THERMAL INK JET PRINTHEAD DRIVER OVERCURRENT PROTECTION SCHEME

摘要

Disclosed is a method and apparatus for detection of low to moderate impedance short circuits on any driven line of a thermal ink jet printer to inhibit damage to printer driver circuitry, principally active elements thereof. The printer includes a printhead having a plurality of thermally activated print nozzles therein for ink ejection upon thermal agitation of the ink within the nozzle, and data and address drive lines driven by data line and address line drivers for selection and activation of nozzle heater active elements associated with each of the nozzles by effecting current flow through a heater element associated with each of said nozzles upon selection by associated address and data line activation. One method includes the steps of energizing one of a data line and address lines associated with at least one thermal ink jet nozzle on the printhead, detecting a lower than normal impedance on the energized line, and inhibiting further activation or energization of at least one of the data and address line drivers. The inhibiting step may be accomplished, for example, by disabling the power supply associated with driver associated with the line having lower than normal impedance and/or by preventing the printer driver circuit fromproviding data and/or address signals to the printhead.