Electric power conversion systems – Current conversion – Using semiconductor-type converter
Reexamination Certificate
1998-10-14
2001-02-27
Wong, Peter S. (Department: 2838)
Electric power conversion systems
Current conversion
Using semiconductor-type converter
C363S037000, C363S069000, C363S089000
Reexamination Certificate
active
06195276
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to synchronous rectifier devices for alternators.
BACKGROUND OF THE INVENTION
It is clear that motor vehicles will in the future need more and more electrical energy to operate under optimal conditions in order to comply with new legislation that will come into force in the next few years, in particular concerning pollution.
The invention proposes a rectifier device that contributes to these objectives and which in particular improves the efficiency and the output of an alternator by reducing rectifier losses and iron losses in the stator and the rotor. The device proposed by the invention also reduces magnetic noise from the alternator by preventing non-linear switching of low-level current.
It is standard practice to use for rectifying the output voltage of a motor vehicle multiphase alternator Graetz full-wave rectifier bridges comprising switching circuits controlled synchronously with the voltages of the various phases of the armature.
In this connection reference is made to patent applications EP-665.637 and EP-762.596.
The switches used are generally enriched N-channel insulated gate transistors (usually called MOSFET). Compared to Graetz bridges using diodes, bridges using switches have the advantage of reducing the direct voltage drop at their terminals.
However, a rectifier bridge of the above kind for motor vehicles operates in an electrical environment subject to very high levels of interference and this can lead to irregularities in the controlling of the switches.
An object of the invention is to provide a rectifier device that mitigates these drawbacks.
The device proposed by the invention also has the advantage of being very low in cost and of being capable of withstanding high temperatures.
DISCUSSION OF THE INVENTION
According to the invention there is provided a device for rectifying the output voltage of a multiphase alternator including a controlled switch Graetz bridge adapted to be connected to different phase lines of the alternator, and control means for controlling said switches to generate a rectified voltage, wherein said control means include a diode type component Graetz bridge which generates signals for controlling the switches of the controlled Graetz bridge.
The diode type components are advantageously the base-emitter junctions of bipolar transistors.
For example, the emitters of said bipolar transistors are connected to the phase lines of the alternator and their collectors are connected to circuits for shaping the collector voltages or currents for controlling the switches of the switch bridge.
In a first embodiment the bases of the two transistors whose emitters are connected to the same phase line are connected between ground and the rectified output of the controlled switch bridge.
In a different embodiment the device includes a voltage adjusting circuit to the terminals of which are connected the bases of two transistors whose emitters are connected to the same phase line.
For example, the voltage adjusting circuit advantageously includes variable impedance means and in particular variable resistance means.
The device preferably includes diodes for protecting the base-emitter junctions of bipolar transistors.
The controlled switches are preferably of the MOSFET type.
For example, the means for shaping the collector voltages or currents that control the gates of the positive switches of the Graetz bridge include voltage offsetting means.
REFERENCES:
patent: 4186435 (1980-01-01), Cailloux
patent: 4348630 (1982-09-01), Boenig et al.
patent: 4412169 (1983-10-01), Dell'orto
patent: 4456870 (1984-06-01), Rodari
patent: 4501933 (1985-02-01), Siligoni et al.
patent: 4507525 (1985-03-01), Siligoni et al.
patent: 5444291 (1995-08-01), Paparo et al.
patent: 5449936 (1995-09-01), Paparo et al.
patent: 0 665 637 (1995-08-01), None
patent: 0 762 596 (1997-03-01), None
French Search Report dated Jun. 4, 1998.
Morgan & Finnegan , LLP
Valeo Equipments Electriques Moteur
Vu Bao Q.
Wong Peter S.
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