EP0044152A2
Expired / Lapsed
EP
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Liquid crystal display system having improved temperature compensation
Assignee: Texas Instruments Inc
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Filing: 1981-06-26
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Granted: —
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Expires: 2001-06-26
Abstract
Abstract A liquid crystal display system having improved temperature compensation based upon electrical measurement of liquid crystal display segment capacitance. The capacitance of a segment is measured when preconditioned to a first voltage below the threshold voltage and when preconditioned to a second voltage above the threshold voltage. Separate embodiments are disclosed which sequentially measure the capacitance of a single segment or which simultaneously measures the capacitance of two segments. The magnitude of the second voltage is adjusted to converge the ratio of the measured capacitances to a predetermined fixed value or a predetermined value selected according to the display temperature. A preferred embodiment is a display system (16) which accepts digit data for storage in a digit shift register (22) or segment data for storage in a segment shift register (24). In accordance with mode signals received by a format control (20), a sequence control (26) cooperates with a ROM (28) to convert digit data to segment data. A temperature compensator (36) cooperates with a voltage regulator (32) to generate the required drive voltages for the display as fixed percentages of the second voltage.
Inventors
- 👤 Jerald G. Leach
- 👤 Howard R. Test Ii
- 👤 Michael J. Drury
- 👤 Robert H. Woodside
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-26 14:08
CPC Classifications
G; G02; G02F; G02F1/00; G02F1/01; G02F1/13; G02F1/133; G02F1/1333; G02F1/133382; G09; G09G; G09G3/00; G09G3/04; G09G3/16; G09G3/18
Claims Analysis
Total Claims: 54
Claim 1
Independent Claim
71 words
A liquid crystal display system comprising: a liquid crystal display segment; display drive means for alternately coupling the segment to first and second voltages; and temperature compensation means for determining the ratio of the capacitance of the segment when coupled to the first voltage to the capacitance of the segment when coupled to the second voltage, and for changing the second voltage to converge said ratio toward a predetermined ratio value.
Claim 2
Dependent Claim
71 words
A liquid crystal display system comprising: a liquid crystal display segment; display drive means for alternately coupling the segment to first and second voltages; and temperature compensation means for determining the ratio of the capacitance of the segment when coupled to the first voltage to the capacitance of the segment when coupled to the second voltage, and for changing the second voltage to converge said ratio toward a predetermined ratio value.
Claim 3
Dependent Claim
16 words
The display system of Claim 1 wherein the first and second voltages have predetermined RMS values.
Claim 4
Dependent Claim
19 words
The display system of Claim 2 wherein the second voltage is changed by varying the duty cycle blanking thereof.
Claim 5
Dependent Claim
24 words
The display system of Claim 1 or 2 wherein the first voltage has a predetermined value below a predetermined threshold voltage of said segment.
Claim 6
Dependent Claim
21 words
The display system of Claim 4 wherein the second voltage has a selected value above said threshold voltage of said segment.
Claim 7
Dependent Claim
82 words
A display drive circuit for use in a liquid crystal display system having a liquid crystal display segment, the drive circuit comprising: display drive means for alternately coupling the segment to first and second voltages; and temperature compensation means for determining the ratio of the capacitance of the segment when coupled to the first voltage to the capacitance of the segment when coupled to the second voltage, and for changing the second voltage to converge said ratio toward a predetermined ratio value.
Claim 8
Dependent Claim
82 words
A display drive circuit for use in a liquid crystal display system having a liquid crystal display segment, the drive circuit comprising: display drive means for alternately coupling the segment to first and second voltages; and temperature compensation means for determining the ratio of the capacitance of the segment when coupled to the first voltage to the capacitance of the segment when coupled to the second voltage, and for changing the second voltage to converge said ratio toward a predetermined ratio value.
Claim 9
Dependent Claim
17 words
The display drive circuit of Claim 6 wherein the first and second voltages have predetermined RMS values.
Claim 10
Dependent Claim
20 words
The display drive circuit of Claim 7 wherein the second voltage is changed by varying the duty cycle blanking thereof.
Claim 11
Dependent Claim
25 words
The display drive circuit of Claim 6 or 7 wherein the first voltage has a predetermined value below a predetermined threshold voltage of said segment.
Claim 12
Dependent Claim
22 words
The display drive circuit of Claim 9 wherein the second voltage has a selected value above said threshold voltage of said segment.
Claim 13
Dependent Claim
83 words
A liquid crystal display system comprising: first and second liquid crystal display segments; display drive means for coupling the first segment to a predetermined first voltage, and the second segment to a second voltage; and temperature compensation means for determining the ratio of the capacitance of the first segment when coupled to the first voltage to the capacitance of the second segment when coupled to the second voltage, and for changing the second voltage to converge said ratio toward a predetermined ratio value.
Claim 14
Dependent Claim
83 words
A liquid crystal display system comprising: first and second liquid crystal display segments; display drive means for coupling the first segment to a predetermined first voltage, and the second segment to a second voltage; and temperature compensation means for determining the ratio of the capacitance of the first segment when coupled to the first voltage to the capacitance of the second segment when coupled to the second voltage, and for changing the second voltage to converge said ratio toward a predetermined ratio value.
Claim 15
Dependent Claim
16 words
The display system of Claim 11 wherein the first and second voltages have predetermined RMS values.
Claim 16
Dependent Claim
19 words
The display system of Claim 12 wherein the second voltage is changed by varying the duty cycle blanking thereof.
Claim 17
Dependent Claim
24 words
The display system of Claim 11 or 12 wherein the first voltage has a predetermined value below a predetermined threshold voltage of said segment.
Claim 18
Dependent Claim
22 words
The display system of Claim 14 wherein the second voltage has has a selected value above said threshold voltage of said segment.
Claim 19
Dependent Claim
92 words
A display drive circuit for use in a liquid crystal display system having first and'second liquid crystal display segments, the drive circuit comprising: display drive means for coupling the first segment to a first voltage, and the second segment to a second voltage; and temperature compensation means for determining the ratio of the capacitance of the first segment when coupled to the first voltage to the capacitance of the second segment when coupled to the second voltage, and for changing the second voltage to converge said ratio toward a predetermined ratio value.
Claim 20
Dependent Claim
92 words
A display drive circuit for use in a liquid crystal display system having first and'second liquid crystal display segments, the drive circuit comprising: display drive means for coupling the first segment to a first voltage, and the second segment to a second voltage; and temperature compensation means for determining the ratio of the capacitance of the first segment when coupled to the first voltage to the capacitance of the second segment when coupled to the second voltage, and for changing the second voltage to converge said ratio toward a predetermined ratio value.
Claim 21
Dependent Claim
17 words
The display drive circuit of Claim 16 wherein the first and second voltages have predetermined RMS values.
Claim 22
Dependent Claim
20 words
The display drive circuit of Claim 17 wherein the second voltage is changed by varying the duty cycle blanking thereof.
Claim 23
Dependent Claim
25 words
The display drive circuit of Claim 16 or 17 wherein the first voltage has a predetermined value below a predetermined threshold voltage of said segment.
Claim 24
Dependent Claim
22 words
The display drive circuit of Claim 19 wherein the second voltage has a selected value above said threshold voltage of said segment.
Claim 25
Dependent Claim
113 words
A liquid crystal display system comprising: a liquid crystal display segment; a display drive means for alternatively coupling said display segment to first and second voltages; a capacitance ratio selection means, responsive to the temperature of said display segment, for selecting one of a plurality of predetermined ratio values, each predetermined ratio value corresponding to one of a plurality of temprature ranges; and a temperature compensation means for determining the ratio of the capacitance of said display segment when coupled to said first voltage to the capacitance of said display segment when coupled to said second voltage, and for changing said second voltage to converge said ratio to said selected predetermined ratio value.
Claim 26
Dependent Claim
113 words
A liquid crystal display system comprising: a liquid crystal display segment; a display drive means for alternatively coupling said display segment to first and second voltages; a capacitance ratio selection means, responsive to the temperature of said display segment, for selecting one of a plurality of predetermined ratio values, each predetermined ratio value corresponding to one of a plurality of temprature ranges; and a temperature compensation means for determining the ratio of the capacitance of said display segment when coupled to said first voltage to the capacitance of said display segment when coupled to said second voltage, and for changing said second voltage to converge said ratio to said selected predetermined ratio value.
Claim 27
Dependent Claim
152 words
The liquid crystal display system claimed in Claim 21, wherein said temperature compensation means comprises: a first charging means for charging said display. segment to a predetermined voltage at a predetermined first rate after said display drive means has coupled said display segment to said first voltage; a second charging means for charging said display segment to a predetermined voltage at a selected one of a a plurality of predetermined second rates corresponding to said selected predetermined ratio value after said display drive means has coupled said display segment to said second voltage; a timer means for measuring the first charging time of said first charging means and the second charging time of said second charging means; and a converging means for increasing said second voltage when said first charging time exceeds said second charging time and for decreasing said second voltage when said second charging time exceeds said first charging time.
Claim 28
Dependent Claim
135 words
The liquid crystal display system claimed in Claim 22, wherein: said display drive means includes a second voltage generator comprising a predetermined voltage source, a counter having a duty cycle blanking count stored therein and a duty cycle blanking means for generating said second voltage by blanking the voltage generated by said predetermined voltage source by a duty cycle ratio corresponding to said duty cycle blanking count; said capacitance ratio selection means being responsive to said duty cycle blanking count for selecting said predetermined ratio value depending upon said duty cycle blanking count; and said converging means comprises means for decrementing said duty cycle blanking count when said first charging time exceeds said second charging time and means for incrementing said duty cycle blanking count when said second charging time exceeds said first charging time.
Claim 29
Dependent Claim
162 words
The liquid crystal display system as claimed in Claim 23, wherein said capacitance ratio selection means comprises: a state counter having a plurality of states, each state corresponding to one of said plurality of predetermined ratio values; a plurality of count sensors, each responsive to said duty cycle blanking count for generating a coincidence signal when said duty cycle blanking count equals a respective predetermined count, and each associated with two states of said state counter corresponding to adjacent temperature ranges; and a state selector means, responsive to said count sensors and said timer means, for placing said state counter in said state associated with a count sensor generating an enable signal corresponding to the lower temperature range when said first charging time exceeds said second charging time and for placing said state counter in said state associated with a count sensor generating an enable signal corresponding to the higher temperature range when said second charging time exceeds said first charging time.
Claim 30
Dependent Claim
104 words
The liquid crystal display system claimed in Claim 21, further comprising: a plurality of liquid crystal display segments; an off voltage generator means for generating an ott voltage having a first predetermined ratio to said second voltage; an on voltage generator means for generating an on voltage having a second predetermined ratio to said second voltage, said second predetermined ratio being greater than said first predetermined ratio; and a display actuation means for coupling said on voltage to selected ones of said plurality of display segments for actuation thereof and for coupling said off voltage to the other of said plurality of display segments.
Claim 31
Dependent Claim
122 words
A display drive circuit for use in a liquid crystal display system having a liquid crystal display segment, said drive circuit comprising: a display drive means for alternately coupling said display segment to first and second voltages; a capacitance ratio selection means, responsive to the temperature of said display segment, for selecting one of a plurality of predetermined ratio values corresponding to one of a plurality of temperature ranges ; and, a temperature compensation means for determining the ratio of the capacitance of said display segment when coupled to said first voltage to the capacitance ratio of said display segment when coupled to said second voltage, and for changing said second voltage to converge said ratio to said selected predetermined ratio value.
Claim 32
Dependent Claim
122 words
A display drive circuit for use in a liquid crystal display system having a liquid crystal display segment, said drive circuit comprising: a display drive means for alternately coupling said display segment to first and second voltages; a capacitance ratio selection means, responsive to the temperature of said display segment, for selecting one of a plurality of predetermined ratio values corresponding to one of a plurality of temperature ranges ; and, a temperature compensation means for determining the ratio of the capacitance of said display segment when coupled to said first voltage to the capacitance ratio of said display segment when coupled to said second voltage, and for changing said second voltage to converge said ratio to said selected predetermined ratio value.
Claim 33
Dependent Claim
151 words
The liquid crystal display system claimed in Claim 26, wherein said temperature compensation means comprises: a first charging means for charging said display segment to a predetermined voltage at a predetermined first rate after said display drive means has coupled said display segment to said first voltage; a second charging means for charging said display segment to a predetermined voltage at a selected one of a plurality of predetermined second rates corresponding to said selected predetermined ratio value after said display drive means has coupled said display segment to said second voltage; a timer means for measuring the first charging time of said first charging means and the second charging time of said second charging means; and a converging means for increasing said second voltage when said first charging time exceeds said second charging time and for decreasing said second voltage when said second charging time exceeds said first charging time.
Claim 34
Dependent Claim
135 words
The liquid crystal display system claimed in Claim 27, wherein: said display drive means includes a second voltage generator comprising a predetermined voltage source, a counter having a duty cycle blanking count stored therein and a duty cycle blanking means for generating said second voltage by blanking the voltage generated by said predetermined voltage source by a duty cycle ratio corresponding to said duty cycle blanking count; said capacitance ratio selection means being responsive to said duty cycle blanking count for selecting said predetermined ratio value depending upon said duty cycle blanking count; and said converging means comprises means for decrementing said duty cycle blanking count when said first charging time exceeds said second charging time and means for incrementing said duty cycle blanking count when said second charging time exceeds said first charging time.
Claim 35
Dependent Claim
162 words
The liquid crystal display system as claimed in Claim 28, wherein said capacitance ratio selection means comprises: a state counter having a plurality of states, each state corresponding to one of said plurality of predetermined ratio values; a plurality of count sensors, each responsive to said duty cycle blanking count for generating a coincidence signal when said duty cycle blanking count equals a respective predetermined count, and each associated with two states of said state counter corresponding to adjacent temperature ranges; and a state selector means, responsive to said count sensors and said timer means, for placing said state counter in said state associated with a count sensor generating an enable signal corresponding to the lower temperature range when said first charging time exceeds said second charging time and for placing said state counter in said state associated with a count sensor generating an enable signal corresponding to the higher temperature range when said second charging time exceeds said first charging time.
Claim 36
Dependent Claim
104 words
The liquid crystal display system claimed in Claim 26, further comprising: a plurality of liquid crystal display segments; an off voltage generator means for generating an off voltage having a first predetermined ratio to said second voltage; an on voltage generator means for generating an on voltage having a second predetermined ratio to said second voltage, said second predetermined ratio being greater than said first predetermined ratio; and a display actuation means for coupling said on voltage to selected ones of said plurality of display segments for actuation thereof and for coupling said off voltage to the other- of said plurality of display segments.
Claim 37
Dependent Claim
133 words
A liquid crystal display system comprising: a first and second liquid crystal display segments; a display drive means for coupling said first display segment to a first voltage and for coupling said second display segment to a second voltage; a capacitance ratio selection means, responsive to the temperature of said display segments, for selecting one of a plurality of predetermined ratio values, each ratio value corresponding to one of a plurality of temperature ranges; and a temperature compensation means for determining the ratio of the capacitance of said first display segment when coupled to said first voltage to the capacitance of said second display segment when coupled to said second voltage and for changing said second voltage and for changing said second voltage to converge said ratio to said selected predetermined ratio value.
Claim 38
Dependent Claim
133 words
A liquid crystal display system comprising: a first and second liquid crystal display segments; a display drive means for coupling said first display segment to a first voltage and for coupling said second display segment to a second voltage; a capacitance ratio selection means, responsive to the temperature of said display segments, for selecting one of a plurality of predetermined ratio values, each ratio value corresponding to one of a plurality of temperature ranges; and a temperature compensation means for determining the ratio of the capacitance of said first display segment when coupled to said first voltage to the capacitance of said second display segment when coupled to said second voltage and for changing said second voltage and for changing said second voltage to converge said ratio to said selected predetermined ratio value.
Claim 39
Dependent Claim
158 words
The liquid crystal display system claimed in Claim 31, wherein said temperature compensator means comprises: a first charging means for charging said first display segment to a predetermined voltage at a predetermined first rate after said display drive means has coupled said first display segment to said first volrage; a second charging means for charging said second display segment to a predetermined voltage at a selected one of a plurality of predetermined second rates corresponding to said selected predetermined ratio value after said display drive means has coupled said second display segment to said second voltage; a charging time comparison means for determining the relationship of the first charging time of the second charging means to the charging time of the second charging means;and a converging means for increasing said second voltage when said first charging time exceeds said second charging time and for decreasing said second voltage when said second charging time exceeds said first charging time.
Claim 40
Dependent Claim
135 words
The liquid crystal display system claimed in Claim 32, wherein: said display drive means includes a second voltage generator comprising a predetermined voltage source, a counter having a duty cycle blanking count stored therein and a duty cycle blanking means for generating said second voltage by blanking the voltage generated by said predetermined voltage source by a duty cycle ratio corresponding to said duty cycle blanking count; said capacitance ratio selection means being responsive to said duty cycle blanking count for selecting said predetermined ratio value depending upon said duty cycle blanking count; and said converging means comprises means for decrementing said duty cycle blanking count when said first charging time exceeds said second charging time and means for incrementing said duty cycle blanking count when said second charging time exceeds said first charging time.
Claim 41
Dependent Claim
9 words
The liquid crystal display system as claimed in Claim
Claim 42
Dependent Claim
152 words
33, wherein said capacitance ratio selection means comprises: a state counter having a plurality of states, each state corresponding to one of said plurality of predetermined ratio values: a plurality of count sensors, each responsive to said duty cycle blanking count for generating a coincidence signal when said duty cycle blanking count equals a respective predetermined count, and each associated with two states of said state counter corresponding to adjacent temperature ranges: and a state selector means, responsive to said count sensors and said timer means, for placing said state counter in said state associated with a count sensor generating an enable signal corresponding to the lower temperature range when said first charging time exceeds said second charging time for placing said state counter in said state associated with a count sensor generating an enable signal corresponding to the higher temperature range when said second charging time exceeds said first charging time.
Claim 43
Dependent Claim
152 words
33, wherein said capacitance ratio selection means comprises: a state counter having a plurality of states, each state corresponding to one of said plurality of predetermined ratio values: a plurality of count sensors, each responsive to said duty cycle blanking count for generating a coincidence signal when said duty cycle blanking count equals a respective predetermined count, and each associated with two states of said state counter corresponding to adjacent temperature ranges: and a state selector means, responsive to said count sensors and said timer means, for placing said state counter in said state associated with a count sensor generating an enable signal corresponding to the lower temperature range when said first charging time exceeds said second charging time for placing said state counter in said state associated with a count sensor generating an enable signal corresponding to the higher temperature range when said second charging time exceeds said first charging time.
Claim 44
Dependent Claim
104 words
The liquid crystal display system claimed in Claim 31, further comprising: a plurality of liquid crystal display segments; an off voltage generator means for generating an off voltage having a first predetermined ratio to said second voltage; an on voltage generator means for generating an on voltage having a second predetermined ratio to said second voltage, said second predetermined ratio being greater than said first predetermined ratio; and a display actuation means for coupling said on voltage to selected ones of said plurality of display segments for actuation thereof and for coupling said off voltage to the other of said plurality of display segments.
Claim 45
Dependent Claim
142 words
A display drive circuit for use in a liguid crystal display system having first and second display segments, said display drive circuit comprising: a display drive means for coupling said first display segment to a first voltage and for coupling said second display segment to a second voltage; a capacitance ratio selection means, responsive to the temperature of said display segments, for selecting one of a plurality of predetermined ratio values, each ratio value corresponding to one of a plurality of temperature ranges; and a temperature compensation means for determining the ratio of the capacitance of said first display segment when coupled to said first voltage to the capacitance of said second display segment when coupled to said second voltage and for changing said second voltage and for changing said second voltage to converge said ratio to said selected predetermined ratio value.
Claim 46
Dependent Claim
142 words
A display drive circuit for use in a liguid crystal display system having first and second display segments, said display drive circuit comprising: a display drive means for coupling said first display segment to a first voltage and for coupling said second display segment to a second voltage; a capacitance ratio selection means, responsive to the temperature of said display segments, for selecting one of a plurality of predetermined ratio values, each ratio value corresponding to one of a plurality of temperature ranges; and a temperature compensation means for determining the ratio of the capacitance of said first display segment when coupled to said first voltage to the capacitance of said second display segment when coupled to said second voltage and for changing said second voltage and for changing said second voltage to converge said ratio to said selected predetermined ratio value.
Claim 47
Dependent Claim
158 words
The liquid crystal display system claimed in Claim 36, wherein said temperature compensator means comprises: a first charging means for charging said.first display segment to a predetermined voltage at a predetermined first rate after said display drive means has coupled said first display segment to said first voltage; a second charging means for charging said second display segment to a predetermined voltage at a selected one of a plurality of predetermined second rates corresponding to said selected predetermined ratio value after said display drive means has coupled said second display segment to said second voltage; a charging time comparison means for determining the relationship of the first charging time of the second charging means to the charging time of the second charging means; and a converging means for increasing said. second voltage when said first charging time exceeds said second charging time and for decreasing said second voltage when said second charging time exceeds said first charging time.
Claim 48
Dependent Claim
134 words
The liquid crystal display system claimed in Claim 37, wherein: said display drive means includes a second voltage generator comprising a predetermined voltage source, a counter having a duty cycle blanking count therein and a duty cycle blanking means for generating said second voltage by blanking the voltage generated by said predetermined voltage source by a duty cycle ratio corresponding to said duty cycle blanking count; said capacitance ratio selection means being responsive to said duty cycle blanking count for selecting said predetermined ratio value depending upon said duty cycle blanking count; and said converging means comprises means for decrementing said duty cycle blanking count when said first charging time exceeds said second charging time and means for incrementing said duty cycle blanking count when said second charging time exceeds said first charging time.
Claim 49
Dependent Claim
164 words
The liquid crystal display system as claimed in Claim 38, wherein said capacitance ratio selection means comprises: a state counter having a plurality of states, each state corresponding to one of said plurality of predetermined ratio values; a plurality of count sensors, each responsive to said duty cycle blanking count for generating a coincidence signal when said duty cycle blanking count equals a respective predetermined count, and each associated with two states of said state counter corresponding to adjacent temperature ranges; and a state selector means, responsive to said count sensors and said charging time comparison means, for placing said state counter in said state associated with a count sensor generating an enable signal corresponding to the lower temperature range when said first charging time exceeds said second charging time and for placing said state counter in said state associated with a count sensor generating an enable signal corresponding to the higher temperature range when said second charging time exceeds said first charging time.
Claim 50
Dependent Claim
105 words
The liquid crystal display system claimed in Claim 39, further comprising: a plurality of liquid crystal display segments; an off voltage generator means for generating an off voltage having a first predetermined ratio top said second voltage; an on voltage generator means for generating an on voltage having a second predetermined ration to said second voltage, said second predetermined ration being greater than said first predetermined ratio; and a display actuation means for coupling said on voltage to selected ones of said plurality of display segments for actuation thereof and for coupling said off segment voltage to the other os said plurality of display segments.
Claim 51
Dependent Claim
74 words
A data processing system comprising: data processing means for providing data in an encoded format in a first operating mode and in a display format in a second operating mode; and data display means responsive to the operating mode of the data processing means, for receiving the data provided by the data processing means, converting data received in the encoded format to the display format, and displaying the received data in the display format.
Claim 52
Dependent Claim
74 words
A data processing system comprising: data processing means for providing data in an encoded format in a first operating mode and in a display format in a second operating mode; and data display means responsive to the operating mode of the data processing means, for receiving the data provided by the data processing means, converting data received in the encoded format to the display format, and displaying the received data in the display format.
Claim 53
Dependent Claim
59 words
The data processing system of Claim 41 wherein the data display means are for receiving the data provided by the data processing means, storing the received data, converting data received and stored in the encoded format into the display format, storing the converted data in the display format, and displaying the received and stored data in the display format.
Claim 54
Dependent Claim
172 words
The data processing system of Claim 41 wherein the data display means comprises: first storage means for selectively receiving and storing data in the encoded format, and for selectively providing data stored therein in the encoded format; second storage means for selectively receiving and storing data in the display format, and for selectively providing data stored therein in the display format; conversion means for selectively receiving data in the encoded format, converting the received data to the display format, and providing the data in the display format; control means responsive to the operating mode of the data processing means, for selectively enabling the first storage means, the conversion means and the second storage means to receive and store the data provided by the data processing means, convert data received and stored in the encoded format to the display format, store the converted data in the display format, and provide the data in the display format; and display means for displaying the data provided by the second storage means in the display format.
References Cited (Backward Citations)
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