Rotation speed detection circuit and motor driver apparatus having the same

A motor driver comprising:

• a rotation speed detection circuit;
• a lead angle control circuit which outputs a lead angle control signal for performing lead angle control of a motor based on a digital data signal and an internal clock signal;
• a driver portion which performs the lead angle control in accordance with rotation speed of the motor based on the lead angle control signal and delivers a drive signal for driving the motor, wherein
• the rotation speed detection circuit includes an internal clock generation portion which receives an input of a period signal whose period varies in accordance with rotation speed of the motor and generates the internal clock signal having a predetermined number of pulses in one period of the period signal, and an internal clock counter portion which counts the number of pulses of the internal clock signal for a predetermined period every one period of the period signal and delivers a count value thereof as a digital data signal.

A motor driver with speed servo comprising:

• a rotation speed detection circuit;
• a D/A converter which converts the digital data signal delivered from the rotation speed detection circuit into an analog voltage signal;
• a voltage-to-current converter circuit which converts the analog voltage signal into an analog current signal;
• an acceleration/reduction control pulse signal generation circuit which generates an acceleration control pulse signal and a reduction control pulse signal so that actual rotation speed of the motor agrees with target rotation speed based on the period signal;
• a charge pump circuit which generates charge/discharge pulse current corresponding to the analog current signal based on the acceleration control pulse signal and the reduction control pulse signal;
• a speed control circuit which delivers a speed control signal for controlling rotation speed of the motor based on a torque control signal generated by integral of the charge/discharge pulse current delivered from the charge pump circuit to make DC voltage;
• and
• a driver portion which delivers a drive signal for driving the motor based on the speed control signal, wherein
• the rotation speed detection circuit includes an internal clock generation portion which receives an input of a period signal whose period varies in accordance with rotation speed of the motor and generates the internal clock signal having a predetermined number of pulses in one period of the period signal, and
• an internal clock counter portion which counts the number of pulses of the internal clock signal for a predetermined period every one period of the period signal and delivers a count value thereof as a digital data signal.