Electric lamp and discharge devices: systems – Periodic switch in the supply circuit – Silicon controlled rectifier ignition
Patent
1993-03-12
1994-11-15
Pascal, Robert J.
Electric lamp and discharge devices: systems
Periodic switch in the supply circuit
Silicon controlled rectifier ignition
315307, 315291, 315194, 315DIG5, 315DIG7, H05B 3702
Patent
active
053651510
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a ballast for the pulsed-mode operation of gas discharge lamps. More specifically, it concerns the use of a self-excited or externally controlled half or full bridge circuit, likewise for the pulsed mode operation of gas discharge lamps.
2. Description of the Related Art
Conventional electronic ballasts (EVG) serve both to improve brightness control and to make extended and more sparing ignition of high and low pressure gas discharge lamps (GE) possible. Such electronic ballasts supply a frequency in the range of 20 kHz to 70 kHz to a series resonant load circuit. By changing the frequency of the output voltage of the EVG the load current in the series-resonant circuit can be adjusted continuously and in a stepless manner. The gas discharge lamp that is arranged in the load circuit and has the load current flowing through it can thus have its brightness changed in a stepless manner. At the same time, by the output frequency of the EVG approaching the resonant frequency of the load circuit when the lamp is not ignited, a high voltage can be generated at the lamp, to cause the lamp to ignite.
Whilst such EVG's enable comfortable brightness control and ignition, they are not equally suitable to alter the other characteristics of a gas discharge lamp, such as colour temperature or light output (valued luminous flux, lumen/watt).
This can now be achieved by operating a gas discharge lamp periodically with two dissimilar, substantially different current intensities. On the one hand a high current value is applied to the lamp for a certain period and on the other hand the lamp is allowed a recovery time with a substantially lower holding current.
This cycle is repeated periodically so that averaged over time it is ensured that the lamp remains in the conducting state and takes up the lamp nominal power rating P.sub.N. By changing the duration of the respective time intervals and the amplitude of the current pulses during each respective time interval the colour temperature and light output of the gas discharge lamps, in particular the Na-high pressure lamps, can be changed. To date, however, this change requires that to achieve different current intensities for the main pulse and the substantially lower holding current pulse the chokes arranged in the load circuit be switched over by additional switches. These switches are expensive and complicated.
SUMMARY OF THE INVENTION
To solve the problem illustrated it is therefore proposed by the invention to avoid switching the chokes and to provide only one choke which, however, is provided periodically via at least one switching element or element pair with voltage pulses, the frequency of the voltage pulses being modulatable by means of a control signal. This achieves modulation of the effective reactance of the load circuit whereby the load current, which also flows through the gas discharge lamp, is as it were also modulated.
A further independent solution of the explained problem is found in the use of the circuits mentioned at the beginning for the pulsed-mode operation of gas discharge lamps, preferably with a pulsation frequency in the range of 50 Hz to 1000 Hz, whereby the gas discharge lamp is arranged in series with an inductance in a load circuit.
The idea on which the explained solution is based is that of controlling the momentary operational overloading of the lamps and the holding current phase by way of a frequency change which involves alternative frequency, stepwise or sine-like, i.e. a continuously, periodically formed frequency change. As the mean value the nominal power rating is reached so that the lamp is not thermally overloaded but the light output and its colour temperature can be changed.
If necessary the holding current could also be dispensed with but it is expedient to retain it so that the lamp does not need to be re-ignited after a main current pulse. It also allows a non-sine-like but similarly constituted, in any event continuing frequency change to avo
REFERENCES:
patent: 4277728 (1981-07-01), Stevens
patent: 4373146 (1983-02-01), Bonazoil et al.
patent: 4912374 (1990-03-01), Nagase et al.
patent: 5128593 (1992-07-01), Gilbert
Pabst Wolfgang
Spiegel Norbert
Pascal Robert J.
Ratliff Reginald A.
Tridonic Bauelemente GmbH
LandOfFree
Gas discharge lamp ballast circuit with frequency modulated puls does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Gas discharge lamp ballast circuit with frequency modulated puls, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Gas discharge lamp ballast circuit with frequency modulated puls will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1100033