Patent ID: 8278910

Claim:
A phase locked loop (PLL) for controlling a motor, comprising: a first feedback loop; and a second feedback loop, wherein the first feedback loop includes an oscillator configured to generate a signal having a frequency corresponding to an input voltage to output the generated signal, a first phase comparator configured to output a first phase difference signal corresponding to a phase difference between the signal output from the oscillator and an input signal, and a first smoothing filter configured to smooth the first phase difference signal to output the smoothed signal as the input voltage to the oscillator, and the second feedback loop includes a second phase comparator configured to output a second phase difference signal corresponding to a phase difference between a signal derived from the motor and having a frequency corresponding to a rotational speed of the motor and the input signal, an adder configured to add the first phase difference signal and the second phase difference signal to output the resultant signal, and a second smoothing filter configured to smooth the signal output from the adder to output the smoothed signal to the motor.