Electrical transmission or interconnection systems – Vehicle mounted systems – Automobile
Patent
1999-02-06
2000-11-28
Paladini, Albert W.
Electrical transmission or interconnection systems
Vehicle mounted systems
Automobile
307 91, 320DIG11, 322 25, 322 27, 322 28, H02J 716
Patent
active
061539457
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a generator regulator, in particular for regulating the on-board voltage in motor vehicles, which regulates the output voltage of a generator and affects an exciting current flowing over an exciting winding of the generator.
2. Prior Art
A generator for vehicles with a voltage regulator, which is part of a control device, is known from DE 34 02 288 A1. The voltage regulator therein described measures an actual voltage value (output voltage) of the generator and compares it with an internally formed nominal value. In accordance with this comparison, a clocked exciting current is supplied to the exciting winding of the generator via a transistor power end stage.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a generator regulator of the above-described type, which has protection from overloads due to short circuits and the like.
According to the invention the generator regulator for a generator excited with an excitation winding comprises generator and including means for providing a pulsed excitation current that passes through the excitation winding during operation; and turn on and off the excitation current in order to provide a predetermined pulse width for the pulsed excitation current passing through the excitation winding so as to maintain a constant output voltage of the generator.
The means for activating and deactivating the transistor power end stage includes necessarily means for comparing a saturation voltage of the transistor power end stage picked up at a node between the transistor power end stage and the excitation winding with a reference voltage to provide a comparison output and a pulse width modulation circuit for controlling the transistor power end stage to vary the predetermined pulse width of the pulsed excitation current according to the comparison output whereby damage to the transistor power end stage due to short circuits is prevented.
The generator regulator in accordance with the invention offers the advantage that the transistor power end stage controlling the exciting winding is protected against overloads in case of a short circuit or when being operated at low ohmic loads. Because a saturation voltage of a transistor power end stage controlling the exciting winding is compared with a reference voltage, and the pulse width of exciting current is modulated as a function of the result of the comparison, it is advantageously possible to eliminate occurring differences in the output capabilities of the transistor power end stage by regulating the exciting current, and a power loss of the transistor power end stage can be limited.
Advantageous embodiments of the invention ensue from the remaining characteristics mentioned in the dependent claims.
BRIEF DESCRIPTION OF THE DRAWING
The objects, features and advantages of the invention will now be illustrated in more detail with the aid of the following description of the preferred embodiment, with reference to the accompanying sole figure which is a block diagram of a circuit for an output voltage regulator of a generator according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
The circuit arrangement of a voltage regulator 10 of a generator, not shown in detail, for generating an on-board voltage of a motor vehicle is represented in the drawings. The voltage regulator 10 has external terminals B+, DF and B-. An exciting winding 12 of the generator is connected with the external terminals B+ and DF. A freewheeling diode 13 is connected parallel with the exciting winding 12, which picks up a freewheeling current when the inductive load of the exciting winding 12 is switched off. The exciting winding 12 is controlled by means of a transistor power end stage 14 which, for example, can be constituted by a Darlington circuit. In the switched-on state, the transistor power end stage 14 connects the terminal DF with the terminal B-, i. e. with ground. With the transistor power end stage 14 closed, the exciting cu
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patent: 4386310 (1983-05-01), Sievers
patent: 4636706 (1987-01-01), Bowman et al.
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patent: 5093583 (1992-03-01), Mashino et al.
Dr. Guenter Springer: "Bearbeiten Von Lehren An Berif;Ichen Schulen Und Von Ingenieuren" In Fachkunde Elektrotechnik 21, Jan. 1996.
Fiedler Gerhard
Koss Thomas
Nasswetter Guenter
Reisz Egon
Paladini Albert W.
Robert & Bosch GmbH
Striker Michael J.
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