Frequency selection circuit for self-excited ultrasonic generator

Abstract

The utility model provides a frequency selecting circuit for a self-excited ultrasonic generator, which comprises a first active band-pass filtering module, a second active band-pass filtering module and a phase shifting module, and the active band-pass filtering module comprises a first operational amplifier, a second operational amplifier and a third operational amplifier. The phase shift module comprises a second slide rheostat and a phase correction capacitor, output signals of the first active band-pass filtering module and the second active band-pass filtering module are connected with a slip sheet of the second slide rheostat, and the second slide rheostat and the phase correction capacitor are connected in parallel. An output signal is obtained by the second slide rheostat and the other end of the phase correction capacitor; a double-tuning loop is adopted for frequency selection, a final output signal is formed by adding output signals of two parallel active band-pass filters, the quality factor (Q value) of the two band-pass filters is properly designed by changing the resistance value of the slide rheostat, the center frequency of the two band-pass filters is staggered, accurate and stable frequency characteristics can be obtained, and readjustment is not needed.

Description

Technical Field

[0001] The utility model relates to the technical field of frequency selection, in particular to a frequency selection circuit for a self-excited ultrasonic generator. Background Art

[0002] In tool-type ultrasonic transducers, the tool head is often complex in shape due to practicality. The complex shape brings multiple vibration modes and multiple resonant frequencies. Usually only one frequency among the multiple resonant frequencies is practical. The self-excited ultrasonic generator that drives this transducer must have a certain frequency selection capability to suppress all useless resonant frequencies, avoid wrong frequencies, and select the correct frequency for work.

[0003] The existing frequency selection method uses the L value in the LC tuning loop to find the best operating frequency. The operator adjusts a variable inductor while observing the ammeter on the panel. When the ammeter indicates the minimum value, it is considered that the best operating frequency has been found.

[0004] As mentioned earlier, the phase difference between signal C and signal A is φ1. Different operating frequencies will correspond to different φ1 values. For the sake of description, the φ1 value corresponding to the optimal operating frequency is called "optimal φ1". When the operator finds the optimal operating frequency, he actually adjusts the variable inductor so that the frequency selector has an "optimal φ2" with the same absolute value and opposite sign as the "optimal φ1" at the optimal operating frequency.

[0005] However, once the operator has adjusted the variable inductor to find the best operating frequency, it is not a permanent solution. After working for a period of time, the temperature of the transducer will gradually increase, and its resonant frequency will gradually decrease. At the new frequency, the φ2 of the frequency selector is no longer optimal. Figure 2 As shown, the φ2 curve of the single LC tuning circuit used in the existing frequency selection method is not a horizontal line segment within the practical frequency range, but a line segment oblique to the frequency axis, that is, φ2 changes with frequency. When the transducer frequency changes, the operator needs to readjust the variable inductor to allow the frequency selector to maintain the original optimal φ2 value at the new optimal operating frequency.

[0006] Therefore, the problems existing in the existing frequency selection method are:

[0007] 1. The inductor used for frequency selection needs to be adjusted frequently, which is troublesome to operate and the user needs to have certain professional knowledge;

[0008] 2. It is not suitable for products supplied to the general public without professional knowledge. Utility Model Content

[0009] The utility model aims to provide a frequency selection circuit for a self-excited ultrasonic generator.

[0010] In order to achieve the above purpose, the technical solution of the utility model is:

[0011] A frequency selection circuit for a self-excited ultrasonic generator, characterized in that the frequency selection circuit includes a signal amplification module, a power amplification module, an impedance matching module, a feedback signal sampling module and a frequency selection phase shifting module connected in sequence, the signal amplification module is controlled by a single chip microcomputer, the frequency selection phase shifting module includes a first active bandpass filtering module, a second active bandpass filtering module and a phase shifting module, the first active bandpass filtering module includes a first operational amplifier, a second operational amplifier and a third operational amplifier, the positive phase input terminals of the first operational amplifier, the second operational amplifier and the third operational amplifier are connected to the feedback signal, the output terminal of the first operational amplifier is connected to the slider of a first sliding rheostat, and one end of the first sliding rheostat is connected to the inverting input terminal of the first operational amplifier The other end of the first sliding rheostat is connected to the inverting input end of the second operational amplifier, the output end of the second operational amplifier is connected to the inverting input end of the third operational amplifier, the output end of the third operational amplifier is connected to the inverting input end of the first operational amplifier, the output end of the second operational amplifier is used as the output signal of the first active band-pass filtering module, the second active band-pass filtering module has the same structure as the first active band-pass filtering module, the phase shift module includes a second sliding rheostat and a phase correction capacitor, the output signals of the first active band-pass filtering module and the second active band-pass filtering module are connected to the slider of the second sliding rheostat, the second sliding rheostat and the phase correction capacitor are connected in parallel, and the output signal is obtained from the other end of the second sliding rheostat and the phase correction capacitor.

[0012] Furthermore, the signal amplification module includes an input signal amplification module and an output signal amplification module, the input signal amplification module includes a driving chip, the power amplification module includes a first MOSFET and a second MOSFET, the first MOSFET and the second MOSFET are connected in series, and the driving chip drives the first MOSFET and the second MOSFET respectively, and the output signal amplification module includes a fourth operational amplifier, the other end of the phase correction capacitor and the second sliding resistor is connected to the inverting input end of the fourth operational amplifier, and the amplified output signal is obtained from the output end of the fourth operational amplifier.

[0013] Furthermore, the frequency selection circuit includes a power supply current sampling module, which includes a first transformer and a transistor, the turns ratio of the primary and secondary of the first transformer is 1:2, pin 1 of the primary of the first transformer is connected to a 3.7V voltage, pin 2 of the primary of the first transformer is connected to the drain of the first MOS tube, pin 3 of the secondary of the first transformer is connected to the collector of the transistor, and the base of the transistor is connected to the input end of the signal amplification module.

[0014] Furthermore, the impedance matching module includes a second transformer, the second transformer includes a first coil, a second coil and a third coil, the first coil serves as the primary of the second transformer, the second coil and the third coil are connected in series as the secondary of the second transformer, the turns ratio of the first coil, the second coil and the third coil is 3:2:5, the 3rd pin of the second coil and the 5th pin of the third coil are respectively connected to the two ends of the transducer load, and the 4th pins of the second coil and the third coil output feedback signals to the frequency selection and phase shifting module.

[0015] Furthermore, the frequency selection circuit also includes a power management module, which includes a boost IC. The boost IC is controlled by a single-chip microcomputer, and the input terminal of the boost IC is connected to a 3.7V voltage.

[0016] The utility model adopts a double tuning circuit for frequency selection, and the final output signal is formed by adding the output signals of two parallel active bandpass filters. By changing the resistance value of the sliding rheostat and appropriately designing the quality factors (Q values) of the two bandpass filters, the center frequencies of the two bandpass filters are staggered, and accurate and stable frequency characteristics can be obtained without re-adjustment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a system structure diagram of the utility model;

[0018] Figure 2 It is a schematic diagram of the process of frequency selection and phase shifting of the utility model;

[0019] Figure 3 A circuit diagram for the implementation of the utility model;

[0020] Figure 4 This is a characteristic diagram of the dual-tuning circuit of the utility model.

[0021] Reference numerals:

[0022] 1 signal generator, 2 signal amplification module, 3 power amplification module, 4 impedance matching module,

[0023] 5 transducer load, 6 feedback signal sampling module, 7 frequency selection phase shift module,

[0024] 71 first active bandpass filter module, 72 second active bandpass filter module, 73 phase shift module,

[0025] 8 power management module, 9 power current sampling module,

[0026] U1 single chip microcomputer, U2 driver chip, U3 boost IC, Q transistor,

[0027] T1 first transformer, T2 second transformer, Ri sampling resistor, Rf feedback resistor,

[0028] MOS1 is the first MOS tube, MOS2 is the second MOS tube,

[0029] A1 is the first operational amplifier, A2 is the second operational amplifier,

[0030] A3 is the third operational amplifier, A4 is the fourth operational amplifier,

[0031] Rp1 is the first sliding resistor, Rp2 is the second sliding resistor, C70 is the phase correction capacitor,

[0032] N1 is the first coil, N2 is the second coil, and N3 is the third coil. DETAILED DESCRIPTION

[0033] The technical solution of the utility model will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0034] The utility model discloses a frequency selection circuit for a self-excited ultrasonic generator, such as Figure 1 As shown, the frequency selection circuit includes a signal amplification module 2, a power amplification module 3, an impedance matching module 4, a feedback signal sampling module 6 and a frequency selection phase shift module 73 which are connected in sequence. The signal amplification module 2 is controlled by the single chip microcomputer U1, and the input end of the signal amplification module 2 is connected to the signal of the signal generator 1.

[0035] like Figure 3 As shown, the frequency-selective phase-shifting module 73 includes a first active band-pass filtering module 71, a second active band-pass filtering module 72 and a phase-shifting module 73. The first active band-pass filtering module 71 includes a first operational amplifier A1, a second operational amplifier A2 and a third operational amplifier A3. The positive-phase input terminals of the first operational amplifier A1, the second operational amplifier A2 and the third operational amplifier A3 are connected to the feedback signal.

[0036] The first operational amplifier A1, the second operational amplifier A2 and the third operational amplifier A3 adopt TPH2504, the first operational amplifier A1 is used as a common-phase proportional amplifier, the output end of the first operational amplifier A1 is connected to the slider of the first sliding rheostat Rp1, one end of the first sliding rheostat Rp1 is connected to the inverting input end of the first operational amplifier A1, the other end of the first sliding rheostat Rp1 is connected to the inverting input end of the second operational amplifier A2, the output end of the second operational amplifier A2 is connected to the inverting input end of the third operational amplifier A3, the output end of the third operational amplifier A3 is connected to the inverting input end of the first operational amplifier A1, the output end of the second operational amplifier A2 is used as the output signal of the first active bandpass filtering module 71, and the second operational amplifier A2 and the third operational amplifier A3 are used as voltage followers.

[0037] Among them, the total resistance of the first sliding resistor Rp1 is 100KΩ, the sampling resistor Ri of the first operational amplifier A1 is fixed at 3.3KΩ, and the feedback resistor of the first operational amplifier A1 is a fixed 3.3KΩ feedback resistor Rf + a variable resistance of the first sliding resistor Rp1. The total resistance is changed by adjusting the resistance of the first sliding resistor Rp1 to change the amplification factor of the first operational amplifier A1.

[0038] The second active band-pass filter module 72 has the same structure as the first active band-pass filter module 71 .

[0039] The phase shift module 73 includes a second sliding rheostat Rp2 and a phase correction capacitor C70. The output signals of the first active bandpass filter module 71 and the second active bandpass filter module 72 are both connected to the slider of the second sliding rheostat Rp2. The resistance of the second sliding rheostat Rp2 is 500KΩ. The second sliding rheostat Rp2 is connected in parallel with the phase correction capacitor C70, and the output signal is obtained from the other end of the second sliding rheostat Rp2 and the phase correction capacitor C70.

[0040] The signal amplification module 2 includes an input signal amplification module 2 and an output signal amplification module 2. The input signal amplification module 2 includes a driving chip U2. The driving chip U2 adopts EG2104S. The power amplification module 3 includes a first MOS tube MOS1 and a second MOS tube MOS2. The first MOS tube MOS1 and the second MOS tube MOS2 are connected in series. The driving chip U2 drives the first MOS tube MOS1 and the second MOS tube MOS2 respectively. The output signal amplification module 2 includes a fourth operational amplifier A4. The other end of the phase correction capacitor C70 and the second sliding rheostat Rp2 is connected to the inverting input end of the fourth operational amplifier A4. The amplified output signal is obtained from the output end of the fourth operational amplifier A4. The fourth operational amplifier A4 adopts TPH2502.

[0041] The frequency selection circuit includes a power supply current sampling module 9, which includes a first transformer T1 and a transistor. The turns ratio between the primary and secondary of the first transformer T1 is 1:2. Pin 1 of the primary of the first transformer T1 is connected to a 3.7V voltage. Pin 2 of the primary of the first transformer T1 is connected to the drain of the first MOS tube MOS1. Pin 3 of the secondary of the first transformer T1 is connected to the collector of the transistor Q. The base of the transistor Q is connected to the input end of the signal amplification module 2. The transistor Q uses 9014.

[0042] The impedance matching module 4 includes a second transformer T2, which includes a first coil N1, a second coil N2 and a third coil N3. The first coil N1 serves as the primary of the second transformer T2, and the second coil N2 and the third coil N3 are connected in series as the secondary of the second transformer T2. The turns ratio of the first coil N1, the second coil N2 and the third coil N3 is 3:2:5. Pin 3 of the second coil N2 and pin 5 of the third coil N3 are respectively connected to the two ends of the transducer load 5, and pin 4 of the second coil N2 and the third coil N3 output feedback signals to the frequency selection and phase shifting module 73.

[0043] The frequency selection circuit also includes a power management module 8, which includes a boost IC U3. The boost IC U3 is controlled by the single-chip microcomputer U1. The input terminal of the boost IC U3 is connected to a 3.7V voltage. The boost IC U3 uses SX1308.

[0044] like Figure 2 As shown, the utility model adopts a double tuning circuit for frequency selection. The frequency selection signal is formed by adding the output signals of the first active bandpass filter module 71 and the second active bandpass filter module 72 connected in parallel. The resistance values ​​of the sliding resistors of the first active bandpass filter module 71 and the second active bandpass filter module 72 are adjusted to change the quality factors Q of the two bandpass filters. The center frequencies of the two bandpass filters are appropriately staggered to obtain Figure 4 The frequency characteristics are shown.

[0045] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model, rather than to limit it. Although the utility model has been described in detail with reference to the aforementioned embodiments, ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solution deviate from the scope of the technical solution of the embodiments of the utility model.

Claims

1. A frequency selection circuit for a self-excited ultrasonic generator, characterized in that: The frequency selection circuit includes a signal amplification module, a power amplification module, an impedance matching module, a feedback signal sampling module and a frequency selection phase shifting module which are connected in sequence. The signal amplification module is controlled by a single chip microcomputer. The frequency selection phase shifting module includes a first active bandpass filtering module, a second active bandpass filtering module and a phase shifting module. The first active bandpass filtering module includes a first operational amplifier, a second operational amplifier and a third operational amplifier. The positive phase input terminal of the first operational amplifier is connected to the feedback signal. The output terminal of the first operational amplifier is connected to the slider of the first sliding rheostat. One end of the first sliding rheostat is connected to the inverting input terminal of the first operational amplifier. The other end of the first sliding rheostat is connected to the inverting input terminal of the second operational amplifier. The output end of the second operational amplifier is connected to the inverting input end of the third operational amplifier, the output end of the third operational amplifier is connected to the inverting input end of the first operational amplifier, the output end of the second operational amplifier is used as the output signal of the first active band-pass filtering module, the second active band-pass filtering module has the same structure as the first active band-pass filtering module, the phase shifting module includes a second sliding rheostat and a phase correction capacitor, the output signals of the first active band-pass filtering module and the second active band-pass filtering module are connected to the slider of the second sliding rheostat, the second sliding rheostat and the phase correction capacitor are connected in parallel, and the output signal is obtained from the other end of the second sliding rheostat and the phase correction capacitor.

2. The frequency selection circuit for a self-excited ultrasonic generator according to claim 1, characterized in that: The signal amplification module includes an input signal amplification module and an output signal amplification module, the input signal amplification module includes a driving chip, the power amplification module includes a first MOSFET and a second MOSFET, the first MOSFET and the second MOSFET are connected in series, and the driving chip drives the first MOSFET and the second MOSFET respectively, the output signal amplification module includes a fourth operational amplifier, the other end of the phase correction capacitor and the second sliding rheostat is connected to the inverting input end of the fourth operational amplifier, and the amplified output signal is obtained from the output end of the fourth operational amplifier.

3. The frequency selection circuit for a self-excited ultrasonic generator according to claim 2, characterized in that: The frequency selection circuit includes a power supply current sampling module, which includes a first transformer and a transistor. The turns ratio between the primary and secondary of the first transformer is 1:

2. Pin 1 of the primary of the first transformer is connected to a 3.7V voltage. Pin 2 of the primary of the first transformer is connected to the drain of the first MOS tube. Pin 3 of the secondary of the first transformer is connected to the collector of the transistor. The base of the transistor is connected to the input end of the signal amplification module.

4. The frequency selection circuit for a self-excited ultrasonic generator according to claim 1, characterized in that: The impedance matching module includes a second transformer, which includes a first coil, a second coil and a third coil. The first coil serves as the primary of the second transformer, and the second coil and the third coil are connected in series as the secondary of the second transformer. The turns ratio of the first coil, the second coil and the third coil is 3:2:

5. Pin 3 of the second coil and pin 5 of the third coil are respectively connected to the two ends of the transducer load, and pins 4 of the second coil and the third coil output feedback signals to the frequency selection and phase shifting module.

5. The frequency selection circuit for a self-excited ultrasonic generator according to claim 1, characterized in that: The frequency selection circuit also includes a power management module, which includes a boost IC. The boost IC is controlled by a single-chip microcomputer, and an input terminal of the boost IC is connected to a 3.7V voltage.

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