Circuit apparatus and method for operating a lamp

• US 20040245942A1
• Filed: 07/23/2003
• Published: 12/09/2004
• Est. Priority Date: 08/01/2002
• Status: Active Grant

• Current Assignee: Patent-Treuhand-Gesellschaft Fur Elektrische Gluhlampen mbH (Ams-Osram AG)
• Original Assignee: Patent-Treuhand-Gesellschaft Fur Elektrische Gluhlampen mbH (Ams-Osram AG)
• Inventors: Storm, Arwed, Mayer, Siegfried
• Granted Patent: US 7,053,561 B2
• Time in Patent Office: Days
• US Class Current: 315/291
• CPC Class Codes: H05B 41/2856 against internal abnormal circuit conditions
• CPC Class Codes: Y10S 315/07 Starting and control circuits for gas discharge lamp using transistors

Abstract

The current through the components of a half-bridge of an electronic ballast is intended to be limited during the starting phase. For this purpose, the gate of a half-bridge transistor (T2) is driven by a current limiting circuit (D1, D2, D3, T3, C3) in such a way that the current through the transistors (T1, T2) is limited during the starting phase, whereas it remains unlimited during the glow phase and burning phase of the lamp (LA).

Claims

1. A circuit apparatus for operating a lamp, in particular a low-pressure discharge lamp, having an inverter device for supplying the lamp with alternating current, which has at least one transistor switching unit, and a current limiting device, which is connected to the at least one transistor switching unit, for limiting the current through the at least one transistor switching unit, wherein the control electrode of the at least one transistor switching unit can be driven by the current limiting device for the purpose of current limitation.

2. The circuit apparatus as claimed in claim 1, in which the inverter device comprises a half-bridge including the at least one transistor unit and a further transistor unit

3. The circuit apparatus as claimed in claim 2, in which the at least one transistor unit comprises a MOSFET transistor.

4. The circuit apparatus as claimed in one of claims 1 to 3, in which the lamp can be operated in a load circuit that is connected to the inverter device.

5. The circuit apparatus as claimed in claim 4, which comprises a phase setting device, connected to the inverter device, for matching the operating frequency of the inverter device to a resonant frequency of the load circuit.

6. The circuit apparatus as claimed in claim 5, in which the phase setting device is connected to a control electrode of the at least one transistor switching unit

7. The circuit apparatus as claimed in claim 5, in which the phase setting device is connected in parallel with the current limiting device.

8. The circuit apparatus as claimed in claim 1, in which the current limiting device comprises a switching device by means of which the at least one transistor switching unit can be switched on and off as a function of the current through the at least one transistor switching unit.

9. A method for operating a lamp, in particular a low-pressure discharge lamp, by generating an alternating current for supplying the lamp by means of at least one transistor switching unit and limiting the current through the at least one transistor switching unit, wherein the control electrode of the at least one transistor switching unit is driven for the purpose of current limitation.

10. The method as claimed in claim 9, in which the lamp is operated in a load circuit.

11. The method as claimed in claim 10, in which the frequency of the generated alternating current is matched to a resonant frequency of the load circuit.

12. The method as claimed in one of claims 9 to 11, in which the at least one transistor switching unit is switched off at a prescribed threshold value as a function of the current flowing through it.