Patent ID: 8254077

Claim:
A solenoid valve driving circuit for driving a solenoid valve by applying a first voltage with respect to a solenoid coil of the solenoid valve during a first period, and for maintaining a driven state of the solenoid valve by repeatedly applying pulse voltage at substantially the same voltage level as the first voltage, as a second voltage with respect to the solenoid coil during a second period following the first period, comprising: a current detector that detects a current that flows in the solenoid coil; a rate of change over time calculating unit configured to calculate a rate of change over time of the current; and a maintaining state transition determining unit configured to determine a transition from the first period to the second period based on the rate of change over time, wherein after the first voltage with respect to the solenoid coil is applied, the rate of change over time becomes substantially zero at a first time, and a current value of the current decreases at a second time after the first time, and wherein the maintaining state transition determining unit selects, as a point of transition from the first period to the second period, either a third time, which is when the current value has increased back to the current value at the first time and which is after the second time, or a fourth time which is after the third time and which is after the current value at the first time has been maintained.