Electrostatic discharge protection for pixellated electronic device
First Claim
1. An electronic device comprising:
- an array of pixels provided on a substrate and arranged in rows and columns, each pixel comprising a switching element;
a plurality of row and column address lines for addressing each pixel;
wherein each row and column address line is connected to a first discharge element through a first discharge device and to a second discharge element through a second discharge device, wherein the first discharge device allows the passage of charge between the address line and the first discharge element when the address line is at a potential below that of the first discharge element, and the second discharge device allows the passage of charge between the address line and the second discharge element when the address line is at a potential above that of the second discharge element.
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Accused Products
Abstract
An electronic device (10) comprises an array of pixels (12), arranged in rows and columns (14,16) with row and column address lines (18,20) for addressing each pixel (12). Each row and column address line is connected to two discharge lines (30,32) through a discharge circuit (38). The circuit allows the passage of charge between the address line and the first discharge line (30) when the address line is at a potential below that of the first discharge line, and allows the passage of charge between the address line and the second discharge line (32) when the address line is at a potential above that of the second discharge line. This provides electrostatic discharge protection against an increase or decrease in voltage on the row or column address lines during manufacture of the device. By providing suitable voltages on the two discharge lines during operation of the manufactured device, it is possible to prevent the discharge circuit from operating, thereby saving power.
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Citations
20 Claims
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1. An electronic device comprising:
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an array of pixels provided on a substrate and arranged in rows and columns, each pixel comprising a switching element;
a plurality of row and column address lines for addressing each pixel;
wherein each row and column address line is connected to a first discharge element through a first discharge device and to a second discharge element through a second discharge device, wherein the first discharge device allows the passage of charge between the address line and the first discharge element when the address line is at a potential below that of the first discharge element, and the second discharge device allows the passage of charge between the address line and the second discharge element when the address line is at a potential above that of the second discharge element. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
wherein with no external voltages applied to the first and second discharge elements, the first path provides electrostatic protection, and the transistor in the second path is turned off, and with external voltages applied to the first and second discharge elements, the transistor in the first path is turned off, and the transistor in the second path is turned on and provides a high impedance between the first and second discharge elements. -
13. A device as claimed in claim 12, wherein the protection circuit further comprises a first connection for connecting a first, low, external voltage to the first discharge element and a second connection for connecting a second, high, voltage to second discharge element.
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14. A device as claimed in claim 1 wherein a protection circuit is provided between the first and second discharge elements, the protection circuit comprising:
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a first path between the first and second discharge elements, comprising a first transistor;
a second path between the first and second discharge elements, comprising a second transistor and a resistor in series, wherein the gate of the first transistor is connected to the junction between the resistor and the second transistor, and wherein the second transistor has a gate control line to enable it to be turned on or off.
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15. A device as claimed in claim 14, wherein with no signal applied to the gate control line, the second transistor is turned off, and wherein if the second transistor is turned on, the voltage at the junction is such as to turn off the first transistor.
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16. A device as claimed in claim 1, comprising a liquid crystal display.
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17. A device as claimed in claim 1, wherein the switching elements of the pixels comprise thin film transistors.
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18. A device as claimed in claim 3, wherein
the second discharge element includes another conductive track that is also arranged around the periphery of the pixel array. -
19. A device as claimed in claim 18, wherein
each discharge element comprises at least one diode-connected transistor. -
20. A device as claimed in claim 19, further including
a protection circuit between the first and second discharge elements.
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Specification