Control circuit for gas discharge lamps, which has a transformer with start and run windings
First Claim
1. A control circuit for a gas discharge lamp, which is configured for connection to a source of an AC run current, wherein the control circuit comprises:
- input terminals which are adapted to be coupled to the source of the AC run current;
output terminals which are adapted to be coupled to the gas discharge lamp;
a transformer having a primary run winding, a primary start winding and a secondary winding, wherein the primary run winding is coupled to the input terminals and the secondary winding is coupled in parallel with the output terminals;
a run current control switch coupled in series with the primary run winding;
an oscillator coupled to the primary start winding of the transformer;
a start current control switch coupled to the oscillator;
a current sensor coupled in series with the output terminals; and
a feedback loop coupled between the current sensor and the run current control switch and between the current sensor and the start current control switch such that the run current control switch and the start current control switch are responsive to the current sensor.
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Accused Products
Abstract
A control circuit for a gas discharge lamp according to the present invention includes a transformer having a primary run winding, a primary start winding and a secondary winding. The primary run winding is coupled to a source of an AC run signal. The secondary winding is coupled to the gas discharge lamp. A current sensor is coupled in series with the gas discharge lamp to sense current flow through the lamp. A high frequency oscillator is coupled to the primary start winding for providing a high frequency start signal to the primary start winding. In a start phase, the oscillator provides the high frequency start signal to the primary start winding to initiate ionization of the gas discharge lamp. Once the gas has sufficiently ionized in the lamp, the control circuit switches from the start phase to a run phase by removing the high frequency start signal from the primary start winding and applying the AC run signal to the primary run winding. Switching between the high frequency start signal and the AC run signal on the low voltage primary side of the transformer allows the transformer to be sized much smaller to match the operating characteristics of the bulb as opposed to its start characteristics.
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Citations
28 Claims
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1. A control circuit for a gas discharge lamp, which is configured for connection to a source of an AC run current, wherein the control circuit comprises:
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input terminals which are adapted to be coupled to the source of the AC run current; output terminals which are adapted to be coupled to the gas discharge lamp; a transformer having a primary run winding, a primary start winding and a secondary winding, wherein the primary run winding is coupled to the input terminals and the secondary winding is coupled in parallel with the output terminals; a run current control switch coupled in series with the primary run winding; an oscillator coupled to the primary start winding of the transformer; a start current control switch coupled to the oscillator; a current sensor coupled in series with the output terminals; and a feedback loop coupled between the current sensor and the run current control switch and between the current sensor and the start current control switch such that the run current control switch and the start current control switch are responsive to the current sensor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A control circuit for a gas discharge lamp, which is configured for connection to a source of an AC run signal that has a first frequency, wherein the control circuit comprises:
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input terminals which are adapted to be coupled to the source of the AC run signal; output terminals which are adapted to be coupled to the gas discharge lamp; a transformer having a primary run winding, a primary start winding and a secondary winding, wherein the primary run winding is coupled to the input terminals and the secondary winding is coupled in parallel with the output terminals; oscillator means coupled to the primary start winding for generating a start signal which has a second frequency that is higher than the first frequency; means for sensing current flow through the output terminals; means for selectively applying the start signal to the primary start winding as a function of the sensed current through the output terminals; and means for selectively applying the run signal to the primary run winding as a function of the sensed current through the output terminals. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20)
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21. A method of controlling a gas discharge lamp, comprising:
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coupling the gas discharge lamp in parallel with a secondary winding of a transformer; applying an alternating current (AC) start signal to a primary start winding of the transformer; sensing current flow generated through the gas discharge lamp in response to the AC start signal; removing the AC start signal as a function of the sensed current flow through the gas discharge lamp; and applying an alternating current (AC) run signal to a primary run winding of the transformer after removing the AC start signal. - View Dependent Claims (22, 23, 24, 25, 26)
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27. A control circuit for a gas discharge lamp, which is configured for connection to a source of an AC run signal that has a first frequency, wherein the control circuit comprises:
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input terminals which are adapted to be coupled to the source of the AC run signal; output terminals which are adapted to be coupled to the gas discharge lamp; a transformer having a primary run winding, a primary start winding and a secondary winding, wherein the primary run winding is coupled to the input terminals and the secondary winding is coupled in parallel with the output terminals; an oscillator having an oscillator output which is coupled to the primary start winding and which generates a start signal having a second frequency that is higher than the first frequency; a current sensor coupled in series with the output terminals, wherein the current sensor has a sensor output which generates a feedback signal as a function of current flowing through the secondary winding; a start current control switch coupled to the oscillator, which selectively applies the start signal to the primary start winding as a function of the feedback signal; and a run current control switch coupled in series with the primary run winding, which selectively applies the AC run signal to the primary run winding as a function of the feedback signal.
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28. A gas discharge lamp control circuit configured for controlling power delivered from an AC source to a gas discharge lamp, wherein the AC source supplies an AC drive signal having a plurality of sequential positive and negative half cycles, the control circuit comprising:
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input terminals which are adapted to be coupled to the AC source; output terminals which are adapted to be coupled to the gas discharge lamp; a transformer having a primary winding and a secondary winding, wherein the primary winding is coupled to the input terminals and the secondary winding is coupled in parallel with the output terminals; a capacitor coupled in series with the output terminals; phase control means coupled in series with the primary winding for conducting current of the AC drive signal after a first phase delay during the positive half cycles and for conducting current of the AC drive signal after a second phase delay during the negative half cycles; and trigger means coupled to the phase control means for determining the first and second phase delays.
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Specification