High Voltage Interface Address Circuit And Method For Gas Discharge Panel

Abstract

There is disclosed an interface circuit for converting low voltage logic signal voltage pulses to high voltage discharge manipulating voltage pulses for a gas discharge display/memory device. The interface circuit is connected such that the output thereof is referenced to the sustaining voltage for the panel. An optical coupled in a multiplex system is used to isolate the low voltage logic source from the high voltage operating circuit and reduce the number isolators for this system.

Parent Case Text

This application is a continuation-in-part of application Ser. No. 851,131 filed July 18, 1969 now U.S. Pat. No. 3,628,088.

Description

BACKGROUND OF THE INVENTION

Gas discharge panels and devices of the pulsing discharge type disclosed in Baker et al. U.S. Pat. No. 3,499,167 (e.g. discharges terminated by stored charges) require relatively high operating voltages, the magnitude of which depends upon, among other things, the discharge gap, gas mixture and pressure, thickness of the dielectric. For example, the gas discharge panel disclosed in the above referenced Nolan application requires sustaining voltages between about 300-400 volts supplied to conductor matrices defining discharge sites. High voltage pulses are added to such sustaining voltages at selected times to manipulate discharges at selected discharge sites. Command or information signals from a computer or other source of information to be displayed and/or stored are normally at a four volt level and such low voltages are of insufficient magnitude to manipulate the discharge condition of selected discharge sites. In the past, low voltage command or address voltages from addressing logic circuits have been translated to voltage level sufficient to manipulate discharges and selected discharge sites by transformers driven by two transistors. Also, high voltage transistor switches actuated by the low voltage command voltages are used to connect a high voltage direct current supply to conductors in the discharge site selection matrix. In such cases, the low voltage circuitry may require additional components to assure isolation of the high voltage supply from the low level logic circuits.

SUMMARY OF THE INVENTION

In accordance with the present invention, isolation of the low level command voltage source is achieved by a use of a multiplex circuit and system. The low voltage system can be earth ground referenced whereas the multiplex circuit system can be referenced to the high level periodic voltage necessary to sustain discharge within the discharge device at a selected site, once initiated.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features, aspects and details of the invention will become more apparent from the following specification when considered with the accompanying drawing illustrating a preferred embodiment of the invention.

DESCRIPTION OF A PREFERRED EMBODIMENT

With reference to the drawing, a gas discharge panel 10 of the type disclosed in Nolan application Ser. No. 764,577 is constituted by a pair of relatively rigid support or plate members 11 and 12, respectively, each of which has on opposing surfaces thereof conductor arrays 13 and 14, respectively, cooperatively defining discharge site locations and a pair of thin dielectric members 15 and 16, respectively, plate member 11 and 12 being joined together and sealed by spacer sealant member 17. The opposing surface of thin dielectric members 15 and 16 constitute at least in part a portion of storage member forming walls of a thin gas chamber under about 10 mils thick, and preferably the gas chamber is about 4 to 6 mils thick. Transversely oriented conductor arrays 13 and 14 are supplied with operating potentials for selectively effecting discharges within the thin gas chamber between selected cross points or matrix points of a pair of the conductors of each array and sustaining and terminating discharges once initiated. The gas is one which is under a relatively high gas pressure so as to localize the discharges within the chamber and to confine charges produced on discharge to within the volume of gas in which they are created. As set forth in the aforementioned Nolan application, the gas in the thin gas chamber has a breakdown voltage verses pressure-time-discharge gap distance which is relatively horizontal or flat over a selected broad range of gas pressure and, preferably is a mixture of neon and argon gases wherein the neon constitutes about 99.9 percent atoms of the gas mixture and the argon constitutes about 0.1 percent atoms of the gas mixture. The gas is under pressure of about 0.2 atmosphere to about 5 atmosphere and preferably from about 0.2 atmosphere to about 1 atmosphere.

As further disclosed in the aforementioned Baker et al. and Nolan applications, charges produced on discharge of the gas are collected upon the discrete surface areas of dielectric members 15 and 16 and in effect constitute electric potentials opposing the potentials which created them and hence terminate the discharge. However, on a succeeding half cycle of applied potential, potential of the stored charges, being in the same direction, aid in initiating the next discharge and constitute an electrical memory. Because of the gas being at a relatively high pressure and separated from the operating conductors by dielectric material, relatively high periodic alternating potentials are required in order to sustain discharges once initiated. At the present time, typical sustaining voltage for a neon-argon panel lies within the range of 260 to 310 volts peak to peak at a frequency or rate of from about 30 to 50 kH.sub.z with two microsecond high voltage pulses superimposed or added to the sustaining voltage to manipulate the discharge condition of selected discharge sites. The operating voltage may be lowered further by a non-conductive overcoat or layer (not shown) such as a layer or coating lead oxide of a few angstroms thick on dielectric layers 15 and 16. The normal magnitude of pulse potential (added to the sustainer) required to initiate a discharge (assuming, of course, that the gas has been conditioned by ultra-violet or by other means as disclosed in the aforementioned patent application) is about the same as the sustaining potential.

Normally voltages from a computer or standard commercially available logic circuitry is in a neighborhood of four volts. In order to interface such low level signals with panels requiring voltages around 100 times larger is the problem with which the present invention deals.

As shown in the drawing, each conductor 14-1, 14-2, 14-3 . . . 14-n of conductor array 14 and each conductor 13-1, 13-2, 13-3 . . . and 13-n of conductor array 13 is supplied with sustainer voltages from sources 33A and 33B on which the multiplex circuit systems impose an additional voltage pulse to constitute the firing voltage for a selected site.

Each row conductor in conductor array 14 and each column conductor in conductor array 13 is provided with its own driving or interface circuit, which, in the drawings are designated as "x-axis high voltage pulsers" and "x-axis logic decoder and control" for row conductors 14-1, 14-2, 14-3, 14-n, respectively, "y-axis high voltage pulsers" and "y-axis logic decoders and control" for column conductors 13. It will be appreciated that panel 10 will usually have many more conductors and conductor arrays 13 and 14, available panels having the conductors on 30 mil centers so that in a four inch display area in a panel there may be about 132 row conductors and 132 column conductors.

These circuits (the high voltage pulsers and logic decoder and control) may be of the type disclosed in O'Brien application Ser. No. 147,765 filed May 28, 1971, "High Voltage Pulser Circuit For Driving Row-Column Conductor Arrays of a Gas Discharge Display Capable of Being Made in Integrated Form", or O'Brien application Ser. No. 147,764 filed May 28, 1971 and entitled "Low Voltage Pulser Circuit For Driving Row-Column Conductor Arrays of a Gas Discharge Display Capable of Being Made in Integrated Circuit Form," both assigned to the assignee hereof.

The sustaining voltage from sustaining voltage generator 33-A constitutes one-half the sustaining potential necessary to be applied across the gas in the discharge gap in the panel to sustain discharges once initiated. Oppositely phases sustaining voltage (Vs/2) from sustaining generator 33-B is applied to column conductors 13 through the x and y axis logic and high voltage pulser circuits as shown.

The input ends of light bearing fiber elements 40 are in close optically coupled relation with respect to light emitting diodes 41, there being a light emitting diode 41 and a corresponding fiber optic element 40 with the cathodes thereof commonly connected together and to the common system ground. Any four volt pulse as for example, a four volt logic pulse from logic-addressing circuit 50 causes the light emitting diode to which it is applied to emit light.

Logic and control information signals from logic addressing signal source 50 are coupled to the "x-axis logic decoder and control" and the "y-axis logic decoder and control" by means of fiber optic elements. As shown, fiber optic elements 40-S and 40-B.sub.1 and 40-B.sub.2 are used to convey information to a photon coupling section 60 in the "x-axis" system and fiber optic elements 45-S and 45-B.sub.1 and 45-B.sub.2 carry information to photon coupling section 70 in the "y-axis" system. The photon couple sections are per se, conventional and include a photosensitive diode or transistor (not shown) for each fiber optic element to convert the bursts of radient energy issuing from the ends of the fiber optic elements to bursts or pulses of electricl energy useful for further processing. Thus, the circuit configuration of my application Ser. No. 851,131 may be adopted to convert the radient energy pulses to voltage pulses, but at a relatively low voltage level for the decoder. In the drawing the fiber optic elements 40-S and 45-S carry strobe or enabling pulses whereas the fiber optic elements 40-B.sub.1 and 40-B.sub.2 and 45-B.sub.1 and 45-B.sub.2 carry binary information bits or data, it being appreciated that the number of said fiber optic elements carrying binary bits or data would be larger than the two shown for each axis.

As exemplified in the above identified O'Brien applications the row strobe or enable pulses, in conjunction with the decoding of the binary bits carried by fiber optic elements 40-B.sub.1 and 40-B.sub.2, are capable of selectively applying a high voltage pulse on one of row conductors 14-1 . . . 14-N, which is algebraically added to the sustainer voltage for that axis; and a like action takes place with respect to the information channels in the "y-axis" circuits.

As noted earlier, the sustaining voltage sources 33-A and 33-B produce oppositely phase sustaining voltages so that one-half the required sustaining voltage is applied to column conductors 13 and 1/2 the required sustaining voltage is applied to row conductor 14. Logic signal voltages applied to light sensitive diodes 41 are applied simultaneously to selected pairs of conductors, the crossing points of which defines a selected discharge site which it is desired to manipulate the discharge condition thereof.

A feature of the circuit is that a four volt pulse, referenced to ground, may be used to control a very high voltage (300 volt) pulse that is referenced to or floats on a sine waveform or other periodic wave form. The fiber optic elements effectively isolates the two signals such that a 300 volt signal does not couple back into the four volt system. In addition, there a fewer components per interface circuit. In the circuit disclosed, the high voltage pulsing circuit is isolated from the source of control signals via the optical coupling but other forms of isolation may be used so as to permit the pulse signals to be referenced to the sustaining voltage. However, alternative coupling means typified by pulsed transformers or capacitor-resistor coupling have inherent impedances which do not yield as good an isolation as the photon coupler. The resulting inherent impendance in these types of couplers, principally the primary to secondary capacitance in the transformer, produces a potential electrical spurious signal condition. Through the use of photon couplers, the path of the capacitive surge currents resulting from the sustainer switching action can be completely controlled and not be allowed to introduce noise into the logic by the flow of this current through the logic.

Claims

What is claimed is:

1. In a system for supplying operating potentials to a gas discharge panel device of the type in which a thin gas discharge medium under pressure and bounded by dielectric charge storage members has the discharge condition of selected discharge sites therein manipulated by selectively applied high voltage pulses and discharges maintained once initiated by a pair of relatively high, periodic sustaining voltages from a pair of sources by means of a pair of transverse row and column conductor arrays defining the discharge sites and wherein voltages from a relatively low voltage signal pulse source determine the occurrence of said high voltage pulses, each said source of sustaining potential having a pair of output terminals, respectively, and means connecting one of said terminals from each source of sustaining potential to each other and a point of common potential so that said relatively high sustaining voltage sources being connected to conductors of said array respectively such that said panel floats with respect to a point of common potential, the improvement comprising,

multiplex circuit system for receiving pairs of said low voltage signal pulses and converting same to said high voltage level pulses, which high voltage level pulses are referenced to said sustainer voltage respectively,

said multiplex circuit system including at least a pair of high voltage pulser means, one high voltage pulser means for said row conductor array and one high voltage pulser means for said column conductor arrays, respectively, means connecting one said high voltage pulser means in series between one of said pair of sources of periodic sustaining voltage and the row conductors of said panels and the other of said high voltage pulser means in series between the other of said pair of sources of periodic sustaining voltage,

means for applying each of said pair of relatively low voltage signal pulses to respective ones of said high voltages pulse means to cause said high voltage pulser means to generate high voltage pulses having as a reference point the magnitude of said voltage periodic voltage from the one of said pair of sources it is connected with in said series relation.