Liquid crystal display apparatus with touch panel

• US 6,236,386 B1
• Filed: 12/21/1998
• Issued: 05/22/2001
• Est. Priority Date: 12/22/1997
• Status: Expired due to Term

• Current Assignee: Lenovo Innovations Ltd Hong Kong (Lenovo Group Ltd.)
• Original Assignee: NEC Corporation
• Inventors: Watanabe, Mitsuhiro
• Primary Examiner(s): Hjerpe, Richard
• Assistant Examiner(s): Zamani, Ali A.
• Application Number:
  US09/217,343
• Time in Patent Office: 883 Days
• Field of Search: 345/99, 345/100, 345/179, 345/104, 345/98, 345/173
• US Class Current: 345/98
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/04182 Filtering of noise external to the device and not generated by digitiser components
• CPC Class Codes: G06F 3/045 using resistive elements, e.g. a single continuous surface or two parallel surfaces put in contact
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers

Abstract

In a liquid crystal display apparatus, sampling of an A-D converter for the purpose of capturing data from a touch panel is performed at a rate that is unrelated to the AC signal applied to the LCD, and data from the touch panel is captured in a regular manner in accordance with the sampling rate of the A-D converter. An added circuit detects the transformation points of the LCD AC signal and, based on a transformation point detection signal that is output by this circuit, data of the touch panel data sampled by the A-D converter that is affected by LCD noise is discarded, so that only data not affected by LCD noise is sent to a main memory.

Claims

1. A liquid crystal display apparatus, comprising:

an LCD as a display means;

an LCD control unit for controlling a display of said LCD;

a main controller for displaying required graphic data and character data on said LCD via the LCD control unit;

an analog-type touch panel as an input means;

an A-D converter that converts touch panel analog data to digital data;

a touch panel interface for establishing an interface between said main controller and said A-D converter, and in said display apparatus, information for a position on a screen being determined from said analog data of said touch panel, and said position information being displayed on said LCD, or used to detect a data input position corresponding to a position on said LCD screen, and wherein said display apparatus is further provided with a data-cancellation means for inhibiting the capture of digital data from said A-D converter at the occurrence of noise that is generated as a result of a control signal that is supplied to said LCD from said LCD control unit;

wherein said data-cancellation means is located separately from the main controller and comprises;

a transformation point detection unit for detecting a transformation point of said AC signal of said control signals and outputting a transformation point detection signal;

a data capturing start signal generating unit for generating a data capturing start signal that establishes the timing of the capture of digital data from said A-D converter; and

a captured data discarding unit that, upon receipt of said transformation point detection signal and said data capturing start signal, if at least a part of each of said transformation point signal and said data capturing start signal overlap, generates a data discard signal.

2. A liquid crystal display apparatus according to claim 1, wherein said data-cancellation means is provided in said touch panel interface, and wherein said touch panel interface discards digital data that was captured from said A-D converter at a time when said data discard signal is generated.

3. A liquid crystal display apparatus according to claim 2, wherein said transformation point detection unit comprises:

a first clock generation circuit for the purpose of generating a first clock that is synchronized to said AC signal;

a D-type flip-flop for the purpose of delaying said AC signal by one clock, using said first clock; and

an exclusive-OR circuit which takes the exclusive-OR of said AC signal and said AC signal delayed by one clock and outputting said exclusive-OR as a transformation point detection signal.

4. A liquid crystal display apparatus according to claim 2, wherein said captured data discarding unit comprises:

a second clock generation circuit for the purpose of generating a second clock;

an inverter circuit for the purpose of inverting said second clock;

a first D-type flip-flop for the purpose of receiving said second clock at a clock terminal and receiving said AC signal at a D input terminal;

a second D-type flip-flop for the purpose of receiving said second clock at a clock terminal and receiving a Q output of said first D-type flip-flop at a D input terminal; and

a logical AND circuit that takes the AND of said data capturing start signal and a Q output of said second D-type flip-flop and outputs this as a data discard signal.

5. A liquid crystal display apparatus according to claim 1, wherein said LCD has a function of generating an AC signal by a frame signal of said control signals, and wherein said data-cancellation means comprises:

a transformation point detection unit for the purpose of detecting a transformation point of said frame signal and outputting a transformation point detection signal;

a data capturing start signal generation units that generates a data capturing start signal that establishes the timing of the capture of digital data from said A-D converter; and

a captured data discarding unit that, upon receipt of said transformation point detection signal and said data capturing start signal, if at least a part of said each of signals is temporally overlap to each other, generates a data discard signal.

6. A liquid crystal display apparatus, comprising:

an LCD as a display means;

an LCD control unit for controlling a display of said LCD;

a main controller for displaying required graphic data and character data on said LCD via the LCD control unit;

an analog-type touch panel as an input means;

a touch panel interface, which internally includes an A-D converter that converts touch panel analog data to digital data, for establishing an interface between said main controller and said touch panel, and in said display apparatus, information for a position on a screen being determined from said analog data of said touch panel, and said position information being displayed on said LCD, or used to establish a correspondence to an input position on said LCD screen;

a data-cancellation means for inhibiting the capture of digital data from said A-D converter at the occurrence of noise that is generated as a result of a control signal that is supplied to said LCD from said LCD control unit;

wherein said data-cancellation means is located separately from the main controller and comprises;

a transformation point detection unit for detecting a transformation point of said AC signal of said control signals and outputting a transformation point detection signal;

a data capturing start signal generation unit for generating a data capturing start signal that establishes the timing of the capture of digital data from said A-D converter; and

a captured data discarding unit that. upon receipt of said transformation point detection signal and said data capturing start signal, if at least a part of each of said transformation point detection signal and said data capturing start signal overlap, generates a data discard signal.

7. A liquid crystal display apparatus according to claim 6, wherein said data-cancellation means is provided in said touch panel interface, and wherein said touch panel interface discards digital data that was captured from said A-D converter at a time when said data discard signal is generated.

8. A liquid crystal display apparatus according to claim 7, wherein said transformation point detection unit comprises:

a first clock generation circuit for the purpose of generating a first clock that is synchronized to said AC signal;

a D-type flip-flop for the purpose of delaying said AC signal by one clock, using said first clock; and

an exclusive-OR circuit which takes the exclusive-OR of said AC signal and said AC signal delayed by one clock and outputting said exclusive-OR as a transformation point detection signal.

9. A liquid crystal display apparatus according to claim 7, wherein said captured data discarding unit comprises:

a second clock generation circuit for the purpose of generating a second clock;

an inverter circuit for the purpose of inverting said second clock;

a first D-type flip-flop for the purpose of receiving said second clock at a clock terminal and receiving said AC signal at a D input terminal;

a second D-type flip-flop for the purpose of receiving said second clock at a clock terminal and receiving a Q output of said first D-type flip-flop at a D input terminal; and

a logical AND circuit that takes the AND of said data capturing start signal and a Q output of said second D-type flip-flop and outputs this as a data discard signal.

10. A liquid crystal display apparatus according to claim 6, wherein said LCD has a function of generating an AC signal by means of a frame signal of said control signals, and wherein said data-cancellation means comprises:

a transformation point detection unit for the purpose of detecting a transformation point of said frame signal and outputting a transformation point detection signal;

a data capturing start signal generation units that generates a data capturing start signal that establishes the timing of the capture of digital data from said A-D converter; and

a captured data discarding unit that, upon receipt of said transformation point detection signal and said data capturing start signal, if at least a part of said each of signals is temporally overlap to each other, generates a data discard signal.