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Error detection apparatus for an electro-optic display

  • US 5,515,390 A
  • Filed: 04/18/1994
  • Issued: 05/07/1996
  • Est. Priority Date: 04/22/1993
  • Status: Expired due to Fees
First Claim
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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:

  • 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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