US-20260128715-A1 - CLOSED LOOP POWER CONTROL

US20260128715A1US 20260128715 A1US20260128715 A1US 20260128715A1US-20260128715-A1

Abstract

A control system is configured to control an output power of a power amplifier. The control system is operable to detect when the power amplifier is in first state and responsively provide first additional bias to the power amplifier. The first additional bias assists or enables the power amplifier in increasing the output power. The control system is also operable to detect when the power amplifier is in a second state and responsively provide second additional bias to the power amplifier. The second additional bias assists or enables the power amplifier in increasing the amount of output power.

Inventors

Søren Deleuran Laursen

Assignees

QORVO US, INC.

Dates

Publication Date: 20260507
Application Date: 20260105

Claims (14)

1 . A control system, comprising: a detector circuit connected to an output of a power amplifier, the detector circuit operable to detect a reverse voltage and output a detector signal that provides an indication of a state of the power amplifier; an amplifier circuit configured to output a bias control voltage dependent upon a voltage input to the control system, and the detector signal; a first bias circuit connected to the power amplifier, the first bias circuit operable to provide first additional bias to the power amplifier when the power amplifier is detected to be in an early saturation state by adjusting a voltage output from the first bias circuit; a second bias circuit connected to the power amplifier, the second bias circuit operable to provide second additional bias to the power amplifier when the power amplifier is detected to be in a saturation state; and a saturation correction circuit, operable to: when the power amplifier is detected to be in the early saturation state, cause flow of current from the voltage output from the first bias circuit to pass through a resistor to increase the detector signal when the voltage output from the first bias circuit exceeds a threshold voltage set based on the bias control voltage and a power supply voltage for control system; and when the power amplifier is detected to be in the saturation state, cause flow of current from the voltage output from the first bias circuit to increase the detector signal without passing through the resistor, when the voltage output from the first bias circuit exceeds a second, higher, threshold based on the bias control voltage.
2 . The control system of claim 1 , wherein: the power amplifier comprises a driver amplifier and a final amplifier; the first bias circuit is connected to the driver amplifier; and the second bias circuit is connected to the final amplifier.
3 . The control system of claim 2 , further comprising a third bias circuit connected to the driver amplifier of the power amplifier.
4 . The control system of claim 2 , wherein the driver amplifier is a multistage driver amplifier.
5 . The control system of claim 1 , wherein the detector circuit is further operable to detect a forward voltage.
6 . The control system of claim 5 , wherein the detector circuit comprises a first diode and a second diode connected to a directional coupler.
7 . The control system of claim 1 , further comprising a scaling circuit connected to the detector circuit, the scaling circuit adjustable to support multiple radio frequency bands.
8 . The control system of claim 1 , further comprising a saturation correction circuit connected to the power amplifier, the saturation correction circuit providing a first feedback path and a second feedback path.
9 . The control system of claim 1 , further comprising a feedback circuit connected to the power amplifier, the feedback circuit operable to output a feedback signal that causes additional bias to be provided to the power amplifier.
10 . A radio frequency (RF) system, comprising: RF input circuitry connected to a power amplifier; RF output circuitry connected to the power amplifier; and a control system comprising: a detector circuit connected to an output of the power amplifier, the detector circuit operable to detect a reverse voltage and output a detector signal that provides an indication of a state of the power amplifier; an amplifier circuit configured to output a bias control voltage dependent upon a voltage input to the control system, and the detector signal; a first bias circuit connected to the power amplifier, the first bias circuit operable to provide a first additional bias to the power amplifier when the power amplifier is detected to be in an early saturation state by adjusting a voltage output from the first bias circuit; a second bias circuit connected to the power amplifier, the second bias circuit operable to provide a second additional bias to the power amplifier when the power amplifier is detected to be in a saturation state; and a saturation correction circuit, operable to: when the power amplifier is detected to be in the early saturation state, cause flow of current from the voltage output from the first bias circuit to pass through a resistor to increase the detector signal when the voltage output from the first bias circuit exceeds a threshold voltage set based on the bias control voltage and a power supply voltage for the control system; and when the power amplifier is detected to be in the saturation state, cause flow of current from the voltage output from the first bias circuit to increase the detector signal without passing through the resistor, when the voltage output from the first bias circuit exceeds a second, higher, threshold based on the bias control voltage.
11 . The RF system of claim 10 , wherein the RF input circuitry comprises a transceiver and/or an antenna.
12 . A method of operating a control system in an electronic device, the method comprising: determining a power amplifier is in an early saturation state based on a first signal level of a detector signal that is output from a detector circuit connected to an output of the power amplifier, the detector circuit operable to detect a forward voltage and a reverse voltage; providing the detector signal as a feedback signal to an amplifier circuit that generates a bias control voltage based on the detector signal and a voltage input to the control system; based on determining the power amplifier is in the early saturation state, providing first additional bias to the power amplifier; determining the power amplifier is in a saturation state based on detecting a second signal level of the detector signal, wherein the second signal level is greater than the first signal level; and based on determining the power amplifier is in the saturation state, providing second additional bias to the power amplifier; wherein: when the power amplifier is detected to be in the early saturation state, causing flow of current from the voltage output from the first bias circuit to pass through a resistor to increase the detector signal when the voltage output from the first bias circuit exceeds a threshold voltage set based on the bias control voltage and a power supply voltage for control system; and when the power amplifier is detected to be in the saturation state, causing flow of current from the voltage output from the first bias circuit to increase the detector signal without passing through the resistor, when the voltage output from the first bias circuit exceeds a second, higher, threshold based on the bias control voltage.
13 . The method of claim 12 , wherein: the power amplifier comprises a driver amplifier and a final amplifier; the first additional bias is provided to the driver amplifier; and the second additional bias is provided to the final amplifier.
14 . The method of claim 12 , wherein: the first signal level of the detector signal is based on a first level of detected reverse power; the second signal level of the detector signal is based on a second level of detected reverse power; and the second level is greater than the first level.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation of U.S. Patent Application No. 18/121,074, filed March 14, 2023, which claims the benefit of U.S. provisional patent application No. 63/324,822, filed on March 29, 2022, and titled “CLOSED LOOP POWER CONTROL”, the disclosures of which are expressly incorporated herein by reference in their entireties. TECHNICAL FIELD The present disclosure relates generally to systems and methods for closed loop power control. More particularly, the present disclosure relates to systems and methods for radio frequency (RF) power control. BACKGROUND Power amplifiers are typically used in RF systems or devices, where a control system is used to control the output power of the power amplifier. Some control systems use a very large low-dropout (LDO) regulator to control the supply voltage of the power amplifier, including a final stage of the power amplifier. The LDO regulator is typically implemented with a large transistor, such as a large p-type field effect transistor. However, the large transistor consumes a significant amount of area on a die and requires an excellent thermal path, which is not compatible with standard solder bump techniques. Additionally, in some instances, the power amplifier reaches a saturation state where the power amplifier is producing a maximum amount of output power. But the saturation state can create problems with a switching spectrum of the power amplifier. SUMMARY The present disclosure relates to closed loop power control for a power amplifier. A control system is operable to detect when the power amplifier is in an early saturation state and responsively provide first additional bias to the power amplifier. The first additional bias assists or enables the power amplifier in increasing the output power. The control system is also operable to detect when the power amplifier is in a saturation state and responsively provide second additional bias to the power amplifier. The second additional bias assists or enables the power amplifier in increasing the amount of output power until the amount of output power reaches a maximum level. In one aspect, a control system is operable to control an output signal of a power amplifier. The control system includes a detector circuit connected to an output of the power amplifier, a first bias circuit connected to the power amplifier, and a second bias circuit connected to the power amplifier. The detector circuit is operable to detect a reverse voltage on the output of the power amplifier and output a detector signal that provides an indication of a state of the power amplifier. In a non-limiting nonexclusive example, the forward voltage is used for power control and the reverse voltage for amplifier protection. When the power amplifier is in a first state (e.g., an early saturation state), the first bias circuit is operable to provide first additional bias to the power amplifier. When the power amplifier is in a second state (e.g., a saturation state), the second bias circuit is operable to provide second additional bias to the power amplifier. In another aspect, an RF system includes RF input circuitry and RF output circuitry connected to a power amplifier. A control system is also connected to the power amplifier. The control system includes a detector circuit connected to an output of the power amplifier, a first bias circuit connected to the power amplifier, and a second bias circuit connected to the power amplifier. The detector circuit is operable to detect a reverse voltage on the output of the power amplifier and output a detector signal that provides an indication of a state of the power amplifier. When the power amplifier is in a first state (e.g., an early saturation state), the first bias circuit is operable to provide first additional bias to the power amplifier. When the power amplifier is in a second state (e.g., a saturation state), the second bias circuit is operable to provide second additional bias to the power amplifier. In yet another aspect, a method of operating a control system includes determining a power amplifier is in a first state (e.g., an early saturation state) based on a first signal level of a detector signal that is output from a detector circuit connected to an output of the power amplifier. The detector circuit is operable to detect a reverse voltage that provides an indication of a state of the power amplifier. Based on determining the power amplifier is in the early saturation state, first additional bias is provided to the power amplifier. The method further includes determining the power amplifier is in a second state (e.g., a saturation state) based on detecting a second signal level of the detector signal, where the second signal level is greater than the first signal level. Based on determining the power amplifier is in the second state (e.g., the saturation state), second additional bias is provided to the power amplifier. Those skilled in