Touch panel for display device
A touch panel for a display device integrates functionality provided by resistive-type and EM-type touch panels. The touch panel is integrated with the display device and includes a resisitve-type touch panel arranged above the display device and an EM-type touch panel arranged below the display device.
1. A touch panel for a display device, comprising:
a resistive-type touch panel arranged above the display device;
an electromagnetic (EM)-type touch panel arranged below the display device; and
a first driving part to drive the resistive-type touch panel, wherein the first driving part generates voltages corresponding to coordinates of a location of an object contacting the touch panel using potential gradients generated across substrates of the touch panel,
wherein the electromagnetic (EM)-type touch panel includes:
a sensor board including a plurality of antenna coils;
a select circuit for selecting one of the plurality of antenna coils;
a transmitting circuit for successively applying an AC signal to the selected antenna coil selected by the select circuit to generate an electromagnetic field from the selected antenna coil;
a stylus pen generating an induction voltage from the electromagnetic field and discharging the induction voltage to excite the selected antenna coil so that the selected antenna coil generates a received signal;
a receiving circuit amplifying and filtering the received signal and outputting a filtered signal;
a connection switching circuit for alternately connecting the select circuit to the transmitting circuit and the receiving circuit; and
a processing circuit for controlling the select circuit and the connection switching circuit, and detecting a location of a contact point of the stylus pen from the filtered signal,
wherein the transmitting circuit includes:
an oscillator generating a clock pulse;
a frequency divider dividing the clock pulse into first, second and third frequencies;
a first NAND gate for calculating the second and third frequencies;
a second NAND gate for inverting a signal outputted from the first NAND gate;
a driving circuit converting a signal outputted from the second NAND gate to an average signal and transmitting the average signal to the selected antenna coil through the connection switching circuit and the select circuit; and
an EXOR gate calculating the first and second frequencies, wherein the receiving circuit includes:
an amplifier amplifying the received signal from the selected antenna coil and outputting an amplified signal;
a first phase detector receiving the second frequency and the amplified signal from the frequency divider and the amplifier, and generating a first inverted signal;
a second phase detector receiving a signal from the EXOR gate and the amplified signal from the amplifier, and outputting a second inverted signal;
a first low-pass filter converting the first inverted signal to a first average signal and outputting the first average signal to the a processing circuit; and
a second low-pass filter converting the second inverted signal to a second average signal and outputting the second average signal to the processing circuit.
2. The touch panel of claim 1 , wherein the resistive-type touch panel includes:
upper and lower substrates bonded to each other;
transparent electrodes arranged on opposing surfaces of the upper and lower substrates; and
patterned spacers arranged between the upper and lower substrates.
3. The touch panel of claim 2 , wherein the resistive-type touch panel further includes an adhesive material arranged in a dead space region bonding the upper and lower substrates to each other.
4. The touch panel of claim 1 , further comprising a case top securing the display device, the resistive-type touch panel, and the EM-type touch panel together as a single body.
5. A touch panel display device, comprising:
a display device;
a resistive-type touch panel arranged above the display device;
an electromagnetic (EM)-type touch panel arranged below display device;
a case top securing the display device, the resistive-type touch panel, and the EM-type touch panel together as a single body; and
a first driving part to drive the resistive-type touch panel, wherein the first driving part generates voltages corresponding to coordinates of a location of an object contacting the touch panel using potential gradients generated across substrates of the touch panel,
wherein the electromagnetic (EM)-type touch panel includes:
a sensor board including a plurality of antenna coils;
a select circuit for selecting one of the plurality of antenna coils;
a transmitting circuit for successively applying an AC signal to the selected antenna coil selected by the select circuit to generate an electromagnetic field from the selected antenna coil;
a stylus pen generating an induction voltage from the electromagnetic field and discharging the induction voltage to excite the selected antenna coil so that the selected antenna coil generates a received signal;
a receiving circuit amplifying and filtering the received signal and outputting a filtered signal;
a connection switching circuit for alternately connecting the select circuit to the transmitting circuit and the receiving circuit; and
a processing circuit for controlling the select circuit and the connection switching circuit, and detecting a location of a contact point of the stylus pen from the filtered signal,
wherein the transmitting circuit includes:
an oscillator generating a clock pulse;
a frequency divider dividing the clock pulse into first, second and third frequencies;
a first NAND gate for calculating the second and third frequencies;
a second NAND gate for inverting a signal outputted from the first NAND gate;
a driving circuit converting a signal outputted from the second NAND gate to an average signal and transmitting the average signal to the selected antenna coil through the connection switching circuit and the select circuit; and
an EXOR gate calculating the first and second frequencies, wherein the receiving circuit includes:
an amplifier amplifying the received signal from the selected antenna coil and outputting an amplified signal;
a first phase detector receiving the second frequency and the amplified signal from the frequency divider and the amplifier, and generating a first inverted signal;
a second phase detector receiving a signal from the EXOR gate and the amplified signal from the amplifier, and outputting a second inverted signal;
a first low-pass filter converting the first inverted signal to a first average signal and outputting the first average signal to the a processing circuit; and
a second low-pass filter converting the second inverted signal to a second average signal and outputting the second average signal to the processing circuit.