Supply circuit for a gas discharge character display tube

Claim 2

A display system comprising a gas discharge character segment display tube in which segments of characters can be displayed by means of a plurality of cathodes, said display tube comprising a plurality of electrodes including at least one anode electrode and at least two cathode electrodes cooperating with said anode, at least one of the tube cathodes being common to different characters to be displayed, and a stabilised current source circuit for supplying the tube anode voltage and one of said cathodes of the gas discharge character display tube with a substantially constant current and including a measuring resistor connected in the cathode circuit of said common cathode, said current source circuit being responsive to a voltage developed across said resistor for controlling the tube anode supply voltage so as to maintain the voltage across the resistor constant.

Claim 3

A display system as claimed in claim 1, further comprising a plurality of resistors each connected individually in a different cathode circuit of the display tube, at least one other tube cathode being common to different characters to be displayed, and means for coupling said one common cathode and said one other common cathode through a gating circuit of the OR-type to a control input of the stabilised current source circuit.

Claim 4

A display system as claimed in claim 2, characterized in that the resistors in the cathode circuits each have a value which varies with the active surface of the corresponding cathodes.

Claim 5

A display system as claimed in claim 1 wherein the gas discharge character segment display tube is of the multiple matrix type for the substantially simultaneous display of a plurality of characters and having a common cathode for each character, and means for coupling the common cathodes through a gating circuit to a control input of the stabilised current source circuit.

Claim 6

A display system as claimed in claim 1 wherein the display tube includes an auxiliary cathode shielded from visual observation, and means connecting the measuring resistor in the cathode circuit of said auxiliary cathode.

Claim 7

A display system comprising a gas discharge character segment display tube, said tube comprising a plurality of electrodes including at least one anode electrode and a plurality of cathode electrodes cooperatively disposed to said anode, at least one of the tube cathodes being common to different characters to be displayed, a regulated source of current having output terminals coupled to the tube electrodes to supply operating voltages across the tube anode-cathode circuits, a measuring resistor connected in the cathode circuit of said common cathode across which a control voltage is derived from the current supplied by said regulated current source, and means for applying said control voltage to a control input terminal of the regulated current source, said regulated current source including means responsive to said control voltage for controlling the tube operating voltage in a manner to maintain the voltage across said resistor substantially constant whereby at least one electrode of the display tube draws a substantially constant current from the regulated current source.

Claim 8

A display system comprising a gas discharge character segment display tube, said tube comprising a plurality of electrodes including at least one anode electrode and a plurality of cathode electrodes cooperatively disposed to said anode, at least one of the tube cathodes being common to different characters to be displayed, a regulated source of current having output terminals coupled to the tube electrodes to supply operating voltages across the tube anode-cathode circuits, a measuring resistor connected in the cathode circuit of said common cathode across which a control voltage is derived from the current supplied by said regulated current source, and means for applying said control voltage to a control input terminal of the regulated current source, said regulated current source including means responsive to said control voltage for controlling the tube operating voltage in a manner to maintain the voltage across said resistor substantially constant whereby at least one electrode of the display tube draws a substantially constant current from the regulated current source.

Claim 9

A display system as claimed in claim 6 further comprising a plurality of resistors each individually connected to a given one of the cathodes of said display tube, at least one other of said tube cathodes being common to the different characters to be displayed, and a diode gate circuit for coupling the common cathodes to the control input terminal of the regulated current source.

Claim 10

A display system as claimed in claim 6 wherein the display tube includes a second anode and a second plurality of cathodes cooperatively disposed therewith, means for connecting cathodes of the first group of cathodes to the corresponding cathodes of the second group of cathodes, first and second switching devices for coupling the first and second anodes, respectively, to one output terminal of the current source, a plurality of other switching devices each coupled individually to a pair of corresponding cathodes of the first and second group of cathodes to selectively control cathode current, and a decoding circuit having output terminals coupled to said switching devices for switching same in accordance with the characters to be displayed.

Claim 11

A display system as claimed in claim 8 wherein at least one cathode of the second group of cathodes is common to the different characters to be displayed and includes a measuring resistor in the cathode circuit thereof for deriving a control voltage, and a gating circuit for coupling all of said common cathodes to the control input of the regulated current source.

Claim 12

A display system as claimed in claim 6 wherein the display tube includes an auxiliary cathode shielded from view and common to the different characters to be displayed, and wherein said measuring resistor is connected in the cathode circuit of said auxiliary cathode.