Brian P Roth

US Patent:

6806675, Oct 19, 2004

Filed:

Oct 4, 2001

Appl. No.:

09/970592

Inventors:

Bing Wang - Coppell TX
Donny R. Walker - Coppell TX
Brian J. Roth - Coppell TX

Assignee:

Abbott Laboratories - Abbott Park IL

International Classification:

H02P 818

US Classification:

318685, 318696, 318254, 318432, 318434, 318700

Abstract:

A stepper motor control circuit reduces ripple current by applying both fast and slow current decays to a motor phase when current is being reduced in the motor phase while following a falling current waveform. The control circuit uses an initial fast decay to reduce a winding current and then switches to a slow decay until a winding current is sampled again. The control circuitry samples a winding current and compares the sampled current to a reference current to determine if current is to be applied or reduced using fast and/or slow decay methods. Different phase current sample circuits allow either constant current sensing or selective current sensing.