Gas discharge display system with current suppression means

Claim 2

A gas discharge display device comprising first and second groups of output transistors, first and second control circuits coupled to said first and second groups of output transistors, respectively, for controlling the conduction in said output transistors, a gas discharge display tube comprising a first electrode system arranged in a discharge space of the tube and having a plurality of electrodes coupled to output electrodes of the first group of output transistors, means connecting further electrodes of said first group of output transistors to a terminal of an electric supply source, capacitance means, said display tube including a second electrode system arranged in the tube discharge space and having a plurality of electrodes capacitively coupled via said capacitor means to output electrodes of the second group of output transistors, means connecting further electrodes of said second group of output transistors to a point of substantially the same potential as the said supply source terminal, a switch coupled to the first control circuit for suppressing the current through the display device when the electrodes of the first electrode system are not energized, and means for coupling the output electrodes of the second group of output transistors through a load impedance means and said switch to a further terminal of the supply source.

Claim 3

A gas discharge diSplay device as claimed in claim 1 wherein the load impedance means comprises a plurality of current sources.

Claim 4

A display device as claimed in claim 1 wherein said coupling means is arranged to connect the load impedance means and the switch in series between the output electrodes of the second group of transistors and the further terminal of the supply source.

Claim 5

A display system comprising, a gas discharge display tube having first and second electrode systems comprising a first and a second plurality of electrodes, respectively, first and second groups of output transistors, first and second control means coupled to said first and second groups of output transistors, respectively, for controlling the conduction in said first and second groups of output transistors, first and second terminals for supplying operating voltages to the display tube, means individually connecting the first plurality of tube electrodes to output electrodes of the first group of transistors, means connecting further electrodes of said first group of output transistors to the first supply terminal, capacitor means, means including said capacitor means for coupling the second plurality of tube electrodes to output electrodes of the second group of output transistors, means connecting further electrodes of said second group of output transistors to a voltage substantially the same as that of the first voltage supply terminal, a controlled switch for suppressing the current through the display device when the electrodes of the first electrode system are deenergized and including a control electrode coupled to the first electrode system, load impedance means, and means for coupling the output electrodes of the second group of output transistors through said load impedance means and said controlled switch to the second voltage supply terminal.

Claim 6

A display system comprising, a gas discharge display tube having first and second electrode systems comprising a first and a second plurality of electrodes, respectively, first and second groups of output transistors, first and second control means coupled to said first and second groups of output transistors, respectively, for controlling the conduction in said first and second groups of output transistors, first and second terminals for supplying operating voltages to the display tube, means individually connecting the first plurality of tube electrodes to output electrodes of the first group of transistors, means connecting further electrodes of said first group of output transistors to the first supply terminal, capacitor means, means including said capacitor means for coupling the second plurality of tube electrodes to output electrodes of the second group of output transistors, means connecting further electrodes of said second group of output transistors to a voltage substantially the same as that of the first voltage supply terminal, a controlled switch for suppressing the current through the display device when the electrodes of the first electrode system are deenergized and including a control electrode coupled to the first electrode system, load impedance means, and means for coupling the output electrodes of the second group of output transistors through said load impedance means and said controlled switch to the second voltage supply terminal.

Claim 7

A display system as claimed in claim 4 further comprising diode means coupling the electrodes of the second electrode system to a third operating voltage supply terminal of the system.

Claim 8

A display system as claimed in claim 4 wherein said load impedance means comprises a plurality of transistors connected to operate as current sources and connected in series with the controlled switch to the second voltage supply terminal and individually connected to the output electrodes of the second group of output transistors.

Claim 9

A display system as claimed in claim 6 wherein said capacitor means comprises a plurality of capacitors connected between the electrodes of the second electrode system and the junction points formed between the output electrodes of the second group of output transistors and the current source transistors.

Claim 10

A display system as claimed in claim 4 wherein the control electrode of the controlled switch is connected to the first control means via said first group of output transistors.

Claim 11

A display system as claimed in claim 4 wherein said further electrodes of the second group of output transistors are connected to said first voltage supply terminal.

Claim 12

A display system as claimed in claim 4 wherein said coupling means is arranged to connect said load impedance means and said controlled switch in series between the output electrodes of the second group of transistors and said second voltage supply terminal, and said control electrode is responsive to the voltage at said first electrode system to turn on the controlled switch if at least one of the electrodes of the first electrode system is energized with a display voltage.