Motor controller and method for controlling motor

1. A motor controller comprising:

an H bridge circuit having switching elements, fly-wheel diodes, and half bridges connected to motor coils provided in the motor;

a current detector that detects motor current flowing in the motor coil;

a zero-cross detector that detects a zero-cross of a back electromotive force voltage of each of the motor coils; and

a controller that operates to control the H bridge circuit to operate in one of operation modes including a charge mode, a high-dissipation mode, a low-dissipation mode and a free mode by activating the switching elements of the H bridge based on the motor current detected by the current detector,

wherein the H bridge circuit increases the motor current flowing in each of the motor coils in the charge mode,

wherein the H bridge circuit operates with high energy dissipation and a flyback pulse of each of the motor coils is induced in the high-dissipation mode,

wherein the H bridge circuit operates with low energy dissipation that is lower than in the high-dissipation mode in the low-dissipation mode,

wherein the H bridge circuit operates to allow the zero-cross detector to detect the zero-cross of the back electromotive force voltage of each of the motor coils after the flyback pulse of each of the motor coils is decreased,

wherein the controller further operates to perform a process including:

controlling the H bridge circuit to switch to the charge mode;

controlling the H bridge circuit to switch to the high-dissipation mode when the zero-cross detector detects that the back electromotive force voltage of the motor coil connected to a phase of the H bridge circuit shortly before the H bridge circuit is zero-crossed;

controlling the H bridge circuit to switch to the low-dissipation mode after a predetermined time has elapsed; and

controlling the H bridge circuit to switch to the free mode when the motor current detector detects that the motor current flowing in the motor coil connected to the H bridge circuit flows in a direction opposite to that in the charge mode.

2. The motor controller according to claim 1 ,

wherein, in the low-dissipation mode, the controller sets one of high-side switching elements located in a direction where the motor current flows and one of low-side switching elements located in a direction opposite to the direction to which the motor current flows, among the switching elements of the H bridge circuit, to a conduction state, and causes current to flow in a closed circuit by energy accumulated in the motor coil, the closed circuit being formed by the high-side switching element and the low-side switching element that are in the conduction state.

3. The motor controller according to claim 1 ,

wherein, in the high-dissipation mode, the controller sets all of the switching elements of the H bridge circuit to a non-conduction state, thus causing current to flow in a closed circuit by energy accumulated in the motor coil, the closed circuit being formed by a high-side fly-wheel diode located in the direction where the motor current flows and a low-side fly-wheel diode located in the direction opposite to that where the motor current flows.

4. The motor controller according to claim 1 ,

wherein the switching elements and the fly-wheel diodes included in the H bridge circuit are of a CMOS type.

5. The motor controller according to claim 1 ,

wherein the current detector includes a current mirror circuit and a comparator.

6. A method for controlling a motor with a motor controller including:

an H bridge circuit having switching elements, fly-wheel diodes, and half bridges connected to motor coils provided in the motor;

a current detector that detects motor current flowing in the motor coil;

a zero-cross detector that detects a zero-cross of a back electromotive force voltage of each of the motor coils; and

a controller that operates to control the H bridge circuit to operate in one of operation modes including a charge mode, a high-dissipation mode, a low-dissipation mode and a free mode by activating the switching elements of the H bridge based on the motor current detected by the current detector,

wherein the H bridge circuit increases the motor current flowing in each of the motor coils in the charge mode,

wherein the H bridge circuit operates with high energy dissipation and a flyback pulse of each of the motor coils is induced in the high-dissipation mode,

wherein the H bridge circuit operates with low energy dissipation that is lower than in the high-dissipation mode in the low-dissipation mode,

wherein the H bridge circuit operates to allow the zero-cross detector to detect the zero-cross of the back electromotive force voltage of each of the motor coils after the flyback pulse of each of the motor coils is decreased,

wherein the method comprises:

controlling the H bridge circuit to switch to the charge mode;

controlling the H bridge circuit to switch to the high-dissipation mode when the zero-cross detector detects that the back electromotive force voltage of the motor coil connected to a phase of the H bridge circuit shortly before the H bridge circuit is zero-crossed;

controlling the H bridge circuit to switch to the low-dissipation mode after a predetermined time has elapsed; and

controlling the H bridge circuit to switch to the free mode when the motor current detector detects that the motor current flowing in the motor coil connected to the H bridge circuit flows in a direction opposite to that in the charge mode.