The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jun. 11, 1991
Filed:
Jun. 12, 1989
John M Miller, Saline, MI (US);
James E Fenton, Ann Arbor, MI (US);
Harold G Spring, Garden City, MI (US);
Ford Motor Company, Dearborn, MI (US);
Abstract
A method and apparatus for controlling field current in an alternator maintains the alternator output voltage at a defined level and substantially suppresses transients in the event the alternator is disconnected from a load. A pair of MOS Insulated Gate Bipolar Transistors (MOSIGBT's) are connected one in series and one in parallel with the alternator field winding and current is provided to the field winding through the series connected regulator transistor as needed to maintain the alternator output voltage. The field current is auto-commutated through the parallel connected transient suppression transistor when the regulator transistor is off. When the alternator is disconnected from a load, both transistors are switched off in a controlled manner to discharge the field winding energy at a high voltage and at an accelerated rate within the parallel connected transistor. The series connected transistor is nearly intantaneously turned off to remove the source of field current and the parallel connected transistor is 'ramped' off or turned off at a controlled rate to act as a controlled resistance and thereby dissipate the field energy at a high voltage level. By dissipating the field energy at a high voltage level, the dissipation time is substantially reduced as compared to prior art arrangements. The present invention is generally applicable to alternator circuits and is particularly applicable to automotive battery charging systems.