Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
1999-04-28
2001-02-13
Budd, Mark O. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S359000, C310S316020
Reexamination Certificate
active
06188163
ABSTRACT:
TECHNICAL FILED
This invention relates to a converter with piezoceramic transformer.
BACKGROUND ART
Solid state piezoceramic converter with a small output power around 3 watts has been developed and applied as a power source for LCD backlight in notebook computer.
Following references may be referred to understand prior art in this field.
1. C. A. Rosen, “Ceramic transformers and filters”, Proc. Electronic Comp. Symp., 1956.
2. H. W. Katz, “Solid state magnetic and dielectric devices”, New York: John Wiley and Sons. 1959.
3. W. P. Mason, “Physical acoustics”, Vol.1 Part A.1964.
4. R. Holland, “Contour extensional resonant properties of rectangular piezoelectric plates”, IEEE Trans., Sonics and Ultrasonics, SU-15. pp. 97-105, April, 1968.
5. A. A. Yerofeev, A. I. Proklin, V. I. Orekhov, et al. “Piezoelectric current transformer”, USSR Inventor Certificate No. 1254967, published 1986, Bull. No.32 (in Russian).
However, piezoceramic transformer(PCT) for a large power application was not very successful due to a lack of adequate design of piezoceramic element which can deliver a large output current.
This invention is to design converters using PCT which can directly input household electricity, 220 V (110 V) 50 Hz or 60 Hz at an output power up to several dozens watts for applications such as electric illumination appliances, medical appliances, etc.
Piezoelectric transformer as an electromechanical electric energy transformer has monolithic solid state constructions made of piezoceramic in a form of bar, plate, disk, or cylinder. The unique feature of PCT is the resonance nature of electric energy transfer within a relatively narrow frequency band near the mechanical resonance, where the amplitude of mechanical internal stress achieves the maximum value (1, 2, 3).
While electric energy transfer in traditional electromagnetic (coiled) transformers is realized through electro-magnetic-coupling from the input to the output, energy transfer in a PCT is achieved through electro-mechanical coupling. Unlike a low-impedance electromagnetic transformer, PCT is rather a power source due to a relatively high output impedance.
Piezoceramic transformers have the following major advantages:
enhanced efficiency and a low level of electromagnetic interference
planar construction and highly selective frequency characteristics
simple monolitic construction for ease of mass production
high operating frequency of electric energy transformation
no fire hazard and enhanced safety to shorting
According to the type of deformation wave excited in the bulk of dielectric (piezoelectric) element, PCTs are classified into longitudinally-transverse and bending. The most common PCT are of plate and bar type with excitation of longitudinal oscillations oriented along width, length, or circumference. (4, 5).
Selection of PCT construction and thus its working frequency is determined primarily by the technical requirements to the input and output parameters such as input/output voltage, load resistance, load current, the stability of the output voltage and the admissible driving frequency.
DISCLOSURE OF INVENTION
The object of this invention is to design a compact, reliable and economic converter using a piezoceramic transformer which can handle household electricity, 110/220V AC with 50/60 Hz directly and a large power up to 40 W.
In order to achieve the aforementioned object, this invention provides a piezoceramic converter for high power applications which is constructed with a piezoceramic transformer being designed in the form of a square or circular piezoplate polarized in thickness direction and excited in contour extensional mode mode. The size of the piezoceramic transformer is 10-50 mm in side of square plate or in diameter of circular plate and 1-6 mm in thickness. A pulse-synchronized electronic feedback circuit is incorporated to stabilize output voltage and current under varying load conditions. Feedback circuit consists of two diodes and a capacitor connected in parallel and a resistor connected in series to it. Frequency programming elements, a resistor and a capacitor are built into the control circuit to set an operating frequency of the piezoceramic transformer.
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Budd Mark O.
Dong Il Technology Ltd.
Jacobson Price Holman & Stern PLLC
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