Digital, Back EMF, single coil sampling, sensorless commutator system for a D.C. motor

• US 5,672,948 A
• Filed: 11/15/1994
• Issued: 09/30/1997
• Est. Priority Date: 06/14/1993
• Status: Expired due to Fees

• Current Assignee: Cambridge Aeroflo, Inc.
• Original Assignee: Cambridge Aeroflo, Inc.
• Inventors: Cohen, Adam J., Holman, Roger L., Nair, Rajesh M.
• Primary Examiner(s): Sircus, Brian
• Application Number:
  US08/339,827
• Time in Patent Office: 1,050 Days
• Field of Search: 318/254, 318/439, 318/603, 318/138, 388/805, 388/812, 388/813, 388/816, 388/820, 388/928.1
• US Class Current: 318/603
• CPC Class Codes: H02P 6/182 using back-emf in windings

Abstract

A digital, back EMF, single coil, sensorless up/down counter frequency adjustment system for a d.c. motor includes means for detecting the occurrence of a null voltage during the back EMF commutation state of a field coil; counter means for counting in one direction during the back EMF commutation state and for counting in the opposite direction when the null voltage is detected; means, responsive to the counter means, for ascertaining the final count of the counter means; and means, responsive to the means for ascertaining, for adjusting the frequency of initiation of the commutation states when a non-zero count is ascertained for synchronizing the field coil and the rotor.

Claims

1. A digital, back EMF, sensorless commutation system for a d.c. motor comprising:

means for detecting the occurrence of a null voltage during high impedance states of a field coil of the d.c. motor;

counter means for counting in a first direction in a first high impedance state during voltages below the null voltage and for counting in a second direction during voltages above the null voltage;

means for counting in the second direction at a beginning of a second high impedance state until the first occurrence of a null voltage and for thereafter counting in said second direction during voltages below the null voltage and for counting in said first direction during voltages above the null voltage;

means, responsive to said counter means for ascertaining the final count of said counter means; and

means, responsive to said means for ascertaining, for adjusting the frequency of initiating of the commutation states for synchronizing said d.c. motor.