Patent ID: 8482232

Claim:
A motor drive circuit configured to supply drive currents to drive coils with a plurality of phases of a motor to drive the motor, comprising: a trapezoidal wave signal generation circuit configured to output a trapezoidal wave signal whose inclination is changed with a rotation speed of the motor or a target rotation speed of the motor; a plurality of output transistors configured to output the drive current to the drive coils, respectively, in accordance with the trapezoidal wave signal; and an amplifier circuit configured to amplify the trapezoidal wave signal in accordance with the rotation speed or the target rotation speed, to be supplied to each of the plurality of output transistors, wherein the trapezoidal wave signal generation circuit includes a current supply circuit configured to supply a charging/discharging current for charging/discharging a capacitor, in accordance with the rotation speed or the target rotation speed, and the trapezoidal wave signal generation circuit is configured to generate the trapezoidal wave signal including an inclination part whose inclination is according to the inclination of rising or falling of a voltage across the capacitor, wherein the amplifier circuit is configured to amplify the trapezoidal wave signal in proportion to the rotation speed or the target rotation speed, and wherein the current supply circuit is configured to supply the charging/discharging current in accordance with an increase in the rotation speed or the target rotation speed, the charging/discharging current increasing more greatly as compared to an increase in proportion to an increase in the rotation speed or the target rotation speed.