Source driver and method for determining polarity of pixel voltage thereof

This application claims the priority benefit of Taiwan application serial no. 102128856, filed on Aug. 12, 2013. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

1. Field of the Invention

The invention relates to a driving device of a display, and more particularly, relates to a source driver and a method for determining polarity of pixel voltage thereof.

2. Description of Related Art

In recent years, liquid crystal displays have become a mainstream in the market due to its advantages such as low power consumption, absence of radiation, and high space utilization. In a driving circuit of a display, a source driver is an indispensable element configured to convert a digital image data signal into a pixel voltage and to provide the pixel voltage to the pixel being activated, so that the pixel voltage can be stored in the a storage capacitor formed by the a pixel electrode and a common electrode.

Since the pixel voltage varies with grayscale (i.e., brightness) pending to be displayed, and a variation of a voltage level can be conducted to the common electrode through a capacitance coupling effect of the storage capacitor, such that the voltage level of the common electrode (i.e., a common voltage) is influenced, thereby affecting a display performance of pixels. Further, as sizes of the liquid crystal displays become larger, a size of a liquid crystal display panel is also increased, which results in a number of the pixel voltages provided by the source driver to increase. Accordingly, how to avoid the common voltage from being influenced b the variation of the pixel voltage is gradually becoming an important topic to be discussed.

In addition, in order to reduce a power consumption of the source driver, a charge sharing technology is applied in transmitting the pixel voltage to the liquid crystal display panel. However, the charge sharing technology in a conventional art is generally used in the source driver which generates the pixel voltage by utilizing a dot inversion driving method. However, with continuous advancements of display technologies, driving methods for the source driver are also advanced, so that the charge sharing technology is incapable of reducing the power consumption of the source driver. Therefore, it requires a new charge sharing technology in order to reduce the power consumption of the source driver adopting the new driving methods.

The invention is directed to a source driver and a method for determining polarity of pixel voltage thereof, capable of improving stability of common voltage.

The source driver of the invention includes a data register unit, a plurality of data groups and a plurality of polarity determining units. The data register unit receives an image data signal and provides a plurality of display data. The data groups have at least two data channels respectively. The data channels are coupled to the data register unit to receive the corresponding display data and provide a plurality of pixel voltages. The polarity determining units are respectively coupled to the data channels corresponding to different data groups, and each of the polarity determining units determines whether to invert polarities of a part of the pixel voltages provided by the coupled data channels according to the received display data of the coupled data channels and previous display data corresponding to the received display data.

According to an embodiment of the invention, when preset charging directions of the pixel voltages of the corresponding data groups determined by each of the polarity determining units according to the received display data of the coupled data channels and the previous display data corresponding to the received display data are completely identical, each of the polarity determining units inverts the polarities of the part of the pixel voltages provided by the coupled data channels. When the preset charging directions of the pixel voltages of the corresponding data groups determined by each of the polarity determining units according to the received display data of the coupled data channels and the previous display data corresponding to the received display data are not completely identical, each of the polarity determining units does not invert the polarities of the part of the pixel voltages provided by the coupled data channels.

According to an embodiment of the invention, when each of the data groups includes an even number of data channels, each of the polarity determining units inverts the polarities of a half of the pixel voltages provided by the coupled data channels.

When each of the data groups includes an odd number of data channels, each of the polarity determining units inverts the polarities of a n number of the pixel voltages provided by the coupled data channels, in which n is a positive integer close to a half of a number of the data channels included in each of the data groups.

According to an embodiment of the invention, each of the data channels respectively receives two display data and respectively provides two corresponding pixel voltages, and the polarities of the pixel voltages provided by each of the data channels are different from each other.

According to an embodiment of the invention, each of the data channels includes a first latch, a second latch, a first exchanging unit, a third latch, a fourth latch, a first digital-to-analog converter, a second digital-to-analog converter, a second exchanging unit, a first buffer, a second buffer, a first switch and a second switch. An input terminal of the first latch is coupled to the data register unit to receive the corresponding display data, and an output terminal of the first latch is coupled to the corresponding polarity determining unit to provide the display data received by each of the data channels. An input terminal of the second latch is coupled to the data register unit to receive the corresponding display data, and an output terminal of the second latch is coupled to the corresponding polarity determining unit to provide the display data received by each of the data channels. The first exchanging unit has a first input terminal, a second input terminal, a first output terminal and a second output terminal, and receives a polarity control signal provided by the polarity determining unit, the first input terminal being coupled to the output terminal of the first latch, the second input terminal being coupled to the output terminal of the second latch. According to the polarity control signal, the first exchanging unit controls the first input terminal and the second input terminal to couple the first output terminal and the second output terminal, respectively, or controls the first input terminal and the second input terminal to couple the second output terminal and the first output terminal, respectively. An input terminal of the third latch is coupled to the first output terminal to receive the corresponding display data, and an output terminal of the third latch is coupled to the corresponding polarity determining unit to provide the corresponding previous display data. An input terminal of the fourth latch is coupled to the second output terminal to receive the corresponding display data, and an output terminal of the fourth latch is coupled to the corresponding polarity determining unit to provide the corresponding previous display data. An input terminal of the first digital-to-analog converter is coupled to the output terminal of the third latch to receive the corresponding display data and provide the pixel voltages having a first polarity. An input terminal of the second digital-to-analog converter is coupled to the output terminal of the fourth latch to receive the corresponding display data and provide the pixel voltages having a second polarity. The second exchanging unit has a third input terminal, a fourth input terminal, a third output terminal and a fourth output terminal, and receives the polarity control signal, the third input terminal being coupled to the output terminal of the first digital-to-analog converter, the fourth input terminal being coupled to the output terminal of the second digital-to-analog converter. According to the polarity control signal, the second exchanging unit controls the third input terminal and the fourth input terminal to couple the third output terminal and the fourth output terminal, respectively, or controls the third input terminal and the fourth input terminal to couple the fourth output terminal and the third output terminal, respectively. An input terminal of the first buffer is coupled to the third output terminal to buffer the received pixel voltages. An input terminal of the second buffer is coupled to the fourth output terminal to buffer the received pixel voltages. The first switch is coupled to the first buffer and receives a latch signal so as to output the received pixel voltages under control of the latch signal. The second switch is coupled to the second buffer and receives the latch signal so as to output the received pixel voltages under control of the latch signal.

In the present embodiment, the source driver further includes a plurality of charge sharing units. The charge sharing units are coupled to the output terminals of the data channels corresponding to different data groups, respectively, and coupled to the corresponding polarity determining unit. Therein, each of the polarity determining units determines whether to enable the corresponding charge sharing unit to execute a charge sharing function according to the preset charging directions of the pixel voltages of the corresponding data groups determined according to the received display data of the coupled data channels and the previous display data corresponding to the received display data.

According to an embodiment of the invention, each of the charge sharing units includes a plurality of charge sharing switches respectively coupled between the output terminals of the data channels of the corresponding data groups, and being simultaneously turned on under control of the corresponding polarity determining unit.

The invention also provides a method for determining polarity of pixel voltage of source driver, which includes the following steps: providing a plurality of display data according to an image data signal; providing a plurality of pixel voltages according to the display data, in which the pixel voltages corresponds to a plurality of data groups, respectively, and each of the data groups at least corresponds to two of the pixel voltages; determining a polarity of each of the pixel voltages; and determining whether to invert the polarities of a part of the pixel voltages corresponding to each of the data groups according to the display data corresponding to the each of the data groups and a plurality of previous display data corresponding to the display data.

According to an embodiment of the invention, the step of determining whether to invert the polarities of a part of the pixel voltages corresponding to each of the data groups according to the display data corresponding to the each of the data groups and a plurality of previous display data corresponding to the display data includes: inverting the polarities of the part of the pixel voltages of each of the data groups when the display data corresponding to each of the data groups and the previous display data corresponding to the display data both showing that preset charging directions of the pixel voltages corresponding to each of the data groups are completely identical; and do not inverting the polarities of the part of the pixel voltages of each of the data groups when the display data corresponding to each of the data groups and the previous display data corresponding to the display data both showing that the preset charging directions of the pixel voltages corresponding to each of the data groups are not completely identical.

According to an embodiment of the invention, the method for determining polarity of pixel voltage of source driver further includes: when each of the data groups corresponds to an even number of the pixel voltages, the pixel voltages being inverted is a half of the even number of the pixel voltages.

According to an embodiment of the invention, the method for determining polarity of pixel voltage of source driver further includes: when each of the data groups corresponds to an odd number of pixel voltages, the pixel voltages being inverted is a n number of the odd number of the pixel voltages, in which n is a positive integer close to a half of a number of the pixel voltages corresponding to each of the data groups.

According to an embodiment of the invention, a polarity of each of the pixel voltages and a polarity of a neighboring pixel voltage are different from each other.

According to an embodiment of the invention, the method for determining polarity of pixel voltage of source driver further includes: executing a charge sharing function to the pixel voltages corresponding to each of the data groups when the polarities of the part of pixel voltages of each of the data groups are not inverted.

Based on above, in the source driver and a method for determining polarity of pixel voltage thereof, whether to invert the polarities of the part of the pixel voltages corresponding to each of the data groups is determined according to the display data corresponding to the each of the data groups and the previous display data corresponding to the display data. Accordingly, influences of charging the pixel voltages to the common voltage can be reduced.

To make the above features and advantages of the disclosure more comprehensible, several embodiments accompanied with drawings are described in detail as follows.

FIG. 1A is a schematic view illustrating a system of a source driver according to an embodiment of the invention.

FIG. 1B is a schematic view of waveforms of pixel voltages according to an embodiment of the invention.

FIG. 2A is a schematic view illustrating a system of a source driver according to another embodiment of the invention.

FIG. 2B is a schematic view of waveforms of pixel voltages according to another embodiment of the invention.

FIG. 3A is a schematic view illustrating a system of a source driver according to yet another embodiment of the invention.

FIG. 3B is a schematic view of waveforms of pixel voltages according to yet another embodiment of the invention.

FIG. 3C is a schematic view illustrating a circuit of a source driver according to yet another embodiment of the invention.

FIG. 4 is a flow chart illustrating a method for determining polarity of pixel voltage of source driver according to an embodiment of the invention.

FIG. 1A is a schematic view illustrating a system of a source driver according to an embodiment of the invention. Referring to FIG. 1A , in the present embodiment, a source driver 100 includes a data register unit 110 , a plurality of polarity determining units (e.g., 120 _ 1 , 120 _ 2 ) and a plurality of data channels (e.g., 130 _ 1 to 130 _ 4 ). The data channels (e.g., 130 _ 1 to 130 _ 4 ) are grouped into a plurality of data groups (e.g., G 11 , G 12 ). In the present embodiment, it is illustrated with each of the data groups (e.g., G 11 , G 12 ) including two data channels (e.g., 130 _ 1 to 130 _ 4 ) as an example. In other embodiments, each of the data groups (e.g., G 11 , G 12 ) can include three data channels (e.g., 130 _ 1 to 130 _ 4 ) or more data channels, and the embodiment of the invention is not limited thereto.

The data register unit 110 receives an image data signal SDI, and provides a plurality of display data (e.g., DS 11 to DS 14 ) from data transmitted by the image data signal SDI being organized and arranged. The data channels (e.g., 130 _ 1 to 130 _ 4 ) is coupled to the data register unit 110 to receive the corresponding display data (e.g., DS 11 to DS 14 ) and receive a latch signal LD, so as to provide the corresponding pixel voltages (e.g., VP 11 to VP 14 ) according to the latch signal LD. Therein, a polarity of each of the pixel voltages (e.g., VP 11 to VP 14 ) and a polarity of a neighboring pixel voltage (e.g., VP 11 to VP 14 ) can be different from each other, but the embodiment of the invention is not limited thereto. For instance, the data channel 130 _ 1 receives the display data DS 11 to provide the corresponding pixel voltage VP 11 and the data channel 130 _ 2 receives the display data DS 12 to provide the corresponding pixel voltage VP 12 , and the rest may be deduced by analogy.

The polarity determining units (e.g., 120 _ 1 , 120 _ 2 ) are respectively coupled to the data channels (e.g., 130 _ 1 to 130 _ 4 ) corresponding to different data groups (e.g., G 11 , G 12 ) and configured to receive a polarity signal POL. For instance, the polarity determining unit 120 _ 1 is coupled to the data channels 130 _ 1 and 103 _ 2 of the corresponding data group G 11 , and the polarity determining unit 120 _ 2 is coupled to the data channels 130 _ 3 and 130 _ 4 of the corresponding data group G 12 . Each of the polarity determining units (e.g., 120 _ 1 , 120 _ 2 ) controls the polarities of the pixel voltages (e.g., VP 11 to VP 14 ) provided by each of the data channels (e.g., 130 _ 1 to 130 _ 4 ) through polarity control signals (e.g., PC 11 to PC 14 ), and receives reference data (e.g., DR 11 to DR 14 ) and previous reference data (e.g., DR 11 p to DR 14 p ) from the data channels (e.g., 130 _ 1 to 130 _ 4 ) coupled thereto.

The reference data DR 11 provided by the data channel 130 _ 1 corresponds to the received display data DS 11 , and the reference data DR 11 can be a part of the display data DS 11 (e.g., high bit part), or the entire display data DS 11 . The previous reference data DR 11 p provided by the data channel 130 _ 1 corresponds to the received previous display data DS 11 , and the previous reference data DR 11 p can be a part of the previous display data DS 11 (e.g., high bit part), or the entire previous display data DS 11 . Other reference data (e.g., DR 12 to DR 14 ) and the previous reference data (e.g., DR 12 p to DR 14 p ) may be deduced by analogy, but the embodiment of the invention is not limited thereto.

In the present embodiment, each of the polarity determining units (e.g., 120 _ 1 , 120 _ 2 ) first determines the polarity (e.g., a positive polarity or a negative polarity) of each of the pixel voltages (e.g., VP 11 to VP 14 ) according to the polarity signal POL. Further, each of the polarity determining units (e.g., 120 _ 1 , 120 _ 2 ) then determines whether the polarities of the pixel voltages (e.g., VP 11 to VP 14 ) provided by the coupled data channels (e.g., 130 _ 1 to 130 _ 4 ) require an inversion according the received reference data (e.g., DR 11 to DR 14 ) and the previous reference data (e.g., DR 11 p to DR 14 p ). In other words, each of the polarity determining units (e.g., 120 _ 1 , 120 _ 2 ) determines whether to inverse the polarities of a part of the pixel voltages (e.g., VP 11 to VP 14 ) provided by the coupled data channels (e.g., 130 _ 1 to 130 _ 4 ) according to the received display data (e.g., DS 11 to DS 14 ) of the coupled data channel (e.g., 130 _ 1 to 130 _ 4 ).

Furthermore, the polarity determining units (e.g., 120 _ 1 , 120 _ 2 ) can determine a preset charging direction of each of the pixel voltages (e.g., VP 11 to VP 14 ) according to the polarity of each of the pixel voltages (e.g., VP 11 to VP 14 ) and the display data (e.g., DS 11 to DS 14 ) and the corresponding previous reference data (e.g., DR 11 p to DR 14 p ) received by the data channels (e.g., 130 _ 1 to 130 _ 4 ). Further, in case the preset charging directions of the pixel voltages (e.g., VP 11 to VP 14 ) provided by the data channels (e.g., 130 _ 1 to 130 _ 4 ) corresponding to the same data group (e.g., G 11 , G 12 ) are completely identical, the polarity determining unit (e.g., 120 _ 1 , 120 _ 2 ) can inverse the polarities of the part of the pixel voltages (e.g., VP 11 to VP 14 ) corresponding to the same data group (e.g., G 11 , G 12 ), so that the preset charging directions of the pixel voltages (e.g., VP 11 to VP 14 ) corresponding to the same data group (e.g., G 11 , G 12 ) can be changed to be not completely identical. Otherwise, the polarity determining unit (e.g., 120 _ 1 , 120 _ 2 ) maintains the polarities of the pixel voltages (e.g., VP 11 to VP 14 ).

In other words, when all preset charging directions of the pixel voltages (e.g., VP 11 to VP 14 ) of the corresponding data groups (e.g., G 11 , G 12 ) determined by each of the polarity determining units (e.g., 120 _ 1 , 120 _ 2 ) according to the received display data (e.g., DS 11 to DS 14 ) of the coupled data channels (e.g., 130 _ 1 to 130 _ 4 ) and the previous display data corresponding to the received display data are completely identical, each of the polarity determining units (e.g., 120 _ 1 , 120 _ 2 ) inverts the polarities of the part of the pixel voltages (e.g., VP 11 to VP 14 ) provided by the coupled data channels (e.g., 130 _ 1 to 130 _ 4 ). Otherwise, when the preset charging directions of the pixel voltages (e.g., VP 11 to VP 14 ) of the corresponding data groups (e.g., G 11 , G 12 ) determined by each of the polarity determining units (e.g., 120 _ 1 , 120 _ 2 ) according to the received display data (e.g., DS 11 to DS 14 ) of the coupled data channels (e.g., 130 _ 1 to 130 _ 4 ) and the previous display data corresponding to the received display data are not completely identical, each of the polarity determining units (e.g., 120 _ 1 , 120 _ 2 ) does not invert the polarities of the pixel voltages (e.g., VP 11 to VP 14 ) provided by the coupled data channels (e.g., 130 _ 1 to 130 _ 4 ).

FIG. 1B is a schematic view of waveforms of pixel voltages according to an embodiment of the invention. Referring to FIG. 1A and FIG. 1B , in the present embodiment, it is illustrated with the data channels 130 _ 1 and 130 _ 2 of the data group G 11 as an example. A curve S 110 refers to an internal voltage variation in the data channel 130 _ 1 , for example. Curves S 120 a and S 120 b refer to internal voltage variations in the data channel 130 _ 2 , for example. A curve S 130 refers to a voltage variation of the pixel voltage VP 11 , for example. Curves S 140 a and S 140 b refer to voltage variations of the pixel voltage VP 12 , for example. Therein, according to the latch signal LD, the data channels 130 _ 1 and 130 _ 2 outputs the pixel voltages VP 11 and VP 12 (represented as on) or does not output the pixel voltages VP 11 and VP 12 (represented as off), in which the polarity of the pixel voltage VP 11 is positive (being greater than a common voltage Vcom) and the polarity of the pixel voltage VP 12 is negative (being less than the common voltage Vcom).

In the present embodiment, according to the received display data (DS 11 , DS 12 ) and the previous received display data (DS 11 , DS 12 ) of the data channels 130 _ 1 and 130 _ 2 , the polarity determining unit 120 _ 1 determines that the preset charging directions of the pixel voltages VP 11 and VP 12 at a time point T 1 are completely identical (refers to charging directions of the curve S 130 and S 140 a at the time point T 1 ). In this case, the polarity determining unit 120 _ 1 inverses the polarity of the pixel voltage VP 12 through a polarity control signal PC 12 (i.e., the polarity of the pixel voltage VP 12 is inversed into positive), so that the charging directions of the pixel voltages VP 11 and VP 12 are completely different (refers to charging directions of the curves S 130 and S 140 b at the time point T 1 ). Therein, the preset charging directions are determined based on the polarities of the pixel voltages VP 11 and VP 12 before the inversion.

In the present embodiment, after the polarity of the pixel voltage VP 12 is inversed, the preset charging directions of the pixel voltages VP 11 and VP 12 are not completely identical (refers to charging directions of the curves S 130 and S 140 b at time points T 2 and T 3 ), such that the polarity of the pixel voltage VP 12 is continuously set to positive. In an embodiment of the invention, the polarity determining unit 120 _ 1 can control only the polarity of the pixel voltage VP 12 outputted by the data channel 130 _ 2 . However, in other embodiments, the polarity determining unit 120 _ 1 can alternatively control the polarity of the pixel voltage VP 11 outputted by the data channel 130 _ 1 and the polarity of the pixel voltage VP 12 outputted by the pixel voltage 130 _ 2 . For instance, a first polarity inversion inversing the polarity of the pixel voltage VP 11 , a second polarity inversion inversing the polarity of the pixel voltage VP 12 , and the rest may be deduced by analogy.

In the present embodiment, each of the data channels (e.g., 130 _ 1 to 130 _ 4 ) provides a pixel voltage (e.g., VP 11 to VP 14 ), and each of the data groups (e.g., G 11 , G 12 ) includes two data channels (e.g., 130 _ 1 to 130 _ 4 ). That is, each of the data groups (e.g., G 11 , G 12 ) corresponds to two pixel voltages (e.g., VP 11 to VP 14 ). Also, the polarity determining unit (e.g., 120 _ 1 , 120 _ 2 ) inverses one (i.e., a half of the two pixel voltages) of the polarities of the two pixel voltages (e.g., VP 11 to VP 14 ) corresponding to each of the data groups (e.g., G 11 , G 12 ). However, in other embodiments, each of the data groups (e.g., G 11 , G 12 ) can correspond to three or more pixel voltages (e.g., VP 11 to VP 14 ).

When each of the data groups (e.g., G 11 , G 12 ) corresponds to an even number (e.g., 4 or 6) of the pixel voltages (e.g., VP 11 to VP 14 ), the polarity determining unit (e.g., 120 _ 1 , 120 _ 2 ) can inverse a half (e.g, 2 or 3) of the polarities of the pixel voltages (e.g., VP 11 to VP 14 ) corresponding to each of the data groups (e.g., G 11 , G 12 ). When each of the data groups (e.g., G 11 , G 12 ) corresponds to an odd number (e.g., 3 or 5) of the pixel voltages (e.g., VP 11 to VP 14 ), the polarity determining unit (e.g., 120 _ 1 , 120 _ 2 ) can inverse a number close to a half of the odd number of the pixel voltages (e.g., VP 11 to VP 14 ) corresponding to each of the data groups (e.g., G 11 , G 12 ). For instance, when each of the data groups (e.g., G 11 , G 12 ) corresponds to three pixel voltages (e.g., VP 11 to VP 14 ), the polarity determining unit (e.g., 120 _ 1 , 120 _ 2 ) can inverse one or two (both are close to a half of three, i.e., 1.5) of the pixel voltages (e.g., VP 11 to VP 14 ). When each of the data groups (e.g., G 11 , G 12 ) corresponds to five pixel voltages (e.g., VP 11 to VP 14 ), the polarity determining unit (e.g., 120 _ 1 , 120 _ 2 ) can inverse two or three (both are close to a half of five, i.e., 2.5) of the pixel voltages (e.g., VP 11 to VP 14 ), and the rest may be deduced by analogy.

Moreover, when each of the data groups (e.g., G 11 , G 12 ) corresponds to more than three pixel voltages (e.g., VP 11 to VP 14 ), the polarity determining unit (e.g., 120 _ 1 , 120 _ 2 ) can inverse a part of the pixel voltages (e.g., VP 11 to VP 14 ). For instance, when each of the data groups (e.g., G 11 , G 12 ) corresponds to three pixel voltages (e.g., VP 11 to VP 14 ), the polarity determining unit (e.g., 120 _ 1 , 120 _ 2 ) can inverse one or two of the pixel voltages (e.g., VP 11 to VP 14 ). When each of the data groups (e.g., G 11 , G 12 ) corresponds to four pixel voltages (e.g., VP 11 to VP 14 ), the polarity determining unit (e.g., 120 _ 1 , 120 _ 2 ) can inverse one, two or three of the pixel voltages (e.g., VP 11 to VP 14 ), and the rest may be deduced by analogy.

FIG. 2A is a schematic view illustrating a system of a source driver according to another embodiment of the invention. Referring to FIG. 1A and FIG. 2A , a source driver 200 is similar to the source driver 100 , and the same or similar elements are indicated by the same or similar reference numbers. In the present embodiment, the source driver 200 includes a data register unit 210 , a plurality of polarity determining unit (e.g., 220 _ 1 , 220 _ 2 ) and a plurality of data channels (e.g., 230 _ 1 to 230 _ 4 ). The data channels (e.g., 230 _ 1 to 230 _ 4 ) are grouped into a plurality of data groups (e.g., G 21 , G 22 ). In the present embodiment, it is illustrated with each of the data groups (e.g., G 21 , G 22 ) including two data channels (e.g., 230 _ 1 to 230 _ 4 ) as an example. In other embodiments, each of the data groups (e.g., G 21 , G 22 ) can include three data channels (e.g., 230 _ 1 to 230 _ 4 ) or more data channels, and the embodiment of the invention is not limited thereto.

The data register unit 210 receives an image data signal SDI and provides a plurality of display data (e.g, DS 21 to DS 28 ). The data channels (e.g., 230 _ 1 to 230 _ 4 ) is coupled to the data register unit 210 to receive two corresponding display data (e.g., DS 21 to DS 28 ) and receive a latch signal LD, so as to provide the two corresponding pixel voltages (e.g., VP 21 to VP 28 ) according to the latch signal LD. Therein, polarities of the two pixel voltages (e.g., VP 21 to VP 28 ) of each of the data channels (e.g., 230 _ 1 to 230 _ 4 ) are different from each other, but the embodiment of the invention is not limited thereto.

The polarity determining units (e.g., 220 _ 1 , 220 _ 2 ) are respectively coupled to the data channels (e.g., 230 _ 1 to 230 _ 4 ) corresponding to different data groups (e.g., G 21 , G 22 ) and configured to receive a polarity signal POL. Each of the polarity determining units (e.g., 220 _ 1 , 220 _ 2 ) controls the polarities of the pixel voltages (e.g., VP 21 to VP 24 ) provided by each of the data channels (e.g., 230 _ 1 to 230 _ 4 ) through polarity control signals (e.g., PC 21 to PC 24 ), and receives reference data (e.g., DR 21 to DR 28 ) and previous reference data (e.g., DR 21 p to DR 28 p ). Therein, the reference data DR 21 can be a part of the display data DS 21 (e.g., high bit part) or the entire display data DS 21 , and the previous reference data DR 21 p can be a part of the previous display data DS 21 (e.g., high bit part) or the entire previous display data DS 21 . Other reference data (e.g., DR 22 to DR 28 ) and the previous reference data (e.g., DR 22 p to DR 28 p ) may be deduced by analogy, but the embodiment of the invention is not limited thereto.

In the present embodiment, the polarity determining units (e.g., 220 _ 1 , 220 _ 2 ) first determines the polarity (e.g., the positive polarity or the negative polarity) of each of the pixel voltages (e.g., VP 21 to VP 28 ) according to the polarity signal POL. Further, each of the polarity determining units (e.g., 220 _ 1 , 220 _ 2 ) then determine whether the polarities of the pixel voltages (e.g., VP 21 to VP 28 ) provided by the coupled data channels (e.g., 230 _ 1 to 230 _ 4 ) require an inversion according the received reference data (e.g., DR 21 to DR 28 ) and the previous reference data (e.g., DR 21 p to DR 28 p ). In other words, when all preset charging directions of the pixel voltages (e.g., VP 21 to VP 28 ) of the corresponding data groups (e.g., G 21 , G 22 ) determined by each of the polarity determining units (e.g., 220 _ 1 , 220 _ 2 ) according to the received display data (e.g., DS 21 to DS 28 ) of the coupled data channels (e.g., 230 _ 1 to 230 _ 4 ) and the previous display data corresponding to the received display data are completely identical, each of the polarity determining units (e.g., 220 _ 1 , 220 _ 2 ) inverts the polarities of the part of the pixel voltages (e.g., VP 21 to VP 28 ) provided by the coupled data channels (e.g., 230 _ 1 to 230 _ 4 ). Otherwise, when the preset charging directions of the pixel voltages (e.g., VP 21 to VP 28 ) of the corresponding data groups (e.g., G 21 , G 22 ) determined by each of the polarity determining units (e.g., 220 _ 1 , 220 _ 2 ) according to the received display data (e.g., DS 21 to DS 28 ) of the coupled data channels (e.g., 230 _ 1 to 230 _ 4 ) and the previous display data corresponding to the received display data are not completely identical, each of the polarity determining units (e.g., 220 _ 1 , 220 _ 2 ) does not invert the polarities of the part of the pixel voltages (e.g., VP 21 to VP 28 ) provided by the coupled data channels (e.g., 230 _ 1 to 230 _ 4 ).

FIG. 2B is a schematic view of waveforms of pixel voltages according to another embodiment of the invention. Referring to FIG. 1B , FIG. 2A and FIG. 2B , in which the same or similar elements are indicated by the same or similar reference numbers. In the present embodiment, it is illustrated with the data channels 230 _ 1 and 230 _ 2 of the data group G 21 as an example. Curves S 210 and S 220 refer to internal voltage variations in the data channel 230 _ 1 , for example. Curves S 230 a , S 230 b , S 240 a and S 240 b refer to internal voltage variations in the data channel 230 _ 2 , for example. A curve S 250 refers to a voltage variation of the pixel voltage VP 21 , for example. A curve S 260 refers to a voltage variation of the pixel voltage VP 22 , for example. Curves S 270 a and S 270 b refer to voltage variations of the pixel voltage VP 23 , for example. Curves S 280 a and S 280 b refer to voltage variations of the pixel voltage VP 24 , for example. Therein, according to the latch signal LD, the data channels 230 _ 1 and 230 _ 2 output the pixel voltages VP 21 to VP 28 (represented as on) or do not output the pixel voltages VP 21 to VP 28 (represented as off), in which the polarities of the pixel voltages VP 21 and VP 23 are positive (being greater than the common voltage Vcom) and the polarities of the pixel voltages VP 22 and VP 24 are negative (being less than the common voltage Vcom).

In the present embodiment, preset charging directions of the pixel voltages VP 21 to VP 24 at a time point T 1 are completely identical (refers to charging directions of the curves S 250 , S 260 , S 270 a and S 280 a at the time point T 1 ). Therefore, the polarity determining unit 220 _ 1 inverses the polarities of the pixel voltages VP 23 and VP 24 (i.e., the polarity of the pixel voltage VP 23 is inversed into negative, and the polarity of the pixel voltage VP 24 is inversed into positive), so that the charging directions of the pixel voltages VP 21 to VP 24 are not completely identical (refers to charging directions of the curves S 250 , S 260 , S 270 b and S 280 b at the time point T 1 ). Therein, the preset charging directions are determined based on the polarities of the pixel voltages VP 21 to VP 24 before the inversion.

In the present embodiment, after the polarities of the pixel voltages VP 23 and VP 24 are inversed, the preset charging directions of the pixel voltages VP 11 to VP 24 are not completely identical (refers to charging directions of the curves S 250 , S 260 , S 270 b and S 280 b at time points T 2 and T 3 ), such that the polarity of the pixel voltage VP 23 is continuously set to negative, and the polarity of the pixel voltage VP 24 is continuously set to positive. In an embodiment of the invention, the polarity determining unit 220 _ 1 can control only the polarities of the pixel voltages VP 23 and VP 24 outputted by the data channel 230 _ 2 . However, in other embodiments, the polarity determining unit 220 _ 1 can alternatively control the polarities of the pixel voltages VP 21 and VP 22 outputted by the data channel 230 _ 1 and the polarities of the pixel voltages VP 23 and VP 24 outputted by the pixel voltage 230 _ 2 . That is, a first polarity inversion inversing the polarities of the pixel voltages VP 21 and VP 22 , a second polarity inversion inversing the polarities of the pixel voltages VP 23 and VP 24 , and the rest may be deduced by analogy.

In the present embodiment, each of the data groups (e.g., G 21 , G 22 ) includes two data channels (e.g., 230 _ 1 to 230 _ 4 ), and the polarity determining unit (e.g., 220 _ 1 , 220 _ 2 ) inverses the polarities of the pixel voltages (e.g., VP 21 to VP 28 ) provided by one (i.e., a half of the two data channels) of the two corresponding data channels (e.g., 230 _ 1 to 230 _ 4 ) of each one of the data groups (e.g., G 21 , G 22 ). However, in other embodiments, each of the data groups (e.g., G 21 , G 22 ) can include three or more data channels (e.g., 230 _ 1 to 230 _ 4 ).

When each of the data groups (e.g., G 21 , G 22 ) includes an even number (e.g., 4 or 6) of data channels (e.g., 230 _ 1 to 230 _ 4 ), the polarity determining unit (e.g., 220 _ 1 , 220 _ 2 ) inverses the polarities of the pixel voltages (e.g., VP 21 to VP 28 ) provided by a half (e.g., 2 or 3) of the data channels (e.g., 230 _ 1 to 230 _ 4 ) included in each one of the data groups (e.g., G 21 , G 22 ). When each of the data groups (e.g., G 21 , G 22 ) includes an odd number (e.g., 3 or 5) of data channels (e.g., 230 _ 1 to 230 _ 4 ), the polarity determining unit (e.g., 220 _ 1 , 220 _ 2 ) inverses the polarities of the pixel voltages (e.g., VP 21 to VP 28 ) provided by a number close to a half of the data channels (e.g., 230 _ 1 to 230 _ 4 ) included in each one of the data groups (e.g., G 21 , G 22 ). For instance, when each of the data groups (e.g., G 21 , G 22 ) includes three data channels (e.g., 230 _ 1 to 230 _ 4 ), the polarity determining unit (e.g., 220 _ 1 , 220 _ 2 ) inverses the polarities of the pixel voltages (e.g., VP 21 to VP 28 ) provided by one or two (both are close to a half of three, i.e., 1.5) of the data channels (e.g., 230 _ 1 to 230 _ 4 ). When each of the data groups (e.g., G 21 , G 22 ) includes five data channels (e.g., 230 _ 1 to 230 _ 4 ), the polarity determining unit (e.g., 220 _ 1 , 220 _ 2 ) inverses the polarities of the pixel voltages (e.g., VP 21 to VP 28 ) provided by two or three (both are close to a half of five, i.e., 2.5) of the data channels (e.g., 230 _ 1 to 230 _ 4 ), and the rest may be deduced by analogy.

Moreover, when each of the data groups (e.g., G 21 , G 22 ) includes more than three data channels (e.g., 230 _ 1 to 230 _ 4 ), the polarity determining unit (e.g., 220 _ 1 , 220 _ 2 ) inverses the polarities of the pixel voltages (e.g., VP 21 to VP 28 ) provided by a part of the data channels (e.g., 230 _ 1 to 230 _ 4 ). For instance, when each of the data groups (e.g., G 21 , G 22 ) includes three data channels (e.g., 230 _ 1 to 230 _ 4 ), the polarity determining unit (e.g., 220 _ 1 , 220 _ 2 ) inverses the polarities of the pixel voltages (e.g., VP 21 to VP 28 ) provided by one or two of the data channels (e.g., 230 _ 1 to 230 _ 4 ). When each of the data groups (e.g., G 21 , G 22 ) includes four data channels (e.g., 230 _ 1 to 230 _ 4 ), the polarity determining unit (e.g., 220 _ 1 , 220 _ 2 ) inverses the polarities of the pixel voltages (e.g., VP 21 to VP 28 ) provided by one, two or three of the data channels (e.g., 230 _ 1 to 230 _ 4 ), and the rest may be deduced by analogy.

FIG. 3A is a schematic view illustrating a system of a source driver according to yet another embodiment of the invention. Referring to FIG. 2A and FIG. 3A , a source driver 300 is similar to the source driver 200 , and the same or similar elements are indicated by the same or similar reference numbers. In the present embodiment, a source driver 300 further includes a plurality of charge sharing units (e.g., 310 _ 1 , 310 _ 2 ), and the polarity determining units (e.g., 320 _ 1 , 320 _ 2 ) are coupled to the corresponding charge sharing unit (e.g., 310 _ 1 , 310 _ 2 ), respectively. The charge sharing unit (e.g., 310 _ 1 , 310 _ 2 ) are coupled to output terminals of the data channels (e.g., 230 _ 1 to 230 _ 4 ) corresponding to different data groups (e.g., G 21 , G 22 ). When the polarities of the pixel voltages (e.g., VP 21 to VP 28 ) provided by the coupled data channels (e.g., 230 _ 1 to 230 _ 4 ) are not inversed by each of the polarity determining units (e.g., 320 _ 1 , 320 _ 2 ), this indicates that the preset charging directions of the pixel voltages (e.g., VP 21 to VP 28 ) are not completely identical. Therefore, each of the polarity determining units (e.g., 320 _ 1 , 320 _ 2 ) can enable the corresponding charge sharing unit ( 310 _ 1 , 310 _ 2 ) so as to execute a charge sharing function.

FIG. 3B is a schematic view of waveforms of pixel voltages according to yet another embodiment of the invention. Referring to FIG. 2B , FIG. 3A and FIG. 3B , in which the same or similar elements are indicated by the same or similar reference numbers. In the present embodiment, it is illustrated with the data channels 230 _ 1 and 230 _ 2 of the data group G 21 as an example. A curve S 310 refers to a voltage variation of the pixel voltage VP 21 , for example. A curve S 320 refers to a voltage variation of the pixel voltage VP 22 , for example. Curves S 330 a and S 330 b refer to voltage variations of the pixel voltage VP 23 , for example. Curves S 340 a and S 340 b refer to voltage variations of the pixel voltage VP 24 , for example.

In the present embodiment, before the polarity inversion is performed, preset charging directions of the pixel voltages VP 21 to VP 24 at a time point T 1 are completely identical (refers to charging directions of the curves S 310 , S 320 , S 330 a and S 340 a at the time point T 1 ). Therefore, the polarity determining unit 220 _ 1 inverses the polarities of the pixel voltages VP 23 and VP 24 (i.e., the polarity of the pixel voltage VP 23 is inversed into negative, and the polarity of the pixel voltage VP 24 is inversed into positive), so that the charging directions of the pixel voltages VP 21 to VP 24 are not completely identical (refers to charging directions of the curves S 310 , S 320 , S 330 b and S 340 b at the time point T 1 ).

Subsequently, after the polarities of the pixel voltages VP 23 and VP 24 are inversed, the preset charging directions of the pixel voltages VP 11 and VP 12 are not completely identical (refers to charging directions of the curves S 310 , S 320 , S 330 b and S 340 b at time points T 2 and T 3 ), such that the polarity determining unit 220 _ 1 maintains the polarities of the pixel voltages VP 23 and VP 24 . In this case, the polarity determining unit 220 _ 1 can control the charge sharing unit 310 _ 1 to be enabled before the time points T 2 and T 3 (e.g., as shown at sharing time points CS 1 to CS 4 ), such that charging amplitudes of the pixel voltages VP 21 to VP 24 can be reduced through the charge sharing function. In an embodiment of the invention, the polarity determining unit 220 _ 1 can enable the charge sharing unit 310 _ 1 when the preset charging directions of the pixel voltages VP 21 to VP 24 are reversed to each other (i.e., the pixel voltages with upper charging direction is equal to the pixel voltages with lower charging direction), this can be set by the persons with ordinary skill in the art, and the embodiment of the invention is not limited thereto.

FIG. 3C is a schematic view illustrating a system of a source driver according to yet another embodiment of the invention. Referring to FIG. 3A and FIG. 3B , a source driver 400 is similar to the source driver 300 , and the same or similar elements are indicated by the same or similar reference numbers. In the present embodiment, the data channel 230 _ 1 includes latches LT 1 to LT 4 , exchanging units SWX 1 to SWX 2 , digital-to-analog converters ADC 1 to ADC 2 , buffers BF 1 to BF 2 and switches SW 1 to SW 2 . Circuit structure of the data channel 230 _ 2 can refer to the data channel 230 _ 1 , thus related description is omitted hereinafter.

An input terminal of the latch LT 1 is coupled to the data register unit 210 to receive the corresponding display data DS 21 , and an output terminal of the latch LT 1 is coupled to the corresponding polarity determining unit 320 _ 1 to provide the reference data DR 21 corresponding to the display data DS 21 received by each of the data channels 230 _ 1 . An input terminal of the latch LT 2 is coupled to the data register unit 210 to receive the corresponding display data DS 22 , and an output terminal of the latch LT 2 is coupled to the corresponding polarity determining unit 320 _ 1 to provide the reference data DR 22 corresponding to the display data DS 22 received by each of the data channels 230 _ 1 .

The exchanging unit SWX 1 has input terminals A 1 to A 2 , output terminals B 1 to B 2 , and receives the polarity control signal PC 21 provided by the polarity determining unit 320 _ 1 . The input terminal A 1 is coupled to the output terminal of the latch LT 1 ; the input terminal A 2 is coupled to the output terminal of the latch LT 2 ; the output terminal B 1 is coupled to an input terminal of the latch LT 3 ; and the output terminal B 2 is coupled to an input terminal of the latch LT 4 . According to the polarity control signal PC 21 , the exchanging unit SWX 1 controls the input terminals A 1 and A 2 to couple to the output terminals B 1 and B 2 , respectively, or controls the input terminals A 1 and A 2 to couple to the output terminals B 2 and B 1 , respectively.

The latch LT 3 receives the corresponding display data (e.g., DS 21 , DS 22 ), and an output terminal of the latch LT 3 is coupled to the corresponding polarity determining unit 320 _ 1 to provide the previous reference data DR 21 p or DR 22 p corresponding to the previous display data. The latch LT 4 receives the corresponding display data (e.g., DS 22 , DS 21 ), and an output terminal of the latch LT 4 is coupled to the corresponding polarity determining unit 320 _ 1 to provide the previous reference data DR 22 p or DR 21 p corresponding to the previous display data. An input terminal of the digital-to-analog converter ADC 1 being coupled to the output terminal of the latch LT 3 to receive the corresponding display data (e.g., DS 21 , DS 22 ) and provide the pixel voltages (e.g., VP 21 , VP 22 ) having a positive polarity (refers to a first polarity). An input terminal of the digital-to-analog converter ADC 2 being coupled to the output terminal of the latch LT 4 to receive the corresponding display data (e.g., DS 22 , DS 21 ) and provide the pixel voltages (e.g., VP 22 , VP 21 ) having a negative polarity (refers to a second polarity).

The exchanging unit SWX 2 has input terminals A 3 to A 4 , output terminals B 3 to B 4 , and receives the polarity control signal PC 21 provided by the polarity determining unit 320 _ 1 . The input terminal A 3 is coupled to an output terminal of the digital-to-analog converter ADC 1 . The input terminal A 4 is coupled to an output terminal of the digital-to-analog converter ADC 2 . The output terminal B 3 is coupled to an input terminal of the buffer BF 1 . The output terminal B 4 is coupled to an input terminal of the buffer BF 2 . According to the polarity control signal PC 21 , the exchanging unit SWX 2 controls the input terminals A 3 and A 4 to couple to the output terminals B 3 and B 4 , respectively, or controls the input terminals A 3 and A 4 to couple to the output terminals B 4 and B 3 , respectively.

The buffer BF 1 is configured to buffer the pixel voltage VP 21 . The buffer BF 2 is configured to buffer the pixel voltage VP 22 . The switch SW 1 is coupled to the buffer BF 1 and receives the latch signal LD, and outputs the pixel voltage VP 21 under control of the latch signal LD. The switch SW 2 is coupled to the buffer BF 2 and receives the latch signal LD, and outputs the pixel voltage VP 22 under control of the latch signal LD.

A charge sharing unit 310 a includes a plurality of charge sharing switches SWC 1 to SWC 3 respectively coupled between the output terminals of the data channels 230 _ 1 to 230 _ 2 (corresponding to the same data group G 21 ), and being simultaneously turned on or turned off under control of the corresponding polarity determining unit 320 _ 1 .

FIG. 4 is a flow chart illustrating a method for determining polarity of pixel voltage of source driver according to an embodiment of the invention. Referring to FIG. 4 , in the present embodiment, the method for determining polarity of pixel voltage of source driver includes the following steps. A plurality of display data are provided according to an image data signal (step S 410 ). A plurality of pixel voltages are provided according to the display data, in which the pixel voltages corresponds to a plurality of data groups, respectively, and each of the data groups at least corresponds to two of the pixel voltages (step S 420 ). A polarity of each of the pixel voltages is determined (step S 430 ). Whether to invert the polarities of a part of the pixel voltages corresponding to each of the data groups is determined according to the display data corresponding to the each of the data groups and a plurality of previous display data corresponding to the display data (step S 440 ). In which, a sequence of steps S 410 , S 420 , S 430 and S 440 is merely an example, the embodiments of the invention are not limited thereto. Further, detailed information regarding steps S 410 , S 420 , S 430 and S 440 may refer to the embodiments as illustrated in FIG. 1A , FIG. 1B , FIG. 2A , FIG. 2B , FIG. 3A , FIG. 3B and FIG. 3C , so related description is omitted hereinafter.

Based on above, in the source driver and a method for determining polarity of pixel voltage thereof, whether to invert the polarities of the part of the pixel voltages corresponding to each of the data groups is determined according to the display data corresponding to the each of the data groups and the previous display data corresponding to the display data. Accordingly, influences of charging the pixel voltages to the common voltage can be reduced. Moreover, the charge sharing function can be executed to the pixel voltages corresponding to each of the data groups when the polarities of the part of pixel voltages of each of the data groups are not inverted, such that charging amplitudes of the pixel voltages can be reduced.

It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present disclosure without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the present disclosure cover modifications and variations of this disclosure provided they fall within the scope of the following claims and their equivalents.