Electronic ballast with filament cut-out
First Claim
1. An electronic ballast comprising:
- a high voltage rail and a common rail;
a pair of switching transistors coupled in series between said high voltage rail and said common rail and having a junction therebetween;
an inductor and a capacitor coupled in series between said junction and one of the rails to form a series resonant circuit;
a transformer including said inductor as a primary winding and further including a secondary winding;
a filament transformer including a first winding and a second winding;
an AC switch;
wherein said secondary winding, said first winding, and said AC switch are connected in series, whereby said AC switch controls the flow of current through said first winding from said secondary winding.
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0 Petitions
Accused Products
Abstract
An electronic ballast for a gas discharge lamp includes an AC to DC converter for changing alternating current at power line voltage to direct current and an inverter powered by the converter and having a series resonant, direct coupled output coupled to the lamp. The inverter includes an AC switch having a diode bridge defining an AC diagonal and a DC diagonal and a transistor connected across the DC diagonal. The primary winding of a filament transformer is connected across the AC diagonal of the bridge and the transistor is coupled to the microprocessor for controlling current through the primary winding. The microprocessor is programmed to close the AC switch while the lamp is starting and to open the switch after the lamp is started, thereby cutting off the filaments from a source of power and reducing the power consumed by the ballast during normal operation. A resistor in series with the transistor is used to detect filament resistance and provide an indication of lamp type.
75 Citations
15 Claims
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1. An electronic ballast comprising:
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a high voltage rail and a common rail; a pair of switching transistors coupled in series between said high voltage rail and said common rail and having a junction therebetween; an inductor and a capacitor coupled in series between said junction and one of the rails to form a series resonant circuit; a transformer including said inductor as a primary winding and further including a secondary winding; a filament transformer including a first winding and a second winding; an AC switch; wherein said secondary winding, said first winding, and said AC switch are connected in series, whereby said AC switch controls the flow of current through said first winding from said secondary winding. - View Dependent Claims (2, 3, 4, 5)
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6. A method for operating an electronic ballast controlled by a microprocessor, said method comprising the steps of:
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determining the approximate resistance of a lamp filament coupled to the ballast; if the resistance matches data stored in the microprocessor, then starting the lamp; else entering a default routine. - View Dependent Claims (7, 8, 9, 10, 11)
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12. A method for operating an electronic ballast controlled by a microprocessor, said method comprising the steps of:
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determining the approximate resistance of a lamp filament coupled to the ballast; if the resistance matches data stored in the microprocessor, then starting the lamp; else entering a default routine; supplying a discharge current to the lamp in accordance with matching data stored in the microprocessor. - View Dependent Claims (13, 14, 15)
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Specification