Phase difference detection device and method for a position detector

A phase difference detection device for a position detector, said position detector being excited by a predetermined reference signal to generate first and second A.C. output signals, said first A C. output signal having been amplitude-modulated using, as an amplitude coefficient, a first function value corresponding to a position-to-be-detected, and said second A.C. output signal having been amplitude-modulated using, as an amplitude coefficient, a second function value corresponding to the position-to-be-detected, said phase difference detection device comprising:

• a phase shift circuit operatively coupled to said position detector to shift an electric phase of said received first A.C. output signal by a predetermined angle;
• a first circuit operatively coupled to said phase shift circuit and said position detector to perform an operation between an output signal of said phase shift circuit and said second A.C. output signal so as to synthesize a first data signal having an electric phase angle shifted in one of positive and negative directions in correspondence to the position-to-be-detected;
• a second circuit operatively coupled to said phase shift circuit and said position detector to perform an operation between an output signal of said phase shift circuit and said second A.C. output signal so as to synthesize a second data signal having an electric phase angle shifted in other of positive and negative directions in correspondence to the position-to-be-detected;
• and
• a third circuit operatively coupled to said first and second circuit to generate, on the basis of a difference between said first data signal and said second data signal, a signal pulse-width-modulated in accordance with position data indicative of the position-to-be-detected.

A method of detecting a position by use of a position detector, said position detector being excited by a predetermined reference signal to generate first and second output signals, said first output signal having been amplitude-modulated using, as an amplitude coefficient, a first function value corresponding to a position-to-be-detected, and said second output signal having been amplitude-modulated using, as an amplitude coefficient, a second function value corresponding to the position-to-be-detected, said method comprising the steps of:

• receiving said first and second output signals from said position detector;
• forming first and second data signals from said received first and second output signals, said first data signal having an electric phase angle shifted in a positive direction in correspondence to a position-to-be-detected, said second data signal having an electric phase angle shifted in a negative direction in correspondence to said position-to-be-detected;
• measuring an electric phase difference between said predetermined reference signal and said first data signal to obtain first phase data;
• measuring an electric phase difference between said predetermined reference signal and said second data signal to obtain second phase data;
• operating position detection data corresponding to the position-to-be-detected on the basis of said first and second phase data;
• and
• generating a signal pulse-width-modulated in accordance with the position detection data.