Resonant frequency tracking and control

A circuit to control driving a resonator, for use in a system that includes a resonator, and a resonator driver to provide resonator drive signals at a resonator drive frequency, and a sensor to sense resonator drive, the circuit comprising:

• a sensor input configured to receive input sensed resonator drive signals corresponding to sensed resonator drive;
• a frequency control output;
• a frequency tracker/controller coupled to the sensor input, and to the frequency control output, including:
• a back-emf estimator to estimate back-emf, including:
• to estimate resonator resistance based at least in part on sensed resonator drive signals from the sensor input, and
• to estimate back-emf, and generate corresponding estimated back-emf signals, based at least in part on the sensed resonator drive signals and the estimated resonator resistance;
• a phase detector to determine a phase difference between the resonator drive signals, and the estimated back-emf signals;
• and
• a frequency controller to generate frequency control signals for output from the frequency control output.

A method of controlling a resonator for operation at a resonant frequency, for use in a system that includes a resonator, and a resonator driver to provide resonator drive signals at a resonator drive frequency, the method comprising:

• sensing resonator drive to provide sensed resonator drive signals;
• generating frequency control signals for input to the resonator driver to track and control resonator drive frequency, including:
• estimating back-emf, including:
• estimating resonator resistance based at least in part on the sensed resonator drive signals, and
• estimating back-emf to generate corresponding estimated back-emf signals, based at least in part on the sensed resonator drive signals and the estimated resonator resistance;
• detecting a phase difference between the resonator drive signals, and the estimated back-emf signals;
• and
• generating the frequency control signals to iteratively adjust the frequency of the resonator drive signals until phase coherent with the estimated back-emf signals, for driving the resonator at or near a resonant frequency (F0).