Electronic power circuit for gas discharge lamps
First Claim
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1. A power circuit for starting and operating a gas discharge lamp with ac-voltage, wherein the power circuit is provided with:
- at least a first and a second lamp output terminal between which, in use, the gas discharge lamp is connected,a dc-voltage input, with at least two input terminals,a series connection of at least two switching elements such as, for instance, power transistors, which is connected between the input terminals of the dc-voltage input,a control circuit arranged for delivering control pulses to the switching elements for alternately and not in an overlapping manner bringing said switching elements into conduction,at least one lamp coil which is connected, on the one side, to the junction of said switching elements and which, on the other side, is connected with the first lamp output terminal,at least one resonance capacity, at least comprising one or more capacitors while the resonance capacity is connected, on one side, to the first lamp output terminal and, on the other side, is connected to one or both input terminals,at least one coupling capacity, at least comprising one or more capacitors, the coupling capacity having a capacity value which is considerably greater than the capacity value of the resonance capacity, the coupling capacity being connected on the one side with the second lamp output terminal and being connected on the other side with one or both terminals of said dc-voltage input anda variable frequency oscillator which, in use, delivers a signal to said control circuit with a frequency which is determinative of the control frequency with which said switching elements are brought into conduction periodically and not in an overlapping manner,characterized in that the power circuit is arranged such that for starting the lamp, the resonance frequency of the resonance circuit of the power circuit, formed by at least the lamp coil and the resonance capacity, divided by the frequency of the control pulses for alternately and not in an overlapping manner bringing said switching elements into conduction for starting the gas discharge lamp, is slightly smaller than an odd positive integer, preferably 3%–
40% smaller, more preferably 10% to 25% smaller than the odd positive integer.
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Abstract
An input dc-voltage, usually obtained from an AC-mains voltage through a pre-connected rectifier and Power Factor Corrector, is converted by a series connection of two power transistors to an ac-voltage, which, via an LC section is presented to a gas discharge lamp.
For starting the lamp, the power transistors are switched with a frequency which is slightly higher than approximately one-third or one-fifth of the resonance frequency of the LC section.
Circuits have been provided for limiting the output voltage, for limiting the lamp current and for stabilizing the lamp output. Safety circuits switch the power circuit off if the lamp does not ignite or if the lamp exhibits rectifying effect.
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Citations
64 Claims
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1. A power circuit for starting and operating a gas discharge lamp with ac-voltage, wherein the power circuit is provided with:
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at least a first and a second lamp output terminal between which, in use, the gas discharge lamp is connected, a dc-voltage input, with at least two input terminals, a series connection of at least two switching elements such as, for instance, power transistors, which is connected between the input terminals of the dc-voltage input, a control circuit arranged for delivering control pulses to the switching elements for alternately and not in an overlapping manner bringing said switching elements into conduction, at least one lamp coil which is connected, on the one side, to the junction of said switching elements and which, on the other side, is connected with the first lamp output terminal, at least one resonance capacity, at least comprising one or more capacitors while the resonance capacity is connected, on one side, to the first lamp output terminal and, on the other side, is connected to one or both input terminals, at least one coupling capacity, at least comprising one or more capacitors, the coupling capacity having a capacity value which is considerably greater than the capacity value of the resonance capacity, the coupling capacity being connected on the one side with the second lamp output terminal and being connected on the other side with one or both terminals of said dc-voltage input and a variable frequency oscillator which, in use, delivers a signal to said control circuit with a frequency which is determinative of the control frequency with which said switching elements are brought into conduction periodically and not in an overlapping manner, characterized in that the power circuit is arranged such that for starting the lamp, the resonance frequency of the resonance circuit of the power circuit, formed by at least the lamp coil and the resonance capacity, divided by the frequency of the control pulses for alternately and not in an overlapping manner bringing said switching elements into conduction for starting the gas discharge lamp, is slightly smaller than an odd positive integer, preferably 3%–
40% smaller, more preferably 10% to 25% smaller than the odd positive integer. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 38, 39, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 57, 58, 59, 60, 61, 62, 63, 64)
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37. A power circuit for starting and operating a gas discharge lamp with ac-voltage, to be connected between a first and a second lamp output terminal of the power circuit, the power circuit consisting of:
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a dc-voltage input with two input terminals, a series circuit of two power transistors, connected between the input terminals of this dc-voltage input, a control circuit delivering control pulses to the said power transistors for alternately and not in an overlapping manner bringing said power transistors into conduction, a lamp coil, connected, on the one side, to the junction of said power transistors, and, on the other side, to the first lamp output terminal, a resonance capacity at least consisting of one or more capacitors, connected, on the one side, to the first lamp output terminal, and, on the other side, to one or both said input terminals, a coupling capacity, consisting of one or more capacitors, with a capacity value which is considerably greater than that of said resonance capacity, and connected to the second lamp output terminal one the one side and to one or both terminals of said dc-voltage input on the other side, a variable frequency oscillator delivering a frequency to the said control circuit which is determinative of the control frequency with which said power transistors are brought into conduction periodically and not in an overlapping manner, characterized in that for starting the lamp, the ratio between the resonance frequency of the resonance circuit, formed by said lamp coil and said resonance capacity and the control frequency for alternately and not in an overlapping manner bringing said power transistors into conduction for starting the gas discharge lamp, is slightly smaller than an odd positive integer. - View Dependent Claims (40, 41, 56)
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Specification
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Current AssigneeN.V. Nederlandsche Apparatenfabriek "Nedap"
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Original AssigneeN.V. Nederlandsche Apparatenfabriek "Nedap"
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Inventorsvan Eerden, Gerrit Hendrik
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Primary Examiner(s)Vu; David
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Assistant Examiner(s)A, MINH D
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Application NumberUS10/950,649Publication NumberTime in Patent Office875 DaysField of Search315/291, 315/307, 315/171, 315/172, 315/178, 315/209.R, 315/211, 315/214, 315/DIG.7US Class Current315/291CPC Class CodesH05B 41/3925 by frequency variation H05B...
