Method and apparatus for providing the lock of a phase-locked loop system from frequency sweep

Claim 1

A circuit for producing a drive signal for starting and operating a polyphase motor having a back emf in a floating coil, comprising: a source providing an initial reference voltage; a source of clock pulses of successively decreasing periods; a voltage controlled oscillator having an input for receiving an input voltage and having a VCO output, said voltage controlled oscillator having a resynchronizing input for reinitiating said VCO output on each clock pulse of said source of clock pulses; a period comparator for comparing the period of said clock pulses to the period of said VCO output; a phase comparator for comparing the phases of the back emf and said VCO output; first, second, and third switches controlled by said period comparator; said first switch for switching the input of said voltage controlled oscillator from said initial reference voltage to said output of the phase comparator when the period of said clock pulses becomes less than the period of said VCO output; said second switch for switching from said clock pulses to said VCO output to provide said drive signal when the period of said clock pulses becomes less than the period of said VCO output; and said third switch for disabling said resynchronizing input from said clock pulses when the period of said clock signal becomes less than the period of said VCO output.