Patent ID: 7732978
Filing Date: 2010-06-08
Classification: H01L

Abstract:
1. A piezoelectric element driving circuit comprising: a transformer having a turns ratio at which a rate of a number of turns of a secondary winding on a load side is high with respect to a number of turns of a primary winding on a power supply side, exceeding a ratio of a power supply side voltage value to a specification voltage value on the load side; a switch circuit for performing switching operation on power supply voltage at a driving frequency on a primary side of said transformer to apply a driving voltage to a piezoelectric element connected to a secondary side of said transformer; a reactance element connected in parallel with said piezoelectric element on one of the primary side and the secondary side of said transformer, the reactance element forming a resonant circuit that performs parallel resonance at said driving frequency with a capacitance component in an equivalent circuit of said piezoelectric element and an inductance component of said transformer; a pulse generating circuit for generating a driving pulse for said switch circuit; and a duty ratio controlling circuit for being supplied with said driving pulse, limiting a duty ratio of said driving pulse such that a value of said driving voltage falls within a range equal to or lower than the specification voltage value on said load side, and outputting the driving pulse whose duty ratio is limited to said switch circuit.