Electric lamp and discharge devices: systems – Condenser in the supply circuit – Condenser in shunt to the load device and the supply
Patent
1993-04-05
1995-03-07
Pascal, Robert J.
Electric lamp and discharge devices: systems
Condenser in the supply circuit
Condenser in shunt to the load device and the supply
315240, 315209R, 315227R, 315242, 315244, 315362, H05B 3700
Patent
active
053961528
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to an electrical circuit for the pulsed operation of high-pressure gas-discharge lamps.
BACKGROUND
It has already been known for a long time that the photometric parameters of gas discharge lamps can be improved substantially with the aid of a pulsed supply current. These methods have gained particular attention in sodium vapor high-pressure lamps, in which the color temperature can be raised from approximately 2000 to above 3000K by strobing. At the same time, an improvement in color reproduction is possible. German Patents DE-PS 26 57 824 and DE-PS 28 25 532 refer to these subjects.
When sodium vapor discharge lamps are operated with a plurality of metal vapors, bipolar impulses must be used, in order to prevent separation phenomena.
The nature of the strobe pulses, their shape, the pulse width, the duty factor, the rise and the height have a decisive influence on the attainable photometric parameters. In most versions, work is preferably done with relatively wide pulses (approximately 100 to 200 .mu.s) and duty factors of approximately 0.2, with repetition rates below 500 Hz, as described in German Patent DE-PS 36 36 901.
At frequencies above 500 Hz, the discharge system has a tendency to develop resonant phenomena, which are expressed in the form of severe arc instabilities and losses in light yields (German Patent DE-PS 31 22 183). It is also known for the pulse geometry and pulse shaping to be formed in such a way, when electronic ballasts are used, that the pulses have a rapid transition from the cooling phase to the state of a predetermined pulse output, a prolonged operative time at that level, and a rapid return to the state of the cooling phase. For pulse shaping, a multiple-member delay line is proposed, comprising capacitive and inductive components. Experiments have shown that the optimal pulse width for sodium vapor discharge lamps is between 100 and 200 .mu.s, so that if delay lines are used for pulse shaping, a suitable electronic ballast would be very expensive in terms of components and would be large in volume.
In principle it can be stated that generating relatively wide pulses of appropriate height makes major demands of ballast technology, because large quantities of energy must be stored and switched.
Electrical circuits for the pulsed operation of high-pressure gas-discharge lamps are known for instance from German Patent Disclosure DE-OS 36 41 070, German Patent DE-PS 35 40 985, and German Patent DE-PS 26 57 824.
A substantial disadvantage of these electrical circuits is the major technological effort and expense entailed in making them, and the great losses that must sometimes be expected in the current-limiting components. Moreover, a constant load can be supplied only by expanding the circuit, which is expensive.
THE INVENTION
It is an object of the invention is to create a electrical circuit for high-pressure gas-discharge lamps that enables pulsed operation at a sinusoidal holding load, at little technological effort or expense.
Briefly, according to the invention, for generating the strobe pulses, one or more reactive impedances are provided located as energy storing means in series with one or more switch elements, parallel to at least one of the reactive impedances that are connected in series to the high-pressure gas-discharge lamp.
The series circuit comprising a reactive impedance or impedances and a switch element or elements comprises either electromechanical or electronic switch.
It can be stated that even conventional half-bridge circuits with a serial resonant circuit can be employed by supplying pulsed discharges, if success is achieved in suddenly increasing the energy furnished by the half-bridge circuit at the moment of pulsing. This is achieved with the electrical circuit proposed.
The exemplary circuit introduced here requires virtually no additional expense over that for conventional half-bridge circuits. All the necessary functions for the pulsed operation, such as ignition, holding load supply and strobin
REFERENCES:
patent: 2462371 (1949-02-01), Engle
patent: 4442380 (1984-04-01), Adachi
patent: 4477796 (1984-10-01), Kearsley
patent: 4525651 (1985-06-01), Ahlgren
patent: 5289083 (1994-02-01), Quazi
Pascal Robert J.
Patent-Treuhand-Gesellschaft fur elektrische Gluhlampen m.b.H.
Ratliff Reginald A.
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