A control circuit for controlling output power of a power amplifier

Abstract

The present invention discloses a control circuit for controlling the output power of a power amplifier, the control circuit comprising: a bias circuit, generating a bias current according to an input control voltage, the bias current being coupled to the input end of the power amplifier; an output voltage control circuit, adjusting the output voltage according to the input control voltage, the output voltage being coupled to the output end of the power amplifier. The control circuit provided by the present invention controls the output power of the power amplifier by converting voltage into current using the bias circuit, thereby achieving the purpose of controlling the output power of the power amplifier by the control voltage, avoiding the use of expensive off-chip precision resistors, and saving costs.

Description

Technical Field

[0001] The invention relates to a control circuit for controlling the output power of a power amplifier. Background Art

[0002] A power amplifier is a device that can amplify the voltage or power of an input signal. It is composed of electron tubes or transistors, power transformers and other electrical components. It is widely used in various devices such as communications, broadcasting, radar, television, and automatic control.

[0003] The output power of the power amplifier needs to be controlled within a specific range. Taking the cellular data RF front end of a mobile phone as an example, its power amplifier system currently needs to output up to 33dBm of power. The battery needs to provide ampere-level current to the power amplifier. If the output power of the power amplifier is not properly controlled, it is easy to cause serious heat dissipation problems. Summary of the invention

[0004] In order to solve the problems existing in the prior art, an object of the present invention is to provide a control circuit for controlling the output power of a power amplifier which can effectively control the output power of the power amplifier and save costs.

[0005] To achieve the purpose of the present invention, a control circuit for controlling the output power of a power amplifier provided herein comprises:

[0006] A bias circuit generates a bias current according to an input control voltage, wherein the bias current is coupled to an input terminal of the power amplifier;

[0007] The output voltage control circuit adjusts the output voltage according to the input control voltage, and the output voltage is coupled to the output end of the power amplifier.

[0008] Furthermore, the bias circuit includes a voltage-controlled current source, which generates a bias current that is exponentially related to the control voltage, and the bias current is coupled to an input terminal of the power amplifier.

[0009] Furthermore, the voltage-controlled current source includes an operational amplifier M1, a field effect transistor Q1, a field effect transistor Q2 and a field effect transistor Q3, the control voltage is loaded on the reverse input terminal of the operational amplifier M1, the forward input terminal of the operational amplifier M1 is connected to the drains of the field effect transistor Q1 and the field effect transistor Q2, the gate of the field effect transistor Q2 is connected to the gate of the field effect transistor Q3 and is connected to the drain of the field effect transistor Q2; the drain of the field effect transistor Q3 serves as an output terminal to output a bias current.

[0010] Furthermore, the output voltage control circuit includes a control voltage detection module and a power supply module; the control voltage detection module detects the control voltage and outputs a comparison voltage; the power supply module outputs an output voltage to the output end of the power amplifier according to the comparison voltage, wherein the output voltage is positively correlated with the comparison voltage.

[0011] Furthermore, the power supply module is an LDO module or a DCDC module.

[0012] Furthermore, the power supply module includes a comparator M2, a field effect transistor Q4 and a field effect transistor Q5, the comparison voltage output by the control voltage detection module is loaded on the non-inverting input terminal of the comparator M2, the inverting input terminal of the comparator M2 is grounded via a resistor R1, and the output terminal of the comparator M2 is connected to the gates of the field effect transistor Q4 and the field effect transistor Q5; the field effect transistor Q4 is grounded via the resistor R1, the source of the field effect transistor Q5 is grounded, and the drain of the field effect transistor Q5 is connected to the output terminal of the power amplifier as an output terminal.

[0013] Furthermore, an LC circuit is included, and the output voltage of the power supply module is coupled to the output end of the power amplifier via the LC circuit.

[0014] The beneficial effects of the present invention include:

[0015] 1) The control circuit provided by the present invention controls the output power of the power amplifier by converting voltage into current using a bias circuit, thereby achieving the purpose of controlling the output power of the power amplifier by a control voltage, avoiding the use of expensive off-chip precision resistors, and saving costs.

[0016] 2) By using the output voltage control circuit, the output voltage is controlled in different power modes, thereby achieving the purpose of reducing or increasing the output power of the power amplifier. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The drawings herein are incorporated into and constitute a part of the specification, showing embodiments consistent with the present invention, and together with the specification, are used to explain the principles of the present invention. Obviously, the drawings described below are only some embodiments of the present invention, and for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0018] Figure 1 A circuit diagram of a control circuit provided by the present invention;

[0019] Figure 2 A circuit diagram of a voltage-controlled current source provided by the present invention;

[0020] Figure 3A circuit diagram of a power supply module provided by the present invention;

[0021] In the attached figure: 1- bias circuit, 2- control voltage detection module, 3- power supply module. DETAILED DESCRIPTION

[0022] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that the present invention will be more comprehensive and complete and fully convey the concept of the example embodiments to those skilled in the art.

[0023] In order to control the output power of the power amplifier, the present invention provides a control circuit for controlling the output power of the power amplifier. Figure 1 As shown, it includes a bias circuit 1, which generates a bias current according to an input control voltage, and the bias current is coupled to the input end of the power amplifier; and an output voltage control circuit, which adjusts the output voltage according to the input control voltage, and the output voltage is coupled to the output end of the power amplifier.

[0024] The control circuit converts the control voltage into a bias current through the bias circuit 1, and the bias current controls the output power of the power amplifier; the output voltage of the power amplifier is controlled through the output voltage control circuit, and the output voltage also realizes the control of the output power of the power amplifier.

[0025] Herein, the bias circuit 1 includes a voltage-controlled current source, which generates a bias current exponentially related to a control voltage, and the bias current is coupled to the input terminal of the power amplifier. The circuit structure of the voltage-controlled current source is as follows: Figure 2 As shown, it includes an operational amplifier M1, a field effect transistor Q1, a field effect transistor Q2 and a field effect transistor Q3, a control voltage is loaded on the reverse input terminal of the operational amplifier M1, a forward input terminal of the operational amplifier M1 is connected to the drains of the field effect transistors Q1 and Q2, a gate of the field effect transistor Q2 is connected to the gate of the field effect transistor Q3 and is connected to the drain of the field effect transistor Q2; the drain of the field effect transistor Q3 is used as an output terminal to output a bias current.

[0026] In this article, the output voltage control circuit includes a control voltage detection module 2 and a power supply module 3; the control voltage detection module 2 detects the control voltage and outputs a comparison voltage; the power supply module 3 outputs an output voltage to the output end of the power amplifier according to the comparison voltage output by the control voltage detection module 2, wherein the output voltage is positively correlated with the comparison voltage. Among them, the control voltage detection module 2 compares the control voltage with the reference voltage. When the control voltage is greater than the reference voltage, the control voltage detection module 2 outputs a larger comparison voltage to control the power supply module 3 to increase the output voltage, thereby achieving the purpose of providing the output power of the power amplifier; when the control voltage is less than the reference voltage, the control voltage detection module 2 outputs a smaller comparison voltage to control the power supply module 3 to reduce the output voltage, thereby achieving the purpose of reducing the output power of the power amplifier.

[0027] The power supply module 3 in this article is an LDO module or a DCDC module. Here, an LDO module is used as the power supply module. Figure 3 As shown, the LDO module includes a comparator M2, a field effect transistor Q4 and a field effect transistor Q5, the comparison voltage output by the control voltage detection module is loaded on the non-inverting input terminal of the comparator M2, the inverting input terminal of the comparator M2 is grounded via a resistor R2, the output terminal of the comparator M2 is connected to the gates of the field effect transistors Q4 and Q5; the source of the field effect transistor Q4 is grounded via a resistor R1, the source of the field effect transistor Q5 is directly grounded, the drain of the field effect transistor Q4 and the source of the field effect transistor Q5 are connected to the power supply VCC; the drain of the field effect transistor Q5 is connected to the output terminal of the power amplifier as an output terminal. The control voltage detection module 2 compares the control voltage with the reference voltage. When the control voltage is greater than the reference voltage, the control voltage detection module 2 outputs a larger voltage to control the power supply module 3 to increase the output voltage.

[0028] For better matching, the output voltage of the power supply module 3 is coupled to the output end of the power amplifier via an LC circuit.

[0029] The control principle of the control circuit provided in this article is: power = voltage x current, so controlling the output voltage or current of the power amplifier can control the output power.

[0030] The control circuit provided in this paper controls the output power of the power amplifier by controlling the output voltage and output current of the output stage transistor T1 of the power amplifier. Figure 1 In the figure, PA represents a power amplifier, TI represents an output-stage transistor of the power amplifier, and the output-stage transistor of the power amplifier refers to the stage with the largest current and the largest power in the power amplifier.

[0031] Reference Figure 1As shown, the bias current output by the bias circuit 1 is loaded on the base of the output stage transistor T1 of the power amplifier. Since the collector current is proportional to the base current, when the control voltage of the input bias circuit 1 changes, the output bias current changes accordingly, and the purpose of controlling the output power is achieved through the bias current method. The output voltage of the output voltage control circuit is coupled to the collector of the output stage transistor T1 of the power amplifier. The output voltage of the output voltage control circuit is adjusted according to the input control voltage, and the purpose of controlling the output power is achieved through the voltage method.

[0032] The bias circuit 1, control voltage detection module 2 and power supply module 3 described in this article are integrated on a CMOS or SOI chip to achieve on-chip control; the control voltage in this article is provided by an external circuit.

[0033] The control circuit provided in this article controls power by changing the base current as the main means, and the output voltage change of the output voltage control circuit is an auxiliary means. It mainly controls the low-voltage and high-voltage sections of the voltage to achieve low power consumption (low-voltage section) or high power (high-voltage section).

[0034] The present disclosure has been described by the above-mentioned relevant embodiments, but the above-mentioned embodiments are only examples for implementing the present disclosure. It must be pointed out that the disclosed embodiments do not limit the scope of the present disclosure. On the contrary, changes and modifications made without departing from the spirit and scope of the present disclosure are all within the scope of patent protection of the present disclosure.

Claims

1. A control circuit for controlling the output power of a power amplifier, characterized in that: include: A bias circuit generates a bias current according to an input control voltage, wherein the bias current is coupled to an input terminal of the power amplifier; The bias circuit includes a voltage-controlled current source, the voltage-controlled current source generates a bias current that is exponentially related to the control voltage, and the bias current is coupled to an input terminal of the power amplifier; An output voltage control circuit, which adjusts the output voltage according to the input control voltage, wherein the output voltage is coupled to the output terminal of the power amplifier; The output voltage control circuit comprises a control voltage detection module and a power supply module, wherein the control voltage detection module detects the control voltage and outputs a comparison voltage; the power supply module outputs an output voltage to the output end of the power amplifier according to the comparison voltage, wherein the output voltage is positively correlated with the comparison voltage; The voltage-controlled current source comprises an operational amplifier M1, a field effect transistor Q1, a field effect transistor Q2 and a field effect transistor Q3, the control voltage is loaded on the reverse input terminal of the operational amplifier M1, the forward input terminal of the operational amplifier M1 is connected to the drain of the field effect transistor Q1, the output of the operational amplifier M1 is connected to the gate of the field effect transistor Q1, and the source of the field effect transistor Q1 is grounded; the source of the field effect transistor Q2 is connected to the power supply VCC, the drain is connected to the drain of the field effect transistor Q1, and the gate is connected to the gate of the field effect transistor Q3; the drain and the gate of the field effect transistor Q2 are short-circuited; the gate of the field effect transistor Q3 is connected to the power supply VCC, and the drain serves as an output terminal to output a bias current.

2. The control circuit for controlling the output power of a power amplifier according to claim 1, characterized in that: The power supply module is an LDO module or a DCDC module.

3. The control circuit for controlling the output power of a power amplifier according to claim 1, characterized in that: The power supply module includes a comparator M2, a field effect transistor Q4 and a field effect transistor Q5. The comparison voltage output by the control voltage detection module is loaded on the non-inverting input terminal of the comparator M2. The inverting input terminal of the comparator M2 is grounded via a resistor R1 and connected to the source of the field effect transistor Q4. The output terminal of the comparator M2 is connected to the gate of the field effect transistor Q4 and the gate of the field effect transistor Q5. The drain of the field effect transistor Q4 is connected to the power supply VCC, the source of the field effect transistor Q5 is connected to the power supply VCC, and the drain is connected to the output terminal of the power amplifier as an output terminal.

4. The control circuit for controlling the output power of a power amplifier according to claim 1, characterized in that: It also includes an LC circuit, and the output voltage of the power supply module is coupled to the output end of the power amplifier via the LC circuit.

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