A high power ultrasonic transducer drive source and method of use thereof

Abstract

This invention discloses a high-power ultrasonic transducer driver and its usage method, belonging to the field of ultrasonic technology. The driver includes a microcontroller control module, a full-bridge power inverter circuit, a phase-locked loop (PLL) frequency tracking module, a power detection and overcurrent protection module, and a human-machine interface module. The microcontroller control module generates an adjustable frequency PWM signal, which the full-bridge power inverter circuit converts into a high-frequency AC signal and outputs to the transducer. The PLL frequency tracking module collects the transducer feedback signal and adjusts the PWM frequency to achieve automatic tracking. The overcurrent protection module detects the drive current and issues a shutdown command when it exceeds a threshold. The human-machine interface module is used for parameter setting and status display. The usage method includes initialization, parameter setting, signal output, frequency tracking, overcurrent protection, and cyclic driving steps. This invention features high frequency tracking accuracy, fast response speed, and stable operation.

Description

Technical Field

[0001] This invention relates to the field of ultrasonic technology, specifically to a high-power ultrasonic transducer drive source and its usage method. Background Technology

[0002] With the widespread application of ultrasonic technology in cleaning, welding, atomization, medical treatment, and industrial processing, the requirements for the performance of ultrasonic transducers and their driving sources are constantly increasing. Especially in high-power ultrasonic transducer systems, the driving source must possess characteristics such as high output power, adjustable frequency, high efficiency, and good stability. In existing technologies, high-power ultrasonic transducers typically rely on a fixed-frequency driving source. However, during actual operation, ultrasonic transducers are affected by factors such as temperature rise, load changes, and material aging, causing their resonant point to drift. If the driving source cannot track and adjust in time, the transducer will deviate from its resonant state, leading to decreased energy transmission efficiency, severe heat generation, and even potential damage to the transducer. This detuning phenomenon is particularly pronounced in high-power continuous operation, becoming a key issue affecting system stability. Furthermore, the driving source needs to operate at high frequencies of tens or even hundreds of kilohertz, placing high demands on the switching speed, driving capability, and electromagnetic interference control of power devices. Traditional circuits often suffer from reduced efficiency, severe device overheating, and circuit instability under high-frequency conditions.

[0003] Therefore, how to achieve automatic tracking of the resonant point of the ultrasonic transducer under high power conditions and ensure stable and efficient operation of the drive circuit at high frequency is a technical problem that urgently needs to be solved. Summary of the Invention

[0004] The purpose of this invention is to provide a sludge drying device, comprising a mains power supply, a rectifier and filter circuit, a DC-DC converter, a DSP processor, a microcontroller control system, a PWM amplifier circuit, a full-bridge inverter circuit, and electrodes. The mains power supply provides power to the sludge drying device. The rectifier and filter circuit converts the mains power into DC power. The DC-DC converter, connected to the rectifier and filter circuit, transforms and stabilizes the voltage. The DSP processor assesses the sludge state based on signals from a humidity sensor and generates pulse signals with corresponding pulse widths according to the sludge state. The microcontroller control system generates control signals. The PWM amplifier circuit amplifies the PWM waveform. The full-bridge inverter circuit, connected to the PWM amplifier circuit, converts the DC voltage into a bipolar pulse voltage to prevent electrode electrolytic corrosion. The electrodes, connected to the full-bridge inverter circuit, apply an alternating electric field to the sludge to accelerate moisture polarization migration.

[0005] Furthermore, the DC-DC converter employs a full-bridge LLC resonant converter to achieve wide voltage range regulation; the DSP processor dynamically tracks the optimal dry point through resistivity-frequency closed-loop optimization; the full-bridge inverter circuit consists of four sets of power switching transistors, which achieve DC-to-AC voltage conversion through alternating switching.

[0006] Furthermore, the frequency range of the bipolar pulse is 1kHz to 50kHz, and the amplitude range is 12V to 60V; the target resistivity of the drying device is greater than 200Ω·m, corresponding to a target humidity of 40%.

[0007] Furthermore, the method of using the sludge drying device is characterized by comprising the following steps:

[0008] Step S100: Place the sludge to be treated between the electrodes, ensuring good contact between the electrodes and the sludge;

[0009] Step S200: Start the device. The grid power is converted into DC power by the rectifier and filter circuit. The DC-DC converter transforms and regulates the voltage.

[0010] Step S300: The humidity sensor detects the humidity parameters of the sludge in real time and transmits the detection signal to the DSP processor;

[0011] Step S400: The DSP processor evaluates the sludge state based on the signal from the humidity sensor, dynamically tracks the optimal drying point through resistivity-frequency closed-loop optimization, and generates a pulse signal with a corresponding pulse width based on the evaluation results.

[0012] Step S500: The microcontroller control system receives instructions from the DSP processor and generates a PWM control signal;

[0013] Step S600: The PWM amplifier circuit amplifies the PWM signal to the required drive level;

[0014] Step S700: The full-bridge inverter circuit converts the DC voltage into a bipolar pulse voltage and outputs it to the electrodes;

[0015] Step S800: The electrodes generate an alternating electric field that acts on the sludge, accelerating the polarization and migration of water, thereby achieving sludge drying;

[0016] Step S900: Repeat steps S300 to S800 until the resistivity of the sludge is greater than 200 Ω·m and the corresponding moisture content reaches 40%, thus completing the drying process.

[0017] Furthermore, the resistivity-frequency closed-loop optimization in step S400 specifically includes: setting an initial frequency of 1kHz, continuously monitoring the resistivity and water content of the sludge, and when the resistivity is ≤200Ω·m or the water content is >40%, increasing the frequency in steps of 500Hz, waiting for 30 minutes after each increase, until the resistivity is >200Ω·m and the water content reaches 40%, and outputting the current frequency as the optimal drying frequency.

[0018] Furthermore, the frequency range of the bipolar pulse in step S700 is 1kHz to 50kHz, and the amplitude range is 12V to 60V.

[0019] Furthermore, when the resistivity of the sludge in step S900 is greater than 200 Ω·m and the corresponding humidity reaches 40%, the system automatically stops drying or maintains a heat preservation state.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) This invention uses a single-chip microcomputer combined with a full-bridge inverter circuit and a phase-locked loop frequency tracking module to automatically track the resonant point of an ultrasonic transducer in real time. When the load or temperature changes cause the resonant point to drift, the system can adjust the output frequency in time to avoid deviating from the optimal working state, thereby improving the energy transmission efficiency.

[0022] (2) This invention achieves continuous controllability of output power through PWM duty cycle adjustment, meeting the needs of various applications such as ultrasonic cleaning, welding, crushing and medical treatment. In terms of hardware design, a scheme combining a microcontroller and power electronic circuits is adopted. A series resonant network is formed by a full-bridge inverter combined with a matching inductor and a transducer, so that the output waveform is close to a sine wave, reducing harmonic content and reducing device heat generation.

[0023] (3) This invention uses a power detection and overcurrent protection module to detect the current in real time, and combines it with a microcontroller to implement overcurrent shutdown protection, ensuring long-term stable operation of the system and transducer. In addition, this invention also has human-computer interaction and parameter saving functions, which facilitates user operation and parameter setting.

[0024] The present invention will now be further described with reference to the accompanying drawings. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the system structure of a high-power ultrasonic transducer drive source according to an embodiment of the present invention.

[0026] Figure 2 This is a schematic diagram of the high-power ultrasonic transducer drive source according to an embodiment of the present invention.

[0027] Figure 3This is a full-bridge inverter circuit diagram of a high-power ultrasonic transducer drive source according to an embodiment of the present invention.

[0028] Figure 4 This is a schematic diagram of the phase-locked loop frequency tracking module of the high-power ultrasonic transducer drive source according to an embodiment of the present invention.

[0029] Figure 5 This is a schematic diagram of the current protection principle of the high-power ultrasonic transducer drive source according to an embodiment of the present invention.

[0030] Figure 6 This is a square wave diagram of the high-power ultrasonic transducer drive source according to an embodiment of the present invention.

[0031] Figure 7 This is the minimum system circuit of an STM32 microcontroller for a high-power ultrasonic transducer driver source according to an embodiment of the present invention. Detailed Implementation

[0032] like Figure 1 As shown, the high-power ultrasonic transducer driver in this embodiment mainly includes a microcontroller control module, a full-bridge power inverter circuit, a phase-locked loop frequency tracking module, a power supply detection and overcurrent protection module, and a human-machine interface module. These modules work together organically through signal flow and control paths to achieve all the functions of driving the transducer.

[0033] The microcontroller control module generates an adjustable frequency PWM control signal. The full-bridge power inverter circuit receives this signal and converts it into a high-frequency AC signal, which is then output to the ultrasonic transducer load. The phase-locked loop (PLL) frequency tracking module is connected to the transducer feedback terminal, acquiring the transducer's voltage or current feedback signal and adjusting the PWM frequency output by the microcontroller control module to automatically track the transducer's resonant frequency. The power detection and overcurrent protection module is located in the current path between the full-bridge power inverter circuit and the transducer. It detects the drive current and sends a shutdown command to the microcontroller control module when the current exceeds a set threshold. The human-machine interface module includes setting buttons and a display screen for setting the operating frequency, current threshold, and displaying the operating status.

[0034] like Figure 3 As shown, the full-bridge power inverter circuit consists of an H-bridge structure composed of four MOSFETs. The microcontroller control module outputs two complementary PWM signals, which are amplified and converted into gate drive signals suitable for the MOSFETs by an IR2110 driver chip. The two main output ports HO and LO of the IR2110 are connected to the upper and lower MOSFETs of the full-bridge inverter, respectively. When the upper and lower bridge arms are alternately turned on, the transducers receive an AC square wave voltage with adjustable frequency and constant duty cycle. The drive waveform is a symmetrical PWM signal with a 50% duty cycle, resulting in an undistorted AC output waveform, high efficiency, and suitability for driving capacitive transducer loads.

[0035] like Figure 4 As shown, the phase-locked loop (PLL) frequency tracking module includes an input sampling circuit, a phase detector, a low-pass filter, and a voltage-controlled oscillator (VCO). Its operation is as follows: The voltage feedback signal is taken from both ends of the transducer, limited and amplified, and then input to the phase detector for phase comparison with the microcontroller's PWM clock signal. If the output waveform lags behind, it indicates that the driving frequency is lower than the resonant frequency, so the microcontroller is controlled to increase the PWM frequency; if the phase leads, it indicates that the frequency is too high, so the PWM frequency is decreased. After stabilizing the control voltage through the low-pass filter, it is input to the VCO to achieve dynamic frequency adjustment. In the STM32 microcontroller, the feedback signal period can be directly detected using the timer input capture function, the feedback frequency can be calculated, and then compared with the set value to achieve software phase-locked loop functionality.

[0036] like Figure 5 As shown, the power detection and overcurrent protection module includes a current sensing resistor, an operational amplifier circuit, a voltage comparator, and an alarm output port. The current sensing resistor is a high-power, low-resistance non-inductive sampling resistor, connected in series at the output of the full-bridge power inverter circuit. The operational amplifier circuit amplifies the small voltage signal across the sensing resistor to a range suitable for ADC sampling. The voltage comparator compares the amplified detection signal with a reference voltage; when the detected current exceeds a set threshold, it outputs a low-level signal to trigger a microcontroller interrupt. Upon responding to the interrupt, the microcontroller immediately shuts down the PWM output, simultaneously controls the buzzer to emit an alarm signal, and displays the overcurrent protection status on the screen.

[0037] like Figure 7 As shown, the microcontroller control module uses an STM32F103C8T6 microcontroller. Its minimum system circuit includes a crystal oscillator circuit, a reset circuit, and a power supply circuit. This microcontroller is configured with at least two PWM output channels, one ADC sampling channel, and one external interrupt input port to implement PWM signal output, current sampling, and overcurrent protection interrupt response.

[0038] A matching inductor is connected in series before the transducer load to form a series resonant circuit with the transducer, achieving impedance matching of the drive signal. The matching inductor is a ferrite core inductor, and its value is calculated based on the transducer capacitance parameters and operating frequency to ensure that the entire circuit reaches a series resonant state at the target frequency, minimizing impedance and maximizing current.

[0039] The human-machine interface module includes an OLED display and at least three function buttons for adjusting the PWM frequency, setting the protection current threshold, and controlling start / stop, respectively. The system also includes an EEPROM parameter storage module to save user-defined operating frequency and current protection threshold data, enabling power-off memory functionality.

[0040] This invention also proposes a method for using a high-power ultrasonic transducer drive source, comprising the following steps:

[0041] Step S100: The system is powered on and initialized. The microcontroller control module reads the parameters stored in the EEPROM and sets the default operating frequency and current protection threshold.

[0042] Step S200: The human-machine interaction module receives the frequency adjustment command input by the user, and the microcontroller control module generates a PWM control signal of the corresponding frequency according to the command.

[0043] Step S300: The full-bridge power inverter circuit receives the PWM control signal and converts the DC power supply into a high-frequency AC signal for output to the ultrasonic transducer.

[0044] Step S400: The phase-locked loop frequency tracking module acquires the voltage or current feedback signal of the transducer, compares it with the PWM control signal, and adjusts the PWM frequency output by the microcontroller control module according to the phase difference.

[0045] Step S500: The power supply detection and overcurrent protection module detects the drive current in real time. When the detected current exceeds the set threshold, it sends a shutdown command to the microcontroller control module to stop the PWM output.

[0046] Step S600: Repeat steps S300 to S500 until a stop command is received or a fault signal is detected, thus completing the drive process.

[0047] The prototype system built in the laboratory used the following parameters: input power supply DC 36V 5A, drive frequency 28kHz, maximum output current 3A, transducer model 40kHz industrial ceramic plate, matching inductor 47μH, full-bridge MOSFET IRF540N, driver chip IR2110, microcontroller STM32F103C8T6, current sensing resistor 0.05Ω / 5W, amplifying operational amplifier LM358, comparator LM393, and display module 0.96-inch OLED. During debugging, the PWM signal and voltage waveform across the transducer were observed using an oscilloscope, confirming that the waveform was close to a sine wave under resonant conditions, and the system operated stably. During the transition between no-load and full-load loads, the frequency tracking module could quickly adjust the frequency change, and the current fluctuation was controlled within ±0.2A.

Claims

1. A high-power ultrasonic transducer drive source, characterized in that, Includes the following modules: The microcontroller control module is used to generate adjustable frequency PWM control signals; The full-bridge power inverter circuit receives the PWM signal output by the microcontroller control module at its input terminal and connects to the ultrasonic transducer load at its output terminal to convert the PWM signal into a high-frequency AC signal. A phase-locked loop frequency tracking module is connected to the feedback terminal of the transducer and is used to collect the voltage or current feedback signal of the transducer, adjust the PWM frequency output by the microcontroller control module, and realize automatic tracking of the resonant frequency of the transducer. The power detection and overcurrent protection module is set in the current path between the full-bridge power inverter circuit and the transducer. It is used to detect the magnitude of the drive current and send a shutdown command to the microcontroller control module when the current exceeds a set threshold. The human-computer interaction module includes a setting button and a display screen, which are used to set the operating frequency, current threshold, and display the operating status.

2. The driving source according to claim 1, characterized in that, The microcontroller control module is an STM32 series or 51 series microcontroller, configured with at least two PWM output channels, one ADC sampling channel and one external interrupt input port.

3. The driving source according to claim 1, characterized in that, The full-bridge power inverter circuit consists of an H-bridge structure composed of four MOSFETs. The gate of each MOSFET receives the PWM signal output by the microcontroller control module via an IR2110 driver chip.

4. The driving source according to claim 1, characterized in that, The phase-locked loop frequency tracking module includes an input sampling circuit, a phase detector, a low-pass filter, and a voltage-controlled oscillator, used to compare the phase of the transducer's feedback signal with the PWM signal and adjust the PWM frequency according to the phase difference.

5. The driving source according to claim 1, characterized in that, The power detection and overcurrent protection module includes: A current sensing resistor is connected in series at the output of the full-bridge power inverter circuit. Operational amplifier circuit, used to amplify current detection signal; A voltage comparator is used to compare the detected signal with a reference voltage; The alarm output port is connected to the interrupt pin of the microcontroller control module.

6. The driving source according to claim 1, characterized in that, The human-machine interaction module includes an OLED display and at least three function buttons, which are used to adjust the PWM frequency, set the protection current threshold, and control start and stop, respectively.

7. The driving source according to claim 1, characterized in that, A matching inductor is connected in series with the transducer load to form a series resonant circuit with the transducer, thereby achieving impedance matching of the drive signal.

8. The driving source according to claim 1, characterized in that, The microcontroller control module uses an internal timer and input capture function to periodically measure the transducer feedback signal and dynamically adjusts the output PWM frequency based on a phase adjustment strategy, thereby achieving software phase-locked control.

9. The driving source according to claim 1, characterized in that, The driving source also includes an EEPROM parameter storage module, which is used to store user-set operating frequency and current protection threshold data to realize power-off memory function.

10. A method of using a high-power ultrasonic transducer drive source as described in any one of claims 1 to 9, characterized in that, Includes the following steps: Step S100: The system is powered on and initialized. The microcontroller control module reads the parameters stored in the EEPROM and sets the default operating frequency and current protection threshold. Step S200: The human-machine interaction module receives the frequency adjustment command input by the user, and the microcontroller control module generates a PWM control signal of the corresponding frequency according to the command; Step S300: The full-bridge power inverter circuit receives the PWM control signal and converts the DC power supply into a high-frequency AC signal for output to the ultrasonic transducer; Step S400: The phase-locked loop frequency tracking module acquires the voltage or current feedback signal of the transducer, compares it with the PWM control signal in phase, and adjusts the PWM frequency output by the microcontroller control module according to the phase difference; Step S500: The power supply detection and overcurrent protection module detects the drive current in real time. When the detected current exceeds the set threshold, it sends a shutdown command to the microcontroller control module to stop the PWM output. Step S600: Repeat steps S300 to S500 until a stop command is received or a fault signal is detected, thus completing the drive process.

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