PROBLEM TO BE SOLVED: To provide a solenoid drive device and an automatic transmission, capable of reducing an abnormal detection time.;SOLUTION: A solenoid 2 of an automatic transmission 1 is driven by a speed-change controller 3. In the speed-change controller 3, a base current Iaim is set on the basis of a signal indicating a state of an engine or the like by a base setting part 14 of a target current setting part 9, a dither current Idth is added by a dither setting part 10, and an excitation current is set. A duty ratio is set so as to electric conduct the excitation current to the solenoid 2, and a PWM signal is generated on the basis of it. An abnormal detection part 14 of an abnormal determination part 13 calculates and determines a mean current of a dither period of the solenoid 2, and prohibits a dither function when an abnormality is detected. When the abnormality is determined by calculating the mean current in the PWM period by the abnormal detection part 14, a fail-safe processing is executed by an in-abnormality control part 19.;SELECTED DRAWING: Figure 1;COPYRIGHT: (C)2019,JPO&INPIT
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