阅读说明：本技术 一种磁特性测量系统的阻抗自动匹配装置及匹配方法 (Automatic impedance matching device and method for magnetic characteristic measurement system ) 是由 李永建 利雅婷 杨明 陈瑞颖 成昊 于 2020-07-06 设计创作，主要内容包括：本发明公开了一种磁特性测量系统的阻抗自动匹配装置及匹配方法。装置包括一个电流互感器、一个电压互感器、一个第一电压比较器、一个第二电压比较器、一个DSP、若干个MOSFET开关管驱动电路和一个电容箱；所述电容箱包括若干个第一MOSFET开关管、若干个匹配电容、一个中间电容和一个第二MOSFET开关管。本方法在测量过程时,电流互感器与电压互感器实时检测电压电流信号,经过电压比较器得到方波信号输入到DSP中,DSP经过信号计算控制MOSFET开关管驱动电路,进而自动对匹配电容进行控制,实现了实时相位检测、自动阻抗匹配和实时补偿,提高了匹配精度,全程无需人为操作,简化了实验过程和控制策略,提高了实验效率。(The invention discloses an impedance automatic matching device and an impedance automatic matching method of a magnetic characteristic measurement system. The device comprises a current transformer, a voltage transformer, a first voltage comparator, a second voltage comparator, a DSP, a plurality of MOSFET switching tube driving circuits and a capacitor box; the capacitor box comprises a plurality of first MOSFET switch tubes, a plurality of matching capacitors, an intermediate capacitor and a second MOSFET switch tube. According to the method, during the measurement process, the current transformer and the voltage transformer detect voltage and current signals in real time, square wave signals obtained through the voltage comparator are input into the DSP, the DSP controls the MOSFET switching tube driving circuit through signal calculation, and then the matching capacitor is automatically controlled, so that real-time phase detection, automatic impedance matching and real-time compensation are realized, the matching precision is improved, manual operation is not needed in the whole process, the experimental process and the control strategy are simplified, and the experimental efficiency is improved.)

1. An impedance automatic matching device of a magnetic characteristic measurement system is characterized by comprising a current transformer, a voltage transformer, a first voltage comparator, a second voltage comparator, a DSP, a plurality of MOSFET switching tube driving circuits and a capacitance box; the capacitor box comprises a plurality of first MOSFET switch tubes, a plurality of matching capacitors, an intermediate capacitor and a second MOSFET switch tube;

the current transformer is connected into the magnetic characteristic measurement system, and a current signal in an excitation loop of the magnetic characteristic measurement system is obtained through sampling; the output end of the current transformer is connected with the second voltage comparator; the voltage transformer is connected into the magnetic characteristic measurement system, and a voltage signal in an excitation loop is obtained through sampling; the output end of the voltage transformer is connected with the first voltage comparator; the first voltage comparator and the second voltage comparator are both connected with the signal input end of the DSP; a plurality of signal output ends of the DSP are respectively connected with the matching capacitor through respective MOSFET switch tube driving circuits and respective first MOSFET switch tubes, and the other signal output end of the DSP is connected with the intermediate capacitor through the MOSFET switch tube driving circuit and a second MOSFET switch tube; the middle capacitor and the second MOSFET switching tube are connected in series, the plurality of matching capacitors are connected in series with the respective first MOSFET switching tubes and then connected in parallel with the input end and the output end of the capacitor box, and the input end and the output end of the capacitor box are connected into an excitation loop of the magnetic characteristic measurement system.

2. The automatic impedance matching apparatus for a magnetic characteristic measurement system according to claim 1, wherein the conductor of the magnetic characteristic measurement system is passed through a core of the current transformer.

3. The automatic impedance matching device for a magnetic characteristic measurement system according to claim 1, wherein two terminals of the voltage transformer are connected in parallel to the magnetic characteristic measurement system and connected in parallel to both ends of the power amplifier.

4. The automatic impedance matching device for a magnetic characteristic measurement system according to claim 1, wherein the second MOSFET switch tube is activated by an intermediate capacitor having a capacitance value smaller than that of all the matching capacitors.

5. The impedance automatic matching device of a magnetic characteristic measurement system according to claim 1, wherein the number of matching capacitors matches the number of first MOSFET switching tubes; the sum of the number of the matching capacitors and the number of the middle capacitors is equal to the number of the MOSFET switch tube driving circuits.

6. The automatic impedance matching device for a magnetic property measurement system according to claim 1, wherein the first voltage comparator and the second voltage comparator are of type LM 360; the IN1 pin of the LM360 is grounded, the V-pin is connected with direct-current voltage minus 5V, the V + pin is connected with direct-current voltage plus 5V, the GND end is grounded, and the NC pin and the OUT2 pin are vacant; the output end of the current transformer is connected with the IN2 end of the second voltage comparator; the output end of the voltage transformer is connected with the IN2 end of the first voltage comparator; the OUT1 terminal of the first voltage comparator and the OUT1 terminal of the second voltage comparator are both connected with the signal input terminal of the DSP.

7. An impedance automatic matching method of a magnetic characteristic measurement system is characterized by comprising the following steps:

the first step, before the measurement of magnetic characteristics begins, the testing frequency, sampling frequency and phase position of the measurement of magnetic characteristics are setValue of

secondly, starting measurement, wherein the magnetic characteristic measurement system outputs an excitation signal, and a current transformer and a voltage transformer acquire a group of power amplifier voltage signals and excitation current signals; the voltage and current signals are input into a first voltage comparator and a second voltage comparator through output ends of a current transformer and a voltage transformer, a group of square wave excitation current signals and power amplifier voltage signals are obtained through output of the first voltage comparator and the second voltage comparator, and then the group of square wave excitation current signals and the power amplifier voltage signals are respectively input into a signal input end of a DSP; at the moment, the property of the excitation loop is inductive;

thirdly, impedance matching for the first time;

obtaining the phase difference between the power amplifier voltage signal and the exciting current signal in one period by a phase difference calculation methodAnd determining the phase differenceAnd a phase setting valueThe magnitude relationship of (1);

if the phase difference is not constant

if the phase difference is not constantAccording to the phase difference

fourthly, other sub-impedance matching is carried out;

step 1, obtaining a phase difference between a power amplifier voltage signal and an excitation current signal in a period by a phase difference calculation methodAnd judgeAndthe magnitude relationship of (1);

if it isImpedance matching is not needed, and the capacitance Cx' of the excitation loop after the last impedance matching is accessed in the excitation loop at the moment, and the measurement process is continued;

if it isThen the property of the excitation loop is assumed to be inductive at that time, based onCalculating to obtain an inductance value in the excitation loop, and calculating to obtain an increase and decrease capacitance value Cr2 through the inductance value; then the capacitance Cx2 that should be connected into the excitation loop at this time is the capacitance Cx' + Cr2 that is connected into the excitation loop after the last impedance matching; the DSP controls the signal output end of the DSP to be set to be 1 or 0 according to the Cx2 value, the MOSFET switch tube driving circuit receives the control signal of the DSP, so that the on-off of the first MOSFET switch tube is controlled, the matching capacitor with the corresponding capacitance value is connected into the excitation loop, and the capacitance value connected into the excitation loop is Cx 2;

step 2, obtaining the phase difference between the power amplifier voltage signal and the exciting current signal of the next period after the exciting loop is connected with the capacitance Cx2 by a phase difference calculation methodAnd judgeAnd

if it isThen the nature of the excitation loop is capacitive at this time, based onCalculating to obtain an increase and decrease capacitance value Cr3 in the excitation loop; then the capacitance Cx3 in the excitation loop is equal to Cx2-Cr 3; the DSP controls the signal output end of the DSP to be set to be 1 or 0 according to the Cx3 value, the MOSFET switching tube driving circuit receives the control signal of the DSP, so that the on-off of the matching capacitor is controlled, the matching capacitor with the corresponding capacitance value is connected into the excitation loop, the capacitance value connected into the excitation loop is equal to Cx3, the impedance matching is completed, and the measuring process is continued;

if it isThen it is still assumed that the nature of the excitation loop at this time is inductive, based on

step 3, obtaining the phase difference between the power amplifier voltage signal and the exciting current signal of the next period after the exciting loop is connected with the capacitance Cx4 by a phase difference calculation method

if it is

if it is

fifthly, monitoring the phase difference in real time and

8. The method of automatically matching impedance of a magnetic characteristics measurement system according to claim 7, wherein the phase difference calculation method is: the DSP acquires the time difference between the rising edge of the power amplifier voltage signal and the rising edge of the exciting current signal in a period, and then calculates the phase difference between the power amplifier voltage signal and the exciting current signal in the period according to the time difference.

9. The method of automatically matching impedance of a magnetic property measurement system according to claim 7 or 8, wherein the phase difference calculation method is specifically:

when the property of the excitation loop is inductive, when the DSP acquires the rising edge of a power amplifier voltage signal in a period, the signal input end of the DSP connected with the first voltage comparator is set to be 1, the timer module starts to time until the rising edge of an excitation current signal in the same period is acquired, the signal input end of the DSP connected with the second voltage comparator is set to be 1, and the timer module stops timing to obtain a time difference; calculating according to the time difference to obtain the phase difference between the power amplifier voltage signal and the exciting current signal;

when the property of an excitation loop is capacitive, when the DSP acquires the rising edge of an excitation current signal in a period, the signal input end of the DSP connected with the second voltage comparator is set to be 1, the timer module starts to time until the rising edge of a power amplifier voltage signal in the same period is acquired, the signal input end of the DSP connected with the first voltage comparator is set to be 1, and the timer module stops timing to obtain a time difference; and calculating the phase difference between the power amplifier voltage signal and the exciting current signal according to the time difference.

10. The automatic impedance matching method for a magnetic characteristic measurement system according to claim 7, wherein the method of setting the signal output terminal of the DSP itself to 1 or 0 employs a bit-by-bit identification method; the bit-wise identification method comprises the following steps:

(1) judging the value of Cxn ten position: judging the size relationship of Cxn, 10 mu F and 20 mu F; if the particle size is more than 20 mu F, the ten position is 2; if the concentration is less than 20 mu F and more than 10 mu F, the tens position is 1; if less than 10 muF, 0 is in the ten position;

cxn is a capacitance value which is calculated in the impedance matching process and is to be connected into the excitation loop, and n is 1-6;

(2) judging the value C0 on Cxn bits: if the tens of Cxn is 2, subtracting 20 μ F from Cxn, storing the result in Cs, and rounding Cs to obtain C0; if the ten digits of Cxn are 1, subtracting 10 μ F from Cxn, storing the result in Cs, and rounding Cs to obtain C0; if the ten bits of Cxn are 0, directly storing the result into Cs, and rounding the Cs to obtain C0;

(3) judging the value C1 on Cxn decile: subtracting C0 from the Cs in the step 2) to obtain the decimal place of the Cs, and storing the decimal place to the Cs again; firstly, judging the size relationship between Cs and 0.1 muF and 1 muF; if Cs is greater than 0.1 muF and less than 1 muF, multiplying Cs by 10 and rounding to obtain C1; c1 is 0 if Cs is less than 0.1 μ F;

(4) judging the value C2 on the Cxn percentile: subtracting 0.1C1 from the Cs in the step 3), and storing the result to the Cs again; firstly, judging the size relationship of Cs with 0.01 mu F and 0.1 mu F; if Cs is greater than 0.01 μ F and less than 0.1 μ F, multiplying Cs by 100 and rounding to obtain C2; c2 is 0 if Cs is less than 0.01 μ F;

(5) judging the value C3 on the Cxn thousandth: subtracting 0.01C1 from the Cs in the step 4), and storing the result to the Cs again; firstly, judging the size relationship between Cs and 0.001 mu F and 0.01 mu F; if Cs is greater than 0.001 μ F and less than 0.01 μ F, multiplying Cs by 1000 and rounding to obtain C3; if Cs is less than 0.001 μ F, C3 is 0.

Technical Field

The invention relates to the field of magnetic characteristic measurement, in particular to an impedance automatic matching device and an impedance automatic matching method of a magnetic characteristic measurement system.

Background

Accurate measurement and simulation of magnetic properties such as magnetic hysteresis, loss and the like of magnetic materials are the key for optimizing the design of electromagnetic devices. The measurement under one-dimensional and two-dimensional conditions can not accurately describe the spatial magnetic properties of the material, so a three-dimensional magnetic property measurement system is adopted. The magnetic characteristic measuring system comprises a computer, a power amplifier, a water-cooling resistor, an exciting coil, a test sample, a sensing coil and an amplifying circuit, and realizes space rotation exciting magnetization and obtains a sensing signal. The computer outputs excitation signals to the power amplifier for amplification, the excitation coils are used for exciting the test sample after amplification, the sensing coils on the outer surface of the test sample detect sensing signals, the sensing signals are amplified by the amplifying circuit and then transmitted to the computer for result calculation processing, and magnetic characteristic data such as hysteresis loops, loss and the like under excitation are obtained. The circuit is inductive due to the exciting coils of the multiple windings and the inductive resistance in the circuit, so that the excitation is difficult and the power efficiency is greatly reduced. In order to better acquire voltage and current signals of the coil and reduce reactive loss of a circuit, capacitance compensation needs to be carried out on a line.

The magnetic measurement device adopted in the literature Liyongjian, Yangqingxin, Anjinlong, Zhao Zhigang, Zhu Jian and Soft magnetic composite material three-dimensional magnetic characteristic detection experimental research [ J ]. the report of electrotechnical science, 2012,27(09): 160-. The document of application No. 201720388703.5 discloses an automated resonant capacitor matching device suitable for a three-dimensional magnetic characteristic measurement system, which controls a mechanical switch by a single chip microcomputer only after a capacitance value is calculated manually, and does not automatically control the on/off of the switch by phase detection.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to solve the technical problem of providing an automatic impedance matching device and an automatic impedance matching method for a magnetic characteristic measurement system.

The technical scheme for solving the technical problem of the device is that the invention provides an impedance automatic matching device of a magnetic characteristic measurement system, which is characterized by comprising a current transformer, a voltage transformer, a first voltage comparator, a second voltage comparator, a DSP, a plurality of MOSFET switching tube driving circuits and a capacitor box; the capacitor box comprises a plurality of first MOSFET switch tubes, a plurality of matching capacitors, an intermediate capacitor and a second MOSFET switch tube;

the current transformer is connected into the magnetic characteristic measurement system, and a current signal in an excitation loop of the magnetic characteristic measurement system is obtained through sampling; the output end of the current transformer is connected with the second voltage comparator; the voltage transformer is connected into the magnetic characteristic measurement system, and a voltage signal in an excitation loop is obtained through sampling; the output end of the voltage transformer is connected with the first voltage comparator; the first voltage comparator and the second voltage comparator are both connected with the signal input end of the DSP; a plurality of signal output ends of the DSP are respectively connected with the matching capacitor through respective MOSFET switch tube driving circuits and respective first MOSFET switch tubes, and the other signal output end of the DSP is connected with the intermediate capacitor through the MOSFET switch tube driving circuit and a second MOSFET switch tube; the middle capacitor and the second MOSFET switching tube are connected in series, the plurality of matching capacitors are connected in series with the respective first MOSFET switching tubes and then connected in parallel with the input end and the output end of the capacitor box, and the input end and the output end of the capacitor box are connected into an excitation loop of the magnetic characteristic measurement system.

The technical scheme for solving the technical problem of the method is to provide an automatic impedance matching method of a magnetic characteristic measurement system, which is characterized by comprising the following steps of:

firstly, before the measurement of the magnetic characteristics is started, the testing frequency, the sampling frequency and the phase setting value of the measurement of the magnetic characteristics are setInputting the data into a DSP; the impedance automatic matching device is connected into an excitation loop of a magnetic characteristic measurement system; the DSP is powered on when the DSP is started and is connected with the second MOSFET switching tubeThe signal output end is arranged with 1, so that the middle capacitor is connected to the excitation loop;

secondly, starting measurement, wherein the magnetic characteristic measurement system outputs an excitation signal, and a current transformer and a voltage transformer acquire a group of power amplifier voltage signals and excitation current signals; the voltage and current signals are input into a first voltage comparator and a second voltage comparator through output ends of a current transformer and a voltage transformer, a group of square wave excitation current signals and power amplifier voltage signals are obtained through output of the first voltage comparator and the second voltage comparator, and then the group of square wave excitation current signals and the power amplifier voltage signals are respectively input into a signal input end of a DSP; at the moment, the property of the excitation loop is inductive;

thirdly, impedance matching for the first time;

obtaining the phase difference between the power amplifier voltage signal and the exciting current signal in one period by a phase difference calculation method

And determining the phase differenceAnd a phase setting value

The magnitude relationship of (1);

if the phase difference is not constantImpedance matching is not needed, and at the moment, an intermediate capacitor is connected into the excitation loop, and the measurement process is continued;

if the phase difference is not constant

According to the phase differenceCalculating to obtain an inductance value in the excitation loop, and calculating to obtain an increase and decrease capacitance value Cr1 through the inductance value; because the exciting loop is inductive during the first impedance matching, the exciting loop should be connectedCapacitance Cx1 in the loop is equal to capacitance + Cr1 of the intermediate capacitor; the DSP controls the signal output end of the DSP to be set to be 1 or 0 according to the Cx1 value, the MOSFET switch tube driving circuit receives the control signal of the DSP, so that the on-off of the first MOSFET switch tube is controlled, the matching capacitor with the corresponding capacitance value is connected into the excitation loop, the capacitance value connected into the excitation loop is Cx1, and the impedance matching is completed; continuing the measuring process;

fourthly, other sub-impedance matching is carried out;

step 1, obtaining a phase difference between a power amplifier voltage signal and an excitation current signal in a period by a phase difference calculation method

And judgeAnd

the magnitude relationship of (1);

if it isImpedance matching is not needed, and the capacitance Cx' of the excitation loop after the last impedance matching is accessed in the excitation loop at the moment, and the measurement process is continued;

if it is

Then the property of the excitation loop is assumed to be inductive at that time, based on

Calculating to obtain an inductance value in the excitation loop, and calculating to obtain an increase and decrease capacitance value Cr2 through the inductance value; then the capacitance Cx2 that should be connected into the excitation loop at this time is the capacitance Cx' + Cr2 that is connected into the excitation loop after the last impedance matching; the DSP controls the signal output end of the DSP to be set to 1 or 0 according to the Cx2 value, and the MOSFET switch tube driving circuit receives the control signal of the DSP, thereby controlling the first MOSFET switch tubeThe matching capacitor with the corresponding capacitance value is connected into the excitation loop, so that the capacitance value of the connected excitation loop is Cx 2;

step 2, obtaining the phase difference between the power amplifier voltage signal and the exciting current signal of the next period after the exciting loop is connected with the capacitance Cx2 by a phase difference calculation methodAnd judgeAnd

the magnitude relationship of (1);

if it is

Then the nature of the excitation loop is capacitive at this time, based onCalculating to obtain an increase and decrease capacitance value Cr3 in the excitation loop; then the capacitance Cx3 in the excitation loop is equal to Cx2-Cr 3; the DSP controls the signal output end of the DSP to be set to be 1 or 0 according to the Cx3 value, the MOSFET switching tube driving circuit receives the control signal of the DSP, so that the on-off of the matching capacitor is controlled, the matching capacitor with the corresponding capacitance value is connected into the excitation loop, the capacitance value connected into the excitation loop is equal to Cx3, the impedance matching is completed, and the measuring process is continued;

if it is

Then it is still assumed that the nature of the excitation loop at this time is inductive, based on

Calculating to obtain an inductance value in the excitation loop, and calculating to obtain an increase and decrease capacitance value Cr3 through the inductance value; then the capacitance Cx4 which is equal to Cx2+ Cr3 should be switched into the excitation loop; the DSP controls the signal output end of the DSP according to the Cx4 value1 or 0, the MOSFET switch tube driving circuit receives a control signal of the DSP, so that the on-off of the first MOSFET switch tube is controlled, and further, the matching capacitor with the corresponding capacitance value is connected into the excitation loop, so that the capacitance value connected into the excitation loop is Cx 4;

step 3, obtaining the phase difference between the power amplifier voltage signal and the exciting current signal of the next period after the exciting loop is connected with the capacitance Cx4 by a phase difference calculation methodAnd judging each cycleAndthe magnitude relationship of (1);

if it isThen the nature of the excitation loop is capacitive at this time, based on

Calculating to obtain an increase and decrease capacitance value Cr4 in the excitation loop; then the capacitance Cx5 in the excitation loop is equal to Cx4-Cr 4; the DSP controls the signal output end of the DSP to be set to be 1 or 0 according to the Cx5 value, the MOSFET switching tube driving circuit receives the control signal of the DSP, so that the on-off of the matching capacitor is controlled, the matching capacitor with the corresponding capacitance value is connected into the excitation loop, the capacitance value connected into the excitation loop is equal to Cx5, the impedance matching is completed, and the measuring process is continued;

if it is

The property of the excitation loop is inductive at this time, and the phase difference is usedCalculating to obtain inductance value in the exciting loop, and calculating to obtain increased and decreased capacitanceThe value Cr 4; then the capacitance Cx6 which is equal to Cx4+ Cr4 should be switched into the excitation loop; the DSP controls the signal output end of the DSP to be set to be 1 or 0 according to the Cx6 value, the MOSFET switch tube driving circuit receives the control signal of the DSP, so that the on-off of the first MOSFET switch tube is controlled, the matching capacitor with the corresponding capacitance value is connected into the excitation loop, the capacitance value of the connected excitation loop is Cx6, the impedance matching is completed, and the measurement process is continued;

fifthly, monitoring the phase difference in real time andand the size relationship between the magnetic characteristic and the impedance is matched according to the fourth step when impedance matching is required until the whole magnetic characteristic measurement is finished.

Compared with the prior art, the invention has the beneficial effects that:

(1) the device utilizes the advantage of small delay of the DSP to carry out phase real-time detection, and improves the accuracy of impedance matching, thereby enabling the sample to be easily excited in the measuring process and improving the working efficiency of the power supply.

(2) In the measuring process, when the difference between the exciting current and the power amplifier voltage is changed due to rise of magnetic density or other reasons, the current transformer and the voltage transformer detect a voltage current signal in real time, a square wave signal is obtained through a voltage comparator and input into the DSP, the DSP controls the MOSFET switching tube driving circuit through signal calculation, and then the accessed matching capacitor is automatically controlled, so that real-time phase detection, automatic impedance matching and real-time compensation are realized, the matching precision is improved, manual operation is not needed in the whole process, the experimental process and the control strategy are simplified, and the experimental efficiency is improved.

(3) The capacitance value is identified by using the bit-based identification function of the DSP, the accuracy can be up to 0.001 mu F, and the control strategy is simplified.

(4) If the relay is adopted to control the capacitor to be switched on and off, overvoltage is easily caused, and electric arcs are further caused. Different from the traditional mechanical switches such as relays and the like, the invention adopts the MOSFET to carry out switch control on the capacitance box, controls the access of the corresponding matching capacitor, reduces the delay, and simultaneously has the function of arc extinction due to the non-contact switch.

(5) Compared with the traditional impedance matching device, the device does not need manual calculation to look up a table and does not need to close the system, and can realize automatic impedance matching in the magnetic characteristic measurement system in the complete sense.

(6) An intermediate capacitor is added in the capacitor box and is controlled by a second MOSFET switch tube, so that the starting of the measurement loop is ensured.

Drawings

FIG. 1 is a schematic view of the connection of the apparatus of the present invention in a magnetic property measurement system;

FIG. 2 is a schematic view of the overall structural connection of the present invention;

FIG. 3 is an enlarged view of a portion of FIG. 2 in accordance with the present invention;

FIG. 4 is a schematic diagram of the connection of a first MOSFET switch tube and a matching capacitor and a second MOSFET switch tube and an intermediate capacitor according to the present invention;

FIG. 5 is a diagram of an excitation current signal and a power amplifier voltage signal captured by the current transformer and the voltage transformer of the present invention;

in the figure: 1. a current transformer; 2. a voltage transformer; 3. a first voltage comparator; 4. a second voltage comparator; 5. a DSP; 6. a MOSFET switching tube driving circuit; 7. a capacitor box; 701. a first MOSFET switch tube; 702. a matching capacitor; 703. an intermediate capacitor; 704. and a second MOSFET switch tube.

Detailed Description

Specific examples of the present invention are given below. The specific examples are only intended to illustrate the invention in further detail and do not limit the scope of protection of the claims of the present application.

The invention provides an impedance automatic matching device (device for short) of a magnetic characteristic measurement system, which is characterized by comprising a current transformer 1, a voltage transformer 2, a first voltage comparator 3, a second voltage comparator 4, a DSP5, a plurality of MOSFET switching tube driving circuits 6 and a capacitor box 7, wherein the current transformer 2 is connected with the first voltage comparator 3 through the capacitor box; the capacitor box 7 comprises a plurality of first MOSFET switch tubes 701, a plurality of matching capacitors 702, an intermediate capacitor 703 and a second MOSFET switch tube 704;

a lead of the magnetic characteristic measurement system penetrates through an iron core of the current transformer 1, the current transformer 1 is connected into the magnetic characteristic measurement system, and the current transformer 1 samples to obtain a current signal in an excitation loop of the magnetic characteristic measurement system; the output end (pin header) of the current transformer 1 is connected with the IN2 end of the second voltage comparator 4; two wiring terminals of the voltage transformer 2 are connected in parallel into the magnetic characteristic measurement system and connected in parallel at two ends of the power amplifier, and the voltage transformer 2 samples to obtain a voltage signal in an excitation loop; the output end (pin header) of the voltage transformer 2 is connected with the IN2 end of the first voltage comparator 3; the OUT1 terminal of the first voltage comparator 3 and the OUT1 terminal of the second voltage comparator 4 are both connected to the signal input terminal of the DSP5 (in this embodiment, the OUT1 terminal of the first voltage comparator 3 is connected to the eCAP1 terminal of the DSP5, and the OUT1 terminal of the second voltage comparator 4 is connected to the eCAP2 terminal of the DSP 5); a plurality of signal output ends of the DSP5 are respectively connected to matching capacitors 702 with different capacitance values through respective MOSFET switch tube driving circuits 6 and respective first MOSFET switch tubes 701, another signal output end of the DSP5 is connected to the intermediate capacitor 703 through the MOSFET switch tube driving circuits 6 and respective second MOSFET switch tubes 704 (in this embodiment, the IO1 to IO17 ports of the DSP5 are respectively connected to the matching capacitors 702 with different capacitance values through respective MOSFET switch tube driving circuits 6 and respective first MOSFET switch tubes 701, and the IO18 port is connected to the intermediate capacitor 703 through the MOSFET switch tube driving circuits 6 and the second MOSFET switch tubes 704); the second MOSFET switch tube 704 and the intermediate capacitor 703 play a role in starting, and because of the presence of the exciting coil in the measurement loop, the measurement loop is inductive when starting to measure, and in order to avoid influencing subsequent detection compensation, the intermediate capacitor 703 adopts a capacitance value which is as small as possible and smaller than the capacitance values of all the matching capacitors 702; the intermediate capacitor 703 and the second MOSFET switch tube 704 are connected in series, the matching capacitor 702 and the respective first MOSFET switch tube 701 are connected in series and then connected in parallel to each other to the input and output ends of the capacitor box 7, and the input and output ends of the capacitor box 7 are connected to the excitation loop of the magnetic characteristic measurement system.

The number of the matching capacitors 702 is matched with that of the first MOSFET switching tubes 701; the sum of the number of the matching capacitors 702 and the number of the intermediate capacitors 703 is equal to the number of the MOSFET switch tube driving circuits 6.

The current transformer 1 adopts an onboard precise micro current transformer with the model of ZMCT 103B/C; the voltage transformer 2 adopts an onboard precise miniature voltage transformer with the model of ZMPT 101B; the model number of the DSP5 is TMS320F 2835.

The first MOSFET switch tube 701 and the second MOSFET switch tube 704 are both of an IRF540 type and are of enhancement type; the MOSFET switch tube driving circuit 6 adopts a TLP250 type optical coupling isolation driving circuit; the matching capacitor and the MOSFET switch tube adopt a multi-stage parallel connection mode.

In this embodiment, an eCAP1 port of the DSP5 is a power amplifier voltage signal input; an eCAP2 port of the DSP5 is used for inputting an excitation current signal; the capacitance value of the matching capacitor 702 of the IO1 port of the DSP5 is 10 μ F; IO2 port 5 μ F; IO3 port 2 μ F; IO4 port 2 μ F; IO5 port 1 μ F; IO6 port 0.5 μ F; IO7 port 0.2 μ F; IO8 port 0.1 μ F; IO9 port 0.1 μ F; IO10 port 0.03 uF; IO11 port 0.03 uF; IO12 port 0.02 μ F; IO13 port 0.01 μ F; IO14 port 0.01 μ F; IO15 port at 0.005 μ F; IO16 port 0.002 uF; IO17 port 0.001 μ F; the capacitance of the intermediate capacitor 703 is 0.001 μ F. After all the matching capacitors 702 are connected into the excitation loop, the highest matching capacitors can reach 21.009 mu F, the accuracy can reach 0.001 mu F, the disturbance in the measurement process can be responded, and the impedance matching is completed.

The first voltage comparator 3 and the second voltage comparator 4 are LM360 in model and are respectively used for voltage zero-crossing comparison and current zero-crossing comparison; the IN1 pin of LM360 is grounded, the V-pin is connected with the DC voltage of-5V, the V + pin is connected with the DC voltage of +5V, the GND end is grounded, and the NC pin and the OUT2 pin are vacant.

The device is applied to a one-dimensional magnetic characteristic measuring system, and is configured in all directions if the three-dimensional magnetic characteristic needs to be measured.

The invention also provides an impedance automatic matching method (method for short) of the magnetic characteristic measurement system, which is characterized by comprising the following steps:

firstly, before the measurement of the magnetic characteristics is started, the testing frequency, the sampling frequency and the phase setting value of the measurement of the magnetic characteristics are setInput into the DSP 5; will be connected with the resistorThe automatic matching resisting device is connected into an excitation loop of the magnetic characteristic measuring system; the DSP5 is powered on, and a signal output end (i.e. an IO18 port) of the DSP5 connected with the second MOSFET switch tube 704 is set to be 1, so that the intermediate capacitor 703 is connected to an excitation loop;

the phase setting value

Depending on the test frequency; the sampling frequency is determined according to the test frequency, the higher the test frequency is, the higher the sampling frequency can take, and the lower the test frequency is, the lower the sampling frequency can take.

The magnetic characteristic measuring system comprises a computer, a power amplifier, a water-cooling resistor, an exciting coil, a capacitance box 7, a test sample, a sensing coil and an amplifying circuit; the measuring loop is a loop formed by a magnetic characteristic measuring system; the excitation loop of the magnetic characteristic measurement system comprises a power amplifier, a water-cooling resistor, an excitation coil and a capacitance box 7, and a series loop is formed. The magnetic characteristic measurement process comprises the following steps: the computer outputs excitation signals to the power amplifier for amplification, the excitation coils are used for exciting the test sample after amplification, the sensing coils on the outer surface of the test sample detect sensing signals, the sensing signals are amplified by the amplifying circuit and then transmitted to the computer for result calculation processing, and magnetic characteristic data such as hysteresis loops, loss and the like under excitation are obtained.

Secondly, starting measurement, wherein the magnetic characteristic measurement system outputs an excitation signal, and the current transformer 1 and the voltage transformer 2 acquire a group of power amplifier voltage signals and excitation current signals; the voltage current signal is input to the IN2 ends of the first voltage comparator 3 and the second voltage comparator 4 through the output ends of the current transformer 1 and the voltage transformer 2, and a group of excitation current signals IN a square wave form and power amplifier voltage signals are output from the OUT1 ends of the first voltage comparator 3 and the second voltage comparator 4 (see fig. 5); because the input signal of the DSP5 requires the voltage value range to be 0-3V, the voltage comparator 2 is needed to process the voltage and current signals of the measuring loop into a group of square wave signals; because the property of the excitation loop is inductive before impedance matching, the power amplifier voltage signal leads the excitation current signal; then the group of wave signals are respectively input to the signal input end of the DSP 5;

thirdly, impedance matching for the first time;

step 1, obtaining a phase difference between a power amplifier voltage signal and an excitation current signal in a period by a phase difference calculation method

And determining the phase differenceAnd a phase setting valueThe magnitude relationship of (1);

if the phase difference is not constantImpedance matching is not needed, and at the moment, the intermediate capacitor 703 is connected into the excitation loop, and the measurement process is continued;

if the phase difference is not constant

According to the phase differenceCalculating to obtain an inductance value in the excitation loop, and calculating to obtain an increase and decrease capacitance value Cr1 through the inductance value; because the exciting loop is inductive during the first impedance matching, the capacitance Cx1 in the exciting loop should be switched in to the capacitance + Cr1 of the intermediate capacitor 703; the DSP5 controls the signal output end of the DSP to be set to 1 or 0 according to the Cx1 value, the MOSFET switch tube driving circuit 6 receives the control signal of the DSP5, so as to control the on/off of the first MOSFET switch tube 701, and further to enable the matching capacitor 702 with the corresponding capacitance value to be connected into the excitation loop, so that the capacitance value of the connected excitation loop is Cx1, and the impedance matching is completed; continuing the measuring process;

the period is set according to the testing frequency of the magnetic characteristic measurement and is inversely related to the testing frequency of the magnetic characteristic measurement;

fourthly, other sub-impedance matching is carried out; disturbance exists in the measuring process, so that the phase of an excitation current signal is advanced to a power amplifier voltage signal, and the excitation loop is capacitive at the moment, so that after the first impedance matching is completed, the subsequent other impedance matching needs to judge the property of the excitation loop; (ii) a

Step 1, obtaining a phase difference between a power amplifier voltage signal and an excitation current signal in a period by a phase difference calculation method

And judge

And

the magnitude relationship of (1);

if it isImpedance matching is not needed, and the capacitance Cx' of the excitation loop after the last impedance matching is accessed in the excitation loop at the moment, and the measurement process is continued;

if it isThen the property of the excitation loop is assumed to be inductive at that time, based on

Calculating to obtain an inductance value in the excitation loop, and calculating to obtain an increase and decrease capacitance value Cr2 through the inductance value; then the capacitance Cx2 that should be connected into the excitation loop at this time is the capacitance Cx' + Cr2 that is connected into the excitation loop after the last impedance matching; the DSP5 controls the signal output end of the DSP to be set to 1 or 0 according to the Cx2 value, the MOSFET switch tube driving circuit 6 receives the control signal of the DSP5, so as to control the on-off of the first MOSFET switch tube 701, and further to enable the matching capacitor 702 with the corresponding capacitance value to be connected into the excitation loop, so that the capacitance value of the connected excitation loop is Cx 2;

step 2,Obtaining the phase difference between the power amplifier voltage signal and the exciting current signal of the next period after the exciting loop is connected with the capacitance Cx2 by a phase difference calculation method

And judgeAnd

the magnitude relationship of (1);

if it is

Then the nature of the excitation loop is capacitive at this time, based onCalculating to obtain an increase and decrease capacitance value Cr3 in the excitation loop; then the capacitance Cx3 in the excitation loop is equal to Cx2-Cr 3; the DSP5 controls the signal output end of the DSP5 to be set to 1 or 0 according to the Cx3 value, the MOSFET switch tube driving circuit 6 receives the control signal of the DSP5, thereby controlling the on-off of the matching capacitor 702, enabling the matching capacitor 702 with the corresponding capacitance value to be connected into the excitation loop, enabling the capacitance value connected into the excitation loop to be equal to Cx3, completing the impedance matching at this time, and continuing the measuring process;

if it is

Then it is still assumed that the nature of the excitation loop at this time is inductive, based on

Calculating to obtain an inductance value in the excitation loop, and calculating to obtain an increase and decrease capacitance value Cr3 through the inductance value; then the capacitance Cx4 which is equal to Cx2+ Cr3 should be switched into the excitation loop; the DSP5 controls the signal output terminal to be set to 1 or 0 according to the Cx4 value, the MOSFET switch tube driving circuit 6 receives the control signal of the DSP5, thereby controlling the on-off of the first MOSFET switch tube 701, and further leading the matching current of the corresponding capacitance valueThe capacitor 702 is connected into the excitation loop, so that the capacitance value of the connected excitation loop is Cx 4;

step 3, obtaining the phase difference between the power amplifier voltage signal and the exciting current signal of the next period after the exciting loop is connected with the capacitance Cx4 by a phase difference calculation methodAnd judging each cycle

Andsize relationship of

If it isThen the nature of the excitation loop is capacitive at this time, based on

Calculating to obtain an increase and decrease capacitance value Cr4 in the excitation loop; then the capacitance Cx5 in the excitation loop is equal to Cx4-Cr 4; the DSP5 controls the signal output end of the DSP5 to be set to 1 or 0 according to the Cx5 value, the MOSFET switch tube driving circuit 6 receives the control signal of the DSP5, thereby controlling the on-off of the matching capacitor 702, enabling the matching capacitor 702 with the corresponding capacitance value to be connected into the excitation loop, enabling the capacitance value connected into the excitation loop to be equal to Cx5, completing the impedance matching at this time, and continuing the measuring process;

if it isThe property of the excitation loop is inductive at this time, and the phase difference is usedCalculating to obtain an inductance value in the excitation loop, and calculating to obtain an increase and decrease capacitance value Cr4 through the inductance value; then the capacitance Cx6 which is equal to Cx4+ Cr4 should be switched into the excitation loop; the DSP5 controls the signal output terminal to set 1 or 0 according to Cx6 value, and the MOSFEThe T switch tube driving circuit 6 receives the control signal of the DSP5, so as to control the on/off of the first MOSFET switch tube 701, and further to make the matching capacitor 702 with a corresponding capacitance value access the excitation loop, so that the capacitance value accessed to the excitation loop is Cx6, complete the impedance matching, and continue the measurement process;

fifthly, monitoring the phase difference in real time andand the size relationship between the magnetic characteristic and the impedance is matched according to the fourth step when impedance matching is required until the whole magnetic characteristic measurement is finished.

The phase difference calculation method comprises the following steps: the DSP5 acquires the time difference between the rising edge of the power amplifier voltage signal and the rising edge of the exciting current signal in a period, and then calculates the phase difference between the power amplifier voltage signal and the exciting current signal in the period according to the time difference.

The phase difference calculation method specifically comprises the following steps: when the property of the excitation loop is inductive, the DSP5 acquires the rising edge of the power amplifier voltage signal in a period, the signal input terminal (i.e., the eCAP1 terminal) of the DSP5 connected to the first voltage comparator 3 is set to 1, the timer module starts timing, until the rising edge of the excitation current signal in the same period is acquired, the signal input terminal (i.e., the eCAP2 terminal) of the DSP5 connected to the second voltage comparator 4 is set to 1, and the timer module stops timing to obtain a time difference; and calculating the phase difference between the power amplifier voltage signal and the exciting current signal according to the time difference. When the property of the excitation loop is capacitive, when the DSP5 acquires the rising edge of the excitation current signal in a period, setting 1 at the signal input end (i.e., the eCAP2 end) of the DSP5 connected to the second voltage comparator 4, starting timing by the timer module, setting 1 at the signal input end (i.e., the eCAP1 end) of the DSP5 connected to the first voltage comparator 3 until the rising edge of the power amplifier voltage signal in the same period is acquired, and stopping timing by the timer module to obtain a time difference; and calculating the phase difference between the power amplifier voltage signal and the exciting current signal according to the time difference.

The method for controlling the signal output end of the DSP to be set to 1 or 0 can adopt a bitwise identification method or other existing methods; the bit-wise identification method comprises the following steps:

(1) judging the value of Cxn ten position: judging the size relationship of Cxn, 10 mu F and 20 mu F; if the particle size is more than 20 mu F, the ten position is 2; if the concentration is less than 20 mu F and more than 10 mu F, the tens position is 1; if less than 10 muF, 0 is in the ten position;

cxn is a capacitance value which is calculated in the impedance matching process and is to be connected into the excitation loop, and n is 1-6;

(2) judging the value C0 on Cxn bits: if the tens of Cxn is 2, subtracting 20 μ F from Cxn, storing the result in Cs, and rounding Cs to obtain C0; if the ten digits of Cxn are 1, subtracting 10 μ F from Cxn, storing the result in Cs, and rounding Cs to obtain C0; if the ten bits of Cxn are 0, directly storing the result into Cs, and rounding the Cs to obtain C0;

(3) judging the value C1 on Cxn decile: subtracting C0 from the Cs in the step 2) to obtain the decimal place of the Cs, and storing the decimal place to the Cs again; firstly, judging the size relationship between Cs and 0.1 muF and 1 muF; if Cs is greater than 0.1 muF and less than 1 muF, multiplying Cs by 10 and rounding to obtain C1; c1 is 0 if Cs is less than 0.1 μ F;

(4) judging the value C2 on the Cxn percentile: subtracting 0.1C1 from the Cs in the step 3), and storing the result to the Cs again; firstly, judging the size relationship of Cs with 0.01 mu F and 0.1 mu F; if Cs is greater than 0.01 μ F and less than 0.1 μ F, multiplying Cs by 100 and rounding to obtain C2; c2 is 0 if Cs is less than 0.01 μ F;

(5) judging the value C3 on the Cxn thousandth: subtracting 0.01C1 from the Cs in the step 4), and storing the result to the Cs again; firstly, judging the size relationship between Cs and 0.001 mu F and 0.01 mu F; if Cs is greater than 0.001 μ F and less than 0.01 μ F, multiplying Cs by 1000 and rounding to obtain C3; if Cs is less than 0.001 μ F, C3 is 0.

For example Cxn-17.553 μ F. Firstly, judging the size relationship between the standard substance and 10 mu F and 20 mu F, and then firstly detecting whether the standard substance is more than 10 mu F or not and more than 20 mu F or not, thereby determining that the range is 10 mu F-20 mu F, namely the ten position is 1; since the ten is 1, subtracting 10 μ F from Cxn, storing the result to Cs, wherein the Cs is 7.553 μ F, and the Cxn is rounded to obtain 7 in the C0 position; c0 is subtracted from the Cs 7.553 μ F to obtain its decimal place, and the decimal place is restored to Cs, where Cs is 0.553 μ F; judging the size relationship between the decimal place and 0.1 muF and 1 muF, and determining the range between 0.1 muF and 1 muF; multiplying Cs by 0.553 μ F by 10 and rounding to obtain Cxn decile C1 of 5; subtracting 0.1C1 from Cs 0.553 μ F and storing the result back in Cs, where Cs is 0.053 μ F, multiplying Cs by 100 and rounding to give C2 on the Cxn percentile, thus giving its percentile 5 μ F; and subtracting 0.01C1 from the Cs after the calculation, and storing the result into the Cs again, wherein the Cs is 0.003 mu F, multiplying the Cs by 1000 and rounding to obtain Cxn kilogramme C2, thereby obtaining the kilogramme of 3 mu F.

Nothing in this specification is said to apply to the prior art.