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Basic working principle and characteristics of multilayer piezoelectric ceramic transformer

Views:5     Author:Site Editor     Publish Time: 2019-10-11      Origin:Site

The application of the positive piezoelectric effect is mainly used for gas igniters, such as gas stoves. Ignition system for gas lighters, etc. The basic working principle is: compressing a spring by an external force, releasing it after pressing to the apex, and the spring force pushes a heavy hammer to strike the piezoelectric ceramic column to generate a high-voltage spark of several thousand volts to ignite the combustible gas.

The application of the inverse piezoelectric effect is mainly used for piezoelectric buzzers, such as music cards, doorbells, pager. The basic working principle is that when an alternating electric field is applied on the piezoelectric ceramic sheet, the piezoelectric ceramic sheet generates a corresponding deformation or vibration, and when the vibration frequency is in the audio band, a corresponding sound is emitted.

The application of this feature in conjunction with the mechanical resonance principle is also widely used to manufacture electronic components such as resonators, frequency selectors, delay lines, and filters.

The basic structure of a piezoelectric ceramic transformer is to combine the application of a piezoelectric buzzer with the application of a piezoelectric igniter to form a piezoelectric resonator. At one end of the buzzer (called the drive end), a sinusoidal alternating voltage is generated which is consistent with the resonant frequency of the piezoelectric transformer. The piezoelectric resonator generates vibration and is transmitted to one end of the igniter (called the power generating end), resulting in continuous sinusoidal voltage depends on the structural characteristics of the piezoelectric transformer, and can be input low voltage, output high voltage (boost type), or input high voltage, output low voltage (buck type). Signal transmission can be achieved by adding low frequency modulation through the modem at the high frequency drive voltage.

Piezoelectric ceramics are brittle materials. In order to ensure the mechanical strength, piezoelectric transformers must have a certain thickness, and the driving voltage of the above transformers is considerably limited. For this reason, a monolithic (multi-layer) piezoelectric ceramic transformer project came into being. The basic structural form of a monolithic (multilayer) piezoelectric ceramic transformer.

After adopting the monolithic (multi-layer) structure, the thickness and the number of layers of single layer custom linear piezo tubes are adjustable, and the driving voltage is no longer limited, so that the piezoelectric transformer can work at an optimum state regardless of the driving voltage.The core technology of this project is submicron low temperature sintered piezoelectric ceramic material, internal electrode co-firing technology, polarization treatment technology and structural design.

Monolithic (multi-layer) piezoelectric ceramic transformer (MPT) is a third-generation electronic transformer with
1. Ultra-thin: the thickness gauge generally does not exceed 4 mm
2. High conversion efficiency: over 97% at full load (resistive load)
3. Self-protection characteristic with automatic short-circuit of load short circuit
4. Resonant transformer: zero voltage, zero current conversion
5. Quasi-constant current output characteristics for low resistance loads
6. No anti-peak voltage, reliable protection power amplifier circuit
7. No electromagnetic interference
8. No coil breakdown, mold break
9. Resistance to salt spray, good weather resistance, especially suitable for maritime climate usage.

Accurate positioning application of piezoelectric ceramic sheets in industrial control process.Following the discovery of the piezoelectric effect, piezoelectric ceramics first served as an electroacoustic or acoustic device , and there are many applications, such as acoustic sensors and shock sensors. They are generally used in the fields of measuring vibration, shaking, and so on.There are no mature applications for accurate position measurement. industrial equipment in motion control towels, for high-precision position control, the best sensor parts are various encoders, which can not only easily achieve accuracy of 0.01 mm or even micron, but also can collect position data in the whole process of motion. However, the fly is that it is expensive. Ordinary optical sensors are generally composed of red LED and phototransistors, each of which uses a slit of a certain width to limit the size of the emitted and received beams. Therefore, the transmission characteristics of the photosensitive tube and the size of the beam directly determine the accuracy of the sensor.

Under the requirement of high precision, the detection result of ordinary piezo ceramic plate transducer is extremely fuzzy. Even after digital shaping, due to the influence of the drift of the working point and the external environment interference, we cannot obtain the stable repeated detection results. Therefore, such optical sensors are generally used for precision requirements of 0.5 mm or less required for general mechanical positioning. In order to adapt to the accuracy of the stepper motor of 0.1 mm or more, it is theoretically required to further reduce the slit width. Actually it is too small slit width. The photosensitive device will not be able to obtain sufficient luminous flux, so that the photosensitive tube cannot be turned on, and thus the movement of the obstruction cannot be detected. Other electromagnetic induction sensors, such as proximity switches and hall sensors, require moving metal or ferromagnetic materials to approach the sensing surface. In the range of a certain distance, the resulting intermediate level is confirmed as the flip state. However, the range of this distance is relatively vague and random, and the reproducibility of the test results will also be affected by factors such as the specific circuit conditions, the surrounding environment, and the response delay, so it cannot be used for the control of high-precision positioning. For these reasons, the near-micron-level precision positioning has so far been almost non-encoders, and devices that can use such precision levels are generally inexpensive, regardless of the cost price factor of the sensor. However, inexpensive stepper motors provide high enough drive accuracy, such as the worst step angle of 1.8 degrees, which can be obtained with a rougher lead screw drive (10mm/360*1.8=) . The control precision of 0.5mm, in the cheap electromechanical system composed of stepping motor, how to realize the position control of the sensor which is cheap and can match the accuracy of the stepping motor. Using the  piezoelectric ceramic piece in the impact the potential allows for an inexpensive and precise position control solution. Below is an application plan. To clarify its feasibility and implementation methods. Assume that the work platform starts from the initial position, moves a specified distance, and then returns to the initial position to complete a work cycle. Here, a stepper motor drive is used, with the correct starting acceleration and brake deceleration to ensure the smallest possible out-of-step, so that any precise positioning of the working platform can be achieved only the open-loop control of the stepper motor. Installing the piezoelectric piece at the starting point position not only provides the initial reference position to the system, but also allows the accumulating loss of the out-of-control, disorder, etc. during the driving process by returning each working cycle of the platform to the reset position. Making each work cycle start at the exact reset position. Although the electrical signal of the reset sensor is generated by a mechanical impact, the impact can be made non-destructive by the following measures: (1) Low-speed impact: When the motion approaches the reset position, the speed is slow down, which is known as the stroke. The acceleration and deceleration motion control can be realized. In the case of unknown travel, you can keep the whole slow motion to approach the reset position; (2) Impact buffer: the impact member is added with rubber or spring to buffer, adjusting the appropriate preload, which can be obtained before the cushioning element is obviously deformed. The electrical signal that strikes the output, the cushioning effect reduces the rigidity of the impact and prolongs the service life of the sensor. When the system is out of control, depending on whether the motor is blocked or not, the following measurement can be taken to avoid the occurrence of runaway. (1) Hard blocking: When the motor drive system is allowed to block, using the rigid mechanical limit to limit the continued movement after impacting the piezoelectric ceramics; (2) Flexible crossing: in the case of not allowing the blocking, use spring/shake A mechanism such as a rod is loaded with a hammer. When it is out of control, the mechanism can move across the sensor, the platform continues to move forward, and an emergency trip switch is added to cut off the corresponding power source, or other measurement to terminate the abnormal operation.

The application of piezoelectric ceramic sheets in the structural health monitoring systems. In recent years, piezoelectric impedance technology has been studied more and more in structural health diagnosis. The structural health diagnosis of piezoelectric impedance technology successfully used to assemble trusses is considered to be the beginning of the application of piezoceramic elements ring impedance technology in the field of structural health diagnosis. Piezoelectric impedance technology has the advantage of being sensitive to small damages in the structure, which is helpful for detecting the initial failure of the structure, and the PZT piezoelectric material (lead zirconate titanate piezoelectric ceramic) commonly used in piezoelectric impedance technology has a small volume and structure. Simple and reliable. In addition, PZT is only sensitive to changes in the local range nearby, which helps to separate the mass loading of the structure, structural stiffness and boundary condition changes and the influence of structural damage near PZT on the measurement results, so this technique is suitable for tracking and monitoring. Weak links are critical to structural integrity or have a significant impact on structural life and are not easily detectable.

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