Touch detection device
According to one embodiment, a touch detection device includes a touch panel including a transmitting coil and a receiving coil, the touch panel provided with a display function and a touch detection function, and a differential amplifier including two input terminals connected to first and second terminals of the receiving coil.
1. A touch detection device comprising:
a touch panel comprising a transmitting coil and a receiving coil, the touch panel provided with a display function and a touch detection function;
a differential amplifier comprising two input terminals connected to first and second terminals of the receiving coil;
a comparator configured to detect a phase difference between a drive signal supplied to the transmitting coil and an output signal of the differential amplifier; and
a compensation circuit configured to compensate for a phase delay of the differential amplifier,
wherein the drive signal is input to the comparator via the compensation circuit.
2. The touch detection device of claim 1 , wherein
the differential amplifier comprises a first operational amplifier, a second operational amplifier and a third operational amplifier,
an output terminal of the first operational amplifier is connected to an inverting input terminal of the third operational amplifier,
an output terminal of the second operational amplifier is connected to a non-inverting input terminal of the third operational amplifier,
an inverting input terminal of the first operational amplifier and an inverting input terminal of the second operational amplifier are connected to each other,
the first terminal of the receiving coil is connected to a non-inverting input terminal of the first operational amplifier, and
the second terminal of the receiving coil is connected to a non-inverting input terminal of the second operational amplifier.
3. The touch detection device of claim 2 , wherein
the output terminal of the first operational amplifier is connected to the inverting input terminal of the first operational amplifier via a first resistor,
the output terminal of the second operational amplifier is connected to the inverting input terminal of the second operational amplifier via a second resistor,
a third resistor is connected between the first resistor and the second resistor,
the output terminal of the first operational amplifier is connected to the inverting input terminal of the third operational amplifier via a fourth resistor,
the output terminal of the second operational amplifier is connected to the non-inverting input terminal of the third operational amplifier via a fifth resistor,
an output terminal of the third operational amplifier is connected to the inverting input terminal of the third operational amplifier via a sixth resistor,
the non-inverting input terminal of the third operational amplifier is grounded via a seventh resistor, and
the touch detection device further comprises:
a gain adjustment circuit configured to change a gain of the differential amplifier by changing resistor values of one or more of the first resistor, the second resistor, the third resistor, the fourth resistor, the fifth resistor, the sixth resistor and the seventh resistor.
4. The touch detection device of claim 1 , wherein
the touch panel comprises:
pixels arranged in a two-dimensional array in an X direction and a Y direction;
drive electrodes connected to rows of the pixels arranged in the X direction and extending in the X direction; and
signal lines connected to columns of the pixels in the Y direction and extending in the Y direction,
the transmitting coil comprises the drive electrodes, and
the receiving coil comprises the signal lines.
5. The touch detection device of claim 4 , wherein the touch panel comprises:
a first substrate comprising the pixels;
a second substrate arranged on the first substrate and comprising a color filter; and
a liquid crystal layer arranged between the first substrate and the second substrate,
the drive electrodes are formed on the first substrate, and
the signal lines are formed on the second substrate.
6. The touch detection device of claim 4 , wherein
the touch panel comprises:
a first substrate comprising the pixels;
a second substrate arranged on the first substrate and comprising a color filter; and
a liquid crystal layer arranged between the first substrate and the second substrate,
the signal lines are formed on the first substrate, and
the drive electrodes are formed on the signal lines via an insulating layer.