220 inductors

[0123] 230 capacitor

[0124] 300 Electric Synthesizer

[0125] 310 and 320 capacitors

[0126] Transformers 311 and 321

[0127] 312 and 322 transistors

[0128] 390 capacitor

[0129] 400 load.

Claims

1. A switching amplifier, comprising: The first switch and the second switch are turned on and off in a complementary manner; as well as A capacitor, the two ends of which are connected to the output terminals of the first switch and the second switch, receives power from the power source. The first impedance element is connected between one end of the capacitor and the power supply terminal; and The second impedance element is connected between the other end of the capacitor and the ground terminal; The input terminal of the first switch is connected to the power supply terminal, and the output terminal of the first switch is connected to the other end of the capacitor; and The input terminal of the second switch is connected to the ground terminal, and the output terminal of the second switch is connected to one end of the capacitor.

2. The switching amplifier according to claim 1, further comprising: The power synthesizer combines the power from the signals supplied from both ends of the capacitor and supplies the combined power to the load from the output terminal.

3. The switching amplifier according to claim 2, in, The power synthesizer includes a first capacitor and a second capacitor. The input terminals of the first capacitor and the second capacitor are respectively connected to the two ends of the capacitor, and the terminal formed by connecting the output terminals of the first capacitor and the second capacitor to each other is used as the output terminal.

4. The switching amplifier according to claim 3, in, The power synthesizer includes the first capacitor and the second capacitor in place of the capacitor.

5. The switching amplifier according to claim 2, in, The power synthesizer includes a transformer, replacing the first impedance element and the second impedance element.

6. The switching amplifier according to claim 2, in, The power synthesizer includes a first common-gate transistor and a second common-gate transistor. The source of the first common-gate transistor and the source of the second common-gate transistor are connected to the two ends of the capacitor, and the terminal formed by connecting the drain of the first common-gate transistor and the drain of the second common-gate transistor to each other is used as the output terminal.

7. The switching amplifier according to claim 1, in, The first switch and the second switch include a first transistor and a second transistor that are turned on and off in a complementary manner.

8. The switching amplifier according to claim 7, in, The first switch and the second switch further have a first common-gate transistor connected to the first transistor in a common-source, common-gate manner and a second common-gate transistor connected to the second transistor in a common-source, common-gate manner.

9. The switching amplifier according to claim 1, in, The first switch and the second switch include a first common-gate transistor and a second common-gate transistor that are turned on and off in a complementary manner.

10. The switching amplifier according to claim 1, in, The first switch and the second switch are further connected to the two ends of the capacitor, and the first switch and the second switch are connected to the capacitor in multiple stages.

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