Patent ID: 7154245

Claim:
A circuit for controlling the phase current waveform in a step motor comprising: a set point generator connecting with a PWM OSCILLATOR for providing FRONT-SLOPE and SIGN data to said PWM OSCILLATOR; a BRIDGE CONTROL LOGIC connecting with said PWM OSCILLATOR and an H BRIDGE, said BRIDGE CONTROL LOGIC thereby controlling step motor phase current through said H BRIDGE to a step motor coil to prevent occurrence of harmonics of said operating current frequency relative to said phase current waveform; wherein said controlling of said step motor phase current comprises: providing a step motor operating current defining an operating current waveform and an operating current frequency; connecting a pulse width modulator signal with said step motor operating current; determining a number of edges comprising said operating current waveform; decreasing said operating current frequency when said number of edges exceeds a predetermined value; and increasing said operating current frequency when said number of edges is less than said predetermined value.