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EP-4432058-B1 - DISPLAY DEVICE

EP4432058B1EP 4432058 B1EP4432058 B1EP 4432058B1EP-4432058-B1

Inventors

  • Konuma, Kengo

Dates

Publication Date
20260506
Application Date
20240308

Claims (6)

  1. A display device including a liquid crystal display, LCD, panel configured such that common electrodes to which a potential based on a ground level is applied, liquid crystal, and pixel electrodes are stacked, and a display driver for driving the pixel electrodes of the LCD panel, the display device comprising: a power source section (1021, 1022) configured to supply a power source to be used by the display driver to drive the pixel electrodes; a capacitor having one end connected to wiring of the power source between the power source section and the display device; and an impedance device disposed between the other end of the capacitor and the ground of the display device, wherein the capacitor and the impedance device have such impedance characteristics that a DC component is blocked and impedance in a predetermined frequency band set as a frequency band in which ground noise is generated is reduced.
  2. The display device according to claim 1, wherein the LCD panel is an in-cell LCD panel, and further including a touch panel controller that is configured to detect a touch by applying an AC signal to the common electrodes of the LCD panel, the display device comprising: a first capacitor (C1); and a second capacitor (C2); wherein each of the first capacitor and the second capacitor is connected at one end to AC signal wiring, which is wiring to which the AC signal is applied from the touch panel controller, and at the other end to power source wiring, which is wiring for the power source between the power source section and the display driver, the impedance device has one end connected to AC signal wiring and the other end connected to the ground of the display device, the AC signal is superimposed on the power source via the first capacitor, and the second capacitor and the impedance device have such impedance characteristics that a DC component is blocked and impedance in a frequency band of the AC signal is increased and impedance in a predetermined frequency band set as a frequency band where ground noise is generated is reduced.
  3. The display device according to claim 1, wherein the LCD panel is an in-cell LCD panel, and further including a touch panel controller that is configured to detect a touch by applying an AC signal to the common electrodes of the LCD panel, wherein the LCD panel includes TFTs having drains connected to the pixel electrodes, sources to which source voltages corresponding to pixel values are applied from the display driver, and gates to which gate voltages are applied by the display driver, the TFTs being controlled to be turned on or off by the gate voltages, the display device includes a first power source section (1021) configured to supply a first power source of a voltage to be used as a gate voltage when the display driver turns on the TFTs connected to the pixel electrodes, a second power source section (1022) configured to supply a second power source which is a power source of a voltage to be used as a gate voltage when the display driver turns off the TFTs connected to the pixel electrodes, a first capacitor (C1), a second capacitor (C2), a third capacitor (C4), and a fourth capacitor (C5), wherein each of the first capacitor and the second capacitor is connected at one end to AC signal wiring, which is wiring to which the AC signal is applied from the touch panel controller, and at the other end to first power source wiring, which is wiring for the first power source between the first power source section and the display driver, each of the third capacitor and the fourth capacitor is connected at one end to the AC signal wiring and at the other end to second power source wiring, which is wiring for the second power source between the second power source section and the display driver, the impedance device has one end connected to AC signal wiring and the other end connected to the ground of the display device, the AC signal is superimposed on the first power source via the first capacitor and the AC signal is superimposed on the second power source via the third capacitor, and the second capacitor, the fourth capacitor, and the impedance device have such impedance characteristics that a DC component is blocked and impedance in a frequency band of the AC signal is increased and impedance in a predetermined frequency band set as a frequency band where ground noise is generated is reduced.
  4. The display device according to Claim 3, comprising: a display panel (103) including the LCD panel, the display driver, and the touch panel controller; a substrate (102) having the first power source section, the second power source section, the first capacitor, the second capacitor, the third capacitor, the fourth capacitor, and the impedance device; and a flexible printed circuit (FPC) (104) configured to connect the display panel and the substrate, wherein a portion, between the display panel and the substrate, of the AC signal wiring, the first power source wiring, and the second power source wiring is formed on the FPC.
  5. The display device according to any one of Claims 1 to 4, wherein the impedance device is a series LC circuit with a coil and a capacitor connected in series.
  6. The display device according to any one of Claims 1 to 5, wherein the display device is mounted on a vehicle, the ground of the display device is connected to a battery of the vehicle through a predetermined ground line and to a vehicle body ground of the vehicle by a conductive body different from the ground line, and the predetermined frequency band includes a resonant frequency of an antenna having a length corresponding to a length of a path between the battery and the vehicle body ground via the ground of the display device.

Description

The present disclosure relates to noise suppression for display devices that use liquid crystal displays (LCDs), such as in-cell touch panel displays. As a display device using an LCD, an in-cell touch panel display has been used that uses a common electrode also as an electrode for touch detection in an LCD which has pixels arranged therein and which has pixel electrodes to which voltages corresponding to pixel values are applied, the common electrode to which a common voltage is applied, and a liquid crystal sandwiched between the pixel electrodes and the common electrode. In such an in-cell touch panel display, a technology for stabilizing a drive signal to be applied to the common electrode by applying an AC drive signal applied to the common electrode for touch detection to signal lines of the pixels during the touch detection, thereby reducing an adverse effect of parasitic capacitance between the common electrode and the signal lines of the pixels has been used (for example, JP 2015-210811 A). A ground of a display device with an LCD may be connected to both a ground line that is connected to a battery and a vehicle body ground. In general, the display device and the battery are located far apart, and a length of the ground line between the display device and the battery is at least 1 m. In this case, a portion forming a path extending from the ground line through the display device to the vehicle body ground functions as an antenna, and in relation to the fact that the ground line has high impedance, noise generated by radio waves, etc. at the antenna propagates to the display device as ground noise carrying a relatively large current. The ground noise propagating to the display device is large at a resonant frequency of the antenna. This ground noise causes malfunction of the display device. US 2017/269779 A1 discloses a capacitive sensing method comprising driving a first excitation signal onto a sensor electrode, and driving a second excitation signal onto the embedded electrodes. It discloses various methods and apparatuses for capacitive touch sensing that eliminates the effect of parasitic capacitance. The various embodiments can be used for LCD touch-display panels employing self-capacitive sensing techniques and mechanisms, and can prevent noise from a relatively noisy local ground of pulse generators and power supplies. US 2013/082977 A1 provides a display, a touch detection unit, a driving method, and an electronic unit which are allowed to reduce probability of malfunction caused by noise. A malfunction may be caused by the fact that a touch signal related to the presence or absence of a touch event is undistinguished from disturbance noise. In the display panel, the frequency of an AC drive signal VcomAC is allowed to be easily changed so that such malfunction is reduced. Accordingly, it is an object of the present invention to suppress malfunction of the display device caused by ground noise. The present invention relates to a display device according to the appended claims. Embodiments are disclosed in the dependent claims. According to an aspect of the present disclosure, a display device having a liquid crystal display (LCD) panel configured such that common electrodes to which a potential based on a ground level is applied, liquid crystal, and pixel electrodes are stacked, and a display driver for driving the pixel electrodes of the LCD panel includes a power source section configured to supply a power source to be used by the display driver to drive the pixel electrodes, a capacitor having one end connected to wiring of the power source between the power source section and the display device, and an impedance device disposed between the other end of the capacitor and the ground of the display device. Here, the capacitor and the impedance device have such impedance characteristics that a DC component is blocked and impedance in a predetermined frequency band set as a frequency band in which ground noise is generated is reduced. According to another aspect of the present disclosure, a display device having an in-cell LCD panel configured such that common electrodes to which a potential based on a ground level is applied, liquid crystal, and pixel electrodes are stacked, a display driver that drives pixel electrodes of the LCD panel, and a touch panel controller that detects a touch by applying an AC signal to the common electrodes of the LCD panel includes a power source section configured to supply a power source to be used by the display driver to drive the pixel electrodes, a first capacitor, a second capacitor, and an impedance device. Here, each of the first capacitor and the second capacitor is connected at one end to AC signal wiring, which is wiring to which the AC signal is applied from the touch panel controller, and at the other end to power source wiring, which is wiring for the power source between the power source section and the display driver. Furthermore, the impedan