Touch pad and position detecting circuit and method thereof
First Claim
1. A position detecting circuit for a touch pad, said touch pad including a sensing pad and a sensing pen, the position detecting circuit comprising:
- a waveform generator, for generating an input signal, wherein said input signal is capable of gradually moving a position of a zero voltage on said sensing pad in a predetermined direction;
a filter, for receiving a sensing signal sensed by said sensing pen, and filtering and outputting said sensing signal;
an amplifier, coupled to said filter, for receiving and amplifying said filtered sensing signal;
an envelope detector, coupled to said amplifier, for detecting said filtered-amplified sensing signal and generating an envelope signal;
a zero voltage detector, coupled to said envelope detector, for receiving said envelope signal and generating an output signal, wherein said output signal is capable of determining as to when a zero voltage occurs; and
a controller, coupled to said waveform generator and said zero voltage detector, for controlling said waveform generator to generate said input signal and determining a position of said sensing pen on said sensing pad responsive to said output signal from said zero voltage detector,wherein said position of said zero voltage moves back and forth in said predetermined direction.
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Abstract
A touch pad and a position detecting circuit and method thereof are provided. The touch pad uses a waveform generator to generate an input signal; the input signal is capable of gradually moving a position of a zero voltage on the sensing pad in a predetermined direction. The touch pad also uses the zero voltage detector to detect when a zero voltage of the sensing signal of the sensing pen occurs so as to determine the position of the sensing pen on the sensing pad. Hence, the analog-to-digital converter is not required. Therefore, the resolution can be easily expanded, and the cost, the preciseness, and the specification can be easily controlled.
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Citations
10 Claims
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1. A position detecting circuit for a touch pad, said touch pad including a sensing pad and a sensing pen, the position detecting circuit comprising:
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a waveform generator, for generating an input signal, wherein said input signal is capable of gradually moving a position of a zero voltage on said sensing pad in a predetermined direction; a filter, for receiving a sensing signal sensed by said sensing pen, and filtering and outputting said sensing signal; an amplifier, coupled to said filter, for receiving and amplifying said filtered sensing signal; an envelope detector, coupled to said amplifier, for detecting said filtered-amplified sensing signal and generating an envelope signal; a zero voltage detector, coupled to said envelope detector, for receiving said envelope signal and generating an output signal, wherein said output signal is capable of determining as to when a zero voltage occurs; and a controller, coupled to said waveform generator and said zero voltage detector, for controlling said waveform generator to generate said input signal and determining a position of said sensing pen on said sensing pad responsive to said output signal from said zero voltage detector, wherein said position of said zero voltage moves back and forth in said predetermined direction. - View Dependent Claims (2, 3, 4)
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5. A position detecting method for a touch pad, said touch pad including a sensing pad and a sensing pen, the method comprising:
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inputting an input signal, wherein said input signal is capable of gradually moving a position of a zero voltage on said sensing pad in a predetermined direction; and determining a position of said sensing pen on said sensing pad based on a timing when a zero voltage of a sensing signal of said sensing pen occurs, wherein said position of said zero voltage moves back and forth in said predeterrnined direction. - View Dependent Claims (6)
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7. A touch pad, comprising:
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a sensing pad; a sensing pen; a waveform generator, for generating an input signal, wherein said input signal is capable of moving a position of a zero voltage on said sensing pad in a predetermined direction gradually; a filter, for receiving a sensing signal sensed by said sensing pen, filtering and outputting said sensing signal; an amplifier, coupled to said filter, for receiving and amplifying said filtered sensing signal; an envelope detector, coupled to said amplifier, for detecting said filtered-amplified sensing signal and generating an envelope signal; a zero voltage detector, coupled to said envelope detector, for receiving said envelope signal and generating an output signal, wherein said output signal is capable of determining as to when a zero voltage occurs; and a controller, coupled to said waveform generator and said zero voltage detector, for controlling said waveform generator to generate said input signal and determining a position of said sensing pen on said sensing pad responsive to said output signal from said zero voltage detector, wherein said position of said zero voltage moves back and forth in said predetermined direction. - View Dependent Claims (8, 9, 10)
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Specification