Protection circuit, power amplifier and radio frequency front-end module

Abstract

The utility model discloses a protection circuit, a power amplifier and a radio frequency front-end module, and the protection circuit comprises a signal input end, a grounding end, a first diode unit, a second diode unit and a transistor unit. The first diode unit comprises at least one first diode, the transistor unit and each first diode are connected in series between the signal input end and the grounding end, and the conduction voltage drop of the transistor unit is smaller than the conduction voltage drop of the first diode; the first end of the second diode unit is connected with the grounding end, and the second end of the second diode unit is connected with the signal input end. According to the invention, the saturation efficiency of the power amplifier can be ensured while the protection effect of the protection circuit is realized.

Description

Technical Field

[0001] This application belongs to the technical field of power amplifiers, and specifically relates to a protection circuit, a power amplifier, and a radio frequency front-end module. Background Art

[0002] The power amplifier, abbreviated as PA, is an important component for realizing wireless transmission of radio frequency signals. With the upgrade of mobile communication networks, communication devices need to be able to select different frequency bands for radio frequency signal transmission in different mobile communication network standards, which requires radio frequency power amplifiers applicable to various communication networks to provide higher output power, which also means that the power amplifier will generate higher voltage and larger voltage swings.

[0003] In traditional PA applications, a protection circuit is set at the output end of the power amplifier to reduce the voltage peak generated by the power amplifier through the protection circuit and provide a clamping voltage for the power amplifier. However, the clamping voltage of the protection circuit is negatively correlated with the saturation efficiency of the power amplifier, that is, the lower the clamping voltage, the better the protection effect, but the greater the loss of the saturation efficiency of the power amplifier. Therefore, how to reduce the loss of the saturation efficiency of the power amplifier while ensuring the circuit protection effect is an urgent problem to be solved. Summary of the Utility Model

[0004] This application provides a protection circuit, a power amplifier, and a radio frequency front-end module, which can reduce the loss of the saturation efficiency of the power amplifier while ensuring the circuit protection effect.

[0005] To solve the above technical problems, in a first aspect, this application provides a protection circuit. The protection circuit includes a signal input end and a ground end, and further includes a first diode unit, a second diode unit, and a transistor unit;

[0006] The first diode unit includes at least one first diode. The transistor unit is connected in series with each of the first diodes between the signal input end and the ground end, and the conduction voltage drop of the transistor unit is less than the conduction voltage drop of the first diode;

[0007] The first end of the second diode unit is connected to the ground end, and the second end of the second diode unit is connected to the signal input end.

[0008] As a further improvement of this application, the transistor unit includes at least one Schottky diode, and the Schottky diode is connected in series with the first diode unit between the signal input end and the ground end;

[0009] Wherein, the first end of the Schottky diode is connected to the signal input end, and the second end of the Schottky diode is connected to the first end of the first diode unit;

[0010] Alternatively, the first end of the Schottky diode is connected to the second end of the first diode unit, and the second end of the Schottky diode is connected to the ground terminal;

[0011] Alternatively, the Schottky diode is connected in series between two adjacent first diode units.

[0012] As a further improvement of the present application, the transistor unit includes at least one bipolar junction transistor, the bipolar junction transistor is connected in series with the first diode unit between the signal input terminal and the ground terminal, and the first end and the second end of the bipolar junction transistor are short-circuited;

[0013] Wherein, the first end of the bipolar junction transistor is connected to the signal input terminal, and the third end of the bipolar junction transistor is connected to the first end of the first diode unit;

[0014] Alternatively, the first end of the bipolar junction transistor is connected to the second end of the first diode unit, and the third end of the bipolar junction transistor is connected to the ground terminal;

[0015] Alternatively, the bipolar junction transistor is connected in series between two adjacent first diodes.

[0016] As a further improvement of the present application, the transistor unit includes at least one Schottky diode and at least one bipolar junction transistor, the Schottky diode, the bipolar junction transistor and the first diode unit are connected in series between the signal input terminal and the ground terminal, and the first end and the second end of the bipolar junction transistor are short-circuited.

[0017] As a further improvement of the present application, the second diode unit includes at least one second diode, and the conduction voltage drop of the transistor unit is less than the conduction voltage drop of the second diode.

[0018] In a second aspect, the present application provides a power amplifier, the power amplifier includes the protection circuit according to any one of the above, wherein the signal input terminal of the protection circuit is connected to the output terminal of the power amplification circuit.

[0019] As a further improvement of the present application, the power amplifier is a single-ended power amplifier, the single-ended power amplifier includes a power amplification circuit, and the power amplification circuit includes at least one power amplification transistor;

[0020] The number of the protection circuits is configured to be at least one, and the output terminal of the power amplification transistor is connected to at least one of the protection circuits.

[0021] As a further improvement of the present application, the power amplifier includes at least two power amplification circuits, and each power amplification circuit includes at least one power amplification transistor;

[0022] The number of the protection circuits is configured to be at least two, and the output ends of at least two power amplification transistors are respectively connected to at least one protection circuit.

[0023] As a further improvement of the present application, the power amplifier is a differential power amplifier, a push-pull power amplifier, a Doherty power amplifier or a balanced power amplifier.

[0024] In a third aspect, the present application provides a radio frequency front-end module, which includes the protection circuit described in any one of the above, or includes the power amplifier described in any one of the above.

[0025] The protection circuit, the power amplifier and the radio frequency front-end module provided by the present application have the following beneficial effects:

[0026] In the protection circuit, the power amplifier and the radio frequency front-end module provided by the present application, a first diode unit and a transistor unit are arranged between the signal input end and the ground end. Since the on-voltage drop of the transistor unit is less than the on-voltage drop of a single first diode in the first diode unit, the step value of the protection circuit will be reduced, and the clamping voltage of the protection circuit will not be greatly increased. It can improve the saturation efficiency of the power amplifier while realizing the protection effect of the protection circuit. Description of the Drawings

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only a part of the embodiments of the present application, rather than all of the embodiments. For those of ordinary skill in the art, without creative efforts, other drawings obtained based on these drawings all belong to the scope protected by the present application.

[0028] Figure 1 It is a schematic structural diagram of the protection circuit provided by the embodiment of the present application;

[0029] Figure 2 It is a schematic structural diagram of the protection circuit provided in the related art;

[0030] Figure 3 For Figure 1 The first application embodiment of the Schottky diode as the transistor unit in the shown protection circuit;

[0031] Figure 4 For Figure 1The second application embodiment of the Schottky diode as a transistor unit in the protection circuit shown;

[0032] Figure 5 For Figure 1 The third application embodiment of the Schottky diode as a transistor unit in the protection circuit shown;

[0033] Figure 6 For Figure 1 The first application embodiment of the bipolar junction transistor as a transistor unit in the protection circuit shown;

[0034] Figure 7 For Figure 1 The second application embodiment of the bipolar junction transistor as a transistor unit in the protection circuit shown;

[0035] Figure 8 For Figure 1 The third application embodiment of the bipolar junction transistor as a transistor unit in the protection circuit shown;

[0036] Figure 9 For Figure 1 The first application embodiment of the bipolar junction transistor and the Schottky diode as transistor units in the protection circuit shown;

[0037] Figure 10 For Figure 1 The second application embodiment of the bipolar junction transistor and the Schottky diode as transistor units in the protection circuit shown;

[0038] Figure 11 For Figure 1 The third application embodiment of the bipolar junction transistor and the Schottky diode as transistor units in the protection circuit shown;

[0039] Figure 12 For Figure 1 The fourth application embodiment of the bipolar junction transistor and the Schottky diode as transistor units in the protection circuit shown;

[0040] Figure 13 For Figure 1 The fifth application embodiment of the bipolar junction transistor and the Schottky diode as transistor units in the protection circuit shown;

[0041] Figure 14 For Figure 1 The sixth application embodiment of the bipolar junction transistor and the Schottky diode as transistor units in the protection circuit shown;

[0042] Figure 15 The circuit schematic diagram of the single - ended power amplifier provided by the embodiment of the present application;

[0043] Figure 16 ForFigure 15 Schematic diagram of the structure of a single - ended power amplifier connected with several protection circuits;

[0044] Figure 17 For Figure 15 Connection relationship diagram of the single - ended power amplifier and the output impedance matching network;

[0045] Figure 18 Circuit schematic diagram of the differential power amplifier provided by the embodiment of the present application;

[0046] Figure 19 Circuit schematic diagram of the Doherty power amplifier provided by the embodiment of the present application;

[0047] Figure 20 Circuit schematic diagram of the balanced power amplifier provided by the embodiment of the present application;

[0048] Explanation of reference numerals:

[0049] 10 - First diode unit; 11 - First diode; 20 - Second diode unit; 30 - Transistor unit; 31 - Schottky diode; 32 - Bipolar junction transistor; 40 - Power amplification transistor; 41 - Output impedance matching network; 100 - Protection circuit. Detailed implementation manners

[0050] In order to make the objectives, technical solutions and advantages of the present application more clear and understandable, the present application will be further described in detail below with reference to the drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0051] In order to make the description of the present disclosure more detailed and complete, the following provides an illustrative description of the implementation manners and specific embodiments of the present application; however, this is not the only form for implementing or applying the specific embodiments of the present application. The implementation manners cover the features of multiple specific embodiments and the method steps and their sequences for constructing and operating these specific embodiments. However, other specific embodiments can also be used to achieve the same or equivalent functions and step sequences. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present application.

[0052] It should be noted that the terms "first", "second", etc. in the specification, claims and drawings of the present application are used to distinguish similar objects and do not necessarily need to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein.

[0053] In the description of the embodiments of the present application, unless otherwise specified, " / " means "or". For example, A / B may mean A or B. The "and / or" in the text is merely a description of the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of the present application, "a plurality" means two or more than two, and other quantifiers should be understood similarly. The preferred embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application. And without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other.

[0054] Please refer to Figures 1 - 20 , the present application provides a protection circuit, a power amplifier and a radio frequency front-end module, which can reduce the loss of the saturation efficiency of the power amplifier while ensuring the circuit protection effect. Please refer to Figure 1 , which is a schematic structural diagram of the protection circuit provided by the embodiment of the present application. The protection circuit includes a signal input end and a ground end, and further includes a first diode unit 10, a second diode unit 20 and a transistor unit 30.

[0055] Further, the above-mentioned first diode unit 10 includes at least a first diode 11. The transistor unit 30 is connected in series with each of the above-mentioned first diodes 11 between the signal input end and the ground end, and the conduction voltage drop of the transistor unit 30 is configured to be less than the conduction voltage drop of the first diode 11.

[0056] Please refer to Figure 2 , which is a schematic structural diagram of the protection circuit provided in the related art. In the application of the traditional power amplifier, in order to avoid the failure of the power amplifier during high-power output, a protection circuit as shown in the figure is usually set at the output end of the power amplifier. It can be observed that the protection circuit provided in the related art includes a first diode unit 10 and a second diode unit 20. The first diode unit 10 is connected between the signal input end and the ground end, and the second diode unit 20 is reversely connected in parallel at both ends of the first diode unit 10. Since the conduction voltage drop of the first diode 11 in the first diode unit 10 is large, the value step of the protection circuit will increase, and the saturation efficiency of the power amplifier is easily lost.

[0057] Specifically, the clamping voltage of the protection circuit is negatively correlated with the saturation efficiency of the PA (Power Amplifier), that is, the lower the clamping voltage of the protection circuit, the better the protection effect, but the greater the loss of the PA saturation efficiency. Therefore, in order to avoid the loss of the PA saturation efficiency, it is necessary to appropriately increase the clamping voltage of the protection circuit.

[0058] In some alternative embodiments, please continue to refer to Figure 2, in the related art, on the basis of the protection circuit shown in Figure 2 , a first diode 11 is further added to increase the clamping voltage that the protection circuit can achieve. However, due to the large forward voltage drop of the first diode 11, the clamping voltage is greatly increased, resulting in a significant reduction in the protection effect of the protection circuit. In order to improve the protection effect, the first diode 11 is removed. Although the protection effect will be improved, it will also cause a loss in the protection efficiency of the PA. Therefore, a new protection circuit is needed to balance the saturation efficiency of the PA and the protection effect of the protection circuit.

[0059] Please continue to refer to Figure 1 . In the present application, a first diode unit 10 and a transistor unit 30 are provided between the signal input terminal and the ground terminal. Since the forward voltage drop of the transistor unit 30 is less than that of the first diode 11 in the first diode unit 10, the value step of the protection circuit will become smaller, and the clamping voltage of the protection circuit will not be greatly increased, thereby improving the saturation efficiency of the power amplifier while achieving the protection effect of the protection circuit.

[0060] Furthermore, the second diode unit 20 provided in the present application is reversely connected in parallel across the first diode unit 10 and the transistor unit 30. It can be observed that the second diode unit 20 is provided with a first end and a second end. The first end of the second diode unit 20 is connected to the ground terminal, and the second end of the second diode unit 20 is connected to the signal input terminal. Among them, the first end of the second diode unit 20 is the anode, and the second end is the cathode, so as to be reversely connected in parallel across the first diode unit 10 and the transistor unit 30. The present application clamps the output voltage of the power amplifier through the forwardly arranged first diode unit 10 and transistor unit 30 to prevent the power amplifier from being damaged due to excessive output voltage. In addition, for the instantaneous voltage caused by static electricity, the present application protects the forward instantaneous voltage through the first diode unit and the transistor unit, and protects the reverse instantaneous voltage through the reversely connected second diode unit, thereby avoiding damage to the power amplifier caused by static electricity voltage.

[0061] In some alternative embodiments, the transistor unit 30 includes at least one Schottky diode 31. The Schottky diode 31 is connected in series with the first diode unit 10 between the signal input terminal and the ground terminal, and the forward voltage drop of the Schottky diode 31 is less than that of a single first diode 11 in the first diode unit 10.

[0062] Specifically, the first diode 11 is a PN junction semiconductor device made with a P-type semiconductor as the positive electrode and an N-type semiconductor as the negative electrode. Its forward conduction voltage is related to the semiconductor material used. In a power amplifier, the forward conduction voltage of the diode is usually greater than that of a common silicon diode, reaching above 1V. The Schottky diode 31 has a metal as the positive electrode and an N-type semiconductor as the negative electrode, and is a metal-semiconductor device made using the rectifying characteristics of the potential barrier formed on the contact surface between the two. Its conduction voltage is much lower than that of a common diode.

[0063] Exemplarily, the conduction voltage drop of the first diode 11 of the present application is 1.4V, and the conduction voltage drop of the Schottky diode 31 is less than or equal to 0.6V. Obviously, the conduction voltage drop of the Schottky diode 31 is less than that of the first diode 11, meeting the requirement that the transistor unit 30 is less than the conduction voltage drop of a single first diode 11 in the first diode unit 10.

[0064] Specifically, the Schottky diode 31 can be disposed between the signal input end and the first diode unit 10. Please refer to Figure 3 , for Figure 1 Example 1 of the application of the Schottky diode 31 as the transistor unit 30 in the protection circuit shown. Taking the case where there is one Schottky diode 31 disposed in the transistor unit 30 as an example, the first end of the Schottky diode 31 is connected to the signal input end, the second end of the Schottky diode 31 is connected to the first end of the first diode unit 10, and the second end of the first diode unit 10 is connected to the ground end.

[0065] Please refer to Figure 4 , for Figure 1 Example 2 of the application of the Schottky diode 31 as the transistor unit 30 in the protection circuit shown. The Schottky diode 31 can be disposed between the first diode unit 10 and the ground end. Specifically, the first end of the first diode unit 10 is connected to the signal input end, the second end of the first diode unit 10 is connected to the first end of the Schottky diode 31, and the second end of the Schottky diode 31 is connected to the ground end.

[0066] Please refer to Figure 5 , for Figure 1 Example 3 of the application of the Schottky diode 31 as the transistor unit 30 in the protection circuit shown. When there are two or more first diodes 11 in the first diode unit 10, the Schottky diode 31 can be disposed between two adjacent first diodes 11. At this time, the first end of the Schottky diode 31 can be connected to the cathode of the adjacent first diode 11, and the second end of the Schottky diode 31 can be connected to the anode of the adjacent first diode 11.

[0067] In a specific embodiment provided by the present application, the first end of the Schottky diode 31 is the anode of the Schottky diode 31, and the second end of the Schottky diode 31 is the cathode of the Schottky diode 31.

[0068] Taking the example that there is one first diode 11 in the first diode unit 10, at this time, the first end of the first diode unit 10 is the anode of the first diode 11, and the second end of the first diode unit 10 is the cathode of the first diode 11. Since the forward voltage drop of the first diode 11 in the first diode unit 10 is 1.4V, while the conduction voltage drop of the Schottky diode 31 is 0.6V or even lower, the requirement that the forward voltage drop of the transistor unit 30 is less than the conduction voltage drop of the first diode 11 is thus satisfied.

[0069] Optionally, one or two Schottky diodes 31 can also be added according to requirements. Such a setting will not cause a significant increase in the clamping voltage of the protection circuit, and can improve the saturation efficiency of the power amplifier while achieving the protection effect of the protection circuit, thereby improving the reliability and safety of the power amplifier.

[0070] It can be understood that on the premise that the clamping voltage of the protection circuit meets the requirements, the present application does not further limit the specific number of Schottky diodes 31 in the transistor unit 30 and the connection sequence with the first diode unit 10. As long as the transistor unit 30 and the first diode unit 10 are connected in series between the signal input end and the ground end, and the conduction voltage drop of the transistor unit 30 is less than the conduction voltage drop of the first diode 11, such a setting method is feasible, and those skilled in the art should be aware of this.

[0071] For example, when the clamping voltage of the protection circuit needs to be set within the range of 4.5V to 5V, 3 first diodes 11 and 1 Schottky diode 31 can be selected to be connected in series to achieve a clamping voltage of 4.8V, or 2 first diodes 11 and 3 to 5 Schottky diodes 31 can be selected to be connected in series.

[0072] As an optional implementation manner, the above transistor unit 30 includes at least one bipolar junction transistor 32. The bipolar junction transistor 32 is connected in series with the first diode unit 10 between the signal input end and the ground end. In the present application, the first end and the second end of the bipolar junction transistor 32 are short-circuited to make the conduction voltage drop of the bipolar junction transistor 32 less than the conduction voltage drop of a single first diode 11 in the first diode unit 10. Exemplarily, if the conduction voltage drop of the short-circuited bipolar junction transistor 32 is 1.25V and the conduction voltage drop of a single first diode 11 is 1.4V, the conduction voltage drop of the short-circuited bipolar junction transistor 32 is less than the conduction voltage drop of a single first diode 11.

[0073] Specifically, the bipolar junction transistor 32 can be disposed between the signal input terminal and the first diode unit 10. Please refer to Figure 6 , for Figure 1 FIG. 1, which is Application Example 1 of the bipolar junction transistor 32 as the transistor unit 30 in the protection circuit shown. Taking the example that there is one bipolar junction transistor 32 in the transistor unit 30, it can be observed that the first end of the bipolar junction transistor 32 is connected to the signal input terminal, the third end of the bipolar junction transistor 32 is connected to the first end of the first diode unit 10, and the second end of the first diode unit 10 is connected to the ground terminal.

[0074] Please refer to Figure 7 , for Figure 1 FIG. 2, which is Application Example 2 of the bipolar junction transistor 32 as the transistor unit 30 in the protection circuit shown. The bipolar junction transistor 32 can be disposed between the first diode unit 10 and the ground terminal. At this time, the first end of the first diode unit 10 is connected to the signal input terminal, the second end of the first diode unit 10 is connected to the first end of the bipolar junction transistor 32, and the third end of the bipolar junction transistor 32 is connected to the ground terminal.

[0075] Please refer to Figure 8 , for Figure 1 FIG. 3, which is Application Example 3 of the bipolar junction transistor 32 as the transistor unit 30 in the protection circuit shown. When there are two or more first diodes 11 in the first diode unit 10, the bipolar junction transistor 32 can be disposed between two adjacent first diode units 10. It can be observed that the first end of the bipolar junction transistor 32 is connected to the cathode of the adjacent first diode 11, and the third end of the bipolar junction transistor 32 is connected to the anode of the adjacent first diode 11.

[0076] Optionally, the above bipolar junction transistor 32 can be set as a homojunction bipolar transistor or an HBT (Heterojunction bipolar transistor). In principle, an appropriate bipolar junction transistor 32 can be selected according to actual requirements. The specific setting form of the bipolar junction transistor 32 is not further limited in this application.

[0077] In a specific embodiment provided by the present application, the first end of the bipolar junction transistor 32 is the collector of the bipolar junction transistor 32, the second end of the bipolar junction transistor 32 is the base of the bipolar junction transistor 32, and the third end of the bipolar junction transistor 32 is the emitter of the bipolar junction transistor 32. In the present application, the collector and the emitter of the bipolar junction transistor 32 are short-circuited. Since the forward voltage drop of the first diode 11 in the first diode unit 10 is 1.4V, and the conduction voltage drop of the short-circuited bipolar junction transistor 32 is 1.25V or even lower, the forward voltage drop of the bipolar junction transistor 32 is less than the conduction voltage drop of the first diode 11. Therefore, when the bipolar junction transistor 32 is connected to the first diode unit 10, it will not cause a significant increase in the clamping voltage of the protection circuit, and while achieving the protection effect of the protection circuit, the saturation efficiency of the power amplifier is improved.

[0078] It can be understood that on the premise that the clamping voltage of the protection circuit meets the requirements, the present application does not further limit the specific number of the bipolar junction transistors 32 in the transistor unit 30 and the connection sequence with the first diode unit 10. As long as the transistor unit 30 and the first diode unit 10 are connected in series between the signal input end and the ground end, and the conduction voltage drop of the transistor unit 30 is less than the conduction voltage drop of the first diode 11, such a setting method is feasible, and those skilled in the art should be aware of this.

[0079] Optionally, on the premise that the clamping voltage of the protection circuit meets the requirements, individual first diodes 11 in the first diode unit 10 can also be replaced with the above-mentioned bipolar junction transistors 32. Such a setting will not cause a significant increase in the clamping voltage of the protection circuit, and can also improve the saturation efficiency of the power amplifier while achieving the protection effect of the protection circuit, thus taking into account the saturation efficiency and safety of the power amplifier.

[0080] As an optional implementation manner, the transistor unit 30 may include at least one Schottky diode 31 and at least one bipolar junction transistor 32. The Schottky diode 31, the bipolar junction transistor 32, and the first diode unit 10 are connected in series between the signal input end and the ground end. Similarly, the first end and the second end of the bipolar junction transistor 32 need to be short-circuited.

[0081] Please refer to Figure 9 For Figure 1In the protection circuit shown, the bipolar junction transistor 32 and the Schottky diode 31 are used as Application Example 1 of the transistor unit 30. The first diode unit 10 can be connected to the signal input terminal, the bipolar junction transistor 32 can be connected to the ground terminal, and the Schottky diode 31 can be arranged between the first diode unit 10 and the bipolar junction transistor 32. It can be observed that the first end of the first diode unit 10 is connected to the signal input terminal, the second end of the first diode unit 10 is connected to the first end of the Schottky diode 31, the second end of the Schottky diode 31 is connected to the first end of the bipolar junction transistor 32, and the third end of the bipolar junction transistor 32 is grounded.

[0082] As an alternative implementation, please refer to Figure 10 , for Figure 1 In the protection circuit shown, the bipolar junction transistor 32 and the Schottky diode 31 are used as Application Example 2 of the transistor unit 30. The first diode unit 10 can be connected to the signal input terminal, the Schottky diode 31 can be connected to the ground terminal, and the bipolar junction transistor 32 can be arranged between the first diode unit 10 and the Schottky diode 31. It can be observed that the first end of the first diode unit 10 is connected to the signal input terminal, the second end of the first diode unit 10 is connected to the first end of the bipolar junction transistor 32, the third end of the bipolar junction transistor 32 is connected to the first end of the Schottky diode 31, and the second end of the Schottky diode 31 is grounded.

[0083] As an alternative implementation, please refer to Figure 11 , for Figure 1 In the protection circuit shown, the bipolar junction transistor 32 and the Schottky diode 31 are used as Application Example 3 of the transistor unit 30. The Schottky diode 31 can be connected to the signal input terminal, the bipolar junction transistor 32 can be connected to the ground terminal, and the first diode unit 10 can be arranged between the Schottky diode 31 and the bipolar junction transistor 32. It can be observed that the first end of the Schottky diode 31 is connected to the signal input terminal, the second end of the Schottky diode 31 is connected to the first end of the first diode unit 10, the second end of the first diode unit 10 is connected to the first end of the bipolar junction transistor 32, and the third end of the bipolar junction transistor 32 is grounded.

[0084] In some alternative embodiments, please refer to Figure 12 , for Figure 1In the illustrated protection circuit, bipolar junction transistor 32 and Schottky diode 31 are used as Application Example 4 of transistor unit 30. The Schottky diode 31 can be connected to the signal input terminal, the first diode unit 10 can be connected to the ground terminal, and the bipolar junction transistor 32 can be arranged between the Schottky diode 31 and the first diode unit 10. At this time, the first terminal of the Schottky diode 31 is connected to the signal input terminal, the second terminal of the Schottky diode 31 is connected to the first terminal of the bipolar junction transistor 32, the third terminal of the bipolar junction transistor 32 is connected to the first terminal of the first diode unit 10, and the second terminal of the first diode unit 10 is grounded.

[0085] In some alternative embodiments, please refer to Figure 13 , for Figure 1 In the illustrated protection circuit, bipolar junction transistor 32 and Schottky diode 31 are used as Application Example 5 of transistor unit 30. The bipolar junction transistor 32 can be connected to the signal input terminal, the Schottky diode 31 can be connected to the ground terminal, and the first diode unit 10 can be arranged between the bipolar junction transistor 32 and the Schottky diode 31. It can be observed that the first terminal of the bipolar junction transistor 32 is connected to the signal input terminal, the third terminal of the bipolar junction transistor 32 is connected to the first terminal of the first diode unit 10, the second terminal of the first diode unit 10 is connected to the first terminal of the Schottky diode 31, and the second terminal of the Schottky diode 31 is grounded.

[0086] As an alternative implementation, please refer to Figure 14 , for Figure 1 In the illustrated protection circuit, bipolar junction transistor 32 and Schottky diode 31 are used as Application Example 6 of transistor unit 30. The bipolar junction transistor 32 can be connected to the signal input terminal, the first diode unit 10 can be connected to the ground terminal, and the Schottky diode 31 can be arranged between the bipolar junction transistor 32 and the first diode unit 10. It can be observed that the first terminal of the bipolar junction transistor 32 is connected to the signal input terminal, the third terminal of the bipolar junction transistor 32 is connected to the first terminal of the Schottky diode 31, the second terminal of the Schottky diode 31 is connected to the first terminal of the first diode unit 10, and the second terminal of the first diode unit 10 is grounded.

[0087] Of course, when there are several first diodes 11 in the first diode unit 10, the above bipolar junction transistor 32 can be arranged between two adjacent first diodes 11, or the above Schottky diode 31 can be arranged between two adjacent first diodes 11. Of course, the Schottky diode 31 and the bipolar junction transistor 32 can also be arranged together between two adjacent first diode units 10. The above arrangement methods are all feasible, and the present application will not enumerate them here.

[0088] It should be noted that the combination of the Schottky diode 31 and / or the bipolar junction transistor 32 in the transistor unit 30 can be selected according to actual needs. In principle, the conduction voltage drop generated by the combination of the Schottky diode 31 and / or the bipolar junction transistor 32 should be close to the required conduction voltage drop. And in practical applications, factors such as the area of the protection circuit can be comprehensively considered to minimize the occupied area of the protection circuit and improve the integration of the power amplifier.

[0089] It can be understood that on the premise that the clamping voltage of the protection circuit meets the requirements, the present application does not further limit the specific number of the Schottky diode 31 and / or the bipolar junction transistor 32 in the transistor unit 30, nor the connection sequence between them and the first diode unit 10. As long as the transistor unit 30 and the first diode unit 10 are connected in series between the signal input end and the ground end, and the conduction voltage drop of the transistor unit 30 is less than the conduction voltage drop of the first diode 11, such a setting method is feasible, and those skilled in the art should be aware of this.

[0090] For example, when the clamping voltage of the protection circuit needs to be set in the range of 4.5V to 5V, 3 first diodes 11 can be selected and connected in series with 1 Schottky diode 31 to achieve a clamping voltage of 4.8V. It is also possible to select 2 first diodes 11, 1 bipolar junction transistor 32, and 1 Schottky diode 31 and connect them in series. As long as the clamping voltage of the protection circuit meets the requirements, the adjustment of the number of the above-mentioned first diodes 11, Schottky diodes 31, and / or bipolar junction transistors 32 is feasible, and the present application will not elaborate on this too much here.

[0091] As an alternative implementation manner, please continue to refer to Figures 3 - 14 , it can be observed that the second diode unit 20 provided by the present application includes at least one second diode, and the conduction voltage drop of the transistor unit 30 should be less than the conduction voltage drop of the second diode in the second diode unit 20. The second diode unit 20 connected in reverse parallel plays a role in preventing the extremely large instantaneous voltage generated by static electricity from damaging the operational amplifier PA.

[0092] As an alternative implementation manner, for the convenience of description, the series-connected first diode unit 10 and transistor unit 30 are called the forward protection branch, and the second diode unit 20 is called the reverse protection branch. Then, the protection circuit provided by the present application can include at least two forward protection branches, that is, at least two groups of the first diode unit 10 and the transistor unit 30. The conduction voltage drops of the respective forward protection branches can be the same, and every two forward protection branches are connected in parallel with each other to improve the current-carrying capacity of the protection circuit.

[0093] Optionally, the protection circuit may also include at least two second diode units 20 connected in parallel with each other to improve the current-carrying capacity for electrostatic current.

[0094] Based on the above protection circuit, the present application further provides a power amplifier, which includes an amplification circuit and the above protection circuit, and the signal input end of the protection circuit can be connected to the output end of the power amplification circuit.

[0095] Since the output voltage at the output end of the power amplifier is the superposition of a DC voltage and a radio frequency voltage swing, the power amplifier is prone to failure at high voltages. Therefore, the above protection circuit can be connected to the output end of the power amplifier to reduce and clamp the output voltage, preventing the output voltage at the output end from being too large and causing damage to the power amplifier.

[0096] Please refer to Figure 15 FIG. [FIG. number not provided in the original] is a circuit schematic diagram of a single-ended power amplifier provided by an embodiment of the present application. Since the conduction voltage drops of the first diode unit 10, the transistor unit 30, and the second diode unit 20 are fixed, taking the example that the first diode unit 10 is provided with 3 first diodes 11 and a Schottky diode 31, if the conduction voltage drop of the first diode unit 10 is 1.4V and the conduction voltage drop of the Schottky diode 31 is 0.6V, the conduction voltage drop generated by the 3 series-connected first diodes 11 and the Schottky diode 31 is 4.8V. When the output voltage at the output end of the power amplifier is greater than 4.8V, the above 3 series-connected first diodes 11 and the Schottky diode 31 will conduct, thereby clamping the output voltage at the output end of the power amplifier at 4.8V, thus avoiding the output voltage of the power amplifier from being too large and improving the saturation efficiency of the power amplifier at the same time.

[0097] The second diode unit 20 connected in reverse parallel at both ends after the first diode unit 10 and the transistor unit 30 are connected in series can prevent the power amplifier from being damaged by electrostatic voltage. When electrostatic is generated at the output port of the power amplifier, the electrostatic may generate a very large instantaneous voltage, which may be positive or negative. The first diode unit 10 and the transistor unit 30 can protect against the positive instantaneous voltage, and the second diode unit 20 connected in reverse parallel can protect against the negative instantaneous voltage. Therefore, the protection circuit 100 provided by the present application can avoid damage to the power amplifier caused by electrostatic voltage.

[0098] In some embodiments, the above power amplifier can be configured in the form of a single-ended power amplifier, and the signal input end of the protection circuit 100 is connected to the output end of the single-ended power amplifier. Please continue to refer to Figure 15, the single - ended power amplifier includes a power - amplification circuit. In the power - amplification circuit, there is at least one power - amplification transistor 40, or several parallel - connected power - amplification transistors 40 can also be provided. The present application does not further limit the number of power - amplification transistors 40. When the power - amplification circuit includes multiple parallel - connected transistors 40, the output ends of multiple parallel - connected power - amplification transistors 40 in the same power - amplification circuit can be connected to the same protection circuit 100.

[0099] Please refer to Figure 16 , for Figure 15 the schematic structural diagram of a single - ended power amplifier connected with several protection circuits 100. When several protection circuits 100 are provided in the power amplifier, several protection circuits 100 can be connected in parallel and then commonly connected to the output end of the power - amplification transistor 40, so as to protect the single - ended power amplifier through the protection circuit 100. Due to the clamping effect of the first diode unit 10 and the transistor unit 30, when the single - ended power amplifier outputs at a high power, the output voltage at the output end can be limited within the clamping voltage, thereby protecting the power - amplification transistor 40 from failure.

[0100] Specifically, the protection circuit 100 needs to be directly connected to the output end of the power - amplification transistor 40 to directly protect the output end of the power - amplification transistor 40.

[0101] As an optional implementation manner, several parallel - connected protection circuits 100 can also be connected to the output end of the power - amplification transistor 40 according to actual design requirements to meet the design needs of different output powers of the power amplifier. For example, in order to improve the current - carrying capacity of the protection circuit 100 and avoid component failure caused by over - current, the overall current - carrying capacity of the protection circuit 100 can be increased by setting multiple parallel - connected protection circuits 100 at the output end of the power - amplification transistor 40. It can also make the protection effect of the protection circuit 100 on the power amplifier more balanced, ensuring that the voltage swings of all components in the power - amplification circuit are protected.

[0102] In some optional implementation manners, the above - mentioned power amplifier can also be set as a differential power amplifier, a Doherty power amplifier (Doherty PA), a balanced power amplifier (Balance PA), a push - pull power amplifier, or other power amplifiers including at least two power - amplification circuits.

[0103] Specifically, these power amplifiers mentioned above all include at least two power - amplification circuits, and each power - amplification circuit includes at least one power - amplification transistor 40. Of course, each power - amplification circuit can also include several power - amplification transistors 40. The present application does not further limit the number of power - amplification transistors 40 provided in the power - amplification circuit.

[0104] Furthermore, since at least two power amplification circuits are provided in each of the above power amplifiers, and each power amplification circuit includes at least one power amplification transistor 40, the number of protection circuits 100 is also set to at least two, and the output ends of at least two power amplification transistors 40 are respectively connected to the corresponding protection circuits 100.

[0105] Optionally, taking the case where two power amplification circuits are provided in the power amplifier as an example for illustration, at this time, the output ends of each power amplification circuit should be respectively connected to at least one protection circuit 100. For the same power amplification circuit, when it includes multiple power amplification transistors 40 connected in parallel, the output end of each power amplification transistor 40 is connected to the protection circuit 100 corresponding to this power amplification circuit.

[0106] Certainly, according to the actual output power requirement of the power amplifier, several protection circuits 100 connected in parallel can also be provided at the output connection of each power amplification circuit to increase the overall current-carrying capacity of the protection circuit 100. Preferably, the number of protection circuits 100 provided at the output ends of the two power amplification circuits can be equal, so that the protection effect of the protection circuit 100 on the power amplifier is more balanced, ensuring that the voltage swings of all components in the power amplification circuit are protected.

[0107] Please refer to Figure 18 、 Figure 19 and Figure 20 wherein, Figure 18 is the circuit schematic diagram of the differential power amplifier provided by the embodiment of the present application, Figure 19 is the circuit schematic diagram of the Doherty power amplifier provided by the embodiment of the present application, Figure 20 is the circuit schematic diagram of the balanced power amplifier provided by the embodiment of the present application; it can be observed that at least two power amplification circuits are provided in the above differential power amplifier, Doherty power amplifier and balanced power amplifier, and one power amplification transistor 40 or at least two power amplification transistors 40 connected in parallel are provided in each power amplification circuit. It can be observed that at least one corresponding protection circuit 100 is connected to the output ends of the two power amplification circuits, and the number of protection circuits 100 provided at the output ends of the two power amplification transistor circuits is equal, so that the protection effect of the protection circuit 100 on the power amplifier is more balanced, ensuring that the voltage swings of all components in the power amplification circuit are protected.

[0108] Certainly, the protection circuit provided by the present application can also be applied to other power amplifiers, as long as the signal input end of the protection circuit is connected to the output end of the power amplification circuit in the power amplifier. The present application does not further limit the specific selection of the power amplifier.

[0109] It should be noted that various power amplifiers involved in the embodiments of the present application, such as single-ended power amplifiers, differential power amplifiers, Doherty power amplifiers, and balanced power amplifiers, can all be single-stage power amplifiers or multi-stage power amplifiers. When it is a multi-stage power amplifier, at least the output end of the last-stage power amplification circuit is provided with the above-mentioned protection circuit, and the previous-stage power amplification circuit can be provided or not provided with the above-mentioned protection circuit, and the present application does not make any limitations in this regard.

[0110] As an optional implementation manner, please refer to Figure 17 , for Figure 15 the connection relationship diagram of the single-ended power amplifier and the output impedance matching network 41 shown. Taking the single-ended power amplifier as an example, an output impedance matching network 41 can also be provided between the output end of the power amplification transistor 40 and the output end of the single-ended power amplifier. The input end of the output impedance matching network 41 should be connected to the output end of the power amplification transistor 40 and be provided after the protection circuit 100 to convert the output impedance of the single-ended power amplifier to match the impedance of the subsequent circuit.

[0111] Among them, the signal input end b of the protection circuit 100 should be set between the output end of the power amplification transistor 40 and the input end of the output impedance matching network 41, that is, the protection circuit 100 should be provided before the power amplification transistor 40, so that the signal input end of the protection circuit 100 is directly connected to the output end of the power amplification transistor 40 to directly protect the output end of the power amplification transistor 40.

[0112] Since the impedance increases and the voltage also becomes higher after the RF signal passes through the output impedance matching network 41, if the protection circuit 100 is connected after the output impedance matching network 41, more first diodes 11 need to be provided to protect the power amplification transistor 40, increasing the area of the required protection circuit 100, and the protection circuit 100 provided at the output end of the output impedance matching network 41 cannot accurately correspond to the output voltage at the output end of the power amplification transistor 40 and cannot accurately protect the power amplification transistor 40. Therefore, the output impedance matching network 41 needs to be provided on the right side of node b, that is, the impedance matching network 41 should be provided after the input end of the protection circuit 100.

[0113] In some optional implementation manners, a choke coil (not shown in the figure) can also be provided in the Figures 15 - 17 single-ended power amplifier shown. The choke coil is an inductor, mainly used to block the passage of high-frequency alternating current and prevent the leakage of the RF output signal of the power amplification circuit. The choke coil can be provided between node a and the VCC port. Of course, it can also be in Figures 15 - 17In the single - ended power amplifier shown, other components are added according to actual application requirements to achieve the required functions, and this application does not make further restrictions on this.

[0114] It should be noted that, in addition to the single - ended power amplifier in the above example, the above - mentioned impedance matching network 41 and choke coil can be arranged in differential power amplifiers, Doherty power amplifiers, balanced power amplifiers and other common power amplifiers according to actual needs. In principle, it only needs to meet the positional relationship that the impedance matching network 41 is arranged after the protection circuit 100 and the choke coil is arranged between node a and the VCC port. This application will not elaborate too much on this here.

[0115] Based on the above protection circuit and power amplifier, this application also provides a radio frequency front - end module. For other details of how this radio frequency front - end module implements the above technical solutions, reference can be made to the descriptions of the protection circuit and power amplifier provided in the above - mentioned application embodiments, and details will not be elaborated here.

[0116] In the protection circuit, power amplifier and radio frequency front - end module provided by this application, a first diode unit and a transistor unit are arranged between the signal input end and the ground end. Since the conduction voltage drop of the transistor unit is less than the conduction voltage drop of a single first diode in the first diode unit, the step value of the protection circuit will become smaller, and it will not cause a large increase in the clamping voltage of the protection circuit; the number of first diodes in the first diode unit, as well as the Schottky diodes and / or bipolar junction transistors in the transistor unit, can also be adjusted according to requirements, avoiding a large increase in the clamping voltage of the protection circuit, and being able to improve the saturation efficiency of the power amplifier while achieving the protection effect of the protection circuit.

[0117] In addition, for the instantaneous voltage caused by static electricity, this application uses the first diode unit and the transistor unit to protect against the forward instantaneous voltage, and uses the second diode unit connected in reverse parallel to protect against the reverse instantaneous voltage, thereby avoiding damage to the power amplifier caused by static electricity voltage.

[0118] The above - described embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, 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 for some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A protection circuit, characterized in that: It includes a signal input terminal and a ground terminal, and also includes a first diode unit, a second diode unit and a transistor unit; The first diode unit includes at least one first diode, the transistor unit and each of the first diodes are connected in series between the signal input terminal and the ground terminal, and a conduction voltage drop of the transistor unit is smaller than a conduction voltage drop of the first diode; A first end of the second diode unit is connected to the ground end, and a second end of the second diode unit is connected to the signal input end.

2. The protection circuit according to claim 1, characterized in that: The transistor unit includes at least one Schottky diode, and the Schottky diode is connected in series with the first diode unit between the signal input terminal and the ground terminal; Wherein, the first end of the Schottky diode is connected to the signal input end, and the second end of the Schottky diode is connected to the first end of the first diode unit; Alternatively, the first end of the Schottky diode is connected to the second end of the first diode unit, and the second end of the Schottky diode is connected to the ground end; Alternatively, the Schottky diode is connected in series between two adjacent first diode units.

3. The protection circuit according to claim 1, characterized in that: The transistor unit comprises at least one bipolar junction transistor, the bipolar junction transistor and the first diode unit are connected in series between the signal input terminal and the ground terminal, and the first terminal and the second terminal of the bipolar junction transistor are short-circuited; Wherein, the first end of the bipolar junction transistor is connected to the signal input end, and the third end of the bipolar junction transistor is connected to the first end of the first diode unit; Alternatively, the first end of the bipolar junction transistor is connected to the second end of the first diode unit, and the third end of the bipolar junction transistor is connected to the ground end; Alternatively, the bipolar junction transistor is connected in series between two adjacent first diodes.

4. The protection circuit according to claim 1, characterized in that: The transistor unit includes at least one Schottky diode and at least one bipolar junction transistor, the Schottky diode, the bipolar junction transistor and the first diode unit are connected in series between the signal input terminal and the ground terminal, and the first terminal and the second terminal of the bipolar junction transistor are short-circuited.

5. The protection circuit according to claim 1, characterized in that: The second diode unit includes at least one second diode, and a conduction voltage drop of the transistor unit is smaller than a conduction voltage drop of the second diode.

6. A power amplifier, characterized in that: The power amplifier comprises a power amplifier circuit and a protection circuit as claimed in any one of claims 1 to 5, wherein a signal input end of the protection circuit is connected to an output end of the power amplifier circuit.

7. The power amplifier according to claim 6, characterized in that The power amplifier is a single-ended power amplifier, the single-ended power amplifier comprises a power amplifier circuit, and the power amplifier circuit comprises at least one power amplifier transistor; The number of the protection circuits is configured to be at least one, and the output end of the power amplifier transistor is connected to at least one of the protection circuits.

8. The power amplifier according to claim 6, characterized in that The power amplifier comprises at least two power amplification circuits, each of which comprises at least one power amplification transistor; The number of the protection circuits is configured to be at least two, and the output ends of at least two of the power amplifier transistors are respectively connected to at least one of the protection circuits.

9. The power amplifier according to claim 8, characterized in that The power amplifier is a differential power amplifier, a push-pull power amplifier, a Doherty power amplifier or a balanced power amplifier.

10. A radio frequency front-end module, characterized in that: The RF front-end module includes the protection circuit as described in any one of claims 1-5, or includes the power amplifier as described in any one of claims 6-9.

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