Application of piezoelectric ceramics in the new fields(2)

Piezoelectric transformer

Piezoelectric transformers have been developed since the 1950s, but they were not commercialized until the 1990s. The successful application of piezoelectric transformers, on the one hand, the advancement of materials is the use of sub-micron fine PZT piezo ceramic materials, the mechanical strength is very good, high-power ultrasonic signal transmission equipment is the use of this material; It is in the control circuit. transformation method is adopted, which maintains the output current under the stable conditions to effectively control the driving frequency of the piezo transducer piezoelectric plates. In addition, the main weakness of the piezoelectric ceramic transformer (high output impedance) , the output current is small and the output voltage load changes greatly, etc.), find the applicable occasion, such as used in the cold cathode tube for LCD backlighting.

Piezoelectric ceramics are our common "free energy" such as "lighter on your body. Firearms in your gas stove. There are piezoelectric ceramic speakers. The people of essence think of this. And builting the piezoelectric ceramic road that is driven by the car. The roadbed is under pressure. This pressure is a free energy that does not have to be paid. As long as the initial investment. Will not be necessary in the future." Re-investment of energy. The highway overpass with piezoelectric ceramics buried under the road is a very good power plant.

Piezoelectric device for active vibration reduction and noise reduction

The piezoelectric material itself has a positive and negative piezoelectric effect,which is making it an ideal material for detectors and actuators in the active distribution control of flexible structures. The most important piezo ceramic crystal quartz used in this respect are PZT and PVDF. Compared with the former, PVDF has the advantages of wide frequency response, easy matching with acoustic impedance, high mechanical strength, good flexibility, light weight and impact resistance, easy to make large-area film, and low price. Schematic diagram of piezoelectric ceramics to control noise reduction and vibration reduction. A crucible with a piezoelectric detector and actuator. The piezoelectric layer at the bottom (for detection) senses the displacement of the crucible,which generates a corresponding voltage, multiplies this voltage by a certain control law and feeds it back to the upper piezoelectric actuator, which is subjected to voltage. Act to produce mechanical vibration. If the feedback voltage is converted to a phase of 180°C, this vibration will cancel the vibration of the helium, thus achieving the purpose of vibration and noise reduction. Such distributed detectors and actuator devices are referred to as smart structures due to their self-monitoring and self-regulating capabilities. It has been applied to the vibration and noise reduction of submarine shells, aircraft cabins and launch spacecraft cabins.

A typical example is a space truss structure proposed by the American Jet Engine Laboratory. It installs a stacked PMN actuator at each truss node and acts as an active force. This immediately suppresses unwanted vibrations. Another application is to use a multi-layer PMN electrostrictive actuator to control the phase of incident light waves within the optical information processing range . The PMN electrostrictive actuator optimizes the telescope image.

Medical miniature piezoelectric ceramic sensor