Claims
- 1. An electronic ballast for powering a gas discharge lamp, said ballast comprising:
- an inverter having a series resonant output including a first inductor and a first capacitor connected in series;
- control means for driving said inverter at an adjustable frequency; and
- a second inductor, magnetically coupled to said first inductor, for supplying power to said control means.
- 2. The ballast as set forth in claim 1 and further including:
- a converter for converting an AC input voltage into pulses of direct current at a high voltage and for converting said AC input voltage into a direct current at a low voltage;
- wherein said direct current at low voltage also supplies power to said control means.
- 3. The ballast as set forth in claim 1 wherein said output is a direct coupled output.
- 4. The ballast as set forth in claim 1 and further including a second capacitor and a diode; wherein said second inductor includes a first end and a second end, said first end is connected to a common point, said second end is coupled by said diode to said second capacitor, and said second capacitor is coupled to a supply input of said control means.
- 5. The ballast as set forth in claim 4 and further including a zener diode coupled to said second capacitor.
- 6. The ballast as set forth in claim 5 and further including an NPN transistor, wherein said zener diode is coupled to the base of said NPN transistor.
- 7. The ballast as set forth in claim 6 and further including:
- a converter for converting an AC input voltage into pulses of direct current at a high voltage and for converting said AC input voltage into a direct current at a low voltage;
- wherein said direct current at low voltage also supplies power to said control means; and
- wherein said converter includes said NPN transistor and said NPN transistor controls the frequency of said pulses.
- 8. An electronic ballast for powering a gas discharge lamp, said ballast comprising:
- a half-bridge inverter having a series resonant output for connection to said lamp;
- sense means coupled to said inverter and to said output for detecting a DC voltage across said lamp and for increasing the frequency of said inverter when the DC voltage is detected, whereby said lamp is dimmed at end of life.
- 9. The ballast as set forth in claim 8 wherein said sense means includes a zener diode for defining a threshold voltage that said DC voltage must exceed before the sense means increases the frequency of the inverter.
- 10. The ballast as set forth in claim 8 wherein said output is a direct coupled output.
- 11. An electronic ballast for powering a gas discharge lamp, said ballast comprising:
- an inverter having a series resonant output including a first inductor and a capacitor connected in series;
- control means for driving said inverter at an adjustable frequency;
- a second inductor, magnetically coupled to said first inductor, for supplying power to said control means; and
- sense means coupled to said inverter and to said output for detecting a DC voltage across said lamp and for increasing the frequency of said inverter when a DC voltage is detected.
- 12. The ballast as set forth in claim 11 and further including:
- a converter for converting an AC input voltage into pulses of direct current at a high voltage and for converting said AC input voltage into a direct current at a low voltage;
- wherein said direct current at low voltage also supplies power to said control means.
CROSS-REFERENCE TO RELATED APPLICATION
This application is a division of application Ser. No. 08/879,181, filed Jun. 20, 1997.
US Referenced Citations (2)
Number |
Name |
Date |
Kind |
5500576 |
Russell et al. |
Mar 1996 |
|
5808422 |
Venkitasubrahmanian et al. |
Sep 1998 |
|
Divisions (1)
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Number |
Date |
Country |
Parent |
879181 |
Jun 1997 |
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