Lead angle control circuit, and motor drive device and motor drive system using the lead angle control circuit

A motor drive device configured to drive a motor with a motor drive signal in which a lead angle is controlled, comprising:

• a control signal generating section configured to generate a control signal corresponding to a motor current flowing through the motor;
• an upper limit voltage limit section configured to receive an upper limit voltage and configured to output a lead angle control signal obtained by limiting a maximum value of the control signal to the upper limit voltage;
• a lead angle data generating section configured to generate a relationship line between lead angle data representing the lead angle and the lead angle control signal, and configured to generate the lead angle data based on the relationship line and the lead angle control signal;
• and
• a motor drive signal generating section configured to generate the motor drive signal in which the lead angle is controlled, based on the lead angle data and a position signal representing a rotational position of the motor,
• wherein the lead angle data generating section receives a changing point voltage and a lead angle setting voltage, the changing point voltage being less than the upper limit voltage,
• the relationship line reaches an upper limit point from a lower limit point through a changing point,
• in the changing point, the lead angle control signal is the changing point voltage, and the lead angle data represents the lead angle corresponding to the lead angle setting voltage, and
• in the upper limit point, the lead angle control signal is the upper limit voltage, and the lead angle data represents a maximum lead angle.