Envelope tracking power supply modulator and wireless communication system thereof

Abstract

An envelope tracking power supply modulator (ETSM) and a wireless communication system are provided. A linear amplifier of the ETSM includes a pre-driver stage circuit and an output stage circuit. The pre-driver stage circuit receives an envelope input and generates a pre-driver output in accordance therewith. The output stage circuit generates an amplifier output of the linear amplifier in accordance with the pre-driver output, the amplifier output being used to set a modulated supply voltage for a power amplifier. A plurality of amplifiers of the output stage circuit includes first and second amplifiers. The first amplifier participates in setting the amplifier output when the power amplifier has a first output power level, and the second amplifier does not participate in setting the amplifier output. The first amplifier and the second amplifier participate in setting the amplifier output when the power amplifier has a second output power level that is different from the first output power level. Broad bandwidth envelope tracking is achieved with reduced quiescent current consumption, and efficiency of the power amplifier is improved.

Description

TECHNICAL FIELD

[0001] The present invention relates to envelope tracking, and more particularly, to an envelope tracking supply modulator utilizing a linear amplifier with a segmented output stage and associated wireless communication system. BACKGROUND

[0002] Power amplifiers (PAs) are used to amplify radio-frequency (RF) signals for radio transmission. PAs are commonly found in wireless communication devices for driving the antennas of transmitters. The power consumption of a PA is critical for wireless communication devices that are powered by batteries. Traditionally, PAs are biased using a fixed supply voltage. When the RF input signal to the PA is at maximum level, a peak RF output power is typically present. However, when the PA backs off from the peak RF output power condition, the excess input power is necessarily dissipated by the PA as it is not converted into useful RF output power. That is, the conventional fixed PA supply voltage results in a significant amount of power loss as heat. Envelope tracking is a technique that dynamically modulates the supply voltage of a PA with the envelope of the RF input signal. This will cause the PA to be closer to the peak level at all times, significantly improving the efficiency of the PA. That is, the envelope tracking technique modulates the PA supply voltage to track the envelope of the RF input signal, thereby reducing the amount of power dissipated as heat.

[0003] In wireless communications, the bandwidth is the range of frequencies occupied by a modulated carrier signal. As wireless communication technology advances, the bandwidth used by a modulated carrier signal is becoming wider and wider. Therefore, an envelope tracking supply modulator for providing a modulated supply voltage to a PA requires a linear amplifier with wide bandwidth. However, a typical linear amplifier usually consumes a large amount of quiescent current to achieve a wider envelope tracking bandwidth. Therefore, a typical wide bandwidth envelope tracking design is very power-hungry.

[0004] Therefore, there is a need for an innovative design to achieve wide bandwidth envelope tracking with reduced quiescent current consumption. SUMMARY

[0005] It is therefore an object of the present invention to provide an envelope tracking supply modulator and associated wireless communication system that utilizes a linear amplifier with a segmented output stage to address the above problems.

[0006] According to a first aspect of the present disclosure, an example envelope tracking power supply modulator is disclosed. The example envelope tracking power supply modulator includes a linear amplifier. The linear amplifier includes a pre-driver stage circuit and an output stage circuit. The pre-driver stage circuit is configured to receive an envelope input and generate a pre-driver output based on the envelope input. The output stage circuit is configured to receive the pre-driver output and generate an amplifier output of the linear amplifier based on the pre-driver output, wherein the amplifier output is configured to set a modulated supply voltage of a power amplifier. The output stage circuit has a plurality of amplifiers, including a first amplifier and a second amplifier. When the power amplifier has a first output power level, the first amplifier is involved in setting the amplifier output and the second amplifier is not involved in setting the amplifier output. When the power amplifier has a second output power level that is different from the first output power level, the first amplifier and the second amplifier are involved in setting the amplifier output.

[0007] According to a second aspect of the present disclosure, an example envelope tracking power supply modulator is disclosed. The example envelope tracking power supply modulator includes a linear amplifier. The linear amplifier includes a pre-driver stage circuit and an output stage circuit. The pre-driver stage circuit is configured to receive an envelope input and generate a pre-driver output based on the envelope input. The output stage circuit is configured to receive the pre-driver output and generate an amplifier output based on the pre-driver output, wherein the amplifier output is involved in setting a modulated supply voltage of a power amplifier. The output stage circuit has a plurality of amplifiers, the output stage circuit selects one or more amplifiers from the plurality of amplifiers to generate the amplifier output, and a number of amplifiers selected from the plurality of amplifiers to be involved in setting the amplifier output under a first condition is different from a number of amplifiers selected from the plurality of amplifiers to be involved in setting the amplifier output under a second condition, wherein the power amplifier has a second output power level under the second condition that is different from a first output power level of the power amplifier under the first condition.

[0008] According to a third aspect of the present application, an exemplary wireless communication system is disclosed. The exemplary wireless communication system comprises a transmit (TX) circuit, an envelope tracking circuit, and a modulator / demodulator circuit. The TX circuit is configured to receive a TX baseband signal, generate a radio frequency signal based on the TX baseband signal, and output the radio frequency signal through a power amplifier. The envelope tracking circuit is configured to derive an envelope input from the TX baseband signal, and generate a modulated power supply voltage based on the envelope input. The envelope tracking circuit comprises an envelope tracking power supply modulator. The envelope tracking power supply modulator comprises a linear amplifier. The linear amplifier comprises a pre-driver stage circuit and an output stage circuit. The pre-driver stage circuit is configured to receive the envelope input, and generate a pre-driver output based on the envelope input. The output stage circuit is configured to receive the pre-driver output, and generate an amplifier output of the linear amplifier based on the pre-driver output, wherein the amplifier output participates in setting the modulated power supply voltage of the power amplifier. The output stage circuit has a plurality of amplifiers, including a first amplifier and a second amplifier. The modulator / demodulator circuit is configured to generate the TX baseband signal, generate a control signal based on an output power level of the power amplifier, and output the control signal to the output stage circuit. The modulator / demodulator circuit comprises a TX power detection circuit configured to detect the output power level of the power amplifier. In response to the control signal, the output stage circuit is configured to select one or more amplifiers from the plurality of amplifiers to generate the amplifier output; when the power amplifier has a first output power level, the first amplifier participates in setting the amplifier output and the second amplifier does not participate in setting the amplifier output; when the power amplifier has a second output power level different from the first output power level, the first amplifier and the second amplifier participate in setting the amplifier output.

[0009] The present application can achieve wide bandwidth envelope tracking with reduced quiescent current consumption, and improve the efficiency of the power amplifier.

[0010] These and other objects of the present application will no doubt become obvious to one of ordinary skill in the art after reading the following detailed description of the preferred embodiment, which is illustrated in a number of drawings. BRIEF DESCRIPTION OF DRAWINGS

[0011] Figure 1 is a block diagram illustrating an envelope tracking power supply modulator according to an embodiment of the present application.

[0012] Figure 2 is a waveform diagram of a modulated power supply voltage V PA of a PA in different power modes according to an embodiment of the present application.

[0013] Figure 3 is a circuit diagram illustrating an AB class amplifier used by an output stage circuit according to an embodiment of the present application.

[0014] Figure 4is a diagram illustrating the relationship between the quiescent current LA IQ of a LA (whose output stage has only two amplifiers) and the load current VPA IL of a PA according to an embodiment of the application.

[0015] Figure 5 is a diagram illustrating the relationship between the quiescent current LA IQ of a LA (whose output stage has more than two amplifiers) and the load current VPA IL of a PA according to an embodiment of the application.

[0016] Figure 6 is a circuit diagram illustrating an adjustable compensation circuit according to an embodiment of the application.

[0017] Figure 7 is a block diagram illustrating a wireless communication system according to an embodiment of the application.

[0018] Figure 8 is a block diagram illustrating another envelope tracking supply modulator according to an embodiment of the application. DETAILED DESCRIPTION

[0019] Certain terms are used throughout the description and claims to refer to particular components. As one skilled in the art will appreciate, electronic equipment manufacturers can refer to a component by different names. This document does not intend to distinguish between components that differ in name but not in function. In the following description and in the claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "including, but not limited to." Also, the term "couple" or "coupled" as used herein is intended to mean either an indirect or direct electrical connection. Thus, if a first device is electrically connected to a second device, that connection can be through one or more intervening devices, or directly, without any intervening devices.

[0020] Figure 1 is a block diagram illustrating an envelope tracking supply modulator (ETSM) according to an embodiment of the application. The ETSM 100 is configured to generate a modulated supply voltage V ENV from an envelope input S PA and to provide the modulated supply voltage V PA to a power amplifier (PA) 101. The PA 101 is powered by the modulated supply voltage V PA and is configured to amplify a radio frequency (RF) signal S RFto generate an output PA OUT having a desired TX power. In this embodiment, the ETSM 100 employs a hybrid ETSM architecture, and comprises a DC-DC converter 102 and a linear amplifier (LA) 104. The DC-DC converter 102 is arranged to generate and output a regulated direct current (DC) voltage V DC to an output port N3 of the ETSM 100 via an inductor L DC . For example, the DC-DC converter 102 can be implemented by a buck converter. The LA 104 is arranged to receive an envelope input S ENV , and to generate an amplifier output V AC , the amplifier output V AC being output to the output port N3 of the ETSM 100 via an alternating current (AC) coupling capacitor C AC . The regulated DC voltage V DC and the amplifier output V AC jointly control a modulated supply voltage V PA of the PA 101. Specifically, the regulated DC voltage V DC determines a DC portion of the modulated supply voltage V PA , and the amplifier output V AC determines an AC portion of the modulated supply voltage V PA .

[0021] Figure 2 is a waveform diagram of the modulated supply voltage V PA of the PA 101 in different power modes according to an embodiment of the present application. When the PA 101 is operating in a high power mode PC2 (power class 2), a DC portion VPArms (VPArms = 3.2V) of the modulated supply voltage V PA is set by the regulated DC voltage V DC , and an AC portion of the modulated supply voltage V PA is set by the amplifier output V AC . When the PA 101 is operating in a low power mode PC3 (power class 3), a DC portion VPArms (VPArms = 2.4V) of the modulated supply voltage V PA is set by the regulated DC voltage V DC , and an AC portion of the modulated supply voltage V PA is set by the amplifier output V AC .

[0022] The LA 104 includes a pre-driver stage circuit 106 and an output stage circuit 108. The pre-driver stage circuit 106 is configured to receive an envelope input S ENV and generate a pre-driver output S ENV in accordance with the envelope input S PRE Any available pre-driver design can be used to implement the pre-driver stage circuit 106. Since the present application focuses on the output stage design, further description of the pre-driver stage circuit 106 is omitted for brevity.

[0023] It is noted that, for brevity, Figure 1 only components relevant to the present application are shown in FIG. 1. In practice, the ETSM 100 can include additional components depending on actual design considerations. For example, the DC-DC converter 102 and the LA 104 form an envelope tracking modulator (ETM), and the envelope input S ENV is provided to the ETM (specifically, the LA 104) by an analog filter (not shown) in the ETSM 100.

[0024] As mentioned above, a typical wide-bandwidth envelope tracking design is very power hungry due to the need for large quiescent current. To address this issue, the present application proposes an envelope tracking power modulator that uses a linear amplifier with a segmented output stage. As shown in Figure 1 The output stage circuit 108 includes a plurality of amplifiers 110_1-110_N, each coupled between an input port N1 and an output port N2 of the output stage circuit 108, where N is a positive integer no less than 1 (i.e., N≥2). For example, the output stage circuit 108 can be designed to have only two amplifiers 110_1 and 110_N (N=2). For another example, the output stage circuit 108 can be designed to have more than two amplifiers 110_1-110_N (N>2). In short, the output stage circuit 108 can be viewed as being segmented into a plurality of amplifiers, where the number of amplifiers can be adjusted depending on actual design considerations.

[0025] In the present embodiment, each of the amplifiers 110_1-110_N can be implemented by a class-AB amplifier. Figure 3 is a circuit diagram illustrating a class-AB amplifier used by the output stage circuit 108 according to an embodiment of the present application. One or more of the amplifiers 110_1-110_N can be implemented using the class-AB amplifier design shown in Figure 3 The class-AB amplifier 300 operates at a supply voltage V BBand a ground voltage GND, which includes a plurality of P-type metal oxide semiconductor (PMOS) transistors M10 and M12, a plurality of N-type metal oxide semiconductor (NMOS) transistors M11 and M13, and a plurality of buffers BUF1 and BUF2. In this embodiment, PMOS transistor M12 and NMOS transistor M13 are core devices with thin gate oxide, and PMOS transistor M10 and NMOS transistor M11 are input / output (I / O) devices with thick gate oxide. The pre-driver output S PRE is a differential signal composed of Vgp and Vgn. Thus, the input port N1 of the output stage circuit 108 includes a first node and a second node, where the first node is coupled to the gate of PMOS transistor M12, and the second node is coupled to the gate of NMOS transistor M13. The gate voltage of PMOS transistor M10 is set by the buffer BUF1 to a reference voltage V refp . The gate voltage of NMOS transistor M11 is set by the buffer BUF2 to another reference voltage V refn . The drain of PMOS transistor M10 and the drain of NMOS transistor M11 are coupled to the output port N2 of the output stage circuit 108. Thus, when the AB class amplifier 300 is enabled by the output stage circuit 108, the AB class amplifier 300 outputs an amplifier output V PRE at the output port N2 of the output stage circuit 108 according to the pre-driver output S AC at the input port N1 of the output stage circuit 108.

[0026] It is noted that, Figure 3 the circuit structure shown is for illustrative purposes only and is not meant to limit the present application. For example, one or more of the amplifiers 110_1-110_N can be implemented using another AB class amplifier design.

[0027] In one exemplary segmented output stage implementation, the amplifiers 110_1-110_N can be identical amplifiers and thus have the same output drive capability. In another exemplary implementation, the amplifiers 110_1-110_N can be different amplifiers. For example, the amplifiers 110_1-110_N can have the same circuit design but different transistor sizes and thus have different output drive capabilities. As another example, the amplifiers 110_1-110_N can have different circuit designs and thus have different output drive capabilities.

[0028] The amplifier output V AC The modulation supply voltage V PA In this embodiment, the output stage circuit 108 selects one or more of the amplifiers 110_1-110_N to generate the amplifier output V AC For better understanding of the proposed TX power based quiescent current reduction technique, the following assumptions are made that the output stage circuit 108 can be designed to have only two amplifiers 110_1 and 110_N (N=2). When the PA 101 has a first output power level, the amplifier 110_1 is used to set the amplifier output V AC while the amplifier 110_N (N=2) is not used to set the amplifier output V AC When the PA 101 has a second output power level different from the first output power level, both the amplifiers 110_1 and 110_N (N=2) are used to set the amplifier output V AC For example, when the PA 101 has the first output power level, the amplifier 110_N (N=2) is disabled, while when the PA 101 has the second output power level higher than the first output power level, the amplifier 110_N (N=2) is enabled, at which time the amplifier output V AC is greater than the amplifier output V AC when the amplifier 110_N (N=2) is disabled. Thus, the quiescent current of the LA 104 is smaller under the first condition (the PA 101 has the first output power level) than under the second condition (the PA 101 has the second output power level higher than the first output power level). In this way, the efficiency of the ETSM 100 can be improved for mid-range and low TX power.

[0029] Figure 4 is a schematic diagram illustrating the relationship between the quiescent current LA IQ of the LA 104 (whose output stage has only two amplifiers) and the load current VPA IL of the PA 101 according to an embodiment of the present application. The quiescent current LA IQ of the LA 104 is controlled by the transistors. The load current VPA IL of the PA 101 is positively correlated with the output power level of the PA 101. The TX power of the PA 101 is segmented into two non-overlapping output power ranges R1 and R2, where the maximum output power level within the output power range R1 is lower than the minimum output power level within the output power range R2.

[0030] The characteristic curve CV1 represents when the LA 104 generates the amplifier output V ACVPA IL vs. LA IQ with PA 101 in low power mode. The characteristic curve CV2 represents the relationship between the load current VPA IL of the PA 101 and the quiescent current LA IQ of the LA 104 in the case where the PA 101 is in low power mode. The characteristic curve CV3 represents the relationship between the load current VPA IL of the PA 101 and the quiescent current LA IQ of the LA 104 in the case where the PA 101 is in high power mode. The characteristic curve CV3 can be obtained when the proposed TX power based quiescent current reduction technique is used. The characteristic curve CV3 represents that for any output power level within the output power range R1, the LA 104 enables only one amplifier 110_1 and uses it to set the amplifier output V AC , and for any output power level within the output power range R2, the LA 104 enables all amplifiers 110_1 and 110_N (N=2) and uses them to set the amplifier output V AC . AC VPA IL vs. LA IQ with PA 101 in low power mode. The characteristic curve CV2 represents the relationship between the load current VPA IL of the PA 101 and the quiescent current LA IQ of the LA 104 in the case where the PA 101 is in low power mode. The characteristic curve CV3 represents the relationship between the load current VPA IL of the PA 101 and the quiescent current LA IQ of the LA 104 in the case where the PA 101 is in high power mode. The characteristic curve CV3 can be obtained when the proposed TX power based quiescent current reduction technique is used. The characteristic curve CV3 represents that for any output power level within the output power range R1, the LA 104 enables only one amplifier 110_1 and uses it to set the amplifier output V

[0031] When the output power level of the PA 101 is any output power level in the output power range R1 (e.g., the PA 101 is operating in low power mode), the amplifier 110_1 is enabled and the amplifiers 110_N (N=2) are disabled, such that only one of the amplifiers 110_1 and 110_N (N=2) is involved in setting the amplifier output V AC . AC The output stage circuit 108 is configured to modulate the supply voltage V PA ) for the amplifiers 110_1 and 110_N (N=2) to set the amplifier output V PA . AC When the TX power level is low, the quiescent current of the LA 104 is reduced. Therefore, for medium and low TX power, the ETSM efficiency can be improved.

[0032] Alternatively, the output stage circuit 108 can be designed to have more than two amplifiers 110_1-110_N (N>2). The same concept of using a segmented output stage to reduce the LA quiescent current and improve the ETSM efficiency can be used. Figure 5 is a schematic diagram illustrating the relationship between the quiescent current LA IQ of the LA 104 (whose output stage has more than two amplifiers) and the load current VPA IL of the PA 101 according to an embodiment of the present application. The TX power of the PA 101 is segmented into N non-overlapping output power ranges R1, R2, …, R N-1 , RN wherein the maximum output power level within the output power range R1 is lower than the minimum output power level within the output power range R2, the maximum output power level within the output power range R2 is lower than the minimum output power level within the higher output power range, and so on.

[0033] Characteristic curve CV1 represents the relationship between the load current VPA IL of the PA 101 and the quiescent current LA IQ of the LA 104 in the case where the LA 104 uses only one amplifier 110 1 to generate the amplifier output V AC Characteristic curve CV2' represents the relationship between the load current VPA IL of the PA 101 and the quiescent current LA IQ of the LA 104 in the case where the LA 104 uses all amplifiers 110 1-110 N (N > 2) to generate the amplifier output V AC Characteristic curve CV3' represents the relationship between the load current VPA IL of the PA 101 and the quiescent current LA IQ of the LA 104 in the case where the proposed TX power based quiescent current reduction technique is used. Characteristic curve CV3' represents that for different output power ranges R1-R N of the PA 101, the LA 104 has different combinations of amplifiers enabled and participating in setting the amplifier output V AC , respectively. For example, when the output power level of the PA 101 is any output power level belonging to the output power range R i (1 < i < N), the amplifiers 110 1-110 i are enabled and participating in setting the modulated supply voltage V PA with contribution to the amplifier output V AC , while the amplifiers 110 (i+1)-110 N are disabled and do not participate in setting the amplifier output V AC .

[0034] In other words, in response to the output power level of the PA 101, the output stage circuit 108 selects one or more amplifiers from the amplifiers 110 1-110 N to generate the amplifier output V AC For example, under a first condition where the PA 101 has a first output power level, the number of amplifiers selected from the amplifiers 110 1-110 N to participate in setting the amplifier output V AC is less than the number of amplifiers selected from the amplifiers 110 1-110 N to participate in setting the amplifier output V AC under a second condition (the PA 101 has a second output power level different from (e.g., higher than) the first output power level).

[0035] In addition to the amplifiers 110_1-110_N, the output stage circuit 108 can include an adjustable compensation circuit 112 for changing its compensation setting when the number of participating amplifiers setting the amplifier output V AC changes due to a change in the output power level of the PA 101. Figure 6 is a circuit diagram illustrating an adjustable compensation circuit according to an embodiment of the present application. By way of example, but not limitation, Figure 1 the adjustable compensation circuit 112 shown in FIG. 1 can be implemented by Figure 6 the adjustable compensation circuit 600 shown in FIG. 6. The adjustable compensation circuit 600 is coupled between an input port N1 and an output port N2 of the output stage circuit 108, and includes a plurality of resistors R1, R2 and a plurality of variable capacitors C1, C2. The pre-driver output S PRE provided to the input port N1 of the output stage circuit 108 is a differential signal composed of V gp and V gn . Thus, the input port N1 of the output stage circuit 108 includes a first node and a second node, where the first node is coupled to one end of the resistor R1 and the second node is coupled to one end of the resistor R2. The capacitance values of the variable capacitors C1 and C2 can be dynamically adjusted to change the compensation setting of the adjustable compensation circuit 600. That is, the plurality of resistors R1, R2 and the plurality of variable capacitors C1, C2 are coupled in parallel between the outputs of the amplifiers 110_1-110_N and the output port N2 of the output stage circuit 108 to form the feedback resistors and capacitors of the amplifiers. For example, when the output power level of the PA changes and the number of participating amplifiers setting the amplifier output V AC changes, if the capacitance values are fixed, the stability of the amplifier output (e.g., signal jitter, etc.) can be degraded. By adjusting the capacitance values of the variable capacitors when different numbers of amplifiers participate in setting the amplifier output V AC , the stability of the amplifier output can be improved. For example, when the PA 101 has a first output power level, the adjustable compensation circuit 600 is configured to have a first compensation setting (e.g., a first capacitance value setting) optimized for the output stage circuit 108. When the PA 101 has a second output power, the adjustable compensation circuit 600 is configured to have a second compensation setting (e.g., a second capacitance value setting) optimized for the output stage circuit 108, where the second compensation setting is different from the first compensation setting due to the adjustment of the capacitance values via the variable capacitors C1 and C2.

[0036] It is noted that the adjustable compensation circuit 112 can be optional. For example, the output stage circuit 108 can be modified to replace the adjustable compensation circuit 112 with a compensation circuit having a fixed compensation setting. Any envelope tracking power supply modulator using a linear amplifier with a segmented output stage falls within the scope of the present application.

[0037] Figure 7 is a block diagram illustrating a wireless communication system according to an embodiment of the present application. For example, the wireless communication system 700 can be a 5G-NR system or a 4G-LTE system, and the envelope tracking power supply modulator of the wireless communication system 700 can have a digitally controlled linear amplifier with a segmented output stage for RF transmitter efficiency optimization. As shown in Figure 7 the wireless communication system 700 includes a transmit (TX) circuit 702, an envelope tracking circuit 704, and a modulator / demodulator circuit (labeled "MODEM") 706. The modulator / demodulator circuit 706 can be part of a digital baseband circuit. The TX circuit 702 is configured to receive a TX baseband signal TX_BB from the modulator / demodulator circuit 706, generate an RF signal S RF from the TX baseband signal TX_BB, and output the RF signal S RF to an antenna 701 via a power amplifier (PA) 720. For example, the TX baseband signal TX_BB is a digital signal, the RF signal S RF is an analog signal, and the TX circuit 702 includes a TX digital front-end circuit (labeled "TX DFE") 712, a digital-to-analog converter (DAC) 714 (in-phase (I) path), a digital-to-analog converter (DAC) 716 (quadrature (Q) path), an RF circuit (labeled "TX RF") 718, and the PA 720. The TX digital front-end circuit 712 can include a digital pre-distortion module, an up-sampling module (I path), an up-sampling module (Q path), etc. The RF circuit 718 can include an analog filter (I path), an analog filter (Q path), an up-converter, etc.

[0038] The envelope tracking circuit 704 is configured to derive an envelope input S ENV from the TX baseband signal TX_BB, and generate a modulated supply voltage V ENV from the envelope input S PA . For example, the TX baseband signal TX_BB is a digital signal, the envelope input S ENVThe signal is analog. The envelope tracking circuit 704 includes an envelope tracking digital baseband circuit (labeled "ETDBB") 722, a DAC 724, and an envelope tracking power supply modulator (ETSM) 726, wherein the ETSM 726 includes an analog filter 728 and an envelope tracking modulator (ETM) 730. The envelope tracking digital baseband circuit 722 may include an envelope detection block, a power scaling block, a lookup table, an upsampling block, etc.

[0039] Figure 7 The PA 720 shown can be Figure 1 The PA 101 shown. ETSM 726 (specifically, ETM 730) can be used... Figure 1 The hybrid ETSM architecture shown is used for implementation. Therefore, the ETM 730 can include... Figure 1 The DC-DC converter 102 and linear amplifier 104 are shown. In this embodiment, the ETSM 726 can automatically adjust based on digital detection of the TX power level to optimize system efficiency. Figure 7 As shown, the modulator / demodulator circuit 706 includes a TX power detection circuit 732, which is arranged to perform digital detection of the TX power level. The TX power detection circuit 732 can receive the output PA_OUT of PA 720 via coupler 708 and a receive (RX) path, and can detect the output power level of PA 720 (i.e., the TX power of the wireless communication system 700) by, for example, processing the output PA_OUT in the digital domain. Based on the detected output power level of PA 720, the modulator / demodulator circuit 706 generates a control signal S_CTRL and outputs the control signal S_CTRL to ETSM 726 (specifically, the output stage circuit 108 of LA104). In response to the control signal S_CTRL, the output stage circuit 108 selects one or more amplifiers from amplifiers 110_1-110_N to generate the amplifier output V. AC And / or configure the compensation settings of the adjustable compensation circuit 112.

[0040] exist Figure 1 In the illustrated embodiment, LA 104 in ETSM 100 is coupled to capacitor C via AC coupling. AC It is coupled to output port N3. However, this is for illustrative purposes only and does not imply any limitation on the invention. Figure 8 This is a block diagram illustrating another envelope tracking power supply modulator according to an embodiment of the present invention. The main difference between ETSM 800 and ETSM 100 is that LA108 of ETSM 800 is not coupled to the output port N3 through any AC coupling capacitor. In other words, the amplifier output V ACIt is directly coupled to the output port N3. This enables the use of regulated DC voltage V. DC and amplifier output V AC The modulation power supply voltage V of PA 101 is jointly controlled. PA For the same purpose. Since those skilled in the art can easily understand the details of ETSM 800 after reading the above content regarding ETSM 100, further description is omitted here for brevity. Furthermore, regarding Figure 7 The wireless communication system 700 shown, ETSM 726 (specifically, ETSM 730), can be used by Figure 8 The hybrid ETSM architecture shown is used for implementation. Therefore, the ETM 730 can include... Figure 8 The DC-DC converter 102 and linear amplifier 104 are shown.

[0041] Those skilled in the art will readily understand that various modifications and changes can be made to the apparatus and method while retaining the teachings of the present invention. Therefore, the foregoing should be interpreted as being limited only by the scope and limits of the appended claims.

Claims

1. An envelope tracking power supply modulator, comprising: Linear amplifiers, including: A pre-driver stage circuit for receiving an envelope input and generating a pre-driver output based on the envelope input; and An output stage circuit is configured to receive the pre-driver output and generate the amplifier output of the linear amplifier based on the pre-driver output, wherein the amplifier output is used to set the modulation supply voltage of the power amplifier, and the output stage circuit includes: A plurality of amplifiers, including a first amplifier and a second amplifier, wherein when the power amplifier has a first output power level, the first amplifier participates in setting the amplifier output, while the second amplifier does not participate in setting the amplifier output; when the power amplifier has a second output power level different from the first output power level, the first amplifier and the second amplifier participate in setting the amplifier output. Wherein, under the first condition that the power amplifier has the first output power level, the quiescent current of the linear amplifier is different from the quiescent current of the linear amplifier under the second condition that the power amplifier has the second output power level.

2. The envelope tracking power modulator as claimed in claim 1, wherein the second output power level is higher than the first output power level.

3. The envelope tracking power modulator of claim 1, wherein the first output power level is lower than the second output power level, and the quiescent current of the linear amplifier under the first condition is less than the quiescent current of the linear amplifier under the second condition.

4. The envelope tracking power modulator as claimed in claim 1, wherein the first output power level is any value among a plurality of output power levels within a first output power range of the power amplifier, the second output power level is any value among a plurality of output power levels within a second output power range of the power amplifier, and the first output power range and the second output power range do not overlap.

5. The envelope tracking power modulator of claim 1, wherein the second amplifier is disabled when the power amplifier has the first output power level, and the second amplifier is enabled when the power amplifier has the second output power level.

6. The envelope tracking power modulator as claimed in claim 1, wherein, The first amplifier and the second amplifier are either the same amplifier or different amplifiers.

7. The envelope tracking power modulator of claim 1, wherein the pre-driver output is received at the input port of the output stage circuit, and the amplifier output is generated at the output port of the output stage circuit, wherein the output stage circuit further comprises: An adjustable compensation circuit is coupled between the output port and the input port of the output stage circuit, wherein when the power amplifier has the first output power level, the adjustable compensation circuit is configured to have a first compensation setting; when the power amplifier has the second output power level, the adjustable compensation circuit is configured to have a second compensation setting different from the first compensation setting.

8. The envelope tracking power modulator of claim 1, wherein the modulated power supply voltage of the power amplifier is generated at the output port of the envelope tracking power modulator, and the output stage circuit outputs the amplifier output to the output port of the envelope tracking power modulator without any AC coupling capacitor.

9. An envelope tracking power supply modulator, comprising: Linear amplifiers, including: Pre-driver stage circuitry for receiving envelope input and generating pre-driver output based on the envelope input; and An output stage circuit is configured to receive the pre-driver output and generate an amplifier output based on the pre-driver output, wherein the amplifier output is used to set the modulation supply voltage of the power amplifier, and the output stage circuit includes: A plurality of amplifiers, wherein the output stage circuitry is configured to select one or more amplifiers from the plurality of amplifiers to generate the amplifier output, and the number of amplifiers selected from the plurality of amplifiers to participate in setting the amplifier output under a first condition is different from the number of amplifiers selected from the plurality of amplifiers to participate in setting the amplifier output under a second condition, wherein the power amplifier has a second output power level under the second condition is different from the power amplifier has a first output power level under the first condition; The quiescent current of the linear amplifier under the first condition is different from the quiescent current of the linear amplifier under the second condition.

10. The envelope tracking power modulator as claimed in claim 9, wherein, The first output power level is lower than the second output power level.

11. The envelope tracking power modulator of claim 9, wherein the first output power level is lower than the second output power level, and the quiescent current of the linear amplifier under the first condition is less than the quiescent current of the linear amplifier under the second condition.

12. The envelope tracking power modulator of claim 9, wherein the first output power level is any value among a plurality of output power levels within a first output power range of the power amplifier, the second output power level is any value among a plurality of output power levels within a second output power range of the power amplifier, and the first output power range and the second output power range do not overlap.

13. The envelope tracking power modulator of claim 9, wherein the plurality of amplifiers are the same amplifier or different amplifiers.

14. The envelope tracking power modulator of claim 9, wherein the pre-driver output is received at an input port of the output stage circuit, the amplifier output is generated at an output port of the output stage circuit, and the output stage circuit further comprises: An adjustable compensation circuit is coupled between the output port and the input port of the output stage circuit, wherein when the power amplifier has the first output power level, the adjustable compensation circuit is configured to have a first compensation setting; when the power amplifier has the second output power level, the adjustable compensation circuit is configured to have a second compensation setting different from the first compensation setting.

15. The envelope tracking power modulator of claim 9, wherein the modulated power supply voltage of the power amplifier is generated at the output port of the envelope tracking power modulator, and the output stage circuit outputs the amplifier output to the output port of the envelope tracking power modulator without any AC coupling capacitor.

16. A wireless communication system, comprising: A TX transmitting circuit is used to receive a TX baseband signal, generate an RF signal based on the TX baseband signal, and output the RF signal via a power amplifier; An envelope tracking circuit is used to derive an envelope input from the TX baseband signal and generate a modulation power supply voltage based on the envelope input. The envelope tracking circuit includes an envelope tracking power supply modulator, which includes a linear amplifier comprising: A pre-driver stage circuit for receiving the envelope input and generating a pre-driver output based on the envelope input; and An output stage circuit is configured to receive the pre-driver output and generate the amplifier output of the linear amplifier based on the pre-driver output, wherein the amplifier output is used to set the modulation supply voltage of the power amplifier, and the output stage circuit includes a plurality of amplifiers, including a first amplifier and a second amplifier; and A modulator / demodulator circuit is used to generate the TX baseband signal, generate a control signal based on the output power level of the power amplifier, and output the control signal to the output stage circuit, wherein the modulator / demodulator circuit includes: A TX power detection circuit is used to detect the output power level of the power amplifier; wherein, in response to the control signal, the output stage circuit is used to select one or more amplifiers from the plurality of amplifiers to generate the amplifier output; when the power amplifier has a first output power level, the first amplifier participates in setting the amplifier output, and the second amplifier does not participate in setting the amplifier output; when the power amplifier has a second output power level different from the first output power level, the first amplifier and the second amplifier participate in setting the amplifier output; wherein, under the first condition that the power amplifier has the first output power level, the quiescent current of the linear amplifier is different from the quiescent current of the linear amplifier under the second condition that the power amplifier has the second output power level.

17. The wireless communication system of claim 16, wherein, The number of amplifiers selected from the plurality of amplifiers to participate in setting the amplifier output under the first condition that the power amplifier has the first output power level is different from the number of amplifiers selected from the plurality of amplifiers to participate in setting the amplifier output under the second condition that the power amplifier has the second output power level.

18. The wireless communication system of claim 16, wherein the first output power level is lower than the second output power level.

19. The wireless communication system of claim 16, wherein the modulated power supply voltage of the power amplifier is generated at the output port of the envelope tracking power modulator, and the output stage circuit outputs the amplifier output to the output port of the envelope tracking power modulator without any AC coupling capacitor.

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