Thermal inkjet printhead and printer energy control apparatus and method

A removable ink jet print head comprising:

• a connector having a plurality of electrical inputs connectable to a printer;
• a voltage input node connected to the connector;
• a plurality of firing resistors connected to the input node;
• an energy control circuit connected to the input node and operably connected to the resistors to simultaneously fire at least a plurality of the resistors with a firing pulse having a duration inversely related to the voltage at the input node.

A method of operating a thermal ink jet printer including a removable print head having a plurality of ink firing resistors comprising the steps:

• calibrating the printer by determining a nominal input voltage above a threshold necessary for simultaneous operation of a plurality of the resistors;
• printing by generating firing pulses during which selected resistors are connected between an input node and ground to generate thermal energy in the resistors;
• during printing, continually estimating the amount of energy dissipated in the selected resistors during each pulse;
• and
• ending the firing pulse when the energy dissipated reaches a preselected level.

A method of calibrating a thermal ink jet print head having a plurality of ink firing resistors groups each containing at least one resistor, and a memory device having a plurality of memory locations, the method comprising the steps:

• operating each group to determine an optimal operating voltage value for each of the groups;
• for each group, calculating a voltage correction value based on the optimal operating voltage value;
• and
• for each group, storing the voltage correction value in a different one of the memory locations.