Bistable display device and driving circuit

The disclosure provides a bistable display device and a driving circuit. The bistable display device includes a display panel and the above-described driving circuit, wherein the driving circuit includes a source driver, a first image buffer, a second image buffer, and a timing controller. The source driver is coupled to the display panel to drive the display panel according to a pixel signal. The timing controller is coupled to the first image buffer, the second image buffer, and the source driver. The timing controller alternately selects a first image signal temporarily stored in the first image buffer and a second image signal temporarily stored in the second image buffer as a current image signal and a previous image signal. The timing controller performs a look-up mechanism based on the current image signal and the previous image signal to generate the pixel signal.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan application serial no. 108122109, filed on Jun. 25, 2019. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND

1. Technical Field

The disclosure generally relates to a display technology, in particular, to a bistable display device and a driving circuit.

2. Description of Related Art

In recent years, with the rapid development of display technologies, many electronic products in the daily life have been equipped with display devices. With the popularization of portable electronic products, a bistable display device has gradually gained market attention since it can keep an image without continuous power supply and has the advantages of light weight, thinness, durability, low power consumption and the like.

However, the bistable display device in the prior art needs to compare a gray-scale change between a current image and a previous image to select corresponding driving data during image updating. The existing bistable display device may copy pre-loaded pixel data to a specific buffer and allow a timing controller to read pixel data of the current image and the previous image from the specific buffer according to a fixed reading path. If the size of the display device is larger, the size of the pixel data will be larger. This data copying process may cause a display image updating delay, which makes the bistable display device spend relatively long time on page change, thus affecting the reading experience of a user. Therefore, there is a real need to provide a bistable display device with higher page change speed.

SUMMARY

Accordingly, the disclosure provides a bistable display device and a driving circuit, so as to greatly increase the image updating speed of the bistable display device.

The disclosure provides a bistable display device, including a display panel, a source driver, a first image buffer, a second image buffer and a timing controller. The source driver is coupled to the display panel to drive the display panel according to a pixel signal. The timing controller is coupled to the first image buffer, the second image buffer and the source driver. The timing controller alternately selects a first image signal temporarily stored in the first image buffer and a second image signal temporarily stored in the second image buffer as a current image signal and a previous image signal and performs a look-up mechanism according to the current image signal and the previous image signal to generate the pixel signal.

The disclosure provides a bistable display device, including a display panel, a source driver, a display image buffer, a first image buffer, a second image buffer and a timing controller. The source driver is coupled to the display panel to drive the display panel according to a pixel signal. The display image buffer is configured to temporarily store a previous image signal. The timing controller is coupled to the source driver, the first image buffer, the second image buffer and the display image buffer. A current image signal is temporarily stored in one of the first image buffer and the second image buffer in turn, and the timing controller reads the current image signal from the first image buffer or the second image buffer to perform a look-up mechanism according to the current image signal and the previous image signal to generate the pixel signal.

The disclosure provides a driving circuit, configured to drive a display panel, and including a source driver, a first image buffer, a second image buffer and a timing controller. The source driver is coupled to the display panel to drive the display panel according to a pixel signal. The timing controller is coupled to the first image buffer, the second image buffer and the source driver. The timing controller alternately selects a first image signal temporarily stored in the first image buffer and a second image signal temporarily stored in the second image buffer as a current image signal and a previous image signal, and performs a look-up mechanism according to the current image signal and the previous image signal to generate the pixel signal.

The disclosure provides a driving circuit, configured to drive a display panel, and including a source driver, a display image buffer, a first image buffer, a second image buffer and a timing controller. The source driver is coupled to the display panel to drive the display panel according to a pixel signal. The display image buffer is configured to temporarily store a previous image signal. The timing controller is coupled to the source driver, the first image buffer, the second image buffer and the display image buffer. A current image signal is temporarily stored in one of the first image buffer and the second image buffer in turn, and the timing controller reads the current image signal from the first image buffer or the second image buffer to perform a look-up mechanism according to the current image signal and the previous image signal to generate the pixel signal.

Based on the above, the bistable display device and the driving circuit of the embodiments of the disclosure do not need to copy the image signals temporarily pre-stored in other buffers to another buffer configured to output the current image signal, so that the disclosure can omit the time-consuming image signal copying action, especially when a display region is larger, the delay caused by the image signal copying action is more obvious. After the image buffer of the disclosure receives the current image signal, the timing controller can directly read the current image signal from the image buffer, and further can increase the display image updating speed by reading the data of different image buffers in turn. Therefore, according to the bistable display device and the driving circuit of the embodiments of the disclosure, the display image updating delay may be reduced, and the image updating speed of the bistable display device may be greatly increased.

In order to make the aforementioned and other objectives and advantages of the disclosure comprehensible, embodiments accompanied with figures are described in detail below.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1is a structural diagram of a bistable display device according to an embodiment of the disclosure. Referring toFIG. 1, a bistable display device100includes a display panel101and a driving circuit102. The driving circuit102is configured to drive the display panel101to display images to a user for watching. The display panel101includes a plurality of scanning lines SL, a plurality of data lines DL and a plurality of pixels P (FIG. 1only shows one scanning line SL, one data line DL and one pixel P as a representative). These pixels P are arrayed and respectively coupled to the scanning lines SL and the data lines DL. In the following descriptions, the display panel101takes an e-paper display (EPD) as an embodiment, but not limited thereto. The display panel101also may be other types of bistable display panels, such as an electronic ink (E-ink) display panel, an electrowetting display (EWD) panel, a quick response-liquid powder display (QR-LPD) panel or a cholesteric liquid crystal display (ChLCD) panel.

The driving circuit102at least includes a source driver110, a timing controller (T-con)120and a buffer apparatus130. The timing controller120is coupled to the source driver110and the buffer apparatus130. The buffer apparatus130at least includes two buffers, such as a first image buffer IB1and a second image buffer IB2inFIG. 1, but the disclosure does not limit the number of buffers.

The first image buffer IB1and the second image buffer IB2are configured to respectively temporarily store image signals of different timings, such as an image signal (hereinafter referred to as the previous image signal) currently displayed by the display panel101and an image signal (hereinafter referred to as the current image signal) to be displayed at present by the display panel101. The timing controller120is coupled to the first image buffer IB1and the second image buffer IB2. The timing controller120alternately selects a first image signal temporarily stored in the first image buffer IB1and a second image signal temporarily stored in the second image buffer IB2as the current image signal and the previous image signal, and performs a look-up mechanism according to the current image signal and the previous image signal to generate a pixel signal PS. The pixel signal PS may be transmitted to the source driver110.

In the present embodiment, the timing controller120may have a built-in look-up table LUT to perform the look-up mechanism. The look-up table LUT records driving waveforms required for gray-scale conversion of each pixel P. However, in other embodiments, the timing controller120also may perform the look-up mechanism through a look-up table stored in an external memory (not shown).

It should be further noted that the timing controller120reads the current image signal from the first image buffer IB1and the second image buffer IB2in turn, that is, the reading path for the current image signal or the previous image signal of the present embodiment is not specified.

In addition, the driving circuit102further includes a gate driver140and a common electrode driver150. The timing controller120is also coupled to the gate driver140and the common electrode driver150. The gate driver140generates a gate signal GS according to a scanning enable signal SS provided by the timing controller120, thereby turning on each column of pixels in the display panel101one by one. The common electrode driver150generates a plurality of common voltages Vcom to a common electrode of the display panel101according to a reference signal RS provided by the timing controller120. The source driver110generates a display voltage signal DS according to the pixel signal PS provided by the timing controller120, thereby driving each pixel P to display an image according to a voltage difference between the corresponding display voltage signal DS and each of the common voltages Vcom.

Implementation details of the bistable display device100are further described below.

FIG. 2is a schematic diagram of an image signal at different timings according to an embodiment of the disclosure. InFIG. 2, the bistable display device100may display an image signal210at a first timing t0, an image signal220at a second timing t1, an image signal230at a third timing t2, and an image signal240at a fourth timing t3. The first timing t0to the fourth timing t3are respectively in a time order. The first timing t0, the second timing t1, the third timing t2and the fourth timing t3in the present description refer to time points at which the display panel101reaches a steady state.

FIG. 3andFIG. 4are schematic diagrams showing that a timing controller reads image signals from a buffer apparatus at different timings according to an embodiment of the disclosure. Referring toFIG. 3andFIG. 4in combination withFIG. 2, inFIG. 3, the bistable display device100displays the image signal210at the first timing t0and intends to display the image signal220at the next timing (the second timing t1).

At present, the first image buffer IB1stores the displayed image signal210, and the image signal220to be displayed is pre-loaded into the second image buffer IB2. The timing controller120reads the image signal210and the image signal220from the first image buffer IB1and the second image buffer IB2respectively, and determines that the image signal210is the previous image signal and the image signal220is the current image signal. Then, the timing controller120performs look-up on the look-up table LUT according to the current image signal (the image signal220) and the previous image signal (the image signal210) to generate a pixel signal PS to drive the display panel101to display the image signal220at the second timing t1.

Then, inFIG. 4, the bistable display device100is to display the image signal230at the third timing t2, so the image signal230is temporarily stored in the first image buffer IB1, and the second image buffer IB2continues to maintain the image signal220. The timing controller120reads the image signal230and the image signal220from the first image buffer IB1and the second image buffer IB2respectively, and determines that the image signal220is the previous image signal and the image signal230is the current image signal. The timing controller120performs look-up on the look-up table LUT according to the current image signal (the image signal230) and the previous image signal (the image signal220) to generate a pixel signal PS to drive the display panel101to display the image signal230at the third timing t2.

If the bistable display device100further needs to continuously display a new image at the next timing (e.g., the fourth timing t3), the second image buffer IB2temporarily stores the next image signal240instead, while the first image buffer IB1continues to maintain the image signal230. By parity of reasoning, if the bistable display device100has no images to be updated, the second image buffer IB2may be in an idle state, while the first image buffer IB1continues to maintain the image signal230.

It is worth mentioning that data characters stored in the first image buffer IB1and the second image buffer IB2are exchanged in turn, and when the next image signal to be displayed is loaded into the buffer apparatus130, it may be alternately selected to be temporarily stored in the first image buffer IB1or the second image buffer IB2. Compared with the prior art that the current image signal needs to be copied to a specific storage location, or the current image signal is copied to another specific storage location serving as an updated previous image signal after an image is updated, by receiving the current image signal in turn and receiving the buffer temporary data of the current image signal to serve as previous image data at the next timing, the driving circuit102of the present embodiment may omit the above data copying step to achieve an effect of increasing the image updating speed of the bistable display device100.

For example, the page updating time of an existing bistable display device generally exceeds several milliseconds, but the page updating time of the bistable display device100of the present embodiment may be less than 1 millisecond, and thus has the effect of significantly increasing the image updating speed.

FIG. 5andFIG. 6are schematic diagrams showing that a timing controller reads image signals from a buffer apparatus at different timings according to another embodiment of the disclosure. In the embodiments ofFIG. 5andFIG. 6, the buffer apparatus130includes a third image buffer IB3in addition to the first image buffer IB1and the second image buffer IB2. The third image buffer IB3is also coupled to the timing controller120and configured to temporarily store an image signal. The timing controller120may select one of the first image buffer IB1, the second image buffer IB2and the third image buffer IB3in turn to temporarily store an image signal of a next image, and correspondingly select the image signals stored in the other two of the first image buffer IB1, the second image buffer IB2and the third image buffer IB3as the current image signal and the previous image signal.

InFIG. 5, the bistable display device100displays an image signal210at present. The image signal210is temporarily stored in the first image buffer IB1. The bistable display device100then intends to sequentially display an image signal220and an image signal230. The next image signal220to be displayed has been temporarily pre-stored in the second image buffer IB2. The timing controller120reads the image signal210and the image signal220from the first image buffer IB1and the second image buffer IB2respectively. At the moment, the image signal210is determined as the previous image signal, and the image signal220is determined as the current image signal. The timing controller120generates a pixel signal PS to the source driver110according to the current image signal (the image signal220) and the previous image signal (the image signal210), and drives the display panel101to display the image signal220correspondingly at the second timing t1. Besides, the third image buffer IB3may load a next (the third timing t2) image signal230to be displayed in advance.

Then, at the second timing t1, the bistable display device100displays the image signal220, and the second image buffer IB2continues to temporarily store the image signal220. The image signal230has been stored in the third image buffer IB3. The timing controller120changes the reading path to read the image signal220and the image signal230from the second image buffer IB2and the third image buffer IB3respectively. The timing controller120takes the image signal220as a new previous image signal and the image signal230as a new current image signal. The timing controller120generates a pixel signal PS according to the current image signal (the image signal230) and the previous image signal (the image signal220), and thus drives the display panel101to correspondingly display the image signal230at the third timing t2. If, next, the bistable display device100is to display an image signal240at the fourth timing t3, the first image buffer IB1may load the image signal240to be displayed at the next timing. The rest can be done in the same manner.

In short, the present embodiment increases the image updating speed of the bistable display device100by shortening the delay time with three image buffers IB1to IB3. The three image buffers IB1to IB3may receive the image signals of different timings in a fixed order, and the timing controller120may determine whether the data stored in the image buffers IB1to IB3are the previous image signals or the current image signals according to the order of the received image signals. Two of the three image buffers IB1to IB3are configured to temporarily store the previous image signal and the current image signal, and the third one of the image buffers may be configured to receive the image signal of the next image, so as to optimize a pipeline design. If the bistable display device100is to continue to maintain the current image, the third one of the image buffers may be in the idle state till a new image signal needs to be received.

It should be added that the display data DATA received by the driving circuit102inFIG. 1include the image signals (such as the foregoing image signals210to240) and corresponding pixel actuation location information. The pixel actuation location information records driving location information about these pixels P, for example, records those pixels P needing to change colours or gray scales or records the order of the pixels P to be displayed, but not limited thereto. For example, if the bit value of the pixel actuation location information of a certain pixel P is “1”, it is indicated that the driving circuit102may update the state of the pixel P, and on the contrary, if the bit value of the corresponding pixel actuation location information is “0”, it is indicated that this pixel P may maintain its original state. The pixel actuation location information also may be a two-bit value, e.g.: “00”, “01”, “10” and “11”. The disclosure does not limit the number of bits of the pixel actuation location information and corresponding state setting methods.

In the embodiments ofFIGS. 3 to 6, the first image buffer IB1, the second image buffer IB2, and even the third image buffer IB3may respectively store the image signals of the display data DATA at different timings, but do not need to store the corresponding pixel actuation location information. Specifically, the first image buffer IB1may store only the image signal210, the second image buffer IB2may store only the image signal220, and the third image buffer IB3may store only the image signal230. Therefore, the bandwidth can be saved, and the memory capacity required by the buffer apparatus130can be reduced.

FIG. 7andFIG. 8are schematic diagrams showing that a timing controller reads image signals from a buffer apparatus at different timings according to another embodiment of the disclosure. Referring toFIG. 7andFIG. 8in combination withFIG. 2, in the present embodiment, a buffer apparatus730may replace the buffer apparatus130of the bistable display device100. The buffer apparatus730is similar to the buffer apparatus130in structure, but the buffer apparatus730includes, in addition to at least one image buffer (including the first image buffer IB1and the second image buffer IB2herein), a display image buffer DB configured to temporarily store a previous image signal. The timing controller120is coupled to the source driver110, the first image buffer IB1, the second image buffer IB2and the display image buffer DB. In the present embodiment, the current image signal is temporarily stored in one of the first image buffer IB1and the second image buffer IB2in turn, and the other one of the first image signal IB1and the second image signal IB2may be configured to temporarily store an image signal of a next image.

InFIG. 7, the bistable display device100displays the image signal210of the first timing t0at present, and the image signal210is stored in the display image buffer DB. A difference from the foregoing image buffers IB1to IB3is that the display image buffer DB also stores corresponding pixel actuation location information Inf. The bistable display device100is to display the image signal220at the second timing t1, and the image signal220is temporarily stored in one (the first image buffer IB1herein) of the first image buffer IB1and the second image buffer IB2.

The timing controller120regularly reads the previous image signal (the image signal210at the moment) from the display image buffer DB, and reads the current image signal in the first image buffer IB1. It should be particularly noted that in the present embodiment, the timing controller120may perform the look-up mechanism according to the image signal210and the image signal220in the process of generating the pixel signal PS, and also may generate a pixel signal PS according to the pixel actuation location information Inf of the display image buffer DB. Since the pixel actuation location information Inf has driving information that records the pixel P of each location, the timing controller120may determine a display order of the corresponding pixels P or whether to continue the driving according to the pixel actuation location information Inf. Therefore, the driving circuit102of the present embodiment may implement a regional driving technique according to the pixel actuation location information Inf. For example, only partial pixels P are updated.

If the bistable display device100is to continue to change the display image, the second image buffer IB2may receive the image signal230to be displayed at the next timing (the third timing t2), and on the contrary, the second image buffer IB2may be in the idle state.

After the bistable display device100displays the image signal220, the timing controller120may copy the image signal220temporarily stored in the first image buffer IB1to the display image buffer DB to update the previous image signal.

At the third timing t2, the timing controller120reads the previous image signal (the image signal220at the moment) from the display image buffer DB, but reads the image signal230from the second image buffer IB2instead. That is, the timing controller120may alternately select to receive the current image signal from the first image buffer IB1and the second image buffer IB2.

Similarly, after the bistable display device100displays the image signal230, the timing controller120may copy the image signal230from the second image buffer IB2to the display image buffer DB serving as an updated previous image signal. The first image buffer IB1that originally stores the image signal210also may receive the image signal240of the next timing or return to the idle state.

Those skilled in the art can obtain sufficient teachings or suggestions according to the above implementation descriptions to understand the subsequent display operation flow of the bistable display device100, and the descriptions thereof are omitted below.

It should be particularly noted that the bistable display device100of the present embodiment still omits the step of copying the current image signal to a specific buffer before displaying an image, and directly reads the current image signal from the image buffer, so the page updating time may still be less than 1 millisecond, which greatly reduces the display image updating delay. Meanwhile, the pixel actuation location information Inf in the display image buffer DB needs to be updated in the later stage of the driving process of the display panel101, so that the effect of reducing the occupied bandwidth of the buffer apparatus130is still achieved compared to the prior art.

Based on the above, the bistable display device and the driving circuit of the embodiments of the disclosure omit the step of copying the current image signal to display an image mainly by a mode of directly reading the current image signal from the image buffer, so that the bistable display device and the driving circuit of the embodiments of the disclosure can reduce the display image updating delay and achieve a fast page change effect.