A board level circuit fault detection system based on harmonic analysis

Abstract

The application discloses a board-level circuit fault detection system based on harmonic analysis and relates to the field of fault detection. The problem that, in a traditional frequency test method, only a single frequency point characteristic can be obtained through single test and multiple tests need to be carried out to obtain the complete frequency spectrum of a measured object is solved. In the application, a square wave signal is used as a test input signal, a wide frequency spectrum of a measured object is obtained through single test by means of harmonic analysis on input and output signals, a board-level circuit Bode diagram is drawn, and the fault condition of the board-level circuit is judged by making a difference between the Bode diagrams of a normally working board-level circuit and a to-be-measured board-level circuit, so that the efficient diagnosis of the board-level circuit by an automatic test system is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of fault detection, in particular to a board-level circuit fault detection system based on harmonic analysis. BACKGROUND

[0002] In order to realize fast and accurate fault detection, a model of the board-level circuit to be tested needs to be established. When using the traditional frequency domain test method to model the board-level circuit to be tested, different frequency test signals need to be repeatedly added to the board-level circuit to be tested, and the frequency characteristics of the object to be tested are obtained according to the output signals, and finally the model of the board-level circuit to be tested is constructed from the frequency characteristics. This method has a large amount of work and a long test time because it needs to be tested multiple times, and has certain limitations in practical application.

[0003] The square wave signal contains rich frequency domain components, and the input square wave in the test process is equivalent to inputting a group of sine waves with different frequencies. Therefore, by performing harmonic analysis on the response signal of the board-level circuit by taking the square wave signal as the input signal, the frequency response of each frequency can be decomposed by a special algorithm, and the detection of multiple frequency point characteristics by single test can be realized, which can greatly reduce the workload of the frequency domain test process and speed up the test speed. SUMMARY

[0004] The purpose of the present application is to provide an improved fault detection system based on harmonic analysis, which uses a square wave signal as an input signal to input a board-level circuit to be tested, and realizes the simultaneous test of multiple frequency point characteristics of the board-level circuit by performing harmonic analysis on the response signal, draws a Bode diagram of the board-level circuit, and realizes fault detection by comparing the Bode diagram.

[0005] The present application is implemented as follows:

[0006] 1. A board-level circuit fault detection system based on harmonic analysis, comprising the following steps:

[0007] (1) A control host drives a signal generating instrument to generate a square wave signal with an amplitude of , a period of , a duty cycle of 50%, and a phase of , and inputs to the board-level circuit to be tested.

[0008] (2) A signal acquisition module acquires the potential signal of the board-level circuit to be tested , and sends to the control host.

[0009] (3) The control host can calculate the response signal of the board-level circuit to be tested , , which can be obtained by an external load resistance , and the square wave signal​ , the potential signal is determined by

[0010] .

[0011] (4) The control host side square wave signal is Fourier series expanded,

[0012]

[0013] wherein is the angular frequency of the square wave, which can be calculated from , then the amplitude of the harmonic with a frequency of in can be obtained.

[0014] .

[0015] (5) The control host side response signal is Fourier decomposed, which can be expressed as

[0016] .

[0017] wherein: the coefficient , can be determined by the following formula:

[0018]

[0019]

[0020] the amplitude can be determined by the following formula:

[0021]

[0022] the phase can be determined by the following formula:

[0023] .

[0024] (6) Since the amplitude of each frequency component in the input signal is different, gain compensation is needed. The amplitude characteristic of the to-be-tested board-level circuit for the sinusoidal wave with a frequency of is , which can be determined by the following formula:

[0025] .

[0026] (7) The phase-frequency characteristic of the to-be-tested board-level circuit for the sinusoidal wave with a frequency of is

[0027] .

[0028] (8) According to (6), (7), the amplitude-frequency characteristic and the phase-frequency characteristic of the measured board-level circuit are obtained, and the Bode diagram is drawn, that is, the frequency characteristic diagram of the measured board-level circuit is obtained.

[0029] (9) The board-level circuit in normal working state and the board-level circuit to be measured are tested respectively, and the Bode diagram in ideal working state and the Bode diagram of the board-level circuit to be measured .

[0030] (10) The Bode diagram is integrated to obtain the fault discrimination value

[0031] .

[0032] (11) The Bode diagram is subtracted from the Bode diagram , the absolute value is obtained, and the integral is carried out to obtain the fault discrimination value

[0033] .

[0034] (12) If , the control host sends a fault warning. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is the schematic diagram of the present application.

[0036] Figure 2 is the implementation circuit diagram of the present application.

[0037] Figure 3 is the schematic diagram of the frequency spectrum component of the square wave signal. DETAILED DESCRIPTION

[0038] The above scheme will be further described below in combination with specific examples, and the present application is selected as follows:

[0039] Example 1:

[0040] In this embodiment, referring to Figure 1 and Figure 2 , the board-level circuit fault detection system based on harmonic analysis adopts a square wave signal as an input signal of the board-level circuit to be measured, and realizes simultaneous testing of multiple frequency point characteristics of the board-level circuit by harmonic analysis on the response signal, draws the Bode diagram of the board-level circuit, and realizes fault detection through comparison of the Bode diagram, including the following steps:

[0041] (1) The control host drive function generator module PXI-5413 generates a square wave signal with amplitude , period , duty cycle 50%, and phase , and the is input to the board-level circuit to be tested.

[0042] (2) The oscilloscope module PXI-5114 measures the voltage across the circuit to be tested and sends to the control host.

[0043] (3) The control host can calculate the response signal of the board-level circuit to be tested, which can be determined by the external load resistance , square wave signal , and potential signal through the following formula

[0044] .

[0045] (4) The control host performs Fourier series expansion on the square wave signal ,

[0046]

[0047] where is the angular frequency of the square wave, and can be calculated, so that the amplitude of the harmonic with a frequency of in

[0048] .

[0049] (5) The control host performs Fourier decomposition on the response signal , which can be represented as

[0050]

[0051] where: coefficients , can be determined by the following formula:

[0052]

[0053]

[0054] The amplitude can be determined by the following formula:

[0055] ​​

[0056] Phase The phase can be determined by the following formula:

[0057] .

[0058] (6) Because the amplitude of each frequency component in the input signal is different, gain compensation is needed. The amplitude characteristic of the measured board-level circuit for a sinusoidal wave with a frequency of is , which can be determined by the following formula:

[0059] .

[0060] (7) The phase-frequency characteristic of the measured board-level circuit for a sinusoidal wave with a frequency of is

[0061] .

[0062] (8) According to the results obtained in (6) and (7), the amplitude-frequency characteristic and the phase-frequency characteristic of the measured board-level circuit are obtained, and the Bode diagram is drawn, i.e. the frequency characteristic diagram of the measured board-level circuit is obtained.

[0063] (9) The board-level circuit in normal working state and the measured board-level circuit are tested respectively, and the ideal working state Bode diagram and the measured board-level circuit Bode diagram are obtained.

[0064] (10) The Bode diagram is integrated to obtain the fault discrimination value

[0065] .

[0066] (11) The Bode diagram and the Bode diagram are subtracted, the absolute value is taken, and integration is performed to obtain the fault discrimination value

[0067] .

[0068] (12) If , the control host issues a fault warning.

[0069] In this example, a single test can achieve measurement of at least three frequency points. In the traditional method, the instrument startup time in a single measurement is 0.3 s, and the steady-state time of the board-level circuit to be measured is 1 s, so at least 3.9 s is required to complete the measurement of three frequency points. In this method, the instrument startup time in a single measurement is 0.3 s, the steady-state time of the board-level circuit to be measured is 1 s, and the control host analysis time is 1 s, so the time required to complete the measurement of three frequency points is 2.3 s. It can be seen that this method greatly speeds up the test speed.

Claims

1. A board-level circuit fault detection system based on harmonic analysis, characterized in that: a host computer drives a signal generating instrument, such as a function generator, to generate a square wave signal, which is input to the board-level circuit under test. Simultaneously, the host computer controls a signal acquisition instrument, such as an oscilloscope, to acquire the response signal of the board-level circuit under test. Then, the host computer performs harmonic analysis on the square wave signal, calculates the amplitude of each frequency component of the square wave signal, and then performs harmonic analysis and gain compensation on the response signal to obtain the frequency characteristics of the board-level circuit under test. A Bode plot is then generated. The system tests the board-level circuit under normal operating conditions and generates the corresponding Bode plot for the normally operating board-level circuit. The system tests the board-level circuit under test and draws the Bode diagram of the board-level circuit under test. Bode plot Find the integral over the Bode plot. Bode diagram Find the difference, integrate the absolute value of the difference, and determine whether the system is faulty based on the integral result. The specific steps are as follows: The control host drives the signal generation instrument to generate an amplitude of The cycle is Duty cycle 50%, phase is square wave signal ,Will Input to the board-level circuit under test (2) The signal acquisition module acquires the potential signal at both ends of the circuit under test. ,Will Send to the control host, (3) The control host can calculate the response signal of the circuit at the board level under test. , The resistance value can be determined by the external load resistor. Square wave signal Potential signal Determined by the following formula (4) Control host square wave signal Perform a Fourier series expansion. in Let be the angular frequency of the square wave, given by... If it can be calculated, then it can be obtained. The intermediate frequency is The amplitude of the harmonics is (5) The host computer responds to the signal Perform Fourier decomposition. It can be represented as in: coefficient , It can be determined by the following formula: Amplitude It can be determined by the following formula: phase It can be determined by the following formula: (6) Since the amplitudes of the frequency components in the input signal are different, gain compensation is required. The board-level circuit under test requires a gain compensation for the frequency of... The amplitude characteristics of the sine wave are as follows: , It can be determined by the following formula: (7) The circuit under test for frequency is The phase frequency characteristic of the sine wave is (8) Based on the results obtained in (6) and (7), the amplitude-frequency characteristics and phase-frequency characteristics of the board-level circuit under test are obtained, and the Bode plot is drawn to obtain the frequency response diagram of the board-level circuit under test. (9) Test the board-level circuit under normal working conditions and the board-level circuit under test respectively to obtain the Bode diagram of the ideal working state. Bode diagram of the board-level circuit under test (10) Bode diagram Integrate to obtain the fault diagnosis value. (11) Bode diagram Bode diagram By taking the difference, finding the absolute value, and integrating, we obtain the fault diagnosis value. (12) If If this happens, the control host will issue a fault warning.

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