Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2000-02-14
2001-06-12
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
C310S316010
Reexamination Certificate
active
06246153
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a positive feedback amplifier circuit that preferably includes a resonating piezoelectric transformer device. The preferred combined circuit can be used to power an auxiliary high voltage electronic device very efficiently using a low voltage power source, and as a device that emits audible or ultrasonic signals or that acts as a transducer.
BACKGROUND OF THE INVENTION
Resonant transducers or transformers capable of stepping up an input voltage are well known in the art. It is similarly well known that such devices will operate most efficiently, i.e. produce the most or optimum gain, at their resonant frequency. Such resonant transducers are useful in situations where it is necessary or desirable to drive an electronic device with a relatively high voltage, while the only available power supply may be of relatively low voltage. For example, it may be desirable to use a 6 or 9 volt battery, for reasons of compactness or remoteness, to power a device requiring a 120-150 volt input. U.S. patent application Ser. No. 08/864,029 filed May 27, 1997, now U.S. Pat. No. 5,834,882 describes a multilayered, laminated, piezoelectric transformer. U.S. Provisional Application No. 60/165,864 filed Nov. 16, 1999 describes a thickness mode piezoelectric transformer with end-masses. Each of these transformers demonstrates the ability to convert a primary or input voltage V
1
to a higher secondary or output voltage V
2
through the application of V
1
to a first polarized piezoelectric ceramic layer(s) to generate an extensional stress which is then mechanically transmitted to a second tightly adhered polarized piezoelectric ceramic layer(s) which undergoes a similar and proportional extensional stress producing V
2
. The ratio of the first voltage V
1
to the second voltage V
2
is a function of the piezoelectric properties of the two layers, the size and geometry of the two disk or plate shaped layers and the size and elasticity of the ceramic layers and other adhesive and pre-stress layers as well as the electrode configuration and polarizing characteristics of the ceramic layers utilized in the devices described in the above-referenced applications. Similarly, the resonant frequency of a particular design of such a device will be determined by the same parameters.
SUMMARY OF THE INVENTION
According to the present invention, there is provided a circuit which preferably incorporates the previously referenced piezoelectric transformers in combination with a positive feedback amplifier circuit to yield a device capable of serving: 1) as an energy source capable of driving an auxiliary high voltage device with an initial low voltage input; or 2) to produce either an audible or ultrasonic signal which may mechanically drive another device.
The resonating (i.e. oscillating) transducer piezoelectrically generates an output (“secondary”) voltage of alternatingly positive and negative polarity. In one embodiment, this voltage is stepped up and temporarily stored by a rectifier-capacitor array and subsequently supplemented with voltage from a relatively low voltage make-up battery. A supplemented, stepped up voltage of reversed polarity is then fed back into the “primary” side of the transducer during each half cycle of operation. Sequencing and application of the reverse polarity voltage to the primary side of the transducer is accomplished by an operational amplifier which alternatingly drives a pair of power transistors whose output is communicated to the primary side of the transducer. The described process is repeated, and voltage output from the secondary side of the transducer continues to increase, until the circuit reaches steady state, typically after several cycles of transient operation. As the capacitors or the rectifier-capacitor array become charged, the electrical impedance of the array (and therefore the impedance seen at the secondary side of the transducer) decreases. As the impedance decreases, the voltage gain of the disclosed transducer inherently decreases. The ultimate voltage gain of the circuit can therefore be determined by matching the impedance of the rectifier-capacitor array and the transducer at the desired voltage output/gain.
Alternatively, the oscillating piezoelectric transformer/ transducer may operate in a pulsed mode regenerative resonant circuit. In this mode, a voltage pulse is applied to the transformer. This voltage is stepped up and rectified and supplemented with voltage from a relatively low voltage make-up battery and temporarily stored in a capacitor. A trigger circuit senses the voltage at the capacitor and when the voltage reaches a certain level, generates a trigger signal. The trigger signal opens the gate of an SCR, which allows the capacitor to discharge sending another voltage pulse to the “primary” input side of the transformer. The described process is repeated, and voltage output from the secondary side of the transducer continues to increase, until the circuit reaches steady state, typically after several cycles of transient operation.
Accordingly, it is an object of the present invention to provide a positive feedback resonant transducer circuit for generating a relatively high alternating voltage from one or more relatively low direct voltage sources.
It is another object of the present invention to provide a circuit of the character described in which the voltage is stepped up by a piezoelectric transformer.
It is another object of the present invention to provide a circuit of the character described in which the stepped up voltage is fed back into the primary side of the piezoelectric transformer to produce a supplemented stepped up voltage at the secondary side of the transformer.
It is another object of the present invention to provide a circuit of the character described in which the piezoelectric transformer comprises a pair of piezoceramic layers intimately bonded together.
It is another object of the present invention to provide a circuit of the character described in which the piezoelectric transformer comprises a plurality of piezoceramic layers intimately bonded together and vibrating in a thickness mode.
It is another object to provide a modification of the present invention in which the piezoelectric transformer produces an acoustic or ultrasonic signal.
It is another object to provide a modification of the present invention in which the stepped up voltage is used to drive an auxiliary high voltage device.
It is another object to provide a modification of the present invention in which the vibration of the transducer / transformer is used to mechanically vibrate an auxiliary device.
Further objects and advantages of my invention will become apparent from a consideration of the drawings and ensuing description thereof.
REFERENCES:
patent: 5654605 (1997-08-01), Kawashima
patent: 5705877 (1998-01-01), Shimada
patent: 5969954 (1999-10-01), Zaitsu
patent: 6054796 (2000-04-01), Bishop
patent: 6114797 (2000-09-01), Bishop et al.
Bishop Richard Patten
Boyd Clark Davis
Bolduc David J.
Clark Stephen E.
Dougherty Thomas M.
Face International Corp.
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