Ignition system with overvoltage and excess current protection

US4244344A · kind A · utility

Assignee

• Robert Bosch GmbH · DE

Inventors

• Peter Werner · Wiernsheim, DE
• Werner Jundt · Ludwigsburg, DE
• Herman Roozenbeek · Schwieberdingen, DE
• Bernd Bodig · Leinfelden, DE

Key dates

• Filing date: May 17, 1979
• Grant date: Jan 13, 1981
• Expiry date: May 17, 1999

Classification

• Technology area (CPC F): Mechanical Engineering; Lighting; Heating
• CPC primary: F02P3/0552
• WIPO field: Engines, pumps, turbines
• WIPO sector: Mechanical engineering

Abstract

In a known ignition system, the emitter-collector circuit of the ignition transistor is connected in series with the primary winding of the ignition coil and with a precision resistor. When the voltage across the latter exceeds a predetermined value, an auxiliary transistor is switched to a conductive state. The emitter-collector circuit of the auxiliary transistor is connected to the base of the ignition transistor and, when conductive, prevents further increases of current through the primary winding of the ignition coil. To protect this circuit, a series circuit including two Zener diodes is connected between the base and collector of the ignition transistor. Further, a voltage divider is connected in parallel with the emitter-collector circuit of the ignition transistor and an additional resistor is connected between the base and the emitter thereof. When overvoltages across the primary winding cause breakdown of the Zener diodes, the current through the Zener diodes is blocked from the emitter-collector circuit of the auxiliary transistor either by a diode or by a blocking transistor having an emitter-collector circuit connected in parallel with the base-emitter circuit of the…