TWI553614B - Common voltage driving method and circuit for electro-phoretic display - Google Patents

Description

Common electrode driving method and circuit applied to electrophoretic display

The present invention relates to a driving circuit, and more particularly to a common electrode driving method and circuit applied to an electrophoretic display.

An electro-phoretic display (EPD) is a display device that can control the movement of colored charged particles by an electric field in an electrophoresis system such as a microcapsule to display an image. The electrophoretic display has the characteristics of power saving, no need for backlighting, and the fact that the screen does not disappear after power-off, and has been widely used in various fields.

The existing electrophoretic display can be driven by an active matrix, including an upper and a lower substrate, a TFT driving circuit and a common electrode respectively disposed on the upper and lower substrates, and an electrophoretic layer interposed between the upper and lower substrates. The TFT driving circuit receives the scanning signal to turn on each pixel, so that the turned-on pixel corresponds to the receiving pixel voltage; the common electrode receives the common voltage for biasing the pixel voltage of each pixel to form a specific electric field to change. The position of the colored charged particles in the electrophoretic structure layer is used to display grayscale images.

However, since the common voltage of the common electrode described above often needs to be switched between positive and negative voltage levels (for example, +15V and -15V), the positive voltage level is directly switched to the negative voltage level or directly from the negative voltage level. Switching to a positive voltage level often results in some additional power loss.

Therefore, it is necessary to provide a common electrode driving method and circuit applied to an electrophoretic display to solve the problems of the conventional technology.

The main object of the present invention is to provide a common electrode driving method applied to an electrophoretic display, in which a bias current of an operational amplifier of a common electrode driving circuit is turned off during switching of a common electrode between two different (positive and negative) voltages, and A third voltage is applied to reduce the power consumption caused by switching between positive and negative voltages; the bias current of the operational amplifier is turned off, which reduces the operational power consumption of the operational amplifier, and also prevents the operational amplifier from affecting the output voltage. And cause extra power consumption.

To achieve the above object, the present invention provides a common electrode driving method for an electrophoretic display, the common electrode driving method comprising the steps of: receiving write data; outputting a positive voltage level or a negative through an operational amplifier according to the written data. a common voltage of the voltage level; comparing whether the current written data and the next written data satisfy a predetermined difference value; when a predetermined difference value is satisfied between the currently written data and the next written data, a switching signal is generated; The switching signal turns off the bias current of the operational amplifier, causes the operational amplifier to output a zero voltage level; and ends the switching signal and continues to receive the next written data.

In an embodiment of the present invention, the step of receiving the write data is performed by a temporary storage unit to latch and store the write data of a timing controller.

In an embodiment of the present invention, the write data stored in the temporary storage unit is converted into a corresponding common voltage switching signal by a decoding unit, and the common voltage switching signal is used to control the operational amplifier to selectively receive the positive voltage standard. The reference voltage of the bit or negative voltage level is amplified and output as a common voltage.

In an embodiment of the present invention, whether the current write data and the next written data satisfy the predetermined difference value by a logic control unit, and the data is currently written When the predetermined difference value is satisfied between the next written data, the logic control unit generates the switching signal by combining a pulse signal.

The present invention further provides a common electrode driving circuit for an electrophoretic display, comprising: a temporary storage unit for receiving a latch enable signal for capturing and storing a write data; and a decoding unit coupled An output end of the temporary storage unit is configured to convert the write data stored in the temporary storage unit into a corresponding common voltage switching signal; a logic control unit is coupled to the output end and the input end of the temporary storage unit, And comparing whether the current write data and the next write data satisfy a predetermined difference value, and outputting a switch signal when the predetermined difference value is satisfied; and an operational amplifier coupled to the decoding unit and the logic control unit, Selectingly receiving reference voltages of different voltage levels according to a common voltage switching signal from the decoding unit, and amplifying the output as a common voltage, wherein the operational amplifier turns off its input bias current when receiving the switching signal, And its output outputs zero voltage.

In an embodiment of the invention, the temporary storage unit is a latch.

In an embodiment of the invention, the common voltage switching signal includes a first common voltage switching signal for controlling the input positive voltage level, a second common voltage switching signal for controlling the input zero voltage level, and a control input negative voltage level. The third common voltage switching signal.

In an embodiment of the present invention, the logic control unit has another input terminal for receiving a pulse signal, and when the logic control unit compares the current written data with the next written data to satisfy the predetermined difference value, The logic control unit outputs the switching signal in combination with the pulse signal.

In summary, the present invention mainly compares the difference between the data written before and after through a logic control unit. When it is judged that the difference in the setting is satisfied, it means that the common voltage needs to be from the current level. Outputting a switching signal turns off the op amp bias current and simultaneously switches the output of the op amp from the current level to the zero level ground level, and then switches to the next level. Compared with directly switching from the current level to the next level, the action of the present invention to cut to the zero voltage level is equal to the work of only paying the zero voltage level to the next voltage level, thereby effectively reducing power consumption. Further, the number of display switching of the electrophoretic display is prolonged.

10‧‧‧Scratch unit

11‧‧‧Decoding unit

12‧‧‧Logical Control Unit

13‧‧‧Operational Amplifier

1 is a schematic diagram of a common electrode driving circuit applied to an electrophoretic display according to a preferred embodiment of the present invention; FIG. 2 is a signal waveform diagram of a common electrode driving circuit of FIG. 1; and FIG. 3 is a first FIG. A signal waveform diagram of an output terminal of an operational amplifier of a common electrode driving circuit; and FIG. 4 is a flow chart of a common electrode driving method applied to an electrophoretic display according to a preferred embodiment of the present invention.

The above and other objects, features and advantages of the present invention will become more <RTIgt; Furthermore, the directional terms mentioned in the present invention, such as upper, lower, top, bottom, front, rear, left, right, inner, outer, side, surrounding, central, horizontal, horizontal, vertical, longitudinal, axial, Radial, uppermost or lowermost, etc., only refer to the direction of the additional schema. Therefore, the directional terminology used is for the purpose of illustration and understanding of the invention.

The present invention provides a common electrode driving circuit applied to an electrophoretic display. The Electrophoretic displays generally include major components such as timing controllers, scan drivers, data drivers (or source drivers), and electrophoretic panels. The timing controller is configured to receive screen data of a display screen and output corresponding display materials accordingly. The scan driver and the data driver are coupled to the timing controller, wherein the timing controller controls the scan driver to sequentially output a plurality of scan signals to sequentially turn on each pixel unit of the electrophoretic panel; the data driver receives the timing The display data output by the controller provides a corresponding pixel voltage to each pixel unit that is turned on. The electrophoretic panel is composed of an upper and a lower substrate, a common electrode, a pixel electrode, and an electrophoretic layer between the upper and lower substrates, wherein the common electrode receives a common voltage; each pixel electrode is connected to a TFT unit to constitute the above a pixel unit; when the TFT unit is turned on by the scanning signal, the pixel electrode receives the pixel voltage, and the common voltage of the common electrode forms a voltage across the electrode; the electrophoresis layer, in one embodiment, may be composed of a plurality of microcapsules, wherein Each of the microcapsules contains colored charged particles, such as positively charged black particles and negatively charged white particles, which are respectively moved to different positions above and below under the electric field generated by the above-mentioned cross-pressure to form an image.

The common electrode driving circuit of the present invention is a common voltage for generating the above-mentioned common electrode. Referring to FIG. 1, a common electrode driving circuit applied to an electrophoretic display according to a preferred embodiment of the present invention is disclosed. The common electrode driving circuit mainly includes a temporary storage unit 10, a decoding unit 11, a logic control unit 12, and an operational amplifier 13.

Referring to Fig. 2, it is a signal waveform diagram of the common electrode driving circuit of Fig. 1. The temporary storage unit 10 can be a latch for receiving a latch enable signal from the timing controller to capture and store a write data. The written data is the display data of the timing controller.

The decoding unit 11 is coupled to an output end of the temporary storage unit 10 for The write data stored in the storage unit 10 is converted into a corresponding common voltage switching signal (swp, sw0, swn), which may include a first common voltage switching signal swp for controlling the input positive voltage level, and a second control input zero voltage level. The common voltage switching signal sw0 and the third common voltage switching signal swn that controls the input negative voltage level.

The two input ends of the logic control unit 12 are respectively coupled to the output end and the input end of the temporary storage unit 10, and simultaneously receive the next write data data_bus from the timing controller and the current write stored by the temporary storage unit 10. The data is used to compare whether the currently written data and the next written data satisfy a predetermined difference value. The logic control unit 12 has another input terminal for receiving a pulse signal PWS. When the logic control unit 12 compares the current write data with the next write data to satisfy the predetermined difference value, the logic control unit 12 combines The pulse signal PWS outputs a switching signal sw.

The operational amplifier 13 is coupled to the decoding unit 11 and the logic control unit 12, and selectively receives reference voltages of different voltage levels according to a common voltage switching signal (swp, sw0, swn) from the decoding unit 11, and It is amplified and output as a common voltage for supplying the common electrode of the above electrophoretic display. Specifically, in this embodiment, the inverting input terminal of the operational amplifier 13 is connected to the three output terminals of a reference voltage supply unit through a resistor, and the three output terminals of the reference voltage supply unit respectively output positive voltage standards. The reference voltage VPOS of the bit, the ground voltage GND, and the reference voltage VNEG of the negative voltage level; the DC voltage VDC is connected across the inverting input terminal and the output terminal of the operational amplifier 13, so as shown in FIG. 3, when When the decoding unit 11 outputs the first common voltage switching signal swp for controlling the input positive voltage level, the operational amplifier 13 correspondingly outputs -VDC-VNEG; when the decoding unit 11 outputs the second common voltage for controlling the input zero voltage level When the signal sw0 is switched, the corresponding output of the operational amplifier 13 is -VDC; when the decoding When the unit 11 outputs the third common voltage switching signal swn that controls the input negative voltage level, the operational amplifier 13 corresponds to the output of -VDC-VPOS. In addition, the power terminal and the output terminal of the operational amplifier 13 are coupled to the output end of the logic control unit 12, and the operational amplifier 13 is controlled by the switching signal sw output by the logic control unit 12, and receives the switching signal sw to close. The bias current, the output of the operational amplifier 13 outputs zero voltage.

Since the logic control unit 12 compares the current write data with the next write data to satisfy the predetermined difference value, the switch signal sw is output to turn off the bias current of the operational amplifier 13, so that the output of the operational amplifier 13 is from the original positive/ Before the common voltage of the negative voltage level is ready to switch to the next level, switch to the ground voltage of the zero voltage level and then switch to the next level to avoid switching directly from the positive/negative voltage level to the next level. . Therefore, compared with directly switching from the positive/negative voltage level to the next level, the action of first cutting to the zero voltage level is equal to the work of only paying the zero voltage level to the next voltage level. Effectively reduce power consumption, thus extending the number of display switching of the electrophoretic display. Furthermore, the op amp's bias current is turned off, which reduces the operational power consumption of the op amp, and also prevents the op amp operation from affecting the output voltage and causing additional power consumption.

Further referring to FIG. 4, based on the above-described common electrode driving circuit, the present invention provides a common electrode driving method, comprising the following steps: 100: receiving write data, wherein the temporary storage unit 10 captures and stores in a latching manner. Writing data of a timing controller; 101: outputting a common voltage of a positive voltage level or a negative voltage level through an operational amplifier according to the written data, wherein the data stored in the temporary storage unit 10 is decoded by the decoding unit 11 Converting into a corresponding common voltage switching signal, and the common voltage switching signal control operational amplifier 13 selectively receives the reference voltage of the positive voltage level or the negative voltage level, and amplifies and amplifies The output is used as a common voltage for supplying the common electrode of the electrophoretic display; 102: comparing whether the current write data and the next written data satisfy a predetermined difference value, wherein the current write data and the next write are compared by the logic control unit 12. Whether the incoming data satisfies a predetermined difference value, and when the predetermined difference value is satisfied between the currently written data and the next written data, the logic control unit 12 generates a switching signal sw in combination with the pulse signal PWS; 103: is turned off by the switching signal The operational amplifier's bias current is such that the operational amplifier outputs a zero voltage level, wherein the operational amplifier 13 is controlled by the switching signal sw outputted by the logic control unit 12, and receives the switching signal sw to turn off the bias current. The output of the amplifier 13 outputs a zero voltage (ground voltage); and 104: ends the switching signal and continues to receive the next written data, that is, returns to the foregoing step 100.

In summary, the present invention mainly compares the difference between the data written before and after through a logic control unit. When it is judged that the difference in the setting is satisfied, it means that the common voltage needs to be switched from the current level (for example, -15V) to the next level. (+15V), that is, outputting a switching signal to turn off the op amp bias current, and cut the output of the op amp from the current level (-15V) to the ground voltage (0V) of the zero level, and then switch to Next level (+15V). Compared to directly switching from the current level (-15V) to the next level (+15V), the following level of +15V reference requires 30C of charge, and the present invention first cuts to zero voltage level. The action is equal to only a charge of 15C from the zero voltage level (0V) to the next voltage level (+15V), so the power consumption can be effectively reduced, thereby prolonging the display switching times of the electrophoretic display.

Although the present invention has been disclosed in its preferred embodiments, it is not intended to limit the invention, and any person skilled in the art can make it without departing from the spirit and scope of the invention. Various changes and modifications are intended to be included within the scope of the appended claims.

10‧‧‧Scratch unit

11‧‧‧Decoding unit

12‧‧‧Logical Control Unit

13‧‧‧Operational Amplifier

Claims (7)

A common electrode driving method for an electrophoretic display, comprising the steps of: receiving a write data, wherein a write-once unit captures and stores a write data of a timing controller through a temporary storage unit; An operational amplifier outputs a common voltage of a positive voltage level or a negative voltage level; compares whether the current written data and the next written data satisfy a predetermined difference value; and satisfies between the currently written data and the next written data. When the difference value is predetermined, a switching signal is generated; the bias current of the operational amplifier is turned off by the switching signal to cause the operational amplifier to output a zero voltage level; and the switching signal is ended and the next written data is continuously received. The common electrode driving method for an electrophoretic display according to claim 1, wherein the writing data stored in the temporary storage unit is converted into a corresponding common voltage switching signal by a decoding unit, and the common voltage switching signal is used. The operational amplifier is controlled to selectively receive a reference voltage of a positive voltage level or a negative voltage level, and is amplified and output as a common voltage. The common electrode driving method applied to an electrophoretic display according to the second aspect of the patent application, wherein a logic control unit compares whether the current written data and the next written data satisfy the predetermined difference value, and writes the data at present. When the predetermined difference value is satisfied between the next written data, the logic control unit generates the switching signal in combination with a pulse signal. A common electrode driving circuit for an electrophoretic display, comprising: a temporary storage unit for receiving a latch enable signal for capturing and storing a write data; and a decoding unit coupled to the temporary storage unit An output end is configured to convert the write data stored in the temporary storage unit into a corresponding common voltage switching signal; a logic control unit is coupled to the output end and the input end of the temporary storage unit for comparing the current Whether the written data and the next written data satisfy a predetermined difference value, and outputs a switching signal when the predetermined difference value is satisfied; and an operational amplifier coupled to the decoding unit and the logic control unit according to the Decoding unit common voltage switching signal and selectively receiving reference voltages of different voltage levels, and amplifying and outputting as a common voltage, wherein the operational amplifier turns off its input bias current when receiving the switching signal, and its output end Output zero voltage. The common electrode driving circuit applied to the electrophoretic display according to claim 4, wherein the temporary storage unit is a latch. The common electrode driving circuit applied to the electrophoretic display according to the fourth aspect of the invention, wherein the common voltage switching signal comprises a first common voltage switching signal for controlling the input positive voltage level and a second common control input zero voltage level. The voltage switching signal and a third common voltage switching signal that controls the input negative voltage level. The common electrode driving circuit applied to the electrophoretic display according to claim 4, wherein the logic control unit has another input terminal for receiving a pulse signal, and when the logic control unit compares the current write data with the next write When the data meets the predetermined difference value, the logic control unit outputs the pulse signal in combination with the pulse signal The signal number.