Sampling bipolar peak detector for sensing a non-symmetrical decay of an AC voltage signal

In a servomotor control system including a resolver integrally coupled to a servomotor and responsive to a periodic excitation signal to provide a return signal indicating the instantaneous angular position of the servomotor, apparatus for determining the validity of the excitation signal comprising:

• a source of said periodic excitation signal having a peak amplitude;
• a source of clock signal, synchronized to said excitation signal;
• a comparator circuit which compares the excitation signal, in amplitude, to a predetermined reference value during each period of the excitation signal and which produces an output signal that is in a first state when the amplitude of the excitation signal is greater than said predetermined reference value and in a second state otherwise;
• and
• state machine means, responsive to the clock signal for determining if the output signal of the comparison means is in one of the first state or the second state for N successive periods of said clock signal, where N is an integer greater than one, to produce an output signal indicating the validity of the excitation signal.

In a servomotor control system including a resolver integrally coupled to a servomotor and responsive to a periodic excitation signal to provide a return signal indicating the instantaneous angular position of the servomotor, apparatus for determining the validity of the excitation signal comprising:

• a source of said periodic excitation signal having a positive and a negative peak amplitude;
• a source of clock signal, synchronized to said excitation signal;
• a source of inverted clock signal which is 180 degrees out of phase with respect to the clock signal;
• first and second comparison means for comparing the excitation signal, in amplitude, to a predetermined reference value during each period of the excitation signal and for producing an output signal that is in a first state when the amplitude of the excitation signal is greater than said predetermined reference value and in a second state otherwise, said first comparison means operating with positive amplitudes and said clock signal and said second comparison means operating with positive amplitudes and said inverted said clock signal;
• first and second state machine means, responsive to the clock signal for determining if the output signal of the comparison means is in one of the first state or the second state for N successive periods of said clock signal, where N is an integer greater than one, to produce a first output signal indicating the validity of the positive portion of said excitation signal and said second state machine means responsive to said inverted clock signal for determining if the output signal of the comparison means is in one of the first state or the second state for N successive periods of said inverted said clock signal, where N is an integer greater than one, to produce a second output signal indicating the validity of the negative portion of said excitation signal;
• and
• means for combining said first and second output signals to generate a third output signal.