Patent ID: 9035585
Filing Date: 2015-05-19
Classification: H02H,H02P

Abstract:
1. A motor drive circuit characterized in that when first source-side and second sink-side transistors and second source-side and first sink-side transistors are turned on/off in a complementary manner so as to supply a drive current to a drive coil connected between a first connection point of the first source-side transistor and the first sink-side transistor connected in series and a second connection point of the second source-side transistor and the second sink-side transistor connected in series, the first or the second sink-side transistor is turned on/off according to a PWM signal and synchronous rectification is performed for the motor drive circuit such that the first or the second source-side transistor in an off state is turned on and kept on during a time period during which the first or the second sink-side transistor is off according to the PWM signal, and that the motor drive circuit includes: a detection circuit configured to detect a reverse current to flow in a direction from the first sink-side transistor to the second source-side transistor or in a direction from the second sink-side transistor to the first source-side transistor; a disable circuit configured to disable a detection output of the detection circuit during a predetermined time period from a start of detection of the reverse current performed by the detection circuit; a first inhibit circuit configured to inhibit the synchronous rectification according to a detection output of the detection circuit when the predetermined time period has elapsed from a start of detection of the reverse current performed by the detection circuit; a second inhibit circuit configured to inhibit the synchronous rectification irrespective of an operation of the first inhibit circuit, when each on-duty period of the PWM signal to turn on the first or the second sink-side transistor is shorter than the predetermined time period; and a third inhibit circuit configured to inhibit the synchronous rectification irrespective of an operation of the first or the second inhibit circuit, when the PWM signal has a period in which a direction of a current supplied to the drive coil is changed to a direction opposite to a direction thereof at a time of a start of the synchronous rectification.