Circuit for driving liquid drop spraying apparatus

A circuit for driving a liquid drop spraying apparatus including a plurality of units for spraying a small amount of liquid drops, each unit comprising a liquid spraying nozzle, a pressure chamber for pressurizing liquid to be sprayed from the nozzle, an introduction hole for supplying liquid to the pressure chamber, and a piezoelectric/electrostrictive element for operating the pressure chamber, wherein the introduction hole of each unit communicates with a common liquid supply path, the ratio of a diameter of the introduction hole to a diameter of the nozzle is in a range of 0.6 to 1.6, and the ratio of a diameter of the nozzle to the thickness of the nozzle is in a range of 0.2 to 4, said circuit comprising:

• at least one discharging circuit for discharging current from the piezoelectric/electrostrictive element from a starting discharge voltage to a final discharge voltage thereby deforming a wall of the pressure chamber and discharging from the nozzle the liquid supplied to the pressure chamber by a pressure produced in the pressure chamber, said discharging circuit holding a final discharge voltage for a predetermined time;
• and
• at least one charging circuit comprising at least one inductor and at least one resistor connected in series with said piezoelectric/electrostrictive element, said charging circuit sequentially performing first and second charging steps with at least two charge time constants, wherein the first charge time is constant is greater than the second charge time constant, said charging circuit starting the second charging step at a voltage that is 30% to 65% of a voltage difference between a final discharge voltage and a starting discharge voltage when the final discharge voltage is defined as a reference.