Semiconductor device, motor drive system, and control method thereof

A motor drive system comprising:

• a three-phase motor configured to have a first phase, a second phase, and a third phase;
• a drive circuit configured to drive the three-phase motor;
• and
• a semiconductor device for controlling the drive circuit,
• wherein the semiconductor device includes:
• a current detection circuit configured to detect a current flowing through the three-phase motor by driving of the drive circuit;
• and
• a controller configured to control the drive circuit, based on the detected current,
• wherein the controller is configured to
• control, when the three-phase motor is stationary, the drive circuit to sequentially energize two of the first phase, the second phase and the third phase to create an energization pattern of a set of wave detection currents that sequentially flows in a first direction from the drive circuit to a first interphase between the first phase and the second phase, a second interphase between the second phase and the third phase, and a third interphase between the third phase and the first phase, then in a second direction from the first interphase, the third interphase, and the second interphase,
• obtain, from the set of wave detection currents detected by the current detection circuit, a first interphase current difference, a second interphase current difference, and a third interphase current difference, wherein:
• the first interphase current difference is a difference between wave detection currents in the first direction and the second direction in the first interphase;
• the second interphase current difference is a difference between wave detection currents in the first direction and the second direction in the second interphase;
• and
• the third interphase current difference is a difference between wave detection currents in the first direction and the second direction in the third interphase;
• and
• determine an initial energization pattern used in initial driving of the three-phase motor, based on a magnitude relationship among the first interphase current difference, the second interphase current difference, and the third interphase current difference,
• wherein the set of wave detection currents comprises:
• a first current that flows in the first direction from the first phase to the second phase;
• a second current that flows in the first direction from the first phase to the third phase;
• a third current that flows in the first direction from the second phase to the third phase;
• a fourth current that flows in the second direction from the second phase to the first phase;
• a fifth current that flows in the second direction from the third phase to the first phase;
• and
• a sixth current that flows in the second direction from the third phase to the second phase, wherein the current detection circuit is configured to detect the first to sixth currents, and
• wherein the first interphase current difference is a difference between the first current and the fourth current, the second interphase current difference is a difference between the second current and the fifth current, and the third interphase current difference is a difference between the third current and the sixth current,
• wherein the controller is configured to:
• detect a position of a rotor of the three-phase motor, based on a largest interphase current difference among the first interphase current difference, the second interphase current difference, and the third interphase current difference;
• and
• determine the initial energization pattern used in the initial driving with reference to the detected position of the rotor as a basic position, and
• wherein the controller is configured to:
• determine an addition parameter to be added to the basic position, based on the magnitude relationship among the first interphase current difference, the second interphase current difference, and the third interphase current difference;
• and
• determine the energization pattern used in the initial driving, based on a result of adding the addition parameter.

A control method for controlling a drive circuit configured to drive a three-phase motor, the control method comprising:

• detecting, by a current detection circuit, a current flowing through the three-phase motor by driving of the drive circuit;
• and
• controlling, by a controller, the drive circuit based on the detected current,
• wherein the three-phase motor has a first phase, a second phase, and a third phase,
• wherein the control method further comprises:
• controlling, by the controller, when the three-phase motor is stationary, the drive circuit to sequentially energize two of the first phase, the second phase and the third phase to create an energization pattern of a set of wave detection currents that sequentially flows in a first direction from the drive circuit to a first interphase between the first phase and the second phase, a second interphase between the second phase and the third phase, a third interphase between the third phase and the first phase, then in a second direction from the first interphase, the third interphase, and the second interphase;
• obtaining, by the controller, from the set of wave detection currents detected by the current detection circuit, a first interphase current difference, a second interphase current difference, and a third interphase current difference, wherein:
• the first interphase current difference is a difference between wave detection currents in the first direction and the second direction in the first interphase;
• the second interphase current difference is a difference between wave detection currents in the first direction and the second direction in the second interphase;
• and
• the third interphase current difference is a difference between wave detection currents in the first direction and the second direction in the third interphase;
• and
• determining, by the controller, an initial energization pattern used in initial driving of the three-phase motor, based on a magnitude relationship among the first interphase current difference, the second interphase current difference, and the third interphase current difference,
• wherein the set of wave detection currents comprises:
• a first current that flows in the first direction from the first phase to the second phase;
• a second current that flows in the first direction from the first phase to the third phase;
• a third current that flows in the first direction from the second phase to the third phase;
• a fourth current that flows in the second direction from the second phase to the first phase;
• a fifth current that flows in the second direction from the third phase to the first phase;
• and
• a sixth current that flows in the second direction from the third phase to the second phase, wherein the current detection circuit is configured to detect the first to sixth currents, and
• wherein the first interphase current difference is a difference between the first current and the fourth current, the second interphase current difference is a difference between the second current and the fifth current, and the third interphase current difference is a difference between the third current and the sixth current,
• wherein the control method further comprises:
• detecting, by the controller, a position of a rotor of the three-phase motor, based on a largest interphase current difference among the first interphase current difference, the second interphase current difference, and the third interphase current difference;
• and
• determining, by the controller, the initial energization pattern used in the initial driving with reference to the detected position of the rotor as a basic position, and
• wherein the control method further comprises:
• determining, by the controller, an addition parameter to be added to the basic position, based on the magnitude relationship among the first interphase current difference, the second interphase current difference, and the third interphase current difference;
• and
• determining, by the controller, the energization pattern used in the initial driving, based on a result of adding the addition parameter.