Electricity: power supply or regulation systems – Output level responsive – Using a three or more terminal semiconductive device as the...
Reexamination Certificate
2000-03-22
2001-03-20
Wong, Peter S. (Department: 2838)
Electricity: power supply or regulation systems
Output level responsive
Using a three or more terminal semiconductive device as the...
C327S214000, C327S437000, C327S484000
Reexamination Certificate
active
06204652
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to electrical power supply apparatus, especially for the supply of power to electrical equipment fitted in motor vehicles. The invention is applicable in particular, but without limitation, to power supply apparatus for lighting systems that include incandescent light sources or light sources of the light emitting diode type, or electrical systems which are sensitive to variations in the supply voltage.
BACKGROUND OF THE INVENTION
Such lighting systems are supplied from an onboard energy source which is typically the battery of the vehicle. Vehicle batteries used at the present time generally deliver a nominal voltage of around 12 volts. However, it is normal practice to find that there are over-voltages at the terminals of the items of equipment supplied by the battery. These over-voltages may be of short duration, and may not perturb the operation of the apparatus except over a time interval short enough to be acceptable.
However, over-voltages in the power supply network may often be prolonged, especially as a result of the discharge of capacitive elements, or because an alternator regulator is defective. In the absence of any additional regulation of voltage directly at the terminals of the apparatus, the disturbance to the operation of the latter will therefore persist.
In the case of headlights, such a prolonged over-voltage may typically reach 18 volts and can cause the light intensity emitted to be increased. This can infringe photometric regulations and cause dazzling, which is tiresome or even dangerous to drivers coming in the opposite direction.
The over-voltages can also be voluntary, because manufacturers sometimes increase the power distributed in the vehicle in order generally to compensate for the various voltage losses that are linked to the increasing number of items of electrical equipment mounted in a vehicle, such as electrical power assisted steering, electrically governed suspension systems, and so on. In this context, headlights are such that, under these circumstances, they will emit light of too high an intensity, which, apart from the dazzling effects already mentioned above, also involve a considerable shortening of the useful life of filament lamps in the headlights.
In addition, in order to solve the problem of the increase already mentioned above, in the power consumed by the various onboard electrical items of equipment, it has been arranged that the nominal supply voltage delivered by the battery of the vehicle should be substantially increased. Thus, some vehicles have batteries of 24 or 42 volts for example.
The use of existing apparatuses which do not have intermediate adjusting means for the voltage is then excluded, because the voltages delivered at the terminals of such apparatus is too different from the nominal voltage of each respective apparatus, which is of the order of 12 volts.
In the case of filament lamps, which are the type most often used in headlights, it is certainly possible to envisage that the lamps should have a supply voltage corresponding to the battery voltage of the vehicle, of 24 or 42 volts for example. However, the constraints imposed on design and manufacture of the filament (which has to have a very fine double coil so that it can be brought to incandescence, but which must also be quite strong so that it will not be damaged by the supply voltage) has made such lamps expensive and fragile. In addition, the filament of such a lamp is not well adapted to the photometric requirements imposed by certain so-called “free surface” reflectors.
Another solution would consist in the use of a second voltage source which is dedicated to the lighting system, or the use of a specific electrical network for lighting purposes, connected to the battery of the vehicle through a voltage reducer. However, this would involve major complexity and extended length in the wiring network of the vehicle, which is something manufacturers try to avoid, given the high costs involved in wiring.
One solution that can resolve the above mentioned drawbacks linked to persistent or permanent over-voltages or to an increase in the nominal voltages delivered by the vehicle battery, consists in associating with each lamp of a headlight or indicating signal display a voltage regulating apparatus which firstly reduces the voltage to the rated or nominal value of the headlight or indicating light in the case of general supply of the vehicle with a voltage greater than the rated voltage, and secondly, regulates the voltage so as to minimise fluctuations in the voltages that may occur across the lamp.
One such voltage regulating device has been described by the Company Valeo Vision in French patent specification No. FR 2 707 021. In the arrangement described in that document, a n electronic circuit modules the vehicle battery voltage and a periodic voltage with square wave pulses for supplying the lamps of the illumination equipment. The periods of the pulses of the supply voltage are so defined that there mean value is adjusted on a given rated value corresponding to the nominal power supply voltage of the lamps.
DISCUSSION OF THE INVENTION
An object of the present invention is to provide an improvement to this regulating apparatus, in which the current flowing in the load or loads remains essentially constant, so as, in particular, to increase the useful life of the loads and in particular incandescent lamps.
Another object of the invention is to provide a switching and regulating station the structure of which is simple and inexpensive.
According to the invention in a first aspect, apparatus for regulating the supply voltage for an electrical load having a nominal supply voltage, the apparatus being fed from a source of unidirectional voltage of variable value, the apparatus comprising an oscillator generating a rectangular control signal, the cyclic ratio of which varies with the value of the unidirectional voltage when the latter is greater than a given threshold voltage, and further including an interrupter controlled by the said control signal and connected in series with the load across the voltage source, the apparatus being characterised in that it further includes an inductance which is connected in series with the load and a component with unidirectional conduction, in parallel with the series-connected lamp and inductance.
Preferably, the unidirectional conduction component is a second controlled interrupter.
The two controlled interrupters are preferably subjected to the same control signal; they preferably consist of C-MOS transistors, with N channel and P channel respectively; and preferably, the two controlled interrupters are connected in series with the voltage source.
According to the invention in a second aspect, a system for generating the supply for loads mounted in a motor vehicle includes at least one apparatus according to the said first aspect of the invention, for regulating the supply voltage of an associated load.
The system preferably also includes a module for selectively controlling the supply of power to each regulating apparatus.
Preferably, it further includes a module for selectively controlling the power supply of each load by applying to each regulating apparatus an activating signal or a de-activating signal.
The control module preferably consists of a decoder for activating and de-activating signals carried on a common bus.
Preferably, the control module and the regulating apparatuses are part of a common electronic unit.
REFERENCES:
patent: 4902958 (1990-02-01), Cook, II
patent: 5095224 (1992-03-01), Renger
patent: 5289043 (1994-02-01), Marshall et al.
patent: 5414341 (1995-05-01), Brown
patent: 5627460 (1997-05-01), Bazinet et al.
patent: 5757173 (1998-05-01), Agiman
patent: 5808455 (1998-09-01), Schwartz et al.
patent: 5847554 (1998-12-01), Wilcox et al.
patent: 5870296 (1999-02-01), Schaffer
patent: 0 470 750 (1992-02-01), None
patent: 2 707 021 (1994-12-01), None
Albou Pierre
Charret Jean Paul
Leleve Joel
Laxton Gary L.
Morgan & Finnegan , LLP
Valeo Vision
Wong Peter S.
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