Capacitive load driving circuit, droplet ejection device, droplet ejection unit and inkjet head driving circuit

A capacitive load driving circuit which applies a driving signal to a capacitive load for driving the capacitive load, the capacitive load driving circuit comprising:

• an operational amplifier, which outputs a differential signal between a signal which is fed back to an inverting input terminal and an input signal which is inputted to a non-inverting input terminal;
• a pulse width modulator, which pulse width-modulates output of the operational amplifier and outputs a digital signal;
• a digital power amplifier, which amplifies power of the digital signal;
• a first filter, which smooths output of the digital power amplifier and inputs the smoothed signal to the capacitive load as the driving signal;
• a second feedback circuit, which feeds back a signal outputted from the digital power amplifier, which signal includes a phase which is advanced relative to the driving signal, to the inverting input terminal of the operational amplifier;
• and
• a third feedback circuit, which feeds back the driving signal, which has been outputted from the first filter and propagated through wiring resistance between the first filter and the capacitive load to the inverting input terminal of the operational amplifier.

A capacitive load driving circuit which applies a driving signal to a capacitive load for driving the capacitive load, the capacitive load driving circuit comprising:

• an operational amplifier, which outputs a differential signal between a signal which is fed back to an inverting input terminal and an input signal which is inputted to a non-inverting input terminal;
• a pulse width modulator, which pulse width-modulates output of the operational amplifier and outputs a digital signal;
• a digital power amplifier, which amplifies power of the digital signal;
• a first filter, which smooths output of the digital power amplifier and inputs the smoothed signal to the capacitive load as the driving signal;
• a first feedback circuit, which feeds back the driving signal outputted from the first filter to the inverting input terminal of the operational amplifier;
• and
• at least one of
• a second feedback circuit, which feeds back a signal outputted from the digital power amplifier, which signal includes a phase which is advanced relative to the driving signal, to the inverting input terminal of the operational amplifier and
• a third feedback circuit, which feeds back the driving signal, which has been outputted from the first filter and propagated through wiring resistance between the first filter and the capacitive load, to the inverting input terminal of the operational amplifier.

A droplet ejection device comprising:

• a plurality of capacitive load driving circuits;
• and
• a droplet ejection head, which includes a capacitive load for causing a droplet to be ejected from a nozzle of the head, wherein
• each capacitive load driving circuit includes:
• an operational amplifier, which outputs a differential signal between a signal which is fed back to an inverting input terminal and an input signal which is inputted to a non-inverting input terminal;
• a pulse width modulator, which pulse width-modulates output of the operational amplifier and outputs a digital signal;
• a digital power amplifier, which amplifies power of the digital signal;
• a first filter, which smooths output of the digital power amplifier and inputs the smoothed signal to the capacitive load as a driving signal;
• a first feedback circuit, which feeds back the driving signal outputted from the first filter to the inverting input terminal of the operational amplifier;
• and
• at least one of
• a second feedback circuit, which feeds back a signal outputted from the digital power amplifier, which signal includes a phase which is advanced relative to the driving signal, to the inverting input terminal of the operational amplifier and
• a third feedback circuit, which feeds back the driving signal, which has been outputted from the first filter and propagated through wiring resistance between the first filter and the capacitive load, to the inverting input terminal of the operational amplifier.

A droplet ejection unit comprising:

• a droplet ejection element which includes a capacitive load corresponding with a pressure generation chamber which is charged with droplets to be ejected from a nozzle, the droplet ejection element ejecting the droplet from the nozzle when a driving signal is applied to the capacitive load for altering a capacity of the pressure generation chamber;
• and
• a capacitive load driving circuit which applies the driving signal to the capacitive load for driving the capacitive load, wherein
• the capacitive load driving circuit includes:
• an operational amplifier, which outputs a differential signal between a signal which is fed back to an inverting input terminal and an input signal which is inputted to a non-inverting input terminal;
• a pulse width modulator, which pulse width-modulates output of the operational amplifier and outputs a digital signal;
• a digital power amplifier, which amplifies power of the digital signal;
• a first filter, which smooths output of the digital power amplifier and inputs the smoothed signal to the capacitive load as the driving signal;
• a second feedback circuit, which feeds back a signal outputted from the digital power amplifier, which signal includes a phase which is advanced relative to the driving signal, to the inverting input terminal of the operational amplifier;
• and
• a third feedback circuit, which feeds back the driving signal, which has been outputted from the first filter and propagated through wiring resistance between the first filter and the capacitive load to the inverting input terminal of the operational amplifier.

A droplet ejection unit comprising:

• a droplet ejection element which includes a capacitive load corresponding with a pressure generation chamber which is charged with droplets to be ejected from a nozzle, the droplet ejection element ejecting the droplet from the nozzle when a driving signal is applied to the capacitive load for altering a capacity of the pressure generation chamber;
• and
• a capacitive load driving circuit which applies the driving signal to the capacitive load for driving the capacitive load, wherein
• the capacitive load driving circuit includes:
• an operational amplifier, which outputs a differential signal between a signal which is fed back to an inverting input terminal and an input signal which is inputted to a non-inverting input terminal;
• a pulse width modulator, which pulse width-modulates output of the operational amplifier and outputs a digital signal;
• a digital power amplifier, which amplifies power of the digital signal;
• a first filter, which smooths output of the digital power amplifier and inputs the smoothed signal to the capacitive load as a driving signal;
• a first feedback circuit, which feeds back the driving signal outputted from the first filter to the inverting input terminal of the operational amplifier;
• and
• at least one of
• a second feedback circuit, which feeds back a signal outputted from the digital power amplifier, which signal includes a phase which is advanced relative to the driving signal, to the inverting input terminal of the operational amplifier and
• a third feedback circuit, which feeds back the driving signal, which has been outputted from the first filter and propagated through wiring resistance between the first filter and the capacitive load, to the inverting input terminal of the operational amplifier.

A driving circuit of an inkjet head which includes a piezoelectric actuator corresponding with a pressure generation chamber which is charged with ink to be ejected from a nozzle, the driving circuit causing an ink droplet to be ejected from the nozzle by applying a driving signal to the piezoelectric actuator for altering a capacity of the pressure generation chamber, and the inkjet head driving circuit comprising:

• an operational amplifier, which outputs a differential signal between a signal which is fed back to an inverting input terminal and an analog driving signal which is inputted to a non-inverting input terminal;
• a pulse width modulator, which pulse width-modulates output of the operational amplifier and outputs a digital signal;
• a digital power amplifier, which amplifies power of the digital signal,
• a first filter, which smooths output of the digital power amplifier and inputs the smoothed signal to the piezoelectric actuator as the driving signal for causing an ink droplet to be ejected from the nozzle of the inkjet head;
• a first feedback circuit, which feeds back the driving signal outputted from the first filter to the inverting input terminal of the operational amplifier;
• and
• a second feedback circuit, which includes a second filter for smoothing output of the digital power amplifier and which feeds back a signal smoothed by the second filter to the inverting input terminal of the operational amplifier.