Electricity: electrical systems and devices – Control circuits for electromagnetic devices – Systems for magnetizing – demagnetizing – or controlling the...
Patent
1993-01-29
1995-01-03
Pellinen, A. D.
Electricity: electrical systems and devices
Control circuits for electromagnetic devices
Systems for magnetizing, demagnetizing, or controlling the...
123490, 361153, 361 18, 361 41, 361 74, 361194, 323908, F02D 500, G05F 158, H02H 7122
Patent
active
053791789
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method and device for triggering an electromagnetic consumer.
BACKGROUND OF THE INVENTION
The German Printed Patent No. 29 05 900 discloses a device for controlling the de-excitation time of electromagnetic devices, in particular electromagnetic injection valves in internal combustion engines, in which a circuit arrangement having an especially controllable output voltage is connected in series or in parallel to the electromagnetic device. In the case of known devices of this type, the inductive consumer is fed, for example, from a voltage source via a series-connected transistor, which is capable of being controlled by triggering means. A desired, fast current suppression when the transistor is switched off can be achieved by means of a Zener diode, which is wired parallel to the transistor, or rather by a transistor which is operated in a comparable manner with a Zener voltage, which is higher than the operating voltage at the moment of switch-off.
Instead of a separate suppressor device, such a transistor can also be directly provided with a so-called Zener bracketing and, thus, also be operated as a suppressor device. A disadvantage of this known device is that the suppressor device then also becomes unintentionally conductive and, in some instances, is unacceptably thermally stressed when the operating voltage in the case of a switched-off transistor becomes greater than the Zener voltage. This can occur, for example, when there is a so-called load-dump pulse on the operating-voltage line.
SUMMARY OF THE INVENTION
The present invention has the advantages that an imminent overloading of the suppressor device is recognized, and that its destruction can be avoided by switching over the suppressor device as a preventive measure. Switching-over in the sense of the present invention means switching off the suppressor device, or also switching over the threshold voltage value that is characteristic of the suppressor device. The present invention begins with the realization that the suppressor device is always in imminent danger of being destroyed as the result of thermal overloading when, in the switched-off state of the switching element, the operating voltage exceeds the switching voltage ("Zener voltage") of the suppressor device. The present invention achieves its goal in that a dangerous rise in voltage across the operating-voltage line is recognized and, from this is derived a switching criterion for switching over the suppressor device.
A particularly advantageous device for triggering an electromagnetic consumer, which has a series-connected electromagnetic consumer and first switching means with first triggering means for actuating the switching means, and has a suppressor device, comprises voltage comparison means and second switching means, as well as second triggering means. In this case, the voltage comparison means compare the operating voltage to a specifiable setpoint value, and the second triggering means activate the second switching means for the purpose of switching over the suppressor device when the operating voltage exceeds a specifiable voltage value.
In a particularly advantageous exemplified embodiment of the device according to the present invention, a comparator is provided as a voltage comparison means, whose input terminals are supplied with the operating voltage and the voltage of a reference voltage source. Transistors are provided as first and second switching means in the above-mentioned device. The triggering means for the first and second switching means preferably comprise at least one microcomputer.
In an advantageous specific embodiment of the device according to the present invention, the suppressor device comprises a series connection consisting of at least one diode and one Zener diode in connection with the first switching means realized as a transistor.
Furthermore, in another advantageous refinement of the device according to the present invention, the suppressor device comprises a series connection
REFERENCES:
patent: 4776314 (1988-09-01), Krauter
patent: 4949211 (1990-08-01), Edwards
Bielesch Thomas
Graf Herbert
Schwenger Juergen
Wichert Bernd
Zimmermann Werner
Krishnan Aditya
Pellinen A. D.
Robert & Bosch GmbH
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