Radio frequency source power stabilizing circuit and method

Abstract

The invention provides a radio frequency source power stabilizing circuit and method, and belongs to the field of radio frequency sources, a current detection unit detects power supply current of a radio frequency source, converts the power supply current into a voltage value and feeds back the voltage value to a voltage conversion unit; the voltage conversion unit adjusts the output voltage according to the received voltage value; and the power amplifier unit adjusts the output power according to the output voltage adjusted by the voltage conversion unit. The output power of the power amplifier unit is in negative correlation with the load impedance, the output power of the power amplifier unit is in positive correlation with the square of the input voltage of the power amplifier unit, and when the load impedance changes, the power supply current is converted into a voltage value through the current detection unit and fed back to the voltage conversion unit; in this way, negative feedback can be established between the output power of the power amplifier unit and the input voltage of the power amplifier unit, the stability of the output power of the power amplifier unit is guaranteed, an impedance detection circuit, an impedance matching circuit and an MCU do not need to be arranged, and the complexity and size of the circuit are reduced.

Description

Technical Field

[0001] This invention relates to the field of radio frequency sources, and more particularly to a power stabilization circuit and method for radio frequency sources. Background Technology

[0002] Radio frequency (RF) sources are commonly used core functional modules in transceivers, radar, and other RF devices. Because the output power of a power amplifier is significantly affected by the load impedance, a typical power amplifier can only achieve a relatively constant output power for a specific impedance range. However, the impedance encountered during operation can vary considerably beyond the amplifier's tolerance range, making it impossible to maintain constant power output across the entire impedance spectrum. A common solution is to incorporate impedance detection and impedance matching circuits. By detecting the impedance matching status and using an MCU to control the parameter adjustments of the impedance matching circuit, the current impedance is adjusted to achieve optimal power output. However, the impedance detection circuit, impedance matching circuit, and MCU significantly increase the complexity and size of the circuitry. Summary of the Invention

[0003] This invention provides a power stabilization circuit and method for radio frequency sources, which solves the problem that impedance detection circuits, impedance matching circuits, and MCUs in the prior art greatly increase the complexity and size of the circuit.

[0004] This invention provides a radio frequency source power stabilization circuit, including a current detection unit, a voltage conversion unit, and a power amplifier unit. The output power of the power amplifier unit is negatively correlated with the load impedance, and the output power of the power amplifier unit is positively correlated with the square of the input voltage of the power amplifier unit. The current detection unit is used to detect the power supply current of the radio frequency source, convert the power supply current into a voltage value and feed it back to the voltage conversion unit; The voltage conversion unit is used to adjust the output voltage according to the received voltage value; The power amplifier unit is used to adjust the output power according to the output voltage adjusted by the voltage conversion unit.

[0005] As one embodiment, the current detection unit includes a sampling resistor R2, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R5, and an operational amplifier. The sampling resistor R2 is connected in series to the power supply line of the RF source. The two ends of the sampling resistor R2 are respectively connected to one end of the resistor R11 and one end of the resistor R12. The other end of the resistor R11 is grounded through the resistor R14. The other end of the resistor R12 is connected to the output pin of the operational amplifier through the resistor R13. The common terminal of the resistor R13 and the output pin of the operational amplifier is connected to one end of the resistor R5. The other end of the resistor R5 is connected to the voltage conversion unit.

[0006] As an example, the resistance value of resistor R11 is the same as that of resistor R12, the resistance value of resistor R13 is the same as that of resistor R14, and the gain of the operational amplifier is negatively correlated with the output power of the power amplifier unit, and is determined based on the ratio of the resistance value of resistor R13 to that of resistor R11.

[0007] As one embodiment, the voltage conversion unit includes a voltage conversion chip and a feedback network. The feedback network includes resistors R3 and R4. The common terminal of resistors R3, R4, and R5 is connected to the FB pin of the voltage conversion chip.

[0008] As an example, the resistance value of resistor R5 is determined based on the feedback capability of the voltage conversion chip's FB pin to voltage fluctuations.

[0009] As an example, the input and output terminals of the voltage conversion unit are respectively provided with filtering capacitors.

[0010] As one embodiment, the power amplifier unit includes an inductor L1, a MOSFET U2, an inductor L2, a capacitor C1, and a capacitor C2. One end of the inductor L1 is connected to the output terminal of the voltage conversion unit, and the other end is connected to the drain of the MOSFET U2, one end of the inductor L2, and one end of the capacitor C2. The other end of the capacitor C2 is grounded, and the other end of the inductor L2 is connected to one end of the capacitor C1. The other end of the capacitor C1 serves as the output terminal of the power amplifier unit.

[0011] As one embodiment, it also includes a radio frequency signal generation unit, which is connected to the power amplifier unit and is used to provide a radio frequency carrier signal to the power amplifier unit.

[0012] As an example, the radio frequency carrier signal is a square wave signal, and the MOS transistor U2 is used to periodically switch under the control of the square wave signal. When the MOS transistor U2 is turned on, the power supply current of the radio frequency source passes through the load. When the MOS transistor U2 is turned off, the output voltage of the voltage conversion unit is applied to the load through the series resonant filter circuit composed of the inductor L2 and the capacitor C1.

[0013] The present invention also provides a method for stabilizing radio frequency source power, implemented based on the aforementioned radio frequency source power stabilization circuit, comprising: The power supply current of the radio frequency source is detected, and the power supply current is converted into a voltage value; Adjust the output voltage according to the received voltage value; Adjust the output power based on the adjusted output voltage.

[0014] The RF source power stabilization circuit and method provided by this invention have a negative correlation between the output power of the power amplifier unit and the load impedance, and a positive correlation between the output power of the power amplifier unit and the square of the input voltage of the power amplifier unit. When the load impedance changes, the supply current is converted into a voltage value by the current detection unit and fed back to the voltage conversion unit, so that a negative feedback is established between the output power of the power amplifier unit and the input voltage of the power amplifier unit, ensuring the stability of the output power of the power amplifier unit. There is no need to set up an impedance detection circuit, impedance matching circuit and MCU, reducing the complexity and size of the circuit. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0016] Figure 1 This is a block diagram of the radio frequency source power stabilization circuit provided by the present invention.

[0017] Figure 2 This is a circuit diagram of the current detection unit provided by the present invention.

[0018] Figure 3 This is a circuit diagram of the voltage conversion unit provided by the present invention.

[0019] Figure 4 This is a circuit diagram of the power amplifier unit provided by the present invention.

[0020] Figure 5 This is a circuit schematic diagram of the radio frequency signal generation unit provided by the present invention.

[0021] Figure 6 This is a circuit diagram of the power supply unit of the radio frequency signal generation unit provided by the present invention.

[0022] Figure 7 This is a graph showing the relationship between output power and load impedance variation provided by the present invention.

[0023] Figure 8 This is a PCB circuit diagram of the present invention and existing RF source power stabilization circuits.

[0024] Figure 9 This is a flowchart illustrating the radio frequency source power stabilization method provided by the present invention.

[0025] In the diagram: 100 - Current detection unit, 200 - Voltage conversion unit, 300 - Power amplifier unit, 400 - Radio frequency signal generation unit. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0027] Figure 1 This is a schematic block diagram of the RF source power stabilization circuit provided by the present invention, as shown below. Figure 1 As shown, the present invention provides a radio frequency source power stabilization circuit, including a current detection unit 100, a voltage conversion unit 200, and a power amplifier unit 300. The current detection unit 100 is connected to the voltage conversion unit 200, and the voltage conversion unit 200 is connected to the power amplifier unit 300. The output power of the power amplifier unit 300 is negatively correlated with the load impedance, and the output power of the power amplifier unit 300 is positively correlated with the square of the input voltage of the power amplifier unit 300.

[0028] The current detection unit 100 is used to detect the power supply current of the radio frequency source, convert the power supply current into a voltage value and feed it back to the voltage conversion unit 200.

[0029] The voltage conversion unit 200 is used to adjust the output voltage according to the received voltage value.

[0030] The power amplifier unit 300 is used to adjust the output power according to the output voltage adjusted by the voltage conversion unit 200.

[0031] The power supply current of the RF source is generated after being powered by a constant voltage power supply. The current detection unit 100 is used to detect the power supply current of the entire RF source circuit and convert the detected current value into voltage and feed it back to the feedback pin of the voltage conversion unit 200.

[0032] The voltage conversion unit 200 converts the input voltage into the desired voltage value. Its feedback pin has negative feedback capability, allowing adjustment of the output voltage based on the voltage divided by the voltage conversion unit 200 and the voltage value converted from the supply current. The voltage divided output voltage is used to maintain a constant output voltage, while the voltage value converted from the supply current is used to ensure that the output voltage of the voltage conversion unit 200 changes with load impedance. Specifically, when the load impedance decreases, the output power increases, the current increases, and the feedback voltage increases, causing the output voltage of the voltage conversion unit 200 to decrease, resulting in a decrease in RF output power. Similarly, when the load impedance increases, the output power decreases, the current decreases, the feedback voltage decreases, and the output voltage of the voltage conversion unit 200 increases, resulting in an increase in RF output power, thus ensuring power stability within a certain range of load impedance.

[0033] The output terminal of the power amplifier unit 300 is connected to the load to establish a loop. In this embodiment of the invention, the losses of the current detection unit 100, the voltage conversion unit 200, and the power amplifier unit 300 are negligible. The current detection unit 100 is located on the power input side of the RF source to sample the power supply current of the RF source. The power supply current will change with the change of the load impedance. The power supply current is converted into a voltage value and fed back to the voltage conversion unit 200. The output voltage of the voltage conversion unit 200, which is the input voltage of the power amplifier unit 300, changes in the same direction as the change of the power supply current. This is equivalent to establishing a negative feedback between the output power of the power amplifier unit 300 and the input voltage of the power amplifier unit 300, ensuring the stability of the output power of the power amplifier unit 300.

[0034] It is understood that the output power of the power amplifier unit 300 is negatively correlated with the load impedance, and positively correlated with the square of the input voltage of the power amplifier unit 300. When the load impedance changes, the current detection unit 100 converts the supply current into a voltage value and feeds it back to the voltage conversion unit 200. This establishes negative feedback between the output power of the power amplifier unit 300 and the input voltage of the power amplifier unit 300, ensuring the stability of the output power of the power amplifier unit 300. There is no need to set up an impedance detection circuit, impedance matching circuit and MCU, which reduces the complexity and size of the circuit.

[0035] like Figure 2 As shown, based on the above embodiment, as an optional embodiment, the current detection unit 100 includes a sampling resistor R2, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R5, and an operational amplifier. The sampling resistor R2 is connected in series to the power supply line of the radio frequency source. The two ends of the sampling resistor R2 are respectively connected to one end of the resistor R11 and one end of the resistor R12. The other end of the resistor R11 is grounded through the resistor R14. The other end of the resistor R12 is connected to the output pin of the operational amplifier through the resistor R13. The common terminal of the resistor R13 and the output pin of the operational amplifier is connected to one end of the resistor R5. The other end of the resistor R5 is connected to the voltage conversion unit 200.

[0036] The sampling resistor R2 is connected in series in the power supply line of the RF source. The current flowing through the sampling resistor can be used as the operating current of the entire RF source. The voltage across the sampling resistor R2 is... , The voltage is transmitted to the positive and negative input terminals of the operational amplifier via resistors R11 and R12 respectively. The output voltage of the operational amplifier is fed back to the voltage conversion unit 200 via resistor R5, realizing the process of converting the supply current into voltage. The gain of the operational amplifier is determined based on resistors R11, R12, R13, and R14.

[0037] Optionally, this invention does not limit the type of operational amplifier; any operational amplifier whose gain control accuracy and withstand voltage meet the final requirements is acceptable. In this embodiment, an LM358 is used as the operational amplifier to control the gain of the current detection unit 100 in converting the current into voltage.

[0038] It is understood that the present invention provides a circuit configuration scheme for the current detection unit 100. The supply current can be collected through the sampling resistor R2, and the voltage across the sampling resistor R2 is transmitted to the operational amplifier through resistors R11 and R12. The operational amplifier converts the supply current into voltage according to the set gain to establish negative feedback. In addition, the circuit structure of the current detection unit 100 is simple, reducing the complexity and size of the circuit.

[0039] Based on the above embodiments, as an optional embodiment, the resistance value of resistor R11 is the same as that of resistor R12, the resistance value of resistor R13 is the same as that of resistor R14, and the gain of the operational amplifier is negatively correlated with the output power of the power amplifier unit 300, and is determined based on the ratio of the resistance value of resistor R13 to that of resistor R11.

[0040] The smaller the value of sampling resistor R2, the smaller the voltage drop it generates, and the smaller its impact on the overall efficiency of the RF source. The resistance values ​​of resistor R11 and R12 are the same, and the resistance values ​​of resistor R13 and R14 are the same. The expression for the output voltage of the operational amplifier is as follows: (1) Where G represents the gain and I represents the power supply circuit. Pout is the supply voltage of the constant voltage power supply, and Pout is the output power of the power amplifier unit 300. For convenience, it is calculated as 100% efficiency.

[0041] Combining equation (1), the output voltage of the operational amplifier can be expressed as: The gain of the operational amplifier can be changed by adjusting the values ​​of R13 / R11.

[0042] It is understood that the present invention makes the resistance value of resistor R11 the same as that of resistor R12, and the resistance value of resistor R13 the same as that of resistor R14. The gain of the operational amplifier can be determined simply by adjusting the ratio of the resistance value of resistor R13 to that of resistor R11, which reduces the complexity of gain adjustment and simplifies the overall design of the RF source.

[0043] Based on the above embodiments, as an optional embodiment, such as Figure 3 As shown, the voltage conversion unit 200 includes a voltage conversion chip and a feedback network. The feedback network includes resistors R3 and R4. The common terminal of resistors R3, R4 and R5 is connected to the FB pin of the voltage conversion chip.

[0044] Optionally, a step-down DC-DC converter chip, such as the LMR54410, can be used to avoid excessive output voltage and circuit damage when the downstream load is open. DC-DC converter chips have a characteristic that they adjust the output voltage until the voltage at the FB pin equals a predetermined value (this predetermined value is determined by the characteristics of the DC-DC converter chip; for the LMR54410, this value is 0.8V). Due to this characteristic, when the output power of the power amplifier unit 300 increases due to changes in the external load, the feedback voltage transmitted by the current detection unit 100 increases. Upon detecting this increase, the FB pin of the DC-DC converter chip reduces the voltage supplied to the power amplifier unit 300. Similarly, when the output power of the power amplifier unit 300 decreases, the DC-DC converter chip increases the voltage supplied to the power amplifier unit 300.

[0045] For the feedback network formed by resistors R3, R4, and R5, with the FB pin as a node, the following expression can be obtained based on Kirchhoff's current equations: (2) in, The voltage value is obtained by converting the supply current. This refers to the voltage value at the FB pin. This is the output voltage of the voltage conversion unit 200.

[0046] The expression for the output voltage of the voltage conversion unit 200 is as follows: (3) Where k is the output efficiency coefficient of the Class E power amplifier, R L This is the load impedance of the power amplifier.

[0047] Substituting equations (1) and (3) into equation (2), we obtain the following expression: (4) Rearranging equation (4), we obtain the following expression: (5) The value of resistor R5 determines the depth of feedback. According to equation (5), the smaller the value of resistor R5, the deeper the feedback and the higher the power stability. L The smaller the impact of the change on the whole equation, the smaller the change in power output caused by the load change.

[0048] Under the limiting condition, when R5≈0, equation (5) can be simplified to the following equation: (6) From equation (6), we can derive: (7) As can be seen from equation (7), the output power of the power amplifier unit 300 is negatively correlated with its gain.

[0049] It is understood that the present invention utilizes a feedback network composed of resistors R3 and R4 and a voltage conversion chip to form a voltage conversion unit 200, thereby reducing the complexity of the circuit. Resistors R3 and R4 divide the output voltage of the voltage conversion unit 200 and feed it back to the FB pin. When the feedback of resistor R5 is not working, it provides negative feedback to the voltage conversion chip to maintain the relative stability of the output voltage of the voltage conversion unit 200.

[0050] Based on the above embodiments, as an optional embodiment, the resistance value of resistor R5 is determined based on the feedback capability of the voltage conversion chip's FB pin to voltage fluctuations.

[0051] Understandably, the value of resistor R5 determines the feedback depth. The smaller the value of resistor R5, the deeper the feedback and the higher the power stability. However, excessive feedback will reduce the feedback capability of the voltage conversion chip's feedback pin to voltage fluctuations. Therefore, the feedback depth should be selected according to actual needs. That is, the value of resistor R5 should be determined based on the feedback capability of the voltage conversion chip's FB pin to voltage fluctuations, thus determining the feedback depth and ensuring the voltage conversion chip's feedback capability to voltage fluctuations is not reduced.

[0052] Based on the above embodiments, as an optional embodiment, the input and output terminals of the voltage conversion unit 200 are respectively provided with filtering capacitors.

[0053] The filtering capacitors at the input of the voltage conversion unit 200 include capacitors C99, C35, and C36. Each of capacitors C99, C35, and C36 has a different capacitance value and is used to filter out different noise and interference signals on the power supply voltage. The number and capacitance value are selected according to actual needs.

[0054] The filtering capacitors at the output of the voltage conversion unit 200 include capacitors C39, C40, and C41. Each of capacitors C39, C40, and C41 has a different capacitance value and is used to filter out different noise and interference signals on the power supply voltage. The number and capacitance value are selected according to actual needs.

[0055] It is understood that the present invention sets filter capacitors at the input and output terminals of the voltage conversion unit 200 to filter out different noise and interference signals on the power supply voltage, thereby improving the performance of the radio frequency source circuit.

[0056] like Figure 4 As shown, based on the above embodiment, as an optional embodiment, the power amplifier unit 300 includes an inductor L1, a MOSFET U2, an inductor L2, a capacitor C1, and a capacitor C2. One end of the inductor L1 is connected to the output terminal of the voltage conversion unit 200, and the other end is connected to the drain of the MOSFET U2, one end of the inductor L2, and one end of the capacitor C2, respectively. The other end of the capacitor C2 is grounded, and the other end of the inductor L2 is connected to one end of the capacitor C1. The other end of the capacitor C1 serves as the output terminal of the power amplifier unit 300.

[0057] The inductor L1 acts as an RF choke, allowing DC current to pass through while blocking RF current. Inductor L2 and capacitor C1 form a series resonant filter circuit, ideally resonating at the fundamental frequency of the signal, ensuring that only signals of the desired frequency band pass through. MOSFET U2 is a switching power MOSFET that periodically switches under the control of the RF carrier signal to achieve efficient energy conversion.

[0058] Optionally, capacitors C4, C5, and C6 are also connected to the common terminal of inductor L1 and the output terminal of voltage conversion unit 200 to filter out noise and interference signals of the output voltage of voltage conversion unit 200. The number and capacitance values ​​are selected according to actual needs.

[0059] It is understood that the present invention utilizes inductor L1, MOSFET U2, capacitor C1 and capacitor C2 to construct a power amplifier unit 300. The circuit structure is simple. Inductor L2 and capacitor C1 form a series resonant filter circuit, which resonates at the fundamental frequency of the signal under ideal conditions, ensuring that only signals of the required frequency band pass through. MOSFET U2 is a switching power MOSFET, which periodically switches under the control of the radio frequency carrier signal to achieve efficient energy conversion and improve the power amplifier efficiency.

[0060] like Figure 5 As shown, based on the above embodiments, as an optional embodiment, the radio frequency source power stabilization circuit provided by the present invention further includes a radio frequency signal generation unit 400, which is connected to the power amplifier unit 300 and is used to provide a radio frequency carrier signal to the power amplifier unit 300.

[0061] Optionally, the radio frequency signal generation unit 400 can be constructed using circuits such as a PLL phase-locked loop, a DDS chip, and an active crystal oscillator. It is preferred to use an active crystal oscillator to reduce circuit complexity.

[0062] like Figure 6 As shown, the power supply unit is used to provide the required 5V voltage to the RF signal generation unit 400. It can be implemented using DC-DC, LDO, or other methods, and can be designed according to the characteristics of the required power supply.

[0063] Optionally, the radio frequency carrier signal is a square wave signal, and the MOS transistor U2 is used to periodically switch under the control of the square wave signal. When the MOS transistor U2 is turned on, the power supply current of the radio frequency source passes through the load. When the MOS transistor U2 is turned off, the output voltage of the voltage conversion unit 200 is applied to the load through the series resonant filter circuit composed of the inductor L2 and the capacitor C1.

[0064] MOSFET U2 achieves efficient energy conversion through periodic switching under the control of an input signal, i.e., a square wave signal. When the input voltage is greater than the threshold voltage, MOSFET U2 is turned on, equivalent to a closed switch, at which point the transistor has voltage but no current. When the input voltage is less than the threshold voltage, MOSFET U2 is turned off, equivalent to an open switch, at which point no current flows. Therefore, voltage and current do not occur simultaneously on MOSFET U2. When MOSFET U2 is turned on, the voltage across the transistor is zero, and current flows through the load; when MOSFET U2 is turned off, voltage is applied to the load through a resonant circuit, at which point the current is zero, eliminating the losses caused by charging and discharging, thus achieving a theoretical efficiency of 100%.

[0065] It is understandable that MOSFET U2 is a switching power MOSFET that periodically switches under the control of a square wave signal to achieve efficient energy conversion. Voltage and current do not occur simultaneously on MOSFET U2. When MOSFET U2 is turned off, voltage is applied to the load through the resonant circuit. At this time, the current is zero, which eliminates the losses caused by charging and discharging and improves the efficiency of the power amplifier.

[0066] The present invention will now be described with reference to an embodiment.

[0067] Suppose we are designing an RF power source with a load impedance range of 5.5~11 ohms and an expected power of 24W±3W. If we simply use a Class E amplifier, the output power would be 24W with a load center value of around 8 ohms. However, the output power would be 35W and 17.5W with loads of 5.5 ohms and 11 ohms, respectively, far exceeding the expected power variation. The RF power stabilization circuit provided in this invention can overcome the shortcomings of simply using a Class E amplifier.

[0068] The circuit parameters of the present invention are set as follows: V IN The voltage is 28V, the resistance of R2 is 0.05 ohms, the resistance of R5 is 100kΩ, the resistance of R4 is 100kΩ, the resistance of R3 is 2900kΩ, the resistance of the load R1 is 5.5~11 ohms, and the expected power is 24W.

[0069] The gain of the operational amplifier in the current detection unit was adjusted so that when the load was 8 ohms, the output voltage of the operational amplifier was the same as the FB reference voltage, which was 0.8V. (It should be noted that this parameter setting is only for illustrating the effect of the specific needs of this case, and does not mean that this invention is only applicable to this parameter). Actual measurements showed that when the load was 8 ohms, the constant voltage power supply current was approximately 1A, the output voltage of the operational amplifier was approximately 0.8V, VCC was 24V, the output power was approximately 24W, and the efficiency was approximately 86%.

[0070] The present invention will now be quantitatively analyzed in conjunction with the above parameters.

[0071] With an 8-ohm center impedance (center impedance of 5.5~11 ohms) R0, analyze the output power of the power amplifier unit when the total load impedance changes to kR0.

[0072] The amplifier output power is proportional to the square of (Vcc - Vsat) and inversely proportional to the load impedance kR0, from which we can obtain: (8) Where Vsat is the saturation voltage drop of the MOS transistor; C1 / k1 is the output efficiency coefficient of the Class E power amplifier, which is the reciprocal of k in equation (3).

[0073] Let the output voltage of the operational amplifier be V. The output voltage V of the operational amplifier is proportional to the voltage across the sampling resistor R2, further proportional to the current through the sampling resistor R2, and even further proportional to the power consumption. Under the condition that the efficiency is basically constant, it is proportional to the output power P.

[0074] The following equation is derived from equation (8): (9) Based on equations (8) and (9), the following equation can be obtained: (10) When the load is 8 ohms, k1=1, V=0.8, Vsat=0.3V. Substituting these values ​​into equation (10) yields: (11) Dividing equation (10) and equation (11) yields: (12) At the intersection of resistors R3, R4, and R5, a system of equations can be established using Kirchhoff's current law, yielding the following: (13) because Equation (13) can be transformed into: (14) Combining equations (12) and (14), and eliminating V, we can obtain the quadratic equation constraint between the voltage Vcc and the load kR0: (15) From equation (15), we obtain the relationship between Vcc and impedance. Substituting this back into equation (10), we can obtain the relationship between output power and load impedance. Figure 7 . Figure 7 The horizontal axis represents the change in load impedance, P2 represents the change in output power with impedance without any processing, and P1 represents the change in output power with load impedance after adding the negative feedback provided by this invention. Figure 7 It can be seen that, for the maximum and minimum impedance within the load impedance range of 5.5~11 ohms, when the load is 5.5 ohms, the Vcc voltage becomes approximately 21V, and the power output is approximately 27W; when the load is 11 ohms, the Vcc voltage becomes approximately 26.5V, and the power output is approximately 21.4W. It can be seen that this invention can effectively maintain a constant output power. Within the range of 5.5 ohms to 11 ohms, the power variation has changed from the previous 17.5W~35W to the current 21.4W~27W, reducing the power variation range from 17.5W to 5.6W.

[0075] like Figure 8 As shown in the figure, the PCB circuit board at the top is the PCB circuit board of the RF source power stabilization circuit provided by this invention, and the PCB circuit board at the bottom is the existing RF source power stabilization circuit using an impedance detection circuit. Measurements on the PCB boards show that the components of both occupy 20 ppm of the printed circuit board area. and 377 Therefore, it can be seen that the complexity of this invention is far lower than that of impedance detection schemes, which can bring significant cost and size advantages, making it easy to achieve low cost and miniaturization.

[0076] In summary, this invention enables a stable power RF source for varying impedances at low cost and with miniaturization.

[0077] The radio frequency source power stabilization method provided by the present invention is described below. The radio frequency source power stabilization method described below can be referred to in correspondence with the radio frequency source power stabilization circuit described above.

[0078] like Figure 9 As shown, the present invention also provides a method for stabilizing radio frequency source power, which is implemented based on the radio frequency source power stabilization circuit, and includes the following steps.

[0079] Step S100: Detect the power supply current of the radio frequency source and convert the power supply current into a voltage value.

[0080] Step S200: Adjust the output voltage according to the received voltage value.

[0081] Step S300: Adjust the output power according to the adjusted output voltage.

[0082] As one embodiment, the RF source power stabilization circuit includes a current detection unit, a voltage conversion unit, and a power amplifier unit. The output power of the power amplifier unit is negatively correlated with the load impedance, and the output power of the power amplifier unit is positively correlated with the square of the input voltage of the power amplifier unit. The current detection unit is used to detect the power supply current of the radio frequency source, convert the power supply current into a voltage value and feed it back to the voltage conversion unit; The voltage conversion unit is used to adjust the output voltage according to the received voltage value; The power amplifier unit is used to adjust the output power according to the output voltage adjusted by the voltage conversion unit.

[0083] As one embodiment, the current detection unit includes a sampling resistor R2, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R5, and an operational amplifier. The sampling resistor R2 is connected in series to the power supply line of the RF source. The two ends of the sampling resistor R2 are respectively connected to one end of the resistor R11 and one end of the resistor R12. The other end of the resistor R11 is grounded through the resistor R14. The other end of the resistor R12 is connected to the output pin of the operational amplifier through the resistor R13. The common terminal of the resistor R13 and the output pin of the operational amplifier is connected to one end of the resistor R5. The other end of the resistor R5 is connected to the voltage conversion unit.

[0084] As an example, the resistance value of resistor R11 is the same as that of resistor R12, the resistance value of resistor R13 is the same as that of resistor R14, and the gain of the operational amplifier is negatively correlated with the output power of the power amplifier unit, and is determined based on the ratio of the resistance value of resistor R13 to that of resistor R11.

[0085] As one embodiment, the voltage conversion unit includes a voltage conversion chip and a feedback network. The feedback network includes resistors R3 and R4. The common terminal of resistors R3, R4, and R5 is connected to the FB pin of the voltage conversion chip.

[0086] As an example, the resistance value of resistor R5 is determined based on the feedback capability of the voltage conversion chip's FB pin to voltage fluctuations.

[0087] As an example, the input and output terminals of the voltage conversion unit are respectively provided with filtering capacitors.

[0088] As one embodiment, the power amplifier unit includes an inductor L1, a MOSFET U2, an inductor L2, a capacitor C1, and a capacitor C2. One end of the inductor L1 is connected to the output terminal of the voltage conversion unit, and the other end is connected to the drain of the MOSFET U2, one end of the inductor L2, and one end of the capacitor C2. The other end of the capacitor C2 is grounded, and the other end of the inductor L2 is connected to one end of the capacitor C1. The other end of the capacitor C1 serves as the output terminal of the power amplifier unit.

[0089] As one embodiment, it also includes a radio frequency signal generation unit, which is connected to the power amplifier unit and is used to provide a radio frequency carrier signal to the power amplifier unit.

[0090] As an example, the radio frequency carrier signal is a square wave signal, and the MOS transistor U2 is used to periodically switch under the control of the square wave signal. When the MOS transistor U2 is turned on, the power supply current of the radio frequency source passes through the load. When the MOS transistor U2 is turned off, the output voltage of the voltage conversion unit is applied to the load through the series resonant filter circuit composed of the inductor L2 and the capacitor C1.

[0091] The radio frequency source power stabilization method provided by this invention is based on a radio frequency source power stabilization circuit and has the same technical effect as the radio frequency source power stabilization circuit, which will not be described in detail here.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A radio frequency source power stabilization circuit, characterized in that, It includes a current detection unit, a voltage conversion unit, and a power amplifier unit. The output power of the power amplifier unit is negatively correlated with the load impedance, and positively correlated with the square of the input voltage of the power amplifier unit. The current detection unit is used to detect the power supply current of the radio frequency source, convert the power supply current into a voltage value and feed it back to the voltage conversion unit; The voltage conversion unit is used to adjust the output voltage according to the received voltage value; The power amplifier unit is used to adjust the output power according to the output voltage adjusted by the voltage conversion unit.

2. The RF source power stabilization circuit according to claim 1, characterized in that, The current detection unit includes a sampling resistor R2, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R5, and an operational amplifier. The sampling resistor R2 is connected in series to the power supply line of the RF source. The two ends of the sampling resistor R2 are respectively connected to one end of the resistor R11 and one end of the resistor R12. The other end of the resistor R11 is grounded through the resistor R14. The other end of the resistor R12 is connected to the output pin of the operational amplifier through the resistor R13. The common terminal of the resistor R13 and the output pin of the operational amplifier is connected to one end of the resistor R5. The other end of the resistor R5 is connected to the voltage conversion unit.

3. The RF source power stabilization circuit according to claim 2, characterized in that, The resistance value of resistor R11 is the same as that of resistor R12, and the resistance value of resistor R13 is the same as that of resistor R14. The gain of the operational amplifier is negatively correlated with the output power of the power amplifier unit and is determined based on the ratio of the resistance value of resistor R13 to that of resistor R11.

4. The RF source power stabilization circuit according to claim 2, characterized in that, The voltage conversion unit includes a voltage conversion chip and a feedback network. The feedback network includes resistors R3 and R4. The common terminal of resistors R3, R4, and R5 is connected to the FB pin of the voltage conversion chip.

5. The RF source power stabilization circuit according to claim 2 or 4, characterized in that, The resistance value of resistor R5 is determined based on the feedback capability of the voltage conversion chip's FB pin to voltage fluctuations.

6. The RF source power stabilization circuit according to claim 5, characterized in that, The voltage conversion unit is equipped with filter capacitors at both its input and output terminals.

7. The RF source power stabilization circuit according to claim 1, characterized in that, The power amplifier unit includes an inductor L1, a MOSFET U2, an inductor L2, a capacitor C1, and a capacitor C2. One end of the inductor L1 is connected to the output terminal of the voltage conversion unit, and the other end is connected to the drain of the MOSFET U2, one end of the inductor L2, and one end of the capacitor C2. The other end of the capacitor C2 is grounded, and the other end of the inductor L2 is connected to one end of the capacitor C1. The other end of the capacitor C1 serves as the output terminal of the power amplifier unit.

8. The RF source power stabilization circuit according to claim 7, characterized in that, It also includes a radio frequency signal generation unit, which is connected to the power amplifier unit and is used to provide a radio frequency carrier signal to the power amplifier unit.

9. The RF source power stabilization circuit according to claim 8, characterized in that, The radio frequency carrier signal is a square wave signal. The MOS transistor U2 is used to switch periodically under the control of the square wave signal. When the MOS transistor U2 is turned on, the power supply current of the radio frequency source passes through the load. When the MOS transistor U2 is turned off, the output voltage of the voltage conversion unit is applied to the load through the series resonant filter circuit composed of the inductor L2 and the capacitor C1.

10. A method for stabilizing the power of a radio frequency source, characterized in that, Based on the RF source power stabilization circuit according to any one of claims 1-9, the method includes: The power supply current of the radio frequency source is detected, and the power supply current is converted into a voltage value; Adjust the output voltage according to the received voltage value; Adjust the output power based on the adjusted output voltage.

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