Energy control circuit for a thermal ink-jet printhead

A circuit for controlling energy delivered to a heater resistor of a thermal inkjet printhead, comprising:

• level shifter means for receiving a printer control signal and for shifting a voltage level of the printer control signal resulting in an output signal;
• driver means, responsive to the output signal of the level shifter means, for applying a driver output voltage to the heater resistor to provide energy to the resistor;
• and
• comparator means for comparing the driver output voltage against a reference voltage and producing in response a comparator output signal, the comparator output signal communicated to the level shifter means to adjust the driver output voltage so as to maintain a voltage across the heater resistor at a level for providing a desired amount of energy to the heater resistor.

A circuit for controlling energy delivered to a heater resistor of a thermal inkjet printhead, comprising:

• level shifter means for receiving a printer control signal and for shifting a voltage level of the printer control signal resulting in an output signal;
• driver means responsive to the output signal of the level shifter means, for applying a driver output voltage to the heater resistor to provide energy to the resistor;
• difference means for obtaining a voltage across the heater resistor;
• and
• comparator means for comparing the voltage across the heater resistor against a reference voltage and producing in response a comparator output signal, the comparator output signal communicated to the level shifter means to adjust the driver output voltage so as to maintain the voltage across the heater resistor at a level for providing a desired amount of energy to the heater resistor.

A method for controlling energy delivered to a heater resistor of a thermal inkjet printhead, comprising the steps of:

• applying a signal to the heater resistor to provide said heater resistor with energy;
• comparing the applied signal against a reference signal to determine if the applied signal is providing the desired amount of energy;
• and
• in response to the comparison, adjusting the applied signal so that the applied signal provides the heater resistor with the desired amount of energy.