CN-121972388-A - Phase closed-loop adjusting circuit of piezoelectric ultrasonic transducer

CN121972388ACN 121972388 ACN121972388 ACN 121972388ACN-121972388-A

Abstract

The invention discloses a phase closed-loop regulating circuit of a piezoelectric ultrasonic transducer, which relates to the technical field of ultrasonic driving, improves the existing current judging method, realizes direct detection of alternating voltage signals based on a phase discrimination circuit, does not need to be converted into direct voltage signals, avoids time delay of alternating current-direct current conversion process, adopts non-isolated voltage sampling, avoids phase advance caused by a voltage division capacitor, avoids phase lag caused by a transformer inductance, has good universality, can work under transducers with different powers, can realize driving in use occasions of various piezoelectric transducers, and has larger cost advantage compared with a realization mode with higher software participation.

Inventors

GAO JIE
WEI LONG
WANG SHAOCHEN
ZHENG DAWEI

Assignees

安徽汉先智能科技有限公司

Dates

Publication Date: 20260505
Application Date: 20251216

Claims (10)

1. The phase closed-loop adjusting circuit of the piezoelectric ultrasonic transducer is characterized by comprising a voltage acquisition circuit, a current acquisition circuit and a phase discrimination circuit; the voltage acquisition circuit is used for acquiring the voltage UAC at two ends of the piezoelectric ultrasonic transducer; The current acquisition circuit is used for acquiring the current IAC flowing through the piezoelectric ultrasonic transducer; The phase detection circuit is used for detecting the phase difference phi of the voltage UAC and the current IAC of the piezoelectric ultrasonic transducer and converting the phase difference phi into a voltage VPHS which is changed in proportion, wherein VPHS is maximum when phi=0 DEG, and VPHS is minimum when phi=180 DEG; The singlechip adjusts the output frequency based on the voltage VPHS, so that the voltage VPHS changes in the rising direction, and when VPHS reaches the maximum value, the transducer resonates, and the voltage and the current are in phase.
2. The phase closed loop regulation circuit of claim 1 wherein the phase discrimination circuit is based on a phase discrimination chip, wherein the voltage UAC and the current IAC are respectively filtered and then input into two input channels of the phase discrimination chip, and the phase discrimination chip detects the phase difference phi of the voltage UAC and the current IAC and outputs a voltage VPHS which changes proportionally.
3. The phase closed-loop adjusting circuit according to claim 2, wherein the voltage UAC is input to a first input channel of the phase-discriminating chip through a capacitor CA1, an offset voltage adjusting pin corresponding to the first input channel is grounded through a capacitor CA4, the voltage IAC is input to a second input channel of the phase-discriminating chip through a capacitor CA5, and an offset voltage adjusting pin corresponding to the second input channel is grounded through a capacitor CA 6.
4. The phase closed loop regulation circuit of claim 2 wherein the voltage UAC, the current IAC are grounded through pull-down resistors RA1, RA2, respectively.
5. The phase closed-loop adjusting circuit according to claim 1, wherein the voltage acquisition circuit is based on a differential operational amplifier, two ends of the piezoelectric ultrasonic transducer are connected to a non-inverting input end and an inverting input end of the differential operational amplifier respectively after voltage division and current limiting through resistors, and an output end of the differential operational amplifier is connected to the inverting input end through a feedback resistor.
6. The phase closed-loop adjusting circuit according to claim 5, wherein a voltage dividing resistor RG1 and a voltage dividing resistor RG2 are connected in series at two ends of the piezoelectric ultrasonic transducer, and two ends of the resistor RG2 are connected to an inverting input end and a non-inverting input end of the differential operational amplifier through a current limiting resistor RG3 and a current limiting resistor RG4 respectively.
7. The phase closed-loop adjusting circuit according to claim 1, wherein the current collecting circuit uses a sampling resistor and a mutual inductor to collect current, wherein the sampling resistor RF1 is connected in series with two ends of the piezoelectric ultrasonic transducer, the mutual inductor senses voltage drop at two ends of the sampling resistor RF1, and outputs a current signal proportional to the current to be measured, and the current signal is converted into a voltage signal through the resistor RF 2.
8. The phase closed loop regulation circuit of claim 7 wherein the voltage signal across resistor RF2 is input to a differential amplifier circuit which outputs a current IAC.
9. The phase closed loop regulation circuit of claim 1 wherein the voltage VPHS is input to the single chip microcomputer via the ADC acquisition circuit after passing through the op amp circuit.
10. An ultrasonic drive circuit for a piezoelectric ultrasonic transducer, comprising the phase closed-loop adjustment circuit according to any one of claims 1 to 9.

Description

Phase closed-loop adjusting circuit of piezoelectric ultrasonic transducer Technical Field The invention relates to the technical field of ultrasonic driving, in particular to a phase closed-loop adjusting circuit of a piezoelectric ultrasonic transducer. Background The piezoelectric ultrasonic transducer is an energy converter which converts electric energy into mechanical energy by using piezoelectric ceramics and can convert alternating electric signals into mechanical vibration with specific frequency and amplitude. When the piezoelectric ultrasonic transducer is driven, the voltage phase is consistent with the current phase, so that the output efficiency is maximized. Therefore, the accuracy of phase detection is the core of efficient and stable operation of the piezoelectric ultrasonic transducer, and directly determines whether the system can track the resonant frequency in real time, so that the optimal conversion of energy is realized. Conventional ultrasonic drive circuits generally detect a phase using a pulse conversion method or a voltage judgment method. The pulse conversion method converts sinusoidal voltage/current signals at two ends of the transducer into pulse waves with the same frequency through a comparator, and then a digital logic circuit (such as an FPGA) is used for measuring the phase difference of two paths of pulses, but the following defects exist: 1. Switching distortion-the on threshold and response time of the electronics (e.g., comparator) can cause the generated pulse wave phase to lag or lead relative to the original sinusoidal signal, resulting in distortion. 2. Phase offset, namely, parasitic capacitance, inductance and other distribution parameters in a detection circuit can introduce extra unstable phase lag, and the lag changes along with frequency and amplitude, so that accurate compensation is difficult, and a measured value and a true value deviate. The voltage judging method is based on the characteristics of the transducer that the impedance is minimum when resonating and the voltage at two ends is lowest when the current is constant, and indirectly judges whether the resonance is achieved or not by detecting the voltage amplitude (usually converted into direct current) of the transducer, but the following defects exist: 1. The delay is introduced from alternating current to direct current, the inherent response time exists in the process of converting the effective value of a high-frequency alternating current signal into a direct current signal (such as an RMS-DC conversion chip or a precise rectification circuit), and the feedback delay of a system is caused, so that the real-time performance is poor; 2. inductive measurement brings about phase differences, namely, because the driving voltage is high and needs to be isolated from a control loop, the inductive measurement is usually carried out by using an isolation op-amp or a linear optocoupler, and the isolation devices have propagation delay and can introduce additional phase errors. Of course, the pulse conversion method and the voltage judgment method are both phase detection methods with low software participation. With the improvement of the software participation, the method can also have the realization modes of a software phase-locked loop (SPLL) technology, a digital processing method based on Hilbert (Hilbert) transformation, a combined controller based on DSP+FPGA, a dynamic compensation method and the like, and can realize higher precision. However, as the software engagement increases, the implementation cost of the solution increases, and the specific analysis is as follows: 1. The software phase-locked loop (SPLL) technology has moderate software participation, needs MCU or DSP with better performance, and high-precision ADC, and obviously increases hardware cost; 2. The digital processing method based on Hilbert (Hilbert) transformation has the advantages of higher software participation, high hardware cost, complex algorithm realization, extremely high requirement on digital signal processing capability of developers and extremely high development cost, and needs a high-performance DSP or a high-end MCU with FPU, and a high-speed and high-precision ADC. 3. The combined controller and the dynamic compensation method based on the DSP and the FPGA have the highest software participation, the DSP and the FPGA are high-value chips, peripheral circuits are complex, hardware cost is highest, a team with FPGA logic design and DSP algorithm development capability is needed, the system architecture is complex, the development period is long, and the development cost is highest. Disclosure of Invention Aiming at the technical problems, the invention aims to provide a phase closed-loop regulating circuit of a piezoelectric ultrasonic transducer, which can directly detect by using an alternating-current voltage signal without converting the alternating-current voltage signal into a direct-current voltag