Temperature protection method and device for power amplifier

Abstract

The invention discloses a temperature protection method of a power amplifier. The method comprises the following steps: generating a first current changing along with temperature; reference current which does not change along with the temperature is generated; comparing the first current with a reference current to obtain a difference value, generating a control current according to the difference value, when the difference value is a negative value, the control current is zero, and when the difference value is a positive value, the control current is a preset multiple of the difference value; the actual bias current of the power amplifier is adjusted by subtracting the control current from the reference bias current of the power amplifier. Temperature protection is achieved by detecting the temperature of the chip and dynamically adjusting the bias current, sudden change of the working state is avoided, and the power amplifier protection circuit has the advantages of being simple in circuit structure and adjustable in protection strength, can be applied to power amplifiers of different process platforms and is beneficial to improving the reliability of the power amplifiers.

Description

Technical Field

[0001] The present invention relates to the technical field of radio frequency power amplifier design, and in particular to a power amplifier temperature protection method and device. Background Art

[0002] RF power amplifiers generally have high output power, but their efficiency is generally low, especially linear power amplifiers, whose efficiency is usually no higher than 50%. This causes a large amount of DC power consumption to be converted into heat, which increases the chip temperature. The chip temperature of the RF power amplifier is affected by many factors, including output power, amplifier efficiency, operating voltage, load impedance, semiconductor materials, packaging method, and ambient temperature.

[0003] When the chip temperature is too high, it will seriously affect the performance of the RF power amplifier. For example, the increase in temperature will lead to problems such as reduced gain, deteriorated linearity, and increased noise factor. More seriously, excessively high chip temperature may directly cause the chip to burn out and cause device failure. This situation is particularly obvious when the output load impedance is mismatched, because the impedance mismatch will cause output power reflection, further exacerbating the chip's heating problem.

[0004] The temperature protection schemes for power amplifiers in the prior art often have some limitations. Some schemes use a protection mechanism triggered by a temperature threshold, which directly shuts down the power amplifier once the threshold is reached. This sudden change can cause communication interruption. Other schemes require complex control circuits and temperature sensors, which not only increase the chip area and cost, but also are difficult to implement on different process platforms. In addition, since the heat generation of the power amplifier chip is mainly concentrated in the output stage, the traditional temperature detection scheme often cannot accurately reflect the actual temperature of the hot spot area. Summary of the invention

[0005] The object of the present invention is to provide a method and device for temperature protection of a power amplifier, so as to solve the technical problems in the prior art that temperature protection of a power amplifier is not flexible enough and has poor process adaptability.

[0006] To achieve the above-mentioned purpose, the present invention provides a temperature protection method for a power amplifier, comprising: generating a first current that changes with the temperature of the power amplifier; generating a reference current that does not change with the temperature of the power amplifier; comparing the first current with the reference current to obtain a difference, and generating a control current according to the difference, wherein: when the difference is a negative value, the control current is zero; when the difference is a positive value, the control current is a preset multiple of the difference; and adjusting the actual bias current of the power amplifier by subtracting the control current from the reference bias current of the power amplifier.

[0007] Furthermore, the first current is generated by a temperature sensing module, and the reference current is generated by a reference current source in an over-temperature protection module.

[0008] Specifically, the first current may be a negative temperature coefficient current, in which case the difference is the difference between the reference current and the first current; or the first current may be a positive temperature coefficient current, in which case the difference is the difference between the first current and the reference current.

[0009] More specifically, the control current is generated by a current mirror.

[0010] The present invention also provides a temperature protection device for a power amplifier, comprising a temperature sensing module and an over-temperature protection module. The over-temperature protection module comprises a reference current source and a comparison circuit. The temperature sensing module is used to generate a first current that varies with temperature; the reference current source is connected to the output end of the temperature sensing module, and is used to generate a reference current that does not vary with temperature; the input end of the comparison circuit is respectively connected to the output end of the temperature sensing module and the reference current source, and is used to compare the first current with the reference current to obtain a difference, and generate a control current according to the difference.

[0011] Furthermore, the power amplifier includes a driving stage and an output stage, the output end of the comparison circuit is connected to the bias input ends of the driving stage and the output stage respectively, and the bias current includes a driving stage bias current and an output stage bias current.

[0012] More specifically, the temperature sensing module is arranged on a GaAs chip and includes an HBT device for temperature sensing, and the over-temperature protection module is arranged on a Si CMOS chip. The output stage includes a plurality of power units, and the HBT device is arranged at the center of the plurality of power units.

[0013] The temperature protection method and device provided by the present invention are used to generate a first current that changes with temperature through a temperature sensing module, and compare it with a reference current to obtain a difference, and generate a control current according to the difference. When the difference is a negative value, the control current is zero, and when the difference is a positive value, the control current is a preset multiple of the difference. The actual bias current is adjusted by subtracting the control current from the reference bias current. This temperature protection mechanism enables the power amplifier to smoothly reduce the bias current when the temperature exceeds a preset threshold, avoiding sudden changes in the working state, while ensuring the effectiveness of temperature protection.

[0014] By adopting a first current with a negative temperature coefficient or a positive temperature coefficient and using a current mirror to generate a control current, the circuit for implementing temperature protection is simple and reliable. For a power amplifier including a driving stage and an output stage, the bias currents of the two stages can be controlled separately to achieve more accurate temperature protection. By adjusting the multiple of the current mirror, the protection intensity can be flexibly set, so that the protection scheme of the present invention has better adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the basic structure of a radio frequency power amplifier in the prior art;

[0016] Figure 2 Schematic diagram of a temperature protection method according to an embodiment of the present invention;

[0017] Figure 3 This is a schematic diagram of the structure of a temperature protection device in one embodiment of the present invention;

[0018] Figure 4 It is a schematic diagram of the structure of a temperature sensing circuit in one embodiment of the present invention;

[0019] Figure 5 Schematic diagram of the circuit structure of the PA driver stage over-temperature protection module in one embodiment of the present invention;

[0020] Figure 6 Schematic diagram of the circuit structure of a PA output stage over-temperature protection module in one embodiment of the present invention;

[0021] Figure 7 A schematic diagram of the working characteristics of an over-temperature protection circuit in one embodiment of the present invention;

[0022] Figure 8 A schematic diagram of a chip layout when a CMOS process is implemented in one embodiment of the present invention;

[0023] Fig. 9 A schematic diagram of a dual-chip structure when GaAs process is implemented in one embodiment of the present invention;

[0024] Fig.10 A schematic diagram of a temperature sensing circuit when GaAs process is implemented in one embodiment of the present invention;

[0025] Fig.11 A schematic diagram of the layout of a GaAs process PA output stage in one embodiment of the present invention;

[0026] Fig.12 A schematic diagram of the output characteristics of a temperature sensing circuit in one embodiment of the present invention;

[0027] Fig.13 The figure is a schematic diagram of the structure of a radio frequency power amplifier with over-temperature protection in one embodiment of the present invention. DETAILED DESCRIPTION

[0028] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that the described embodiments are only used to explain the technical principles of the present invention, rather than to limit the scope of protection thereof. Those skilled in the art should understand that, without departing from the spirit and scope of the present invention, various changes, modifications or equivalent substitutions may be made to these embodiments. These changes, modifications or equivalent substitutions shall all be deemed to fall within the scope of protection defined by the claims of the present invention.

[0029] like Figure 1 The figure shows a radio frequency power amplifier structure in the prior art, including a PA driver stage PAD, a PA output stage PA and a bias circuit PA bias. The bias circuit PA bias is used to generate two bias currents IB_PAD and IB_PA, respectively providing bias for the PA driver stage PAD and the PA output stage PA. The PA driver stage PAD is used to provide sufficient drive signal and gain for the PA output stage PA, and the PA output stage PA directly drives an external 50Ω load or antenna.

[0030] In the prior art, RF power amplifiers generally have high output power, but their efficiency is low, especially linear power amplifiers, whose efficiency is generally not higher than 50%. Therefore, a large amount of DC power consumption is converted into heat, which causes the chip temperature to rise. The chip temperature of the RF power amplifier is closely related to the output power, amplifier efficiency, operating voltage, load impedance, semiconductor materials, packaging method, ambient temperature, etc. Excessive chip temperature will not only affect the performance of the RF power amplifier, but may also cause the chip to burn. Therefore, limiting the maximum temperature of the power amplifier chip is of great significance to improving the RF performance of the power amplifier and the reliability of the chip.

[0031] like Figure 2 As shown, in one embodiment, the present invention provides a temperature protection method for a power amplifier, comprising the following steps:

[0032] First, the first current that changes with temperature is generated by the temperature sensing module. The first current can be a negative temperature coefficient current or a positive temperature coefficient current. When it is a negative temperature coefficient current, the first current decreases as the temperature increases; when it is a positive temperature coefficient current, the first current increases as the temperature increases.

[0033] Secondly, the reference current source in the over-temperature protection module generates the reference current that does not change with temperature. The method for generating the reference current is a common method used by those skilled in the art and will not be described in detail.

[0034] Then, the first current is compared with the reference current to obtain a difference value. When the first current is a negative temperature coefficient current, the difference value is the difference between the reference current and the first current; when the first current is a positive temperature coefficient current, the difference value is the difference between the first current and the reference current.

[0035] Then, a control current is generated according to the difference. Specifically, when the difference is a negative value, the control current is zero; when the difference is a positive value, the control current is a preset multiple of the difference. The control current is generated by a current mirror, and the preset multiple is determined by the multiple of the current mirror. When the chip temperature is lower than the preset temperature threshold, the difference is a negative value, and the control current is zero, which does not affect the normal operation of the power amplifier; when the chip temperature is higher than the preset temperature threshold, the difference is a positive value, and the control current increases as the difference increases.

[0036] Finally, the actual bias current of the power amplifier is adjusted by subtracting the control current from the reference bias current of the power amplifier. The reference bias current is the bias current of the power amplifier when it is working normally. When there is no over-temperature protection, the actual bias current is equal to the reference bias current. When the chip temperature rises and exceeds the preset temperature threshold, the control current increases with the temperature rise, and the actual bias current decreases accordingly, thereby limiting the output power of the power amplifier and preventing the chip temperature from continuing to rise.

[0037] By adopting the above method, the maximum temperature of the chip during operation can be limited, the chip can be prevented from being burned due to high temperature, and the reliability of the chip can be improved. At the same time, since the control current changes gradually with the temperature, sudden changes in the temperature protection process are avoided, and the stability of the power amplifier operation is guaranteed. In addition, the intensity of the temperature protection will increase as the difference between the actual temperature and the preset temperature threshold increases, realizing intelligent temperature protection.

[0038] like Figure 3 As shown, in another embodiment, the present invention also provides a temperature protection device for a power amplifier. The device includes a temperature sensing module TS and an over-temperature protection module OTP. The temperature sensing module TS is used to generate a first current that varies with temperature, and the input end of the over-temperature protection module OTP is connected to the output end of the temperature sensing module TS.

[0039] The over-temperature protection module OTP includes a reference current source and a comparison circuit. The reference current source is used to generate a reference current that does not change with temperature. The comparison circuit includes an input end and an output end, and its input end is respectively connected to the output end of the temperature sensing module TS and the output end of the reference current source.

[0040] Specifically, the comparison circuit is used to compare the first current with the reference current to obtain a difference, and generate a control current according to the difference. When the difference is a negative value, the control current is zero; when the difference is a positive value, the control current is a preset multiple of the difference. The output end of the comparison circuit is connected to the bias input end of the power amplifier, and is used to adjust the actual bias current of the power amplifier by subtracting the control current from the reference bias current of the power amplifier.

[0041] In this embodiment, the power amplifier includes a driver stage PAD and an output stage PA, and the output end of the comparison circuit is connected to the bias input end of the driver stage PAD and the output stage PA respectively. The bias current includes a driver stage bias current IB_PAD and an output stage bias current IB_PA. By adjusting the bias currents of the driver stage PAD and the output stage PA respectively, the output power of the power amplifier can be more effectively controlled, thereby achieving more accurate temperature protection.

[0042] In a specific embodiment, the temperature sensing module TS is arranged on a GaAs chip, including an HBT device Q1 for temperature sensing, and the over-temperature protection module OTP is arranged on a Si CMOS chip. The output end of the temperature sensing module TS is connected to the over-temperature protection module OTP through an interface between the GaAs chip and the Si CMOS chip. This implementation is applicable to power amplifiers manufactured using GaAs technology.

[0043] Furthermore, the output stage PA includes a plurality of power cells Pcell, and the HBT device Q1 is arranged at the center of the plurality of power cells Pcell. Since the power cell Pcell of the output stage PA is the main heat source, the HBT device Q1 is arranged at the center of the power cell Pcell, so that the actual temperature of the chip can be detected more accurately, thereby improving the accuracy of temperature protection.

[0044] The temperature protection device provided in this embodiment detects the chip temperature in real time through the temperature sensing module TS, and timely adjusts the bias current of the power amplifier through the over-temperature protection module OTP, thereby realizing an effective temperature protection function. The device has a simple structure, is easy to implement, and can flexibly select the intensity of temperature protection according to actual needs, and has strong practicality. At the same time, due to the design of the discrete temperature sensing module TS and the over-temperature protection module OTP, the device is suitable for both CMOS process and GaAs process, and has strong versatility.

[0045] Combine the following Figures 4 to 6 The specific circuit implementation of the present invention is described in detail.

[0046] like Figure 4 As shown, the temperature sensing module TS can be implemented using two types of circuit structures. Figure 4 The circuit shown in (A) can generate a negative temperature coefficient current. Figure 4 The circuit shown in (B) can generate a positive temperature coefficient current. Both circuit structures are commonly used in the art, where the transistors Q1 and Q2 can be PNP tubes or NPN tubes, or can be replaced by diodes, which is common knowledge of those skilled in the art and will not be described in detail here.

[0047] like Figure 5 As shown, the circuit structure for controlling the bias current of the PA driving stage in the over-temperature protection module OTP includes two implementation modes. Figure 5 (A) corresponds to the case where the temperature sensing circuit outputs a negative temperature coefficient current. Figure 5 (B) corresponds to the situation where the temperature sensing circuit outputs a positive temperature coefficient current. Figure 5 In (A), the difference Idiff between the reference current Iref generated by the reference current source and the negative temperature coefficient current Ictat (TS) output by the temperature sensing module is converted into a control current Iotp via a current mirror circuit formed by M1 and M2. When the chip temperature exceeds the preset temperature threshold Tth_otp, the control current Iotp increases as the temperature rises. The final output driver bias current IB_PAD_OTP is equal to the reference bias current IB_PAD minus the control current Iotp.

[0048] like Figure 6 As shown in FIG. 1 , the circuit structure used to control the bias current of the PA output stage in the over-temperature protection module OTP is similar to Figure 5 The structures are the same. The output stage bias current IB_PA_OTP finally outputted is equal to the reference bias current IB_PA minus the control current Iotp.

[0049] The specific design of the current mirror circuit formed by the MOS tubes M1 and M2, including the selection of device size, setting of bias voltage, etc., belongs to the conventional means of those skilled in the art and will not be described in detail here.

[0050] It should be noted that Figure 5 and Figure 6 The circuit structure shown is only a preferred embodiment, and the over-temperature protection module OTP of the present invention is not limited to the above circuit structure. As long as the function of adjusting the bias current according to temperature changes can be achieved, other appropriate circuit structures can be used to achieve it, which is obvious to those skilled in the art.

[0051] The over-temperature protection circuit structure adopted in this embodiment is simple, and only a small number of components are needed to realize the temperature protection function, which is conducive to reducing costs and improving reliability. At the same time, by reasonably designing the multiples of the current mirror, the intensity of the temperature protection can be flexibly adjusted, which has strong practicality.

[0052] Combine the following Figures 7 to 9 The working characteristics and specific embodiments of the present invention are further described.

[0053] like Figure 7 FIG. 1 is a schematic diagram of the working characteristics of the over-temperature protection circuit of the present invention. Figure 7 (A) For the case of using negative temperature coefficient current, Figure 7 (B) corresponds to the case of using positive temperature coefficient current. Figure 7 In (A), Iref is a reference current that does not change with the chip temperature, Ictat (TS) is a negative temperature coefficient current output by the temperature sensing module, and Iotp is a control current output by the over-temperature protection module. When the chip temperature is lower than the temperature threshold Tth_otp, Iref-Ictat is a negative value, and the control current Iotp is zero; when the chip temperature is higher than the temperature threshold Tth_otp, the control current Iotp = (Iref-Ictat)*N, where N represents the amplification factor of the current mirror. Therefore, when the chip temperature is higher than Tth_otp, the over-temperature protection circuit starts to start.

[0054] Similarly, in Figure 7 In (B), when a positive temperature coefficient current is used, Iptat is the positive temperature coefficient current output by the temperature sensing module. When the chip temperature is lower than the temperature threshold Tth_otp, Iptat-Iref is a negative value, and the control current Iotp is zero; when the chip temperature is higher than the temperature threshold Tth_otp, the control current Iotp = (Iptat-Iref)*N. The temperature threshold Tth_otp can be set by adjusting the size of the reference current Iref.

[0055] like Figure 8 As shown in the figure, when the CMOS process is adopted, the temperature sensing module TS, the over-temperature protection module OTP, the PA driver stage PAD and the PA output stage PA are all integrated on the same chip. Since the DC power consumption of the PA output stage PA is much greater than that of the PA driver stage PAD, it is the main heat source of the RF power amplifier chip. Therefore, the temperature sensing module TS is arranged near the PA output stage PA to accurately detect the chip temperature. This single-chip integration solution is particularly suitable for the implementation of CMOS PA.

[0056] like Fig. 9As shown, when the GaAs process is adopted, due to the particularity of the GaAs process, the whole system adopts a dual-chip structure. The core device (HBT device) of the power amplifier is arranged on the GaAs chip (GaAs Die), and the control circuit is arranged on the Si CMOS chip (Si CMOSDie). In this implementation, the temperature detection part of the temperature sensing module is arranged on the GaAs chip, which is used to detect the temperature near the core device of the power amplifier, and transmit the temperature information to the control circuit arranged on the Si CMOS chip through the feedback current Isense. The IB_PAD_OTP and IB_PA_OTP are the bias currents of the PA driving stage and the PA output stage, respectively, which are controlled by the over-temperature protection circuit.

[0057] The dual-chip structure design in this embodiment fully considers the characteristics and limitations of different processes, ensuring the accuracy of temperature detection and realizing reliable control functions. This design is particularly suitable for the temperature protection requirements of high-performance GaAs power amplifiers and has strong engineering practical value.

[0058] Next, continue to combine Figures 10 to 13 Other specific embodiments of the present invention are described.

[0059] like Fig.10 As shown, in the dual-chip implementation using GaAs technology, the temperature sensing circuit adopts the following structure: an HBT device Q1 is set on the GaAs chip as a temperature sensing element, and the remaining elements including MOS tubes M1 to M5 and resistor R1 are all set on the CMOS chip. This design makes full use of the temperature characteristics of the HBT device, while avoiding the difficulty of implementing complex control circuits on GaAswafer. The design of the specific size and bias conditions of the HBT device Q1 belongs to the usual means of those skilled in the art and will not be repeated here.

[0060] like Fig.11 As shown in FIG. 1 , when the PA output stage is composed of multiple power cells Pcell, the temperature sensing HBT device Q1 is set at the center of the multiple power cells Pcell. The advantage of this layout design is that since the power cell Pcell is the main heat source, setting the temperature sensing device Q1 at the center of the power cell can more accurately detect the hot spot temperature of the chip, thereby achieving more accurate temperature protection.

[0061] like Fig.12 As shown in Figure 1, the output characteristics of the temperature sensing circuit include two cases: Fig.12 (A) Characteristic curve showing that the negative temperature coefficient current Ictat decreases as the temperature increases; Fig.12(B) shows the characteristic curve of the positive temperature coefficient current Iptat increasing with the increase of temperature. The selection of these two characteristic curves depends on the specific circuit implementation mode, and both can realize the temperature protection function of the present invention.

[0062] like Fig.13 As shown, in a complete embodiment of the present invention, a temperature sensing module TS and an over-temperature protection module OTP are added on the basis of the traditional RF power amplifier structure. The temperature sensing module TS detects the chip temperature in real time and outputs a corresponding current signal, and the over-temperature protection module OTP adjusts the bias currents IB_PAD and IB_PA of the PA driving stage PAD and the PA output stage PA according to the temperature signal, thereby realizing temperature protection of the power amplifier.

[0063] The description of the above embodiments is only used to help understand the method of the present invention and its core idea. It should be pointed out that for ordinary technicians in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention. For example, the specific implementation of the temperature sensing circuit and the over-temperature protection circuit can have a variety of variations, and the type and number of temperature detection elements can also be adjusted according to actual needs, which will not affect the core technical solution of the present invention.

[0064] The power amplifier temperature protection method and device provided by the present invention have the following beneficial effects:

[0065] 1. By detecting the chip temperature in real time and dynamically adjusting the bias current, the temperature protection of the power amplifier is achieved, and the reliability of the chip is improved;

[0066] 2. The start-up of temperature protection is gradual, which avoids sudden changes in the working state and ensures the stability of the power amplifier;

[0067] 3. The circuit structure is simple, easy to implement, and suitable for different process platforms;

[0068] 4. The intensity of temperature protection is adjustable, with strong flexibility;

[0069] 5. In the dual-chip implementation, through reasonable layout design, the accuracy of temperature detection is guaranteed and reliable control function is realized.

[0070] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A temperature protection method for a power amplifier, characterized in that: include: generating a first current that varies with the temperature of the power amplifier; Generate a reference current that does not vary with the temperature of the power amplifier; The first current is compared with the reference current to obtain a difference, and a control current is generated according to the difference, wherein: When the difference is a negative value, the control current is zero; When the difference is a positive value, the control current is a preset multiple of the difference; The actual bias current of the power amplifier is adjusted by subtracting the control current from the reference bias current of the power amplifier.

2. The method according to claim 1, characterized in that The first current is generated by a temperature sensing module, and the reference current is generated by a reference current source in an over-temperature protection module.

3. The method according to claim 2, characterized in that The first current is a negative temperature coefficient current, and the difference is a difference between the reference current and the first current.

4. The method according to claim 2, characterized in that: The first current is a positive temperature coefficient current, and the difference is a difference between the first current and the reference current.

5. The method according to any one of claims 1 to 4, characterized in that: The control current is generated by a current mirror.

6. A temperature protection device for a power amplifier, characterized in that: include: A temperature sensing module, used for generating a first current that varies with temperature; Over temperature protection module, including: A reference current source, connected to the output end of the temperature sensing module, for generating a reference current that does not change with temperature; A comparison circuit, whose input end is respectively connected to the output end of the temperature sensing module and the reference current source, is used to compare the first current with the reference current to obtain a difference, and generate a control current according to the difference, wherein: When the difference is a negative value, the control current is zero; When the difference is a positive value, the control current is a preset multiple of the difference; The output terminal of the comparison circuit is connected to the bias input terminal of the power amplifier and is used to adjust the actual bias current of the power amplifier by subtracting the control current from the reference bias current of the power amplifier.

7. The device according to claim 6, characterized in that The power amplifier comprises a driving stage and an output stage, and the output end of the comparison circuit is connected to the bias input ends of the driving stage and the output stage respectively. 8 . The apparatus according to claim 6 , wherein the reference bias current comprises a driver stage bias current and an output stage bias current.

9. The device according to claim 6, characterized in that The temperature sensing module is arranged on the GaAs chip and includes an HBT device for temperature sensing. The over-temperature protection module is arranged on the Si CMOS chip. The output end of the temperature sensing module is connected to the over-temperature protection module through the interface between the GaAs chip and the Si CMOS chip.

10. The device according to claim 9, characterized in that The output stage includes a plurality of power cells, and the HBT device is disposed at a central position of the plurality of power cells.

Images