Power output stage having a darlington-pair circuit for switching an inductive load, especially the ignition coil of an internal-combustion engine

US5424671A · kind A · utility

Assignee

• Robert Bosch GmbH · DE

Inventors

• Gerd Hohne · Ludwigsburg, DE
• Hartmut Michel
• Lothar Gademann · Rottenburg am Neckar, DE
• Bernd Bodig · Leinfelden, DE

Key dates

• Filing date: May 25, 1993
• Grant date: Jun 13, 1995
• Expiry date: May 25, 2013

Classification

• Technology area (CPC F): Mechanical Engineering; Lighting; Heating
• CPC primary: F02P9/002
• WIPO field: Engines, pumps, turbines
• WIPO sector: Mechanical engineering

Abstract

A power output stage has a Darlington-pair circuit (11, 12) for switching an inductive load, especially the ignition coil of an internalcombustion engine. In order to predetermine the operating mode of the power output stage, a switch (24) is provided which bridges the base-emitter junction of the Darlington-pair circuit (11, 12), is closed in the event of a quick disconnection of the output stage, and is opened in the event of a voltage-limited disconnection of the output stage. A voltage divider, which consists of at least two resistors (16, 18) and bridges the switching junction of the Darlington-pair circuit (11, 12), is connected by means of its pick-off to the junction point between the switch (24) and the base of the Darlington-pair circuit (11, 12), the switch (24) being connected in parallel with a part (18) of the voltage divider. When the switch (24) is open, the Darlington-pair circuit is consequently raised again upon reaching a lower limiting voltage of, for example, 35 volts over the resistor (16), so that, in the case of driving an ignition coil, a spark-free disconnection is achieved. Only a very few, simple and cheap components are required for this purpose.