Electrical transmission or interconnection systems – Vehicle mounted systems – Automobile
Patent
1998-03-09
2000-01-25
Elms, Richard T.
Electrical transmission or interconnection systems
Vehicle mounted systems
Automobile
361253, B60R 2200
Patent
active
060182024
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an ignition output stage.
BACKGROUND INFORMATION
German Patent Application No. 23 39 896 describes an ignition output stage for internal combustion engines. This primary winding of the ignition coil is connected in series with the interrupter assembly of a switching transistor. The switching transistor is implemented as a Darlington circuit, with a Zener diode connected in parallel to the collector-base system. This Zener diode ensures that the voltage at the interrupter assembly of the switching transistor does not exceed a permissible value. High voltages that represent a danger to the switching transistor occur, in particular, during the transition of the switching transistor interrupter assembly into the off state and are generated by the high voltage transformed to the primary side.
If the collector-emitter voltage reaches the Zener voltage of the base-collector diode, a Zener current flows to the base of the ignition Darlington. This is again switched to the on state so in clamping operation, simultaneously a voltage is present and current flows until the ignition spark on the secondary side of the coil sparks over the coil and the rest of the coil energy flows into the spark gap.
The ignition coil of an ignition circuit is connected with rotating distribution over an ignition distributor to the corresponding ignition spark plug of the internal combustion engine or, with static distribution, directly to the spark plug. In this arrangement very large cable lengths occur between the individual connections, e.g., between the switching transistor and the ignition coil and between the switching transistor and ground and between the triggering circuit of the ignition Darlington and the base of the ignition Darlington. The ohmic resistances and inductances that are present because of the electric cable have an antenna effect, so that during the ignition process the base wiring of the switching transistor is supplied with weak parasitic base current which leads to the ignition voltage only slowly reaching the value necessary for ignition, since the switching transistor is somewhat notched up again by this parasitic current. This effect can be taken into account by using the shortest possible emitter and collector wires or by the use of shielded control wires for the switching transistor base.
SUMMARY OF THE INVENTION
The present invention has an advantage of simply, cost-effectively and very reliably protecting the base wiring of the switching transistor from parasitic effects. In addition, the circuit can be used very well in monolithical integration.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows a first exemplary embodiment of an ignition output stage with internal single-level clamping and short-circuit transistor according to the present invention.
FIG. 2 shows a second exemplary embodiment of an ignition output stage with external, multi-stage clamping and short-circuit transistor.
FIG. 3 shows a third exemplary embodiment of an ignition output stage with internal single-stage clamping and short-circuit transistor.
FIG. 4 shows a clamp voltage curve without short-circuit transistor.
FIG. 5 shows another clamp voltage curve with short-circuit transistor.
FIG. 6 shows a short-circuit transistor integrated monolithically in the ignition Darlington.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a schematic diagram of an ignition output stage with an internal, single-level Zener clamp, as used for internal combustion engine ignition systems. The circuit in FIG. 1 includes ignition coil 1, which is connected on the secondary side to an ignition spark plug that is not shown. The primary winding of ignition coil 1 is connected on one side to voltage supply U.sub.S, for example, the battery of the vehicle that is not shown, and on the other side to ground through power transistor T1. A driver transistor T2 is connected upstream from the power transistor T1 so that a two-stage Darlington transistor results. The collector-emitter junction o
REFERENCES:
patent: 4064415 (1977-12-01), Blackington
patent: 5424671 (1995-06-01), Hohne et al.
patent: 5559661 (1996-09-01), Meinders
Meinders Horst
Schleupen Richard
Elms Richard T.
Robert & Bosch GmbH
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