Visual display apparatus including a liquid crystal display panel

Claim 2

Visual display apparatus comprising: A. a liquid crystal display panel; B. direct voltage supply means comprising first and second terminals; C. controllable semiconductor impedance means connected to form a parallel circuit with said display panel; D. a pulse voltage source connected to said semiconductor means to cause said semiconductor means to be alternately conductive and nonconductive; and E. means for rapidly reducing said pulse voltage to substantially zero by short circuiting said direct voltage supply means comprising an impedance connected in series with said source of direct voltage and said parallel circuit whereby the voltage across means for controlling said display is reduced substantially to zero when said semiconductor means is conductive.

Claim 3

The visual display apparatus of claim 1, wherein said semiconductor means comprises a transistor having a base, an emitter, and a collector, said base being connected to said pulse source, and said emitter and collector of the transistor being connected in parallel with said display and in series with said direct voltage supply means.

Claim 4

The visual display apparatus of claim 2, wherein said impedance comprises a second transistor of opposite conductivity type with respect to said first-named transistor and having a base, an emitter, and a collector, the base of the second transistor being connected to said pulse source, the emitter-collector circuit of said second transistor being connected in series with said voltage supply means and the emitter-collector circuit of said first transistor.

Claim 5

The visual display apparatus of claim 3 in which said pulse source comprises: A. a third transistor having a base, an emitter and a collector; B. a collector load in series with the emitter-collector circuit of said third transistor; and C. positive feedback circuit means connected between said third transistor and said first-named transistor to produce voltage pulses at s aid base of said first-named transistor.

Claim 6

The visual display apparatus of claim 1 in which said display panel comprises a plurality of indicia segments and said apparatus comprises, in addition, a logic circuit connected in series with said display panel to control connection of selected ones of said segments in said parallel circuit.

Claim 7

The visual display apparatus of claim 4 in which said collector load comprises a fourth transistor having a base, an emitter and a collector, the emitter-collector circuit of said fourth transistor being connected in series with said emitter-collector circuit of said third transistor.

Claim 8

The visual display apparatus of claim 6 in which said third transistor is of the same conductivity type as said first-named transistor and said fourth transistor is of the same conductivity type as said second transistor, and said feedback circuit means comprises: A. a first capacitor connected in series between the collector of said first-named transistor to the base of said third transistor; B. a second capacitor connected in series between the collector of said third transistor to the base of said first-named transistor; C. a first resistor connected in series between the base of said fourth transistor and the collector of said first-named transistor; and D. a second resistor connected in series between the base of said second transistor and the collector of said third transistor, whereby said first-named and said fourth transistors are conductive simultaneously and said second and third transistors are conductive simultaneously.