A radio frequency power amplifier power supply circuit

Abstract

This invention belongs to the field of radio frequency power supply technology, and specifically relates to a power supply circuit for a radio frequency power amplifier. The circuit of this invention includes a DC-DC converter, a multi-output fixed-ratio converter, and a level selector. This invention utilizes the multi-output voltage converter to generate multiple usable voltage levels. The level selector, after receiving the envelope information of the signal, selects an appropriate level to output to the power amplifier to power it, achieving pseudo-envelope following. Compared to traditional envelope following technology, the pseudo-envelope following technology of this invention uses an open-loop control of the output level, which can better handle high-bandwidth signals. Compared to average power following technology, the pseudo-envelope following technology switches the output level faster, improving the efficiency from the power amplifier power supply end to the power amplifier output end.

Description

Technical Field

[0001] This invention belongs to the field of radio frequency power supply technology, and in particular relates to a power supply circuit for a radio frequency power amplifier. Background Technology

[0002] With the full commercialization of 5G mobile communication technology, wireless communication systems are rapidly evolving towards ultra-high data rates and ultra-low latency. The 5G New Ratio (NR) standard increases the transmission bandwidth of its carrier signals to improve data transmission rates. This trend results in modulated radio frequency signals having a higher peak-to-average power ratio, causing traditional radio frequency power amplifiers to face a dilemma of linearity and efficiency imbalance: traditional radio frequency power amplifiers using a fixed power supply voltage have their highest efficiency point at the maximum output power point; however, in order to ensure good linearity across the entire signal range, the power amplifier operates in the low-efficiency power back-off region most of the time.

[0003] As a high-power module in wireless communication systems, the efficiency of radio frequency power amplifiers has a significant impact on the energy consumption, heat dissipation design, and battery life of user terminals.

[0004] Currently, most power supply systems for RF power amplifiers employ envelope follower technology and average power follower technology.

[0005] Envelope tracking technology primarily utilizes a linear amplifier and a single-output switching power supply modulator working together, coupled by a capacitor with a capacitance of several hundred picofarads. Theoretically, envelope tracking technology can achieve real-time tracking of the envelope voltage, resulting in extremely high efficiency from the power supply input to the power amplifier output. However, in practical implementation, to better dynamically track the high-bandwidth envelope signal, the closed-loop bandwidth requirement of the power supply circuit is very high. This high bandwidth requirement also leads to a high static bias current in the linear amplifier itself. These issues result in relatively low efficiency for the linear amplifier, limiting the efficiency from the power system input to the power amplifier output.

[0006] Average power follower (APF) technology employs a standalone switching power supply modulator, whose output voltage is regulated by a digital-to-analog converter controlled by a modem. The voltage duration in APF is a time slot, typically 1 ms (NR), and the output voltage level switching must be completed within a transition time interval, typically 10 µs (NR). Unlike envelope follower, APF tracks voltage in real-time, the power supply modulator's level transition operation is time-slot-based, allowing for higher bandwidth envelope signals. However, due to the lower power amplifier voltage regulation frequency, efficiency from the power amplifier's input to its output is limited, further hindering improvements in efficiency from the power system input to the power amplifier output.

[0007] Therefore, while supporting high-bandwidth envelope signals, further improving the overall efficiency from the power system input to the power amplifier output has become a problem to be solved. Summary of the Invention

[0008] To overcome the shortcomings of the prior art, this invention proposes a power supply circuit for an RF power amplifier. This invention is a pseudo-envelope follower technology that uses a multi-output voltage converter to generate multiple usable levels. After receiving the envelope information of the signal, the level selector selects an appropriate level to output to the power amplifier to power it.

[0009] The technical solution of this invention is as follows: A power supply circuit for an RF power amplifier includes a DC-DC converter, a multi-output fixed-ratio converter, and a level selector; The DC-DC converter has three input ports, where the first input port is connected to an external power supply, the second input port is connected to an envelope signal, and the third input port is connected to a mode selection signal. The output port of the DC-DC converter is connected to the input port of the multi-output fixed-ratio converter and the first input port of the level selector. The multi-output fixed-ratio converter has N output ports; The second input port of the level selector is connected to the envelope signal, the third input port is connected to the mode selection signal, and the fourth to the (N+4)th input ports are respectively connected to the N output ports of the multi-output fixed-ratio converter; the output ports of the level selector are connected to the power amplifier. The mode selection signal includes average power follower mode and pseudo envelope follower mode. When the mode selection signal is average power follower mode, the DC-DC converter generates a corresponding reference signal based on the received envelope signal, adjusts the received input voltage, and generates an output voltage to the level selector. At the same time, the level selector directly selects the output voltage of the DC-DC converter to output to the power amplifier. When the mode selection signal is pseudo envelope follower mode, the DC-DC converter no longer receives the envelope signal through the second port, but instead uses its own internal fixed DC voltage as the input voltage, outputting a fixed level to the level selector and a multi-output fixed-ratio voltage converter. The multi-output fixed-ratio voltage converter generates multiple level-to-level selectors with fixed ratios based on the received fixed level. At this time, the level selector detects the voltage level of the received envelope signal and selects the corresponding required level to output to the power amplifier.

[0010] Furthermore, the multi-output fixed-ratio converter is a switched-capacitor converter, which outputs N different voltage levels by setting up series-connected switch and capacitor branches in the switched-capacitor converter.

[0011] Furthermore, the level selector includes a high-speed comparator, a logic control circuit, and N gating switches. The high-speed comparator compares the received envelope signal with a set reference voltage. The logic control circuit receives a mode selection signal. In pseudo-envelope follower mode, the logic control circuit receives the output signal of the high-speed comparator and generates enable signals for the N gating switches. The N levels output by the multi-output fixed-ratio converter are connected to the output terminals of the level selector through the N gating switches.

[0012] The beneficial effects of this invention are that, compared with the traditional envelope follower technology, the pseudo envelope follower technology of this invention adopts an open-loop control of the output level, which can better cope with high bandwidth signals; compared with the average power follower technology, the pseudo envelope follower technology switches the output level faster, and the efficiency from the power amplifier power supply end to the power amplifier output end is improved. Attached Figure Description

[0013] Figure 1 A schematic diagram of a power supply circuit structure for a radio frequency power amplifier provided in an embodiment of this application; Figure 2 This is a schematic diagram of the structure of the multi-output fixed-ratio voltage converter 1 provided in the embodiments of this application; Figure 3 This is one of the equivalent circuit diagrams of the multi-output fixed-ratio voltage converter 1 provided in the embodiments of this application; Figure 4 A second equivalent circuit diagram of the multi-output fixed-ratio voltage converter 1 provided in the embodiments of this application; Figure 5This is a schematic diagram of the structure of the multi-output fixed-ratio voltage converter 2 provided in the embodiments of this application; Figure 6 This is one of the equivalent circuit diagrams of the multi-output fixed-ratio voltage converter 2 provided in the embodiments of this application; Figure 7 A second equivalent circuit diagram of the multi-output fixed-ratio voltage converter 2 provided in the embodiments of this application; Figure 8 This is a schematic diagram of the structure of the multi-output fixed-ratio voltage converter 3 provided in the embodiments of this application; Figure 9 This is a schematic diagram of the level selector provided in an embodiment of this application. Detailed Implementation

[0014] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0015] Example: The structure of this example is as follows: Figure 1 As shown, the system includes a first-stage DC-DC voltage converter, a second-stage multi-output fixed-ratio voltage converter, and a level selector. The first-stage DC-DC voltage converter has at least three input ports: an external power input port, an envelope signal input port, and a mode selection input port. This voltage converter converts the external power input voltage to a suitable voltage level for use by subsequent modules. Controlled by the mode selection port, the first-stage DC-DC voltage converter, based on the information from the envelope signal input port, directly outputs a suitable output voltage to the level selector to achieve average power following; or it outputs a fixed voltage level to the second-stage multi-output fixed-ratio voltage converter and level selector to participate in generating multiple voltage levels output to the level selector, achieving pseudo-envelope following.

[0016] The second-stage multi-output fixed-ratio voltage converter, consisting of a switching transistor, a flying capacitor, and an output capacitor, is implemented by adding an extra branch to a typical switched-capacitor converter circuit. This voltage converter has one input port to receive the voltage signal from the first-stage DC-DC voltage converter; and multiple output ports that, based on the output voltage of the first-stage DC-DC voltage converter, generate multiple fixed-ratio output levels and output signals from V... O1 V O2 V O3 The port outputs to a level selector, providing multiple available power supply voltages for the RF power amplifier.

[0017] A level selector consists of a high-speed comparator, logic and control circuitry, and selection switches. It has multiple voltage input ports to receive power supply voltages from a DC-DC voltage converter and a fixed-ratio output voltage converter; and an envelope signal input port to receive envelope signals from the external system. In average power follower mode, the level selector outputs a fixed voltage from one channel to the power amplifier as its power supply voltage. In pseudo-envelope follower mode, multiple high-speed comparators detect the current envelope voltage level, and the logic and control circuitry activates the corresponding selection switches to select the closest level as the power amplifier's power supply voltage.

[0018] When the system operates in average power follower mode, the first-stage DC-DC voltage converter and level selector are controlled by the signal at the mode selection port to operate in average power follower mode. After processing the signal at the envelope signal input port, the first-stage DC-DC voltage converter generates a corresponding reference signal to adjust the output voltage, which is then output to the level selector and the multi-output fixed-ratio voltage converter. After the level selector selects the mode at the mode port, it disables the high-speed comparator module, and the logic control circuit keeps V on. O4 The selector switch directly supplies the output voltage of the first-stage DC-DC voltage converter as the power supply voltage to the power amplifier. At this time, the multi-output fixed-ratio voltage converter still operates normally after receiving the output voltage of the first-stage DC-DC voltage converter, but after its multi-level output voltage is transmitted to the level selector, the corresponding selector switch is in the off state and is not supplied as the power supply level to the power amplifier.

[0019] When the system operates in pseudo-envelope follower mode, the first-stage DC-DC voltage converter and level selector are controlled by the signal from the mode selection port. The first-stage DC-DC voltage converter no longer receives signals from the envelope signal input port, but uses its internal fixed DC voltage as a reference to output a stable fixed level to the level selector and the multi-output fixed-ratio voltage converter. After receiving the signal from the first-stage DC-DC voltage converter, the multi-output fixed-ratio voltage converter generates multiple fixed-ratio level outputs to the level selector. The level selector, through the mode selection port, enables the high-speed comparator module. Multiple high-speed comparators detect the voltage level of the current envelope signal and transmit it to the logic control module. Based on the envelope voltage level, the corresponding gating switch is activated, providing the closest level to the power amplifier as the power supply voltage.

[0020] Figure 2This is one of the structural schematic diagrams of a multi-output fixed-ratio voltage converter 1 provided in an embodiment of this application. The multi-output fixed-ratio voltage converter is implemented by adding an additional branch to a typical switched-capacitor converter circuit. The multi-output converter generates multiple voltage levels, but only one level serves as the output voltage for the actual load; therefore, the effect of cross-regulation is minimal.

[0021] In this example, based on a 4:1 series-parallel switched-capacitor converter, two additional voltage output nodes V are generated by adding two additional branches consisting of switches and capacitors. O2 V O3 It achieves three levels of voltage output. The switches in the voltage converter circuit are alternately turned on in two configurations. The switches turned on in configuration one are: SW1, SW2, SW3, SW4, SW5, and SW6; the switches turned on in configuration two are: SW7, SW8, SW9, SW10, SW11, and SW12. Figure 2 In the multi-output fixed-ratio voltage converter 1 shown, the input voltage Vin is the output voltage of the first-stage DC-DC voltage converter, and V is the highest voltage node of the multi-output fixed-ratio voltage converter; O1 V O2 V O3 These are output nodes at different voltage levels. All of these output nodes can be connected to a level selector to select the power amplifier's power supply voltage level, or only some nodes can be selected to output to the level selector as needed. If one or more output nodes at a certain voltage level are not used to select the power amplifier's power supply voltage level, the additional branch used to generate that voltage level is removed to optimize the circuit.

[0022] Figure 3 This is one of the equivalent circuit diagrams of the multi-output fixed-ratio voltage converter 1 provided in the embodiments of this application. When the circuit is operating in a steady state and the switch in configuration two is in the on state, the equivalent circuit diagram is as follows. Figure 3 As shown; the voltage across the flying capacitors is the same as the output voltage, that is: .

[0023] Figure 4 This is a second equivalent circuit diagram of the multi-output fixed-ratio voltage converter 1 provided in the embodiments of this application. When the circuit is operating in a steady state and the switch in configuration one is in the on state, the equivalent circuit diagram is as follows. Figure 3 As shown; the flying capacitor voltage and the input voltage have the following relationship: The voltage across the capacitor added in the additional branch has the following relationship: , This results in a multi-level output voltage with a fixed turns ratio: , , .

[0024] Based on a 4:1 series-parallel switched-capacitor converter, two additional voltage output nodes V are generated by adding two additional branches consisting of switches and capacitors. O2 V O3 This design achieves three voltage output levels; the input voltage Vin is the highest voltage node of the multi-output fixed-ratio voltage converter. In this structure, any additional branch can be interchanged with Vin, or the output capacitor C can be changed... O1 By interchangeing with Vin, different voltage levels can be used as inputs to achieve different voltage conversion modes: buck conversion, boost conversion, and buck-boost conversion.

[0025] Figure 5 This is one of the structural schematic diagrams of the multi-output fixed-ratio voltage converter 2 provided in an embodiment of this application. Figure 2 In contrast, this structure swaps the first additional branch with Vin, changing the voltage conversion mode. Similarly, Vin is swapped with other additional branches and the output capacitor C. O1 Interchangeable, operating principle and Figure 5 The same applies, and will not be repeated hereafter. The switches in the voltage converter circuit are alternately turned on in two configurations: Configuration 1 switches are: SW1, SW2, SW3, SW4, SW5, SW6; Configuration 2 switches are: SW7, SW8, SW9, SW10, SW11, SW12. O1 V O2 V O3 Output nodes at different voltage levels.

[0026] Figure 6 This is one of the equivalent circuit diagrams of the multi-output fixed-ratio voltage converter 2 provided in the embodiments of this application. When the circuit is operating in a steady state and the switch in configuration two is in the on state, the equivalent circuit diagram is as follows. Figure 3 As shown; the voltage across the flying capacitors is the same as the output voltage, that is: .

[0027] Figure 7 This is the second equivalent circuit diagram of the multi-output fixed-ratio voltage converter 2 provided in the embodiments of this application. When the circuit is operating in a steady state and the switch in configuration one is in the on state, the equivalent circuit diagram is as follows. Figure 3 As shown; the flying capacitor voltage and the input voltage have the following relationship: , The voltage across the capacitor added in the additional branch has the following relationship: , This results in a multi-level output voltage with a fixed turns ratio: , , .

[0028] Figure 8 This application provides a schematic diagram of the structure of a multi-output fixed-ratio voltage converter 3. As described above, the multi-output fixed-ratio voltage converters all use a 4:1 series-parallel switched-capacitor converter with an additional circuit to obtain three different output levels with varying ratios. This structure is not limited to a specific number of different output levels with varying ratios; the circuits after expanding or reducing the structure will not be described in detail later. Only one example is used here to illustrate the relevant principles. Compared to... Figure 2 , Figure 8 The circuit in the diagram is based on a 6:1 series-parallel switched-capacitor converter, with four additional branches added to achieve six different output voltage ratios: , , , , For circuits with expanded or reduced structures, swap any additional branch with Vin, or change the output capacitor C. O1 By interchangeing with Vin, different voltage levels of nodes can be used as inputs to achieve voltage conversion modes: buck conversion, boost conversion, or buck-boost conversion.

[0029] Figure 9 This is a schematic diagram of the level selector provided in an embodiment of this application. The level selector mainly consists of a high-speed comparator, logic and control circuitry, and a selection switch. By using the mode selection port, the level selector is set to average power follower mode, and the high-speed comparator section no longer processes the envelope signal. The logic and control circuitry keeps the output voltage V of the first-stage DC-DC voltage converter permanently enabled. O4 In the corresponding selection switch, only the first-stage DC-DC voltage converter in the system provides power voltage to the power amplifier. When the level selector is set to pseudo-envelope follower mode, multiple high-speed comparators compare the envelope signal with reference voltages of different levels to obtain the voltage level of the current envelope signal; the number of high-speed comparators here expands or decreases synchronously with the change of the output port of the multi-output fixed-ratio voltage converter. After obtaining the voltage level of the current envelope signal through comparison, the high-speed comparators transmit the signal to the logic and control circuit. The logic and control circuit opens the corresponding power voltage selection switch according to the voltage level of the current envelope signal. In the system, the first-stage DC-DC voltage converter and the second-stage multi-output fixed-ratio voltage converter together provide usable power voltage to the power amplifier.

Claims

1. A power supply circuit for an RF power amplifier, characterized in that, Includes DC-DC converters, multi-output fixed-ratio converters, and level selectors; The DC-DC converter has three input ports, where the first input port is connected to an external power supply, the second input port is connected to an envelope signal, and the third input port is connected to a mode selection signal. The output port of the DC-DC converter is connected to the input port of the multi-output fixed-ratio converter and the first input port of the level selector. The multi-output fixed-ratio converter has N output ports; The second input port of the level selector is connected to the envelope signal, the third input port is connected to the mode selection signal, and the fourth to the (N+4)th input ports are respectively connected to the N output ports of the multi-output fixed-ratio converter; the output ports of the level selector are connected to the power amplifier. The mode selection signal includes average power follower mode and pseudo-envelope follower mode. When the mode selection signal is in average power follower mode, the DC-DC converter generates a corresponding reference signal based on the received envelope signal, adjusts the received input voltage, and generates an output voltage to the level selector. Simultaneously, the level selector directly selects the output voltage of the DC-DC converter to output to the power amplifier. When the mode selection signal is in pseudo-envelope follower mode, the DC-DC converter no longer receives the envelope signal through the second port, but instead uses its internal... Fixed DC The voltage is such that the output fixed level is selected by a level selector and a multi-output fixed-ratio voltage converter. The multi-output fixed-ratio voltage converter generates multiple level-to-level selectors with fixed ratios based on the received fixed level. At this time, the level selector detects the voltage level of the received envelope signal and selects the corresponding required level to output to the power amplifier.

2. The power supply circuit for an RF power amplifier according to claim 1, characterized in that, The multi-output fixed-ratio converter is a switched-capacitor converter. By setting up series-connected switch and capacitor branches in the switched-capacitor converter, it outputs N different voltage levels.

3. The power supply circuit for an RF power amplifier according to claim 2, characterized in that, The level selector includes a high-speed comparator, a logic control circuit, and N gating switches. The high-speed comparator compares the received envelope signal with a set reference voltage. The logic control circuit receives a mode selection signal. In pseudo-envelope follower mode, the logic control circuit receives the output signal of the high-speed comparator and generates enable signals for the N gating switches. The N levels output by the multi-output fixed-ratio converter are connected to the output terminals of the level selector through the N gating switches.

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