The present invention relates to a digital electrophoretic display panel driving device and a method thereof, and more particularly, to a driving device and a method for a electrophoretic display (electronic paper).

A electrophoretic display (EPD), or so-called electronic paper is different from conventional papers, EPD is made of conductive polymer material comprising many "microspheres" (or microcapsules), which is flexible and capable of displaying data thereon repeatedly. In electronic paper techniques, the size of the micro capsules represents the size of the pixels; besides, micro capsules are tended to change their states as driven by an external voltage. The US patent publication No.20060050050 discloses a electronic ink display whose conductivity is tended to change as driven by an external voltage, therefore the material of the electronic ink display must be conductive; meanwhile, the electronic ink display uses polymer material to provide flexibility and can be bent like papers.

The EPD (electronic paper) is advantageous in that its brightness is three to six times of that of reflective color LCD for people to easily read it in the dark or under direct sunlight; the contrast of the EPD is higher than the newspaper with no limitation in its viewing angle.

The EPD is able to display content even after the power is off, which means the battery life of the portable device can be extended; the power consumption of the EPD is only 1/1000 as compared to the display of notebook computer as it doesn't require backlight.

Furthermore, the EPD displays contents as they are printed on the paper, therefore the reader will not get tired easily as compared with reading contents from the LCD display; besides, the EPD is thinner and lighter than the common LCD display.

According to Wikipedia (www.wikipedia.org), please refer to the link: http://en.wikipedia.org/wiki/Electronic paper. EPD (electronic paper) was first developed in the 1970s by Nick Sheridon at Xerox's Palo Alto Research Center. The first electronic paper, called Gyricon, consisted of polyethylene spheres between 20 and 100 micrometres across. Each sphere is composed of negatively charged black plastic on one side and positively charged white plastic on the other. The polarity of the voltage applied to each pair of electrodes then determines whether the white or black side is face-up, thus giving the pixel a white or black appearance

Later, the second generation of EPD uses microcapsules each contains positively charged white particles and negatively charged black particles (E ink) suspended in a clear fluid. When a negative electric field is applied, the white particles move to the top of the microcapsule where they become visible to the user. This makes the surface appear white at that spot. At the same time, an opposite electric field pulls the black particles to the bottom of the microcapsules where they are hidden. By reversing this process, the black particles appear at the top of the capsule, which now makes the surface appear dark at that spot. In other words, one microcapsule can display two different colors. These microcapsules are suspended in a liquid "carrier medium" allowing them to be printed onto virtually any surface, including glass, plastic, fabric and even paper.

Since the EPD (electronic paper) is highly portable, reusable, fast to update, low cost and even provides hand written input, therefore the emerging electronic paper will bring revolution to the publishing industry. People can carry electronic papers along to update news or information at any time, any place, and to modify documents as desired. More importantly, electronic papers help to conserve the environment and reduce consumption of papers (the annual consumption is over 200 million tons) to maintain ecological balance.

Furthermore, the EPD changes the traditional media. Japanese government announced that it intended to transmit news digitally to every user's computer for users browse the contents using specific software and to even download the contents to their electronic papers via wireless network. Forrester Research said that electronic paper stands a chance to replace the popular LCD displays and changes the way people read.

However, the developing EPD (electronic paper) still presents several issues to be overcome such as production cost, lasting time, driving voltage, reliability, and response time. Although all kinds of publishing materials are now undergoing digitization process and various devices are developing to display digital contents, one problem remained to be solved is how to make reading experience with electronic papers similar to that with conventional papers. This involved improving the electronic paper to be much readable for text/image, re-writable for documents, and to consume less power in displaying and storage.

In prior art electrophoretic display (EPD) panel driving method, please refer to the flowchart in FIG.1, each EPD panel is slightly different due to parameters, material, packaging or environment in the front end process (10), therefore panel suppliers will provide different common electrode voltages (Vcom) (11). Hence, in driving each EPD panel, it is necessary to adjust the Vcom on the system board. The back end process for EPD panels (12) is to cut the EPD display panel and to integrate it with other components such as capacitors, driving IC, frame, flexible printed circuit and so on, then in system manufacturing process, the Vcom of the EPD is modified manually by adjusting the variable resistor (13). Then the waveform voltage value is written to the memory in the system board (14). After the system verifies the displaying contents (15, 16), the waveform voltage values are read from the memory in the system board and combined with the Vcom to display contents (18). Please refer to the electrophoretic display panel driving device in FIG.1A, manually adjusting variable resistor (111) prevents loading effect from affecting the Vcom, therefore the buffer circuit (112) is used for outputting voltage to switch input/output terminals. The controller chip is provided for controlling the output of the common electrode voltage switch (114) to the output terminal (115).

It is an object of the present invention to provide a digital electrophoretic display panel driving method and apparatus to reduce the time required in adjusting the variable resistor when replacing the electrophoretic display panel; and to facilitate panel usage of the electrophoretic display. The prior art technique adjusts the variable resistor manually to change the common electrode voltage (Vcom), which could lead to long adjustment time and huge labor; besides, there could be misadjustment or manual error problems.

In order to achieve the above object, the present invention provides a digital electrophoretic display panel driving method and apparatus. The new method reads the setup value digitally from the memory without manual adjustment to save time and labor and to reduce the voltage error of the common electrode voltage (Vcom), since the digital voltage error is less than the voltage error adjusted by the variable resistor.

The prior art EPD is driven by adjusting the variable resistor. When it is going through a maintenance or a production test, the Vcom setup value of the system board should match that of the panel, therefore it could lead to long time wasted in searching for suitable panels.

The present invention reads the Vcom from the memory in the panel, it is convenient for the maintenance worker or the tester since they don't need to find matched panels or to re-adjust the variable resistor.

Please refer to the following description and figures for further understanding of the present invention and its objects, wherein:

• FIG.1 illustrates a flowchart of a method for driving a traditional electrophoretic display panel;
• FIG.1A illustrates a structural view of the traditional electrophoretic display panel;
• FIG.2A illustrates a structural view of a digital electrophoretic display panel driving device;
• FIG.2B illustrates aother structural view of a digital electrophoretic display panel driving device;
• FIG.3 illustrates a block diagram of a electrophoretic display panel;
• FIG.4 illustrates a flowchart of a method for driving a electrophoretic display panel; and
• FIG.4A illustrates a view of how to convert the memory data of a digital electrophoretic display into a common electrode voltage;
• FIG.4B illustrates another view of how to convert the memory data of a digital electrophoretic display into a common electrode voltage.

The advantages and innovative features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

The present invention provides a digital electrophoretic display panel driving method and apparatus to use a memory to store common electrode voltage (Vcom) setup value and the panel driving data; the present digitally reads the setup value from the memory without manual adjustment to save time/labor and to avoid manual error. The digital electrophoretic display (EPD) panel driving device comprises a panel driving memory disposed on the EPD for storing digital panel driving data, and a connecting circuit for a controller chip to read the data in the panel driving memory via the connecting circuit.

Please refer to the embodiment of FIG.2A, wherein a flexible printed circuit (23) of the electrophoretic display panel (2) is mainly added with a panel driving memory (24) thereon, and the NC pin of the flexible printed circuit tail (26) is added with a memory IC (25) connecting with a controller chip (61).

Please refer to the embodiment of FIG.2B, wherein a glass of the electrophoretic display panel (2) is mainly added with the panel driving memory (24) thereon, and the NC pin of the flexible printed circuit tail (26) is added with a memory IC (25) connecting with the controller chip (61).

Since each EPD panel is slightly different due to parameters, material, packaging or environment in the front end process, therefore it is necessary to use different common electrode voltages (Vcom) in driving different EPD panels. The back end process for EPD panels is to cut the EPD display panel and to integrate it with other components such as capacitors, driving IC, frame, flexible printed circuit and so on, then in system manufacturing process, the Vcom of the EPD is modified manually by adjusting the variable resistor. The present invention provides a digital electrophoretic display panel driving method and apparatus to store different common electrode voltages (Vcom) of EPD panels in memory; besides, the memory can be used for storing driving voltage waveform value. As illustrated by Taiwan patent application No.096127424, which provides an active EPD driving method, the present invention discloses a plurality of sub pixels aligned in a matrix, wherein a single or a plurality of pixels are sequentially driven. When an image is inputted, the invention obtains a grey level value for each pixel and sequentially drives the pixels. First, apply driving voltages to convert all pixels into one of the two predefined grey level values. Later, sequentially drive the pixels based on pre-defined resolution; calculate the time and the voltages required for driving the pixels from one grey level value to another grey level value to accelerate the display speed of the EPD. Next, adjust the total driving time of each grey level value to increase or reduce the driving time for each grey level value respectively, in doing this, it is useful to control the display of each grey level value. The driving time or the driving voltage data can be stored on the memory of the EPD panel. Please refer to the embodiment in FIG.3, a power supply (34) provides power to a microcontroller(MCU)(33), the controller chip (31) reads the data from the panel driving memory (24) via the FPC tail (26) and the flexible printed circuit connecting terminal (27), and the controller chip (31) uses the panel power module (32) to provide power to the electrophoretic display panel (2) on the panel module (62). After the data is read, it is converted by the controller chip into an analog voltage signal for the driving chip (21) to drive the EPD. Please refer to FIG.4 for a flowchart of a method for driving the EPD panel. Since each EPD panel is slightly different due to parameters, material, packaging or environment in the front end process (40), therefore it is necessary to use different common electrode voltages (Vcom) (41) provided by the panel supplier to drive different EPD panels and to store digital driving data and the Vcom in the driving memory. The back end process (42) for EPD panels is to cut the EPD display panel and to integrate it with other components such as capacitors, driving IC, frame, flexible printed circuit and so on, then the EPD is driven according to the following steps:

• Step 1 (44): verifying the data displayed by a system, the system calculates and integrates data from different sources to represent the result through graphics, the system verifies the image presented to the user in this step;
• Step 2 (45): the controller chip reading the digital panel driving data from the panel driving memory; wherein different common electrode voltages (Vcom), driving time or driving voltages provided by the panel supplier are stored in the memory, the digital electrophoretic display panel driving device comprises a panel driving memory disposed on the EPD panel, and also comprises a connecting circuit for a controller chip on the system board to read the data in the panel driving memory via the connecting circuit;
• Step 3 (46): the controller chip converting the digital panel driving data read from the panel driving memory into an analog voltage signal;
• Step 4 (47): the controller chip sending the analog voltage signal to a driving integrated circuit on the EPD panel to drive the EPD panel

Please refer to the embodiment in FIG.4A, wherein the controller chip (51) uses a digital/analog converter (52) in the controller chip to convert the digital panel driving data read from the panel driving memory into an analog voltage signal and to control the common electrode voltage switch (54) to send the analog voltage signal from the voltage inverter (53) via an output terminal (55) to the driving integrated circuit on the display panel.

Please refer to the embodiment in FIG.4B, wherein the controller chip (113) uses the common electrode voltage generator (116) in the controller chip (113) to send the digital panel driving data in the panel driving memory to the common electrode voltage switch (114) for outputting a common electrode voltage via an output terminal (115) to the driving integrated circuit on the display panel.

Many changes and modifications in the above described embodiment of the invention can, of course, be carried out without departing from the scope thereof. Accordingly, to promote the progress in science and the useful arts, the invention is disclosed and is intended to be limited only by the scope of the appended claims.