Circuit apparatus for measuring the primary voltage of an ignition coil

US5075627A · kind A · utility

Assignee

• Robert Bosch GmbH · DE

Inventors

• Bernd Bodig · Leinfelden, DE
• Achim Herzog · Backnang, DE
• Klaus Hueser · Stuttgart, DE

Key dates

• Filing date: Mar 8, 1990
• Grant date: Dec 24, 1991
• Expiry date: Mar 8, 2010

Classification

• Technology area (CPC F): Mechanical Engineering; Lighting; Heating
• CPC primary: F02P17/12
• WIPO field: Engines, pumps, turbines
• WIPO sector: Mechanical engineering

Abstract

The voltage developed by a primary winding of an ignition coil is supplied to a voltage divider for furnishing an analog signal of reduced amplitude for evaluation on an analog basis, which reduced amplitude analog signal is averaged by a capacitor connected between the voltage divider tap and ground. The capacitor eliminates the undesired effect of voltage spikes, but is not large enough to interfere with the measurement of voltages exceeding the ignition-initiating primary winding voltage value. The same reduced primary winding voltage is supplied through an input resistor to one input of a differential amplifier connected to operate as a switch having hysteresis and having a reference voltage applied to it such that the output will be the provision of a steady voltage having a duration corresponding to the spark discharge duration, for subsequent digital evaluation. The tap of the voltage divider that provides the analog output voltage for the system is subjected to a clamping action provided by another voltage divider of low ohm value connected across a 5-volt source and having its tap connected to the tap of the first mentioned voltage divider by a diode, so that primary windi…