Time capture based resolver to digital converter

A resolver to digital converter system, comprising:

• a reference winding attached to a rotor, the reference winding configured to be excited by a reference AC signal having a known frequency;
• first and second output windings perpendicularly attached to a stator, electromagnetically coupled to the reference winding, and configured to induce first and second output signals having amplitudes related to a rotary angle of the rotor;
• and
• a controller circuit, comprising:
• first and second crossing detectors configured to detect first and second start time points of the first or second output signals, respectively,
• first and second slope generators configured to generate first and second linear signals at first and second start time points, respectively;
• first and second comparators configured to compare the first and second output signals with the corresponding first and second linear signals, respectively,
• first and second event capture devices configured to record first and second time intervals from the corresponding first and second start time points to the first and second stop time points, wherein magnitudes of the first and second output signals are substantially equal to magnitudes of the corresponding first and second linear signals at the stop time points, and
• a processor configured to convert the first and second time intervals to values proportional to a sine and a cosine of the rotary angle of the rotor, and further convert to a value of the rotary angle.

A rotary angle measurement method using a time capture based resolver, comprising:

• applying a reference AC signal having a known frequency to a reference winding of the resolver to generate first and second output signals from first and second output windings of the resolver, wherein the first and second output windings are electromagnetically coupled to the reference winding;
• detecting a time when a magnitude of the first output signal becomes zero as a start time point of an event capture;
• comparing a pre-determined reference signal with the first output signal and set another time as a stop time point of the event capture when magnitudes of the pre-determined reference signal and the first output signal are substantially same, wherein a time interval is generated by the start time point and stop time point of the event capture;
• and
• processing the time interval to generate a sine value of the rotary angle.