Method and structure for controlling the energizing of an ink jet printhead in a value dispensing device such as a postage meter

A postage meter comprising:

• a printhead for printing an indication of postage value on a recording medium;
• a motor for moving the printhead;
• microprocessor means for generating motor pulses to the motor to activate the motor to move the printhead at a desired speed over the recording medium, for performing additional functions within the postage meter, and for generating a motor pulse signal indicative of an actual motor pulse frequency;
• means for generating and sending a first fire pulse signal including a fire pulse which is fired at a fire pulse frequency to an ink jet printhead driver chip to selectively energize ink jet printhead nozzles to eject drops of ink onto the recording medium based on a predetermined relationship between an expected motor pulse frequency and the fire pulse frequency;
• means for compensating for variations in the speed of the ink jet printhead movement caused by variations in the actual motor pulse frequency relative to the expected motor Pulse frequency, the compensating means including means for receiving the motor pulse signal and continuously comparing the motor pulse signal indicative of the actual motor pulse frequency to the fire pulse frequency to determine if the predetermined relationship exists and if the predetermined relationship does not exist adjusting the fire pulse frequency based upon the variations to the actual motor pulse frequency to maintain the predetermined relationship thereby synchronizing the ink jet printhead movement with the energizing of the printhead nozzles;
• and
• means for accounting for the printed postage value.

A method for controlling energizing of an ink jet printhead comprising the steps of:

• generating motor pulses from a microprocessor to a motor to activate the motor to move the printhead at a desired speed over a recording medium;
• sending from the microprocessor a motor pulse signal indicative of an actual number of motor pulses generated by the microprocessor;
• generating and sending a fire pulse signal including a fire pulse which is fired at a fire pulse frequency from an ASIC to an ink jet printhead driver chip to selectively energize ink jet printhead nozzles to eject drops of ink onto the recording medium based on a desired predetermined relationship between the motor pulses generated by the microprocessor and the fire pulses generated by the ASIC;
• and
• compensating for variations in the speed of the ink jet printhead movement caused by variations in an actual frequency at which the motor pulses are generated by the microprocessor relative to an expected motor pulse frequency by using the ASIC for continuously comparing the actual number of motor pulses generated by the microprocessor to the actual number of fire pulses generated by the ASIC to determined if the predetermined relationship exists and if the predetermined relationship does not exist adjusting the fire pulse frequency to maintain the predetermined relationship thereby synchronizing the ink jet printhead movement with the energizing of the printhead nozzles.