Analyze the principle of application of ultrasonic cleaner equipment power supply

Ultrasonic cleaning machine equipment is ultrasonically applied to the cleaning of the workpiece, so that attached to the workpiece on the particles, oil, etc. with the mechanical vibration of the ultrasound off or dissolved or emulsified, to achieve the purpose of cleaning the workpiece. In principle, the core part of ultrasonic cleaning equipment should be the role of ultrasound.

Ultrasonic cleaning machine equipment in the ultrasonic part is divided into two parts; one is an ultrasonic transducer {or ultrasonic vibration head; the other is an ultrasonic generator, ultrasonic transducer is to convert the electrical signal provided by the ultrasonic generator to Mechanical vibration. This article only discusses ultrasonic generators and does not discuss ultrasonic transducers.

Ultrasonic generator (hereinafter referred to as the generator) is essentially a power signal generator, which generates a sinusoidal (or quasi-sinusoidal) signal at a certain frequency. The development of ultrasonic generators is closely related to the development of power electronic devices and can generally be divided into electronic tubes and analogs. Transistors. Switching transistors in these several stages, respectively, described below.

The principle of ultrasonic cleaning equipment

First, the signal generator generates a specific frequency signal. This signal can be either a sine signal or a pulse signal. The specific frequency is the frequency of the transducer. The ultrasonic frequency used in ultrasonic equipment is 25 KHz and 28 KHz. , 35KHz, 40KHz; 1OOKHz or above is not yet widely used, but with the continuous development of precision cleaning. I believe that the use of face will gradually expand.

The power amplifier can have many forms, such as a tube type A amplifier, A type B amplifier, a transistor type A or B type amplifier (all analog type), a transistor switching type amplifier, etc. The power generally varies from 50W to 5000W, and is generated by the signal After the frequency signal generated by the device passes through the power amplifier, impedance matching is required so that the output impedance matches the transducer and the transducer is driven to convert the electrical signal into mechanical vibration.

The more perfect ultrasonic generator should also have feedback links, mainly provide two feedback signals: The first is to provide the output power signal, we know that when the generator's power supply (voltage) changes when the generator's output power It will also change, this time reflected in the transducer is the mechanical vibration suddenly large or small, resulting in unstable cleaning effect. Therefore, the need to stabilize the output power, the power amplifier through the power feedback signal corresponding adjustment, making the power amplifier stable.

The second is to provide frequency tracking signals. When the transducer is operating at the resonant frequency, its efficiency is the highest and the operation is the most stable, and the resonant frequency of the transducer will change due to assembly reasons and the aging of the work, of course, this change. The frequency is only drifting, the change is not very big, the frequency tracking signal can control the signal generator, make the frequency of the signal generator track the resonant frequency point of the transducer in a certain range. Let the generator work in the best condition. Of course, with the development of modern electronic technologies, especially microprocessors (uP) and signal processors (DSPs), the functions of generators have become more and more powerful, but no matter how they change, their core functions should be as described above. It's just that the technology is different when each part is implemented.

Ultrasonic generator (hereinafter referred to as the generator) is essentially a power signal generator, which generates a sinusoidal (or quasi-sinusoidal) signal at a certain frequency. The development of ultrasonic generators is closely related to the development of power electronic devices and can generally be divided into electronic tubes and analogs. Transistors. Switching transistors in these several stages, respectively, described below.

The principle of ultrasonic cleaning equipment

First, the signal generator generates a specific frequency signal. This signal can be either a sine signal or a pulse signal. The specific frequency is the frequency of the transducer. The ultrasonic frequency used in ultrasonic equipment is 25 KHz and 28 KHz. , 35KHz, 40KHz; 1OOKHz or above is not yet widely used, but with the continuous development of precision cleaning. I believe that the use of face will gradually expand.

The power amplifier can have many forms, such as a tube type A amplifier, A type B amplifier, a transistor type A or B type amplifier (all analog type), a transistor switching type amplifier, etc. The power generally varies from 50W to 5000W, and is generated by the signal After the frequency signal generated by the device passes through the power amplifier, impedance matching is required so that the output impedance matches the transducer and the transducer is driven to convert the electrical signal into mechanical vibration.

The more perfect ultrasonic generator should also have feedback links, mainly provide two feedback signals: The first is to provide the output power signal, we know that when the generator's power supply (voltage) changes when the generator's output power It will also change, this time reflected in the transducer is the mechanical vibration suddenly large or small, resulting in unstable cleaning effect. Therefore, the need to stabilize the output power, the power amplifier through the power feedback signal corresponding adjustment, making the power amplifier stable.

Several stages of generator development

The generator development can be divided into three major stages; the first stage is to use a tube amplifier; the second stage is to use a transistor analog amplifier; and the third stage is to use a transistor digital (switch) amplifier.

3.1 Tube Amplifier

In the early 1980s, the power amplification of the signal also used the tube. The only advantage of using the tube is its wide dynamic range. This benefit is important for the audio amplifier, but it is of no use for the ultrasonic generator, so once the power After the transistor appeared, it was eliminated. The electron tube has many disadvantages, for example, high power consumption. Large size, short life, and low efficiency.

3.2 Transistor Analog Amplifier

From the 1980s to the mid-1990s, the development of power transistors has been very mature. Various OCL and OTL circuits are suitable for generators. Its schematic diagram is shown in Figure 2.

The signal generator generates a sine wave of a specific frequency, amplifies the signal through a preamplifier, and drives the power amplifier to perform power amplification. After impedance transformation, it is provided to the transducer, in which VCC, VEE is a DC power source after transformation, rectification and filtering.

However, analog power amplifiers have several disadvantages:

(1) Large power consumption. Because OCL, OCL circuit theory efficiency is only about 78%, the actual efficiency is lower, the power consumption is large, causes the power tube to generate heat seriously, needs the bigger heat dissipation power. The heat of the power tube causes the work not to be stable.

(2) Large volume, heavy weight, due to the power of the power tube output

The limitation is that more power tubes are needed to output more power, and the DC power required by the generator is stepped down by the transformer. Rectification. The high-power transformer obtained after filtering is heavy and relatively inefficient.

(3) It is not easy to use modern microprocessors for processing. Because this circuit presents a typical analog line characteristic, it is more complex to use digital processing, involving A/D (analog to digital) and D/A (digital to analog) , The cost is high and the reliability is low

Application of Ultrasound in Extraction Currently, the application of ultrasound in extraction has become increasingly widespread, and it has been industrialized in the extraction of traditional Chinese medicine. The extraction of traditional Chinese medicine in our country has the disadvantages of large solvent consumption, long extraction time, high extraction temperature, long process route, and low extraction efficiency, which results in high residual solvent content, low active ingredient content, difficult to control quality, and lack of efficacy. Obvious and other major problems, low product prices, and weak competitiveness in the international market have greatly constrained the process of modernization of Chinese medicine. Ultrasound for the extraction of traditional Chinese medicine can significantly reduce the solvent consumption and shorten the extraction time. At a lower temperature, it can achieve a high extraction rate without damaging the active ingredients in traditional Chinese medicine. It can be widely used in traditional Chinese medicine. Extraction of saponins, alkaloids, flavonoids, terpenoids, organic acids and polysaccharides. Ultrasonic waves are caused by ultrasonic cavitation. The strong ultrasonic waves emitted from the ends of the horns activate the cavitation bubbles in the liquid in the reaction vessel. When the ultrasonic waves collapse, the shock waves or jets act on the cell walls and cause them to break. Currently, supercritical CO2 extraction has become a research hotspot in recent years due to its advantages of being green without pollution, having little or no residual solvent, ineffective deactivation of product active ingredients, and high product quality. At the same time, the technology has the disadvantages of high extraction pressure, long time, low extraction rate, large amount of entrainer and high energy consumption, which greatly limits its industrial application. Ultrasonic application of supercritical fluid extraction can significantly reduce the extraction system pressure and temperature, reduce the amount of entrainer and shorten the extraction time, and the extraction rate is also significantly improved. Riera E studied the extraction of oils and fats from almond kernels using ultrasound-enhanced supercritical CO2 fluids. The experiment used 20 kHz, 50 W ultrasound. The results showed that the extraction time of almond oil was shortened by 30 at the same extraction rate compared to ultrasound without ultrasound in supercritical CO2, while the extraction rate was increased by 20 at the same extraction time. In addition, at lower power conditions, the ultrasonic transducer can be used as a high-sensitivity probe to show the phase behavior of the supercritical fluid. At present, the research of ultrasonic extraction is mainly limited to single-frequency ultrasound, but there are few studies on the simultaneous radiation enhanced extraction of two or more multi-frequency ultrasound. Research in this area is a new topic that has only been invested in research in recent years. Experiments have shown that the dual-frequency and tri-frequency ultrasound orthogonal irradiation can significantly increase the yield of sonochemical products. The domestic investment in this research is in its infancy, and many aspects of research, such as frequency selection, layout of ultrasonic emission positions, and power Collocation and other aspects need to be further deepened. The author's laboratory is currently undergoing multi-frequency ultrasound to extract alkaloids from bitter wood and has achieved encouraging phase results.