System and method for controlling current density in thermal printheads

A method for limiting electromigration within heater resistors of a printhead of an ink jet printer, the method comprising the steps of:

• determining a resistance drop off characteristic of the printhead heater resistors;
• identifying a substantially stable resistance value of the printhead heater resistors based upon the resistance drop off characteristic;
• running the printhead through a resistor burn in operation which involves repeatedly firing a multiplicity of the heater resistors until a resistance value of each heater resistor of said multiplicity drops to the substantially stable resistance value, wherein the step of running the printhead through a burn in operation is performed during an initialization sequence of the ink jet printer.

A method for limiting electromigration within heater resistors of a printhead of an ink jet printer, the method comprising the steps of:

• determining a resistance drop off characteristic of the printhead heater resistors;
• identifying a substantially stable resistance value of the printhead heater resistors based upon the resistance drop off characteristic;
• running the printhead through a resistor burn in operation which involves repeatedly firing a multiplicity of the heater resistors until a resistance value of each heater resistor of said multiplicity drops to the substantially stable resistance value, wherein the step of running the printhead through a burn in operation is performed while ink is delivered to the printhead such that ink is ejected from the printhead during the burn in operation.

A printer mechanism, comprising:

• a printhead including a plurality of heater resistors;
• a printhead driver circuit operatively connected to the printhead for selectively energizing the heater resistors;
• a controller connected with said printhead driver circuit for effecting operation thereof, wherein the controller is operable to determine a resistance of the printhead heater resistors, and the controller is further operable to adjust a firing voltage across the heater resistors based at least in part upon the determined resistance value, wherein the controller is operable to adjust the firing voltage across the heater resistors in order to maintain current density through the resistors at or below an established threshold maximum level.

A printer mechanism, comprising:

• a printhead including a plurality of heater resistors;
• a printhead driver circuit operatively connected to the printhead for selectively energizing the heater resistors;
• a controller connected with said printhead driver circuit for effecting operation thereof, wherein the controller is operable to determine a resistance of the printhead heater resistors, and the controller is further operable to adjust a firing voltage across the heater resistors based at least in part upon the determined resistance value, wherein the controller is operable to determine resistance of the printhead heater resistors by tracking a number of times the heater resistors are fired and determining a resistance value of the heater resistors based upon the tracked number, wherein a dot count is maintained in memory associated with the printhead, and the controller is connected to receive information from the printhead memory.

A printer mechanism, comprising:

• a printhead including a plurality of heater resistors;
• a printhead driver circuit operatively connected to the printhead for selectively energizing the heater resistors;
• a controller connected with said printhead driver circuit for effecting operation thereof, wherein the controller is operable to determine a resistance of the printhead heater resistors, and the controller is further operable to adjust a firing voltage across the heater resistors based at least in part upon the determined resistance value, wherein the controller is operable to determine resistance of the printhead heater resistors by repeatedly determining a thermal turn on energy of the printhead and correlating changes in determined thermal turn on energy to changes in resistance of the heater resistor.