Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Current driver
Reexamination Certificate
2000-03-30
2001-04-17
Cunningham, Terry D. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Current driver
C327S205000, C327S379000
Reexamination Certificate
active
06218873
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a driver stage for switching a load. A typical driver stage is disclosed in Published, Non-Prosecuted German Patent Application DE 196 00 792 A1. Such driver stages are widely used, for example in motor vehicles, for switching small and medium-sized loads, such as light-emitting diodes, small motors, relays etc.
In the known driver stage, a voltage divider containing two resistors is connected in parallel with the switching path of a switching transistor which is connected in series with the load and via which a current flows, by which a current flowing through the switching transistor is reduced in the event of a short circuit. When the driver stage is switched off, a residual current flows from a positive pole of an operating voltage, via a series circuit containing the voltage divider and the load, to a negative pole.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a driver stage for switching a load which overcomes the above-mentioned disadvantages of the prior art devices of this general type, in which if the driver stage is switched off, no superfluous residual current can flow from the positive pole through the load to the negative pole.
With the foregoing and other objects in view there is provided, in accordance with the invention, a driver stage for switching a load, including:
a first pole terminal to be connected to a voltage source supplying an operating voltage and to the load and a second pole terminal to be connected to the voltage source supplying the operating voltage;
a first resistor connected to the second pole terminal;
a switching transistor having a collector, a base and an emitter connected to the first resistor, the collector to be connected to the load, and the first resistor, the switching transistor and the load defining a series circuit connected between the first pole terminal and the second pole terminal;
a second resistor, a third resistor, a fourth resistor, a fifth resistor, and a sixth resistor connected to the second pole terminal;
a driver transistor having an emitter connected to the first pole terminal, a base, and a collector connected first via the sixth resistor to the second pole terminal and second via the fifth resistor to the base of the switching transistor, the base of the driver transistor to receive a control signal for switching the switching transistor;
a short-circuit transistor having an emitter connected to the second pole terminal, a collector connected to the base of the switching transistor, and a base connected via the second resistor to the emitter of the switching transistor and via the third resistor to the collector of the switching transistor; and
a parallel transistor controllable in synchronism with the switching transistor by the driver transistor via the fourth resistor and having a switching path connected between the base of the short-circuit transistor and the third resistor.
In accordance with a concomitant feature of the invention, if the switching transistor is switched off, the parallel transistor blocks a path formed of the first resistor, the second resistor, the third resistor and the load, to an undesirable residual current.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a driver stage for switching a load, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
REFERENCES:
patent: 3752980 (1973-08-01), Dixon et al.
patent: 3822386 (1974-07-01), Gontowski, Jr.
patent: 4791313 (1988-12-01), Kuo et al.
patent: 5258661 (1993-11-01), Banker et al.
patent: 5546043 (1996-08-01), Pollmeier
patent: 5565810 (1996-10-01), Hammel et al.
patent: 19600792A1 (1997-07-01), None
Cunningham Terry D.
Greenberg Laurence A.
Lerner Herbert L.
Nguyen Long
Siemens Aktiengesellschaft
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