Dynamic bias control circuit and Doherty power amplifier

Abstract

The present invention discloses a dynamic bias control circuit and a Doherty power amplifier. The dynamic bias control circuit is used for the Doherty power amplifier and is electrically connected to the auxiliary power amplifier in the Doherty power amplifier. The dynamic bias control circuit includes: a dynamic bias step-down circuit and a dynamic bias step-up circuit; the output voltage of the dynamic bias step-down circuit is negatively correlated with the input power of the auxiliary power amplifier, and the output voltage of the dynamic bias step-up circuit is positively correlated with the input power of the auxiliary power amplifier; the dynamic bias control circuit is used to correspondingly adjust the bias voltage provided to the auxiliary power amplifier according to the output voltages of the dynamic bias step-down circuit and the dynamic bias step-up circuit, so as to reduce the bias voltage to limit the power amplitude of the auxiliary power amplifier when the input power is greater than the first preset power. This solution can improve the back-off efficiency and protect the safety of the transistors of the auxiliary power amplifier in the high-power mode.

Description

Technical Field

[0001] The present invention relates to the technical field of power amplifiers, and particularly relates to a dynamic bias control circuit and a Doherty power amplifier. Background Art

[0002] As the last active circuit of a millimeter-wave transmitter, the power amplifier bears the heavy burden of indicators such as efficiency, power, and linearity. Usually, the power consumption of a power amplifier (referred to as PA for short, the same below) accounts for more than half of the DC power consumption of the entire transmitter link. Therefore, efficiency is the key performance to measure the quality of a PA.

[0003] In order to improve the working efficiency of the PA, many key technologies have emerged, such as: Kahn envelope separation and recovery technology, envelope tracking technology, Outphasing technology, and Doherty technology. Among them, the Doherty technology, by using a main path PA and a auxiliary path PA, and introducing a load tuning technology, can achieve high power, high efficiency, and high back-off efficiency, and has been widely recognized in the industry.

[0004] However, in the case of the millimeter-wave band, the performance of active devices such as gain, power, and efficiency decreases rapidly with the increase of frequency, and the loss of passive devices becomes larger with the increase of frequency. For a Doherty PA, the loss of the output passive power combining network will seriously deteriorate the overall efficiency of the Doherty circuit. Therefore, with the increase of frequency, the design of a high-efficiency Doherty PA becomes a technical difficulty.

[0005] Traditional Doherty power amplifiers adopt a fixed bias voltage. The main path power amplifier is biased in class B mode, and the auxiliary path power amplifier is biased in class C mode. In the ideal power back-off mode, the auxiliary path power amplifier is in the off state, and the equivalent impedance seen from the power combining point towards the auxiliary path power amplifier is infinite. However, in the actual situation, the auxiliary path power amplifier biased in class C consumes a certain amount of DC power in the back-off mode, and the equivalent impedance seen from the auxiliary path power amplifier is not ideal, thus deteriorating the back-off efficiency.

[0006] Therefore, solutions to the existing technical problems are needed. Summary of the Invention

[0007] The present invention provides a dynamic bias control circuit and a Doherty power amplifier, which aim to introduce a dynamic bias control circuit to the auxiliary path power amplifier in the Doherty power amplifier architecture to further improve the back-off efficiency and protect the safety of the transistors in the auxiliary path power amplifier in the high-power mode.

[0008] In a first aspect, an embodiment of the present invention provides a dynamic bias control circuit, which is used for a Doherty power amplifier and is electrically connected to a slave path power amplifier in the Doherty power amplifier. The dynamic bias control circuit includes: a dynamic bias step-down circuit and a dynamic bias boost circuit connected to the dynamic bias step-down circuit. The output voltage of the dynamic bias step-down circuit is negatively correlated with the input power of the radio frequency signal of the slave path power amplifier, and the output voltage of the dynamic bias boost circuit is positively correlated with the input power of the radio frequency signal of the slave path power amplifier. The dynamic bias control circuit is used to correspondingly adjust the bias voltage provided to the slave path power amplifier according to the output voltage of the dynamic bias step-down circuit and the output voltage of the dynamic bias boost circuit, so as to reduce the bias voltage to limit the power amplitude of the slave path power amplifier when the input power of the radio frequency signal of the slave path power amplifier is greater than a first preset power.

[0009] Optionally, in an embodiment, the dynamic bias step-down circuit includes: a first transistor, a second transistor, a first resistor, a second resistor, and a third resistor. The dynamic bias boost circuit includes: a third transistor, a fourth transistor, a fifth transistor, a fourth resistor, and a first capacitor. A first end of the first transistor is connected to a power supply voltage terminal. A control end of the first transistor is respectively connected to a control end of the third transistor, a first end of the first capacitor, and a current source of the dynamic bias control circuit. A second end of the first transistor is connected to a first end of the first resistor. The second end of the first resistor is respectively connected to a first end of the second transistor, a first end of the second resistor, and a first end of the third resistor. A control end of the second transistor is connected to a second end of the second resistor. A second end of the second transistor is grounded. The first end of the second resistor is connected to the first end of the third resistor. The second end of the third resistor is connected to a first end of the fourth resistor. The second end of the fourth resistor is connected to a first end of the third transistor. The control end of the third transistor is respectively connected to the first end of the first capacitor and the current source. A second end of the third transistor is connected to the power supply voltage terminal. The second end of the first capacitor is grounded. A first end of the fourth transistor is connected to the current source. A control end of the fourth transistor is connected to the first end of the fourth transistor. A second end of the fourth transistor is connected to a first end of the fifth transistor. A control end of the fifth transistor is connected to the first end of the fifth transistor. A second end of the fifth transistor is grounded.

[0010] Optionally, in an embodiment, the third resistor and the fourth resistor are used to adjust the output voltage of the dynamic bias control circuit.

[0011] Optionally, in one embodiment, the common node of the third resistor and the fourth resistor is used to detect the radio frequency signal of the auxiliary power amplifier, and the third resistor and the fourth resistor respectively adjust the output voltage of the dynamic bias buck circuit and the output voltage of the dynamic bias boost circuit according to the detected radio frequency signal.

[0012] Optionally, in one embodiment, the first transistor, the second transistor, the third transistor, the fourth transistor, and the fifth transistor are bipolar transistors or MOS transistors.

[0013] Optionally, in one embodiment, the first capacitor is a metal-insulator-metal capacitor or a cross-over capacitor.

[0014] Optionally, in one embodiment, when the input power of the radio frequency signal of the auxiliary power amplifier is less than the second preset power, the bias voltage provided by the dynamic bias control circuit to the auxiliary power amplifier is a low bias voltage.

[0015] Optionally, in one embodiment, when the input power of the radio frequency signal of the auxiliary power amplifier is greater than the second preset power and gradually increases, the bias voltage provided by the dynamic bias control circuit to the auxiliary power amplifier gradually changes from a low bias voltage to a high bias voltage, where the second preset power is less than the first preset power.

[0016] In a second aspect, an embodiment of the present invention provides a Doherty power amplifier, which includes the dynamic bias control circuit and the auxiliary power amplifier, the main power amplifier, the load modulation circuit, and the quadrature coupler according to any embodiment of the present invention; the dynamic bias control circuit is connected to the auxiliary power amplifier, the auxiliary power amplifier and the main power amplifier are both connected to the load modulation circuit, the load modulation circuit is connected to the radio frequency output end; the quadrature coupler is respectively connected to the radio frequency input end, the auxiliary power amplifier, and the main power amplifier.

[0017] Optionally, in one embodiment, the Doherty power amplifier includes two identical dynamic bias control circuits, and each dynamic bias control circuit is respectively connected to both ends of one side winding of the transformer in the auxiliary power amplifier.

[0018] The present invention introduces a dynamic bias control circuit to the auxiliary power amplifier to achieve the following beneficial effects: when the auxiliary power amplifier is in the power back-off mode of the Doherty power amplifier, the dynamic bias control circuit provides a lower bias voltage to effectively turn off the auxiliary power amplifier, thereby ensuring the back-off efficiency in the power back-off mode; when the input power of the RF signal of the auxiliary power amplifier is within a certain range, the bias voltage provided by the dynamic bias control circuit to the auxiliary power amplifier increases with the increase of the input power, so that the auxiliary power amplifier is in the on state in the high-power mode and improves the linearity of the Doherty power amplifier; when the input power of the RF signal of the auxiliary power amplifier exceeds a certain range, the bias voltage provided by the dynamic bias control circuit to the auxiliary power amplifier is rapidly reduced, and the power amplitude of the auxiliary power amplifier is limited, thereby achieving the effect of protecting the transistors in the auxiliary power amplifier. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those skilled in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0020] Figure 1 It is a schematic diagram of the architecture of a Doherty power amplifier provided by an embodiment of the present invention.

[0021] Figure 2 For Figure 1 It is a schematic diagram of the specific circuit connection between the dynamic bias control circuit and the auxiliary power amplifier shown.

[0022] Figure 3 It is a schematic diagram of the relationship between the output voltage of the dynamic bias control circuit and the input power of the RF signal.

[0023] Figure 4 It is a schematic diagram of the specific circuit connection of the Doherty power amplifier provided by an embodiment of the present invention.

[0024] Figure 5 It is a schematic diagram of the relationship between the output voltage of the dynamic bias control circuit and the output power of the Doherty power amplifier.

[0025] Figure 6 It is a schematic diagram showing that the linearity of the dynamic bias control circuit is better than that of the fixed bias control circuit.

[0026] Figure 7Schematic diagram showing that the circuit efficiency of the circuit adopting the dynamic bias control circuit is higher than that of the circuit adopting the fixed bias control circuit in the back-off mode. Detailed implementation manners

[0027] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part rather than all of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making creative efforts belong to the scope of protection of the present invention. In addition, it should be understood that the specific implementation manners described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention. In the present invention, unless otherwise stated, the orientation terms such as "upper", "lower", "left", and "right" generally refer to the upper, lower, left, and right in the actual use or working state of the device, specifically the drawing directions in the accompanying drawings.

[0028] The present invention provides a dynamic bias control circuit and a Doherty power amplifier, which will be described in detail below. It should be noted that the description order of the following embodiments does not limit the preferred order of the embodiments of the present invention. And in the following embodiments, each embodiment has its own emphasis. For the parts not detailed in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0029] Figure 1 Schematic diagram of the architecture of a Doherty power amplifier provided in an embodiment of the present invention. Figure 2 For Figure 1 Specific circuit connection diagram of the dynamic bias control circuit shown and the auxiliary power amplifier.

[0030] As Figure 1 And Figure 2As shown in the figure, an embodiment of the present invention provides a dynamic bias control circuit 1, which is used for a Doherty power amplifier and is electrically connected to a slave path power amplifier 2 (or simply referred to as a slave amplifier, the same hereinafter) in the Doherty power amplifier. The dynamic bias control circuit 1 includes: a dynamic bias step-down circuit 11 and a dynamic bias boost circuit 12 connected to the dynamic bias step-down circuit 11. The output voltage of the dynamic bias step-down circuit 11 is negatively correlated with the input power of the radio frequency signal of the slave path power amplifier 2, and the output voltage of the dynamic bias boost circuit 12 is positively correlated with the input power of the radio frequency signal of the slave path power amplifier 2. The dynamic bias control circuit 1 is used to adjust the bias voltage provided to the slave path power amplifier 2 accordingly according to the output voltage of the dynamic bias step-down circuit 11 and the output voltage of the dynamic bias boost circuit 12, so as to reduce the bias voltage when the input power of the radio frequency signal of the slave path power amplifier 2 is greater than a first preset power, and limit the power amplitude of the slave path power amplifier 2.

[0031] It should be noted that the radio frequency signal of the slave path power amplifier 2 is derived from the radio frequency signal received at the radio frequency input end of the Doherty power amplifier.

[0032] The dynamic bias control circuit 1 of the present invention is applicable to a Doherty power amplifier. By reasonably designing the dynamic bias control circuit 1, when the input power of the radio frequency signal exceeds a certain range, the bias voltage provided by the dynamic bias control circuit 1 to the slave path power amplifier 2 can be quickly reduced, and the power amplitude of the slave path power amplifier 2 can be limited, so as to protect the transistors in the slave path power amplifier 2, improve the reliability of related products and extend the service life of the products.

[0033] The dynamic bias control circuit 1 will be further described below with reference to the accompanying drawings. The dynamic bias control circuit 1 includes the dynamic bias step-down circuit 11 and the dynamic bias boost circuit 12.

[0034] The dynamic bias buck circuit 11 includes: a first transistor N1, a second transistor N2, a first resistor R1, a second resistor R2, and a third resistor R3. The dynamic bias boost circuit 12 includes: a third transistor N3, a fourth transistor N4, a fifth transistor N5, a fourth resistor R4, and a first capacitor C1. The first end of the first transistor N1 is connected to the power supply voltage terminal Vdd. The control end of the first transistor N1 is respectively connected to the control end of the third transistor N3, the first end of the first capacitor C1, and the current source I of the dynamic bias control circuit 1. The second end of the first transistor N1 is connected to the first end of the first resistor R1. The second end of the first resistor R1 is respectively connected to the first end of the second transistor N2, the first end of the second resistor R2, and the first end of the third resistor R3. The control end of the second transistor N2 is connected to the second end of the second resistor R2. The second end of the second transistor N2 is grounded. The first end of the second resistor R2 is connected to the first end of the third resistor R3. The second end of the third resistor R3 is connected to the first end of the fourth resistor R4. The second end of the fourth resistor R4 is connected to the first end of the third transistor N3. The control end of the third transistor N3 is respectively connected to the first end of the first capacitor C1 and the current source I. The second end of the third transistor N3 is connected to the power supply voltage terminal Vdd. The second end of the first capacitor C1 is grounded. The first end of the fourth transistor N4 is connected to the current source I. The control end of the fourth transistor N4 is connected to the first end of the fourth transistor N4. The second end of the fourth transistor N4 is connected to the first end of the fifth transistor. The control end of the fifth transistor N5 is connected to the first end of the fifth transistor N5. The second end of the fifth transistor N5 is grounded.

[0035] Among them, the first transistor N1, the second transistor N2, the third transistor N3, the fourth transistor N4, and the fifth transistor N5 are bipolar transistors or MOS transistors. In this embodiment, the first transistor N1, the second transistor N2, the third transistor N3, the fourth transistor N4, and the fifth transistor N5 are bipolar transistors. In other partial embodiments, the first transistor N1, the second transistor N2, the third transistor N3, the fourth transistor N4, and the fifth transistor N5 can also be MOS transistors. If MOS transistors are used, such as Figure 2 the current source I shown needs to be replaced with a voltage source.

[0036] The first capacitor C1 is a metal-insulator-metal (MIM) capacitor or a coplanar capacitor. In this embodiment, an MIM capacitor is adopted, i.e., a MIM capacitor. In this way, when forming the dynamic bias control circuit 1, the MIM capacitor and the metals of other devices in the circuit are not on the same layer, thus forming a more three-dimensional and more compact structure.

[0037] The third resistor R3 and the fourth resistor R4 are used to adjust the output voltage of the dynamic bias control circuit 1. Further, the third resistor R3 and the fourth resistor R4 are respectively used to adjust the output voltage of the dynamic bias buck circuit 11 and the output voltage of the dynamic bias boost circuit 12 according to the detected radio frequency signal.

[0038] It should be noted that the detected radio frequency signal comes from the radio frequency signal in the signal path corresponding to the auxiliary power amplifier 2. The common node between the dynamic bias buck circuit 11 and the dynamic bias boost circuit 12 in the dynamic bias control circuit 1 can detect the radio frequency signal from the above signal path. In addition, it should be noted that the input end of the signal path can refer to Figure 4 the radio frequency input end shown in Figure 4 the reference numeral 7 shown in Figure 4 The radio frequency input end is connected to the quadrature coupler. The output end of the signal path can refer to Figure 4 the radio frequency output end shown in

[0039] the reference numeral 5 shown in

[0040] Specifically, when the resistance value of the third resistor R3 of the dynamic bias buck circuit 11 is decreased, the negative feedback of the dynamic bias buck circuit 11 is decreased, so the buck effect of the dynamic bias buck circuit 11 is increased. When the resistance value of the third resistor R3 of the dynamic bias buck circuit 11 is increased, the negative feedback of the dynamic bias buck circuit 11 is increased, so the buck effect of the dynamic bias buck circuit 11 is decreased.

[0041] It should be noted that the greater the input power of the radio frequency signal detected by the dynamic bias step-down circuit 11, the larger the voltage swing of the bias voltage Vb of the second transistor N2, which causes the DC voltage drop Vce across the second transistor N2 to become smaller. As a result, the output voltage of the dynamic bias step-down circuit 11 decreases accordingly (for the second transistor N2, the DC voltage drop Vce = Vc - Ve, the emitter e is grounded, and the ground voltage is zero, i.e., remains unchanged. When the DC voltage drop Vce decreases, Vc also decreases accordingly. Since the Vc terminal is connected to the common node of the second resistor R2 and the third resistor R3, the DC output voltage across the third resistor R3 also decreases accordingly). Thus, the output voltage of the dynamic bias step-down circuit 11 decreases as the input power of the detected radio frequency signal increases.

[0042] When the resistance value of the fourth resistor R4 of the dynamic bias boost circuit is decreased, the negative feedback of the dynamic bias boost circuit 12 is reduced, thus increasing the boosting effect of the dynamic bias boost circuit 12. When the resistance value of the fourth resistor R4 of the dynamic bias boost circuit 12 is increased, the negative feedback of the dynamic bias step-down circuit 11 is increased, thus reducing the boosting effect of the dynamic bias step-down circuit 11.

[0043] It should be noted that the greater the input power of the radio frequency signal detected by the dynamic bias boost circuit 12, the smaller the equivalent resistance of the third transistor N3 in the current mirror circuit composed of the third transistor N3, the fourth transistor N4, and the fifth transistor N5, which causes the Ice flowing through the third transistor N3 to increase, that is, the output voltage of the dynamic bias boost circuit 12 increases accordingly. Thus, the output voltage of the dynamic bias boost circuit 12 increases as the input power of the detected radio frequency signal increases.

[0044] Since the dynamic bias control circuit 1 includes a dynamic bias step-down circuit 11 and a dynamic bias boost circuit 12, and the output voltage of the dynamic bias step-down circuit 11 decreases as the detected input power increases, and the output voltage of the dynamic bias boost circuit 12 increases as the detected input power increases. Therefore, the dynamic bias control circuit 1 can adjust the bias strength of the corresponding circuits (i.e., the dynamic bias step-down circuit 11 and the dynamic bias boost circuit 12) through the coordinated operation of the above-mentioned dynamic bias step-down circuit 11 and dynamic bias boost circuit 12, and by adjusting the resistance values of the third resistor R3 and the fourth resistor R4, so as to obtain the boosting or step-down effect of the dynamic bias control circuit 1.

[0045] In one embodiment, when the input power of the RF signal of the auxiliary power amplifier 2 is less than the second preset power, the bias voltage provided by the dynamic bias control circuit 1 to the auxiliary power amplifier 2 is a low bias voltage, where the second preset power is less than the first preset power. In other words, since the auxiliary power amplifier 2 only needs to be turned on in the large-signal mode (for example, the bias voltage is 0.78V), when the input power of the RF signal is less than the second preset power, that is, in the small-signal mode, the bias voltage provided by the dynamic bias control circuit 1 to the auxiliary power amplifier 2 can be lower, so that the auxiliary power amplifier 2 is more effectively turned off (that is, the lower the bias voltage, the more complete the turn-off of the circuit), thus ensuring the back-off efficiency. It should be understood that the main power amplifier 3 in the Doherty power amplifier (or simply referred to as the main power amplifier, the same below) is biased in class B mode, so the main power amplifier 3 is always in the on state.

[0046] In one embodiment, when the input power of the RF signal of the auxiliary power amplifier 2 is greater than the second preset power and gradually increases, the bias voltage provided by the dynamic bias control circuit 1 to the auxiliary power amplifier 2 gradually changes from the low bias voltage to the high bias voltage, where the second preset power is less than the first preset power. In other words, when the input power of the RF signal gradually increases and the main power amplifier 3 enters the compression state, the bias voltage provided by the dynamic bias control circuit 1 to the auxiliary power amplifier 2 gradually increases, so that the auxiliary power amplifier 2 is turned on in the large-signal mode. Compared with the fixed bias control, after the auxiliary power amplifier 2 is turned on, the bias voltage provided by the dynamic bias control circuit 1 to the auxiliary power amplifier 2 correspondingly increases with the further increase of the input power, which is beneficial to ensuring the linearity of the circuit. It should be noted that in this stage, when increasing the working current of the transistor of the auxiliary power amplifier 2, the gain of the auxiliary power amplifier can be improved.

[0047] In one embodiment, when the input power of the RF signal is greater than the first preset power, that is, when the input power reaches a certain range, the bias voltage provided by the dynamic bias control circuit 1 to the auxiliary power amplifier 2 rapidly decreases. The reason why the bias voltage of the auxiliary power amplifier 2 rapidly decreases is that the dynamic bias control circuit 1 includes a dynamic bias step-down circuit 11 and a dynamic bias step-up circuit 12. The output voltage of the dynamic bias step-down circuit 11 monotonically decreases with the increase of the input power of the RF signal. Its specific change trend is: in the initial stage, it is relatively gentle, and in the large-signal mode and when the input power is greater than the first preset power, it rapidly decreases (similar to first smoothing a certain distance and then making a steep parabolic motion). The output voltage of the dynamic bias step-up circuit 12 monotonically increases with the increase of the input power of the RF signal. Its specific change trend is as Figure 3 shown in the change curve, and this change curve is the function y=(x / 30)6 It is fitted with +0.75, where x represents the input power and y represents the output voltage. In the large-signal mode and when the input power is greater than the first preset power, the magnitude of the input power of the RF signal has no amplification effect on the DC characteristics of the third transistor N3. Therefore, the voltage reduction effect of the dynamic bias voltage reduction circuit 11 will quickly affect the voltage boost effect of the dynamic bias voltage boost circuit 12, that is, the voltage reduction effect is more significant than the voltage boost effect. Thus, the dynamic bias control circuit 1 achieves the effect of quickly reducing the voltage, and further reduces the amplification effect of the transistors of the auxiliary path power amplifier 2, which can reduce the voltage swing of the transistors of the auxiliary path power amplifier 2 to further ensure that the transistors can operate within the withstand voltage range, which is beneficial to the safety of the transistors. That is to say, in the large-signal mode and when the input power is greater than the first preset power, the voltage reduction speed of the dynamic bias voltage reduction circuit 11 is much greater than the voltage boost speed of the dynamic bias voltage boost circuit 12. Thus, the bias voltage provided by the dynamic bias control circuit 1 to the auxiliary path power amplifier 2 quickly decreases, and the voltage swing of the transistors of the auxiliary path power amplifier 2 quickly weakens, thereby achieving the reliability effect of protecting the transistors.

[0048] As Figure 4 shown, in an embodiment of the present invention, a Doherty power amplifier is provided. The Doherty power amplifier includes the dynamic bias control circuit 1 and the auxiliary path power amplifier 2, the main path power amplifier 3, the load modulation circuit 4 (or load modulation network) and the quadrature coupler 6 described in any embodiment of the present invention. Among them, the specific structures of the dynamic bias control circuit 1 and the auxiliary path power amplifier 2 are as described above and will not be elaborated here. The dynamic bias control circuit 1 is connected to the auxiliary path power amplifier 2, the auxiliary path power amplifier 2 and the main path power amplifier 3 are both connected to the load modulation circuit 4, and the load modulation circuit 4 is connected to the RF output terminal 5; the quadrature coupler 6 is respectively connected to the RF input terminal 1, the auxiliary path power amplifier 2 and the main path power amplifier 3.

[0049] Furthermore, the Doherty power amplifier includes two dynamic bias control circuits 1, and each dynamic bias control circuit 1 is respectively connected to both ends of one side winding of the transformer in the auxiliary path power amplifier 2.

[0050] The main path power amplifier 3 in the Doherty power amplifier is biased in class B mode (i.e., with a relatively high bias voltage) and is always on. The auxiliary path power amplifier 2 is biased in class C mode (i.e., with a relatively low bias voltage). When the input power of the RF signal is small, the auxiliary path power amplifier 2 is off. When the input power of the RF signal is large, the auxiliary path power amplifier 2 is on. Further, when the input power of the RF signal is small, the bias voltage of the auxiliary path power amplifier 2 is low and the auxiliary path power amplifier 2 is off. At the same time, only the main path power amplifier 3 is in operation, so power consumption can be saved, thereby improving the performance of the auxiliary path power amplifier in the small signal mode. When the input power of the RF signal is large, the bias voltage of the auxiliary path power amplifier 2 is high and the auxiliary path power amplifier 2 is on. Both the main path power amplifier 3 and the auxiliary path power amplifier 2 are in operation, thus ensuring the output power of the Doherty power amplifier.

[0051] Figure 5 Schematic diagram of the relationship between the output voltage of the dynamic bias control circuit and the output power of the Doherty power amplifier. As Figure 5 shown, in the relationship between the output voltage of the dynamic bias control circuit 1 and the output power of the Doherty power amplifier, when the output power is 15 - 20 dBm, the corresponding output voltage rises relatively rapidly; when the output power is 20 - 25 dBm, the corresponding output voltage drops relatively rapidly. The reason for the change in the output voltage of the dynamic bias control circuit 1 as Figure 5 shown is as follows:

[0052] The dynamic bias control circuit 1 includes a dynamic bias step - down circuit 11 and a dynamic bias step - up circuit 12. Among them, the output voltage of the dynamic bias step - down circuit 11 decreases monotonically with the increase of the input power of the RF signal. Its specific change trend is: in the initial stage, it is relatively flat. In the large signal mode and when the input power is greater than the first preset power, it drops rapidly (similar to a smooth section first and then a steep parabolic motion). The output voltage of the dynamic bias step - up circuit 12 increases monotonically with the increase of the input power of the RF signal. Its specific change trend is as Figure 3 shown by the change curve, and this change curve is the function y=(x / 30) 6It is fitted with +0.75, where x represents the input power and y represents the output voltage. In the large-signal mode and when the input power is greater than the first preset power, for the dynamic bias step-down circuit 11, the radio frequency signal acts on the base of the second transistor N2 (i.e., the control terminal of the second transistor N2). Due to the amplification effect of the transistor, the DC voltage drop Vce of the second transistor N2 changes significantly. For the dynamic bias step-up circuit 12, the radio frequency signal acts on the emitter of the third transistor N3 (i.e., the first terminal of the third transistor N3). Therefore, the change in the input power of the radio frequency signal has no amplification effect on the DC characteristics of the third transistor N3. As a result, the step-down effect of the dynamic bias step-down circuit 11 will quickly affect the step-up effect of the dynamic bias step-up circuit 12, that is, the step-down effect is more significant than the step-up effect. Thus, the dynamic bias control circuit 1 achieves the effect of quickly stepping down the voltage and shows a change as Figure 5 shown.

[0053] Accordingly, the amplification effect of the transistor of the auxiliary road power amplifier 2 decreases rapidly, which can reduce the voltage swing of the transistor of the auxiliary road power amplifier 2 to further ensure that the transistor can work within the withstand voltage range, which is beneficial to the safety of the transistor. That is to say, in the large-signal mode and when the input power is greater than the first preset power, the voltage step-down speed of the dynamic bias step-down circuit 11 is much greater than the voltage step-up speed of the dynamic bias step-up circuit 12. Therefore, the bias voltage provided by the dynamic bias control circuit 1 to the auxiliary road power amplifier 2 decreases rapidly, causing the voltage swing of the transistor of the auxiliary road power amplifier 2 to weaken rapidly, thereby achieving the reliability effect of protecting the transistor.

[0054] Figure 6 It is a schematic diagram showing that the linearity of the dynamic bias control circuit is better than that of the fixed bias control circuit.

[0055] As Figure 6 shown, the gain of the dynamic bias control circuit 1 is basically the same as that of the fixed bias control circuit, except that when the input power of the radio frequency signal is 5 - 10 dBm, the gain of the dynamic bias control circuit 1 is significantly higher than that of the fixed bias control circuit.

[0056] Since when the input power of the radio frequency signal is 5 - 10 dBm, the bias voltage provided by the dynamic bias control circuit 1 to the auxiliary road power amplifier 2 increases with the increase of the input power, the gain of the auxiliary road power amplifier can be ensured.

[0057] If the fixed bias control circuit has the same performance as the dynamic bias control circuit in the large-signal mode (for example, the input power = 10 dBm), then the bias voltage of the fixed bias control circuit in the back-off mode (between 5 - 10 dBm) of the Doherty power amplifier is small and is not sufficient to enable the auxiliary road power amplifier to work effectively and provide sufficient gain.

[0058] If the fixed bias control circuit provides sufficient gain in the back-off mode (between 5 and 10 dBm) of the Doherty power amplifier, the auxiliary power amplifier will enter the compression state earlier in the large-signal mode (for example, input power > 10 dBm), thus unable to ensure equivalent output power and linearity compared with the Doherty power amplifier using the dynamic bias control circuit.

[0059] Figure 7 It is a schematic diagram showing that the circuit efficiency of the circuit using the dynamic bias control circuit is higher than that of the circuit using the fixed bias control circuit in the back-off mode.

[0060] As Figure 7 shown, the circuit efficiency of the circuit using the dynamic bias control circuit 1 is basically higher than that of the circuit using the fixed bias control circuit in the back-off mode, especially in the stage where the output power of the auxiliary power amplifier 2 is 16 - 21 dBm.

[0061] The reason for the above situation is that circuit efficiency = (output power - input power) / DC power consumption. As described above, the output power of the Doherty power amplifier using the dynamic bias control circuit is better than that of the Doherty power amplifier using the fixed bias control. Therefore, the circuit efficiency of the circuit using the dynamic bias control circuit 1 is better than that of the circuit using the fixed bias control circuit in the back-off mode (especially in the stage where the output power is 16 - 21 dBm).

[0062] In addition, since the auxiliary power amplifier 2 in the Doherty power amplifier changes accordingly according to the bias voltage provided by the dynamic bias control circuit 1, the Doherty power amplifier has the following technical effects:

[0063] First, since the auxiliary power amplifier 2 only needs to be turned on in the large-signal mode (for example, the bias voltage is 0.78V), when the input power of the radio frequency signal is less than the second preset power, that is, in the small-signal mode, the bias voltage provided by the dynamic bias control circuit 1 to the auxiliary power amplifier 2 can be lower, thus more effectively turning off the auxiliary power amplifier 2 (that is, the lower the bias voltage, the more complete the turn-off of the circuit), so as to ensure the back-off efficiency in the power back-off mode. Compared with the Doherty power amplifier using the fixed bias control circuit, the dynamic bias control circuit 1 of the present invention provides a lower bias voltage in the small-signal mode, thus turning off the auxiliary power amplifier 2 more completely and ensuring the back-off efficiency.

[0064] Second, compared with the fixed bias control circuit, after the auxiliary power amplifier 2 is turned on, the bias voltage provided by the dynamic bias control circuit 1 to the auxiliary power amplifier 2 increases correspondingly as the input power further increases, which is beneficial to ensuring the linearity of the circuit. It should be noted that when increasing the operating current of the transistor of the auxiliary power amplifier 2, the gain of the auxiliary power amplifier can be improved.

[0065] Third, when the input power of the radio frequency signal is greater than the first preset power, that is, when the input power reaches a certain range, the bias voltage provided by the dynamic bias control circuit 1 to the auxiliary power amplifier 2 decreases rapidly. The reason why the bias voltage of the auxiliary power amplifier 2 decreases rapidly is that: the dynamic bias control circuit 1 includes a dynamic bias step-down circuit 11 and a dynamic bias boost circuit 12. The output voltage of the dynamic bias step-down circuit 11 decreases monotonically as the input power of the radio frequency signal increases. Its specific change trend is: in the initial stage, it is relatively gentle. In the large-signal mode and when the input power is greater than the first preset power, it decreases rapidly (similar to a smooth section first and then a steep parabolic motion). The output voltage of the dynamic bias boost circuit 12 increases monotonically as the input power of the radio frequency signal increases. Its specific change trend is as Figure 3 shown in the change curve, which is fitted by the function y=(x / 30) 6 +0.75, where x represents the input power and y represents the output voltage. In the large-signal mode and when the input power is greater than the first preset power, the magnitude of the input power of the radio frequency signal has no amplification effect on the DC characteristics of the third transistor N3. Therefore, the step-down effect of the dynamic bias step-down circuit 11 will quickly affect the boost effect of the dynamic bias boost circuit 12, that is, the step-down effect is more significant than the boost effect. Thus, the effect of quickly reducing the voltage of the dynamic bias control circuit 1 is achieved, and further, the amplification effect of the transistor of the auxiliary power amplifier 2 is quickly reduced. In this way, the voltage swing of the transistor of the auxiliary power amplifier 2 can be reduced to further ensure that the transistor can operate within the withstand voltage range, which is beneficial to the safety of the transistor.

[0066] In the above embodiments, the descriptions of the respective embodiments have their own emphases. For the parts not detailed in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0067] The above has introduced in detail a dynamic bias control circuit and a Doherty power amplifier provided by embodiments of the present invention. Specific examples are used herein to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the technical solution and its core idea of the present invention; those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A dynamic bias control circuit for a Doherty power amplifier, characterized in that, The dynamic bias control circuit is electrically connected to the auxiliary power amplifier in the Doherty power amplifier; the dynamic bias control circuit includes: a dynamic bias step-down circuit and a dynamic bias boost circuit connected to the dynamic bias step-down circuit; the output voltage of the dynamic bias step-down circuit is negatively correlated with the input power of the radio frequency signal of the auxiliary power amplifier, and the output voltage of the dynamic bias boost circuit is positively correlated with the input power of the radio frequency signal of the auxiliary power amplifier; the dynamic bias control circuit is configured to correspondingly adjust the bias voltage provided to the auxiliary power amplifier according to the output voltage of the dynamic bias step-down circuit and the output voltage of the dynamic bias boost circuit, so as to reduce the bias voltage when the input power of the radio frequency signal of the auxiliary power amplifier is greater than a first preset power, thereby limiting the power amplitude of the auxiliary power amplifier. The dynamic bias step-down circuit includes: a first transistor, a second transistor, a first resistor, a second resistor, and a third resistor; the dynamic bias boost circuit includes: a third transistor, a fourth transistor, a fifth transistor, a fourth resistor, and a first capacitor; a first end of the first transistor is connected to a power supply voltage terminal, a control end of the first transistor is respectively connected to a control end of the third transistor, a first end of the first capacitor, and a current source of the dynamic bias control circuit, and a second end of the first transistor is connected to a first end of the first resistor; the second end of the first resistor is respectively connected to a first end of the second transistor, a first end of the second resistor, and a first end of the third resistor; a control end of the second transistor is connected to a second end of the second resistor, and a second end of the second transistor is grounded; the first end of the second resistor is connected to the first end of the third resistor; the second end of the third resistor is connected to a first end of the fourth resistor; the second end of the fourth resistor is connected to a first end of the third transistor; the control end of the third transistor is respectively connected to the first end of the first capacitor and the current source, and a second end of the third transistor is connected to the power supply voltage terminal; the second end of the first capacitor is grounded; a first end of the fourth transistor is connected to the current source, a control end of the fourth transistor is connected to the first end of the fourth transistor, and a second end of the fourth transistor is connected to a first end of the fifth transistor; a control end of the fifth transistor is connected to the first end of the fifth transistor, and a second end of the fifth transistor is grounded.

2. The dynamic bias control circuit according to claim 1, wherein The third resistor and the fourth resistor are used to adjust the output voltage of the dynamic bias control circuit.

3. The dynamic bias control circuit according to claim 1 or 2, wherein A common node of the third resistor and the fourth resistor is used to detect the radio frequency signal of the auxiliary power amplifier, and the third resistor and the fourth resistor respectively adjust the output voltage of the dynamic bias step-down circuit and the output voltage of the dynamic bias boost circuit according to the detected radio frequency signal.

4. The dynamic bias control circuit according to claim 1, wherein The first transistor, the second transistor, the third transistor, the fourth transistor, and the fifth transistor are bipolar transistors or MOS transistors.

5. The dynamic bias control circuit according to claim 1, wherein The first capacitor is a metal-insulator-metal capacitor or a coplanar capacitor.

6. The dynamic bias control circuit according to claim 1, wherein When the input power of the radio frequency signal of the auxiliary power amplifier is less than a second preset power, the bias voltage provided by the dynamic bias control circuit to the auxiliary power amplifier is a low bias voltage.

7. The dynamic bias control circuit according to claim 1, wherein When the input power of the radio frequency signal of the auxiliary power amplifier is greater than the second preset power and gradually increases, the bias voltage provided by the dynamic bias control circuit to the auxiliary power amplifier gradually changes from the low bias voltage to the high bias voltage, where the second preset power is less than the first preset power.

8. A Doherty power amplifier, characterized in that, Comprising the dynamic bias control circuit according to any one of claims 1 to 7, and the auxiliary power amplifier, the main power amplifier, the load modulation circuit and the quadrature coupler; the dynamic bias control circuit is connected to the auxiliary power amplifier, the auxiliary power amplifier and the main power amplifier are both connected to the load modulation circuit, the load modulation circuit is connected to the radio frequency output terminal; the quadrature coupler is respectively connected to the radio frequency input terminal, the auxiliary power amplifier and the main power amplifier.

9. The Doherty power amplifier according to claim 8, characterized in that, The Doherty power amplifier includes two identical dynamic bias control circuits, and each of the dynamic bias control circuits is respectively connected to both ends of one side winding of the transformer in the auxiliary power amplifier.

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