A power management circuit for an RF amplifier

Abstract

This application belongs to the field of radio frequency amplifier technology, specifically an RF amplifier power management circuit, including a first bandgap reference module for generating a first reference voltage; a second bandgap reference module for generating a second reference voltage, wherein the temperature slope of the first reference voltage is higher than that of the second reference voltage; a third bandgap reference module for generating a third reference voltage; a selector for selecting either the first or second reference voltage as a fourth reference voltage for output; a low-dropout linear regulator for comparing the fourth reference voltage with a feedback voltage and adjusting the output voltage of the low-dropout linear regulator according to the comparison result; a voltage monitoring module for monitoring the power supply voltage and obtaining a sampled voltage; and a comparator for comparing the sampled voltage with the third reference voltage and outputting a temperature slope control signal. This application achieves compensation of RF amplifier characteristics under a wide range of power supply voltages and a combination of high and low temperatures.

Description

Technical Field

[0001] This application belongs to the field of radio frequency amplifier technology, specifically a power management circuit for a radio frequency amplifier. Background Technology

[0002] With the rapid development of wireless communication technology, the capacity of communication channels has expanded rapidly, and modulation technology has been continuously upgraded. This requires communication systems to provide excellent signal-to-noise ratio and linearity, which in turn places higher demands on the performance of radio frequency amplifiers in the transceiver link.

[0003] To adapt to different environmental conditions, RF amplifiers must maintain stable gain and phase responses across various power supply voltages and temperatures, achieving excellent signal quality. However, in reality, the critical characteristics of RF amplifiers change when power supply voltage and temperature vary. Therefore, a power management unit is needed to provide specific bias voltages to compensate for the RF amplifier's characteristics, such as... Figure 1 The power management unit shown is connected to the power supply voltage and can generate a temperature-dependent bias voltage. The RF amplifier has a bias voltage terminal and an RF input terminal. The bias voltage terminal is connected to the bias voltage terminal, and the RF input terminal is connected to the RF input terminal, providing the RF amplifier with the required temperature-dependent bias, thereby achieving stable gain and phase response. For example, if the RF amplifier requires a larger bias voltage at low temperatures and a smaller bias voltage at high temperatures, the power management unit generates a bias voltage with a negative temperature coefficient, whose slope as a function of temperature is negative.

[0004] However, as the power supply voltage decreases, if the temperature slope of the bias voltage remains constant, the bias voltage value may reach the limit of the power supply voltage at low temperatures. This can cause abnormalities in the bias voltage output by the power management unit, leading to RF amplifier malfunction. Therefore, in order to simultaneously meet the requirements of both temperature and power supply voltage, the bias voltage must be able to adjust in real time in accordance with both temperature and power supply voltage. Summary of the Invention

[0005] This application provides a power management circuit for an RF amplifier, which solves the problem that abnormal bias voltage output by the power management unit leads to functional failure of the RF amplifier.

[0006] This application provides an embodiment of a radio frequency amplifier power management circuit, including:

[0007] The first bandgap reference module is used to generate the first reference voltage;

[0008] A second bandgap reference module is used to generate a second reference voltage, wherein the temperature slope of the first reference voltage is higher than that of the second reference voltage.

[0009] The third bandgap reference module is used to generate the third reference voltage;

[0010] The selector is used to select either the first reference voltage or the second reference voltage as the fourth reference voltage for the output.

[0011] A low-dropout linear regulator is used to compare a fourth reference voltage with a feedback voltage and adjust the output voltage of the low-dropout linear regulator according to the comparison result. The feedback voltage is used to feed back the output voltage of the low-dropout linear regulator to the low-dropout linear regulator. The output voltage of the low-dropout linear regulator is used as the bias voltage of the RF amplifier.

[0012] The voltage monitoring module is used to monitor the voltage of the power supply and obtain the sampled voltage after sampling.

[0013] A comparator is used to compare the sampled voltage with a third reference voltage and output a temperature slope control signal, which is used as a selection signal for the selector.

[0014] Furthermore, the low-dropout linear regulator includes:

[0015] The operational amplifier receives a fourth reference voltage through its inverting input terminal and a feedback voltage through its non-inverting input terminal.

[0016] The power transistor is connected to the output of the operational amplifier through its gate, to the power supply through its source, and to the output voltage of the low-dropout linear regulator through its drain.

[0017] Furthermore, a feedback voltage is provided to the operational amplifier by connecting the common terminal of the first feedback resistor and the second feedback resistor, which are connected in series, to the non-inverting input terminal of the operational amplifier. One end of the first feedback resistor is connected to the output voltage of the low dropout linear regulator, and the other end of the first feedback resistor is connected to one end of the second feedback resistor, while the other end of the second feedback resistor is grounded.

[0018] Furthermore, when the feedback voltage is greater than the fourth reference voltage, the operational amplifier increases its output voltage, and the output voltage of the low-dropout linear regulator decreases due to the inverting amplification of the power transistor.

[0019] When the feedback voltage is less than the fourth reference voltage, the output voltage decreases, and the output voltage of the low dropout linear regulator increases due to the inverting amplification of the power transistor.

[0020] Furthermore, the comparator outputs a high-level temperature slope control signal when the sampling voltage is greater than the third reference voltage, and a low-level temperature slope control signal when the sampling voltage is less than the third reference voltage.

[0021] Furthermore, the selector selects the first reference voltage output when the temperature slope control signal is high, and selects the second reference voltage output when the temperature slope control signal is low.

[0022] Compared with the prior art, the advantages of this application are as follows:

[0023] This application selects a first reference voltage with a large temperature slope as the bias voltage (output voltage of the low-dropout linear regulator) when the power supply voltage is high, which can effectively compensate for the temperature sensitivity of the RF amplifier performance. When the power supply voltage decreases from high to low, a second reference voltage with a smaller temperature slope is selected as the bias voltage, so that the bias voltage is lower than the power supply voltage at low temperatures of -40°C, avoiding failure due to the bias voltage exceeding the power supply voltage. This achieves compensation for the RF amplifier characteristics under a wide range of power supply voltage and high / low temperature combinations, thereby improving the performance of the RF amplifier. Attached Figure Description

[0024] Figure 1 This is a block diagram of a power management unit in the prior art;

[0025] Figure 2 A circuit block diagram of the power management circuit for the radio frequency amplifier provided in an embodiment of this application;

[0026] Figure 3 The diagram shows the effect of the RF amplifier power management circuit provided in the embodiment of this application during use. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0028] In order to achieve certain RF performance (taking dynamic EVM index as an example) of RF amplifier under a wide range of power supply voltage and high and low temperature conditions, this application proposes an RF amplifier power management circuit, which adopts RF amplifier bias voltage with different temperature characteristics under different power supply voltages, and dynamically adjusts the temperature characteristics of the bias voltage in real time according to the change of power supply voltage.

[0029] like Figure 2 As shown, a power management circuit for an RF amplifier includes:

[0030] The first bandgap reference module is used to generate the first reference voltage;

[0031] The second bandgap reference module is used to generate a second reference voltage, wherein the temperature slope of the first reference voltage is higher than that of the second reference voltage.

[0032] The third bandgap reference module is used to generate the third reference voltage;

[0033] The selector is used to select either the first reference voltage or the second reference voltage as the fourth reference voltage for the output.

[0034] A low-dropout linear regulator is used to compare a fourth reference voltage with a feedback voltage and adjust the output voltage of the low-dropout linear regulator according to the comparison result. The feedback voltage is used to feed back the output voltage of the low-dropout linear regulator to the low-dropout linear regulator, and the output voltage of the low-dropout linear regulator is used as the bias voltage of the RF amplifier.

[0035] The voltage monitoring module is used to monitor the external power supply voltage and obtain the sampled voltage after sampling.

[0036] A comparator is used to compare the sampled voltage with a third reference voltage and output a temperature slope control signal, which is used as a selection signal for the selector.

[0037] The bandgap reference is generated by a bandgap reference module, which utilizes the bandgap voltage of silicon. Temperature independence is achieved by combining voltage sources with positive and negative temperature coefficients. Different temperature slopes can be achieved by adjusting the ratio between the two. The bandgap reference module can be implemented using existing structures, and the embodiments in this application do not limit the specific structure of the bandgap reference module.

[0038] This application generates two first or second reference voltages with different temperature slopes using two bandgap reference modules. One of them is set to a higher temperature slope and the other to a lower temperature slope. The temperature slope refers to the rate at which the voltage changes with temperature, and is represented by a line with a slope on the graph.

[0039] The selector here is a device that selects one of the first reference voltage and the second reference voltage as the output based on the temperature slope control signal. There are no restrictions on the model and structure of the selector. The voltage monitoring module can be implemented using mature products on the market, and there are no restrictions here.

[0040] In one embodiment, the low dropout linear regulator includes: an operational amplifier that receives a fourth reference voltage through its inverting input and a feedback voltage through its non-inverting input;

[0041] The power transistor is connected to the output of the operational amplifier through its gate, to the power supply through its source, and to the output voltage of the low-dropout linear regulator through its drain.

[0042] The operational amplifier is provided with a feedback voltage by connecting the common terminal of the first and second feedback resistors, which are connected in series, to the non-inverting input terminal of the operational amplifier. One end of the first feedback resistor is connected to the output voltage, and the other end of the first feedback resistor is connected to one end of the second feedback resistor, while the other end of the second feedback resistor is grounded.

[0043] The output voltage of the low-dropout linear regulator is divided by the first and second feedback resistors to generate a feedback voltage, which is then compared with the input of the operational amplifier to a fourth reference voltage. When the bias voltage is high, the feedback voltage is greater than the fourth reference voltage, increasing the output voltage of the operational amplifier. This increase is amplified by the power transistor, causing the output voltage of the low-dropout linear regulator to decrease. Conversely, when the bias voltage is low, the feedback voltage is less than the fourth reference voltage, decreasing the output voltage of the operational amplifier. This decrease is amplified by the power transistor, causing the output voltage of the low-dropout linear regulator to increase. Through this feedback mechanism, a constant bias voltage output is ultimately achieved.

[0044] In one embodiment, the comparator outputs a high-level temperature slope control signal when the sampled voltage is greater than the third reference voltage, and a low-level temperature slope control signal when the sampled voltage is less than the third reference voltage. The third reference voltage is a voltage signal unaffected by temperature. The temperature slope control signal generated by comparing the sampled voltage with the third reference voltage is output to the selector as the selector's selection signal. The comparator that satisfies the functions of this application has a conventional structure, and no limitation is placed on the model or structure of the comparator here.

[0045] In one embodiment, when the temperature slope control signal is high, the selector selects a first reference voltage as the fourth reference voltage output; when the temperature slope control signal is low, it selects a second reference voltage as the fourth reference voltage output.

[0046] The selector that satisfies the function of this application has a conventional structure, and there are no restrictions on the model or structure of the selector.

[0047] The working principle of the RF amplifier power management circuit in this embodiment is as follows:

[0048] The selector selects one of the voltage outputs as the fourth reference voltage. The voltage monitoring module detects the power supply voltage in real time and outputs a sampled voltage to a comparator for comparison with the third reference voltage, outputting a temperature slope control signal. The third reference voltage, generated by the third bandgap reference module, has isothermal characteristics and is used to generate the output temperature slope control signal, which is unaffected by temperature changes. When the sampled voltage is greater than the third reference voltage, the temperature slope control signal is high; when the sampled voltage is less than the third reference voltage, the temperature slope control signal is low. The temperature slope control signal controls the output signal of the selector. When the temperature slope control signal is high, the fourth reference voltage equals the first reference voltage, exhibiting a high temperature slope; when the temperature slope control signal is low, the fourth reference voltage equals the second reference voltage, exhibiting a low temperature slope. The output voltage of the low-dropout linear regulator provides a bias voltage for the RF amplifier. The temperature characteristic of the bias voltage follows the temperature characteristic of the fourth reference voltage. It should be noted that the value of the output voltage of the low-dropout linear regulator is the value of the bias voltage.

[0049] The RF amplifier power management circuit provided in this application embodiment achieves the following results during use: Figure 3 As shown, curve La represents the bias voltage versus temperature under high supply voltage, and curve Lb represents the bias voltage versus temperature under low supply voltage. From... Figure 3 As can be seen, when the power supply voltage is high, the temperature slope of the bias voltage temperature curve is large, which can effectively compensate for the temperature sensitivity of the RF amplifier performance. When the power supply voltage decreases (e.g., to 3.3V), the bias voltage temperature curve switches to curve Lb, with a smaller temperature slope. This ensures that the bias voltage value V2b at a low temperature of -40℃ is lower than the power supply voltage, preventing failure due to the bias voltage exceeding the power supply voltage. This application achieves compensation for RF amplifier characteristics under a wide range of power supply voltages and a combination of high and low temperatures, thereby improving the performance of the RF amplifier.

[0050] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A power management circuit for an RF amplifier, characterized in that, include: The first bandgap reference module is used to generate the first reference voltage; A second bandgap reference module is used to generate a second reference voltage, wherein the temperature slope of the first reference voltage is higher than that of the second reference voltage. The third bandgap reference module is used to generate the third reference voltage; The selector is used to select either the first reference voltage or the second reference voltage as the fourth reference voltage for the output. A low-dropout linear regulator is used to compare a fourth reference voltage with a feedback voltage and adjust the output voltage of the low-dropout linear regulator according to the comparison result. The feedback voltage is used to feed back the output voltage of the low-dropout linear regulator to the low-dropout linear regulator. The output voltage of the low-dropout linear regulator is used as the bias voltage of the RF amplifier. The voltage monitoring module is used to monitor the voltage of the power supply and obtain the sampled voltage after sampling. A comparator is used to compare the sampled voltage with a third reference voltage and output a temperature slope control signal. The temperature slope control signal is used as a selection signal for a selector. When the sampled voltage is greater than the third reference voltage, the temperature slope control signal output by the comparator is high, and when the sampled voltage is less than the third reference voltage, the temperature slope control signal output is low. The selector selects the first reference voltage output when the temperature slope control signal is high, and selects the second reference voltage output when the temperature slope control signal is low.

2. The RF amplifier power management circuit according to claim 1, characterized in that, The low-dropout linear regulator includes: The operational amplifier receives a fourth reference voltage through its inverting input terminal and a feedback voltage through its non-inverting input terminal. The power transistor is connected to the output of the operational amplifier through its gate, to the power supply through its source, and to the output voltage of the low-dropout linear regulator through its drain.

3. The RF amplifier power management circuit according to claim 2, characterized in that, The operational amplifier is provided with a feedback voltage by connecting the common terminal of the first and second feedback resistors, which are connected in series, to the non-inverting input terminal of the operational amplifier. One end of the first feedback resistor is connected to the output voltage of the low dropout linear regulator, and the other end of the first feedback resistor is connected to one end of the second feedback resistor, while the other end of the second feedback resistor is grounded.

4. The RF amplifier power management circuit according to claim 2, characterized in that, When the feedback voltage is greater than the fourth reference voltage, the operational amplifier increases the output voltage, and the output voltage of the low dropout linear regulator decreases due to the inverting amplification of the power transistor. When the feedback voltage is less than the fourth reference voltage, the output voltage decreases, and the output voltage of the low dropout linear regulator increases due to the inverting amplification of the power transistor.

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