Device and method for detecting and adjusting resonant frequency of resonant bridge of differential transformer

Abstract

The invention relates to the technical field of electronic circuits, in particular to a differential transformer resonant bridge resonant frequency detection and adjustment device and method, a rapid tuning capacitor bridge is composed of a plurality of tuning capacitors, and the resonant frequency is changed by adjusting the capacitance values of the tuning capacitors connected into a circuit; in addition, an analog-to-digital conversion circuit is used for collecting voltage data, and the upper computer is used for directly observing the minimum value of an output voltage peak-to-peak value to judge the resonance state. According to the device and the method provided by the invention, the resonant frequency can be detected, the tuning range can be adjusted as required, the tuning capacitance stepping precision can be adjusted as required, the tuning precision is high, and the resonant frequency adjustment efficiency is improved; meanwhile, the rapid tuning capacitor bridge is used as an independent adjusting unit, so that repeated welding and dewelding of the front-end circuit during the tuning process when the tuning capacitor is changed are effectively avoided, the safety and the reliability of the front-end bridge are ensured, and the engineering application requirements are better met.

Description

Technical Field

[0001] This invention belongs to the field of electronic circuit technology, and in particular relates to a device and method for detecting and adjusting the resonant frequency of a differential transformer resonant bridge. Background Technology

[0002] Differential variable-gap capacitive displacement sensors are used in the front-end electronics of inertial sensors for gravitational wave detection. Resonant bridge noise is a major factor affecting sensor performance and directly impacts accuracy. The resonant bridge exhibits minimal thermal noise and highest sensor accuracy when operating at its resonant frequency. Changes in transformer parameters, cable length, tuning capacitor, stray capacitance, etc., can cause the resonant frequency to deviate from the operating frequency, leading to increased bridge thermal noise and reduced sensor accuracy. Convenient, fast, and accurate methods for determining and adjusting the resonant frequency can effectively improve sensor performance.

[0003] Currently, there are two main methods for determining the resonant frequency. One method is to observe the resonant frequency using a spectrum analyzer. The frequency at which the noise is at its minimum is the current resonant frequency. This method measures the front-end electronic noise, not the noise of the entire system link, and its accuracy is limited by the resolution of the spectrum analyzer. The other method is to change the excitation signal frequency and observe the output voltage value corresponding to the excitation signal at different frequencies. The maximum output voltage is the current resonant frequency. This method requires a high bandwidth from the preamplifier and a smooth gain over a wide bandwidth.

[0004] When the resonant frequency deviates from the operating frequency, the tuning capacitor of the resonant bridge is adjusted to bring the resonant frequency back to the expected state. In existing solutions, the tuning capacitor is located in the front-end electronics circuit. When the resonant frequency deviates, the final tuning capacitor value is determined by repeatedly adjusting the front-end circuit tuning capacitor. However, in this solution, once the entire device is integrated and the system state is fixed, operation becomes difficult, the circuit is not easy to modify, and due to the above limitations, precise resonant frequency adjustment may not even be possible. Summary of the Invention

[0005] In view of this, the present invention aims to provide a device and method for detecting and adjusting the resonant frequency of a differential transformer resonant bridge. When the resonant state is reached at the operating frequency, the circuit noise is minimized. The peak-to-peak value of the output voltage of the complete system link is read by the analog-to-digital conversion circuit to determine the resonant frequency. When the resonant frequency deviates, the resonant frequency is adjusted by the resonant bridge with a tuning capacitor. The resonant frequency adjustment is no longer limited, and the tuning accuracy and efficiency can be guaranteed.

[0006] To achieve the above objectives, the technical solution created by this invention is implemented as follows: A differential transformer resonant bridge resonant frequency detection and adjustment device includes an input circuit, a resonant bridge, a signal conversion circuit, a demodulation circuit, an analog-to-digital conversion circuit, and a host computer. The input circuit converts an excitation signal into an input signal. The resonant bridge includes a fast-tuning capacitor bridge that receives the input signal, which is then transmitted to the signal conversion circuit via a differential transformer. The signal conversion circuit converts the current signal output by the resonant bridge into a voltage signal. The demodulation circuit demodulates the output signal of the signal conversion circuit. The analog-to-digital conversion circuit converts the analog signal output by the demodulation circuit into a digital signal, outputting a voltage value. The host computer receives the voltage value output by the analog-to-digital conversion circuit and determines whether the resonant bridge is in a resonant state based on the time-domain peak-to-peak value of the voltage value. The fast-tuning capacitor bridge includes two arms, each arm containing multiple parallel tuning capacitors. The resonant frequency is changed by adjusting the capacitance values ​​of the tuning capacitors connected in the fast-tuning capacitor bridge.

[0007] Furthermore, in each bridge arm, each tuning capacitor has its corresponding switch. By adjusting the switch, the corresponding tuning capacitor is connected to its respective bridge arm, thereby adjusting the number of tuning capacitors connected to the fast tuning capacitor bridge and thus changing the capacitance value of the tuning capacitors connected to the fast tuning capacitor bridge.

[0008] Furthermore, the resonant bridge also includes a differential transformer; the differential transformer includes two primary windings and one secondary winding, with the two bridge arms respectively connected to the two primary windings, and the secondary winding connected to the signal conversion circuit.

[0009] Furthermore, the input circuit includes a test mass, an excitation signal is applied to the test mass through the electrode plates, and the tolerance signal between the test mass and the upper electrode plate and the tolerance signal between the test mass and the lower electrode plate are converted into current signals, which are then transmitted to the two arms of the fast-tuning capacitor bridge.

[0010] Furthermore, the signal conversion circuit is also used to amplify the voltage signal.

[0011] Furthermore, the device also includes a filtering module connected to the signal conversion circuit, used to filter out external noise in the voltage signal output by the signal conversion circuit.

[0012] Furthermore, the device also includes a digital control circuit, which is connected to an analog-to-digital converter circuit, a signal conversion circuit, a demodulation circuit, and a host computer. Specifically: the digital control circuit controls the analog-to-digital converter circuit to perform signal acquisition and conversion; the digital control circuit controls the amplification gain of the voltage signal by the signal conversion circuit; the digital control circuit controls the demodulation of the demodulation circuit to align the phase of the demodulated signal with the phase of the input signal; and the digital control circuit controls the waveform and frequency of the excitation signal.

[0013] A method for detecting and adjusting the resonant frequency of a differential transformer resonant bridge includes: S1: Construct a differential transformer resonant bridge resonant frequency detection and adjustment device as provided in this invention; S2: Input an excitation signal of a given frequency into the input circuit and control the demodulation circuit to align the phase of the demodulated signal with the demodulated input signal. At the same time, observe the peak-to-peak value of the voltage in the time domain in the host computer. S3: Adjust the capacitance value of the tuning capacitor connected to the fast-tuning capacitor bridge in fixed steps, and observe the change of the peak-to-peak value in the time domain in the host computer until the peak-to-peak value in the time domain reaches its minimum. At this time, the resonant frequency adjustment is completed and the resonant bridge reaches the expected resonant state.

[0014] Furthermore, step S3 includes: S31: Reduce the number of connected tuning capacitors by a fixed step size and observe the change of the time domain peak-to-peak value in real time: if the time domain peak-to-peak value decreases, reduce the number of connected tuning capacitors by a fixed step size until the time domain peak-to-peak value reaches its minimum; otherwise, proceed to step S32. S32: Increase the number of connected tuning capacitors in fixed steps and observe the change of peak-to-peak value in the time domain in real time: if the peak-to-peak value in the time domain decreases, repeat step S32; otherwise, execute step S31 until the peak-to-peak value in the time domain reaches its minimum.

[0015] Compared with the prior art, the present invention can achieve the following beneficial effects: This invention provides a device and method for detecting and adjusting the resonant frequency of a differential transformer resonant bridge. It uses a high-resolution analog-to-digital converter to acquire voltage data and, via a host computer, directly observes the minimum peak-to-peak value of the output voltage to determine the resonant state. The criteria are clear and intuitive, requiring no change to the excitation signal frequency. The circuit gain is stable, and the influence of the accuracy of the testing instrument on the resonant frequency detection is avoided. Regarding resonant frequency adjustment, the fast-tuning capacitor bridge is replaceable, the tuning range can be adjusted as needed, the tuning capacitor can be adjusted in precise steps, and the tuning accuracy is high, improving the efficiency of resonant frequency adjustment. As a separate adjustment unit, the resonant bridge effectively avoids the repeated soldering and desoldering of the front-end circuit during tuning capacitor changes, ensuring the safety and reliability of the front-end bridge and better meeting engineering application requirements. Attached Figure Description

[0016] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1A schematic diagram of the circuit structure of the differential transformer resonant bridge resonant frequency detection and adjustment device described in the embodiment of the present invention; Figure 2 This is a schematic flowchart of the differential transformer resonant bridge resonant frequency detection and adjustment method described in an embodiment of the present invention. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0019] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0020] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0021] The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0022] like Figure 1As shown in the embodiment of the present invention, the differential transformer resonant bridge resonant frequency detection and adjustment device includes an input circuit, a resonant bridge, a signal conversion circuit, a demodulation circuit, an analog-to-digital conversion circuit, and a host computer. The input circuit converts the excitation signal into an input signal. The resonant bridge includes a fast-tuning capacitor bridge, which receives the input signal and transmits it to the signal conversion circuit via a differential transformer. The fast-tuning capacitor bridge includes two arms, each arm containing multiple parallel tuning capacitors. The resonant frequency is changed by adjusting the capacitance values ​​of the tuning capacitors connected in the fast-tuning capacitor bridge. The signal conversion circuit converts the current signal output by the resonant bridge into a voltage signal. The demodulation circuit demodulates the output signal of the signal conversion circuit. The analog-to-digital conversion circuit converts the analog signal output by the demodulation circuit into a digital signal, outputting a voltage value. The host computer receives the voltage value output by the analog-to-digital conversion circuit and determines whether the resonant bridge is in a resonant state based on the peak-to-peak value of the voltage value in the time domain.

[0023] In this embodiment of the invention, the signal conversion circuit consists of a transimpedance amplifier and an AC amplifier circuit. The transimpedance amplifier converts the current signal into a voltage signal, and the AC amplifier circuit amplifies the voltage signal. The analog-to-digital conversion circuit is implemented using an analog-to-digital converter (A / D converter). The signal conversion circuit, demodulation circuit, and analog-to-digital conversion circuit in this embodiment of the invention all employ existing circuitry.

[0024] In some embodiments, each tuning capacitor has a corresponding switch. By adjusting the switch, the corresponding tuning capacitor is connected to its respective bridge arm, thereby adjusting the number of tuning capacitors connected to the fast-tuning capacitor bridge. Furthermore, each tuning capacitor and its corresponding switch are connected in series. When the switch is closed, the corresponding tuning capacitor is connected to the circuit, thus enabling the toggle switch to adjust the number of tuning capacitors connected to the fast-tuning capacitor bridge. The number of tuning capacitors in the two bridge arms and the capacitance value of each tuning capacitor are adaptively adjusted according to requirements and actual conditions.

[0025] In this embodiment of the invention, each bridge arm includes four parallel tuning capacitors and four switches connected in series with the four tuning capacitors. Specifically, the first bridge arm includes tuning capacitors C1, C2, C3, and C4 connected in parallel, and also includes switches K1, K2, K3, and K4 connected in series with tuning capacitor C1, K2, K3, and K4; the second bridge arm includes tuning capacitors C5, C6, C7, and C8 connected in parallel, and also includes switches K5, K6, K7, and K8 connected in series with tuning capacitor C8. The capacitance value of each tuning capacitor is determined by the tuning precision. For example, if a tuning precision of 1pF is required, tuning capacitors of 1pF, 2pF, 3pF, and 5pF can be selected; if a tuning precision of 5pF is required, tuning capacitors of 5pF, 10pF, 10pF, and 20pF can be selected. Tuning capacitors can be combined to achieve the required capacitance value according to the step precision, and more groups and combinations can be added as needed.

[0026] In some embodiments, the differential transformer includes two primary windings and one secondary winding, with two bridge arms respectively connected to the two primary windings, and the secondary winding connected to a signal conversion circuit.

[0027] In this embodiment of the invention, the primary windings L1 and L2 of the differential transformer are connected to the two bridge arms respectively, and the secondary winding L3 is connected to the signal conversion circuit. Because the resonant bridge has extremely high sensitivity, it is also susceptible to external interference (such as temperature drift, power fluctuations, and electromagnetic noise). The differential output characteristics of the differential transformer can suppress these interferences and perfectly match the balance characteristics of the bridge. Therefore, this invention combines the differential transformer with a fast-tuning capacitor bridge to significantly suppress interference, ultimately enabling the resonant bridge to achieve high-precision and high-stability physical quantity measurement.

[0028] In some embodiments, the input circuit includes a test mass (TM). An excitation signal is applied to the test mass through electrode plates, and the tolerance signals between the test mass and the upper electrode plate and between the test mass and the lower electrode plate are converted into current signals, which are then transmitted to the two arms of the fast-tuning capacitor bridge, respectively. When the resonant bridge is in a resonant state, the thermal noise of the resonant bridge reaches its minimum value, at which point the sensor performance is optimal.

[0029] In some embodiments, the apparatus provided by the present invention further includes a digital control circuit, which is connected to an analog-to-digital converter (ADC), a signal conversion circuit, a demodulation circuit, and a host computer. Specifically: the digital control circuit controls the ADC to perform signal acquisition and conversion; the digital control circuit controls the amplification gain of the voltage signal by the signal conversion circuit; the digital control circuit controls the demodulation of the demodulation circuit, aligning the phase of the demodulated signal with the phase of the input signal; and the digital control circuit controls the waveform and frequency of the excitation signal. In this embodiment, the digital control circuit sends control signals for signal acquisition and conversion to the ADC, thereby controlling the ADC to perform signal acquisition and conversion; the digital control circuit sends gain control signals to the signal conversion circuit, thereby controlling the amplification gain of the voltage signal by the signal conversion circuit; and the digital control circuit sends demodulation control signals to the demodulation circuit, thereby controlling the start and stop of demodulation by the demodulation circuit, thereby aligning the phase of the demodulated signal with the phase of the input signal.

[0030] This invention also provides a method for detecting and adjusting the resonant frequency of a differential transformer resonant bridge, combined with... Figure 1 and Figure 2 The methods include: S1: Construct a differential transformer resonant bridge resonant frequency detection and adjustment device as provided in this invention.

[0031] In this embodiment of the invention, step S1 includes: confirming the expected operating frequency of the resonant bridge, estimating the required tuning capacitor size for the resonant state based on the known inductance value of the differential transformer and the cable length, confirming the tuning accuracy, and welding the fast tuning capacitor bridge. Specifically, the resonant frequency is estimated using the following formula: ; Where f represents the resonant frequency, L represents the inductance of the differential transformer, and C represents the capacitance at the resonant state, including the capacitance on the fast-tuning capacitor bridge, the capacitance of the cable connecting the electrode plate and the fast-tuning capacitor bridge, and other stray capacitances.

[0032] S2: Input an excitation signal of a given frequency to the input circuit and control the demodulation circuit to align the phase of the demodulated signal with the demodulated input signal. At the same time, observe the peak-to-peak value of the voltage in the time domain in the host computer.

[0033] S3: Adjust the capacitance value of the tuning capacitor connected to the fast-tuning capacitor bridge in fixed steps, and observe the change of the peak-to-peak value in the time domain in the host computer until the peak-to-peak value in the time domain reaches its minimum. At this time, the resonant frequency adjustment is completed and the resonant bridge reaches the expected resonant state.

[0034] The fixed step size is selected based on application requirements. A higher fixed step size results in higher resonant frequency adjustment accuracy. The capacitance value of the tuning capacitor is selected according to the resonant frequency accuracy requirements, and the minimum capacitance value represents the step accuracy. For example, if the minimum capacitance value is 1pF, connecting it to the circuit increases the tuning capacitor by 1pF, and disconnecting it decreases the tuning capacitor by 1pF. In this case, the minimum step accuracy is 1pF.

[0035] In some embodiments, step S3 includes: S31: Reduce the number of connected tuning capacitors by a fixed step size and observe the change of the time domain peak-to-peak value in real time: if the time domain peak-to-peak value decreases, reduce the number of connected tuning capacitors by a fixed step size until the time domain peak-to-peak value reaches its minimum; otherwise, proceed to step S32. S32: Increase the number of connected tuning capacitors in fixed steps and observe the change of peak-to-peak value in the time domain in real time: if the peak-to-peak value in the time domain decreases, repeat step S32; otherwise, execute step S31 until the peak-to-peak value in the time domain reaches its minimum.

[0036] In step S3, the capacitors on both bridge arms can be adjusted simultaneously with the same fixed step size, which can ensure the symmetry of the resonant bridge while adjusting the resonant frequency. Alternatively, the capacitors on each bridge arm can be adjusted individually to adjust the symmetry of the resonant bridge.

[0037] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0038] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A device for detecting and adjusting the resonant frequency of a differential transformer resonant bridge, characterized in that, It includes input circuits, resonant bridges, signal conversion circuits, demodulation circuits, analog-to-digital conversion circuits, and a host computer, among which: The input circuit is used to convert the excitation signal into an input signal; the resonant bridge includes a fast-tuning capacitor bridge, which receives the input signal and then transmits it to the signal conversion circuit via a differential transformer; the signal conversion circuit is used to convert the current signal output by the resonant bridge into a voltage signal; the demodulation circuit is used to demodulate the output signal of the signal conversion circuit; the analog-to-digital converter is used to convert the analog signal output by the demodulation circuit into a digital signal and output a voltage value; the host computer is used to receive the voltage value output by the analog-to-digital converter and determine whether the resonant bridge is in a resonant state based on the time-domain peak-to-peak value of the voltage value. The fast-tuning capacitor bridge includes two arms, each arm including multiple tuning capacitors connected in parallel. The resonant frequency is changed by adjusting the capacitance value of the tuning capacitors connected in the fast-tuning capacitor bridge.

2. The differential transformer resonant bridge resonant frequency detection and adjustment device according to claim 1, characterized in that, In each bridge arm, each tuning capacitor has its corresponding switch. By adjusting the switch, the corresponding tuning capacitor is connected to its respective bridge arm, thereby adjusting the number of tuning capacitors connected to the fast tuning capacitor bridge and thus changing the capacitance value of the tuning capacitors connected to the fast tuning capacitor bridge.

3. The differential transformer resonant bridge resonant frequency detection and adjustment device according to claim 1, characterized in that, The resonant bridge also includes a differential transformer; The differential transformer includes two primary windings and one secondary winding. Two bridge arms are respectively connected to the two primary windings, and the secondary winding is connected to the signal conversion circuit.

4. The differential transformer resonant bridge resonant frequency detection and adjustment device according to claim 1, characterized in that, The input circuit includes a test mass, the excitation signal is applied to the test mass through the electrode plate, and the tolerance signal between the test mass and the upper electrode plate and the tolerance signal between the test mass and the lower electrode plate are converted into current signals, which are then transmitted to the two arms of the fast-tuning capacitor bridge.

5. The differential transformer resonant bridge resonant frequency detection and adjustment device according to claim 1, characterized in that, The signal conversion circuit is also used to amplify the voltage signal.

6. The differential transformer resonant bridge resonant frequency detection and adjustment device according to claim 1, characterized in that, The device also includes a filtering module connected to the signal conversion circuit, used to filter out external noise in the voltage signal output by the signal conversion circuit.

7. The differential transformer resonant bridge resonant frequency detection and adjustment device according to claim 6, characterized in that, The device further includes a digital control circuit, which is connected to the analog-to-digital conversion circuit, the signal conversion circuit, the demodulation circuit, and the host computer, wherein: The digital control circuit controls the analog-to-digital conversion circuit to perform signal acquisition and conversion; The digital control circuit controls the amplification gain of the voltage signal by the signal conversion circuit; The digital control circuit controls the demodulation of the demodulation circuit, so that the phase of the demodulation signal controlling the demodulation circuit is aligned with the phase of the input signal. The digital control circuit controls the waveform and frequency of the excitation signal.

8. A method for detecting and adjusting the resonant frequency of a differential transformer resonant bridge, characterized in that, include: S1: Construct the differential transformer resonant bridge resonant frequency detection and adjustment device as described in any one of claims 1 to 7; S2: Input an excitation signal of a given frequency to the input circuit and control the demodulation circuit to align the phase of the demodulated signal with the demodulated input signal, while observing the time-domain peak-to-peak value of the voltage value in the host computer. S3: Adjust the capacitance value of the tuning capacitor connected to the fast tuning capacitor bridge in fixed step size, and observe the change of the time domain peak-to-peak value in the host computer until the time domain peak-to-peak value reaches the minimum. At this time, the resonant frequency adjustment is completed, and the resonant bridge reaches the expected resonant state.

9. The method for detecting and adjusting the resonant frequency of a differential transformer resonant bridge according to claim 8, characterized in that, Step S3 includes: S31: Reduce the number of connected tuning capacitors by a fixed step size and observe the change of the time-domain peak-to-peak value in real time: if the time-domain peak-to-peak value decreases, reduce the number of connected tuning capacitors by a fixed step size until the time-domain peak-to-peak value reaches its minimum; otherwise, proceed to step S32. S32: Increase the number of connected tuning capacitors by a fixed step size and observe the change of the time-domain peak-to-peak value in real time: if the time-domain peak-to-peak value decreases, repeat step S32; otherwise, execute step S31 until the time-domain peak-to-peak value reaches its minimum.

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