Circuit for complementing an AC mains voltage, particularly for

Details Circuit for complementing an AC mains voltage, particularly for Circuit for complementing an AC mains voltage, particularly for

1999-04-05

2000-09-12

Vu, David

Electric lamp and discharge devices: systems

Condenser in the supply circuit

Condenser in shunt to the load device and the supply

315 52, 315 71, H05B 3700

Patent

active

061182222

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The present invention relates to a circuit for complementing the supply voltage, particularly for resistive loads. More particularly, the present invention relates to a circuit for complementing the supply voltage that is suitable to be used ahead of a light source such as an incandescent lamp.
It is commonly known that the best light source currently available is constituted by filament lamps, which in optimum conditions (for example a 220 V supply voltage) constitute the cheapest commercially available light sources and offer the best chromatic yield (RA=100).
However, these lamps, which are supplied with a sinusoidal AC voltage at the frequency of 50 or 60 Hz (standard values of the mains), are subject to drawbacks in their use, since they are very negatively affected by any voltage decreases.
It is in fact known that the mains voltage (which is 220 V in Europe and is the rated value of the mains voltage for household use) is rarely usable, since depending on the distance from the distribution points there are voltage decreases due to voltage losses on the lines and to similar factors. In this way, the lamp designed to operate with a rated voltage that is equal to the ideal mains voltage (for example 220 V) is actually often supplied with a distinctly lower voltage.
This drawback is strongly felt in technologically backward countries, where the mains voltage can be affected by decreases, reaching approximately 170 V at the points of use, with a consequent high loss of efficiency equal to approximately 4.5 lumen/watt.
In this case, an incandescent lamp is not used at its best and the amount and quality of the light produced are considerably lower than the potential of the lamp.
Experimentation has in fact shown that in incandescent lamps with a tungsten filament, said filament is designed to operate at the rated mains voltage, but this occurs only for very short periods; accordingly, the frequencies emitted as photons tend to shift, within the spectrum, more towards the infrared than towards the ultraviolet. In this manner, the incandescent lamp used in a known manner uses part of the consumed energy to produce radiation in a range that is beyond the visual spectrum of the human eye, thus producing heat to the detriment of luminous efficiency.
The luminous efficiency of an incandescent lamp, for example a 40-watt lamp, in optimum operating conditions (for example 220 V AC), is approximately 8.5 lumen/watt. As the voltage decreases, for example to 210 V, the efficiency drops to approximately 7.35 lumen/watt. In practice, a loss of approximately 1 lumen/watt for every 10 V of mains voltage decrease is observed.
The decrease in efficiency caused by the decrease in the supply voltage is common to all devices supplied with AC power. For example, in the case of a water heater designed to operate at a preset operating voltage so as to bring water to the boiling temperature (approximately 100.degree. C.), a lower-than-rated supply voltage can decrease the efficiency of the heater to the point of preventing it from reaching the boiling point of water, thus no longer performing the intended task.
Going back to incandescent lamps, in order to fully exploit these lamps it would be necessary to use a transformer or a voltage booster so as to raise the mains voltage to the rated value required by the lamp. The drawbacks of this solution are the cost, bulk, and consumption of these devices, as well as the difficulty in using them in a household environment.
Another drawback of conventional types of incandescent lamps is the high peak current that they must withstand at power-on time. If the lamp is switched on at the peak point of the sinusoidal curve of the AC voltage, and assuming the presence of an optimum rated voltage level (for example 220 V), the current that flows through the filament of the lamp is very high with respect to the current that flows when the lamp is already switched on.
Therefore, assuming that one is at the peak, at 220 V, the effective voltage is much higher and is

REFERENCES:
patent: 4998044 (1991-03-01), Nilssen

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