Dimming circuit for dual display aircraft instruments

Claim 2

A dimming circuit responsive to the magnitude of a supply voltage produced by a variable voltage source for controlling first and second lamps in a dual display, said dimming circuit comprising: (a) input means for receiving the supply voltage produced by the variable voltage source and producing an input voltage whose magnitude tracks the supply voltage produced by the variable voltage source; (b) threshold voltage means for receiving the supply voltage produced by the variable voltage source and producing a threshold voltage having a high value when the supply voltage produced by the variable voltage source has a high value and a low value when the supply voltage produced by the variable voltage source has a low value, such that said high value of said threshold voltage is substantially greater than the magnitude of said input voltage and said low value of said threshold voltage is substantially less than the magnitude of said input voltage; and, (c) a switch having a first input coupled to receive said input voltage, a second input coupled to receive said threshold voltage, a first output coupled to the first lamp of the dual display, and a second output coupled to the second lamp of the dual display, said switch being responsive to said input voltage and said threshold voltage, such that when said threshold voltage exceeds said input voltage said switch produces a low voltage at said first output of said switch that causes the first lamp to be brightly lit and a high voltage at said second output of said switch that causes the second lamp to be off and, such that when said threshold voltage is less than said input voltage said switch produces a high voltage at said first output of said switch that causes the first lamp to be off and a low voltage at said second output of said switch that causes the second lamp to be dimly lit.

Claim 3

The dimming circuit claimed in claim 1, wherein said threshold voltage means comprises: (a) a reference voltage supply coupled to the variable voltage source for producing a reference voltage; (b) a second voltage divider coupled to the variable voltage source for dividing the supply voltage produced by the variable voltage source and producing a lower magnitude supply voltage whose magnitude tracks the supply voltage produced by the variable voltage source; and, (c) a reference comparator for comparing said reference voltage and said lower magnitude supply voltage and producing said threshold voltage, such that said threshold voltage has said high value when the magnitude of said lower magnitude supply voltage exceeds the magnitude of said reference voltage and said threshold voltage has said low value when the magnitude of said lower magnitude supply voltage is less than the magnitude of said reference voltage.

Claim 4

The dimming circuit claimed in claim 2, wherein said input means is a first voltage divider.

Claim 5

The dimming circuit claimed in claim 1, wherein said switch comprises: (a) a first comparator coupled to receive said input voltage and said threshold voltage, such that the output of said first comparator forms said first output of said switch; and, (b) a second comparator coupled to receive said input voltage and said threshold voltage, such that the output of said second comparator forms said second output of said switch.

Claim 6

The dimming circuit claimed in claim 4, wherein said threshold voltage means comprises: (a) a reference voltage supply coupled to the variable voltage source for producing a reference voltage; (b) a second voltage divider coupled to the variable voltage source for dividing the supply voltage produced by the variable voltage source and producing a lower magnitude supply voltage whose magnitude tracks the supply voltage produced by the variable voltage source; and, (c) a reference comparator for comparing said reference voltage and said lower magnitude supply voltage and producing said threshold voltage, such that said threshold voltage has said high value when the magnitude of said lower magnitude supply voltage exceeds the magnitude of said reference voltage and said threshold voltage has said low value when the magnitude of said lower magnitude supply voltage is less than said threshold voltage.

Claim 7

The dimming circuit claimed in claim 5, wherein said input means is a first voltage divider.

Claim 8

The dimming circuit claimed in claim 6, wherein the magnitude of said input voltage is substantially equal to one-half the magnitude of the supply voltage produced by the variable voltage source.

Claim 9

The dimming circuit claimed in claim 6, wherein said dimming circuit is formed as an integrated circuit.

Claim 10

The dimming circuit claimed in claim 1, wherein said dimming circuit is formed as an integrated circuit.

Claim 11

An aircraft instrument dual display assembly coupled to a variable voltage source, said assembly comprising: (a) a dual display mounted in a housing and having a first indicia, a second indicia, a first lamp capable of illuminating said first indicia, and a second lamp capable of illuminating said second indicia; and, (b) dimming means responsive to a supply voltage produced by the variable voltage source for controlling the illumination of said first and second indicia by said first and second lamps, such that when the magnitude of the supply voltage is high said dimming means causes said first lamp to be brightly lit and said second lamp to be off, and when the magnitude of the supply voltage is low said dimming means causes said first lamp to be off and said second lamp to be dimly lit, said dimming means comprising: (1) input means for receiving the supply voltage produced by the variable voltage source and producing an input voltage whose magnitude tracks the supply voltage produced by the variable voltage source; (2) threshold voltage means for receiving the supply voltage produced by the variable voltage source and producing a threshold voltage having a high value when the supply voltage produced by the variable voltage source has a high value and a low value when the supply voltage produced by the variable voltage source has a low value, such that said high value of said threshold voltage is substantially greater than the magnitude of said input voltage and said low value of said threshold voltage is substantially less than the magnitude of said input voltage; and, (3) a switch having a first input coupled to receive said input voltage, a second input coupled to receive said threshold voltage, a first output coupled to said first lamp of said dual display, and a second output coupled to said second lamp of said dual display, said switch being responsive to said input voltage and said threshold voltage, such that when said threshold voltage exceeds said input voltage said switch produces a low voltage at said first output of said switch that causes said first lamp to be brightly lit and a high voltage at said second output of said switch that causes said second lamp to be off, and such that when said threshold voltage is less than said input voltage said switch produces a high voltage at said first output of said switch that causes said first lamp to be off and a low voltage at said second output of said switch that causes said second lamp to be dimly lit.

Claim 12

An aircraft instrument dual display assembly coupled to a variable voltage source, said assembly comprising: (a) a dual display mounted in a housing and having a first indicia, a second indicia, a first lamp capable of illuminating said first indicia, and a second lamp capable of illuminating said second indicia; and, (b) dimming means responsive to a supply voltage produced by the variable voltage source for controlling the illumination of said first and second indicia by said first and second lamps, such that when the magnitude of the supply voltage is high said dimming means causes said first lamp to be brightly lit and said second lamp to be off, and when the magnitude of the supply voltage is low said dimming means causes said first lamp to be off and said second lamp to be dimly lit, said dimming means comprising: (1) input means for receiving the supply voltage produced by the variable voltage source and producing an input voltage whose magnitude tracks the supply voltage produced by the variable voltage source; (2) threshold voltage means for receiving the supply voltage produced by the variable voltage source and producing a threshold voltage having a high value when the supply voltage produced by the variable voltage source has a high value and a low value when the supply voltage produced by the variable voltage source has a low value, such that said high value of said threshold voltage is substantially greater than the magnitude of said input voltage and said low value of said threshold voltage is substantially less than the magnitude of said input voltage; and, (3) a switch having a first input coupled to receive said input voltage, a second input coupled to receive said threshold voltage, a first output coupled to said first lamp of said dual display, and a second output coupled to said second lamp of said dual display, said switch being responsive to said input voltage and said threshold voltage, such that when said threshold voltage exceeds said input voltage said switch produces a low voltage at said first output of said switch that causes said first lamp to be brightly lit and a high voltage at said second output of said switch that causes said second lamp to be off, and such that when said threshold voltage is less than said input voltage said switch produces a high voltage at said first output of said switch that causes said first lamp to be off and a low voltage at said second output of said switch that causes said second lamp to be dimly lit.

Claim 13

The assembly claimed in claim 10, wherein said dual display further comprises an optical filter for filtering the light energy produced by said second lamp.

Claim 14

The assembly claimed in claim 11, wherein said optical filter is a night vision goggle compatible filter.

Claim 15

The assembly claimed in claim 12, wherein said night vision goggle compatible filter filters light energy in the 600-900 nm range.

Claim 16

The assembly claimed in claim 12, wherein said dimming means is an integrated circuit mounted in said housing of said dual display.

Claim 17

The assembly claimed in claim 10, wherein said switch comprises: (a) a first comparator coupled to receive said input voltage and said threshold voltage, such that the output of said first comparator forms said first output of said switch; and, (b) a second comparator coupled to receive said input voltage and said threshold voltage, such that the output of said second comparator forms said second output of said switch.

Claim 18

The assembly claimed in claim 15, wherein said threshold voltage means comprises: (a) a reference voltage supply coupled to the variable voltage source for producing a reference voltage; (b) a second voltage divider coupled to the variable voltage source for dividing the supply voltage produced by the variable voltage source and producing a lower magnitude supply voltage whose magnitude tracks the supply voltage produced by the variable voltage source; and, (c) a reference comparator for comparing said reference voltage and said lower magnitude supply voltage and producing said threshold voltage, such that said threshold voltage has said high value when the magnitude of said lower magnitude supply voltage exceeds the magnitude of said reference voltage and said threshold voltage has said low value when the magnitude of said lower magnitude supply voltage is less than the magnitude of said reference voltage.

Claim 19

The assembly claimed in claim 16, wherein said input means is a first voltage divider.

Claim 20

The assembly claimed in claim 17, wherein said dimming means is a dimming circuit formed as an integrated circuit.

Claim 21

The assembly claimed in claim 18, wherein said dimming circuit is mounted in said housing of said dual display.

Claim 22

A switching network responsive to the magnitude of a supply voltage produced by a variable voltage source, said switching network comprising: (a) input means for receiving the supply voltage produced by the variable voltage source and producing an input voltage whose magnitude tracks the supply voltage produced by the variable voltage source over its range; (b) threshold voltage means for receiving the supply voltage produced by the variable voltage source and producing a threshold voltage having a high value when the supply voltage produced by the variable voltage source has a high value and a low value when the supply voltage produced by the variable voltage source has a low value, such that said high value of said threshold voltage is substantially greater than the magnitude of said input voltage and said low value of said threshold voltage is substantially less than the magnitude of said input voltage; and, (c) a switch having a first input coupled to receive said input voltage, a second input coupled to receive said threshold voltage, and first and second outputs, said switch being responsive to said input voltage and said threshold voltage, such that when said threshold voltage exceeds said input voltage said switch produces a low voltage at said first output of said switch and a high voltage at said second output of said switch and, such that when said threshold voltage is less than said input voltage said switch produces a high voltage at said first output of said switch and a low voltage at said second output of said switch.

Claim 23

A switching network responsive to the magnitude of a supply voltage produced by a variable voltage source, said switching network comprising: (a) input means for receiving the supply voltage produced by the variable voltage source and producing an input voltage whose magnitude tracks the supply voltage produced by the variable voltage source over its range; (b) threshold voltage means for receiving the supply voltage produced by the variable voltage source and producing a threshold voltage having a high value when the supply voltage produced by the variable voltage source has a high value and a low value when the supply voltage produced by the variable voltage source has a low value, such that said high value of said threshold voltage is substantially greater than the magnitude of said input voltage and said low value of said threshold voltage is substantially less than the magnitude of said input voltage; and, (c) a switch having a first input coupled to receive said input voltage, a second input coupled to receive said threshold voltage, and first and second outputs, said switch being responsive to said input voltage and said threshold voltage, such that when said threshold voltage exceeds said input voltage said switch produces a low voltage at said first output of said switch and a high voltage at said second output of said switch and, such that when said threshold voltage is less than said input voltage said switch produces a high voltage at said first output of said switch and a low voltage at said second output of said switch.

Claim 24

The switching network claimed in claim 20, wherein said switch comprises: (a) a first comparator coupled to receive said input voltage and said threshold voltage, such that the output of said first comparator forms said first output of said switch; and, (b) a second comparator coupled to receive said input voltage and said threshold voltage, such that the output of said second comparator forms said second output of said switch.

Claim 25

The switching network claimed in claim 21, wherein said threshold voltage means comprises: (a) a reference voltage supply coupled to the variable voltage source for producing a reference voltage; (b) a second voltage divider coupled to the variable voltage source for dividing the supply voltage produced by the variable voltage source and producing a lower magnitude supply voltage whose magnitude tracks the supply voltage produced by the variable voltage source; and, (c) a reference comparator for comparing said reference voltage and said lower magnitude supply voltage and producing said threshold voltage, such that said threshold voltage has said high value when the magnitude of said lower magnitude supply voltage exceeds the magnitude of said reference voltage and said threshold voltage has said low value when the magnitude of said lower magnitude supply voltage is less than the magnitude of said reference voltage.

Claim 26

The switching network claimed in claim 22, wherein said input means is a first voltage divider.

Claim 27

The switching network claimed in claim 23, wherein said switching network is formed as an integrated circuit.

Claim 28

The switching network claimed in claim 20, wherein said switching network is formed as an integrated circuit.