A low-frequency high-precision conducted injection voltage real-time monitoring method and system

Abstract

The application provides a low-frequency high-precision conducted injection voltage real-time monitoring method and system, adopts a high-pass filter to effectively filter out the power supply voltage in the test process, improves the test safety, collects low-frequency injection voltage signals through a high-precision high-sampling-rate voltage sampling module to obtain time-domain data, obtains frequency-domain data after processing, improves the dynamic range of the test system, and realizes the function of quickly and accurately testing a small signal superimposed on an alternating current signal when a low-frequency injection interference test is performed on an alternating current power supply system. The application is suitable for testing a wide-band small signal in various alternating current and direct current power supply systems, the test system has a low frequency, the acquisition card can be used to complete the collection of low-frequency voltage signals, a high-sampling-rate high-bandwidth oscilloscope is not needed to collect signals, the requirement for the oscilloscope is greatly reduced, the cost is effectively reduced, the test system is miniaturized, and the electromagnetic compatibility standard examination test is easily completed.

Description

Technical Field

[0001] This invention belongs to the field of electromagnetic compatibility testing technology, specifically relating to a method and system for real-time monitoring of low-frequency, high-precision conducted injection voltage. Background Technology

[0002] In electromagnetic compatibility (EMC) testing, the low-frequency conducted injection susceptibility test is one of the most commonly used assessment items in the field, typically covering a frequency range of 25Hz-150kHz. This test verifies the EUT's ability to withstand signals coupled to the input power line. Before testing, the test system must be calibrated under a purely resistive load to obtain a set of output power calibration values. During the test, the signal level is injected according to the lower of the voltage limit required in the standard and the power value obtained during calibration. When the EUT is AC powered, the power supply in the AC power supply system is typically 220V or 380V, and the injected interference signal will be superimposed on the AC power supply signal. According to the test standard requirements, the injected signal needs to be monitored in real time during the test. GJB151B-2013 specifies an injection voltage of 67mV (i.e., 96.5dBuV) at 150kHz. Figure 5 The oscilloscopes commonly used for this project are 8-bit or 12-bit precision. When measuring a 220V supply voltage signal, the smallest signal that the oscilloscope can resolve is approximately 50mV; when measuring a 380V supply voltage signal, the smallest signal that the oscilloscope can resolve is approximately 93mV. Since the smallest resolvable signal is close to or even exceeds the required test signal, testing this small signal on an AC power supply line will produce significant errors, or even fail to measure the required small signal. Increasing the oscilloscope precision would result in a substantial increase in testing costs.

[0003] In practical testing, when testing small signals superimposed on large AC signals, the magnitude of the small signal cannot be directly obtained using an oscilloscope. A common method is to use the oscilloscope's FFT function for small signal testing. However, due to limitations in testing accuracy, this often fails to accurately detect the injected interference signal. Therefore, new testing methods are needed to avoid these problems. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method and system for real-time monitoring of low-frequency, high-precision conducted injection voltage, which is used to quickly and accurately test small signals superimposed on AC signals.

[0005] The technical solution adopted by this invention to solve the above-mentioned technical problems is as follows: a method for real-time monitoring of low-frequency, high-precision conduction injection voltage, comprising the following steps:

[0006] S1: Design a high-pass filter to filter out the power supply voltage signal of the EUT during the test; fit the frequency response curve of the high-pass filter to the voltage limit of the national standard CS101 so that the injected voltage remains a flat monitoring value within the test frequency band.

[0007] S2: Calibrate the frequency response parameters of the high-pass filter;

[0008] S3: Design a high-precision, high-sampling-rate voltage sampling module to acquire low-frequency injected voltage signals and convert the acquired time-domain signals into frequency-domain signals;

[0009] S4: Connect the first and second input terminals of the high-pass filter to the power supply terminal of the EUT (Equipment Under Test) respectively; connect the output terminal of the high-pass filter to the signal input terminal of the voltage sampling module through an RF coaxial connector and a coaxial cable; connect the coupling transformer, power amplifier, and signal generator sequentially to the power supply circuit of the EUT.

[0010] S5: Store and analyze the real-time time-domain signal acquired by the voltage sampling module, and perform FFT to convert the time-domain signal into a frequency-domain signal. Compare the frequency-domain data with the injection limit required by the test standard to achieve the closed-loop test requirements.

[0011] According to the above scheme, the specific steps in step S2 are as follows:

[0012] S21: Connect the signal output terminal of the signal generator to the first and second input terminals of the high-pass filter respectively, connect the high-impedance voltage probe of the oscilloscope to the first and second input terminals of the high-pass filter respectively, and connect the output terminal of the high-pass filter to the test receiver through the RF coaxial connector and the coaxial line.

[0013] S22: Select an appropriate output amplitude for the signal generator, and adjust the signal frequency from the low-frequency band to the high-frequency band in certain steps. Record the oscilloscope reading and the receiver reading at each frequency point. Let the frequency response parameter of the high-pass filter be k, in dB; and the oscilloscope reading be U. OSC The unit is V; the reading on the test receiver is U. rec The unit is dBuV. The frequency response parameter k of the high-pass filter is calculated using the following formula:

[0014]

[0015] A low-frequency, high-precision real-time monitoring system for conducted injection voltage includes a high-pass filter, a voltage sampling module, a coupling transformer, a power amplifier, and a signal generator. The first and second input terminals of the high-pass filter are respectively connected to the power supply terminals of the EUT (Equipment Under Test) to filter out the power supply voltage signal of the EUT during the test. The signal input terminal of the voltage sampling module is connected to the output terminal of the high-pass filter through an RF coaxial connector and a coaxial line to acquire the low-frequency injected voltage signal and convert the acquired time-domain signal into a frequency-domain signal. The coupling transformer, power amplifier, and signal generator are sequentially connected to the power supply circuit of the EUT.

[0016] Furthermore, the first and second input terminals of the high-pass filter are test clips, and the output terminal of the high-pass filter is an RF coaxial connector.

[0017] Furthermore, the input impedance of the high-pass filter is high in the frequency range of 20Hz to 150kHz.

[0018] Furthermore, the voltage sampling module uses a sampling chip with a vertical resolution of 16 bits, a sampling rate higher than 10Msa / s, and FFT functionality.

[0019] The beneficial effects of this invention are as follows:

[0020] 1. The present invention provides a method and system for real-time monitoring of low-frequency high-precision conducted injection voltage. It employs a high-pass filter to effectively filter out the power supply voltage during the testing process, improving test safety. A high-precision, high-sampling-rate voltage sampling module acquires low-frequency injected voltage signals to obtain time-domain data, which is then processed to obtain frequency-domain data, improving the dynamic range of the test system. It enables rapid and accurate testing of small signals superimposed on AC signals during low-frequency injection interference tests in AC power supply systems.

[0021] 2. This invention is applicable to wide-band small-signal testing in various AC / DC power supply systems. Since the test system has a low frequency, the low-frequency voltage signal can be acquired using a data acquisition card, eliminating the need for a high sampling rate, high bandwidth oscilloscope. This greatly reduces the requirements for the oscilloscope, effectively lowers the cost, facilitates the miniaturization of the test system, and makes it easier to complete electromagnetic compatibility standard assessment tests. Attached Figure Description

[0022] Figure 1 This is a frequency response curve of a high-pass filter according to an embodiment of the present invention.

[0023] Figure 2 This is a schematic diagram of a high-pass filter according to an embodiment of the present invention.

[0024] Figure 3 This is a block diagram of the frequency response calibration of a high-pass filter according to an embodiment of the present invention.

[0025] Figure 4 This is a principle block diagram of an embodiment of the present invention.

[0026] Figure 5 This is a voltage limit curve of CS101 according to an embodiment of the present invention. Detailed Implementation

[0027] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0028] See Figure 4 The embodiments of the present invention include an audio power amplifier, an injection coupling transformer, a high-pass filter, and a voltage sampling module;

[0029] A method for real-time monitoring of low-frequency, high-precision conduction injection voltage according to an embodiment of the present invention includes the following steps:

[0030] S1: Design a high-pass filter, and calculate the frequency response curve of the high-pass filter (see...). Figure 1 ) and the CS101 voltage limit in GJB151B (see Figure 5 After fitting, the monitored injection voltage is kept relatively flat within the required test frequency range. The high-pass filter has a high input impedance between 20Hz and 150kHz. Two test terminals are led out from the filter input, which are connected to the EUT power supply via test clips. The filter output is an RF coaxial connector. Figure 2 As shown.

[0031] High-pass filters are used to filter out the EUT power supply voltage signal during the testing process (typically, the EUT AC power supply signal frequency is 50Hz, and 400Hz is more commonly used in the aerospace field). After filtering out the EUT power supply signal, the power supply signal is attenuated to the millivolt level, which greatly reduces the complexity of the entire monitoring system and improves test safety.

[0032] S2: Calibrate the frequency response parameters of the high-pass filter. The calibration block diagram is as follows: Figure 3 .

[0033] The signal generator is connected to the input of the high-pass filter via a cable. At the same time, the input signal is monitored by a high-impedance voltage probe connected to the oscilloscope. The RF coaxial interface of the output of the high-pass filter is connected to the test receiver. The signal generator is selected with an appropriate output amplitude, and the frequency is adjusted from the low frequency band to the high frequency band in a certain step. The readings of the oscilloscope and the test receiver are recorded at each frequency point. The frequency response parameter of the high-pass filter, i.e., the coefficient k, can be obtained by formula (1).

[0034]

[0035] Where: k is the high-pass filter coefficient, in dB; U OSC U represents the oscilloscope reading, measured in volts (V). rec The readings are for testing the receiver, and the unit is dBuV.

[0036] S3: Design a high-precision, high-sampling-rate voltage sampling module to acquire low-frequency injected voltage signals; the high-precision data acquisition module uses a chip with a vertical resolution of 16 bits and a sampling rate higher than 10Msa / s to meet the testing requirements of this system. The high-precision data acquisition module has an FFT function to convert the acquired time-domain signal into a frequency-domain signal.

[0037] S4: The software stores and analyzes the real-time time-domain data obtained by the voltage acquisition system, and performs FFT on the time-domain data to finally obtain the frequency-domain data. The frequency-domain data is then compared with the injection limits required by the test standard to achieve the closed-loop test requirements.

[0038] The above embodiments are only used to illustrate the design concept and features of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. The protection scope of the present invention is not limited to the above embodiments. Therefore, all equivalent changes or modifications made based on the principles and design ideas disclosed in the present invention are within the protection scope of the present invention.

Claims

1. A method for real-time monitoring of low-frequency, high-precision conducted injection voltage, characterized in that: Includes the following steps: S1: Design a high-pass filter to filter out the power supply voltage signal of the EUT during the test; fit the frequency response curve of the high-pass filter to the voltage limit of the national standard CS101 so that the injected voltage remains a flat monitoring value within the test frequency band. S2: Calibrate the frequency response parameters of the high-pass filter; the specific steps are as follows: S21: Connect the signal output terminal of the signal generator to the first and second input terminals of the high-pass filter respectively, connect the high-impedance voltage probe of the oscilloscope to the first and second input terminals of the high-pass filter respectively, and connect the output terminal of the high-pass filter to the test receiver through the RF coaxial connector and the coaxial line. S22: Select an appropriate output amplitude for the signal generator, and adjust the signal frequency from the low-frequency band to the high-frequency band in certain steps. Record the oscilloscope reading and the receiver reading at each frequency point. Let the frequency response parameter of the high-pass filter be k, in dB; and the oscilloscope reading be U. OSC The unit is V; The reading on the test receiver is U rec The unit is dBuV. The frequency response parameter k of the high-pass filter is calculated using the following formula: ； S3: Design a high-precision, high-sampling-rate voltage sampling module to acquire low-frequency injected voltage signals and convert the acquired time-domain signals into frequency-domain signals; S4: Connect the first and second input terminals of the high-pass filter to the power supply terminal of the EUT (Equipment Under Test) respectively; connect the output terminal of the high-pass filter to the signal input terminal of the voltage sampling module through an RF coaxial connector and a coaxial cable; connect the coupling transformer, power amplifier, and signal generator sequentially to the power supply circuit of the EUT. S5: Store and analyze the real-time time-domain signal acquired by the voltage sampling module, and perform FFT to convert the time-domain signal into a frequency-domain signal. Compare the frequency-domain data with the injection limit required by the test standard to achieve the closed-loop test requirements.

2. A monitoring system for the low-frequency high-precision conduction injection voltage real-time monitoring method according to claim 1, characterized in that: Includes a high-pass filter, voltage sampling module, coupling transformer, power amplifier, and signal generator; The first and second input terminals of the high-pass filter are respectively connected to the power supply terminals of the EUT (Electronic Under Test) device to filter out the power supply voltage signal of the EUT device during the test. The signal input terminal of the voltage sampling module is connected to the output terminal of the high-pass filter through an RF coaxial connector and a coaxial line. It is used to acquire low-frequency injected voltage signals and convert the acquired time-domain signals into frequency-domain signals. The coupling transformer, power amplifier, and signal generator are connected in sequence to the power supply circuit of the EUT (Equipment Under Test).

3. The monitoring system according to claim 2, characterized in that: The first and second input terminals of the high-pass filter are test clips, and the output terminal of the high-pass filter is an RF coaxial connector.

4. The monitoring system according to claim 2, characterized in that: The input impedance of a high-pass filter is high in the frequency range of 20Hz to 150kHz.

5. The monitoring system according to claim 2, characterized in that: The voltage sampling module uses a sampling chip with a vertical resolution of 16 bits, a sampling rate of more than 10Msa / s, and FFT functionality.

Images