Electric lamp and discharge devices: systems – Current and/or voltage regulation – Automatic regulation
Patent
1990-08-16
1991-09-24
Mis, David
Electric lamp and discharge devices: systems
Current and/or voltage regulation
Automatic regulation
315151, 315DIG7, H05B 4114
Patent
active
050516663
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a circuit for starting and operating a gas discharge lamp.
A gas discharge lamp is a lamp, which emits light in an electric discharge in the gas of the gas discharge lamp. In the present context, the term "gas discharge lamp" is a generic term comprising all lamps different from incandescent lamps, such as conventional gas discharge lamps, fluorescent lamps, halide lamps and arc lamps.
Common to all gas discharge lamps is the distinct shift in the characteristic of the gas discharge lamp, when the lamp is shifted from its off-state to its on-state and further the requirement of the gas discharge lamp of exceeding a threshold of electric energy supply for switching the gas discharge lamp from its off-state to its on-state. In its off-state, the gas discharge lamp represents a high electric impedance, whereas in its on-state the gas discharge lamp represents a basically resistive load or is to be considered equivalent to a resistance of finite value. Since the electric resistance represented by the gas discharge lamp in its on-state is a decreasing function of the RMS (root mean square) current supplied to the lamp, the lamp has to be connected with a ballast impedance in series with the lamp itself in order to limit the current supply to the lamp when the lamp is in its on-state on a constant voltage supply such as a mains supply. From the above, it is further understood that a starting circuit has to be provided in order to supply sufficient energy in excess of the above mentioned threshold for shifting the gas discharge lamp from its off-state to its on-state.
Several ballast and starter circuit configurations of passive and active circuit configurations are known in the art. Common to the passive circuit configurations of the ballast and starter circuits is the well-known ignition problem resulting in the emission of light flashes prior to the shift of the gas discharge lamps from their off-state to their on-state, as the passive circuit configurations are not able to positively shift the gas discharge lamps from their off-state to their on-state, and the unstable emission of light from the gas discharge lamps often perceived as a constant flickering of the light emitted.
A particular type of gas discharge lamp is a high power discharge lamp, such as a metal vapour lamp, a halide lamp, arc lamp, etc. In the present context, the term "high power gas discharge lamp" means a gas discharge lamp, which in its operating state or on-state receives power in excess of 200 W such as 300 W-2 kW, e.g. 350 W-1.2 kW from its ballast circuit. A highly relevant application of such high power gas discharge lamps is within the field of street-lighting. Thus, high power halide lamps are often used for enlightening highways, etc. These high power halide lamps used for street-lightning have hitherto been supplied from passive starter and ballast circuits as no commercially successful active starter and ballast circuit configuration has yet been available.
Thus, there is a need for an active circuit for starting and operating a gas discharge lamp, particularly a high power gas discharge lamp, which active circuit on the one hand eliminates the well-known slow starting and light-flickering problems of the passive ballast and starter circuit configurations, and the problems of restarting a halide lamp, which has been powered from the passive ballast and starter circuit and consequently been heated to an elevated temperature and is to be restarted or reignited after e.g. a mains supply failure, and which active circuit on the other hand is of a fairly simple and reliable circuit configuration and may be implemented in an inexpensive and lightweight structure, which compared to conventional, passive ballast and starter circuit configurations is much leighter, e.g. of a weight constituting merely 20-30% of the weight of the passive circuit configuration, however, is not more expensive than the corresponding passive ballast and starter circuit.
This need is fulfilled by a circuit according to the pr
REFERENCES:
patent: 4928038 (1990-05-01), Nerone
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