EP0502273A2
Expired / Lapsed
EP
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Discharge lamp and method of operation
Assignee: General Electric Co
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Filing: 1991-07-29
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Granted: —
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Expires: 2011-07-29
Abstract
Abstract Miniature high pressure arc lamps containing a substantial pressure of xenon, in addition to metal halide and mercury, can provide instant light at turn-on and are suitable for automotive headlamps. The xenon aggravates convection which causes arc-bowing and overheating of the envelope above the arc. By operating the lamps on unidirectional current upon which a frequency-modulated high frequency ripple has been imposed, acoustic resonance is used to straighten out the arc. The use of unidirectional current permits a reduction in cost and size of the ballast control circuits operated from auto storage battery. Frequency modulation of the ripple broadens the band allowing acoustic straightening of the arc. Additional control of the arc plus reduction of cataphoresis may be achieved through a horizontal magnetic field at the arc, transverse to current flow. <IMAGE>
Inventors
- 👤 Gary Robert Allen
- 👤 John Martin Davenport
- 👤 Joseph Michael Allison
- 👤 Richard Lowell Hansler
- 👤 Kenneth Steven King
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-09 06:20
CPC Classifications
H; H05; H05B; H05B41/00; H05B41/14; H05B41/36; H05B41/38; H05B41/382; H01; H01J; H01J61/00; H01J61/02; H01J61/12; H01J61/16; H01J61/04; H01J61/10; H01J61/106; H01J61/56; H01J61/82; H01J61/84; H01J61/86; H05B41/26; H05B41/28; H05B41/288; H05B41/292; H05B41/2928; Y; Y02; Y02B; Y02B20/00; Y10; Y10S; Y10S315/00; Y10S315/07
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
150 words
A method of operating a miniature high pressure metal vapor discharge lamp of a kind comprising: a vitreous envelope defining a discharge space having a volume not exceeding approximately 1 cubic centimeter, a cathode and an anode sealed into the envelope and defining an arc gap, and a fill comprising mercury, metal halides and a radiation-emitting gas in a quantity exerting a partial pressure of at least 25% of the total vapor pressure during continuous operation, which method comprises: forcing a unidirectional current having an alternating component in the form of a high frequency ripple imposed thereon causing instantaneous variations in input power across the arc gap, said variations in power being at a frequency selected in a preferred band within the range from 20 kHz to 200 kHz, said band being one in which acoustic resonance excites arc-straightening modes which reduce the effects of gravity-induced convection in the fill.
Claim 2
Dependent Claim
42 words
The method of claim 1 wherein said preferred band is one in which acoustic resonance excites a mode effective to reduce gravity-induced bowing of the arc, lower the hot spot temperature, raise the cold spot temperature, and reduce cataphoresis in the lamp.
Claim 3
Dependent Claim
41 words
The method of claim 1 wherein the alternating component of the current through the lamp at said selected frequency is frequency-modulated in order to broaden the width of the band of frequencies in which a straight and stable arc is obtained.
Claim 4
Dependent Claim
60 words
The method of claim 1 practiced on a lamp of said kind wherein the arc gap is horizontal, wherein xenon is included in the fill for the radiation-emitting gas, and wherein sodium is included as a halide; and wherein said band is one in which acoustic resonance excites arc-straightening modes which also reduce cataphoresis and its effect on color separation.
Claim 5
Independent Claim
149 words
The method of operating a miniature high pressure metal vapor discharge lamp of a kind comprising: a vitreous envelope defining a discharge space having a volume not exceeding approximately 1 cubic centimeter, a cathode and an anode sealed into the envelope and defining a horizontal arc gap, and a fill comprising mercury, metal halide, and xenon gas in a quantity exerting a partial pressure of at least 25% of the total vapor pressure during continuous operation; which method comprises: initiating ionization across the gap by high voltage pulses, forcing a unidirectional current across the gap at a high level during a starting phase in order to warm up the lamp and reducing said current to a lower level during the run phase, and imposing a high frequency ripple on said current at a modulation depth which is a lower percentage during the starting phase than during the run phase.
Claim 6
Dependent Claim
63 words
The method of claim 5 wherein the current during the start phase is in the range of 2 to 20 times the run current, and wherein the ripple is roughly constant in absolute value throughout start and run phases and has a modulation depth of at least 30% during the run phase in order to assure a wide frequency band of stable operation.
Claim 7
Dependent Claim
139 words
In combination a miniature high pressure metal vapor discharge lamp of a kind comprising: a vitreous envelope defining a discharge space having a volume not exceeding approximately 1 cubic centimeter, a cathode and an anode sealed into the envelope and defining a horizontal arc gap, and a fill comprising mercury, metal halides including sodium, and xenon gas in a quantity exerting a partial pressure of at least 25% of the total vapor pressure during continuous operation; and a source of unidirectional current having a high frequency ripple imposed thereon for operating said lamp, said ripple providing modulation of power to the lamp in frequency bands in which acoustic resonance excites arc-straightening modes, and means providing a horizontal magnetic field at said gap transverse to current flow in order to supplement the acoustic modes in straightening and controlling the arc.
Claim 8
Dependent Claim
29 words
The combination of claim 7 wherein said lamp is mounted in a headlamp reflector assembly and the magnetic field is provided by permanent magnetic means fastened to the assembly.
Claim 9
Dependent Claim
86 words
The combination of claim 8 wherein the ripple-modulated unidirectional current supplied to the lamp is several times greater during a start phase for warming up the lamp than during the run phase of operation that follows it, and electomagnetic means for opposing the permanent magnetic field at said gap, said electromagnetic means being energized by the lamp current whereby to neutralize at least in part the permanent magnetic field and avoid driving the arc down against the lower wall of the lamp during the start phase.
Claim 10
Dependent Claim
27 words
The combination of claim 9 wherein the electromagnetic means is a wire coil located within the reflector assembly below the lamp and connected in series with it.
Claim 11
Dependent Claim
181 words
An integrated compact discharge headlamp and ballast assembly comprising: a vitreous arctube lamp having a volume less than 1 cubic centimeter, a cathode and an anode sealed therein defining an arc gap in the range of 2 to 5mm, and a fill comprising xenon in a quantity exerting a partial pressure of at least 25% of the total vapor pressure in operation, a headlamp reflector within which said arctube is horizontally mounted on a fore and aft axis with the gap located near the focal point, starting means supplying high voltage pulses to inionize the gap and initiate current flow in the lamp, circuit means supplying unidirectional current to said lamp, said current having a high frequency ripple component imposed thereon for exciting arc-straightening acoustic resonance modes in said lamp, and timing and control means providing a higher current through said lamp during a start warm-up phase than during the run phase and increasing the modulation depth of the ripple as the current is decreased, said various means being combined and contained in a portion of the headlamp and ballast assembly.
Claim 12
Dependent Claim
26 words
An assembly as defined in claim 11 including means to frequency-modulate the high frequency ripple in order to broaden the frequency range of the arc-straightening modes.
Claim 13
Dependent Claim
30 words
An assembly as defined in claim 11 including means for creating a horizontal transverse magnetic field at said gap to supplement the acoustic straightening of the arc and reduce cataphoresis.
Claim 14
Dependent Claim
39 words
An assembly as defined in claim 11 including memory circuit means responsive to the time interval of lamp extinguishments of short duration, said memory circuit means reducing the duration of the high current starting phase according to said interval.
Claim 15
Dependent Claim
43 words
An assembly as defined in claim 11 doubled and made into a dual headlamp unit having high and low beams, two starting means being provided, one for each beam lamp, and a single circuit means being provided to supply current to either lamp.
References Cited (Backward Citations)
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