BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 depicts a well-known LUT used by source drivers for overdriving a LCD module:
FIG. 2 is a circuit diagram according to one embodiment of the present invention;
FIG. 3 is a circuit diagram according to another embodiment of the present invention:
FIG. 4 is a circuit diagram according to another embodiment of the present invention;
FIG. 5 illustrates the signal-waveforms of the embodiments shown in FIGS. 2, 3, and 4; and
FIG. 6 illustrates a flowchart according to another embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Some embodiments of the present invention will be described in greater details herein However, it should be noted that the present invention can be practiced in a wide range of other embodiments besides those explicitly described, and the scope of the present invention is expressly not limited except as specified in the accompanying claims.
Moreover, some details are not drawn in order to make the illustrations concise and to provide a clear description for easier understanding of the present invention.
Referring to FIG. 2, a circuit diagram according to one embodiment of the present invention 200 is illustrated. A first threshold detection logic 220 receives gray scale data from an overdriving timing controller 212 (also known as “TCON”) and a first predetermined gray scale value labeled “1st Threshold Value.” The first threshold detection logic 220 compares the gray scale data with the first predetermined gray scale value and then outputs a comparison result as a first control signal OD_Ctrl1. For example, the first threshold detection logic 220 outputs a first level signal, e.g., logic “1”, as the first control signal OD_Ctrl1 when the gray scale data is larger than the first predetermined gray scale value, otherwise it outputs a second level signal, e.g. logic “0”, as the first control signal OD_Ctrl1. For example, given 8-bit gray scale data, the first predetermined gray scale value could be set at gray scale value 240, and thus the first threshold detection logic 220 outputs logic “1” when the gray scale data is higher than 240. Alternatively, the first threshold detection logic 220 outputs the second level signal, such as logic “0”, as the first control signal OD_Ctrl1 when the gray scale data is smaller than the first predetermined gray scale value. With 8-bit gray scale data, the first predetermined gray scale value could be set at 16, and hence the first threshold detection logic 220 would output logic “0” when the gray scale data is smaller than 16. In these embodiments, the first predetermined gray scale value could be built-in or stored in the first threshold detection logic 220. The first threshold detection logic 220 could be a first comparator 222 and the first control signal OD_Ctrl1 can be used to control the final output data.
A second threshold detection logic 230 receives the same gray scale data, and receives a second and third predetermined gray scale values designated “2nd Threshold Value” and “3rd Threshold Value.” The second threshold detection logic 230 compares the gray scale data with the second and third predetermined gray scale values, and then outputs a second control signal OD_Ctrl2 according to the results of the comparisons. For example, the second threshold detection logic 230 outputs a second control signal OD_Ctrl2, such as logic “1”, when the gray scale data is larger than the second predetermined gray scale value or smaller than the third predetermined gray scale value, otherwise it outputs an inactive signal, such as logic “0”. For example, given 8-bit gray scale data, the second and the third predetermined gray scale values can be respectively set to 240 and 16, and therefore the second threshold detection logic 230 outputs logic “1” when the gray scale data is larger than 240 or is smaller than 16; in other words. the second threshold detection logic 230 outputs logic “0” when the gray scale data is between the values 16 and 240. The second threshold detection logic 230 includes a second comparator 232, a third comparator 234, and an OR gate 236. The second comparator 232 compares the gray scale data with the second predetermined gray scale value, and then outputs a first logical high signal (i.e., logic “1”) if the gray scale data is larger than the second predetermined gray scale value. The third comparator 234 compares the gray scale data with the third predetermined gray scale value, and then outputs a second logical high signal if the gray scale data is smaller than the third predetermined gray scale value. The OR gate 236 receives the outputs of the second and the third comparators 232, 234, executes a logical “OR” operation, and outputs the result as the second control signal OD_Ctrl2. In this embodiment, the second and the third predetermined gray scale values could be built-in or stored in the second threshold detection logic 230. And the second control signal OD_Ctrl2 can be used to control the final output data.
The selection logic 240 receives the gray scale data (via a source driver 214) and a plurality of gray scale compensation data, such as Vext_H(−), Vext_H(+), Vext_L(−), and Vext_L(+). The selection logic 240 uses the first and the second control signals OD_Ctrl1, OD_Ctrl2, and a third control signal POL, (polarization signal) as its selection signals for selecting one of received data to output as Vout. Herein, the third control signal POL is provided by the overdriving timing controller 212. The selection logic 240 includes a first multiplexer 242, a second multiplexer 244, and a third multiplexer 246. The first multiplexer 242 receives first and second gray scale compensation data, such as Vext_H(−) and Vext_H(+), and uses the third control signal POL as its selection signal. The second multiplexer 244 receives third and fourth gray scale compensation data, such as Vext13 L,(−) and Vext_L(+), and uses the third control signal POL as its selection signal. Accordingly, when the third control signal POL is logic “0”, the outputs of the first and the second multiplexers 242, 244 are Vext_H(−) and Vext_L(−), respectively; on the contrary, when the third control signal POL is logic “1”, the outputs of the first and the second multiplexers 242, 244 arc Vext_H(+) and Vext_L(+), respectively. The third multiplexer 246 receives the outputs of the first and the second multiplexers and the gray scale data, and uses the first and the second control signals OD_Ctrl1, OD_Ctrl2 as its selection signals, S0 and S1. Herein, the third multiplexer 246 outputs the gray scale data when OD_Ctrl2 and OD_Ctrl1 are logic “00” or “01”; if OD_Ctrl2 and OD_Ctrl1 are logic “10”, then the third multiplexer 246 outputs the output of the second multiplexer 244; and if OD_Ctrl2 and OD_Ctrl1 are logic “11”, then the third multiplexer 246 outputs the output of the first multiplexer 242. In this embodiment, the first multiplexer 242 and the second multiplexer 244 are 2×1 multiplexers, and the third multiplexer 246 is a 4×1 multiplexer. The first, second, third, and fourth gray scale compensation data, Vext_H(−), Vext_H(+), Vext_L(−) and Vext_L(+), can correspond to the gray scales driven at 0.1 volt (V), 13 V, 5 V, and 7 V, respectively, as default values.
FIG. 3 illustrates another embodiment of this present invention. The differences between FIG. 3 and FIG. 2 are the inputs of the first and second multiplexers 242, 244, and the selection signals of the first, second, and third multiplexers 246. The Vext_H(−) signal and the Vext_L(+) are exchanged, and the selection signals of the first and the second multiplexers 242, 244 are changed from POL to OD_Ctrl1. Also, the selection signals, S1 and S0, of the third multiplexer 246 are changed from OD_Ctrl2 and OD_Ctrl1 to OD_Ctrl2 and POL. Thus, the third multiplexer 246 outputs the gray scale data when OD_Ctrl2 and POL are logic “0038 or “01”; if OD_Ctrl2 and POL are logic “10”, then the third multiplexer 246 outputs the output of the second multiplexer 244; and if OD_Ctrl2 and POL are logic “11”, then the third multiplexer 246 outputs the output of the first multiplexer 242. As for other elements shown in FIG. 3, they have the same features and relations with each other as those described in FIG. 2.
FIG. 4 illustrates another embodiment of the present invention. The difference between FIG. 4 and FIG. 2 is the selection logic 240 which comprises an 8×1 multiplexer 248. The 8×1 multiplexer 248 receives the gray scale data and the plurality of gray scale compensation data, Vext_H(−), Vext_H(+), Vext_L(−), and Vext_L(+), and uses the OD_Ctrl2, OD_Ctrl1, and POL, as its selection signals, S2, S1, and S0, respectively. Herein, the selection logic 240 outputs the gray scale data when OD_Ctrl2 is logic “0”; the selection logic 240 outputs Vext_L(−) when OD_Ctrl2, OD_Ctrl1, and POL are logic “100”; the selection logic 240 outputs Vext_L(+) when OD_Ctrl2, OD_Ctrl1, and POL are logic “101”; the selection logic 240 outputs Vext_H(−) when OD_Ctrl2, OD_Ctrl1, and POL are logic “110”; and the selection logic 240 outputs Vext_H(+) when OD_Ctrl2, OD_Ctrl1, and POL are logic “111”. As for other elements shown in FIG. 4, they have the same features and relations to each other as those described in
Alternative embodiments of the present invention are possible. The first threshold detection logic 220 of FIGS. 2, 3 or 4 can be left out to simplify the circuit design and to lower the cost, and the original output of the first threshold detection logic 220 to the first control signal OD_Ctrl1 can be replaced by the output of the second comparator 232, i.e. the first control signal OD_Ctrl1 can be coupled to the output of the second comparator 232 (not shown). Alternatively, the second comparator 232 of FIGS. 2, 3 or 4 can be left out from the circuit design 200, 300 or 400, and the original output of the second comparator 232 to the “OR” gate 236 can be replaced by the output of the first threshold detection logic 220, i.e. the output of the first threshold detection logic 220 can be coupled to both the first control signal OD_Ctrl1 and the first input of the “OR” gate 236.
Referring to FIG. 5, the signal-waveforms of the embodiments shown in FIGS. 2, 3, and 4 are illustrated. In order to clarify the relationship of the signal-waveforms, the units of the vertical axes (in most cases, voltage) are not shown. The horizontal axis in FIG. 5 represents time. Moreover, it should be understood that the signal-waveforms in FIG. 5 are used to explain the relationships among the gray scale data, the gray scale compensation data, and the control signals. Specifically, the signal-waveforms illustrate when to use and how to select the gray scale compensation data. For example, 8-bit gray scale data (0-255) is used. Referring to FIGS. 2-5, the 1st, 2nd, and 3rd Threshold Values could be respectively set to the values 240, 240, and 16. The outputs of the selection logic 240 (labeled Output Status) are equal to the gray scale data (labeled 0) when the gray scale data is between 16 and 240, such as in T3 (the gray scale data is L100) and in T5 (the gray scale data is L200). Because the gray scale values between 16 and 240 do not need to be compensated for, the second control signal OD_Ctrl2 is logic “0” and therefore the selection logic 240 outputs the gray scale data, regardless of the values of the first and third control signals OD_Ctrl1 and POL.
When the gray scale data is larger than 240, such as in T1 (the gray scale data is L255), both OD_Ctrl2 and OD_Ctrl1 are logic “1”, and therefore the Output Status depends upon the POL. The Output Status is equal to the first gray scale compensation data (labeled 1) once the POL is logic “0”. The Output Status is equal to the second gray scale compensation data (labeled 2) when the POL is logic “1”. Similarly, in T4 (the gray scale data is L245), the Output Status is equal to the first gray scale compensation data (labeled 1) when OD_Ctrl2, OD_Ctrl1, and POL are logic “110”,and the Output Status is equal to the second gray scale compensation data (labeled 2) when OD_Ctrl2, OD_Ctrl1, and POL are logic “111”. When the gray scale data is smaller than 16, such as in T2 (the gray scale data is L0), OD_Ctrl2 is logic “1” and OD_Ctrl1 is logic “0”. Thus, the Output Status depends upon the POL. The Output Status is equal to the third gray scale compensation data (labeled 3) when the POL, is logic “0”, and the Output Status is equal to the fourth gray scale compensation data (labeled 4) when the POL is logic “1”. In this embodiment, the first (Vext_H(−)), second (Vext_H(+)), third (Vext_L(−)), and fourth (Vext_L(+)) gray scale compensation data can have the default values of the gray scale values driven at 0.1 volt (V), 13 V, 5 V, and 7 V, respectively.
FIG. 6 is a flowchart illustrating another embodiment of the present invention. In step 610, the system receives gray scale data from an overdriving timing controller. In step 620, the system compares the gray scale data with a first predetermined gray scale value, and then outputs a first control signal. Herein the first control signal is set to be a first level signal when the gray scale data is larger than the first predetermined gray scale value, or is set to be a second level signal otherwise. For example, given 8-bit gray scale data (0-255), the first predetermined gray scale value could be set to 240, and thus the first level signal would be outputted if the gray scale data is larger than 240. In step 630, the system compares the gray scale data to the second and third predetermined gray scale values, and then outputs a second control signal. Herein the second control signal is set to logical high if the gray scale data is larger than the second predetermined gray scale value or if the gray scale data is smaller than the third predetermined gray scale value. Otherwise, the second control signal is set to logical low. It will be apparent to those skilled in the art that steps 620 and 630 can be executed simultaneously or combined as one step. When the second control signal is at logical low, step 640 is executed. In step 640, the system outputs the gray scale data received via a source driver. In step 650, a first gray scale compensation data is outputted if the second control signal is at logical high, the first control signal is the first level signal and a third control signal received from the overdriving timing controller is logic “0”. In step 660, a second gray scale compensation data is outputted if the second control signal is at logical high, the first control signal is the first level signal and the third control signal is logic “1” In step 670, a third gray scale compensation data is outputted if the second control signal is at logical high, the first control signal is the second level signal and the third control signal is logic “0”. In step 680, a fourth gray scale compensation data is outputted if the second control signal is at logical high, the first control signal is the second level signal and the third control signal is logic “1”. For example, the first, second, and third predetermined gray scale values could be 240, 240, and 16, respectively. The first, second, third, and fourth gray scale compensation data could be set to default values such as the gray scale values driven by 0.1V, 13V, 5V, and 7 V, respectively.
In accordance with the alternative embodiments of the present invention, either the first or the second predetermined gray scale value can be left out from the circuit design but the steps of generating the first and second control signals (OD_Ctrl1 and OD_Ctrl2, respectively) remain the same. Such embodiments would require corresponding modifications to FIGS. 5 and 6.
The various signals of the present invention are generally “on” (e.g., a logical HIGH, or 1) or “off” (e.g., a logical LOW, or 0). However, the particular polarities of the “on” (e.g., asserted) and “off” (e.g., de-asserted) states of the signals may be adjusted (e.g., reversed) accordingly to meet the design criteria of a particular implementation. Additionally, inverters may be added to change particular polarities of the signals.
Although specific embodiments have been illustrated and described, it will be obvious to those skilled in the art that various modifications may be made without departing from what at is covered by the appended claims.
Patent Application
20080002912
