Electrical generator or motor structure – Non-dynamoelectric – Piezoelectric elements and devices
Reexamination Certificate
2000-02-01
2001-02-27
Dougherty, Thomas M. (Department: 2834)
Electrical generator or motor structure
Non-dynamoelectric
Piezoelectric elements and devices
Reexamination Certificate
active
06194810
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a piezoelectric or similar transducer device with an oscillating circuit excitable by a control circuit, the said control circuit having an alternating voltage generator that outputs an alternating excitation voltage to the oscillating circuit terminals with a frequency determined such that an alternating sinusoidal operating current with the same frequency passes through the oscillating circuit.
2. Discussion of the Background
In known piezoelectric transducer devices of this type, the excitation frequency is different from the resonant voltage in the oscillating circuit; the result is that the current passing through the oscillating circuit is not in phase with the excitation voltage, such that the transducer is not used under its maximum efficiency conditions. Since the resonant frequency of a piezoelectric transducer can vary fairly significantly, for example by plus or minus 15%, it would be impossible to consider exciting it using an oscillator with a fixed frequency.
Furthermore, in known transducer devices, the transducer device itself is connected to the control circuit through two wires when a return signal is not required. It is connected to it through three wires when a return signal is required.
SUMMARY OF THE INVENTION
The purpose of the invention is to simply optimize the energy efficiency of a piezoelectric or similar transducer device of the type described above. It is also designed to enable this type of optimization using two connecting wires only between the transducer device and its control circuit.
According to the invention, the alternating voltage generator is a flip-flop to which control means are coupled such that the flip-flop changes state when the operating current changes sign.
The control means preferably comprise a device for putting the alternating excitation in phase with the operating current, this device being connected to the oscillation circuit and to an input of the flip-flop to output a control signal to the flip-flop that switches when the operating current changes sign in order to adjust the excitation frequency to the resonant frequency of the oscillating circuit. The link between the oscillating circuit and the control circuit is advantageously made using two wires only and a resistor to adjust the transducer emission level may be located on one of these wires.
In one very simple embodiment, the control means comprise at least one pair of power transistors inserted between the flip-flop and the oscillating circuit as follows: their base-emitter paths are capable of connecting one output from the flip-flop to a terminal of the oscillating circuit and their collectors are connected to one input of the flip-flop through diodes with inverse polarities; in this way, the transistor base current is approximately equal to the operating current and the collector current generates periodic pulses forming the flip-flop control signal.
The flip-flop preferably comprises inverter switches mounted according to an H type structure top-to-bottom with respect to the oscillating circuit and it may be laid out to form a starter oscillator.
A non-limitative embodiment will now be described with reference to the attached drawings.
REFERENCES:
patent: 4914336 (1990-04-01), Yamasaki
patent: 5010222 (1991-04-01), Suganuma
patent: 5355047 (1994-10-01), Okada
patent: 0 012 653 (1980-06-01), None
patent: 0 283 254 (1988-09-01), None
patent: 2 559 331 (1985-08-01), None
Patent Abstracts of Japan, JP 7-093668, Apr. 7, 1995.
Patent Abstracts of Japan, JP 10-284941, Oct. 23, 1998.
Patent Abstracts of Japan, JP 4-277809, Oct. 2, 1992.
Dougherty Thomas M.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Schneider Electric Industries SA
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