Lamp ballast system
First Claim
1. A ballast circuit for a fluorescent lamp, comprising:
- means coupled between the lamp and an alternating current power supply for limiting changes in current flow to the lamp;
means coupled between the lamp and the power supply for correcting the power factor between the lamp and the power supply and for controlling current flow in the circuit;
electronic starter means coupled across electrodes of the lamp for providing current through said electrodes for preheating said electrodes, said starter means comprising a triac coupled across said electrodes, said triac having a trigger input coupled to a diac that in turn is coupled to a capacitor coupled to said power supply so that said triac is triggered whenever a sufficient voltage builds up across said capacitor to trigger said diac, said triac and means for limiting current changes being disposed such that termination of triggering of said triac causes a sufficient voltage pulse to be produced across said electrodes to produce an arc thereacross;
a snubber circuit coupled across said triac and comprising a resistor and capacitor connected in series so that said starter means is prevented from latching at the triggering point of said triac; and
a diode and resistor coupled in series to form a preheating current path which in turn is coupled across said electrodes thereby to provide additional preheat current through said electrodes during every other half cycle of said current prior to production of said arc.
3 Assignments
0 Petitions
Accused Products
Abstract
A ballast circuit for a fluorescent lamp includes a magnetic choke coupled between the lamp and a power supply and an electronic starter circuit coupled across said lamp. The magnetic choke includes an inductor and a capacitor to limit the supply of current to the lamp. The capacitor provides power factor correction and limits current supply without dissipating power in the form of heat. The electronic starter circuit includes a triac coupled across the lamp that is triggered by a diac coupled to the power supply input through a capacitor. When a sufficient charge builds up on the capacitor, the diac is triggered and, in turn, the triac is triggered to provide current through the electrodes of the lamp to thereby preheat the electrodes. Almost as instantly as the triac is triggered, the diac is caused to stop triggering the triac and therefore, the triac becomes non-conducting and is removed from the cirucit. Upon removal of the triac, the sudden stop of current flow causes the magnetic choke inductor to produce a voltage spike across the lamp electrodes to thereby cause an arc to extend between the electrodes. Selective dimming of the lamp is achieved by proper selection of the capacitor coupled to the magnetic choke.
43 Citations
15 Claims
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1. A ballast circuit for a fluorescent lamp, comprising:
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means coupled between the lamp and an alternating current power supply for limiting changes in current flow to the lamp; means coupled between the lamp and the power supply for correcting the power factor between the lamp and the power supply and for controlling current flow in the circuit; electronic starter means coupled across electrodes of the lamp for providing current through said electrodes for preheating said electrodes, said starter means comprising a triac coupled across said electrodes, said triac having a trigger input coupled to a diac that in turn is coupled to a capacitor coupled to said power supply so that said triac is triggered whenever a sufficient voltage builds up across said capacitor to trigger said diac, said triac and means for limiting current changes being disposed such that termination of triggering of said triac causes a sufficient voltage pulse to be produced across said electrodes to produce an arc thereacross; a snubber circuit coupled across said triac and comprising a resistor and capacitor connected in series so that said starter means is prevented from latching at the triggering point of said triac; and a diode and resistor coupled in series to form a preheating current path which in turn is coupled across said electrodes thereby to provide additional preheat current through said electrodes during every other half cycle of said current prior to production of said arc. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A ballast circuit for a fluorescent lamp having two electrodes comprising:
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a magnetic choke coupled between one of said electrodes and a power supply, said magnetic choke including an inductor and a first capacitor connected in series; and a starter circuit coupled across said electrodes, said starter circuit including a first path coupled across said electrodes having a diode and first resistor connected in series, a second path coupled across said electrodes including a second capacitor and a second resistor connected in series, a third path coupled across said electrodes including a third resistor and a third capacitor connected in series and a diac having an input connected between said third resistor and said third capacitor, and a triac coupled across said electrodes and having a triggering input connected to an output of said diac. - View Dependent Claims (9, 10)
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11. A ballast circuit for a fluorescent lamp, comprising:
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a magnetic choke coupled between a lamp and an alternating current power supply and including an inductor ad a capacitor connected in series; an electronic starter circuit coupled across electrodes of said lamp and including;
a triad coupled across said electrodes and means for triggering said triac whenever power is applied to said ballast circuit so that said triac directs preheating current through said electrodes, means for turning off said triac shortly after triggering of a said triac and to place a voltage pulse across said electrodes to create an electrical are across said electrodes;a snubber circuit coupled across said triac and including a capacitor and resistor connected in series, so that said snubber circuit prevents latching of said starter circuit about a triggering point of said triac; and a diode and resistor coupled in series to form a preheating current path which in turn is coupled across said electrodes thereby to provide additional preheat current through said electrodes during every other half cycle of said current prior to production of said arc. - View Dependent Claims (12, 13, 14)
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15. A ballast circuit for a fluorescent lamp, comprising:
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means including an inductive reactor coupled between the lamp and a power supply for limiting changes in current flow to the lamp; means including a first capacitor coupled between the lamp and the power supply for correcting the power factor between the lamp and the power supply and for controlling current flow in the circuit; starter means including a triac coupled across electrodes of the lamp for providing current through said electrodes for preheating said electrodes, said triac having a trigger input coupled to a diac that in turn is coupled to a second capacitor that in turn is coupled to one of said electrodes so that said triac is triggered whenever a sufficient voltage builds up across said second capacitor to trigger said diac, said starter means further comprising a snubber circuit coupled across said triac and comprising a resistor and a capacitor connected in series so that said starter means is prevented from latching at the triggering point of said triac, said starter means also comprising a further preheat circuit coupled across said electrodes and comprising a resistor and diode connected in series to form a preheating current path to provide additional preheating current through said electrodes during every other half cycle of said current, triggering of said triac placing a short circuit across said electrodes and subsequent termination of said triggering of said triac causing said inductive reactor to initiate a voltage spike across said lamp to cause arcing across said electrodes.
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Specification