Drive control circuit for electric motor

A semiconductor device, comprising:

• a drive control circuit that generates a drive signal for driving an electric motor having a permanent magnet and a coil, wherein
• the drive control circuit generates the drive signal based on a positional signal which indicates relative position of a first drive member and a second drive member of the electric motor,
• a signal level of the drive signal becomes a first voltage level in a first interval,
• a signal level of the drive signal becomes alternately the first voltage level and a second voltage level which is different from the first voltage level in a second interval, and
• the coil of the electric motor is not provided with a current in the first interval,
• wherein a length of the second interval is shorter than a length of interval between a point at which a signal level of a timing signal based on the positional signal becomes a fourth level from a third level and a point at which the signal level of the timing signal becomes the third level.

A semiconductor device for driving an electric motor, comprising:

• an original drive signal generator that generates an original drive signal;
• an excitation interval setter that is able, for each half cycle of respective length π in each 2π excitation cycle of the original drive signal, to set an excitation interval to excite coils of the electric motor to either one of a symmetrical interval centered on a center of each half-cycle and an unsymmetrical interval;
• a drive signal shaping circuit that generates a drive signal for driving the electric motor, by validating the original drive signal during the excitation intervals and invalidating the original drive signal during non-excitation intervals other than the excitation interval;
• and
• a clock signal generator that generates a clock signal;
• wherein the excitation interval setter sets the excitation interval utilizing the clock signal.

A drive control circuit for an electric motor, comprising:

• an original drive signal generator that generates an original drive signal;
• an excitation interval setter that is able, for each half cycle of respective length π in each 2π excitation cycle of the original drive signal, to set an excitation interval to excite coils of the electric motor to either one of a symmetrical interval centered on a center of each half-cycle and an unsymmetrical interval;
• and
• a drive signal shaping circuit that generates a drive signal for driving the electric motor, by validating the original drive signal during the excitation intervals and invalidating the original drive signal during non-excitation intervals other than the excitation interval;
• wherein
• the original drive signal generator generates the original drive signal based on a positional signal which indicates relative position of a first drive member and a second drive member of the electric motor;
• and
• the excitation interval setter includes:
• an interval measurer that measures a first level interval representing a length of time for which a periodic timing signal synchronized with the positional signal shows a first level;
• a start time setter that multiplies the first level interval by a first coefficient value which is a positive value less than 1, to derive a first interval;
• an end time setter that multiplies the first level interval by a second coefficient value which is a value greater than the first coefficient value and less than 1, to derive a second interval;
• and
• an excitation interval controller that controls the excitation interval by comparing the first interval with a first level-elapsed interval which represents elapsed time after the timing signal shows a transition from a second level to the first level, and starting the excitation interval at a timing at which the first level-elapsed interval becomes equal to the first interval;
• and comparing the second interval with the first level-elapsed interval, and starting the non-excitation interval at a timing at which the first level-elapsed interval becomes equal to the second interval.

A drive control circuit for an electric motor, comprising:

• an original drive signal generator that generates an original drive signal;
• an excitation interval setter that is able, for each half cycle of respective length π in each 2π excitation cycle of the original drive signal, to set an excitation interval to excite coils of the electric motor to either one of a symmetrical interval centered on a center of each half-cycle and an unsymmetrical interval;
• and
• a drive signal shaping circuit that generates a drive signal for driving the electric motor, by validating the original drive signal during the excitation intervals and invalidating the original drive signal during non-excitation intervals other than the excitation interval;
• wherein
• the original drive signal generator generates the original drive signal based on a positional signal which indicates relative position of a first drive member and a second drive member of the electric motor;
• and
• the excitation interval setter includes:
• an interval measurer that measures a first level interval representing a length of time for which a periodic timing signal synchronized with the positional signal shows a first level, and a second level interval representing a length of time for which the timing signal shows a second level;
• a start time setter that derives a first interval equal to the first level interval multiplied by a first coefficient value which is a positive value less than 1, and a third interval equal to the second level interval multiplied by the first coefficient value;
• an end time setter that derives a second interval equal to the first level interval multiplied by a second coefficient value which is a value greater than the first coefficient value and less than 1, and a fourth interval equal to the second level interval multiplied by the second coefficient value;
• and
• an excitation interval controller that controls the excitation interval by
• comparing the first interval with a first level-elapsed interval which represents elapsed time after the timing signal shows a transition from the second level to the first level, and starting the excitation interval at a timing at which the first level-elapsed interval becomes equal to the first interval;
• comparing the second interval with the first level-elapsed interval, and starting the non-excitation interval at a timing at which the first level-elapsed interval becomes equal to the second interval;
• comparing the third interval with a second level-elapsed interval which represents elapsed time after the timing signal shows a transition from the first level to the second level, and starting the excitation interval at a timing at which the second level-elapsed interval becomes equal to the third interval;
• and
• comparing the fourth interval with the second level-elapsed interval, and starting the non-excitation interval at a timing at which the second level-elapsed interval becomes equal to the fourth interval.