Claims
- 1. An electronic ballast for powering a gas discharge lamp from an AC input voltage, said ballast having a height equal to or less than one inch, a power factor.gtoreq.0.9, and a harmonic distortion.ltoreq.10 percent, said ballast comprising:
- a converter for converting said AC input voltage into pulses of direct current at a high voltage, said converter including means for varying the current drawn by said converter in phase with said AC input voltage by changing the frequency of said pulses;
- a capacitor coupled to the output of said converter for storing said high voltage;
- a driven, half-bridge inverter powered by the energy stored in said capacitor, said inverter having a series resonant, direct coupled output for connection to said lamp;
- wherein said converter includes a first magnetic and said inverter includes a second magnetic and said first magnetic and said second magnetic have separate cores.
- 2. The ballast as set forth in claim 1 wherein said inverter is driven and said ballast further comprises:
- a control circuit including an output coupled to said converter for shutting off said converter.
- 3. The ballast as set forth in claim 2 wherein said control circuit includes a third magnetic, wherein said third magnetic has a core separate from said first magnetic and said second magnetic.
- 4. The ballast as set forth in claim 3 wherein each magnetic is wound on an EE core.
- 5. The ballast as set forth in claim 4 wherein the magnetics have an approximately cubic shape.
- 6. The ballast as set forth in claim 2 wherein said converter also converts said alternating current into a direct current at a low voltage and said control circuit is powered by said direct current at low voltage.
- 7. The ballast as set forth in claim 2 wherein said control circuit includes circuitry for shutting off said ballast in the event of a fault condition.
- 8. The ballast as set forth in claim 7 and further including a sense capacitor in series with said lamp, wherein said sense capacitor is coupled to said circuitry for shutting off said ballast.
- 9. The ballast as set forth in claim 1 wherein the frequency of said converter varies with the amplitude of said AC input voltage.
- 10. An electronic ballast for powering a gas discharge lamp from an AC input voltage, said ballast having a height equal to or less than one inch, said ballast comprising:
- a self-oscillating converter for converting said AC input voltage into pulses of direct current at a high voltage, said converter including means for varying the current drawn by said converter in phase with said AC input voltage by changing the frequency of said pulses;
- a driven, half-bridge inverter, said inverter having a series resonant, direct coupled output for connection to said lamp;
- a control circuit coupled to said inverter for driving said inverter at a predetermined frequency;
- said converter includes a first magnetic, said direct coupled output includes a second magnetic, and said control circuit includes a third magnetic, wherein each magnetic is on a separate core.
- 11. The ballast as set forth in claim 10 wherein said converter also converts said alternating current into a direct current at a low voltage and said control circuit is powered by said direct current at low voltage.
- 12. The ballast as set forth in claim 10 wherein said converter includes means for varying the frequency of said converter in phase with the amplitude of said AC input voltage.
- 13. The ballast as set forth in claim 10 wherein said converter includes:
- a full wave rectifier for rectifying said AC input voltage; and
- means for varying said direct current in phase with a ripple component of the rectified AC input voltage.
CROSS-REFERENCE TO RELATED APPLICATION
This application is a continuation-in-part of co-pending application Ser. No. 08/148,295, filed Nov. 8, 1993, entitled "Electronic Ballast with Low Harmonic Distortion" and assigned to the assignee of this invention.
US Referenced Citations (6)
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
148295 |
Nov 1993 |
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