Method for adjusting working frequency to achieve constant voltage or constant current control of AC circuit

Abstract

The present invention discloses a method for adjusting the working frequency to achieve constant voltage or constant current control of an AC circuit, which relates to the field of industrial sensors. In the technical solution of the present invention, by giving the input parameters of constant voltage or constant current control, the frequency of the square wave signal is adjusted. After the square wave signal is processed by low-pass filtering, it is transformed into a sine wave signal of the same frequency, which directly drives the AC load through AC amplification. The working voltage or working current of the AC load is sampled in real time by a signal sampling circuit, and through noise filtering and signal amplification processing, a sine signal quantity related to the real-time working voltage or working current of the AC load is obtained. This sine signal quantity is processed by an AC rectification and filtering circuit and output as a DC voltage signal, which is transformed into a digital quantity through an ADC analog-to-digital conversion circuit. The given input parameters and the ADC analog-to-digital conversion result are analyzed and processed to adjust the frequency of the square wave signal in real time dynamically, and finally the goal of constant voltage or constant current control of the AC load is achieved.

Description

Technical Field

[0001] The present invention relates to the field of industrial sensors, and particularly to a method for adjusting the working frequency to achieve constant voltage or constant current control of an AC circuit. Background Art

[0002] In the field of industrial sensors, the sensitive elements in sensors generally require an external working excitation power supply. Common working excitation sources include: constant voltage excitation sources or constant current excitation sources, which are used to convert the change of the measured quantity into the output of an electrical signal. Among them, the excitation sources include DC excitation types and AC excitation sources. In industrial applications, the numerical values of AC constant voltage sources and AC constant current sources are generally represented by the effective values of voltage or current.

[0003] In typical industrial sensor products, the principles of realizing AC constant voltage and constant current are as Figure 2 shown. A sine AC oscillation circuit generates the excitation working frequency required for the operation of an AC load. This working frequency is generally a constant value; the sine wave signal passes through a signal conversion circuit and is converted into a square wave signal of the same frequency. At this time, the amplitude of the square wave still cannot meet the needs of the AC load; in the figure, the reason for converting the sine wave signal into a square wave signal is that directly controlling and measuring the maximum value of the sine wave is very difficult and troublesome in some electrical situations, while the measurement and control of the amplitude of the square wave are much simpler. The working power supply of the square wave amplitude conversion circuit D in the figure comes from module C. The output voltage of the module C circuit can be adjusted so that the amplitude of the square wave output by the square wave amplitude conversion circuit D becomes controllable; the square wave signal of module D passes through a low-pass (or band-pass) filter circuit and is converted into a sine wave output signal, and the amplitude of the sine wave can be adjusted accordingly. The sine wave signal is directly used to drive the AC load A after passing through an AC signal amplification circuit; the AC working voltage across the AC load A or the AC working current in the loop can be obtained through the sampling circuit module B, Figure 3 and Figure 4 are the schematic diagrams of common AC working voltage and AC working current sampling circuits. The signal output by the sampling circuit is generally also a sine wave signal. After passing through a rectification, filtering, and amplification circuit, it is converted into a DC voltage signal. This DC voltage signal is then input into the differential operation amplifier circuit K for the difference (differential) operation together with the reference signal output by the reference voltage module R; the reference DC voltage signal is generally directly related to the constant voltage or constant current of the AC load to be set; the result of the difference between the two signals reflects the deviation between the actual AC working voltage or AC working current of the AC load during operation and the actual set value. This deviation value is processed through module C and then used to change the amplitude of the square wave output by the front-end module D of the AC load excitation, thereby realizing the closed-loop control of AC constant voltage or constant current and meeting the actual application requirements.

[0004] For an AC constant voltage or constant current circuit, since the voltage and current vary continuously within a cycle, it is generally more complex than a DC constant voltage or constant current control circuit. The solutions of the existing technologies mainly propose specific circuit structures and implementation forms of different constant voltage or constant current circuits for different types of AC loads and different application requirements, and different circuit implementation forms for the sampling circuit and its signal processing; different closed-loop control methods or algorithms are proposed for the closed-loop control of constant voltage and constant current; essentially, the square wave output amplitude of module D is adjusted to achieve the required constant voltage or constant current control when the AC load is working.

[0005] Starting from module C, passing through module D, module G, and module H, until the terminal of the AC load A, the maximum operating voltage of these modules must be greater than or at least equal to the maximum operating voltage of the AC load. When the operating voltage of the AC load is relatively high, this greatly increases the design cost and difficulty of the circuits (inside) of these modules. Electronic components that can simultaneously meet the requirements of a high operating voltage range, low temperature drift, and high stability accuracy are often very scarce in the market, and in some application fields, it becomes very difficult to implement the hardware circuits of the existing technology solutions. Secondly, to achieve high-precision constant voltage or constant current control of the AC load, essentially, higher requirements are also imposed on the circuit accuracy of the reference voltage module R, the differential operational amplifier circuit K for DC signals, and the module C with adjustable output voltage amplitude, increasing the cost and uncertainty of the solution implementation. For this reason, we propose a method of adjusting the operating frequency to achieve constant voltage or constant current control of the AC circuit. Summary of the Invention

[0006] The main object of the present invention is to provide a method of adjusting the operating frequency to achieve constant voltage or constant current control of the AC circuit, which can effectively solve the problems in the background technology.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A method of adjusting the operating frequency to achieve constant voltage or constant current control of the AC circuit, the method is applicable to an AC circuit including inductive, capacitive, or both inductive and capacitive components, and includes:

[0009] Setting constant voltage or constant current control input parameters;

[0010] Outputting a square wave signal according to the input parameters, converting it into a sine wave signal of the same frequency after low-pass filtering, and then driving the AC load after AC amplification;

[0011] Sampling and outputting the operating voltage or operating current of the AC load, and after being processed by a noise filtering and signal amplification circuit, outputting a sine signal quantity related to the real-time operating voltage (or called terminal voltage) or operating current when the AC load is working;

[0012] The output sine signal quantity is processed by an AC rectification and filtering circuit and then converted into a DC voltage signal for output.

[0013] The output DC voltage signal is converted into a digital quantity through an ADC analog-to-digital conversion circuit, and the ADC analog-to-digital conversion result is output.

[0014] The input parameters and the ADC analog-to-digital conversion result are comprehensively analyzed and processed to adjust in real time the frequency of the square wave signal required for constant voltage or constant current control of the AC load. The calculation formula for the square wave signal frequency is as follows:

[0015]

[0016] In the formula, f L is the operating signal frequency of the inductor device in the AC circuit, f C is the operating frequency of the capacitor device in the AC circuit, f L and f C are generally equal and the same as the square wave frequency; j is the imaginary unit; X L is the AC impedance of the inductor device in the AC circuit; L is the inductance value; X c is the AC impedance of the capacitor device in the AC circuit; C is the capacitance value.

[0017] The method is implemented through a control system. The control system includes unit module R, unit module S, low-pass filter circuit G, AC amplification circuit H, signal sampling circuit B, noise filtering and signal amplification circuit Q, AC rectification and filtering circuit P, analog-to-digital ADC conversion circuit K, and AC load A.

[0018] The unit module R is used for the user to set the constant voltage or constant current control input parameters.

[0019] The unit module S is used for outputting and adjusting the square wave signal frequency.

[0020] The low-pass filter circuit G is used to convert the square wave signal output by the unit module S into a sine wave signal of the same frequency.

[0021] The AC amplification circuit H is used to amplify the obtained sine wave signal to obtain a driving signal that can be directly used to drive the AC load A.

[0022] The sampling circuit B is used to sample and output the working voltage or working current of the AC load A.

[0023] The noise filtering and signal amplification circuit Q is used to perform noise filtering and signal amplification on the sampled signal output by the sampling, and output a sine signal quantity related to the real-time working voltage or working current when the AC load A is working.

[0024] The AC rectification and filtering circuit P is used to perform AC rectification and filtering on the output sine signal quantity, and transform and output it into a DC voltage signal;

[0025] The analog-to-digital ADC conversion circuit K is used to convert the output DC voltage signal into a digital quantity and output it to the unit module S.

[0026] The unit module S includes an internal functional unit module and an external functional unit module. The internal functional unit module includes a PLL phase-locked loop circuit, a frequency division circuit, a square wave frequency output circuit, a frequency control and adjustment circuit, a data analysis and processing circuit, and an ADC chip read / write control circuit; see Figure 6 as shown.

[0027] The external functional unit module includes a source crystal oscillator device for outputting a high-stability frequency signal to the PLL circuit;

[0028] The PLL phase-locked loop circuit is used to multiply or divide the frequency of the input clock signal to generate a new clock frequency signal;

[0029] The PLL phase-locked loop circuit is also used to provide multiple independent clock outputs, and each output has different frequencies, phases, and duty cycles;

[0030] The high-stability clock frequency signal generated by the PLL phase-locked loop circuit passes through the frequency division circuit and the square wave frequency output circuit, and outputs a square wave frequency signal to the input end of the low-pass filter circuit G.

[0031] The ADC chip read / write control circuit is used to control the analog-to-digital ADC conversion circuit K, read the result of the analog-to-digital conversion, and input it to the data analysis and processing circuit.

[0032] The specific implementation process of the technical solution of the present invention includes the following steps:

[0033] Step 1: The user sets the constant voltage or constant current control input parameters through the unit module R;

[0034] Step 2: The unit module S outputs a square wave signal according to the input parameters. After passing through the low-pass filter circuit G, it is transformed into a sine wave signal of the same frequency, and then amplified by the AC amplifier circuit H to drive the AC load A;

[0035] Step 3: The sampling circuit B samples and outputs the working voltage or working current of the AC load. After passing through the noise filtering and signal amplification circuit Q, it outputs a sine signal quantity related to the real-time working voltage or working current when the AC load A is working;

[0036] Step 4: Output a sine signal. After being transformed by the AC rectification and filtering circuit P, it outputs a DC voltage signal. The analog-to-digital ADC conversion circuit K converts the output DC voltage signal into a digital quantity and outputs it to the unit module S;

[0037] Step 5: The unit module S comprehensively analyzes and processes the input parameters and the ADC analog-to-digital conversion results, and adjusts in real time the frequency of the square wave signal required for the constant voltage or constant current control of the AC load.

[0038] The technical principle of the present invention is described as follows:

[0039] In an AC circuit, an AC load can generally be equivalent to a series-parallel connection of resistors, inductors, and capacitors. For the inductors and capacitors in an AC circuit, their impedances can be expressed as:

[0040] X L = jωL ①

[0041]

[0042] In Equation ① and Equation ②, ω is the angular frequency, ω = 2πf, and f is the operating frequency of the AC circuit. Therefore, by changing the magnitude of the operating frequency f, the magnitudes of the AC impedances of the inductor and capacitor can be changed. In an AC circuit loop, the change in the AC impedance of each (element) device means that: the operating voltage (terminal voltage) of each (element) device in the circuit changes, and the current in the circuit loop will also change. The present invention precisely utilizes this basic principle to achieve: in an AC circuit, constant voltage control of the operating voltage (or called terminal voltage) of the AC load, or constant current control of the operating current of the AC load.

[0043] In this invention patent, the AC load generally refers to: the sensor product itself or the sensitive element (unit) in the sensor. The measured quantity will cause some electrical parameter values in the AC load to change. To achieve effective measurement, it is required that the operating voltage (or called terminal voltage) or the operating current of the AC load must remain constant.

[0044] Take Figure 5 the shown AC circuit to further illustrate the principle of using the method of adjusting the operating frequency to achieve constant voltage or constant current control proposed by the present invention. Figure 5 In it, U i is the AC voltage working power supply, and its amplitude remains unchanged; R2 in the circuit is generally called the adjustment resistor, and its resistance value remains unchanged; without loss of generality, the AC load is equivalent to the series-parallel connection of the resistor, inductor, and capacitor in the figure.

[0045] Figure 5 In it, the total impedance of the AC load can be expressed as:

[0046]

[0047] The operating voltage (terminal voltage) U of the AC load in the figure Load , and the calculation expression is:

[0048]

[0049] The operating current i of the AC load in the figure, and the calculation expression is:

[0050]

[0051] Both Equation ③ and Equation ④ are only functions of the angular frequency ω, where ω = 2πf and f is the operating frequency of the circuit. It can be seen from Equation (3) that by adjusting U in the circuit i the operating frequency of the AC (excitation) power supply (while the amplitude of the operating power supply remains unchanged), since the AC load contains inductive and capacitive components, its equivalent impedance X Load will change accordingly; R2 is the regulating resistor and its resistance value always remains unchanged; therefore, in Figure 5 the shown series circuit loop, the voltage division ratio between R2 and the equivalent impedance X of the AC load Load , will change accordingly. We can always select an appropriate operating frequency to keep the terminal voltage of the AC load unchanged, that is, constant voltage control is achieved.

[0052] Similarly, it can be seen from Equation ④ that when it is necessary to keep the current of the AC load constant, the operating frequency of U in the circuit can also be adjusted i the operating frequency of the AC (excitation) power supply, and the equivalent impedance X of the AC load Load will change accordingly, and the total impedance of the series loop will change accordingly. We can always select an appropriate operating frequency to keep the operating current of the AC load unchanged, that is, constant current control is achieved.

[0053] The present invention has the following beneficial effects:

[0054] Compared with the prior art, by changing the operating frequency in the AC circuit, the operating voltage or operating current of the AC load is adjusted, so as to achieve the purpose of constant voltage control of the operating voltage (terminal voltage) of the AC load, or constant current control of the operating current of the AC load;

[0055] Compared with the prior art, for the constant voltage or constant current control method proposed by the present invention, in the AC circuit, the circuit formed by each component can be a non-linear AC circuit or a linear AC circuit; it can be a simple series-parallel circuit or a complex circuit form, and all have applicability. Description of the Drawings

[0056] Figure 1 is the control principle block diagram of the method proposed by the present invention;

[0057] Figure 2 It is a block diagram of the AC constant voltage or constant current control principle for existing industrial sensor products;

[0058] Figure 3 It is the principle of AC voltage sampling Figure 1 ;

[0059] Figure 4 It is the principle of AC current sampling Figure 2 ;

[0060] Figure 5 It is a schematic circuit diagram for the principle explanation of achieving constant voltage or constant current control by adjusting the working frequency;

[0061] Figure 6 It is an explanatory diagram of the function analysis of unit module S in Embodiment 1;

[0062] Figure 7 It is a structural diagram of a differential inductive sensor. Specific implementation manners

[0063] The following further describes the present invention in conjunction with specific implementation manners. Among them, the attached drawings are only used for exemplary illustration, showing only schematic diagrams, rather than physical diagrams, and should not be construed as a limitation to the present invention. In order to better illustrate the specific implementation manners of the present invention, some components in the attached drawings will be omitted, enlarged or reduced, which do not represent the dimensions of actual products.

[0064] The case description of the technical implementation solution of the present invention is as follows:

[0065] The constant voltage or constant current control method proposed by the present invention, the overall technical solution for its implementation is as Figure 1 shown. In the implementation of the technical solution of this invention patent, taking the use of FPGA (Field Programmable Gate Array) as the main control chip to complete as an example for description.

[0066] Figure 1 The implementation manner of the function of unit module S in Figure 6 is as shown. The final output of module S is a square wave signal, and the frequency of the square wave is adjusted in real time to achieve real-time control of the constant voltage (or constant current) of the working voltage of the AC load. The square wave signal output by module S passes through the low-pass filter circuit G and is transformed into a sine wave signal of the same frequency, and then through the amplification of the AC amplification circuit H, and finally directly drives the AC load A.

[0067] The sampling circuit B, the specific implementation method can refer to Figure 3 and Figure 4 ; In Figure 3The circuit structure uses a sampling resistor in series voltage division, and the sampling resistors are connected in series and then in parallel across the load to obtain the actual working voltage amplitude across the AC load. In the figure, R1 and R2 are sampling resistors; in Figure 4 For an AC load that needs to meet AC constant current drive (or some unit functional circuits inside the actual AC load), a sampling resistor R3 is connected in series in its working circuit. The voltage across the sampling resistor reflects the magnitude of the working current in the circuit loop. The signal output by the sampling circuit passes through a (noise) filter and a signal (conditioning) amplifier circuit Q, and finally outputs a sine signal quantity related to the working voltage (or working current) when the AC load is working; the sine signal quantity output by the Q module passes through an AC rectification and filtering circuit P and is converted into a DC voltage signal. The analog-to-digital ADC conversion circuit K converts this DC voltage signal into a digital quantity and outputs it to the module S for the module S to analyze and process, so as to adjust the square wave frequency required for the AC load constant voltage (or constant current) control in real time.

[0068] In Figure 1 For the square wave output by the S unit module, the square wave amplitude is required to be constant. After passing through the unit modules G and H, it outputs a sine wave working power supply voltage to drive the AC load A. If it works in the constant voltage mode, the working voltage amplitude of the actual load is constant.

[0069] Corresponding to Figure 1 In, the function description of the unit module S is as Figure 6 shown, and it can be implemented using a single FPGA (Field Programmable Gate Array) chip. Figure 6 The functional unit modules included therein are: PLL phase-locked loop circuit, frequency division circuit, square wave frequency output circuit, frequency control and adjustment circuit, data analysis and processing circuit, ADC chip read and write control circuit. These functional circuits can all be implemented by programming the FPGA.

[0070] The external active crystal oscillator device outputs a frequency signal with high stability (small frequency temperature coefficient) and inputs it to the PLL (Phase-Locked Loop) circuit inside the FPGA. The PLL phase-locked loop circuit is generally included in the clock management and signal processing module inside the FPGA chip, which can multiply or divide the frequency of the input clock signal to generate a new clock frequency; the PLL phase-locked loop circuit can also provide multiple independent clock outputs, and each output can have different frequencies, phases, and duty cycles, so as to flexibly meet the clock requirements of different circuit modules inside the FPGA.

[0071] The extremely high stability clock frequency signal generated by the PLL phase-locked loop circuit passes through the frequency division circuit and the square wave frequency output circuit, and outputs a square wave frequency signal to the input end of the unit module G in Figure 1 .

[0072] Figure 6 The ADC chip read-write control circuit therein can Figure 1 control the analog-to-digital conversion ADC circuit (the ADC functional circuit can be implemented by a circuit composed of a single chip) in unit module K therein, read the result of the analog-to-digital conversion, and finally input it to Figure 6 the data analysis and processing unit circuit therein.

[0073] Figure 1 Unit module R therein is generally used by users to set the constant voltage or constant current control input parameters. The preset parameters and the result of the ADC analog-to-digital conversion are Figure 6 compared by the data analysis and processing circuit (module) inside the FPGA chip therein. After necessary data analysis and processing are completed, it is output to the frequency control and adjustment circuit, and finally the real-time adjustment of the square wave frequency is completed, achieving the purpose of constant voltage or constant current control of the AC load.

[0074] Specific application cases of the technical solution of the present invention are described as follows:

[0075] Case 1:

[0076] The differential inductance sensor can be used for high-precision displacement measurement. This sensor measures the displacement of an object by detecting the change in inductance and is usually used in precision measurement and control systems. In this case, we regard the differential inductance sensor as Figure 1 the AC load therein. Achieving constant voltage and constant current control is a basic condition for the operation of this sensor. Therefore, the technical problems proposed by the present invention and its implementation approach have practical application value.

[0077] As Figure 7 shown, the main components of the differential inductance sensor include:

[0078] 1) Coils L1 and L2. The winding directions of the coils and the connection method of the like-named ends are shown in the figure to achieve the differential effect;

[0079] 2) Iron core or armature: The iron core (or called armature) is located between the coils. Its position change will cause the inductance value of the coils to change; when the iron core (or armature) moves relative to the coils, it will change the magnetic resistance of the coils, thereby changing the inductance value. In the differential structure, the inductance changes of the two coils are in opposite directions. Therefore, when the inductance of one coil increases, the inductance of the other coil decreases, and the output signal is the difference between the induced electromotive forces of the two coils, which can significantly improve the linearity of the sensor and reduce the influence of external factors.

[0080] In Figure 7In the figure, it is assumed that when the armature is in the middle position, the air gaps on both sides are both δ (defined as the balanced air gap), the cross-sectional area of the iron core magnetic pole is A0, and the number of turns of the upper and lower coils is N. Then the initial self-inductances of the two iron core coils are both:

[0081]

[0082] When the armature moves by Δδ (definition: Δδ > 0 means the armature moves upward; Δδ < 0 means the armature moves downward), then the thickness of the upper air gap becomes: δ1 = δ - Δδ, and the thickness of the lower air gap becomes: δ2 = δ + Δδ. At this time, L1 and L2 are respectively:

[0083]

[0084] When the armature moves by Δδ, the total self-inductance after the upper and lower iron core coils are connected in series is:

[0085]

[0086] Select the constant voltage source excitation method. The calculation of the differential output voltage of the sensor is explained as follows:

[0087] Let z1 and z2 be the equivalent impedances of the upper and lower iron core coils respectively, and z0 is the equivalent impedance of the iron core coil when the armature is in the middle position. Then it can be expressed as:

[0088] z1 = R1 + jωL1;

[0089] z2 = R2 + jωL2;

[0090] z0 = R0 + jωL0;

[0091] Where ω is the angular frequency of the sinusoidal AC power supply, ω = 2πf, and f is the working frequency of the AC circuit.

[0092] When the armature moves within a small range, the equivalent resistance of the coil is basically unchanged, that is, R1 = R2 = R0.

[0093] When a constant voltage source is used for excitation, the voltage difference ΔU = U1 - U2 between the two coils can be written as:

[0094]

[0095] Substituting Equation ⑥ and Equation ⑦ into it, we get:

[0096]

[0097] It can be solved to obtain:

[0098]

[0099] After simplification, we get:

[0100]

[0101] is an option less than 1, the item is even smaller, and Equation ⑩ is approximately transformed into:

[0102]

[0103] For the direct excitation mode of the constant current source, calculation of the differential output voltage of the sensor:

[0104] Refer to Figure 7 , when a constant current source is used for excitation, the voltage difference ΔU = U1 - U2 between the two coils can be written as:

[0105] ΔU = I0·(z1 - z2)

[0106] = jω(L1 - L2)·I0

[0107] Similarly, there is:

[0108]

[0109] It can be solved to obtain:

[0110]

[0111] Similarly, is an option less than 1, the item is even smaller, so Equation is approximately transformed into:

[0112]

[0113] In Equation and Equation : δ, R0, and L0 are the initial known values after the sensor is manufactured, and the set constant voltage value U0 or constant current value I0 is also a known quantity. During the measurement process, the differential output voltage ΔU of the sensor is recorded, and Figure 6 the actual output AC frequency of the circuit (ω = 2πf) is recorded. It is very easy to solve the displacement change Δδ to be measured through these two equations, that is, the measurement function of the sensor is realized.

[0114] The above shows and describes the basic principle, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for adjusting the working frequency to achieve constant voltage or constant current control of an AC circuit, characterized in that, The method is applicable to AC circuits containing inductive components, capacitive components, or both inductive and capacitive components, and includes: Setting constant voltage or constant current control input parameters; Outputting a square wave signal according to the input parameters, transforming it into a sine wave signal of the same frequency after low-pass filtering, and then driving an AC load after AC amplification; Sampling and outputting the working voltage or working current of the AC load, and then outputting a sine signal quantity related to the real-time working voltage or working current during the operation of the AC load after being processed by a noise filtering and signal amplification circuit; The output sine signal quantity is transformed and output into a DC voltage signal after being processed by an AC rectification and filtering circuit; The output DC voltage signal is converted into a digital quantity through an ADC analog-to-digital conversion circuit and output; Comprehensively analyzing and processing the input parameters and the ADC analog-to-digital conversion result, and adjusting in real time the frequency of the square wave signal required for constant voltage or constant current control of the AC load; The calculation formula for the square wave signal frequency is: where f L is the operating frequency of inductive devices in an AC circuit; f C is the operating frequency of capacitive devices in an AC circuit, and f L and f C are equal and the same as the square wave frequency; j is the imaginary unit; X L is the AC impedance of the inductor in an AC circuit; L is the inductance value; X c is the AC impedance of the capacitor in an AC circuit; C is the capacitance value.

2. The method for adjusting the working frequency to achieve constant voltage or constant current control of an AC circuit according to claim 1, characterized in that, The method is implemented through a control system, and the control system includes unit module R, unit module S, low-pass filter circuit G, AC amplification circuit H, signal sampling circuit B, noise filtering and signal amplification circuit Q, AC rectification and filtering circuit P, analog-to-digital ADC conversion circuit K, and AC load A; The unit module R is used for a user to set constant voltage or constant current control input parameters; The unit module S is used for outputting and adjusting the square wave signal frequency; The low-pass filter circuit G is used for transforming the square wave signal output by the unit module S into a sine wave signal of the same frequency; The AC amplification circuit H is used for amplifying the sine wave signal to obtain a driving signal that can be directly used to drive the AC load A; The sampling circuit B is used for sampling and outputting the working voltage or working current of the AC load A; The noise filtering and signal amplification circuit Q is used for filtering out noise and amplifying the sampled signal output by sampling, and outputting a sine signal quantity related to the real-time working voltage or working current during the operation of the AC load A; The AC rectification and filtering circuit P is used for performing AC rectification and filtering processing on the output sine signal quantity, and transforming and outputting it into a DC voltage signal; The analog-to-digital ADC conversion circuit K is used for converting the output DC voltage signal into a digital quantity and outputting it to the unit module S; The unit module S includes an internal functional unit module and an external functional unit module. The internal functional unit module includes a PLL phase-locked loop circuit, a frequency division circuit, a square wave frequency output circuit, a frequency control and adjustment circuit, a data analysis and processing circuit, and an ADC chip read / write control circuit; The external functional unit module includes a crystal oscillator device for outputting a high-stability frequency signal to the PLL circuit; The PLL phase-locked loop circuit is used for multiplying or dividing the frequency of the input clock signal to generate a new clock frequency signal; The high-stability clock frequency signal generated by the PLL phase-locked loop circuit passes through the frequency division circuit and the square wave frequency output circuit, and outputs a square wave frequency signal to the input end of the low-pass filter circuit G; The read / write control circuit of the ADC chip is used to control the analog-to-digital (ADC) conversion circuit K, read the result of the analog-to-digital conversion, and input it to the data analysis and processing circuit; The PLL phase-locked loop circuit is further used to provide multiple independent clock outputs, and each output has different frequencies, phases, and duty cycles.

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