Error detection apparatus for an electro-optic display
First Claim
1. Error detection apparatus for an electro-optic display of a type comprising at least one capacitive display element, each display element connected to drive circuitry which applies a first drive signal, which alternates between two voltage states, to a first electrode of the display element and applies a second drive signal, which alternates between said two voltage states, to a second electrode of the display element, wherein said first and second drive signals are in phase for a display element to be in an "OFF" state and said drive signals are out of phase for a display element to be in an "ON" state, the apparatus comprising:
- means for electrically isolating the first electrode of a display element to be tested from the drive circuitry,means for generating a bias voltage at a bias voltage terminal wherein said bias voltage is selected, during a test, to be distinct from the voltage state of the first drive signal of the element being tested,a resistor connected between said first electrode of the element being tested and said bias voltage terminal,means for generating a reference voltage, having a value between said bias voltage and said voltage state of the first drive signal of the element being tested,means for comparing a voltage on said first electrode of the element being tested with said reference voltage, andmeans for generating an error signal if said voltage on said first electrode crosses said reference voltage within a predetermined period of time wherein the value of the resistor and predetermined period are such that, when no fault condition exists, said voltage on said first electrode does not cross the reference voltage within the predetermined period.
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Abstract
An apparatus for and method of detecting errors in an electro-optic display of a type comprising one or more capacitive display elements. Each display element is connected to drive circuitry. The apparatus includes an isolator for electrically isolating the first electrode of a display element to be tested from the drive circuitry. A comparator compares a voltage on the first electrode of the element being tested with a reference voltage, and an error signal generator generates an error signal if the voltage on the first electrode crosses the reference voltage within a predetermined period of time.
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Citations
11 Claims
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1. Error detection apparatus for an electro-optic display of a type comprising at least one capacitive display element, each display element connected to drive circuitry which applies a first drive signal, which alternates between two voltage states, to a first electrode of the display element and applies a second drive signal, which alternates between said two voltage states, to a second electrode of the display element, wherein said first and second drive signals are in phase for a display element to be in an "OFF" state and said drive signals are out of phase for a display element to be in an "ON" state, the apparatus comprising:
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means for electrically isolating the first electrode of a display element to be tested from the drive circuitry, means for generating a bias voltage at a bias voltage terminal wherein said bias voltage is selected, during a test, to be distinct from the voltage state of the first drive signal of the element being tested, a resistor connected between said first electrode of the element being tested and said bias voltage terminal, means for generating a reference voltage, having a value between said bias voltage and said voltage state of the first drive signal of the element being tested, means for comparing a voltage on said first electrode of the element being tested with said reference voltage, and means for generating an error signal if said voltage on said first electrode crosses said reference voltage within a predetermined period of time wherein the value of the resistor and predetermined period are such that, when no fault condition exists, said voltage on said first electrode does not cross the reference voltage within the predetermined period. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for detecting errors in an electro-optic display of a type comprising at least one capacitive display element, each display element connected to drive circuitry which applies a first drive signal, which alternates between two voltage states, to a first electrode of the display element and applies a second drive signal, which alternates between said two voltage states, to a second electrode of the display element, wherein said first and second drive signals are in phase for a display element to be in an "OFF" state and said drive signals are out of phase for a display element to be in an "ON" state, the method comprising the following steps:
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electrically isolating the first electrode of a display element to be tested from the drive circuitry, generating a bias voltage at a bias voltage terminal, connecting a resistor between said first electrode of the element being tested and said bias voltage terminal, wherein said bias voltage is selected, during a test, to be distinct from the voltage state of the first drive signal of the element being tested, generating a reference voltage, having a value between said bias voltage and said voltage state of the first drive signal of the element being tested, comparing a voltage on said first electrode of the element being tested with said reference voltage, and generating an error signal if said voltage on said first electrode crosses said reference voltage within a predetermined period of time wherein the value of the resistor and predetermined period are such that, when no fault condition exists, said voltage on said first electrode does not cross the reference voltage within the predetermined period.
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Specification