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:
Apr. 28, 1987
Filed:
Dec. 23, 1985
John P Hoffman, Peoria, IL (US);
Weldon L Phelps, Dunlap, IL (US);
Caterpillar Inc., Peoria, IL (US);
Abstract
A hybridized solenoid driver circuit includes a first and second current sensing resistor. The first current sensing resistor is disposed within the flyback current path of the windings of an electrically actuated solenoid and provides a signal proportional to the flyback current only. Control of the solenoid current is effected by operation of a power transistor to controllably connect and disconnect the solenoid from the power supply at a preselected duty cycle. Operation of the driver circuit in the energization mode has no effect on the first current sensing resistor. Conversely, the second current sensing resistor is disposed within the energization current path and provides a signal proportional to the energization current only. Operation of the driver circuit in the flyback mode has no effect on the second current sensing resistor. A summing amplifier receives the first signal directly from the first current sensing resistor as it is referenced to ground; however, the second current sensing resistor is referenced to positive battery and the second signal must be passed through a current mirror prior to delivery to the summing amplifier. The signal provided by the summing amplifier is used by a control circuit to maintain the solenoid current at a desired level by constantly adjusting the duty cycle of a biasing signal delivered to the power transistor.