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:
Nov. 21, 1995
Filed:
Jun. 27, 1994
Roger Peppiette, Shrewsbury, MA (US);
Alberto Bilotti, Florida, AR;
Allegro Microsystems, Inc., Worcester, MA (US);
Abstract
A bridge circuit, intended for use as a PWM driver of an inductive load, includes at least one source driver transistor connected in series totem-pole fashion with a sink driver transistor. A base resistor is connected from base to emitter of one of the driver transistors. This totem pole circuit is connected across a pair of DC supply conductors. A protective fly-back diode is connected across the one driver transistor. An auxiliary resistor is connected from the base of the auxiliary transistor to the emitter of the one driver transistor. When a fly-back diode across the one driver transistor conducts, the one driver transistor tends to conduct in the reverse direction and to store charge that in a subsequent period leads to shoot-through currents through the source and sink drivers. The auxiliary transistor turns on only when the fly-back diode conducts and shunts the base-collector of the source transistor, preventing its turning on and storing charge, and thus preventing potentially damaging shoot-through current through the driver transistors. The added auxiliary components do not cause additional power being drawn from the supply source, and therefore do not cause additional heating in the integrated circuit in which the bridge circuit may be formed. A pair of such half wave totem pole circuits may be paralleled to form a full wave bridge.