A method for evaluating the magnetic field immunity of digital isolators

Abstract

This invention discloses a method for evaluating the magnetic field immunity of a digital isolator: S1: Obtain magnetic field immunity test data for the digital isolator. The input signal of the isolator uses a square wave with a duty cycle of 50% and a level of 0-5.0V; S2: Determine the failure criteria, including two failure modes: level fluctuation exceeding the limit and level fixed 0 / 1. For level fluctuation exceeding the limit, the failure thresholds are set as follows: high level below 0.7·VH and low level above 0.3·(VH-VL)+VL. For level fixed 0 / 1 failure, the failure threshold is set as follows: level length L(0 / 1) ≥ λ; S3: Determine the frequency range in which the device is sensitive to radiation. This frequency range covers the peak value of level fluctuation exceeding the limit and the level fixed 0 / 1 failure portion; S4: Generate a device failure analysis diagram corresponding to the two failure modes, including the failure state, failure peak frequency, frequency-corresponding level fluctuation, and failure-sensitive frequency; S5: Determine the rating criteria: Level A: The device performs its function normally. Level B: The device is interfered with but has not reached a failure state. Level C: Partial functional failure of the device occurs, but the interference decreases as the interference load decreases. Level D: The device has experienced a persistent functional failure, but can be restored through simple operation or cooling after the interference load is removed. Level E: The device has experienced a permanent functional failure; S6, evaluate the magnetic field immunity of the digital isolator, and the evaluation results include the sensitive frequency range, device failure analysis diagram, and device failure rating.

Description

(I) Technical Field:

[0001] This application relates to the field of magnetic field immunity evaluation technology, specifically a method for evaluating the magnetic field immunity of a digital isolator. (II) Background Technology:

[0002] Digital magnetic coupling isolators achieve digital signal transmission and isolation based on the principle of magnetic field coupling, providing excellent resistive isolation in circuits. However, due to the nature of magnetic coupling, in applications near high-power power supplies, motors, and in space, the device is prone to coupling voltage caused by electromagnetic coupling under strong magnetic field interference, leading to transmission instability and failure. Therefore, it is crucial to test and evaluate the magnetic field immunity of digital magnetic coupling isolators.

[0003] Current methods for evaluating the immunity of digital magnetic coupling isolators typically involve directly applying a magnetic field to the device using an excitation coil during testing, and using waveform errors transmitted by the device as the failure criterion. The test field strength is usually based on system-level EMC test strengths such as 100V / m, which is not entirely suitable for device-level EMC evaluation. The test frequency is usually a general frequency. Due to the lack of more suitable failure criteria and the inability to accurately measure the magnitude of the magnetic field, the measurement accuracy is very low, making it difficult to achieve the desired results in testing the magnetic field immunity of digital magnetic coupling isolators.

[0004] Currently, the relevant patented magnetic field immunity testing devices and methods for magnetically coupled digital isolators are measured using a TEM chamber. These methods include using an oscilloscope to measure the device's input and output, generating an RF field by connecting a DC power supply to a Helmholtz coil, and detecting the magnetic field using a gaussmeter. The test equipment system is described in detail, and the test process is clarified. However, the specific subsequent evaluation methods lack details, making it difficult to obtain more information on magnetic field immunity. There is still room for improvement in terms of guidance for application.

[0005] Currently, evaluation standards for the magnetic field immunity of digital magnetic couplers typically only include magnetic field strength values, failing to provide more information on magnetic field immunity and making it difficult to determine their suitability for use in various scenarios. There is also a lack of corresponding testing and evaluation methods for environmental magnetic field frequencies, sensitive frequencies, and level fluctuations.

[0006] Therefore, a method for evaluating the magnetic field immunity of digital isolators is needed. (III) Summary of the Invention:

[0007] 1. Purpose:

[0008] To meet the needs of the prior art, the present invention provides a method for evaluating the magnetic field immunity of digital isolators.

[0009] 2. Technical Solution:

[0010] To achieve the above objectives, this invention provides a method for evaluating the magnetic field immunity of a digital isolator, and generates corresponding immunity evaluation results.

[0011] Step 1: Obtain the magnetic field immunity test data of the digital isolator. The input signal of the isolator adopts a square wave with a duty cycle of 50% and a level of 0-5.0V.

[0012] Magnetic field strength gradient pre-test and formal step test. The pre-test process determines the test frequency and intensity range, and the field strength at the test location is calibrated using the four-point method. Frequency stepping is performed in 1MHz increments to obtain frequency failure conditions under the same field strength.

[0013] There are multiple failure modes in signal transmission. Among them, level fluctuation failure and fixed 0 / 1 failure are most affected by magnetic field interference, which may lead to errors in signal transmission.

[0014] Step 2: Determine the failure criteria, which include two failure modes: level fluctuation exceeding the limit and level fixed 0 / 1. For level fluctuation exceeding the limit, the failure thresholds are high level below 0.7·VH and low level above 0.3·(VH-VL)+VL. For level fixed 0 / 1 failure, the failure threshold is level length L(0 / 1)≥λ.

[0015] Digital isolators have multiple failure modes. During signal transmission, failures due to excessive level fluctuations and fixed 0 / 1 signals are most affected by magnetic field interference.

[0016] The failure thresholds for the output levels are set at 0.7 * VH for high level and 0.3 * (VH - VL) + VL for low level. The differences between the highest and lowest points of the output level and the standard values ​​under both high and low levels are recorded, using the volatility parameter for data recording. Volatility: α = V_b / VH, where V_b is the maximum voltage deviation and VH is the output high level. The volatility corresponding to each frequency point is recorded, and a volatility-frequency fluctuation curve is plotted. A level fluctuation exceeding the limit is considered a failure when the volatility exceeds 0.3.

[0017] For the fixed 0 / 1 level failure mode, an oscilloscope is used to capture and judge the signal. The high / low level is twice half a cycle as the trigger threshold for signal capture. When the oscilloscope captures a high / low level for a continuous length of 2 times or more half a cycle, it is determined to be a fixed 0 / 1 level failure.

[0018] Step 3: Determine the frequency range in which the device is sensitive to radiation. This frequency range covers the peak value of level fluctuation exceeding the limit and the part of the level that is fixed at 0 / 1 and fails.

[0019] Take the concentrated frequency range with the highest fluctuation rate in the level fluctuation failure, and take the range to include several peak points or only take a single set of peak points. Then take the frequency range where the level is fixed 0 / 1 failure. Take the intersection of the above regions and determine it as the sensitive frequency range.

[0020] Step 4: Generate device failure analysis diagrams corresponding to the two failure modes, including failure state, failure peak frequency, frequency-corresponding level fluctuation, and failure-sensitive frequency.

[0021] The device failure analysis graph uses RF interference frequency on the x-axis and failure status on the y-axis, respectively. Failure consists of two parts: level fluctuation exceeding limits and level fixed 0 / 1 failure. A failure threshold of 0.3 times the level fluctuation is used, corresponding to the failure threshold of level fixed 0 / 1 failure. The graph displays both failure modes and thresholds under the same field strength, and the sensitive frequency ranges are marked according to the strongest frequency of level fluctuation failure and level fixed 0 / 1 failure.

[0022] Step 5: Determine the rating criteria. Level A: The device functions normally. Level B: The device is affected by interference but has not reached a failure state. Level C: Partial functional failure of the device, but the interference decreases as the interference load decreases. Level D: Persistent functional failure of the device, but can be restored by simple operation or cooling after removing the interference load. Level E: Permanent functional failure of the device.

[0023] Step 6: Evaluate the magnetic field immunity of the digital isolator. The evaluation results include the sensitive frequency range, device failure analysis diagram, and device failure rating.

[0024] This invention also provides a method for evaluating the magnetic field immunity of a digital isolator, comprising:

[0025] S1: Obtain the magnetic field immunity test data of the digital isolator. The input signal of the isolator adopts a square wave with a duty cycle of 50% and a level of 0-5.0V.

[0026] S2: Determine the failure criteria, which include two failure modes: level fluctuation exceeding the limit and level fixed 0 / 1. For level fluctuation exceeding the limit, the failure threshold is set as high level below 0.7·VH and low level above 0.3·(VH-VL)+VL. For level fixed 0 / 1 failure, the failure threshold is set as level length L(0 / 1)≥λ.

[0027] S3: Determine the frequency range in which the device is sensitive to radiation, which covers the peak value of level fluctuation exceeding the limit and the failure part of level fixed 0 / 1;

[0028] S4: Generate device failure analysis diagrams corresponding to the two failure modes, including failure state, failure peak frequency, frequency-corresponding level fluctuation, and failure-sensitive frequency;

[0029] S5, Determine the rating criteria: A-level: The device performs its function normally. B-level: The device is affected by interference but has not reached a failure state. C-level: Partial functional failure of the device, but the interference decreases as the interference load decreases. D-level: Persistent functional failure of the device, but can be restored by simple operation or cooling after removing the interference load. E-level: Permanent functional failure of the device;

[0030] S6 evaluates the magnetic field immunity of the digital isolator. The evaluation results include the sensitive frequency range, device failure analysis diagram, and device failure rating.

[0031] 3. Advantages and effects:

[0032] The magnetic field immunity evaluation method for digital isolators of the present invention can effectively evaluate the magnetic field immunity of digital isolators, obtain the sensitive frequency of the isolator and two failure scenarios for each frequency, and present the magnetic field immunity characteristics of the device more completely. This is beneficial for strengthening the electromagnetic compatibility design of the device during application and reducing the impact of electromagnetic interference. (iv) Description of the attached drawings:

[0033] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0034] Figure 1 This is a diagram illustrating the method for evaluating the magnetic field immunity of digital isolators in this application;

[0035] Figure 2 This is an example diagram of level fluctuation failure in the digital isolator transmission failure criterion of this application;

[0036] Figure 3 This is an example diagram of a fixed 0 / 1 level failure in the digital isolator transmission failure criterion of this application;

[0037] Figure 4 This is a device failure analysis diagram of the digital isolator magnetic field immunity evaluation method of this application. (V) Specific Implementation Methods:

[0038] Many specific details are set forth in the following description to provide a full understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar extensions without departing from this application; therefore, this application is not limited to the specific embodiments disclosed below.

[0039] The device selected in this invention is an isolator, model GL1200P. The GL1200P isolator is a digital magnetic isolation circuit that integrates a transformer and encoding / decoding circuits into a single package. The device is packaged in an SOP8 plastic package. A detailed explanation of the magnetic field immunity evaluation method for a digital isolator described in this invention will be provided, using specific practical examples.

[0040] Step 1: Obtain the magnetic field immunity test data of the digital isolator. The input signal of the isolator adopts a square wave with a duty cycle of 50% and a level of 0-5.0V.

[0041] A test platform was set up for testing. After powering on the isolator, a square wave signal was input with a 50% duty cycle and a voltage level of 0-5.0V. With interference enabled, the output waveform was monitored and compared with the theoretical output waveform. Since the output waveform of this device was identical to the input waveform, the output could be directly compared with the input. Evaluation was then conducted based on the following two failure criteria.

[0042] Step 2: Determine the failure criteria, which include two failure modes: level fluctuation exceeding the limit and level fixed 0 / 1. For level fluctuation exceeding the limit, the failure thresholds are high level below 0.7·VH and low level above 0.3·(VH-VL)+VL. For level fixed 0 / 1 failure, the failure threshold is level length L(0 / 1)≥λ.

[0043] Digital isolators have multiple failure modes. During signal transmission, failures due to excessive level fluctuations and fixed 0 / 1 signals are most affected by magnetic field interference.

[0044] Analysis method for level fluctuation exceeding the limit failure mode: During frequency stepping, the output frequency is observed using an oscilloscope, and waveform data at each test frequency point is recorded. The difference between the highest and lowest points of the output level under high and low levels and the standard value is recorded separately. Data recording is performed using the parameter volatility: volatility: α = V_bVH, where V_b is the maximum voltage offset, and VH is the output high level. The resulting ratio is the volatility. The volatility corresponding to each frequency point is recorded, and a volatility versus frequency fluctuation curve is plotted. The failure thresholds for the level are set as 0.7·VH for high level and 0.3·(VH-VL)+VL for low level. When the volatility at any point reaches the failure threshold, it is considered that the signal distortion caused by the isolator during signal transmission will cause signal transmission errors, and this is judged as a level fluctuation exceeding the limit failure. In this evaluation process, the theoretical output VL is 0V. The failure thresholds are taken as 0.7VH for high level and 0.3VH for low level. That is, when the fluctuation rate reaches 0.3 at any point, the signal distortion caused by the isolator in transmitting the signal is considered to cause the signal transmission error, and it is judged as a failure due to excessive level fluctuation.

[0045] Example, refer to Figure 3Determine the fluctuation range and the output level. Compare the actual level with the output level to quantify the level fluctuation and calculate the fluctuation rate. Record the frequency fluctuation at that point.

[0046] Analysis method for fixed 0 / 1 level failure mode: Use an oscilloscope to capture and judge, and use twice half a cycle of high / low level as the trigger threshold for signal capture. When the device experiences fixed 0 / 1 level failure, the oscilloscope will capture high / low level for two or more consecutive half cycles. At this time, it is judged as fixed 0 / 1 level failure. When this situation occurs, it will cause the transmitted signal to be completely wrong.

[0047] Example, refer to Figure 3 When the output waveform deviates from the theoretical fluctuation, it is determined whether a failure has occurred where the level is fixed at 0 / 1.

[0048] Step 3: Determine the frequency range in which the device is sensitive to radiation. This frequency range covers the peak value of level fluctuation exceeding the limit and the part of the level that is fixed at 0 / 1 and fails.

[0049] Take the frequency range with the highest fluctuation rate in the level fluctuation failure, and then take the frequency range where the level is fixed at 0 / 1 failure. The intersection of the above regions is determined as the sensitive frequency range.

[0050] Step 4: Generate device failure analysis diagrams corresponding to the two failure modes, including failure state, failure peak frequency, frequency-corresponding level fluctuation, and failure-sensitive frequency.

[0051] The device failure analysis diagram consists of two parts: level fluctuation exceeding the limit failure and level fixed 0 / 1 failure. A level fluctuation rate of 0.3 is used as the failure threshold to distinguish between failure and normal areas, and the failure boundary of level fixed 0 / 1 failure is also marked. The same diagram displays the failure areas corresponding to the two failure modes under the same field strength, thus showing the device's magnetic field immunity failure information in a single diagram. The diagram also marks the failure-sensitive frequency range: the frequency corresponding to the maximum level fluctuation rate and the occurrence of level fixed 0 / 1 failure. The parameters used for evaluation include: magnetic field strength, frequency, and sensitive frequency range.

[0052] Based on the evaluation method of the above failure criteria, the device signal transmission failure state is determined by comprehensively considering the device signal transmission situation, and a device failure analysis diagram corresponding to the interference frequencies of the two failure modes is integrated. After testing, two-dimensional curves of the two failure factors are synthesized, and the sensitive frequency and volatility failure threshold are marked to determine the change of failure status with radio frequency under a fixed strength.

[0053] Example, refer to Figure 4The test results of the GL1200P model were plotted, combining the two failure modes, and the sensitive frequency range was determined to be 113-123MHz.

[0054] Step 5: Determine the rating criteria. Level A: The device functions normally. Level B: The device is affected by interference but has not reached a failure state. Level C: Partial functional failure of the device, but the interference decreases as the interference load decreases. Level D: Persistent functional failure of the device, but can be restored by simple operation or cooling after removing the interference load. Level E: Permanent functional failure of the device.

[0055] The GL1200P model device experiences transmission failure in some frequency bands, but the resulting interference decreases as the interference load decreases. Therefore, its immunity level is rated as C at this intensity.

[0056] Step 6: Evaluate the magnetic field immunity of the digital isolator. The evaluation results include the sensitive frequency range, device failure analysis diagram, and device failure rating.

[0057] The above evaluation methods are summarized, and the evaluation results of the magnetic field immunity of digital isolators are presented through three factors: the failure sensitive frequency range, the device failure analysis diagram, and the failure rating results corresponding to the magnetic field strength.

[0058] The process for evaluating the magnetic field immunity of digital isolators includes:

[0059] S1: Obtain the magnetic field immunity test data of the digital isolator. The input signal of the isolator adopts a square wave with a duty cycle of 50% and a level of 0-5.0V.

[0060] S2: Determine the failure criteria, which include two failure modes: level fluctuation exceeding the limit and level fixed 0 / 1. For level fluctuation exceeding the limit, the failure threshold is set as high level below 0.7·VH and low level above 0.3·(VH-VL)+VL. For level fixed 0 / 1 failure, the failure threshold is set as level length L(0 / 1)≥λ.

[0061] S3: Determine the frequency range in which the device is sensitive to radiation, which covers the peak value of level fluctuation exceeding the limit and the failure part of level fixed 0 / 1;

[0062] S4: Generate device failure analysis diagrams corresponding to the two failure modes, including failure state, failure peak frequency, frequency-corresponding level fluctuation, and failure-sensitive frequency;

[0063] S5, Determine the rating criteria: A-level: The device performs its function normally. B-level: The device is affected by interference but has not reached a failure state. C-level: Partial functional failure of the device, but the interference decreases as the interference load decreases. D-level: Persistent functional failure of the device, but can be restored by simple operation or cooling after removing the interference load. E-level: Permanent functional failure of the device;

[0064] S6 evaluates the magnetic field immunity of the digital isolator. The evaluation results include the sensitive frequency range, device failure analysis diagram, and device failure rating.

Claims

1. A method for evaluating the magnetic field immunity of a digital isolator, characterized in that, The detection square wave is transmitted through a digital isolator. The difference between the highest and lowest points of the output level fluctuation and the standard value is recorded when the output level fluctuates under high and low levels. At the same time, the 0 / 1 continuity of the output level is recorded. The output waveform is comprehensively evaluated by two failure modes: level fluctuation error failure and level fixed 0 / 1 failure. The sensitive frequency range is recorded and the two failure modes are synthesized into the same image. Finally, the magnetic field immunity of the device is rated.

2. The method for evaluating the magnetic field immunity of a digital isolator according to claim 1, characterized in that, The detection square wave has the following characteristics: duty cycle 50%, voltage level 0-5V, and frequency 1MHz.

3. The method for evaluating the magnetic field immunity of a digital isolator according to claim 1, characterized in that, The aforementioned level fluctuation excess failure mode is characterized by a level fluctuation rate exceeding the failure thresholds of 0.7·VH for high level and 0.3·(VH-VL)+VL for low level.

4. The method for evaluating the magnetic field immunity of a digital isolator according to claim 1, characterized in that, The aforementioned fixed 0 / 1 failure mode: using an oscilloscope wavelength trigger to capture the output waveform showing a 0 or 1 level for more than half a cycle.

5. The method for evaluating the magnetic field immunity of a digital isolator according to claim 1, characterized in that, The specified sensitive frequency range refers to the radio frequency interference frequency with the highest failure rate, where the trigger level is fixed at 0 / 1, the failure frequency is high or even completely fails, and the failure rate fluctuates within the specified range.

6. The method for evaluating the magnetic field immunity of a digital isolator according to claim 1, characterized in that, The aforementioned synthesis of two failure modes into the same image is a schematic diagram of integrated evaluation using transmission frequency, volatility, and level fixed 0 / 1 failure as two-axis coordinates. The image consists of a failure area and a normal area, and the failure threshold boundaries of the two failure modes correspond to each other.

7. The method for evaluating the magnetic field immunity of a digital isolator according to claim 1, wherein the sensitive frequency range is characterized in that: The frequency range corresponding to the occurrence of the maximum level fluctuation rate and the occurrence of a fixed 0 / 1 failure.

8. The method for evaluating the magnetic field immunity of a digital isolator according to claim 1, characterized in that, The method for rating the magnetic field immunity of devices is as follows: Level A: All functions of the digital isolator perform as designed during and after the interference; Level B: Most functions of the digital isolator perform as designed during testing, may be affected but can still function normally, and the transmission function can automatically return to normal range after the interference is removed; Level C: Some functions of the digital isolator do not perform as designed during testing, but immediately return to normal operation after the load is removed and the impact decreases as the load decreases; Level D: The functions of the digital isolator do not perform as designed during testing until the load is removed, and can be reset by simple operation or cooling; Level E: One or more functions of the digital isolator cannot operate as designed during and after testing and cannot be permanently restored to normal operation.

9. The method for evaluating the magnetic field immunity of a digital isolator according to claim 3, characterized in that, The formula for defining volatility is: α = V_b / VH, where V_b is the maximum single-level fluctuation offset and VH is the theoretical output high-level value.

10. A method for evaluating the magnetic field immunity of a digital isolator, characterized in that, include: S1: Obtain the magnetic field immunity test data of the digital isolator. The input signal of the isolator adopts a square wave with a duty cycle of 50% and a level of 0-5.0V. S2: Determine the failure criteria, which include two failure modes: level fluctuation exceeding the limit and level fixed 0 / 1. For level fluctuation exceeding the limit, the failure threshold is set as high level below 0.7·VH and low level above 0.3·(VH-VL)+VL. For level fixed 0 / 1 failure, the failure threshold is set as level length L(0 / 1)≥λ. S3: Determine the frequency range in which the device is sensitive to radiation, which covers the peak value of level fluctuation exceeding the limit and the failure part of level fixed 0 / 1; S4: Generate device failure analysis diagrams corresponding to the two failure modes, including failure state, failure peak frequency, frequency-corresponding level fluctuation, and failure-sensitive frequency; S5, Determine the rating criteria: A level: The device performs its functions normally; B level: The device is interfered with but has not reached a failure state; C level: Partial failure of the device's functions, but the interference decreases as the interference load decreases; D level: The device's functions have suffered a persistent failure, but can be restored by simple operation or cooling after the interference load is removed; E level: The device's functions have been permanently failed. S6 evaluates the magnetic field immunity of the digital isolator. The evaluation results include the sensitive frequency range, device failure analysis diagram, and device failure rating.

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