Patent Grant
8810483
The present application is also related to the following pending U.S. patent Applications: Ser. No. 11/426,162 titled “ACTIVE MATRIX DISPLAYS HAVING ENABLING LINES”; Ser. No. 11/426,171 titled “METHOD OF DRIVING ACTIVE MATRIX DISPLAYS HAVING NONLINEAR ELEMENTS IN PIXEL ELEMENTS”; and Ser. No. 11/426,177, titled “ACTIVE MATRIX DISPLAYS HAVING NONLINEAR ELEMENTS IN PIXEL ELEMENTS,” All of the applications cited above as originally filed are hereby incorporated by reference herein in their entirety.
The present invention relates generally to active matrix displays, and more particularly to active matrix displays having nonlinear elements in pixel elements.
In operation, during a predetermined time period, a row of pixel elements (e.g., 50AA-50AC) is selected for charging by applying a selection signal on a row conducting line (e.g., 40A). During the next predetermined time period, next row of pixel elements (e.g., 50BA-50BC) is selected for charging by applying a selection signal on the next row conducting line (e.g., 40B).
When charging a row of pixel elements (e.g., 50AA-50AC), each pixel element is charged with a data signal on a column conducting line. For example, the pixel elements 50AA, 50AB, and 50AC are charged respectively with the column conducting lines 30A, 30B, and 30C. When charging the next row of pixel elements (e.g., 50BA-50BC), each pixel element in this next row is also charged with a data signal on a column conducting line. For example, the pixel elements 50BA, 50BB, and 50BC are charged respectively with the column conducting lines 30A, 30B, and 30C.
During the predetermined time period for charging a row of pixel elements, the switching transistors in the pixel elements needs to be fast enough to change their conducting states. A switching transistor may need to change from the non-conducting state to the conducting state or change from the conducting state to the non-conducting state. When an active matrix display has a total of N rows, if the time period for charging all N rows of pixel elements progressively is a frame time period T0, the allocated predetermined time period for charging one row of pixel elements can be less than T0/N. For high resolution displays in which N is quite large (e.g, N is larger or equal to 512), the allocated predetermined time period can become quite short such that it put on stringent demand on the switching speed of the switching transistors. For lowering the manufacturing cost, it is desirable to reduce the switching speed requirement for the switching transistors by finding new forms of active matrix displays and by finding new method for driving these active matrix displays. Also, it is desirable to improve the display quality of those active matrix displays that use nonlinear elements, such as thin film diodes (TFD) or metal-insulator-metal diodes, as the switching elements for pixel elements.
In one aspect, the invention is directed to a method of driving a pixel element in an active matrix display. The active matrix display includes a matrix of pixel elements wherein a pixel element includes (a) at least one switching transistor having a semiconductor channel, (b) at least one nonlinear element, and (c) at least one capacitive element. The method comprises: (1) driving the semiconductor channel of the at least one switching transistor into a conducting state from a non-conducting state, and maintaining the semiconductor channel of the at least one switching transistor at the conducting state for a first time duration; (2) driving the at least one nonlinear element into a conducting state from a non-conducting state, and maintaining the at least one nonlinear element at the conducting state for a second time duration that is within the first time duration; (3) changing a voltage across the at least one capacitive element while the semiconductor channel of the at least one switching transistor maintains at the conducting state and the at least one nonlinear element maintains at the conducting state; (4) driving the at least one nonlinear element into the non-conducting state from the conducting state, and maintaining the at least one nonlinear element at the non-conducting state for a third time duration that is after the second time duration; and (5) driving the semiconductor channel of the at least one switching transistor into the non-conducting state from the conducting state, and maintaining the semiconductor channel of the at least one switching transistor at the nonconducting state for a fourth time duration that is after the first time duration. The first time duration is at least three times as long as the second time duration.
Implementations of the invention can include one or more of the following features. The method can further comprise maintaining the voltage across the at least one capacitive element during a time period lasting from the beginning of the third time duration to the beginning of the fourth time duration. The method can further comprise maintaining the voltage across the at least one capacitive dement during the fourth time duration.
Implementations of the invention can also include one or more of the following features. In the method, said changing a voltage across the at least one capacitive element can comprise: creating a current that passes through both the semiconductor channel of the at least one switching transistor and the at least one nonlinear element to transmit electrical charges to the at least one capacitive element, while the semiconductor channel of the at least one switching transistor maintains at the conducting state and the at least one nonlinear element maintains at the conducting state. In the method, said creating a current that passes through both the semiconductor channel of the at least one switching transistor and the at least one nonlinear element can comprise: applying a predetermined current to a column conducting line connecting to the pixel element. In the method, said creating a current that passes through both the semiconductor channel of the at least one switching transistor and the at least one nonlinear element can comprise: applying a predetermined voltage to a column conducting tine connecting to the pixel element.
Implementations of the invention can also include one or more of the following features. The first time duration can be at least four times as long as the second time duration, at least eight times as long as the second time duration, or at least sixteen times as long as the second time duration. A pixel element can include a linear switch that comprises (a) a nonlinear element and (b) a switching transistor having a semiconductor channel serially connected to the nonlinear element.
In another aspect, the invention is directed to a method applied on an active matrix display. The active matrix display comprises (a) a matrix of the pixel elements, (b) array of column conducting lines, and (c) an array of row conducting lines crossing the array of column conducting lines. In the active matrix display, a column of pixel elements includes at least M pixel elements each connected to a column conducting line. The integer M is larger than or equal to three (M≧3). Each of the M pixel elements includes (a) at least one switching transistor having a semiconductor channel, (b) at least one nonlinear element, and (c) at least one capacitive element. The method comprises: selecting each given pixel element in the M pixel elements for charging the given pixel element consecutively with a corresponding pixel data applied to said column conducting line during an allocated time period for the given pixel element while the semiconductor channel of the at least one switching transistor in the given pixel element maintains at the conducting state and the at least one nonlinear element in the given pixel element maintains at the conducting state.
In the method, said selecting each given pixel element in the M pixel elements for charging the given pixel element consecutively comprises, (1) driving the semiconductor channel of the at least one switching transistor in the given pixel element into the conducting state from the nonconducting state, and maintaining the semiconductor channel of the at least one switching transistor in the given pixel element at the conducting state for duration of an associated time period for the given pixel element, and (2) driving the at least one nonlinear element in the given pixel element into the conducting state from the non-conducting state, and maintaining the at least one nonlinear element in the given pixel element at the conducting state for a duration of the allocated time period for the given pixel element that is within the associated time period for the given pixel element. In the method, the associated time period for at least one pixel element is more than three times longer than the allocated time period for said at least one pixel element. In the method, at least one of the associated time periods overlaps with at least two other associated time periods.
Implementations of the invention can include one or more of the following features. In the method, the integer M can be larger than or equal to four (M≧4), and wherein at least one of the associated time periods overlaps with at least seven other associated time periods. In the method, the integer M can be larger than or equal to eight (M≧8), and wherein at least one of the associated time periods overlaps with at least seven other associated time periods. In the method, the integer M can be larger than or equal to sixteen (M≧16), and wherein at least one of the associated time periods overlaps with at least seven other associated time periods.
Implementations of the invention can also include one or more of the following features. In the method, at least three associated time periods can be all beginning substantially at the same time and all ending substantially at the same time. In the method, at least one of the associated time period can overlap with at least two other associated time periods under the condition that the beginnings of said at least two other associated time periods is sequentially delayed from the beginning of said at least one of the associated time periods. In the method, each of the M pixel elements can include a linear switch that comprises (a) a nonlinear element and (b) a switching transistor having a semiconductor channel serially connected to the nonlinear element.
In another aspect, the invention is directed to a method applied on an active matrix display having a matrix of the pixel elements. In the active matrix display, a column of pixel elements includes at least M pixel elements, the integer M being larger than or equal to three (M≧3). Each of the M pixel elements includes (a) at least one switching transistor having a semiconductor channel, (b) at least one nonlinear element, and (c) at least one capacitive element. The method comprises: for each positive integer k that is smaller than or equal to the integer M (1≦k≦M), selecting the k'th pixel element in the M pixel elements for charging the k'th pixel element with a corresponding pixel data applied to the k'th pixel element during an allocated time period for the k'th pixel element while the semiconductor channel of the at least one switching transistor in the k'th pixel element maintains at the conducting state and the at least one nonlinear element in the k'th pixel element maintains at the conducting state. In the method, for each k that is smaller than the integer M (k<M), the end of the allocated time period for the (k+1)'th pixel element is after the end of the allocated time period for the k'th pixel element.
In the method, said selecting the k'th pixel element in the M pixel elements for charging the k'th pixel element comprises, (1) driving the semiconductor channel of the at least one switching transistor in the k'th pixel element into the conducting state from the non-conducting state, and maintaining the semiconductor channel of the at least one switching transistor in the k'th pixel element at the conducting state for duration of an associated time period for the k'th pixel element, and (2) driving the at least one nonlinear element in the k'th pixel element into the conducting state from the non-conducting state, and maintaining the at least one nonlinear element in the k'th pixel element at the conducting state for a duration of the allocated time period for the k'th pixel element that is within the associated time period for the k'th pixel element. In the method, the associated time period for at least one of the M pixel elements is more than three times longer than the allocated time period for said one of the M pixel elements. In the method, at least one of the associated time periods overlaps with at least two other associated time periods.
Implementations of the invention can include one or more of the following features. In the method, the integer M can be larger than or equal to four (M≧4), and wherein at least one of the associated time periods overlaps with at least seven other associated time periods. In the method, the integer M can he larger than or equal to eight (M≧8), and wherein at least one of the associated time periods overlaps with at least seven other associated time periods. In the method, the integer M can be larger than or equal to sixteen (M≧16), and wherein at least one of the associated time periods overlaps with at least seven other associated time periods.
Implementations of the invention can also include one or more of the following features. In the method, for each k that is smaller than the integer M (k<M), the allocated time period for the (k+1)'th pixel element can be after the allocated time period for the k'th pixel element. In the method, for each k that is smaller than the integer M (k<M), the end of the allocated time period for the (k+1)'th pixel element can be delayed from the end of the allocated time period for the k'th pixel element with a same delay.
Implementations of the invention can also include one or more of the following features. In the method, for each k that is smaller than M+1, the associated time period for the k'th pixel element can be at least M times as long as the allocated time period for the k'th pixel element. In the method, the associated time period for the first of the M pixel elements can overlap with the associated time periods of the remaining M−1 pixel element. In the method, the associated time periods tor the M pixel elements can be all beginning substantially at the same time and all ending substantially at the same time. In the method, for each k that is smaller than the integer M (k<M), the beginning of the associated time period for the (k+1)'th pixel element can be delayed from the beginning of the associated time period for the k'th pixel element, with the associated time period for the (k+1)'th pixel element overlapping with the associated time period for the k'th pixel element. In one implementation, for each k that is smaller than the integer M (k<M), the beginning of the associated time period for the (k+1)'th pixel element is delayed from the beginning of the associated time period for the k'th pixel element with a same delay constant.
In another aspect, the invention is directed to a method of driving a pixel element in an active matrix display. The active matrix display includes a matrix of pixel elements wherein a pixel element includes at least one switching transistor having a semiconductor channel, at least one nonlinear element, and at least one capacitive element. The nonlinear element in the pixel element comprises a supplementary resistor serially connected to one of a PN diode and a PIN diode. The method comprises: (1) driving the semiconductor channel of the at least one switching transistor into a conducting state from a non-conducting state, and maintaining the semiconductor channel of the at least one switching transistor at the conducting state during a first time period; (2) driving the at least one nonlinear element into a conducting state from a non-conducting state, and maintaining the at least one nonlinear element at the conducting state during a second time period that is within the first time period; (3) charging the at least one capacitive element through the semiconductor channel of the at least one switching transistor and through the at least one nonlinear element while the semiconductor channel of the at least one switching transistor maintains at the conducting state and the at least one nonlinear element maintains at the conducting state; (4) driving the at least one nonlinear element into the non-conducting state from the conducting state, and maintaining the at least one nonlinear element at the non-conducting state during a third time period that is after the second time period; (5) driving the semiconductor channel of the at least one switching transistor into the non-conducting state from the conducting state, and maintaining the semiconductor channel of the at least one switching transistor at the non-conducting state during a fourth time period that is after the first time period, wherein the fourth time period is at least two times as long as the first time period. With this method, said charging the at least one capacitive element comprises applying a predetermined voltage to the at least one capacitive element through the at least one nonlinear element in the selected pixel element.
In another aspect, the invention is directed to a pixel element in an active matrix display. The active matrix display comprises (a) matrix of the pixel elements, (b) an array of column conducting lines, (c) an array of row conducting lines crossing the array of column conducting lines, and (d) an array of enabling lines crossing the array of column conducting lines. The pixel element is directly connected to (a) at least a row conducting line, (b) at least a column conducting line, and (c) at feast an enabling line. The pixel element comprises (a) a resistive element having a first terminal and a second terminal, (b) a capacitive element having a first terminal and a second terminal, (c) a nonlinear element having a first terminal and a second terminal, the nonlinear element being functionally a nonlinear diode, and (d) a switching transistor having a gate and a semiconductor channel. The nonlinear element in the pixel element comprises a supplementary resistor serially connected to one of a PN diode and a PIN diode. Within the pixel element, (1) the nonlinear element and the semiconductor channel of the switching transistor are electrically connected in serial between the column conducting line and the first terminal of the capacitive element, (2) the nonlinear element and the resistive element are electrically connected in serial between the column conducting line and the row conducting line, (3) the gate of switching transistor is configured to receive an electric signal from the enabling line, (4) the nonlinear element is electrically connected between the column conducting line and the second terminal of the resistive element, and (5) the resistive element is electrically connected between the row conducting line and the second terminal of the nonlinear element.
Implementations of the invention may include one or more of the following advantages. The implementations may reduce the manufacturing dependence on switching transistors in the active matrix display and may consequently lower the manufacturing cost. Additional advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention may be realized by means of the instrumentalities and combinations particularly pointed out in the claims.
The present invention will be understood more fully from the detailed description and accompanying drawings of the invention set forth herein. However, the drawings are not to be construed as limiting the invention to the specific embodiments shown and described herein. Like reference numbers are designated in the various drawings to indicate like elements.
The section of the active matrix display in
The section of the active matrix display in
The section of the active matrix display in
In
In
In
In
During the first predetermined time period T1, the switching transistors 52 in the enabled pixel elements 50AA-50AC, 50BA-50BC, 50CA-50CC, and 50DA-50DC are in the conducting state. The first predetermined time period T1 is further divided into four sub-time-periods T1(1), T1(2), T1(3), and T1(4). In one implementation, each of the four sub-time-periods has a duration that is one fourth of the duration of T1. During sub-time-periods T1(1), a first row of pixel elements 50AA-50AC is selected as the selected pixel elements for charging. During sub-time-periods T1(2), a second row of pixel elements 50BA-50BC is selected for charging. During sub-time-periods T1(3), a third row of pixel elements 50CA-50CC is selected for charging. During sub-time-periods T1(4), a fourth row of pixel elements 50DA-50DC is selected for charging.
During sub-time-periods T1(1), a selection voltage Von is applied to the row conducting line 40A to provide a forward biasing voltage for the nonlinear elements in the selected pixel elements 50AA-50AC and these nonlinear elements are driven into the conducting state. Deselect voltages are applied to the row conducting lines 40B-40L to provide reverse biasing voltages for the nonlinear elements in the non-selected pixel elements (i.e., 50BA-50BC, 50CA-50CC, . . . and 50LA-50LC) and these non-selected pixel elements are maintained at the non-conducting state. During sub-time-periods T1(1), the capacitive elements 54 in the selected pixel elements 50AA, 50AB, and 50AC are charged respectively with data drivers 70A, 70B, and 70C.
When the data driver 70A applies a predetermined current Id(AA) to the column conducting line 30A, most of this current passes through the nonlinear element 51 in the pixel element 50AA, because only the nonlinear element 51 in the pixel element 50AA is forward biased and the nonlinear elements in other pixel elements that connected to the column conducting line 30A are reverse biased. In the case that the sum of the leakage currents in these reverse biased nonlinear elements is significantly small, the predetermined current Id(AA) from the data driver 70A essentially all passes through the nonlinear element 51 in the pixel element 50AA. If voltage drops on the row conducting line 40A can be neglected, the voltage applied to the first terminal of the capacitive element 54 in the pixel element 50AA is now of the value Von+R0Id(AA), and the capacitive element 54 can now be charged to a targeted voltage. Here, R0 is the resistance of the resistive element 55. Similarly, when the data driver 70B applies a predetermined current Id(AB) to the column conducting line 30B, a voltage of the value Von+R0Id(AB) can be applied to the first terminal of the capacitive element 54 in the pixel element 50AB. When the data driver 70C applies a predetermined current Id(AC) to the column conducting line 30C, a voltage of the value Von+R0Id(AC) can be applied to the first terminal of the capacitive element 54 in the pixel element 50AC. In the above, it is assumed that the leakage currents in the reverse biased nonlinear elements can be neglected and the voltage drops on the row conducting lines can be neglected.
During sub-time-periods T1(2), a selection voltage Von is applied to the row conducting line 40B to provide a forward biasing voltage for the nonlinear elements in the selected pixel elements 50BA-50BC. Deselect voltages are applied to the row conducting lines 40A and 40C-40L to provide reverse biasing voltages for the nonlinear elements in the non-selected pixel elements (i.e., 50AA-50AC, 50CA-50CC, . . . , and 50LA-50LC). During sub-time-periods T1(2), the capacitive elements 54 in the selected pixel elements 50BA, 50BB, and 50BC are charged respectively with data drivers 70A, 70B, and 70C.
During sub-time-periods T1(3), a selection voltage Von is applied to the row conducting line 40C to provide a forward biasing voltage for the nonlinear elements in the selected pixel elements 50CA-50CC. Deselect voltages are applied to the row conducting lines 40A-40B and 40D-40L to provide reverse biasing voltages for the nonlinear elements in the non-selected pixel elements (i.e.. 50AA-50AC, 50BA-50BC, 50DA-50DC, . . . , and 50LA-50LC). During sub-time-periods T1(3), the capacitive elements 54 in the selected pixel elements 50CA, 50CB, and 50CC are charged respectively with data drivers 70A, 70B, and 70C.
During sub-time-periods T1(4), a selection voltage Von is applied to the row conducting line 40D to provide a forward biasing voltage for the nonlinear elements in the selected pixel elements 50DA-50DC. Deselect voltages are applied to the row conducting lines 40A-40C and 40E-40L to provide reverse biasing voltages for the nonlinear elements in the non-selected pixel elements (i.e., 50AA-50AC, 50BA-50BC, 50CA-50CC, 50EA-50EC, . . . , and 50LA-50LC). During sub-time-periods T1(4), the capacitive elements 54 in the selected pixel elements 50DA, 50DB, and 50DC are charged respectively with data drivers 70A, 70B, and 70C.
At the end of sub-time-period T1(4) (i.e., the end of T1), a disabling signal is applied to the first group of multiple rows of pixel elements (including pixel elements 50AA-50AC, 50BA-50BC, 50CA-50CC, and 50DA-50DC) and the switching transistors 52 in these pixel elements are changed to the non-conducting state; consequently, the voltages on the capacitive elements 54 in these pixel elements can then be maintained.
With similar operation principle, during the second predetermined time period T2, the second group of multiple rows of pixel elements (including pixel elements 50EA-50EC, 50FA-50FC, 50GA-50GC, and 50HA-50HC) are charged. During the third predetermined time period T3, the third group of multiple rows of pixel elements (including pixel elements 501A-50IC, 50JA-50JC, 50KA-50KC, and 50LA-50LC) are charged.
In operation, during sub-time-periods T1, the switching transistor 52 in the pixel element 50AB is in the conducting state because the first group of multiple rows of pixel elements (including pixel elements 50AA-50AC, 50BA-50BC, 50CA-50CC, and 50DA-50DC) are the enabled pixel elements. During sub-time-periods T1(1), the nonlinear elements 51 in pixel elements 50AA-50AC are also in the conducting state because pixel elements 50AA-50AC are the selected pixel elements and the nonlinear element 51 in the selected pixel elements is forward biased.
During sub-time-periods T1(1), when the data driver 70B applies a predetermined current Id(AB) to the column conducting line 30B, the voltage across the capacitive element 54 in the pixel element 50AB will be of the value R0Id(AB), if it is assumed that the total leakage current by other nonlinear elements that are connected to the column conducting line 30B can be reasonably neglected. The voltage across the capacitive element 54 in the pixel element 50AB can be charged to the value R0Id(AB) even there are voltage drops on the row conducting line 40A. This voltage across the capacitive element 54 in the pixel element 50AB can be determined by the predetermined current Id(AB) that is applied to the column conducting line 30B from the data driver 70B.
Similarly, during sub-time-periods T1(1), when the data driver 70A applies a predetermined current Id(AA) to the column conducting line 30A, the voltage across the capacitive element 54 in the pixel element 50AA can be charged to a predetermined value R0Id(AA). When the data driver 70C applies a predetermined current Id(AC) to the column conducting line 30C, the voltage across the capacitive element 54 in the pixel element 50AC can be charged to a predetermined value R0Id(AC).
In the implementations as shown in
In operation, during the first predetermined time period T1, when an enabling signal is applied to the enabling line 60A, the first group of multiple rows of pixel elements (including pixel elements 50AA-50AC, 50BA-50BC, 50CA-50CC, and 50DA-50DC) are enabled as the enabled pixel elements, and the switching transistors 52 and the secondary switching transistors 53 in these enabled pixel elements are in the conducting state. During sub-time-periods T1(1), a selection voltage Von is applied to the row conducting line 40A to drive the nonlinear element 51 in pixel elements 50AA-50AC into the conducting state.
During sub-time-periods T1(1), when the data driver 70B applies a predetermined current Id(AB) to the column conducting line 30B, only the leakage currents by the nonlinear elements in the enabled pixel elements 50BB, 50CB, and 50DB can influence the current passing through the nonlinear element 51 in the selected pixel element 50AB, because the non-enabled pixel elements are essentially isolated from the column conducting line 30B by the secondary switching transistors 53 in the non-enabled pixel elements. If the total leakage current by the nonlinear elements in the enabled pixel elements 50BB, 50CB, and 50DB can be reasonably neglected, the predetermined current Id(AB) as supplied by the data driver 70B will essentially all pass through the nonlinear element 51 in the pixel element 50AB.
In
In
In the previously described implementations for driving active matrix displays (e.g., as shown in
In those implementations where the data driver 70B applies a predetermined voltage to the column conducting line (e.g., 30B) for charging the capacitive element 54 in a pixel element (e.g., 50AB), if the nonlinear element 51 is a PN diode or a PIN diode, the uniformity variations of the voltage applied to the capacitive element 54 caused by uniformity variations of the nonlinear element 51 can be reduced by using a supplementary resistor serially connected to a PN diode or a PIN diode.
As an example,
In operation, during a first predetermined time period T1, a first row of pixel elements 50AA-50AC is selected as the selected pixels for charging. During a second predetermined time period T2, a second row of pixel elements 50BA-50BC is selected for charging. During a third predetermined time period T3, a third row of pixel elements 50CA-50CC is selected for charging.
During the first predetermined time period T1, a selection voltage Von is applied to the row conducting line 40A to provide a forward biasing voltage for the nonlinear elements in the selected pixel elements 50AA-50AC and these nonlinear elements are driven into the conducting state. Deselect voltages are applied to the row conducting lines 40B and 40C to provide reverse biasing voltages for the nonlinear elements in the non-selected pixel elements (i.e., 50BA-50BC and 50CA-50CC) and these non-selected pixel elements are maintained at the non-conducting state. During the first predetermined time period T1, the capacitive elements 54 in the selected pixel elements 50AA, 50AB, and 50AC are charged respectively with data drivers 70A, 70B, and 70C.
For charging the selected pixel element 50AB, the data driver 70B applies a predetermined current Id(AB) to the column conducting line 30B. If the total leakage current by the nonlinear elements in the non-selected pixel elements (i.e., 50BB and 50CB) can be reasonably neglected, the voltage across the capacitive element 54 in the pixel element 50AB can be charged to the value R0Id(AB) even there are voltage drops on the row conducting line 40A.
Similarly, for charging the selected pixel element 50AA, the data driver 70A applies a predetermined current Id(AA) to the column conducting line 30A, the voltage across the capacitive element 54 in the pixel element 50AA can be charged to a predetermined value R0Id(AA). For charging the selected pixel element 50AC, the data driver 70C applies a predetermined current Id(AC) to the column conducting line 30C, the voltage across the capacitive element 54 in the pixel element 50AC can be charged to a predetermined value R0Id(AC).
After the capacitive element 54 in a pixel element (e.g., 50AB) is charged to a target value, the nonlinear element 51 in the pixel element (e.g., 50AB) is driven into a non-conducting state and the voltage across the capacitive element 54 in the pixel element (e.g., 50AB) may change with time. Such voltage change over time, however, can follow a well defined function of time that essentially depends on some design parameters of the pixel element. When the voltage across the capacitive element 54 follows a well defined function of time, the total luminosity of a pixel element during a frame time period can be determined by the initial voltage across the capacitive element 54.
With similar operation principle, during the second predetermined time period T2, when predetermined currents Id(BA), Id(BB), and Id(BC) are respectively applied to the column conducting lines 30A, 30B, and 30C, the capacitive element 54 in the pixel elements 50BA, 50BB, and 50BC can be respectively charged to the voltages of the values R0Id(BA), R0Id(BB), and R0Id(BC). During the third predetermined time period T3, when predetermined currents Id(CA), Id(CB), and Id(CC) are respectively applied to the column conducting lines 30A, 30B, and 30C, the capacitive element 54 in the pixel elements 50CA, 50CB, and 50CC can be respectively charged to the voltages of the values R0Id(CA), R0Id(CB), and R0Id(CC).
In operation, for charging the pixel element 50AB, if a predetermined current Id(AB) passes through both the nonlinear element 51 and the resistive element 55 and if a selection voltage Von is applied to the first terminal of the resistive element 55, then, the voltage at the second terminal of the resistive element 55 can become Von+R0Id(AB). If a supplementary voltage is applied to the supplementary row conducting line 80A such that the second terminal of the capacitive element 54 is set at a voltage of the value Vsupp
In operation, for charging the pixel element 50AB, the nonlinear element 51 in the pixel element 50AB is drive into a conducting state. Both the first nonlinear element 59p and the second nonlinear element 59q of the nonlinear element complex in the pixel element 50AB are also drive into a conducting state. For charging the pixel element 50AB, if a predetermined current Id(AB) passes through both the nonlinear element 51 and the resistive element 55 and if a selection voltage Von is applied to the first terminal of the resistive element 55, then, the voltage at the second terminal of the resistive element 55 can become Von+R0Id(AB). If the voltage at the mid-terminal of the nonlinear element complex is Vmid, then, the capacitive element 54 can be changed to a voltage of the value Von+R0Id(AB)−Vmid. After the capacitive element 54 is charged to a target value, the nonlinear element 51 is driven into a non-conducting state; both the first nonlinear element 59p and the second nonlinear element 59q of the nonlinear element complex are also driven into non-conducting states. After the pixel element 50AB is changed to a non-selected pixel element, the voltage across the capacitive element 54 in the pixel element 50AB can be essentially maintained if leakage currents through the first nonlinear element 59p and the second nonlinear element 59q in the pixel element 50AB can be neglected.
In
In the implementations of active matrix displays as described previously, an active matrix display that has nonlinear elements in pixel elements generally can be driven by data drivers configured to supply predetermined currents to column conducting lines. In one implementation, a data driver can include a current source having certain compliance voltage. The current source can supply a constant current to a column conducting line when the voltage on that column conducting line is less than the compliance voltage. In another implementation, for supplying a predetermined current to a column conducting, a voltage can be applied to the column conducting line through a high impedance element. The value of the predetermined current can be changed either by changing the value of the voltage applied to the column conducting line or by changing the value of the high impedance element.
The data driver 70A includes a current sensing resistor 210, an instrumentation amplifier 220, a first sample-and-hold circuit 230, a switch circuit 240, a second sample- and-hold circuit 270, a first differential amplifier 280, and a second differential amplifier 290. The current sensing resistor 210 has a resistive value Rs. The data driver 70A also includes a data input 201, a data output 209, a switch control input 204, a first circuit-mode input 203 for setting the first sample-and-hold circuit 230 into either the sample mode or the hold mode, and a second circuit-mode input 207 for setting the second sample-and-hold circuit 270 into either the sample mode or the hold mode.
In operation, during a first time period TS, the second sample-and-hold circuit 270 is set to the sampling mode. A signal is applied to the switch control input 204 to enable the switch circuit 240 to connect the inverting input of the first differential amplifier 280 to a zero voltage. During the first time period TS, the current sensing resistor 210, the instrumentation amplifier 220, the second sample-and-hold circuit 270, the first differential amplifier 280, and the second differential amplifier 290 can complete a negative feedback loop. When a data voltage V(AA) is applied to the data input 201 of the data driver 70A after the pixel element 50AA is selected as the selected element, a predetermined current of the value Id(AA)=V(AA)/RsGv is applied to the column conducting line 30A. Here, Gv is the voltage gain of the second differential amplifier 290. This predetermined current may not completely pass through the nonlinear element 51 in the selected pixel element 50AA if there are significant amount of leakage currents by the nonlinear elements in the non-selected pixel elements (e.g., 50BA, 50CA, . . . ).
To measure the total amount of the leakage currents, during a second time period TM, the first sample-and-hold circuit 230 is set to the sampling mode while the second sample-and-hold circuit 270 is set to the holding mode. During the second time period TM, the output voltage of the second differential amplifier 290 is essentially held at a constant voltage. At the end of the second time period TM, when the pixel element 50AA is also changed to a non-selected pixel element along with the other non-selected pixel elements (e.g., 50BA, 50CA, . . . ), the total leakage current Ileak by the nonlinear elements in all non-selected pixel elements can be measured by measuring a voltage across the current sensing resistor 210. After this measurement, if the first sample-and-hold circuit 230 is changed to the holding mode, the measured total leakage current Ileak can be essentially memorized by a voltage held in the first sample-and-hold circuit 230.
During a third time period TC, the pixel element 50AA is selected as the selected element, the first sample-and-hold circuit 230 is set to the holding mode while the second sample-and-hold circuit 270 is set to the sampling mode, and a signal is applied to the switch control input 204 to enable the switch circuit 240 to connect the inverting input of the first differential amplifier 280 to the output of the first sample-and-hold circuit. During the third time period TC, the current sensing resistor 210, the instrumentation amplifier 220, the second sample-and-hold circuit 270, the first differential amplifier 280, and the second differential amplifier 290 can complete a negative feedback loop. When the second differential amplifier 290 receives a data voltage V(AA), a predetermined current of the value Id(AA)=V(AA)/RsGv+Ileak is applied to the column conducting line 30A. If the total amount of leakage currents by the nonlinear elements in the non-selected pixel elements (e.g., 50BA, 50CA, . . . ) is almost equal to Ileak (which includes additional leakage current if the pixel element 50AA is also a non-selected pixel element), then, the current passing through the nonlinear element 51 in the selected pixel element 50AA is almost equal to V(AA)/RsGv. Consequently, the voltage applied to the first terminal of the capacitive element 54 is almost equal to R0V(AA)/RsGv+Von. Here, Von is the voltage at the first terminal of the resistive element 55.
For those implementations of active matrix displays in which the second terminal of the capacitive element 54 is connected to the first terminal of the resistive element 55, the voltage applied across the capacitive element 54 in a selected pixel element (e.g., 50AA) can be almost equal to R0V(AA)/RsGv. Thus, the voltage applied across the capacitive element 54 can be almost entirely determined by a data voltage (e.g., the input voltage V(AA) applied to the data driver 70A) and a few circuit parameters (e.g., R0, Rs, and Gv).
The data driver 70A in
For those implementations of active matrix displays in which the second terminal of the capacitive element 54 is not connected to the first terminal of the resistive element 55, and the voltage applied on the first terminal of the resistive element 55 also depends on some voltage drops on a row conducting line, it may still possible to correct the voltage drops. For example, in a simple model in which the resistance of the row conducting line between two adjacent pixel elements is uniformly AR, the voltage on the second terminal of the resistive element 55 in the pixel elements 50AA, 50AB, and 50AC is respectively given by the following equations:
VAA=Von+R0Id(AA)+ΔR[Id(AA)+Id(AB)+Id(AC)];
VAB=Von+R0Id(AB)+ΔR[Id(AA)+2Id(AB)+2Id(AC)]; and
VAC=Von+R0Id(AC)+ΔR[Id(AA)+2Id(AB)+3Id(AC)].
Here, the current Id(AA), Id(AB), and Id(AC) is respectively the current passing through the resistive element 55 in the pixel elements 50AA, 50AB, and 50AC. By solving above linear equations, the required current Id(AA), Id(AB), and Id(AC) for creating the desired target voltage values can be calculated.
The block 410 includes creating multiple rows of enabled pixel elements during a predetermined time period. The block 410 further includes a block 412 which includes driving the semiconductor channel of the switching transistor in an enabled pixel element into a conducting state.
As examples, when the block 410 is applied to the active matrix display as shown
The block 420 includes selecting a row of pixel elements in the multiple rows of enabled pixel elements to create a plurality of selected pixel elements during a sub-time-period that is a fraction of the predetermined time period. The block 420 further includes a block 422 which includes driving the nonlinear element in a selected pixel element into a conducting state.
As examples, when the block 420 is applied to the active matrix display as shown
The block 430 includes charging the capacitive element in a selected pixel element. In one implementation, the block 430 includes a block 432 which includes applying a predetermined current to a column conducting line that is electrically connected the nonlinear element in the selected pixel element. In other implementations, the block 430 can includes a block 432 which includes applying a predetermined voltage to a column conducting line.
As examples, when the block 430 is applied to the active matrix display as shown
The block 510 includes forming a row of selected pixel elements in the matrix of pixel elements. The block 510 further includes a block 512 which includes driving the nonlinear element in each selected pixel element into a conducting state.
As examples, when the block 510 is applied to the active matrix display as shown
The block 520 includes forming non-selected pixel elements in multiple rows of pixel elements. The block 520 further includes a block 522 which includes driving the nonlinear element in a non-selected pixel element into a non-conducting state.
As examples, when the block 520 is applied to the active matrix display as shown
As examples, when the block 520 is applied to the active matrix display as shown
As examples, when the block 520 is applied to the active matrix display as shown
The block 530 includes charging multiple selected pixel elements in the row of selected pixel elements. The block 530 further includes a block 532 which includes generating a predetermined current that passes through both the nonlinear element and the resistive element in a selected pixel element.
As examples, when the block 530 is applied to the active matrix display as shown
When a pixel element (e.g., the pixel element 50AB as shown in
In general, when the semiconductor channel of the switching transistor 52 is at the non-conducting state during the fourth time period t4, the change of the voltage across the capacitive element 54 due to any leakage current through the semiconductor channel of the switching transistor 52 can be generally neglected. When the nonlinear element 51 is at the non-conducting state after the beginning the third time period t3, the change of the voltage across the capacitive element 54 due to any leakage current through the nonlinear element 51 can be generally neglected at least until the beginning of the fourth time period t4. In some implementations, when the nonlinear element 51 is at the non-conducting state after the beginning the third time period t3, the voltage across the capacitive element 54 can be substantially maintained at least until the beginning of the fourth time period t4. In some other implementations, when the nonlinear element 51 is at the non-conducting state after the beginning of the third time period t3, the residual conductivity of the nonlinear element 51 at the non-conducting state can be small enough such that the change of the voltage across the capacitive element 54 during the time period from the beginning of the third time period to the beginning of the fourth time period t4 can be easily corrected. For example, when the nonlinear element 51 in the pixel element 50AB of
In one specific implementation, when the active matrix display in
The active matrix display in
In one specific implementation, an active matrix display has N rows of pixel elements divided into K sections. The fourth time period t4 can be selected to be K−1 times as long as the first time period t1. In one example, in which an active matrix display has 12 rows of pixel elements divided into 3 sections, the fourth time period t4 can be selected to be 2 times as long as the first time period t1. In another example, in which an active matrix display has 1024 rows of pixel elements divided into 256 sections, the fourth time period t4 can be selected to be 255 times as long as the first time period t1. In another example, in which an active matrix display has 1024 rows of pixel elements divided into 128 sections, the fourth time period t4 can be selected to be 127 times as long as the first time period t1.
In one specific implementation, an active matrix display has N rows of pixel elements divided into K sections. The second time period t2 can be selected to be about equal to Tframe/N or somewhat smaller than Tframe/N, and the first time period t1 can be selected to be about Tframe/K, where Tframe is one frame time period. In one example, in which an active matrix display has 12 rows of pixel elements divided into 3 sections, the second time period t2 can be selected to be about Tframe/12, and the first time period t1 can be selected to be about Tframe/3 or somewhat smaller than Tframe/3. In another example, an active matrix display has 1024 rows of pixel elements divided into 256 sections, the second time period t2 can be selected to be about Tframe/1024 or somewhat smaller, and the first time period t1 can be selected to be about Tframe/256 or somewhat smaller than Tframe/256. In another example, an active matrix display has 1024 rows of pixel elements divided into 128 sections, the second time period t2 can be selected to be about Tframe/1024 or somewhat smaller, and the first time period t1 can be selected to be about Tframe/128 or somewhat smaller than Tframe/128.
In some other implementations, an active matrix display has N rows of pixel elements and it does not need to be divided into sections. The second time period t2 can be selected to be about equal to Tframe/N or somewhat smaller than Tframe/N, and the first time period t1 can be selected to be about K times of t2, that is, t1=Kt2, where K generally can be selected to be a positive real number (i.e., not just an integer) that is larger than 1.2, 2.0, 3.0, 4.0, 8.0, 16.0, 32.0, 64.0, 128.0, or 255.0.
In one example, a column of pixel elements (e.g., the column B) in
In
In
In
In
In
In
In
The implementations of the pixel elements descried in Applicant's instant applications are merely examples. The methods descried in Applicant's instant applications can be applied to many other kinds of pixel elements. In particular, if a current design or a future design of certain pixel element includes an FET linear switch for controlling a data signal applied to a storage capacitor, after such pixel element is modified by replacing such FET linear switch with a linear switch that includes a nonlinear element and a switching transistor, the modified pixel element generally can be controlled by some implementations of the methods as descried in Applicant's instant applications.
In the foregoing specification, specific embodiments have been described. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present teachings.
The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims. The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued.
Moreover in this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” “has”, “having,” “includes”, “including,” “contains”, “containing” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises, has, includes, contains a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by “comprises . . . a”, “has . . . a”, “includes . . . a”, “contains . . . a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises, has, includes, contains the element. The terms “a” and “an” are defined as one or more unless explicitly stated otherwise herein. The terms “substantially”, “essentially”, “approximately”, “about” or any other version thereof, are defined as being close to as understood by one of ordinary skill in the art, and in one non-limiting embodiment the term is defined to be within 10%, in another embodiment within 5%, in another embodiment within 1% and in another embodiment within 0.5%. The term “coupled” as used herein is defined as connected, although not necessarily directly and not necessarily mechanically. A device or structure that is “configured” in a certain way is configured in at least that way, but may also be configured in ways that are not listed.
The Abstract of the Disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure, It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, it can be seen that various features are grouped together in various embodiments for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separately claimed subject matter.
The present application is a Continuation-In-Part Application of U.S. patent application Ser. No. 11/426,147 titled “METHOD OF DRIVING ACTIVE MATRIX DISPLAYS”. This application claims the benefit of U.S. Provisional Application No. 60/693,595, filed on Jun. 25, 2005, and U.S. Provisional Application No. 60/708,334, filed on Aug. 14, 2005, and U.S. application Ser. No. 11/426,147, filed on Jun. 23, 2006.
| Number | Name | Date | Kind |
|---|---|---|---|
| 20010028337 | Wu et al. | Oct 2001 | A1 |
| 20040169631 | Tanaka et al. | Sep 2004 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 60708334 | Aug 2005 | US | |
| 60693595 | Jun 2005 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11426147 | Jun 2006 | US |
| Child | 13225542 | US |
