CN102841258B - Measuring device and method for direct current supply output impedance - Google Patents

Abstract

The invention discloses a measuring device and method for direct current supply output impedance. The measured direct current supply output impedance is defined at a specific operating point and a specific test cross section, the presented equivalent impedance is seen in the direction of the test cross section facing a power supply, and system deviation in the measuring process, caused by load input impedance, is avoided. The measuring device comprises a test frequency point voltage phasor extraction module, a test frequency point current phasor extraction module, a low-current excitation load module, a sweep frequency phasor analysis module and a control computer, wherein the test frequency point voltage phasor extraction module and the test frequency point current phasor extraction module are respectively connected with a voltage input end and a current input end of the sweep frequency phasor analysis module; the signal output end of the sweep frequency phasor analysis module is connected with the low-current excitation load module; and the sweep frequency phasor analysis module is further connected with the control computer.

Description

A DC power supply output impedance measuring device and its measuring method

technical field

The invention relates to the technical field of impedance measurement of a DC power supply system, in particular to a device for measuring the output impedance of a DC power supply and a measurement method thereof.

Background technique

The DC power supply system is a system composed of a power supply and many loads. The impedance of the power supply system can be divided into two parts: the output impedance of the power supply and the input impedance of the load. The output impedance of the power supply is an important technical index reflecting the power supply quality, compatibility, and stability of the power supply system. The input impedance of the load is an important technical index reflecting the input filter or power converter DC-DC suppression of conducted interference and suppression of reflected power. The two are collectively referred to as the power system impedance.

Power system design and electrical load design are often completed by different research and development units at different times. Such as VXI, PXI chassis power supply, computer power bus, communication power bus, spacecraft power bus and international space station power supply, etc. Only after the output impedance of the power supply is determined, the input impedance of all loads connected in parallel is required to be far greater than the output impedance of the power supply, in order to ensure the stability of the system. Power output impedance parameters become important data for designing power systems and loads. Only by actually measuring the output impedance of the power supply and the input impedance of the load can the design indicators be checked with quantitative data. When there is interference in the power supply system, it is also necessary to actually measure the output impedance of the power supply to find the cause online. At present, foreign spacecraft power supplies have used the output impedance of the power supply as a technical indicator to evaluate the quality of the power supply. In the technical specifications of the European Space Agency, the characteristic curve requirements of the spacecraft output impedance are specified, and the stability of the cascaded DC-DC power supply is specified. Require. In order to adapt to the electrical loads from various countries and companies, the power supply system of the International Space Station has specially stipulated the limited range of power output impedance and load input impedance to ensure the stable operation of the entire system. Therefore, if there is no reliable power supply output impedance measurement technology, it is difficult to quantitatively analyze the system stability of power supply and load, and it is also difficult to propose technical requirements for power supply output impedance and load input impedance when designing a power supply system. Therefore, the power output Impedance measurement technology is an important measurement technology that needs to be developed urgently.

The characteristics of the output impedance of the DC power supply are: ①The output impedance of the DC power supply is different from the impedance of the components, and also different from the internal resistance of the power supply. The impedance of a component is determined by the material properties and geometric structure. For example, the impedance of a resistive device is determined by the resistivity and geometric shape of a conductive wire. The field number and the resistance and geometry of the lead wires are determined. The impedance of the inductance device is determined by the coil area and number of turns, the internal and external magnetic permeability of the coil, and the coil resistance and geometry. The output impedance of the power supply is different from the impedance of components. It is determined by the output characteristics of the power supply and the distribution parameters on the power bus. The output impedance of the power supply is the inherent characteristic when the power supply has power output. It is also different from the internal resistance of the power supply, which is the ratio of the change in voltage at the output of the power supply to the change in load current. Both voltage and current are in the DC state, and the so-called change refers to the difference between the two DC output states. The internal resistance can be expressed by the slope of the tangent line of the volt-ampere characteristic curve. The power supply is nonlinear, and the internal resistance is different under different working conditions. The ideal voltage source Us internal resistance Rs is zero, and the ideal current source Is internal resistance Rg is infinite. . ② The output impedance of DC power supply is the impedance under small signal conditions. The DC power supply is a nonlinear system, and the impedance is different at different operating points of voltage and current. There is a small dynamic interval near the operating point, which can be regarded as an approximately linear interval. Therefore, when measuring the power supply impedance, only a small-amplitude sinusoidal excitation current can be applied to ensure that the generated voltage disturbance is not distorted. Under such small signal conditions, only a single frequency voltage phasor and Current phasors to calculate source impedance. Generally below 10kHz, the source impedance is less than 0.1Ω. If the amplitude of the AC excitation current is less than 0.1A, the AC voltage response on the bus is less than 10mV. Such a small voltage signal will be submerged in the noise of the bus, which will seriously affect the measurement accuracy. Signal measurement is a difficult problem in impedance measurement. ③ The output impedance of DC power supply is a distributed parameter impedance. The output impedance of the power supply is not only related to the control characteristics of the power supply, but also related to the transmission line and the measurement section. In the case of high frequency (generally greater than 10kHz), the output impedance of the power supply is affected by the distribution parameters of the busbar and gradually increases, and the distribution parameters of the busbar are related to the measurement section. Select about.

Therefore, the measurement of the output impedance of a DC power supply is different from the measurement of passive impedance components, and an impedance measuring instrument cannot be used directly. It must inject current excitation or voltage excitation when the DC power supply is working, then measure the response voltage or current, and obtain the impedance measurement result by calculating the phasor ratio of voltage and current. However, in order to avoid nonlinear distortion, the excitation and response often work in the small signal range, which is very difficult for small signal measurement. Under the working condition of DC power supply, when the output impedance of the power supply is very small, such as below 0.1Ω, the AC voltage to be measured is often submerged in the noise of the DC power supply itself. At present, there are no commercialized measuring instruments and equipment for the output impedance of DC power supplies at home and abroad. However, general-purpose, commercialized impedance measuring instruments and vector network analyzers can only measure the AC impedance of passive devices, and cannot be directly used to measure the output impedance of the power supply and the input impedance of the load.

According to the records of relevant technical literature at home and abroad, the current method of measuring the output impedance of the power supply generally uses a frequency response analyzer, which generates an AC excitation signal VAC, and simultaneously measures the amplitude ratio of the bus voltage Vtest and the sampling resistor voltage Vref and Phase difference, measurement results are given in Bode plots. The measurement frequency range is 10 Hz to 200 kHz, and the frequency response analyzers used include the 350 series of Venable Company of the United States and the AP200 series of Ridley Company of the United States.

Figure 1 uses the current transformer coupling method to inject AC disturbance current. The coupling of the disturbance signal is too weak. When the impedance at the left end of the transformer is small, the signal source at the right end works in the current source state. It is difficult to use a frequency response analyzer as an excitation. The DC electronic load sets the DC operating point through the DC current I0 (DC). The input impedance of the DC electronic load is connected in parallel with the output impedance of the power supply under test, and the actual measured impedance value is the result of the parallel connection between the output impedance of the DC power supply and the input impedance of the DC electronic load. When the DC load input impedance is much greater than the power output impedance, the measurement result approximates the power output impedance. However, in high frequency bands, the input impedance of the load is often equal to the output impedance of the power supply, resulting in large errors in the measurement results.

Figure 2 uses the field effect tube to amplify the AC disturbance signal, and directly drives the field effect tube with the bus voltage. Under the higher bus voltage, its thermal noise is also amplified into the AC disturbance signal, which interferes with the normal measurement. Similarly, the measured impedance value is the result of the parallel connection between the output impedance of the power supply and the input impedance of the DC electronic load. In the case of high DC current (for example, the input impedance of the electronic load is less than 10Ω), a large system deviation will occur.

Figure 3 designs an active amplifier to amplify the sweeping signal of the frequency response analyzer to drive the coupling transformer, inject AC disturbance signals through the coupling transformer, and expand the scope of application. However, the frequency response bandwidth of the coupling transformer is narrow, and the actual measurement can only reach 200kHz, the measured impedance value also includes the parallel connection of the input impedance of the DC electronic load, resulting in a large system deviation.

A method to measure the output impedance of the power supply is also recommended in the product manual of Agilent's 4395A network analyzer, as shown in Figure 4. Like the above problem, the input impedance of the load has also become the object to be measured. The actual measurement data is the result of the parallel connection between the input impedance of the load and the output impedance of the power supply, and there is a large system deviation.

Contents of the invention

The invention discloses a DC power supply output impedance measurement device and its measurement method. The measured DC power output impedance is defined at a specific operating point (a definite DC voltage and DC current in which the power supply operates within the rated range), specific The test section, from the direction of the test section towards the power supply, presents an equivalent impedance, which overcomes the systematic deviation of the measurement process caused by the influence of the load input impedance.

Technical scheme of the present invention is:

A DC power supply output impedance measurement device, characterized in that it includes a test frequency point voltage phasor extraction module, a test frequency point current phasor extraction module, a small current excitation load module, a frequency sweep phasor analysis module and a control computer; The test frequency point voltage phasor extraction module and the test frequency point current phasor extraction module are respectively connected to the voltage input end and the current input end of the frequency sweep phasor analysis module, and the signal output end of the frequency sweep phasor analysis module is connected to a small current excitation Load module, the frequency sweep phasor analysis module is also connected with the control computer; the test frequency point voltage phasor extraction module is connected to the voltage sampling end of the test section selected on the power bus of the power supply under test connected to the load, and extracts the Measure the amplitude and phase of the voltage signal with a frequency of ω at both ends of the power supply. The test section is a cross-section between the power supply under test and the load looking towards the power supply. The current phasor extraction module at the test frequency point adopts a non-contact The method extracts the amplitude and phase of the current signal with a frequency ω flowing through the test section to the power supply under test from the power bus, the small current excitation load module is connected to the load end of the power supply under test, and the frequency sweep phasor analysis Output a sinusoidal excitation signal with a frequency of ω of a certain amplitude, introduce a sine wave current load with a frequency of ω that disturbs the power supply at the load end of the power supply under test, and the frequency sweep phasor analysis module is based on the amplitude of the received voltage signal and the magnitude and phase of the phase and current signal, calculate the magnitude and phase value of the output impedance of the measured power supply at the frequency ω in the test section; the control computer controls the output frequency ω of the frequency sweep phasor analysis module and receives The calculation results of the frequency sweep phasor analysis module are stored and post-processed.

The signal output terminal of the frequency sweep phasor analysis module is also connected to an open circuit/short circuit/load calibration excitation signal output module, and the open circuit/short circuit/load calibration excitation signal output module is connected to the load terminal when performing open circuit/short circuit/load calibration for outputting the excitation signal to the test section after the power supply and load under test and the small current excitation load module are disconnected from the power bus; the open circuit/short circuit/load calibration excitation signal output module includes a negative feedback operational amplifier, an operational amplifier The positive input terminal of the operational amplifier is connected to the signal output terminal of the frequency-sweeping phasor analysis module and the modulus value and the DC bias circuit through the adder. The output terminal of the operational amplifier is connected in series with a diode, and the positive input terminal of the diode is connected to the voltage limiting protection circuit. The negative output terminal is connected to the voltage sampling terminal of the test section through the calibration switch.

The test frequency point voltage phasor extraction module includes a first DC blocking capacitor and a second DC blocking capacitor connected to the test section voltage sampling terminal, and the first DC blocking capacitor and the second DC blocking capacitor are respectively connected to the first signal input buffer circuit and the second signal input buffer circuit, the first signal input buffer circuit and the second signal input buffer circuit are simultaneously connected to a differential amplifier circuit, and the differential amplifier circuit is connected to the voltage input terminal of the frequency-sweeping phasor analysis module.

The test frequency point current phasor extraction module includes a low-frequency test frequency point current phasor extraction module, and the low-frequency test frequency point current phasor extraction module includes a current transformer made of a magnetic ring with high magnetic permeability. A secondary induction winding and a DC compensation winding are respectively wound on the current transformer, and the secondary induction winding is sequentially connected to the current-voltage conversion circuit and the signal conditioning and frequency compensation circuit, and the signal conditioning and frequency compensation circuit is connected to the frequency sweep phasor analysis module Current input terminal; the DC compensating winding is connected to the DC current measuring device through the sequentially connected DC circuit drive circuit and the low-pass filter circuit, and the DC current measuring device converts the measured bus current signal into a voltage signal, and passes through the low-pass filter After the circuit filters out the AC components, the DC circuit drive circuit outputs a DC current capable of offsetting the magnetic induction intensity generated in the current transformer by the DC current of the power bus to the DC compensating winding.

The test frequency point current phasor extraction module includes a high-frequency test frequency point current phasor extraction module, and the high-frequency test frequency point current phasor extraction module includes a current transformer made of a magnetic ring with low magnetic permeability, A secondary induction winding is wound on the current transformer, and the secondary induction winding is sequentially connected to a current-voltage conversion circuit and a signal conditioning and frequency compensation circuit, and the signal conditioning and frequency compensation circuit is connected to the current input terminal of the frequency-sweeping phasor analysis module .

The small current excitation load module includes a negative feedback closed-loop control and drive circuit composed of an operational amplifier, a field effect transistor, and a sampling resistor. In the analog value circuit, the output terminal of the operational amplifier is connected to the control pole of the field effect transistor, and one output pole of the field effect transistor is connected to the positive pole of the measured power supply through a current limiting and fuse protection circuit, and the other output pole is connected to the negative pole of the power supply under test through a sampling resistor.

The frequency-sweeping phasor analysis module includes a digital logic device, and the test frequency point voltage phasor extraction module and the test frequency point current phasor extraction module are respectively connected to the digital logic device through an input signal conditioning circuit and an analog-to-digital conversion circuit in sequence , the digital logic device is sequentially connected to the small current excitation load module or the open circuit/short circuit/load calibration excitation signal output module through a digital-to-analog conversion circuit and an output signal conditioning circuit; the digital logic device includes a DDS directly connected to a clock chip A digital frequency synthesis unit, the DDS direct digital frequency synthesis unit is respectively connected to the sine integration module and the cosine integration module through a multiplier, and the output of the DDS direct digital frequency synthesis unit is the quadrature signal sin(ωt) of two frequencies of ω and cos(ωt) are respectively multiplied by the voltage digital signal U(t) and the current digital signal I(t) input to the digital logic device, and then sent to the sine integration module and the cosine integration module respectively, and the sine integration module and cosine The integral module is connected with the phasor division operation module, and the phasor division operation module is connected with the control computer through the communication interface; the DDS direct digital frequency synthesis unit is also connected with the digital-to-analog conversion circuit, and the generated frequency is ω sin (ωt) signal or cos(ωt) signal is output to the digital-to-analog conversion circuit; the DDS direct digital frequency synthesis unit is connected with the control computer through the communication interface, and the output frequency of the DDS direct digital frequency synthesis unit is controlled by the control computer.

A method for measuring the output impedance of a DC power supply, characterized in that the working point of the power supply under test and the load is established, and a test section is selected on the power bus connected between the power supply under test and the load, and the test section is between the power supply under test and the load. The cross-section looking towards the direction of the power supply, output a sinusoidal signal with a certain amplitude and frequency ω to the small current excitation load module as an excitation through the output terminal of the sweep frequency phasor analysis module, so that the small current excitation load module is in the power supply under test. The load end introduces a sine wave current load with frequency ω that disturbs the power supply; the voltage phasor extraction module at the test frequency point extracts the amplitude and frequency of the voltage signal at both ends of the power supply under test from the voltage sampling terminal on the test section. Phase, through the test frequency point current phasor extraction module to extract the amplitude and phase of the current signal with frequency ω flowing through the test section to the power supply under test from the power bus, and send them to the voltage input and current of the frequency sweep phasor analysis module respectively Input terminal: the ratio and angle difference of the modulus of the voltage phasor and the current phasor are calculated by the frequency sweep phasor analysis module; then the measurement results are corrected according to the data of open circuit, short circuit and load calibration at frequency ω, and finally The amplitude value and phase value of the output impedance of the measured power supply at the frequency ω in the test section; the control computer communicates with the frequency sweep phasor analysis module through the communication interface, and controls the output frequency ω of the frequency sweep phasor analysis module , receiving the output result of the swept frequency phasor analysis module for storage and post-processing.

The step of correcting the measurement results according to the data of open circuit, short circuit and load calibration at frequency ω includes:

1) Disconnect the power supply and load under test from the power bus, and disconnect the small current excitation load module from the power bus; 2) Output the excitation signal through the open circuit/short circuit/load calibration excitation signal output module connected to the load terminal Give the test section; 3) When the voltage sampling end of the test section is kept open circuit, short circuit, and connected to the standard load, respectively measure the impedance values of the open circuit, short circuit, and standard load; 4) According to these data, the output of the power supply under test Impedance measurements are corrected.

The formula for correcting the measurement results through the measurement data of open circuit and short circuit is

${\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; om</span>}}\frac{{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; sm</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; xm</span>}}}{{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; xm</span>}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; om</span>}}}}$

Z _xm is the measured value of the measured object; Z _om is the measured value when the voltage sampling terminal of the test section is kept open;

Z _sm is the measured value when the voltage sampling end of the test section is short-circuited; Z _x is the impedance value of the measured object after correction;

The method of correcting the measurement results by connecting the measurement data of the standard load is: the actual measured value of the standard load at each frequency point measured when the voltage sampling end of the test section is connected to the standard load is compared with the nominal value of each frequency point of the standard load By comparison, a correction factor is obtained, which makes the final displayed impedance value consistent with the nominal value of the standard load when measuring the standard load, and the subsequent measured values are corrected according to this correction factor.

Technical effect of the present invention:

The invention discloses a DC power supply output impedance measurement device and its measurement method, which defines the measured DC power output impedance at a specific operating point (a definite DC voltage and DC current where the power supply operates within the rated range), specifically The test section, from the direction of the test section to the power supply, shows the equivalent impedance. When measuring, select the test section on the power bus connected between the power supply under test and the load. The test section is between the power supply under test and the load. From the cross-section looking towards the direction of the power supply, the amplitude and phase of the voltage signal with frequency ω at both ends of the power supply under test are extracted from the voltage sampling terminal on the test section, and the frequency of the voltage signal flowing through the test section to the power supply under test is extracted from the power bus. The amplitude and phase of the current signal of ω effectively overcome the systematic deviation of the measurement process caused by the influence of the load input impedance in the prior art measurement method. In addition, the sinusoidal current load with a frequency of ω, which is introduced at the load end of the power supply under test and exerts disturbance on the power supply, is different from the method of actively coupling the signal source signal to the power bus in the prior art measurement method. This sinusoidal current load It is equivalent to passively putting a small power load on the power supply, drawing current from the power supply to achieve the purpose of disturbing the power supply, the frequency and amplitude of the applied sine wave current load are controllable, and small enough, not The operating point that affects the establishment of the power supply under test and the load. Furthermore, it also includes a calibration method for correcting the measurement results. Through open circuit, short circuit, and load calibration, the influence of the measurement device itself is eliminated to the greatest extent, and the output impedance value of the measured power supply that meets the error requirements is obtained.

Description of drawings

Fig. 1 is a schematic diagram of measuring the output impedance of a DC power supply using a current transformer in the prior art.

Fig. 2 is a schematic diagram of measuring the output impedance of a DC power supply using field effect transistors in the prior art.

Fig. 3 is a schematic diagram of measuring the output impedance of a DC power supply using an active amplifier in the prior art.

Figure 4 is a schematic diagram of the Agilent4395A network analyzer measuring the output impedance of the power supply.

Fig. 5 is a schematic diagram of the DC power output impedance measuring device of the present invention.

Fig. 6 is a schematic diagram of the calibration of the DC power output impedance measuring device of the present invention.

Figure 7 is a structural diagram of the output module of the open circuit/short circuit/load calibration excitation signal.

Fig. 8 is a structural diagram of the test frequency point voltage phasor extraction module.

Fig. 9 is a structure diagram of the current phasor extraction module at the low-frequency test frequency point.

Fig. 10 is a structural diagram of the current phasor extraction module at the high-frequency test frequency point.

Figure 11 is a structural diagram of a small current excitation load module.

Fig. 12 is a structural diagram of the frequency sweep phasor analysis module.

Detailed ways

Embodiments of the present invention will be described in further detail below in conjunction with the accompanying drawings.

As shown in FIG. 5 , a schematic diagram of the DC power output impedance measuring device of the present invention. A DC power supply output impedance measurement device, including a test frequency point voltage phasor extraction module, a test frequency point current phasor extraction module, a small current excitation load module, a frequency sweep phasor analysis module and a control computer; the test frequency point voltage phasor The extraction module and the test frequency point current phasor extraction module are respectively connected to the voltage input terminal U and the current input terminal I of the frequency sweep phasor analysis module, and the signal output terminal S of the frequency sweep phasor analysis module is connected to the small current excitation load module, and the frequency sweep The phasor analysis module is also connected with the control computer; the test frequency point voltage phasor extraction module is connected to the voltage sampling end point a and point b of the test section selected on the power bus of the power supply under test connected to the load, and extracts the two ends of the power supply under test The amplitude and phase of the voltage signal with frequency ω, the test section is the cross-section ab between the power supply under test and the load looking towards the power supply direction, the current phasor extraction module of the test frequency point is extracted from the power bus by a non-contact method Test the amplitude and phase of the current signal with frequency ω flowing from the cross section to the power supply under test. The small current excitation load module is connected to the load end of the power supply under test, and the frequency sweep phasor analysis module outputs a sinusoidal excitation signal with a certain amplitude and frequency ω. , introduce a sine wave current load with a frequency of ω that disturbs the power supply at the load end of the power supply under test, and the swept frequency phasor analysis module calculates the The magnitude value and phase value of the output impedance of the measured power supply of the test section at frequency ω; the control computer controls the output frequency ω of the frequency sweep phasor analysis module and receives the calculation results of the frequency sweep phasor analysis module for storage and post-processing deal with.

As shown in FIG. 6 , it is a schematic diagram of the calibration of the DC power output impedance measuring device of the present invention. The signal output terminal of the swept frequency phasor analysis module is also connected to the open circuit/short circuit/load calibration excitation signal output module, which is connected to the load terminal when performing open circuit/short circuit/load calibration. The power supply and load under test and the small current excitation load module are all disconnected from the power bus and then output excitation signals to the test section, so that the frequency sweep phasor analysis module can measure the value of its open circuit, short circuit, and standard load. Open, short, load calibration. The purpose of calibration is to eliminate the influence of the measurement device itself, such as the influence of the test fixture, the error of the system itself, and so on.

As shown in Figure 7, it is a structural diagram of the output module of the open circuit/short circuit/load calibration excitation signal. The open circuit/short circuit/load calibration excitation signal output module includes a negative feedback operational amplifier A. The positive input terminal of the operational amplifier is connected to the signal output terminal S of the frequency sweep phasor analysis module and the modulus value and DC bias circuit through an adder. The output terminal of the amplifier is connected in series with a diode D1, the positive input terminal of the diode D1 is connected to the voltage limiting protection circuit, and the negative output terminal of the diode D1 is connected to the voltage sampling terminals a and b of the test section through a calibration switch. The principle of this module circuit is to output a sinusoidal signal at the test frequency point from the sweep frequency phasor analysis module, after taking the modulus value and adding a DC bias circuit, and adding it to the input signal, the minimum value of the synthesized signal is greater than the diode D1 The pressure drop ensures that the bottom of the signal input to the cross-section test point is not clipped. The reason for adopting this method is that sometimes the calibration switch is forgotten to be disconnected during the test process, which will lead to open circuit, short circuit, and conflict between the output of the load calibration excitation signal output module and the direct connection of the bus voltage, resulting in power supply or open circuit , short circuit, load calibration excitation signal output module is damaged. The circuit of this module adopts diode series output, and the front stage of the diode plus the upper voltage protection circuit can effectively protect the safety of the power supply, open circuit, short circuit and load calibration excitation signal output module.

As shown in Figure 8, it is a structural diagram of the test frequency point voltage phasor extraction module. The test frequency point voltage phasor extraction module includes a first DC blocking capacitor C1 and a second DC blocking capacitor C2 connected to the test section voltage sampling terminal, and the first DC blocking capacitor C1 and the second DC blocking capacitor C2 are respectively connected to the first signal input The buffer circuit and the second signal input buffer circuit, the first signal input buffer circuit and the second signal input buffer circuit are connected to the differential amplifier circuit at the same time, and the differential amplifier circuit is connected to the voltage input terminal U of the frequency-sweeping phasor analysis module; The voltage signal extracted by the sampling terminal is filtered by the DC blocking capacitors C1 and C2, and then the voltage signal of the test frequency point is extracted through the input buffer circuit and the differential amplifier circuit, and sent to the voltage input terminal of the frequency sweep phasor analysis module.

The test frequency point current phasor extraction module includes a low-frequency test frequency point current phasor extraction module and a high-frequency test frequency point current phasor extraction module. The applicable range of the test frequency point current phasor extraction module is 10kHz～30MHz.

If the test frequency is in the range of 10Hz to 1MHz, a low-frequency AC current measurement scheme is adopted. The core of the scheme is to use a high-permeability magnetic ring to make a current transformer. The magnetic core of the magnetic ring can be Permalloy, not High magnetic permeability materials such as crystalline and nanocrystalline. This application needs to detect a superimposed small-amplitude AC current (milliamp level and above) on a large-scale DC bias current (50 amps and above), so in order to prevent the magnetic core from magnetic saturation, the module’s In addition to the secondary induction winding, the current transformer also has a DC compensating winding to offset the magnetic field strength generated in the transformer by the DC component in the power bus current. As shown in Figure 9, it is a structure diagram of the current phasor extraction module at the low-frequency test frequency point. The low-frequency test frequency current phasor extraction module includes a current transformer made of a high-permeability magnetic ring. The current transformer is respectively wound with a secondary induction winding and a DC compensation winding. The secondary induction winding is connected to the current-voltage converter in turn. Circuit and signal conditioning and frequency compensation circuit, the signal conditioning and frequency compensation circuit is connected to the current input terminal I of the frequency sweep phasor analysis module, the role of the secondary induction winding is to induce the AC current component in the measured current, the secondary induction winding The current in the power bus has a linear relationship with the AC current in the power bus. After current-voltage conversion, signal conditioning and frequency response compensation circuit, it is finally output to the frequency sweep phasor analysis module; the DC compensation winding is connected in sequence through the DC circuit drive circuit and The low-pass filter circuit is connected to the DC current measurement device, and the DC current measurement device converts the measured bus current signal into a voltage signal, and after filtering out the AC component through the low-pass filter circuit, the DC circuit drive circuit outputs an energy to the DC compensation winding. The DC current that offsets the magnetic induction intensity generated by the DC current of the power bus bar in the current transformer; the function of the DC compensation winding is to provide it with a certain amount of DC current, and the magnetic induction intensity it generates in the magnetic core is the same as the measured The magnetic induction intensity generated by the DC bias current of the bus current in the magnetic core is equal in magnitude and opposite in direction, so as to ensure that the magnetic core will not be saturated due to excessive DC bias and ensure the normal operation of the current transformer. To realize the function of measuring the DC current of the power bus, you can use Hall current sensors or other types of devices that can convert DC current into DC voltage. The voltage output by the Hall current sensor includes a DC component that is proportional to the DC bias current of the bus. It also includes some small AC components; the output of the Hall current sensor filters out the AC components in the test frequency band through a low-pass filter, and the remaining approximate DC signal is given to the DC current drive circuit, and the DC current drive circuit uses this signal to Drive a DC compensation current to the DC compensation winding of the current transformer to offset the magnetic induction intensity generated by the DC of the power bus in the current transformer.

If the frequency of the test point is in the range of 10kHz to 30MHz, a high-frequency AC current measurement scheme can be used. This scheme can use ferrite, sendust and other magnetic cores with relatively low magnetic permeability and wide frequency response range to make current Transformer. Experiments show that choosing the appropriate magnetic core, the number of turns of the secondary winding, and the DC bias of the power bus current have little effect on the measurement of the AC current component of the current transformer, and the DC compensation winding like the low-frequency current test may not be needed. As shown in Figure 10, it is a structure diagram of the current phasor extraction module at the high-frequency test frequency point. The high-frequency test frequency current phasor extraction module includes a current transformer made of a magnetic ring with low magnetic permeability. The current transformer is wound with a secondary induction winding, and the secondary induction winding is connected to the current-voltage conversion circuit and signal conditioning in turn. and a frequency compensation circuit, and the signal conditioning and frequency compensation circuit is connected to the current input terminal of the frequency-sweeping phasor analysis module.

As shown in Figure 11, it is a structure diagram of a small current excitation load module. The small current excitation load module includes a negative feedback closed-loop control and drive circuit composed of an operational amplifier A, a field effect transistor Q, and a sampling resistor R1. The positive input terminal of the operational amplifier A is connected to the signal output terminal of the sweep frequency phasor analysis module through an adder S and the modulus value circuit, the output terminal of the operational amplifier A is connected to the control pole of the field effect transistor Q, one output pole of the field effect transistor Q is connected to the positive pole of the measured power supply through the current limiting and fuse protection circuit, and the other output pole is passed through the sampling resistor R1 is connected to the negative pole of the power supply under test. The main function of the small current excitation load module is to output a small-amplitude current with controllable frequency and amplitude. The current excitation is a passive sink mode, which will not cause potential damage to the power bus. Low Current Excitation Load Module The applied excitation should be small enough not to affect the operating point established by the source and load. The frequency-sweeping phasor analysis module inputs a sinusoidal signal at the test frequency point, and adds it to the original signal through the modulus circuit to obtain a voltage control signal with a DC bias, whose minimum value is slightly greater than zero; through the operational amplifier A, The control of the negative feedback closed-loop system composed of the field effect transistor Q and the sampling resistor S1 makes the voltage waveform on the sampling resistor S1 the same as _VC , so the power supply outputs the same current waveform as _VC .

As shown in Figure 12, it is a structural diagram of the frequency sweep phasor analysis module. The frequency-sweeping phasor analysis module includes digital logic devices, the test frequency point voltage phasor extraction module and the test frequency point current phasor extraction module are respectively connected to the digital logic devices through the input signal conditioning circuit and the analog-to-digital conversion circuit in turn, and the digital logic devices are sequentially passed through The digital-to-analog conversion circuit and the output signal conditioning circuit are connected to the small current excitation load module or the open circuit/short circuit/load calibration excitation signal output module; the phasors output by the test frequency point voltage phasor extraction module and the test frequency point current phasor extraction module are respectively passed through The input signal conditioning circuit adjusts to a suitable range, converts it into a digital signal through a high-speed analog-to-digital conversion circuit (AD), and inputs it to a digital logic device such as FPGA or DSP that can process digital signals at a high speed; the digital logic device includes a DDS connected to a clock chip Direct digital frequency synthesis unit, the DDS direct digital frequency synthesis unit in the digital logic device can output two orthogonal signals with frequency ω, expressed as sin(ωt) and cos(ωt); DDS direct digital frequency synthesis The unit is connected to the sine integration module and the cosine integration module respectively through the multiplier, and the two quadrature signals sin(ωt) and cos(ωt) with frequency ω output by the DDS direct digital frequency synthesis unit are respectively compared with the voltage input to the digital logic device The digital signal U(t) and the current digital signal I(t) are multiplied by the multiplier and then sent to the sine integration module and the cosine integration module respectively, and the sine integration module and the cosine integration module are connected to the phasor division operation module, U(t) and I(t) are multiplied by sin(ωt) and cos(ωt) respectively, and then multi-period integration is performed to obtain: I1=∫U(t)*cos(ωt)dt; Q1=∫U(t)* sin(ωt)dt; I2=∫I(t)*cos(ωt)dt; Q2=∫I(t)*sin(ωt)dt,

From this, the voltage phasor and current phasor (I1+jQ1) and (I2+jQ2) represented by the complex number with a frequency of ω can be extracted. After complex number division, the modulus ratio |Z| and the angle difference θ ; The phasor division operation module is connected with the control computer through the communication interface, and outputs the calculation result to the control computer for storage and post-processing; The sin(ωt) signal or cos(ωt) signal with a frequency of ω is output to the digital-to-analog conversion circuit, and through the output signal conditioning circuit, it is used as the signal output source of the signal output terminal S of the frequency sweep phasor analysis module; DDS direct digital frequency The synthesis unit is connected with the control computer through the communication interface, and the control computer controls the output frequency of the DDS direct digital frequency synthesis unit.

The DC power supply output impedance measurement method of the present invention realizes that, for a pair of measured objects composed of a DC power supply and a load, the measured DC power supply output impedance is defined at a specific operating point (a determination that the power supply operates within the rated range) DC voltage and DC current), the specific test section, and the equivalent impedance presented from the test section towards the power supply, effectively overcome the systematic deviation of the measurement process caused by the influence of the load input impedance. The measurement method of the present invention is that, at the working point established between the power supply under test and the load, a test section is selected on the power bus connected between the power supply under test and the load, and the test section is between the power supply under test and the load toward the power supply. In the cross-section viewed from the direction, a sinusoidal signal with a certain amplitude and frequency ω is output through the signal output terminal of the sweep frequency phasor analysis module to the small current excitation load module as an excitation, so that the small current excitation load module is introduced into the load end of the power supply under test. A sine wave current load with a frequency of ω, this sine wave current load is equivalent to bringing a small power controllable resistor to the power supply, drawing current from the power supply to achieve the purpose of disturbing the power supply; by testing the frequency point voltage phasor The extraction module extracts the amplitude and phase of the voltage signal with frequency ω at both ends of the power supply under test from the voltage sampling terminal on the test section, and the current phasor extraction module extracts from the power bus through the test frequency point The frequency flowing to the power supply under test through the test section The amplitude and phase of the current signal with ω are respectively sent to the voltage input terminal and current input terminal of the frequency sweep phasor analysis module; the frequency sweep phasor analysis module extracts the voltage phasor and current with frequency ω represented by a complex number Phasor, after the operation of complex number division, calculate the ratio and angle difference of the modulus of the voltage phasor and current phasor; then correct the measurement results according to the open circuit, short circuit and load calibration data at frequency ω, and finally get The amplitude value and phase value of the output impedance of the measured power supply at the frequency ω in the test section; the control computer communicates with the frequency sweep phasor analysis module through the communication interface, and controls the output frequency ω of the frequency sweep phasor analysis module , receiving the output result of the swept frequency phasor analysis module for storage and post-processing.

The step of correcting the measurement results according to the data of open circuit, short circuit and load calibration at frequency ω includes: 1) Disconnecting the power supply and the load under test from the power bus, and simultaneously driving the load module with a small current from the power bus 2) Output the excitation signal to the test section through the open circuit/short circuit/load calibration excitation signal output module connected to the load terminal; 3) When the voltage sampling terminals of the test section are kept open circuit, short circuit, and connected to the standard load, respectively measure 4) According to these data, correct the measurement results of the output impedance of the power supply under test.

The formula for correcting the measurement results through the measurement data of open circuit and short circuit is

${\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; om</span>}}\frac{{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; sm</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; xm</span>}}}{{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; xm</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; Z</span>}}_{\mathrm{<span\; class="notranslate">\; om</span>}}}$

Z _xm is the actual measured value of the measured object; Z _om is the measured value when the voltage sampling end of the test section is kept open; Z _sm is the measured value when the voltage sampling end of the test section is kept short-circuited; Z _x is the corrected measured value the impedance value of the object;

The method of correcting the measurement results by connecting the measurement data of the standard load is: the actual measured value of the standard load at each frequency point measured when the voltage sampling end of the test section is connected to the standard load is compared with the nominal value of each frequency point of the standard load By comparison, a correction factor is obtained, which makes the final displayed impedance value consistent with the nominal value of the standard load when measuring the standard load, and the subsequent measured values are corrected according to this correction factor.

It should be pointed out that the specific embodiments described above can enable those skilled in the art to understand the invention more comprehensively, but do not limit the invention in any way. Therefore, although the description and examples have described the invention in detail, those skilled in the art should understand that the invention can still be modified or equivalently replaced; and all technologies that do not depart from the spirit and scope of the invention The scheme and its improvement are all included in the protection scope of the invention patent.

Claims (9)

1. a direct supply output impedance measurement mechanism, is characterized in that, comprises test frequency voltage phasor extraction module, test frequency electric current phasor extraction module, small area analysis excitation load blocks, frequency sweep phasor analysis module and computer for controlling; Described test frequency voltage phasor extraction module is connected voltage input end and the current input terminal of frequency sweep phasor analysis module respectively with test frequency electric current phasor extraction module, the signal output part of described frequency sweep phasor analysis module connects small area analysis excitation load blocks, and described frequency sweep phasor analysis module is also connected with computer for controlling; described test frequency voltage phasor extraction module is connected to the voltage sample end connecting the testing section that the power source bus of load is chosen at tested power supply, extract amplitude and phase place that tested both ends of power frequency is the voltage signal of ω, described testing section is towards the square section that power supply direction is seen between tested power supply and load, described test frequency electric current phasor extraction module adopts cordless to extract from power source bus amplitude and the phase place that the frequency flowing to tested power supply by testing section is the current signal of ω, described small area analysis excitation load blocks is connected to the load end of tested power supply, the frequency being exported certain amplitude by described frequency sweep phasor analysis module is the sinusoidal excitation signal of ω, introduce one at the load end of tested power supply and the sine-wave current load that the frequency of disturbance is ω is applied to power supply, described frequency sweep phasor analysis module is according to the amplitude of voltage signal received and the amplitude of phase place and current signal and phase place, calculate the tested power supply of described testing section in frequencies omega time the range value of output impedance and phase value, computer for controlling controls the output frequency ω of frequency sweep phasor analysis module and the result of calculation of receiving frequency-sweeping phasor analysis module carries out storing and post-processed,

Described frequency sweep phasor analysis module comprises digital logic device, described test frequency voltage phasor extraction module is connected described digital logic device by input signal conditioning circuit with analog to digital conversion circuit respectively successively with test frequency electric current phasor extraction module, and described digital logic device is connected described small area analysis excitation load blocks by D/A converting circuit with output signal conditioning circuit successively, described digital logic device comprises the DDS direct digital frequency synthesier unit be connected with clock chip, described DDS direct digital frequency synthesier unit connects sine integral module and integral cosine module respectively by multiplier, the two-way frequency that DDS direct digital frequency synthesier unit exports is send into sine integral module and integral cosine module respectively again after the orthogonal signal sin (ω t) of ω is multiplied with current digital signal I (t) with voltage digital signal U (t) inputing to digital logic device respectively with cos (ω t), described sine integral module and integral cosine model calling phasor division arithmetic module, described phasor division arithmetic module is connected with computer for controlling by communication interface, described DDS direct digital frequency synthesier unit also connects described D/A converting circuit, is that sin (ω t) signal or cos (ω t) signal of ω exports to D/A converting circuit by the frequency of generation, described DDS direct digital frequency synthesier unit is connected with computer for controlling by communication interface, by the output frequency of computer for controlling control DDS direct digital frequency synthesier unit.

2. direct supply output impedance measurement mechanism according to claim 1, it is characterized in that, the signal output part of described frequency sweep phasor analysis module also connects open circuit/short circuit/load calibration pumping signal output module, described open circuit/short circuit/load calibration pumping signal output module carrying out opening a way/short circuit/load calibration time be connected to load end, in tested power supply and load and small area analysis excitation load blocks all from output drive signal after power source bus disconnects to testing section; Described open circuit/short circuit/load calibration pumping signal output module comprises negative feedback operational amplifier; the positive input terminal of operational amplifier connects signal output part and the delivery value of frequency sweep phasor analysis module by totalizer and adds DC bias circuit; the output terminal series diode of operational amplifier; the electrode input end of diode connects pressure limited protection circuit, and the cathode output end of diode passes through the voltage sample end in calibration switch connecting test cross section.

3. direct supply output impedance measurement mechanism according to claim 1 and 2, it is characterized in that, described test frequency voltage phasor extraction module comprises the first capacitance and the second capacitance that are connected with testing section voltage sample end, first capacitance and the second capacitance are connected the first signal input buffer circuit and secondary signal input buffer circuit respectively, first signal input buffer circuit is connected differential amplifier circuit again with secondary signal input buffer circuit simultaneously, and differential amplifier circuit connects the voltage input end of frequency sweep phasor analysis module.

4. direct supply output impedance measurement mechanism according to claim 1 and 2, it is characterized in that, described test frequency electric current phasor extraction module comprises low-frequency test frequency electric current phasor extraction module, described low-frequency test frequency electric current phasor extraction module comprises a current transformer made by the magnet ring of high magnetic permeability, described current transformer is wound with respectively secondary induction winding and direct current setoff winding, described secondary induction winding connects current-to-voltage converting circuit and signal condition and frequency compensated circuit successively, signal condition and frequency compensated circuit connect the current input terminal of frequency sweep phasor analysis module, described direct current compensates for winding and is connected DC current measurement device by the DC circuit driving circuit connected successively with low-pass filter circuit, described DC current measurement device converts voltage signal to the bus current signal recorded, after low-pass filter circuit filtering alternating component, then compensate for the DC current that winding exports the magnetic induction density that a DC current offsetting power source bus produces in current transformer to direct current by DC circuit driving circuit.

5. direct supply output impedance measurement mechanism according to claim 1 and 2, it is characterized in that, described test frequency electric current phasor extraction module comprises high-frequency test frequency electric current phasor extraction module, described high-frequency test frequency electric current phasor extraction module comprises a current transformer made by the magnet ring of low magnetic permeability, described current transformer is wound with secondary induction winding, described secondary induction winding connects current-to-voltage converting circuit and signal condition and frequency compensated circuit successively, signal condition and frequency compensated circuit connect the current input terminal of frequency sweep phasor analysis module.

6. direct supply output impedance measurement mechanism according to claim 2, it is characterized in that, the digital logic device of described frequency sweep phasor analysis module is connected described open circuit/short circuit/load calibration pumping signal output module by D/A converting circuit with output signal conditioning circuit successively.

7. a direct supply output impedance measuring method, it is characterized in that, set up the working point of tested power supply and load, the power source bus that tested power supply is connected with load chooses testing section, described testing section is towards the square section that power supply direction is seen between tested power supply and load, the sinusoidal signal being ω by the frequency of the output terminal output certain amplitude of frequency sweep phasor analysis module encourages load blocks as excitation to small area analysis, make small area analysis encourage load blocks to introduce one at the load end of tested power supply and the sine-wave current load that the frequency of disturbance is ω is applied to power supply, be amplitude and the phase place of the voltage signal of ω from the frequency that the voltage sample end testing section extracts tested both ends of power by test frequency voltage phasor extraction module, extract from power source bus amplitude and the phase place that the frequency flowing to tested power supply by testing section is the current signal of ω by test frequency electric current phasor extraction module, be sent to voltage input end and the current input terminal of frequency sweep phasor analysis module respectively, ratio and the differential seat angle of the mould of voltage phasor and electric current phasor is calculated by frequency sweep phasor analysis module, according to the data at the open circuit of frequencies omega, short circuit, load calibration, measurement result is revised again, finally draw the tested power supply of described testing section in frequencies omega time the range value of output impedance and phase value, computer for controlling is communicated with frequency sweep phasor analysis module by communication interface, and control the output frequency ω of frequency sweep phasor analysis module, the Output rusults of receiving frequency-sweeping phasor analysis module carries out storing and post-processed.

8. direct supply output impedance measuring method according to claim 7, is characterized in that, described basis comprises the step that measurement result is revised in the data of the open circuit of frequencies omega, short circuit, load calibration:

1) tested power supply and load are all disconnected from power source bus, encourage load blocks to disconnect from power source bus small area analysis simultaneously; 2) by being connected to the open circuit/short circuit/load calibration pumping signal output module output drive signal of load end to testing section; 3) when the voltage sample end of testing section keeps open circuit, short circuit, connection standard load respectively, resistance value when open circuit, short circuit, connection standard load is measured respectively; 4) according to these data, the measurement result of tested power supply output impedance is revised.

9. direct supply output impedance measuring method according to claim 8, is characterized in that, by the measurement data of open circuit, short circuit to the formula that measurement result is revised is

$Z_x=Z_{\mathrm{om}}\frac{Z_{\mathrm{sm}}-Z_{\mathrm{xm}}}{Z_{\mathrm{xm}}-Z_{\mathrm{om}}}$

Z _xmfor the measured value of measurand; Z _omvoltage sample end for testing section keeps measured value during open circuit; Z _smvoltage sample end for testing section keeps measured value during short circuit; Z _xfor the resistance value of revised measurand.