TWI397049B - Transreflective display apparatus and driving method thereof - Google Patents

Description

Penetrating reflection type display device and driving method thereof

The present invention relates to a display device, and more particularly to a transreflective display device and a method of driving the same.

Today's electronic devices, such as cell phones, personal digital assistants (PDAs), and notebook computers, typically have display devices. These display devices need to be designed to be thin and light to save the size and cost of the electronic device. In response to demand, flat panel displays (FPDs) have gradually replaced the cathode ray tube displays.

The flat panel display panel is divided into a transmissive display panel, a reflective display panel, and a transflective display panel. The transmissive display panel uses a backlight module placed behind it as a light source. The reflective display panel uses ambient light or a light source located in front of the panel. The transflective display panel can use a backlight module and/or ambient light as a light source.

1 is a schematic view of a transflective display panel. Each pixel in the transflective display panel includes a reflective area formed by the reflective material and a transparent area formed by the transparent material. When the ambient light intensity around the display panel is sufficiently strong (eg, above a threshold), the display panel is in a reflective mode that uses ambient light as the light source and emits light from the reflective area. When the intensity of the ambient light is insufficient, the display panel is in a penetrating mode, which uses the backlight module as a light source and emits light from the penetrating region.

However, when the transflective display panel is in the penetrating mode, the backlight module will begin to provide backlighting, but ambient light may be present and reflected from the reflective area. Therefore, some gray scales representing darker pixels cannot be displayed distinctively. 2 is a voltage-to-transparency (V-T) curve of a transflective display panel. The dotted line L' shows the V-T curve of distortion compared to the original solid line L without distortion. That is, when the voltage V0 is applied to the pixel, the transmittance T0' of the distortion V-T curve L' is actually displayed due to the reflected ambient light, instead of the expected transmittance T0 of the original V-T curve L. Therefore, the low gray level corresponding to the transmittance T0' or less cannot exhibit the expected darkness distinguishably.

Therefore, it is necessary to design an appropriate driving method to improve the above problems.

The present invention provides a driving method of a transflective display device having a dual mode display panel. With this driving method, an image can be normally displayed when the display device is in the reflective mode and the transmissive mode, and the display quality of the display device is improved. In addition, the present invention also provides a transflective display device which also has the above advantages.

The invention provides a driving method of a transflective display device. In the driving method, the ambient light intensity of the display device is detected to determine the display mode of the display device. If the ambient light intensity is greater than the predetermined value, the display mode is in the reflective mode, otherwise the display mode is in the through mode. Then, according to the display mode and the ambient light intensity, a plurality of voltages to one of a voltage-to-transparency (V-T) can be selected to drive the display device.

In an embodiment of the above driving method, the V-T curve includes a through mode V-T curve and a reflective mode V-T curve. If the display mode is the penetration mode and there is some ambient light that affects the display quality (or the ambient light intensity is greater than the low threshold), the penetration mode V-T curve is selected.

The present invention provides a transflective display device. The display device comprises a display panel, an ambient light detector, a backlight module, a timing controller and a gamma voltage generator. A display panel with dual display mode is used to display images. The ambient light detector detects the ambient light intensity of the display device and determines the display mode of the display device according to the ambient light intensity, wherein the display mode is a through mode or a reflective mode. When the display mode is the penetrating mode, the backlight module provides backlighting. The timing controller selects multiple voltages to the transmittance curve according to the display mode and the ambient light intensity. Thereafter, the timing controller controls the gamma voltage generator to generate a plurality of gamma voltages according to the selected V-T curve.

In an embodiment of the above display device, the ambient light detector comprises a light sensor and a light controller. The light sensor detects the ambient light intensity of the display device to output an electronic signal. The light controller converts the electronic signal into a digital form detection signal, so that the ambient light controller can determine the display mode according to the detection signal.

The driving method and the transflective display device of the present invention can select an appropriate voltage to transmittance (V-T) curve to drive the pixels on the display panel according to the ambient light intensity and the display mode. When the display device is in the penetrating mode, pixels with lower gray levels may not be distinguishably displayed due to the presence of ambient light. Therefore, considering the influence of ambient light, V-T curves of different display modes are designed, and even some V-T curves of the penetration mode can be designed according to different ambient light intensities. Therefore, referring to a suitable voltage to transmittance (V-T) curve can improve the display quality of the display device.

The above description and the following detailed description are to be considered as illustrative of the invention

The embodiments of the present invention are described in detail below with reference to the accompanying drawings, in which FIG.

In the embodiment of the invention, the transflective display device comprises a display panel and a backlight module as a light source, wherein the backlight module can emit light to the display panel. 3A is a diagram showing two voltage-to-transparency (V-T) curves VT1 and VT2 applied to a display device according to an embodiment of the present invention. The display device provides V-T curves VT1 and VT2 for two different display modes. Each VT curve is determined by a gamma voltage group, such as gamma voltage V1~Vn in the first VT curve VT1, and gamma voltage V1'~Vn' in the second VT curve VT2, the gamma voltage group A digital to analog converter is provided to the source driver.

In order to distinguish the lower gray scale, one or more gamma voltages corresponding to the lower gray scales in the first V-T curve VT1 are different from the gamma voltages corresponding to the same gray scales in the second V-T curve VT2. In Fig. 3A, the gamma voltage Vn corresponding to the lowest gray level in the first V-T curve VT1 is different from the gamma voltage Vn' corresponding to the lowest gray level in the second V-T curve VT2. In other words, in order to display the lowest gray scale, the gamma voltage Vn' supplied with reference to the second V-T curve VT2 is larger than the gamma voltage Vn supplied from the reference first V-T curve VT1. It is worth mentioning that in other embodiments, the digital to analog converter can interpolate the received gamma voltages V1, V2, ..., and Vn/Vn' to generate more additional gamma voltages. This can cause the display of the lower gray level between the gamma voltages V(n-1) to Vn to be different from the lower gray level between the gamma voltages V(n-1) to Vn'.

For example, a resistor string is utilized to generate a gamma voltage. As shown in FIG. 3A, one end of the resistor string is coupled to the reference voltage Vref, and the other end of the resistor string is coupled to the ground voltage GND. According to the partial pressure theorem, the resistor string can output several analog gamma voltages to drive the pixels on the display panel. Each gamma voltage drives the pixels, so that the pixels exhibit corresponding transmittance on the display panel. The first VT curve VT1 is determined by the first group of gamma voltages V1~Vn, and the second VT curve VT2 is determined by the second group of gamma voltages V1'~Vn', wherein the VT curves VT1 and VT2 In the middle, the same reference numerals added by the symbol "V" correspond to the same gray scale, for example, V1 and V1', V2 and V2', or Vn and Vn'. In this embodiment, although the gamma voltage corresponding to only the lowest gray scale (which represents the darkest pixel) between the two VT curves VT1 and VT2 is different, in other embodiments, the two VT curves VT1 There may be more than one gamma voltage between VT2 and VT2.

In an embodiment of the invention, the display device selects one of the V-T curves depending on the display mode and the intensity of the ambient light. 3B is a flow chart of a method of selecting a V-T curve in accordance with an embodiment of the present invention. First, the display mode can be determined by detecting the ambient light intensity (step 301). When the ambient light intensity is higher than the predetermined value, the display mode is set to the reflective mode, otherwise the display mode is set to the through mode. In the reflective mode, the backlight module of the display device is turned off, and the digital to analog converter of the display device uses the first V-T curve to generate the appropriate gamma voltage (step 303). In the penetration mode, the backlight module of the display device is turned on.

Next, it is detected whether part of the ambient light is still present (step 305). If some ambient light still exists, this ambient light may cause dark pixels with lower gray levels to be indistinguishable when displayed. Therefore, the display device will employ the second V-T curve VT2 (step 307), otherwise the first V-T curve VT1 will be employed (step 303). In the embodiment of the present invention, the gamma voltage provided by the second VT curve VT2 can drive the pixels, so that the pixels exhibit a transmittance corresponding to the critical transmittance T0', and the gamma voltage corresponds to the transmittance. The luminosity is different from each other. In the case where a partial ambient light penetration mode is present, the second V-T curve VT2 is applied to differentially display the lower gray scale. In other embodiments, step 305 is optional and the penetration mode may use the second V-T curve regardless of ambient light. Here, part of the ambient light can be defined as ambient light when the ambient light intensity is greater than the low threshold.

As described above, although the above embodiment provides two VT curves VT1 and VT2 to improve the display quality of the display device in different display modes, when the display device is in the penetrating mode, the intensity of the ambient light can be considered, and the design can also be designed. Multiple VT curves. In other words, when the display device is set to the penetration mode, the critical transmittance T0' changes with the ambient light intensity, resulting in a gamma voltage (which is lower than the driving pixel at the critical transmittance T0'). The pixels driven by the horse voltage are not clearly distinguishable. The more ambient light, the higher the critical transmittance T0' and the more low gray levels are not clearly displayed. Therefore, more appropriate V-T curves need to be designed.

4 is a schematic diagram of a plurality of V-T curves according to an embodiment of the present invention. Referring to FIG. 4, a plurality of V-T curves can be provided via the resistor string shown in FIG. 3A or the programmable gamma voltage generator 402 shown in FIG. Three V-T curves VT1, VT2, and VT3 are illustrated in FIG. 4, but more V-T curves may be used, and the present invention is not limited thereto. The V-T curve VT3 is determined by the gamma voltages V1" to Vn". Compared with the V-T curve VT2, the gamma voltages V(n-1)" and Vn" corresponding to the gray scale are different from the gamma voltages V(n-1)' and Vn' corresponding to the same gray scale. Similarly, the display device determines which of the V-T curves is used to display the image depending on the display mode and/or ambient light intensity. The programmable gamma voltage generator 402 is controlled by a timing controller 401 of the display device that generates a gamma voltage in accordance with the selected V-T curve.

FIG. 5 is a schematic diagram of a transflective display device according to an embodiment of the present invention. The display device includes a display panel 501, a backlight module, an ambient light detector, a timing controller 401, and a programmable gamma voltage generator 402. The ambient light detector includes a light sensor 510 and a light controller 520. The photo sensor 510 detects ambient light to output a detection current I to the light controller 520. Light controller 520 includes a current to voltage converter 502 and an analog to digital converter 503. The light controller 520 converts the detection current I into a detection signal and outputs the detection signal to the timing controller 401. Thereafter, the ambient light detector can determine whether the display mode of the display device is the penetration mode or the reflection mode by the ambient light intensity. When the display mode is the penetration mode, the backlight module provides backlight to the display panel, otherwise the backlight module is turned off. The timing controller 401 selects one of the V-T curves depending on the display mode and/or the intensity of the ambient light. The timing controller 401 receives the ambient light intensity and accordingly controls the programmable gamma voltage generator 402 to generate a set of gamma voltages corresponding to the selected V-T curve. In another embodiment, the light controller 520 and the timing controller 401 can be integrated into an integrated circuit (IC).

In summary, the transflective display device can determine the display mode as the penetration mode or the reflection mode according to the ambient light intensity detected by the ambient light controller. When the display device is in the penetrating mode, the dark pixels with lower gray levels may not be displayed distinctively, so in the above embodiment, multiple VT curves of different display modes are provided, and according to the display mode and the ambient light intensity And select the appropriate VT curve to drive the display panel. Referring to the VT curve of the penetration mode, the gamma voltage provided by the VT curve of the penetration mode can drive the pixel to a transmittance higher than the critical transmittance, the gamma voltage is related to the ambient light intensity, and the gamma voltage The corresponding transmittances have little difference from each other. Therefore, darker pixels can be displayed distinctively and the display quality is improved.

Various modifications and variations of the structure of the present invention are possible without departing from the spirit and scope of the invention. In view of the above, it is intended that the present invention covers the modifications and variations of the present invention.

I. . . Detecting current

V0. . . Voltage

T0. . . Transmittance

L, L', VT1, VT2. . . curve

T0’. . . Critical transmittance

Vref. . . Reference voltage

GND. . . Ground voltage

V1, V1', V2, V2', V(n-1), V(n-1)', V(n-1)", Vn, Vn', Vn". . . Gamma voltage

401. . . Timing controller

402. . . Programmable gamma voltage generator

501. . . Display panel

502. . . Current to voltage converter

503. . . Analog to digital converter

510. . . Light sensor

520. . . Light controller

301, 303, 305, 307. . . Steps of the driving method of an embodiment of the present invention

1 is a schematic view of a transflective display panel.

Figure 2 is a voltage to transmittance curve of a transflective display panel.

3A is a graph showing two voltage to transmittance curves applied to a display device in accordance with an embodiment of the present invention.

3B is a flow chart of a method of selecting a V-T curve in accordance with an embodiment of the present invention.

4 is a schematic diagram of a plurality of V-T curves according to an embodiment of the present invention.

FIG. 5 is a schematic diagram of a transflective display device according to an embodiment of the present invention.

301, 303, 305, 307. . . Steps of the driving method of an embodiment of the present invention

Claims (14)

A driving method for a transflective display device includes: providing a plurality of voltage-to-transparency (VT) curves, including a preset VT curve; and detecting an ambient light intensity of the display device; Determining a display mode according to the ambient light intensity, wherein the display mode is a penetration mode or a reflection mode; when the display mode is the reflection mode, selecting the preset VT curve to drive the display device; and when the When the display module is in the penetration mode and the ambient light intensity is higher than a threshold, another VT curve other than the preset VT curve is selected to drive the display device. The driving method of claim 1, wherein the V-T curve comprises a reflection mode V-T curve and a penetration mode V-T curve. The driving method of claim 2, wherein in the step of selecting one of the V-T curves, if the display mode is the penetration mode and partial ambient light is present, the penetration mode V-T curve is selected. The driving method of claim 2, wherein in the step of selecting one of the VT curves, if the display mode is the penetration mode and the ambient light intensity is greater than a low threshold, then the wearing is selected. Through mode VT curve. The driving method of claim 2, wherein a gamma voltage corresponding to a low gray level in the penetration mode V-T curve is greater than a gamma voltage corresponding to the low gray level in the reflection mode V-T curve. The driving method of claim 1, wherein each of the V-T curves is generated by a gamma voltage group including a plurality of gamma voltages. The driving method of claim 6, wherein the gamma voltage group is generated by a resistor string. The driving method of claim 6, wherein the gamma voltage group is generated by a programmable gamma voltage generator. A transflective display device includes: a display panel for displaying an image; an ambient light detector coupled to the display panel to detect an ambient light intensity of the display device, and according to the ambient light intensity Determining a display mode of the display device, wherein the display mode is a penetration mode or a reflection mode; a backlight module, when the display mode is the penetration mode, providing a backlight; a timing controller, coupled Connected to the ambient light detector, when the display mode is the reflective mode, the timing controller selects a plurality of voltages to a preset VT curve of the transmittance (VT) curve, when the display mode is the penetration mode And when the ambient light intensity is higher than a threshold, the timing controller selects another VT curve other than the preset VT curve; A gamma voltage generator is coupled to the timing controller and controlled by the timing controller to generate a plurality of gamma voltages according to the selected V-T curve. The transflective display device of claim 9, wherein the ambient light detector comprises: a photo sensor that detects the ambient light intensity of the display device to output an electronic signal; and The light controller is coupled to the light sensor, receives the electronic signal, and converts the electronic signal into a detection signal having a digital form, wherein the ambient light controller determines the display mode according to the detection signal. The transflective display device of claim 9, wherein the V-T curves comprise a reflection mode V-T curve and a penetration mode V-T curve. The transflective display device of claim 11, wherein the timing controller selects the penetration mode V-T curve if the display mode is the penetration mode and partial ambient light is present. The transflective display device of claim 11, wherein if the display mode is the penetration mode and the ambient light intensity is greater than a low threshold, the timing controller selects the penetration mode VT curve. . The transflective display device of claim 11, wherein a gamma voltage corresponding to a low gray level in the penetration mode VT curve is greater than a gamma corresponding to the low gray level in the reflection mode VT curve. Horse voltage.