Patent ID: 7841685

Claim:
A printing apparatus comprising: a recording head including a recording element which performs recording on a recording medium and ejecting liquid, wherein the recording head comprises: a passage unit formed with an individual liquid passage having a pressure chamber and an ejection port which ejects liquid; and a piezoelectric actuator element which applies pressure to liquid contained in the pressure chamber; a driver IC including a drive circuit which applies a drive signal to the recording element, and a dummy drive circuit which outputs a dummy signal having a value associated with the drive signal; a dummy signal detection circuit which detects a current value of the dummy signal; a reference current value determiner which determines a reference current value, associated with a value of a current which is supposed to flow through the drive circuit, to be a value adapted for an actual operating environment of the printing apparatus, the actual operating environment being defined by a combination of an ambient temperature of the printing apparatus and the kind of liquid ejected from the recording head; and a drive signal control circuit which controls the drive signal based on a current value of the dummy signal detected by the dummy signal detection circuit and the reference current value, wherein the drive signal control circuit comprises a drive potential applicator which applies a drive potential to the drive circuit and the dummy drive circuit, wherein each of the drive circuit and the dummy drive circuit comprises a first terminal to which the drive potential applicator applies the drive potential, a second terminal which is kept at a predetermined potential different from the drive potential, and a third terminal, wherein the drive circuit is able to selectively take either one of a charge state where the third terminal is connected to the first terminal but not connected to the second terminal and a discharge state where the third terminal is connected to the second terminal but not connected to the first terminal, wherein the third terminal of the drive circuit is connected to the piezoelectric actuator element, and the third terminal of the dummy drive circuit is connected to the dummy signal detection circuit, and wherein a current value of a dummy signal outputted from the dummy drive circuit is identical to either one of an initial value of a current which flows through the drive circuit at a time when a state of the drive circuit is switched from the charge state to the discharge state and an initial value of a current which flows through the drive circuit at a time when a state of the drive circuit is switched from the discharge state to the charge state.