AGC circuit for the reduction of harmonics in the drive signal

A drive circuit apparatus for energizing an actuator about a natural resonant frequency, the drive circuit apparatus comprising:

• a counter configured to generate a count sequence from a received clock signal derived from a drive sense signal;
• demodulator means, operatively coupled to the counter as a phase reference, for generating a demodulated drive sense signal in proportion to the received drive sense signal;
• integrator means, operatively coupled to the demodulator means and a reference voltage, for offsetting the demodulated drive sense signal such that the sum of the demodulator means and reference voltage is integrated to a substantially constant signal;
• multiplying digital to analog converter means, operatively coupled to the integrator means and the counter, for generating a substantially bipolar stepped sinusoidal signal, the converter means having a filter and phase adjustor that generates a substantially smooth sinusoidal signal from the substantially bipolar stepped sinusoidal signal.

A method of generating a drive signal for energizing the actuator about a natural resonant frquency, comprising:

• generating a count sequence derived from a drive sense signal;
• generating a voltage level signal from the drive sense signal based on the count sequence;
• deriving a drive signal at substantially constant phase with the drive sense signal from the voltage level signal and based on the count sequence;
• and
• tracking a clock signal phase with the drive sense signal,
• wherein the generating count sequence step comprises generating a clock signal from the drive sense signal with a phase locked loop and subsequently generating a count sequence from the clock signal utilizing a counter.

A method of generating a drive signal for energizing an actuator about a natural resonant frequency, comprising

• generating a count sequence derived from a drive sense signal;
• generating a voltage level signal from the drive sense signal based on the count sequence;
• deriving a drive signal at substantially constant phase with the drive signal from the voltage level signal and based on the count sequence;
• and
• demodulating the drive sense signal based on the count sequence to produce a negative rectified sine wave signal.