Electricity: electrical systems and devices – Electrostatic capacitors – Variable
Patent
1998-10-09
2000-08-01
Kincaid, Kristine
Electricity: electrical systems and devices
Electrostatic capacitors
Variable
361280, 29 2541, 307110, H01G 700, H03M 180
Patent
active
060975865
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a variable capacitor and to a method of varying the capacitance of a capacitor. The invention further relates to a digital-to-analog, converter and to an electrostatic loudspeaker.
Variable capacitors are widely used in electronics but have restrictions where high voltages or large capacitance ranges are required. Moreover, the value of the capacitor is adjusted mechanically, usually manually or by means of a servo motor. This limits the usefulness of the capacitors where automatic control is required or where very rapid changes in capacitance are necessary, with precision.
It is an object of the present invention to mitigate at least some of the afore-mentioned problems.
SUMMARY OF THE INVENTION
According to the present invention there is provided a variable capacitor including a first electrode, a second electrode separated therefrom and, located between the first and second electrodes, gas discharge means including an ionizable gas and means for producing an electrical discharge in the ionizable gas, thereby affecting the capacitance of the capacitor.
The present invention provides a capacitor whose capacitance may be adjusted electrically, according to analog or digital input signals, without the need for a mechanical interface. This allows the capacitance to be precisely adjusted automatically and with great rapidity. As the capacitor has no moving parts, it is also very reliable and needs minimal maintenance.
The capacitor is also capable of operating at high voltages, can provide a relatively large capacitance and has a large range of variation.
The gas discharge means may include a plurality of gas discharge tubes, said means for producing an electrical discharge in the ionizable gas comprising the electrodes of the gas discharge tubes.
The gas discharge tubes may be connected so as to permit the number of tubes activated to be controlled.
Advantageously, each of said first and second electrodes comprises a plurality of plate elements, the plate elements of the first electrode being interleaved with those of the second electrode.
Gas discharge means may be located between each adjacent pair of interleaved plate elements.
Voltage supply means may be connected to said gas discharge means and arranged to supply a voltage sufficient to activate said gas discharge means. Said voltage supply means may include control means for selectively activating a predetermined number of said gas discharge tubes. Alternatively or in addition, the voltage supply means may include control means for controlling the voltage applied to the gas discharge tubes. Alternatively, the voltage supply means may include means for modulating the voltage applied to the gas discharge tubes.
The present invention further provides a digital-to-analog analog converter including a variable capacitor including a first electrode, a second electrode separated therefrom and, located between the first and second electrodes, a plurality of gas discharge tubes, the gas discharge tubes being connected so as to permit the number of tubes activated to be controlled, and voltage supply means connected to the gas discharge tubes, the voltage supply means including control means for selectively activating a number of the gas discharge tubes in response to a digital input signal received by the control means.
Since the capacitance may be relatively large, analog power may be drawn from the capacitor. It may thus be employed as a digital-to-analog power transducer, without the need for a power amplifier.
According to the present invention there is further provided an electrostatic loudspeaker including a diaphragm, at least one electrostatic drive element. arranged to drive the diaphragm, the electrostatic drive element including a first electrode, a second electrode separated therefrom and, located between the first and second electrodes, a plurality of gas discharge tubes, and voltage supply means connected to the electrostatic drive element, the voltage supply means including control means fo
REFERENCES:
patent: 3665458 (1972-05-01), Mulkey et al.
patent: 4095162 (1978-06-01), Hiddink
patent: 4549312 (1985-10-01), Michaels et al.
patent: 5392358 (1995-02-01), Driver
Patent Abstracts of Japan, vol. 007, No. 258 (E-211) Nov. 17, 1983, JP 58142696 (Matsushita Denki Sangyo KK, Aug. 24, 1983).
Kincaid Kristine
Thomas Eric
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