Patent ID: 10337634

Abstract:
A current control circuit controls a linear solenoid valve provided in an oil pressure circuit to feed back an output oil pressure. The current control circuit includes a PWM signal generation part, a target setting part, a duty ratio setting part and a vibration detection circuit. The target setting part sets a target current value, which is a target value of an excitation current of the linear solenoid valve and periodically varies with a predetermined dither amplitude and a dither period longer than a pulse period of the PWM signal. The self-excited vibration detection part calculates a phase difference between the target current value and an actual current value and detects a presence of self-excited vibration because of a resonance of a feedback of the output oil pressure and driving of the linear solenoid valve in the dither period when the phase difference decreases relative to an increase in the target current value or the phase difference increases relative to a decrease in the dither period.