Driving device and driving method of capacitive load and liquid jet printing apparatus

A driving method of a capacitive load comprising:

• modulating a drive waveform signal;
• power-amplifying the modulated signal in the modulation step by a pair of switching elements push-pull connected to each other;
• outputting the amplified digital signal obtained in the power-amplifying step as a drive signal towards at least one load capacitor as the capacitive load after low-pass filtering the amplified digital signal with an inductor;
• selecting the load capacitor and a dummy load capacitor to be connected to the inductor, respectively, so that a sum of a capacitance of the load capacitor and a capacitance of the dummy load capacitor to be connected to the inductor is kept within a predetermined range;
• feeding-back the drive signal as a feedback signal after executing a filtering process on the drive signal so that a frequency characteristic of a passing band of the drive signal output from the inductor to the load capacitor becomes substantially flat;
• and
• pulse-modulating a difference value between the drive waveform signal and the feedback signal.

A liquid jet printing apparatus comprising a driving device of a capacitive load including:

• a modulator adapted to execute pulse modulation on a drive waveform signal;
• a digital power amplifier adapted to power-amplify the modulated signal obtained by the modulator with a pair of switching elements push-pull connected to each other;
• an inductor adapted to low-pass filter the amplified digital signal obtained by the digital power amplifier and output the low-pass filtered signal as a drive signal towards at least one load capacitor as the capacitive load;
• at least one dummy load capacitor;
• a load selection control circuit adapted to select the load capacitor and the dummy load capacitor to be connected to the inductor, respectively, so that a sum of a capacitance of the load capacitor and a capacitance of the dummy load capacitor to be connected to the inductor is kept within a predetermined range;
• and
• a feedback circuit adapted to execute a filtering process on the drive signal so that a frequency characteristic of a passing band of the drive signal output from the inductor to the capacitor becomes substantially flat, and feedback the signal obtained to the modulator as a feedback signal,
• wherein the modulator executes the pulse modulation on a difference value between the drive waveform signal and the feedback signal.