Piezoelectric ceramic EMI filter design method considering temperature drift and frequency offset compensation

Abstract

The invention discloses a piezoelectric ceramic EMI filter design method considering temperature drift and frequency offset compensation. The method comprises the steps that 1, the nonlinear modulation relation of voltage in a piezoelectric ceramic piece to resonant frequency is measured; 2, fitting a temperature coefficient by combining the actually measured relationship between the temperature change of the piezoelectric ceramic and the resonant frequency deviation; 3, capturing the influence of the temperature change on the resonant frequency behavior of the piezoelectric ceramic tuned filter, and constructing a nonlinear temperature-frequency offset transfer function model in combination with the nonlinear modulation relation and the temperature coefficient; 4, setting specific constraint conditions according to actual electromagnetic interference suppression requirements of the frequency converter; and step 5, sampling response data of the piezoelectric ceramic in real time, and dynamically adjusting the bias voltage based on the temperature-frequency offset transfer function obtained by calculation to perform tuning so as to obtain a filtering result meeting a constraint condition.

Description

Technical Field

[0001] The present invention relates to the field of electronic equipment, and in particular to a piezoelectric ceramic EMI filter design method considering temperature drift and frequency offset compensation. Background Art

[0002] In active EMI filter design, piezoelectric ceramics are widely used for frequency regulation and noise suppression due to their excellent tuning properties. However, the resonant frequency of piezoelectric ceramics is affected by many factors, with temperature being a key factor. During operation, rising temperature of piezoelectric ceramics causes changes in their material properties, particularly the dielectric constant and piezoelectric constant, which directly cause a shift in the resonant frequency.

[0003] The impact of temperature on piezoelectric ceramics is primarily reflected in the coupled effects of their electrical and mechanical properties. As temperature rises, the piezoelectric coefficient and elastic modulus of piezoelectric ceramics change, affecting their resonant frequency. Especially in dynamic regulation, rising temperature can exacerbate hysteresis, leading to a decrease in frequency regulation accuracy, which negatively impacts the noise suppression capabilities of active EMI filters.

[0004] To achieve stable noise suppression in highly dynamic power electronic devices, the effect of temperature on the resonant frequency of piezoelectric ceramics must be considered and effective compensation strategies must be implemented. This paper proposes a design method for active EMI filters based on temperature effect compensation. By measuring temperature changes in real time and correcting for frequency offsets, this method ensures precise filter adjustment and efficient noise suppression under varying operating conditions. Summary of the Invention

[0005] Purpose of the invention: The technical problem to be solved by the present invention is to provide a piezoelectric ceramic EMI filter design method taking into account temperature drift and frequency offset compensation in view of the shortcomings of the existing technology.

[0006] In order to solve the above technical problems, the present invention discloses a piezoelectric ceramic EMI filter design method considering temperature drift and frequency offset compensation. The piezoelectric ceramic EMI filter is composed of a piezoelectric ceramic sheet and an electrode;

[0007] The filtering steps of the piezoelectric ceramic tuned filter are as follows:

[0008] Step 1, measuring the nonlinear modulation relationship between the voltage and the resonant frequency in the piezoelectric ceramic piece;

[0009] Step 2: fitting the temperature coefficient based on the relationship between the temperature change of the piezoelectric ceramic and the resonant frequency shift actually measured;

[0010] Step 3: Capture the effect of temperature change on the resonant frequency behavior of the piezoelectric ceramic tunable filter and build a nonlinear temperature-frequency deviation transfer function model by combining the nonlinear modulation relationship and temperature coefficient;

[0011] Step 4: Set specific constraints based on the actual inverter electromagnetic interference suppression requirements;

[0012] Step 5: Sample the response data of the piezoelectric ceramic in real time, and dynamically adjust the bias voltage based on the calculated temperature-frequency deviation transfer function to perform tuning, so as to obtain a filtering result that meets the constraint conditions.

[0013] The optimal size of the piezoelectric ceramic piece is calculated as follows:

[0014] Step 1.1, the differential evolution algorithm (DE algorithm)-impedance trajectory fitting joint optimization method is used to summarize the cross-scale mapping relationship function Z between the material constitutive parameters and geometric dimensions under multiple vibration modes of piezoelectric ceramics. model (f; l, c, t), f is the resonant frequency of the piezoelectric ceramic, l, c, t are the length, width, and thickness of the piezoelectric ceramic respectively;

[0015] Step 2.1: For the fixed-frequency discrete peaks to be filtered out in the electromagnetic interference (EMI) spectrum of the photovoltaic inverter, which are generated by the periodic switching action of the switching devices, set the constraints, including: providing a sufficiently high insertion loss at the fixed-frequency peak to suppress the conducted interference; and optimizing the Z by the DE algorithm-impedance trajectory fitting joint optimization method. model (f; l, c, t) are optimized to find the optimal size of the piezoelectric ceramic.

[0016] Step 1 specifically includes: applying a bias voltage in the vibration direction of the piezoelectric ceramic to obtain a nonlinear modulation relationship between the voltage and the resonant frequency in the piezoelectric ceramic;

[0017] The nonlinear modulation relationship between the voltage and the resonant frequency in the piezoelectric ceramic is shown in the following formula:

[0018]

[0019] Where f0 is the resonant frequency without bias, L is the length of the ceramic, χ and τ are the nonlinear coefficients of the material, V is the voltage applied to each piezoelectric ceramic, and f 0 (V) is the resonant frequency when the bias voltage is V.

[0020] In step 2, the first-order temperature coefficient kT li and the second-order temperature coefficient kT liThe frequency offset data at different temperatures are measured experimentally, and a quadratic polynomial model is used for fitting. The parameter values are optimized using the least squares method, and the fitting effect is verified by residual analysis to achieve the calibration of the temperature coefficient.

[0021] Step 3 is as follows:

[0022] Step 3-1, analyze the temperature compensation, and use the difference between the actual temperature T and the reference ambient temperature T0 (T-T0) to express the linear response. As the difference between T and T0 changes, the output changes linearly, and its square term (T-T0) 2 To express the secondary response, it is used to describe the nonlinear effect of temperature influence, and the temperature-frequency deviation transfer function is set as:

[0023] Tem i (T) = kT 1i (T-T0)+kT 2i (T-T0) 2

[0024] Among them, kT li , kT li are the first-order and second-order temperature coefficients, T0 is the reference temperature, and T is the real-time temperature;

[0025] In step 3-2, the temperature compensation factor is incorporated into the nonlinear modulation relationship between voltage and resonant frequency in a single ceramic to obtain the final relationship function between bias voltage, temperature and ceramic resonance:

[0026]

[0027] The constraints described in step 4 include: target coverage frequency range; single-segment piezoelectric ceramic tuning range; frequency band overlap rate between adjacent segments; multi-segment collaborative tuning synchronization error; and maximum safe electric field strength.

[0028] Step 5 is as follows:

[0029] Step 5-1: Dynamically sample the inverter EMI noise frequency f in real time noise ;

[0030] Step 5-2, based on the relationship function between the final bias voltage, temperature and ceramic resonance, the bias voltage V is dynamically adjusted in combination with feedforward compensation and closed-loop feedback correction to tune the noise frequency f noise Perform filtering.

[0031] The tuning by adjusting the bias voltage in step 5 is specifically as follows: applying a DC bias voltage to the bias voltage electrode of the piezoelectric ceramic piece, and covering different frequency bands in sections by adjusting the bias voltage.

[0032] The electrodes include access electrodes and bias voltage electrodes.

[0033] When there are two or more piezoelectric ceramic sheets, they are connected according to a topological structure.

[0034] Beneficial effects:

[0035] This invention uses a temperature-frequency deviation transfer function to accurately model the temperature-resonant frequency relationship of piezoelectric ceramics, calculates the first-order and second-order temperature coefficients, and effectively compensates for the resonant frequency offset caused by temperature effects, thereby improving the accuracy and stability of the filter. Simultaneously, real-time sampling and dynamic adjustment of the compensation strategy ensure that the filter maintains high-precision frequency regulation under various operating conditions. Taking into account the actual requirements for variable-frequency EMI suppression, this invention sets constraints to ensure that the filter can effectively suppress variable-frequency noise and optimize EMI suppression performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of the equivalent circuit topology of piezoelectric ceramics.

[0037] Figure 2 The vibration mode of the piezoelectric ceramic.

[0038] Figure 3 Schematic diagram of voltage access for a single piezoelectric ceramic filter.

[0039] Figure 4 Schematic diagram of voltage access for multiple piezoelectric ceramic filters.

[0040] Figure 5 It is the algorithm flow chart of the present invention. DETAILED DESCRIPTION

[0041] The present invention provides an active EMI filter design method that takes into account the compensation of the temperature drift and frequency deviation effect of piezoelectric ceramics, aiming to eliminate the influence of the temperature effect of piezoelectric ceramics on the frequency adjustment accuracy and improve the performance of the filter in a high-dynamic power electronic system.

[0042] Example:

[0043] A piezoelectric ceramic EMI filter design method considering temperature drift and frequency offset compensation, wherein the piezoelectric ceramic EMI filter is composed of a piezoelectric ceramic sheet and electrodes;

[0044] The filtering steps of the piezoelectric ceramic tuned filter are as follows:

[0045] Step 1, measuring the nonlinear modulation relationship between the voltage and the resonant frequency in the piezoelectric ceramic piece;

[0046] Step 2: fitting the temperature coefficient based on the relationship between the temperature change of the piezoelectric ceramic and the resonant frequency shift actually measured;

[0047] Step 3: Capture the effect of temperature change on the resonant frequency behavior of the piezoelectric ceramic tunable filter and build a nonlinear temperature-frequency deviation transfer function model by combining the nonlinear modulation relationship and temperature coefficient;

[0048] Step 4: According to the actual requirements of inverter electromagnetic interference suppression,

[0049] Step 5: Sample the response data of the piezoelectric ceramic in real time, and dynamically adjust the bias voltage based on the calculated temperature-frequency deviation transfer function to perform tuning, so as to obtain a filtering result that meets the constraint conditions.

[0050] The optimal size of the piezoelectric ceramic piece is calculated as follows:

[0051] Step 1.1: For a single piezoelectric ceramic piece, it can be divided into contour vibration mode and thickness vibration mode according to different frequencies. The vibration modes are shown as follows: Figure 1 As shown, p is the polarization direction, U1, U2, and U3 represent the vibration mode types. The corresponding equivalent circuit topology is as follows Figure 2 (a) is the contour vibration mode, (b) is the thickness vibration mode, and (c) is a variety of vibration modes. The DE algorithm-impedance trajectory fitting joint optimization method is used to summarize the impedance resonance Z of the piezoelectric ceramic under the lateral vibration mode in this topology. c Impedance resonance Z under thickness vibration mode r , its impedance expression is:

[0052]

[0053] Among them, C0, C0' are parallel capacitors, C m is the equivalent mechanical capacitance, C m 'Dynamic resonant capacitance, L m , L m ' is the equivalent mechanical inductance, R m , R m 'Equivalent mechanical resistance, j is an imaginary number, j squared is 1, ω is 2πf, f is the resonant frequency;

[0054] The specific constraint conditions set in step 4 are that the interference after suppression is lower than the standard limit with a 5dB margin. The constraint is based on the impedance resonance Z c Resonance with impedance Z r The impedance of the formula and Figure 2 The topology design is based on the actual test spectrum, which requires that the suppressed noise must be 5dB lower than the standard limit, such as EN55022.

[0055] Step 2.1, using a monolithic piezoelectric ceramic as a filter, the fixed-frequency discrete peaks (such as the switching frequency fsw and its integer harmonics nf sw ), set constraints, including: providing sufficiently high insertion loss at the fixed frequency peak to suppress conducted interference; while suppressing the target peak, avoid excessive attenuation in the adjacent frequency bands, and use the DE algorithm-impedance trajectory fitting joint optimization method to optimize Z model (f; l, c, t) are optimized to obtain the optimal size parameters of the piezoelectric ceramic piece, and to achieve the optimal physical size design of the piezoelectric ceramic under a given interference frequency band and suppression amplitude.

[0056] For example, a square piezoelectric ceramic piece with a length and width of 10 mm and a thickness of 2 mm can be calculated to calculate its equivalent circuit (such as Figure 2 The specific parameters and resonant frequencies are as follows:

[0057] Table 1. Equivalent circuit parameters of piezoelectric ceramic capacitors

[0058]

[0059] Table 2. Resonant and anti-resonant frequencies of piezoelectric ceramic capacitors in different vibration modes

[0060]

[0061] Step 1 specifically includes: applying a bias voltage in the vibration direction of the piezoelectric ceramic to obtain a nonlinear modulation relationship between the voltage and the resonant frequency in a single piezoelectric ceramic piece;

[0062] The nonlinear modulation relationship between the voltage and the resonant frequency in the piezoelectric ceramic is shown in the following formula:

[0063]

[0064] Where f0 is the resonant frequency without bias, L is the length of the ceramic, χ and τ are the nonlinear coefficients of the material, V is the voltage applied to each piezoelectric ceramic, and f 0 (V) is the resonant frequency when the bias voltage is V.

[0065] Step 3 is as follows:

[0066] Step 3-1, analyze the temperature compensation, and use the difference between the actual temperature T and the reference ambient temperature T0 (T-T0) to express the linear response. As the difference between T and T0 changes, the output changes linearly, and its square term (T-T0) 2 To express the secondary response, it is used to describe the nonlinear effect of temperature influence, and the temperature-frequency deviation transfer function is set as:

[0067] Tem i (T) = kT 1i (T-T0)+kT 2i (T-T0)2

[0068] Among them, kT li , kT li are the first-order and second-order temperature coefficients. The temperature-frequency deviation curve of the piezoelectric ceramic can be measured experimentally to calibrate the fitting model parameters. T0 is the reference temperature of 25°C, and T is the real-time temperature.

[0069] In step 3-2, the temperature compensation factor is incorporated into the nonlinear modulation relationship between voltage and resonant frequency in a single ceramic to obtain the final relationship function between bias voltage, temperature and ceramic resonance:

[0070]

[0071] In step 3-1, the first-order temperature coefficient kT li and the second-order temperature coefficient kT li The frequency offset data at different temperatures can be measured experimentally, fitted using a quadratic polynomial model, and the parameter values optimized using the least squares method. Finally, the fitting effect can be verified through residual analysis to achieve temperature coefficient calibration.

[0072] The constraints described in step 4 include: target coverage frequency range; single-segment piezoelectric ceramic tuning range; frequency band overlap rate between adjacent segments; multi-segment collaborative tuning synchronization error; maximum safe electric field strength; and ensuring that the filter can meet the suppression requirements during the variable frequency noise suppression process without affecting the performance of other frequency bands.

[0073] Step 5 is as follows:

[0074] Step 5-1: Dynamically sample the inverter EMI noise frequency f in real time noise ;

[0075] Step 5-2, based on the relationship function between the final bias voltage, temperature and ceramic resonance, the bias voltage V is dynamically adjusted in combination with feedforward compensation and closed-loop feedback correction to tune the noise frequency f noise Filtering is performed. Filters effectively suppress the effects of temperature rise, ensuring reliable operation across a wide frequency range and in highly dynamic scenarios. Feedforward compensation uses system models or external signals to predict disturbances and adjust inputs, while closed-loop feedback uses proportional, integral, and differential controllers or robust control to correct errors in real time. Feedforward compensation addresses known disturbances, while feedback correction corrects unknown errors, thereby improving system response speed and accuracy.

[0076] The step 5 of adjusting the bias voltage for tuning specifically includes: applying a DC bias voltage to the bias voltage electrode of the piezoelectric ceramic piece, and covering different frequency bands in sections by adjusting the bias voltage;

[0077] The high-frequency switching operation, nonlinear component characteristics and dynamic adjustment of control strategies of photovoltaic inverters will cause EMI frequency conversion problems. Piezoelectric ceramics are dynamically tuned by applying a DC bias voltage.

[0078] When the piezoelectric ceramic is a single piece, such as Figure 3 As shown, the upper and lower surfaces of the piezoelectric ceramic sheet are piezoelectric filter access electrodes, which can be used to design its initial impedance and resonance f0 in the absence of voltage bias. The left and right surfaces of the piezoelectric ceramic sheet are bias voltage electrodes. By adjusting the bias voltage, different frequency bands can be covered in segments.

[0079] When there are multiple piezoelectric ceramic sheets, they are connected according to the topology, such as Figure 4 In the bias voltage-based segmented integrated piezoelectric ceramic tunable filter shown, the voltage bias electrodes of the piezoelectric ceramic pieces are connected to each other in pairs, and a different bias voltage can be applied to each piezoelectric ceramic piece to achieve multi-resonance peak filtering of noise.

[0080] The present invention provides a method for designing a piezoelectric ceramic EMI filter that takes temperature drift and frequency offset compensation into account. While there are numerous methods and approaches for implementing this technical solution, the aforementioned are merely preferred embodiments of the present invention. It should be noted that those skilled in the art may make numerous improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are also within the scope of protection of the present invention. Components not specified in this embodiment may be implemented using existing technologies.

Claims

1. A piezoelectric ceramic EMI filter design method considering temperature drift frequency offset compensation, characterized in that: The piezoelectric ceramic EMI filter is composed of a piezoelectric ceramic sheet and electrodes; The filtering steps of the piezoelectric ceramic EMI filter are as follows: Step 1, measuring the nonlinear modulation relationship between the voltage and the resonant frequency in the piezoelectric ceramic piece; Step 2: fitting the temperature coefficient based on the relationship between the temperature change of the piezoelectric ceramic and the resonant frequency shift actually measured; Step 3: Capture the effect of temperature change on the resonant frequency behavior of the piezoelectric ceramic tunable filter and build a nonlinear temperature-frequency deviation transfer function model by combining the nonlinear modulation relationship and temperature coefficient; Step 4: Set specific constraints based on the actual inverter electromagnetic interference suppression requirements; Step 5: Sample the response data of the piezoelectric ceramic in real time, and dynamically adjust the bias voltage based on the calculated temperature-frequency deviation transfer function to perform tuning, so as to obtain a filtering result that meets the constraint conditions.

2. The method for designing a piezoelectric ceramic EMI filter considering temperature drift and frequency offset compensation according to claim 1, characterized in that: The optimal size of the piezoelectric ceramic piece is calculated as follows: Step 1.1: Summarize the mapping relationship function Z between the material constitutive parameters and geometric dimensions under multiple vibration modes of piezoelectric ceramics model (f; l, c, t), f is the resonant frequency of the piezoelectric ceramic, l, c, t represent the length, width, and thickness of the piezoelectric ceramic; Step 2.1: Set constraints for the fixed-frequency discrete spikes to be filtered out in the EMI spectrum of the photovoltaic inverter, which are generated by the periodic switching action of the switching devices. These constraints include providing sufficiently high insertion loss at the fixed-frequency spikes to suppress conducted interference. For the cross-scale mapping relationship function Z model (f; l, c, t) are optimized to find the optimal size of the piezoelectric ceramic.

3. The method for designing a piezoelectric ceramic EMI filter considering temperature drift and frequency offset compensation according to claim 1, characterized in that: Step 1 specifically includes: applying a bias voltage in the vibration direction of the piezoelectric ceramic to obtain a nonlinear modulation relationship between the voltage and the resonant frequency in the piezoelectric ceramic; The nonlinear modulation relationship between the voltage and the resonant frequency in the piezoelectric ceramic is shown in the following formula: Where f0 is the resonant frequency without bias, L is the length of the ceramic, χ and τ are the nonlinear coefficients of the material, V is the voltage applied to each piezoelectric ceramic, and f 0 (V) is the resonant frequency when the bias voltage is V.

4. The method for designing a piezoelectric ceramic EMI filter considering temperature drift and frequency offset compensation according to claim 1, characterized in that: In step 2, the first-order temperature coefficient kT li and the second-order temperature coefficient kT li The frequency offset data at different temperatures are measured experimentally, and a quadratic polynomial model is used for fitting. The parameter values are optimized using the least squares method, and the fitting effect is verified by residual analysis to achieve the calibration of the temperature coefficient.

5. The method for designing a piezoelectric ceramic EMI filter considering temperature drift and frequency offset compensation according to claim 4, characterized in that: Step 3 is as follows: Step 3-1, analyze the temperature compensation, and use the difference between the actual temperature T and the reference ambient temperature T0 (T-T0) to express the linear response. As the difference between T and T0 changes, the output changes linearly, and its square term (T-T0) 2 To express the secondary response, it is used to describe the nonlinear effect of temperature influence, and the temperature-frequency deviation transfer function is set as: Tem i (T)=kT 1i (T-T0)+kT 2i (T-T0) 2 Among them, kT li , kT li are the first-order and second-order temperature coefficients, T0 is the reference temperature, and T is the real-time temperature; In step 3-2, the temperature compensation factor is incorporated into the nonlinear modulation relationship between voltage and resonant frequency in a single ceramic to obtain the final relationship function between bias voltage, temperature and ceramic resonance:

6. The method for designing a piezoelectric ceramic EMI filter considering temperature drift and frequency offset compensation according to claim 1, characterized in that: The constraints described in step 4 include: target coverage frequency range; single-segment piezoelectric ceramic tuning range; frequency band overlap rate between adjacent segments; multi-segment collaborative tuning synchronization error; and maximum safe electric field strength.

7. The method for designing a piezoelectric ceramic EMI filter considering temperature drift and frequency offset compensation according to claim 1, characterized in that: Step 5 is as follows: Step 5-1: Dynamically sample the inverter EMI noise frequency f in real time noise ; Step 5-2, based on the relationship function between the final bias voltage, temperature and ceramic resonance, the bias voltage V is dynamically adjusted in combination with feedforward compensation and closed-loop feedback correction to tune the noise frequency f noise Perform filtering.

8. The method for designing a piezoelectric ceramic EMI filter considering temperature drift and frequency offset compensation according to claim 1, characterized in that: The tuning by adjusting the bias voltage in step 5 is specifically as follows: applying a DC bias voltage to the bias voltage electrode of the piezoelectric ceramic piece, and covering different frequency bands in sections by adjusting the bias voltage.

9. The method for designing a piezoelectric ceramic EMI filter considering temperature drift and frequency offset compensation according to claim 1, characterized in that: The electrodes include access electrodes and bias voltage electrodes.

10. The method for designing a piezoelectric ceramic EMI filter considering temperature drift and frequency offset compensation according to claim 1, characterized in that: When there are two or more piezoelectric ceramic sheets, they are connected according to a topological structure.

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