Electronic ballast having a symmetric topology
First Claim
1. An electronic ballast for driving a gas discharge lamp having first and second electrodes with a lamp current between the electrodes, the ballast comprising:
- an inverter circuit having an input for receiving a substantially DC bus voltage and first and second output terminals, the inverter circuit further comprising a main transformer having a primary winding coupled between the first and second output terminals, the primary winding having a center tap coupled to the DC bus voltage at the input, the inverter circuit operable to convert the bus voltage to a high-frequency AC voltage across the primary winding of the main transformer of the inverter circuit; and
a symmetrical resonant tank circuit operable to couple the high-frequency AC voltage to the lamp to drive the lamp with the lamp current, the resonant tank circuit comprising;
a split resonant inductor having first and second windings magnetically coupled together, the first winding adapted to be electrically coupled between the first output terminal of the inverter circuit and the first electrode of the lamp, the second winding adapted to be electrically coupled between the second output terminal of the inverter circuit and the second electrode of the lamp, the first and the second windings each having an output terminal across which output terminals an output of the resonant tank circuit is formed, such that the first and second windings are adapted to couple the high-frequency AC voltage of the inverter circuit to the electrodes of the lamp to drive the lamp with the lamp current; and
first and second resonant capacitors coupled in series electrical connection, the series combination of the first and second resonant capacitors coupled across the output of the resonant tank circuit;
wherein the junction of the first and second resonant capacitors is coupled to the center tap of the primary winding of the main transformer of the inverter circuit.
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Accused Products
Abstract
An electronic ballast for driving a gas discharge lamp having first and second electrodes comprises an inverter circuit and a symmetric resonant tank circuit for minimizing the RFI noise produced at the electrodes of the lamp. The inverter circuit receives a substantially DC bus voltage generates a high-frequency AC voltage. The symmetric resonant tank circuit comprises a split resonant inductor having first and second windings magnetically coupled together. The first and second windings electrically coupled between the respective electrodes of the lamp and the inverter circuit. The symmetric resonant tank further comprises first and second capacitors coupled in series electrical connection between the electrodes of the lamp with the junction of the first and second capacitors coupled to the DC bus voltage at the input of the inverter circuit.
57 Citations
34 Claims
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1. An electronic ballast for driving a gas discharge lamp having first and second electrodes with a lamp current between the electrodes, the ballast comprising:
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an inverter circuit having an input for receiving a substantially DC bus voltage and first and second output terminals, the inverter circuit further comprising a main transformer having a primary winding coupled between the first and second output terminals, the primary winding having a center tap coupled to the DC bus voltage at the input, the inverter circuit operable to convert the bus voltage to a high-frequency AC voltage across the primary winding of the main transformer of the inverter circuit; and a symmetrical resonant tank circuit operable to couple the high-frequency AC voltage to the lamp to drive the lamp with the lamp current, the resonant tank circuit comprising; a split resonant inductor having first and second windings magnetically coupled together, the first winding adapted to be electrically coupled between the first output terminal of the inverter circuit and the first electrode of the lamp, the second winding adapted to be electrically coupled between the second output terminal of the inverter circuit and the second electrode of the lamp, the first and the second windings each having an output terminal across which output terminals an output of the resonant tank circuit is formed, such that the first and second windings are adapted to couple the high-frequency AC voltage of the inverter circuit to the electrodes of the lamp to drive the lamp with the lamp current; and first and second resonant capacitors coupled in series electrical connection, the series combination of the first and second resonant capacitors coupled across the output of the resonant tank circuit; wherein the junction of the first and second resonant capacitors is coupled to the center tap of the primary winding of the main transformer of the inverter circuit. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. An electronic ballast for driving a gas discharge lamp having first and second electrodes with a lamp current between the electrodes, the ballast comprising:
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an inverter circuit having an input for receiving a substantially DC bus voltage and first and second output terminals, the inverter circuit further comprising a main transformer having a primary winding coupled between the first and second output terminals, the primary winding having a center tap coupled to the DC bus voltage at the input, the inverter circuit operable to convert the bus voltage to a high-frequency AC voltage across the primary winding of the main transformer of the inverter circuit; and a resonant tank circuit including a split resonant inductor having first and second windings magnetically coupled together, the first winding adapted to be electrically coupled between the first output terminal of the inverter circuit and the first electrode of the lamp, the second winding adapted to be electrically coupled between the second output terminal of the inverter circuit and the second electrode of the lamp, the first and the second windings each having an output terminal across which output terminals an output of the resonant tank circuit is formed, the first and second windings adapted to couple the high-frequency AC voltage of the inverter circuit to the electrodes of the lamp to drive the lamp with the lamp current; the resonant tank circuit further comprising first and second capacitors coupled in series electrical connection between the electrodes of the lamp and across the output of the resonant tank circuit, the junction of the first and second capacitors coupled to the center tap of the primary winding of the main transformer of the inverter circuit.
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15. An electronic ballast for driving a gas discharge lamp having first and second electrodes with a lamp current between the electrodes, the ballast comprising:
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a rectifier circuit for receiving a phase-controlled AC voltage and to generate a rectified voltage; a charge pump circuit coupled to the rectifier circuit for receiving the rectified voltage, the charge pump circuit comprising two series-connected diodes; a push-pull converter having an input coupled to the charge pump circuit for receiving a substantially DC bus voltage, the push-pull converter operable to generate a high-frequency AC voltage and to provide the high-frequency AC voltage across first and second output terminals of the push-pull converter, the push-pull converter further comprising a bus capacitor coupled across the input and a main transformer having a primary winding coupled across the first and the second output terminals, the primary winding having a center tap coupled to the DC bus voltage, the push-pull converter further comprising first and second semiconductor switches electrically coupled to the primary winding of the main transformer for conducting an inverter current through the primary winding on an alternate basis; and a split resonant inductor having first and second windings magnetically coupled together, the first winding adapted to be electrically coupled between the first output terminal of the push-pull converter and the first electrode of the lamp, the second winding adapted to be electrically coupled between the second output terminal of the push-pull converter and the second electrode of the lamp, the first and the second windings each having an output terminal across which output terminals an output of the resonant tank circuit is formed, such that the first and second windings are adapted to couple the high-frequency AC voltage of the inverter circuit to the electrodes of the lamp to drive the lamp with the lamp current, the first and second resonant capacitors coupled in series electrical connection, the series combination of the first and second resonant capacitors coupled across the output of the resonant tank circuit, the junction of the first and second resonant capacitors is coupled to the center tap of the primary winding of the main transformer of the inverter circuit; wherein the charge pump circuit further comprises a capacitor and an inductor coupled in series between the junction of the two series-connected diodes and the first output terminal of the push-pull converter.
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16. A ballast for a gas discharge lamp for driving the lamp with a lamp current between electrodes of the lamp, comprising:
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an inverter circuit having an input for receiving a substantially DC bus voltage and first and second output terminals, said inverter circuit further comprising a main transformer having a primary winding coupled between said first and second output terminals, said primary winding having a center tap coupled to said DC bus voltage at said input, said inverter circuit operable to convert said bus voltage to a high-frequency AC voltage across said primary winding of said main transformer; and an output circuit having first and second input terminals for receiving the high-frequency AC voltage generated by the inverter circuit and having first and second output terminals for coupling to respective terminals of said gas discharge lamp, said output circuit further comprising an inductor having first and second windings which are magnetically coupled together and first and second capacitors having first and second terminals respectively, said first terminals of said first and second capacitors connected to one another at a node and in series with one another, said first and second windings having respective first and second ends, said first ends of said first and second windings connected to said first and second input terminals respectively, said second ends of said first and second windings respectively connected to said second terminals of said first and second capacitors and to said first and second output terminals, said first and second windings electrically coupling, respectively, the first input terminal to the first output terminal and the second input terminal to the second output terminal to drive the lamp with the lamp current; wherein said node connecting said first and second resonant capacitors is coupled to said center tap of said primary winding of said main transformer of said inverter circuit. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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27. A circuit for driving a gas discharge lamp from an AC power source with a lamp current between electrodes of the lamp, said circuit comprising:
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a dimmer switch adapted to be connected to said AC source and producing a phase-controlled voltage; and an electronic dimming ballast connected to a dimmer output of said dimmer switch and having a ballast output adapted to be connected to said gas discharge lamp, said ballast comprising; a rectifier circuit for producing a rectified voltage having a magnitude related to said phase-controlled output voltage; an inverter circuit connected to said rectified voltage and producing a square wave output voltage having a period related to said rectified voltage, said inverter circuit comprising a main transformer having a primary winding across which said square wave output voltage is generated, said primary winding having a center tap for receiving said rectified voltage; and a resonant tank circuit comprising an inductor assemblage and a capacitor assemblage connected in parallel with said inductor assemblage for converting said square wave output voltage to a generally sinusoidal output voltage which is coupled across said lamp, said inductor assemblage comprising first and second inductor windings, which are magnetically coupled together, said capacitor assemblage comprising first and second capacitors connected in series at a common node, said common node connected to said center tap of said primary winding of said main transformer, said first and second inductor windings having first terminals connected in series with the main transformer primary winding and second terminals connected to said first and second capacitors, respectively, such that the generally sinusoidal output voltage is developed across the second terminals to drive the lamp with the lamp current. - View Dependent Claims (28, 29, 30, 31, 32, 33)
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34. A resonant tank circuit for an electronic ballast for a gas discharge lamp for driving the lamp with a lamp current between electrodes of the lamp, said ballast comprising an inverter circuit for receiving a substantially DC bus voltage and generating a high-frequency AC voltage across a primary winding of a main transformer, said resonant tank circuit comprising:
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an inductor assemblage comprising first and second inductor windings magnetically coupled by a common magnetic core; and a parallel-connected capacitor assemblage comprising first and second series-connected capacitors having first terminals connected at a common node and second terminals, respectively; wherein first terminals of said first and second windings of said inductor assemblage define input terminals of said resonant tank circuit, and second terminals of said first and second windings define output terminals of said resonant tank circuit, said second terminals of said first and second windings connected to said second terminals of said first and second capacitors, a voltage developed across said second terminals of the first and second capacitors driving the lamp with the lamp current, said common node connecting said first and second capacitors coupled to a center tap of the primary winding of the main transformer of the inverter circuit.
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Specification