Electromagnetic interference suppression method and system based on piezoelectric ceramic weak coupling integration

Abstract

The invention discloses an electromagnetic interference suppression method and system based on piezoelectric ceramic weak coupling integration. The method comprises the following steps: providing an electromechanical model of a single piezoelectric ceramic in a radial vibration mode and listing an equivalent circuit parameter equation of the electromechanical model; establishing a correlation function of the physical size, the material parameter and the resonance frequency of the piezoelectric ceramic in a weak coupling integration state by combining a piezoelectric ceramic electromechanical model and an impedance expression; determining a gap size threshold value between the piezoelectric ceramics under a weak coupling condition; weak coupling piezoelectric ceramic filter integration based on plane expansion is realized. Interference peak values of multiple frequencies can be greatly suppressed, so that the size and the weight of the filter are effectively reduced, and the cost of the overall suppression scheme is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of filters, and particularly to an EMI suppression method and system based on weak coupling integration of piezoelectric ceramics. Background Art

[0002] In modern electronic systems, electromagnetic interference (EMI) suppression has always been an important technical problem, especially in application scenarios with high power density requirements and strict restrictions on size and weight. Passive EMI filters are widely used in various power electronic devices due to their simple structure and low cost. However, they often face limitations in terms of design flexibility, volume, and weight in practical applications. Especially in the context of the increasing popularity of high-frequency switching devices (such as GaN and SiC in wide bandgap semiconductor technology), the EMI problem has become even more serious, which is particularly significant in application scenarios with extremely high system performance requirements, such as aerospace, military, and portable devices.

[0003] Although the introduction of wide bandgap semiconductors has significantly improved the power density and conversion efficiency of electronic systems, their large voltage change rate has also made the EMI problem more complex. To effectively suppress EMI with a high interference level, traditional passive EMI filters often need to increase the size or use more filtering elements, which to a certain extent weakens the power density advantage brought by wide bandgap technology. Therefore, in these application scenarios, how to optimize the size, weight, and cost of the filter while meeting the EMI suppression requirements has become a key problem that engineers urgently need to solve.

[0004] Piezoelectric ceramics exhibit impedance characteristics similar to capacitors in a wide frequency range, so they can replace the Y capacitors in passive EMI filters and effectively suppress common-mode EMI. In addition, piezoelectric ceramics have a low impedance at the resonant frequency, so that a large attenuation of discrete interference peaks can be achieved. Based on the above characteristics of piezoelectric ceramics, applying them to passive EMI filters not only helps to optimize the weight and size of the filter, but also improves the power density of the device, thereby enhancing the efficiency of the overall system.

[0005] For example, Chinese Patent Publication No. CN118920043A, titled "An EMI Filter Integration Method Based on a Multidimensional Stacking Method of Piezoelectric Ceramics", uses piezoelectric ceramics and stacks them. However, stacking can only suppress a single interference peak and has poor adaptability. How to suppress interference peaks at multiple frequencies is the problem faced currently. Summary of the Invention

[0006] The present invention provides a method and system for electromagnetic interference suppression based on weak coupling integration of piezoelectric ceramics, which can design the resonance frequencies of multiple piezoelectric ceramics and integrate them through weak coupling to achieve efficient suppression of EMI, thereby making the filter lighter in weight and smaller in size.

[0007] The technical solution of the present invention is: a method for electromagnetic interference suppression based on weak coupling integration of piezoelectric ceramics, comprising the following steps:

[0008] Step S1: Propose an electromechanical model under the radial vibration mode of a single piezoelectric ceramic and list its equivalent circuit parameter equations to obtain the impedance expression under the radial vibration mode of the piezoelectric ceramic;

[0009] Step S2: Based on Step S1, list the impedance expression of the electromechanical model under the weak coupling integration state of the piezoelectric ceramics;

[0010] Step S3: Based on Steps S1 and S2, establish a correlation function of physical dimensions, material parameters and resonance frequencies under the weak coupling integration state of the piezoelectric ceramics;

[0011] Step S4: Based on the correlation function, determine the gap size threshold between the piezoelectric ceramics under the weak coupling condition, so as to realize the integration of the weak coupling piezoelectric ceramic filter based on planar expansion.

[0012] In Step S1, the equivalent circuit parameter equations of the electromechanical model under the radial vibration mode of a single piezoelectric ceramic are as follows:

[0013]

[0014] In the formula, is the dielectric constant component under constant stress, k p is the electromechanical coupling coefficient, l and c are the length and thickness of the piezoelectric ceramic respectively, σ E is the Poisson's ratio, h is the number of resonances, ρ is the density of the material, is the elastic compliance constant, Q mi is the mechanical quality factor, C R represents the inherent capacitance of the piezoelectric ceramic, C Ri represents the spring stiffness, L Ri represents the inertial mass, R Ri represents the mechanical loss, f Ri represents the resonance frequency;

[0015] Among them,

[0016]

[0017] The impedance expression under the radial vibration mode of the piezoelectric ceramic is:

[0018]

[0019] In the formula, Z R represents the impedance in the radial vibration mode of the piezoelectric ceramic, i is the number of piezoelectric modules, j is the imaginary number, and ω is the angular frequency.

[0020] In step S2, the impedance expression of the electromechanical model in the weakly coupled integrated state of the piezoelectric ceramic includes:

[0021]

[0022] In the formula, n represents the number of piezoelectric modules, Z Ri represents the impedance of the weakly coupled integration of the piezoelectric ceramic, R Rn represents the mechanical loss, L Rn represents the inertial mass, C Rn represents the spring stiffness.

[0023] In step S3, the correlation function is:

[0024]

[0025] In the formula, f r,i represents the resonance frequency in the weakly coupled integrated state of the piezoelectric ceramic.

[0026] In step S4,

[0027] Import the correlation function into the finite element simulation software, set the electromechanical coupling coefficient, and obtain the threshold range.

[0028] The electromechanical coupling coefficient equation is:

[0029]

[0030] In the formula, k ij represents the electromechanical coupling coefficient, Δx j represents the deformation of the nth piezoelectric module, x j represents the initial size of the nth piezoelectric module, ΔU i represents the voltage variable of the ith piezoelectric module, U i represents the initial voltage of the ith piezoelectric module.

[0031] The set electromechanical coupling coefficient needs to satisfy

[0032] An electromagnetic interference suppression system based on the weak coupling integration of piezoelectric ceramics includes:

[0033] A single impedance module, which is used to propose the electromechanical model in the radial vibration mode of a single piezoelectric ceramic and list its equivalent circuit parameter equation, and obtain the impedance expression in the radial vibration mode of the piezoelectric ceramic;

[0034] A coupling module, configured to list the impedance expression of the electromechanical model in the weakly coupled integrated state of piezoelectric ceramics;

[0035] An association module, configured to establish a correlation function among the physical dimensions, material parameters, and resonance frequency in the weakly coupled integrated state of piezoelectric ceramics;

[0036] A determination module, configured to determine the threshold value of the gap size between piezoelectric ceramics under weak coupling conditions based on the correlation function, so as to realize the integration of weakly coupled piezoelectric ceramic filters based on planar expansion.

[0037] In the operation of the present invention, by proposing an electromechanical model in the radial vibration mode of a single-piece piezoelectric ceramic and listing its equivalent circuit parameter equations, combining the electromechanical model and impedance expression of the piezoelectric ceramic, a correlation function among the physical dimensions, material parameters, and resonance frequency in the weakly coupled integrated state of the piezoelectric ceramic is established, so as to determine the threshold value of the gap size between piezoelectric ceramics under weak coupling conditions and realize the integration of weakly coupled piezoelectric ceramic filters based on planar expansion. The present invention can design the resonance frequencies of multiple piezoelectric ceramics and integrate them in a weakly coupled manner, thereby greatly suppressing the interference peaks of multiple frequencies, making the filter lighter in weight and smaller in size. Description of the Drawings

[0038] Figure 1 is a flowchart of an EMI suppression method based on weakly coupled integration of piezoelectric ceramics according to an embodiment of the present invention;

[0039] Figure 2 is a schematic diagram of the radial vibration mode of a piezoelectric ceramic according to an embodiment of the present invention;

[0040] Figure 3 is an equivalent circuit structure of the radial vibration mode of a single-piece piezoelectric ceramic according to an embodiment of the present invention;

[0041] Figure 4 is an equivalent circuit structure in the weakly coupled integrated state of piezoelectric ceramics according to an embodiment of the present invention;

[0042] Figure 5 is an electromechanical model diagram in the weakly coupled integrated state of piezoelectric ceramics according to an embodiment of the present invention;

[0043] Figure 6 is a physical object and a three-dimensional model of weakly coupled integration of piezoelectric ceramics according to an embodiment of the present invention;

[0044] Figure 7 is a schematic diagram of using weakly coupled integrated piezoelectric ceramics to suppress EMI according to an embodiment of the present invention;

[0045] Figure 8It is the suppression effect of suppressing EMI using piezoelectric ceramics with weak coupling integration according to an embodiment of the present invention. Detailed implementation manners

[0046] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and cannot be used to limit the protection scope of the present invention.

[0047] Refer to Figure 1 , an electromagnetic interference suppression method based on weak coupling integration of piezoelectric ceramics provided by an embodiment of the present invention performs the following steps S1 - step S5, and can realize the integration of a weak coupling piezoelectric ceramic filter based on planar expansion (i.e., integration in the planar direction).

[0048] Through weak coupling integration, the piezoelectric ceramics of the present invention can suppress multiple interference peaks, thereby further reducing the size and weight of the common mode inductor to achieve the lightweight and compactness of the filter.

[0049] "Weak coupling" is to connect piezoelectric ceramics of different sizes by decoupling the connection points of the piezoelectric ceramics, thereby suppressing interference peaks at multiple frequencies.

[0050] Specifically, it includes:

[0051] Step S1: Propose an electromechanical model under the radial vibration mode of a single-piece piezoelectric ceramic and list its equivalent circuit parameter equations;

[0052] The electromechanical model is an electromechanical structure. Refer to Figure 2 the radial vibration mode of the piezoelectric ceramic shown, where p is the polarization direction, U1 and U2 are the directions of the radial vibration mode, and its equivalent circuit structure is as Figure 3 shown, and the corresponding equivalent circuit parameter equations are as follows:

[0053]

[0054] In the formula, is the dielectric constant component under constant stress, k p is the electromechanical coupling coefficient, l and c are the length and thickness of the piezoelectric ceramic respectively, σ E is the Poisson's ratio, h is an odd number representing the number of resonances, ρ is the density of the material, is the elastic compliance constant, Q mi is the mechanical quality factor, C R represents the inherent capacitance of the piezoelectric ceramic, C Ri represents the spring stiffness, L Ri represents the inertial mass, R Ri represents the mechanical loss, and there are the following relationships:

[0055]

[0056] In the formula, f Ri represents the resonant frequency, i is the number of piezoelectric modules, j is the imaginary number, ω is the angular frequency, and Z R represents the impedance expression in the radial vibration mode of the piezoelectric ceramic.

[0057] Step S2: According to the impedance expression in the radial vibration mode of the piezoelectric ceramic proposed in Step S1, the impedance expression of its electromechanical model in the weakly coupled integrated state can be listed:

[0058]

[0059] where n represents the number of piezoelectric modules, and Z Ri represents the impedance of the weakly coupled integration of the piezoelectric ceramic, R Rn represents the mechanical loss, L Rn represents the inertial mass, C Rn represents the spring stiffness, and its equivalent circuit structure is as shown in Figure 4 shown.

[0060] Step S3: Combining the piezoelectric parameter equation proposed in Step S1 and the impedance expression listed in Step S2, the correlation function of the physical dimensions, material parameters, and resonant frequency of the piezoelectric ceramic in the weakly coupled integrated state can be established:

[0061]

[0062] In the formula, f r,i represents the resonant frequency of the piezoelectric ceramic in the weakly coupled integrated state.

[0063] Step S4: Determine the gap size threshold between the piezoelectric ceramics under the weak coupling condition;

[0064] Import the correlation function into the finite element simulation software, and set the electromechanical coupling coefficient in the software to obtain the threshold range.

[0065] Since too large a size at the connection will affect the selection accuracy of the resonant frequency of the piezoelectric ceramic, and too small a size may lead to insufficient mechanical strength, thus affecting the stability and reliability of the piezoelectric ceramic. Therefore, it is necessary to determine the gap size threshold between the piezoelectric ceramics under the weak coupling condition. The gap size is the size of the connection between the piezoelectric ceramics.

[0066] Based on the finite element method and piezoelectric material parameters, an electromechanical model of the piezoelectric ceramic in the weakly coupled integrated state is constructed, as shown in Figure 5 shown, where 1-8 represent 8 piezoelectric modules integrated in a weakly coupled manner; the piezoelectric module specifically refers to: after the piezoelectric ceramics are integrated, it is used to describe a single piezoelectric ceramic.

[0067] Establish the electromechanical coupling coefficient equation between modules in the weakly coupled integrated state of piezoelectric ceramics:

[0068]

[0069] In the formula, Δx j represents the deformation of the nth piezoelectric module, and x j represents the initial size of the nth piezoelectric module, ΔU i represents the voltage variable of the ith piezoelectric module, and U i represents the initial voltage of the ith piezoelectric module, and k ij represents the electromechanical coupling coefficient between modules in the weakly coupled integrated state of piezoelectric ceramics.

[0070] Determine the gap size threshold between piezoelectric ceramics under weak coupling conditions. The correlation function of its physical size, material parameters and resonance frequency can be imported into the finite element simulation software, so as to simulate the influence of different gap sizes on the resonance frequency of piezoelectric ceramics.

[0071] When it can be considered that the coupling will not affect the resonance frequency of each piezoelectric module. If it is greater, it means that the resonance frequencies will affect each other and need to be adjusted.

[0072] An electromagnetic interference suppression system based on weakly coupled integration of piezoelectric ceramics, comprising:

[0073] A single impedance module, used to propose the electromechanical model under the radial vibration mode of a single piezoelectric ceramic and list its equivalent circuit parameter equation, and obtain the impedance expression under the radial vibration mode of the piezoelectric ceramic;

[0074] A coupling module, used to list the impedance expression of the electromechanical model in the weakly coupled integrated state of piezoelectric ceramics;

[0075] A correlation module, used to establish the correlation function of physical size, material parameters and resonance frequency in the weakly coupled integrated state of piezoelectric ceramics;

[0076] A determination module, used to determine the gap size threshold between piezoelectric ceramics under weak coupling conditions based on the correlation function, so as to realize the integration of weakly coupled piezoelectric ceramic filters based on planar expansion.

[0077] In application, taking two piezoelectric modules with a thickness of 1 mm and lengths of 10 mm and 5 mm respectively as an example, it can be calculated by the finite element method that when the size of the connection part is less than l = 2 mm and c = 1 mm, Therefore, the present invention sets the size of the connection part to l = 2 mm and c = 1 mm, so as to realize the integration of weakly coupled piezoelectric ceramic filters based on planar expansion, as Figure 6As shown. Apply it to the input end of a flyback converter (switching frequency is 167 kHz) to replace the Y capacitor as an interference suppression component (such as Figure 7 shown), it can significantly attenuate the interference peaks at its switching frequency and second harmonic (such as Figure 8 shown), thereby effectively reducing the size and weight of the common-mode inductor to achieve the lightweight and compactness of the filter. This method is also applicable to other types of filters.

[0078] The embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings, but the present invention is not limited to the above specific embodiments. Without departing from the core idea of the present invention, those of ordinary skill in the art can still make various changes and adjustments to the present invention within the scope of their professional knowledge.

Claims

1. A method for suppressing electromagnetic interference based on weakly coupled integration of piezoelectric ceramics, characterized in that: The following steps are involved: Step S1: Propose an electromechanical model of a single-piece piezoelectric ceramic under radial vibration mode and list its equivalent circuit parameter equations to obtain an impedance expression of the piezoelectric ceramic under radial vibration mode; Step S2: Based on step S1, an impedance expression of the electromechanical model of the piezoelectric ceramic in the weakly coupled integrated state is listed; Step S3: Based on steps S1 and S2, a correlation function among physical dimensions, material parameters and resonant frequency of the piezoelectric ceramic in a weakly coupled integrated state is established; Step S4: Based on the correlation function, determine the gap size threshold between piezoelectric ceramics under weak coupling conditions, so as to realize the integration of weakly coupled piezoelectric ceramic filters based on planar expansion.

2. The electromagnetic interference suppression method based on piezoelectric ceramic weak coupling integration according to claim 1 is characterized in that: In step S1, the equivalent circuit parameter equation of the electromechanical model under the radial vibration mode of the single-piece piezoelectric ceramic is as follows: In the formula, is the dielectric constant component under constant stress, k p is the electromechanical coupling coefficient, l and c are the length and thickness of the piezoelectric ceramic respectively, σ E is Poisson's ratio, h is the number of resonances, ρ is the density of the material, is the elastic compliance constant, Q mi is the mechanical quality factor, C R Indicates the intrinsic capacitance of piezoelectric ceramics, C Ri Indicates the spring stiffness, L Ri represents inertial mass, R Ri represents mechanical loss, f Ri represents the resonant frequency; in, 3. The electromagnetic interference suppression method based on piezoelectric ceramic weak coupling integration according to claim 2 is characterized in that: The impedance expression of piezoelectric ceramics in radial vibration mode is: In the formula, Z R It represents the impedance of the piezoelectric ceramic in the radial vibration mode, i is the number of piezoelectric modules, j is an imaginary number, and ω is the angular frequency.

4. The electromagnetic interference suppression method based on piezoelectric ceramic weak coupling integration according to claim 3 is characterized in that: In step S2, the impedance expression of the electromechanical model in the weakly coupled integrated state of the piezoelectric ceramic includes: Where n represents the number of piezoelectric modules, Z Ri R represents the impedance of the weakly coupled integrated piezoelectric ceramic. Rn Represents mechanical loss, L Rn represents the inertial mass, C Rn Indicates the spring stiffness.

5. The electromagnetic interference suppression method based on piezoelectric ceramic weak coupling integration according to claim 4 is characterized in that: In step S3, the correlation function is: In the formula, f r,i It represents the resonant frequency of the piezoelectric ceramic in the weakly coupled integrated state.

6. The electromagnetic interference suppression method based on piezoelectric ceramic weak coupling integration according to claim 5 is characterized in that: In step S4, The correlation function was imported into the finite element simulation software, the electromechanical coupling coefficient was set, and the threshold range was obtained.

7. The electromagnetic interference suppression method based on piezoelectric ceramic weak coupling integration according to claim 6 is characterized in that: The electromechanical coupling coefficient equation is: In the formula, k ij represents the electromechanical coupling coefficient, Δx j represents the deformation of the nth piezoelectric module, x j represents the initial size of the nth piezoelectric module, ΔU i represents the voltage variable of the i-th piezoelectric module, U i represents the initial voltage of the i-th piezoelectric module.

8. The electromagnetic interference suppression method based on piezoelectric ceramic weak coupling integration according to claim 6 is characterized in that: The set electromechanical coupling coefficient must satisfy 9. An electromagnetic interference suppression system based on piezoelectric ceramic weak coupling integration, characterized in that: include: Single impedance module, used to propose the electromechanical model of the single piezoelectric ceramic under the radial vibration mode and list its equivalent circuit parameter equation, and obtain the impedance expression of the piezoelectric ceramic under the radial vibration mode; Coupling module, which is used to list the impedance expression of the electromechanical model under the weakly coupled integrated state of piezoelectric ceramics; A correlation module is used to establish the correlation function of physical dimensions, material parameters and resonant frequency under the weak coupling integration state of piezoelectric ceramics; The determination module is used to determine the gap size threshold between piezoelectric ceramics under weak coupling conditions based on a correlation function, thereby realizing the integration of weakly coupled piezoelectric ceramic filters based on plane expansion.

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