Power factor extraction circuit

Abstract

The utility model relates to the technical field of power factor analysis, in particular to a power factor extraction circuit, which is characterized in that a signal of a current phase shift waveform is multiplied by a signal of a voltage waveform to obtain a mixed waveform signal, and a phase difference signal in the mixed waveform signal is extracted through a low-pass filter; the phase difference signal generates a signal for controlling the phase shift of the voltage-controlled phase shifter through a proportional integral circuit, and finally, the phase difference between the signal of the current phase shift waveform and the signal of the voltage waveform indicates that the signal of the voltage-controlled phase shifter has a clear one-to-one correspondence relationship with the power factor, so that the extraction of the power factor signal is completed. Compared with a power factor calculation mode in the prior art, signal extraction operation can be completed without a program of a processor, hardware resource consumption is low, the requirement for calculation resources is low, all devices are common and do not need programming, and maintainability is good.

Description

Technical Field

[0001] The utility model relates to the technical field of power factor analysis, in particular to a power factor extraction circuit. Background Art

[0002] Power factor refers to the ratio of active power to apparent power in an AC circuit. The higher this value, the better the efficiency of user electrical equipment at a given voltage and power, and the more fully utilized the capacity of power transmission, distribution, and power generation equipment.

[0003] Existing methods for determining power factor involve either ferromagnetic electrodynamic detection or processor-based signal analysis. While the former, while suitable for indicating instruments, offers high reliability, the latter provides unintuitive readings and exhibits poor accuracy and sensitivity. The latter requires a powerful processor and sophisticated algorithms, requiring significant hardware investment and making maintenance difficult.

[0004] Based on this, it is necessary to develop a power factor extraction circuit. Utility Model Content

[0005] The embodiment of the utility model provides a power factor extraction circuit, which is used to solve the problem that power factor extraction in the prior art requires a lot of hardware resources.

[0006] In a first aspect, an embodiment of the present invention provides a power factor extraction circuit, comprising: a multiplication circuit, a low-pass filter, a proportional-integral circuit, and a voltage-controlled phase shifter;

[0007] The output end of the multiplication circuit is electrically connected to the input end of the low-pass filter, the output end of the low-pass filter is electrically connected to the input end of the proportional-integral circuit, the output end of the proportional-integral circuit is electrically connected to the control end of the voltage-controlled phase shifter, and the output end of the voltage-controlled phase shifter is electrically connected to the phase-shift input end of the multiplication circuit;

[0008] When a current waveform and a voltage waveform are respectively input to the input end of the voltage-controlled phase shifter and the voltage waveform input end of the multiplication circuit, the voltage-controlled phase shifter generates a phase-shifted waveform according to the output of the proportional-integral circuit, the multiplication circuit multiplies the phase-shifted waveform and the voltage waveform to generate a mixed waveform, the low-pass filter filters the mixed waveform to generate a smooth waveform, and the proportional-integral circuit performs a calculation based on the smooth waveform to generate a power factor indication signal.

[0009] In some possible implementations, the multiplication circuit includes: an addition circuit, a first logarithmic circuit, a second logarithmic circuit, and an exponential circuit;

[0010] The output end of the first logarithm circuit and the output end of the second logarithm circuit are electrically connected to the first input end of the adding circuit and the second input end of the adding circuit respectively, and the output end of the adding circuit is electrically connected to the input end of the exponential circuit;

[0011] An input end of the second logarithmic circuit is electrically connected to an output end of the voltage-controlled phase shifter, and an output end of the exponential circuit is electrically connected to the low-pass filter.

[0012] In some possible implementations, the first logarithmic circuit and the second logarithmic circuit respectively include: a first operational amplifier, a first resistor, a second resistor, and a first transistor;

[0013] The inverting input terminal of the first operational amplifier is electrically connected to the second end of the first resistor and the collector of the first transistor respectively, the positive input terminal of the first operational amplifier is electrically connected to the first end of the second resistor, and the second end of the second resistor and the base of the first transistor are grounded;

[0014] The output end of the first operational amplifier is electrically connected to the emitter of the first transistor and the first input end of the adding circuit or to the emitter of the first transistor and the second input end of the adding circuit.

[0015] In some possible implementations, the adding circuit includes: a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, and a third operational amplifier;

[0016] The second end of the third resistor, the second end of the fourth resistor, and the first end of the fifth resistor are electrically connected to the inverting input terminal of the third operational amplifier, and both ends of the sixth resistor are electrically connected to the positive input terminal of the third operational amplifier and the ground respectively;

[0017] The output terminal of the third operational amplifier is electrically connected to the second end of the sixth resistor and the input terminal of the exponential circuit.

[0018] In some possible implementations, the exponential circuit includes: a second transistor, a seventh resistor, an eighth resistor, and a fourth operational amplifier;

[0019] The emitter of the second transistor, the first end of the seventh resistor and the inverting input end of the fourth operational amplifier are electrically connected;

[0020] Two ends of the eighth resistor are electrically connected to the positive input terminal of the fourth operational amplifier and the ground;

[0021] The output end of the fourth operational amplifier is electrically connected to the second end of the seventh resistor and the input end of the low-pass filter;

[0022] The collector of the second transistor and the base of the second transistor are electrically connected to the output end of the adding circuit.

[0023] In some possible implementations, the low-pass filter includes: a pre-resistor and a bypass capacitor, the second end of the pre-resistor is electrically connected to the first end of the bypass capacitor and the input end of the proportional integral circuit, the second end of the bypass capacitor is grounded, and the first end of the pre-resistor is electrically connected to the output end of the multiplication circuit.

[0024] In some possible implementations, the proportional-integral circuit includes: a fifth operational amplifier, a twelfth resistor, a thirteenth resistor, and a third capacitor;

[0025] The inverting input terminal of the fifth operational amplifier is electrically connected to the second end of the twelfth resistor and the first end of the third capacitor, and the positive input terminal of the fifth operational amplifier is grounded;

[0026] The second end of the third capacitor is electrically connected to the first end of the thirteenth resistor, and the second end of the thirteenth resistor is electrically connected to the output end of the fifth operational amplifier and the control end of the voltage-controlled phase shifter.

[0027] In some possible implementations, the voltage-controlled phase shifter includes: a sixth operational amplifier, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, and a varactor diode;

[0028] The second end of the fourteenth resistor and the first end of the fifteenth resistor are electrically connected to the inverting input terminal of the sixth operational amplifier, the first end of the fourteenth resistor is grounded, and the second end of the fifteenth resistor is electrically connected to the output terminal of the sixth operational amplifier;

[0029] The second end of the sixteenth resistor and the cathode of the varactor diode are electrically connected to the positive input terminal of the sixth operational amplifier;

[0030] The anode of the varactor diode is electrically connected to the output end of the proportional-integral circuit, and the output end of the sixth operational amplifier is electrically connected to the phase-shift input end of the multiplication circuit.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The present invention discloses a power factor extraction circuit, which multiplies the current phase-shift waveform signal and the voltage waveform signal to obtain a mixed waveform signal, extracts the phase difference signal from the mixed waveform signal through a low-pass filter, and generates a signal for controlling the phase shift of a voltage-controlled phase shifter through a proportional-integral circuit, ultimately making the phase difference between the current phase-shift waveform signal and the voltage waveform signal be The signal indicating the phase shift of the voltage-controlled phase shifter has a clear one-to-one correspondence with the power factor, thereby extracting the power factor signal. Compared with existing power factor calculation methods, this signal extraction operation can be completed without a processor program, consuming less hardware resources and requiring less computing resources. Furthermore, all components are common and do not require programming, making them easily available and maintainable. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or descriptions of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0034] Figure 1 This is a functional block diagram of a power factor extraction circuit provided by an embodiment of the present utility model;

[0035] Figure 2 This is a functional block diagram of a multiplication circuit provided by an embodiment of the present utility model;

[0036] Figure 3 This is a schematic diagram of a low-pass filter provided by an embodiment of the present utility model;

[0037] Figure 4 This is a schematic diagram of a proportional-integral circuit provided by an embodiment of the present utility model;

[0038] Figure 5 This is a principle diagram of a voltage-controlled phase shifter provided in an embodiment of the present utility model. DETAILED DESCRIPTION

[0039] In the following description, specific details such as particular system structures and techniques are provided for purposes of illustration, not limitation, to facilitate a thorough understanding of the embodiments of the present invention. However, it will be apparent to those skilled in the art that the present invention may be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, and methods are omitted to avoid obscuring the description of the present invention with unnecessary detail.

[0040] In order to make the purpose, technical solutions and advantages of the present invention clearer, the following will be described through specific implementation methods in conjunction with the accompanying drawings.

[0041] The following is a detailed description of an embodiment of the present invention. This example is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process. However, the protection scope of the present invention is not limited to the following embodiment.

[0042] Figure 1 This is an overall structural diagram of the power factor extraction circuit provided by the embodiment of the utility model.

[0043] like Figure 1 As shown, it shows the overall structure of the power factor extraction circuit provided by the embodiment of the utility model, which is described in detail as follows:

[0044] A power factor extraction circuit includes: a multiplication circuit, a low-pass filter, a proportional-integral circuit, and a voltage-controlled phase shifter;

[0045] The output end of the multiplication circuit is electrically connected to the input end of the low-pass filter, the output end of the low-pass filter is electrically connected to the input end of the proportional-integral circuit, the output end of the proportional-integral circuit is electrically connected to the control end of the voltage-controlled phase shifter, and the output end of the voltage-controlled phase shifter is electrically connected to the phase-shift input end of the multiplication circuit;

[0046] When a current waveform and a voltage waveform are respectively input to the input end of the voltage-controlled phase shifter and the voltage waveform input end of the multiplication circuit, the voltage-controlled phase shifter generates a phase-shifted waveform according to the output of the proportional-integral circuit, the multiplication circuit multiplies the phase-shifted waveform and the voltage waveform to generate a mixed waveform, the low-pass filter filters the mixed waveform to generate a smooth waveform, and the proportional-integral circuit performs a calculation based on the smooth waveform to generate a power factor indication signal.

[0047] For example, the present invention comprises a multiplication circuit, a low-pass filter, a proportional-integrator circuit, and a voltage-controlled phase shifter. These four components form a loop structure, thereby extracting a signal positively correlated with the power factor. The multiplication circuit receives a voltage waveform signal on one hand, and a phase-shifted waveform signal from the voltage-controlled phase shifter on the other. Since the phase-shifted waveform signal is derived from the current waveform, the frequency of the current waveform is the same as the frequency of the voltage waveform, as seen from the main components of the current waveform. The mixed waveform after multiplying the two conforms to the following formula (product-sum-difference):

[0048]

[0049] Where VoltageWave is the amplitude of the voltage waveform, PhaseShiftWave is the amplitude of the current phase-shift waveform, ω0 is the fundamental frequency of the voltage waveform, and φ is the phase difference between the current phase-shift waveform and the voltage waveform.

[0050] From the above formula we can see that the mixed waveform includes a 2-fold frequency waveform and a DC component: Among them, the amplitude of the subsequent DC component is proportional to the cosine value cosφ of the phase difference. When this phase difference is When the DC component amplitude is zero, therefore, in the embodiment of the present invention, the mixed waveform is filtered to remove the AC component, and the remaining DC component amplitude is input into the proportional integral circuit to generate a control signal. This control signal controls the voltage-controlled phase shifter, and the voltage-controlled phase shifter shifts the phase of the current waveform according to the control signal.

[0051] According to the relevant technology of automatic control principle, as long as the parameters of the proportional integral circuit are set reasonably, the proportional integral circuit will eventually make the above DC component 0. At this time, a stable signal will be output at the output end of the proportional integral circuit. This signal is a signal indicating the voltage-controlled phase shifter and is positively correlated with the phase shift angle (the sum of the phase shift angle and the power factor angle is ), the power factor can be calculated from this signal. In some applications, this signal is fed into the processor's analog-to-digital converter, converted to a digital value, and then used to obtain the power factor value through a table lookup. In other words, the signal output by the proportional-integral circuit is the signal indicating the power factor.

[0052] In the embodiment of the utility model, the signal of the current phase-shifted waveform is multiplied by the signal of the voltage waveform to obtain a mixed waveform signal, and the phase difference signal in the mixed waveform signal is extracted by a low-pass filter. This phase difference signal is used to generate a signal for controlling the phase shift of the voltage-controlled phase shifter through a proportional-integral circuit, and finally the phase difference between the signal of the current phase-shifted waveform and the voltage waveform signal is The signal indicating the phase shift of the voltage-controlled phase shifter has a clear one-to-one correspondence with the power factor, thereby extracting the power factor signal. Compared with existing power factor calculation methods, this signal extraction operation can be completed without a processor program, consuming less hardware resources and requiring less computing resources. Furthermore, all components are common and do not require programming, improving maintainability.

[0053] In some possible implementations, the multiplication circuit includes: an addition circuit, a first logarithmic circuit, a second logarithmic circuit, and an exponential circuit;

[0054] The output end of the first logarithm circuit and the output end of the second logarithm circuit are electrically connected to the first input end of the adding circuit and the second input end of the adding circuit respectively, and the output end of the adding circuit is electrically connected to the input end of the exponential circuit;

[0055] An input end of the second logarithmic circuit is electrically connected to an output end of the voltage-controlled phase shifter, and an output end of the exponential circuit is electrically connected to the low-pass filter.

[0056] In some possible implementations, the first logarithmic circuit and the second logarithmic circuit respectively include: a first operational amplifier, a first resistor, a second resistor, and a first transistor;

[0057] The inverting input terminal of the first operational amplifier is electrically connected to the second end of the first resistor and the collector of the first transistor respectively, the positive input terminal of the first operational amplifier is electrically connected to the first end of the second resistor, and the second end of the second resistor and the base of the first transistor are grounded;

[0058] The output end of the first operational amplifier is electrically connected to the emitter of the first transistor and the first input end of the adding circuit or to the emitter of the first transistor and the second input end of the adding circuit.

[0059] In some possible implementations, the adding circuit includes: a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, and a third operational amplifier;

[0060] The second end of the third resistor, the second end of the fourth resistor, and the first end of the fifth resistor are electrically connected to the inverting input terminal of the third operational amplifier, and both ends of the sixth resistor are electrically connected to the positive input terminal of the third operational amplifier and the ground respectively;

[0061] The output terminal of the third operational amplifier is electrically connected to the second end of the sixth resistor and the input terminal of the exponential circuit.

[0062] In some possible implementations, the exponential circuit includes: a second transistor, a seventh resistor, an eighth resistor, and a fourth operational amplifier;

[0063] The emitter of the second transistor, the first end of the seventh resistor and the inverting input end of the fourth operational amplifier are electrically connected;

[0064] Two ends of the eighth resistor are electrically connected to the positive input terminal of the fourth operational amplifier and the ground;

[0065] The output end of the fourth operational amplifier is electrically connected to the second end of the seventh resistor and the input end of the low-pass filter;

[0066] The collector of the second transistor and the base of the second transistor are electrically connected to the output end of the adding circuit.

[0067] For example, Figure 2 As shown, a multiplication circuit is shown, which includes two logarithmic circuits, an addition circuit, and an exponential circuit. The circuits with Amp1 and Amp2 as the core are two logarithmic circuits, the circuit with Amp3 as the core is an addition circuit, and the circuit with Amp4 as the core is an exponential circuit. The two logarithmic circuits have the same structure. The first logarithmic circuit includes an operational amplifier Amp1, resistors R21 and R22, and transistor T1. The second logarithmic circuit includes an operational amplifier Amp2, resistors R23 and R24, and transistor T2. The addition circuit includes an operational amplifier Amp3, resistors R35, R36, R37, and R38. The exponential circuit includes an operational amplifier Amp4, resistors R41 and R42, and transistor T3.

[0068] In some possible implementations, the low-pass filter includes: a pre-resistor and a bypass capacitor, the second end of the pre-resistor is electrically connected to the first end of the bypass capacitor and the input end of the proportional integral circuit, the second end of the bypass capacitor is grounded, and the first end of the pre-resistor is electrically connected to the output end of the multiplication circuit.

[0069] For example, Figure 3 As shown, a low-pass filter is shown, which includes a pre-resistor R71 and a bypass capacitor C71. The circuit bypasses the high-frequency signal from the bypass capacitor so that a low-frequency signal is obtained at the rear end of the pre-resistor, thereby smoothing the signal obtained at the rear end of the pre-resistor.

[0070] In some possible implementations, the proportional-integral circuit includes: a fifth operational amplifier, a twelfth resistor, a thirteenth resistor, and a third capacitor;

[0071] The inverting input terminal of the fifth operational amplifier is electrically connected to the second end of the twelfth resistor and the first end of the third capacitor, and the positive input terminal of the fifth operational amplifier is grounded;

[0072] The second end of the third capacitor is electrically connected to the first end of the thirteenth resistor, and the second end of the thirteenth resistor is electrically connected to the output end of the fifth operational amplifier and the control end of the voltage-controlled phase shifter.

[0073] For example, Figure 4As shown, the proportional-integral circuit is centered around operational amplifier Amp5 and includes resistors R81 and R82, and capacitor C81. This circuit inputs a smoothed signal smoothed by a low-pass filter and performs proportional and integral operations on the smoothed signal. The results of these operations are then fed into a subsequent voltage-controlled phase shifter. When the voltage of the signal output by the proportional-integral circuit is higher, the phase shifting effect of the voltage-controlled phase shifter becomes stronger, further increasing the phase difference between the phase-shifted waveform and the voltage waveform, ultimately weakening the smoothed signal obtained after filtering. Due to the presence of the integrator, as long as the amplitude of the smoothed signal is not zero, a signal is generated that further weakens the smoothed signal until the amplitude of the smoothed signal reaches zero. At this point, the signal instructing the voltage-controlled phase shifter is negatively correlated with the power factor. The signal output by the proportional-integral circuit has a one-to-one correspondence with the power factor, and the power factor can be determined using the signal output by this proportional-integral circuit.

[0074] In some possible implementations, the voltage-controlled phase shifter includes: a sixth operational amplifier, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, and a varactor diode;

[0075] The second end of the fourteenth resistor and the first end of the fifteenth resistor are electrically connected to the inverting input terminal of the sixth operational amplifier, the first end of the fourteenth resistor is grounded, and the second end of the fifteenth resistor is electrically connected to the output terminal of the sixth operational amplifier;

[0076] The second end of the sixteenth resistor and the cathode of the varactor diode are electrically connected to the positive input terminal of the sixth operational amplifier;

[0077] The anode of the varactor diode is electrically connected to the output end of the proportional-integral circuit, and the output end of the sixth operational amplifier is electrically connected to the phase-shift input end of the multiplication circuit.

[0078] For example, Figure 5 As shown, the voltage-controlled phase shifter is based on the operational amplifier Amp6, and includes the operational amplifier Amp6, resistors R91, R92, R93, and varactor C91. This circuit inputs a control signal to the end of the varactor C91 away from the operational amplifier. When the control signal becomes stronger, the phase shift angle increases. When the phase shift angle is equal to the sum of the phase angles of the current and voltage, the phase shift angle increases. When , the smoothed signal is 0.

[0079] It should be understood that the size of the serial numbers of each step in the above embodiment does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present utility model.

[0080] The following is an embodiment of the device of the present invention. For details not described in detail, please refer to the corresponding method embodiment described above.

Claims

1. A power factor extraction circuit, characterized in that: include: Multiplication circuit, low-pass filter, proportional-integral circuit, and voltage-controlled phase shifter; The output end of the multiplication circuit is electrically connected to the input end of the low-pass filter, the output end of the low-pass filter is electrically connected to the input end of the proportional-integral circuit, the output end of the proportional-integral circuit is electrically connected to the control end of the voltage-controlled phase shifter, and the output end of the voltage-controlled phase shifter is electrically connected to the phase-shift input end of the multiplication circuit; When a current waveform and a voltage waveform are respectively input to the input end of the voltage-controlled phase shifter and the voltage waveform input end of the multiplication circuit, the voltage-controlled phase shifter generates a phase-shifted waveform according to the output of the proportional-integral circuit, the multiplication circuit multiplies the phase-shifted waveform and the voltage waveform to generate a mixed waveform, the low-pass filter filters the mixed waveform to generate a smooth waveform, and the proportional-integral circuit performs a calculation based on the smooth waveform to generate a power factor indication signal.

2. The power factor extraction circuit according to claim 1, characterized in that: The multiplication circuit includes: an addition circuit, a first logarithmic circuit, a second logarithmic circuit and an exponential circuit; The output end of the first logarithm circuit and the output end of the second logarithm circuit are electrically connected to the first input end of the adding circuit and the second input end of the adding circuit respectively, and the output end of the adding circuit is electrically connected to the input end of the exponential circuit; An input end of the second logarithmic circuit is electrically connected to an output end of the voltage-controlled phase shifter, and an output end of the exponential circuit is electrically connected to the low-pass filter.

3. The power factor extraction circuit according to claim 2, characterized in that: The first logarithmic circuit and the second logarithmic circuit respectively include: a first operational amplifier, a first resistor, a second resistor and a first transistor; The inverting input terminal of the first operational amplifier is electrically connected to the second end of the first resistor and the collector of the first transistor respectively, the positive input terminal of the first operational amplifier is electrically connected to the first end of the second resistor, and the second end of the second resistor and the base of the first transistor are grounded; The output end of the first operational amplifier is electrically connected to the emitter of the first transistor and the first input end of the adding circuit or to the emitter of the first transistor and the second input end of the adding circuit.

4. The power factor extraction circuit according to claim 2, characterized in that: The adding circuit includes: a third resistor, a fourth resistor, a fifth resistor, a sixth resistor and a third operational amplifier; The second end of the third resistor, the second end of the fourth resistor, and the first end of the fifth resistor are electrically connected to the inverting input terminal of the third operational amplifier, and both ends of the sixth resistor are electrically connected to the positive input terminal of the third operational amplifier and the ground respectively; The output terminal of the third operational amplifier is electrically connected to the second end of the sixth resistor and the input terminal of the exponential circuit.

5. The power factor extraction circuit according to claim 2, characterized in that: The exponential circuit includes: a second triode, a seventh resistor, an eighth resistor and a fourth operational amplifier; The emitter of the second transistor, the first end of the seventh resistor and the inverting input end of the fourth operational amplifier are electrically connected; Two ends of the eighth resistor are electrically connected to the positive input terminal of the fourth operational amplifier and the ground; The output end of the fourth operational amplifier is electrically connected to the second end of the seventh resistor and the input end of the low-pass filter; The collector of the second transistor and the base of the second transistor are electrically connected to the output end of the adding circuit.

6. The power factor extraction circuit according to claim 1, characterized in that: The low-pass filter includes: a pre-resistor and a bypass capacitor, the second end of the pre-resistor is electrically connected to the first end of the bypass capacitor and the input end of the proportional integral circuit, the second end of the bypass capacitor is grounded, and the first end of the pre-resistor is electrically connected to the output end of the multiplication circuit.

7. The power factor extraction circuit according to claim 1, characterized in that: The proportional-integral circuit includes: a fifth operational amplifier, a twelfth resistor, a thirteenth resistor, and a third capacitor; The inverting input terminal of the fifth operational amplifier is electrically connected to the second end of the twelfth resistor and the first end of the third capacitor, and the positive input terminal of the fifth operational amplifier is grounded; The second end of the third capacitor is electrically connected to the first end of the thirteenth resistor, and the second end of the thirteenth resistor is electrically connected to the output end of the fifth operational amplifier and the control end of the voltage-controlled phase shifter.

8. The power factor extraction circuit according to any one of claims 1 to 7, characterized in that: The voltage-controlled phase shifter includes: a sixth operational amplifier, a fourteenth resistor, a fifteenth resistor, a sixteenth resistor, and a varactor diode; The second end of the fourteenth resistor and the first end of the fifteenth resistor are electrically connected to the inverting input terminal of the sixth operational amplifier, the first end of the fourteenth resistor is grounded, and the second end of the fifteenth resistor is electrically connected to the output terminal of the sixth operational amplifier; The second end of the sixteenth resistor and the cathode of the varactor diode are electrically connected to the positive input terminal of the sixth operational amplifier; The anode of the varactor diode is electrically connected to the output end of the proportional-integral circuit, and the output end of the sixth operational amplifier is electrically connected to the phase-shift input end of the multiplication circuit.

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