Ballast power control circuit
First Claim
1. A ballast circuit for energizing a lamp, comprising:
- first and second input terminals for receiving an AC input signal which energizes the ballast circuit;
an inductive element coupled to the first input terminal;
a plurality of capacitive elements coupled in parallel with the lamp, each of the capacitive elements having first and second terminals, said first terminal being coupled to the inductive element, wherein a current flowing through the capacitive element and the inductive element resonates in series, a switch connected to said capacitive elements and configured to selectively couple different selected ones of said capacitive elements into said ballast circuit to selectively vary the total capacitance of said ballast circuit.
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Accused Products
Abstract
A ballast circuit for energizing a lamp includes an inductive element coupled to an input terminal and a capacitive element coupled to the inductive element in parallel with the lamp. In one embodiment, the capacitive element includes a plurality of capacitors each of which is coupled in series with a switch to control the total capacitance provided by the capacitors. By controlling the total capacitance, the intensity of light emitted by the lamp can be selected. In another embodiment, a switching element is coupled across one of the capacitors for providing a selected capacitance to the circuit for controlling the lamp light intensity. In a further embodiment, a transformer has a first winding coupled in series with the capacitive element with the inductive impedance of the first winding being controlled via a second transformer winding coupled to a control circuit. In another embodiment, a ballast circuit includes a transformer for introducing a series current into the circuit for subsequent detection by a detection circuit. This arrangement can be used to send a data signal from one point in the circuit to another which can be used to determine a lamp fight intensity level.
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Citations
23 Claims
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1. A ballast circuit for energizing a lamp, comprising:
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first and second input terminals for receiving an AC input signal which energizes the ballast circuit;
an inductive element coupled to the first input terminal;
a plurality of capacitive elements coupled in parallel with the lamp, each of the capacitive elements having first and second terminals, said first terminal being coupled to the inductive element, wherein a current flowing through the capacitive element and the inductive element resonates in series, a switch connected to said capacitive elements and configured to selectively couple different selected ones of said capacitive elements into said ballast circuit to selectively vary the total capacitance of said ballast circuit. - View Dependent Claims (2, 3, 4, 5, 6, 14)
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7. A ballast circuit for energizing a lamp, comprising:
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first and second input terminals for receiving an AC input signal which energizes the ballast circuit;
an inductive element coupled to the first input terminal;
a capacitive element coupled in parallel with the lamp, the capacitive element having a first and second terminals, said first terminal being coupled to the inductive element;
a control circuit coupled to a switch for controlling a state of the switch;
a plurality of switches each of which is coupled in series with a respective one of a plurality of capacitors and connected to the control circuit;
wherein a current flowing through the capacitive element and the inductive element resonates in series. - View Dependent Claims (8)
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9. A ballast circuit for energizing a lamp, comprising:
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first and second input terminals for receiving an AC input signal which energizes the ballast circuit;
an inductive element coupled to the first input terminal;
a capacitive element coupled in parallel with the lamp, the capacitive element having a first and second terminals, said first terminal being coupled to the inductive element, the capacitive element having first and second capacitors coupled end to end, and a switching element coupled to the first capacitor for selectively shorting the first capacitor, wherein a current flowing through the capacitive element and the inductive element resonates in series. - View Dependent Claims (10, 11, 12)
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13. A ballast circuit for energizing a lamp, comprising:
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first and second input terminals for receiving an AC input signal which energizes the ballast circuit;
an inductive element coupled to the first input terminal;
a capacitive element coupled in parallel with the lamp, the capacitive element having a first and second terminals, said first terminal being coupled to the inductive element, the capacitive element including first and second capacitors coupled in parallel and a switching element coupled in series with the first capacitor;
wherein a current flowing through the capacitive element and the inductive element resonates in series.
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15. A ballast circuit for energizing a lamp, comprising:
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first and second input terminals for receiving an AC input signal which energizes the ballast circuit;
an inductive element coupled to the first input terminal;
a capacitive element coupled in parallel with the lamp, the capacitive element having first and second terminals, said first terminal being coupled to the inductive element, a transformer having a first winding coupled in series with the capacitive element, a control circuit coupled to the second winding of the transformer for canceling a predetermined level of flux generated by the first winding, wherein a current flowing through the capacitive element and the inductive element resonates in series.
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16. A ballast circuit for energizing a lamp, comprising:
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first and second input terminals for receiving an AC input signal which energizes the ballast circuit;
an inductive element coupled to the first input terminal;
a capacitive element coupled in parallel with the lamp, the capacitive element having first and second terminals, said first terminal being coupled to the inductive element, a transformer having a first winding coupled in series with the inductive element and having a second winding, and inductively coupled first and second inductive detection elements which are coupled to opposite ends of the lamp. - View Dependent Claims (17, 18, 19, 20)
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21. A circuit for energizing a load, comprising:
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first and second input terminals;
a transformer having a first winding coupled to the first input terminal and a second winding coupled to a signal generator;
an inductive element coupled to the first winding;
first and second inductive detection elements coupled to opposite ends of the load; and
a third inductive detection element coupled to a signal detector, the third detection element being inductively coupled to the first detection element, wherein the signal detector detects a signal from the signal generator. - View Dependent Claims (22, 23)
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Specification