Driver circuit for an HID lamp and method for operating an HID lamp
View Patent ↗The present invention relates to a driver circuit for an HID lamp having a circuit arrangement for applying a radiofrequency signal for the purpose of starting the lamp and for applying a low-frequency signal for the purpose of operating the lamp after starting, the driver circuit being designed to drive the HID lamp, immediately after starting, using a radiofrequency signal for a period of time, the period of time being variable and depending on at least one operating parameter for the lamp which is set after starting. It also relates to a corresponding method for operating an HID lamp.
1. A method for operating an HID lamp, comprising the following steps:
a) applying a radiofrequency signal to the lamp for the purpose of starting the lamp;
b) measuring at least one operating parameter for the lamp, in particular during or immediately after starting;
c) as a function of the at least one measured operating parameter for the lamp, determining whether to operate the lamp by applying a low-frequency signal to the lamp; and
d) as a function of the at least one measured operating parameter for the lamp, determining whether to operate the lamp by applying a radiofrequency signal to the lamp.
2. The method of claim 1 wherein measuring at least one operating parameter of the lamp occurs only during a low frequency period of operation of the lamp.
3. The method of claim 1 wherein step d) comprises discontinuing the operation of the lamp when a discontinuation condition is fulfilled.
4. The method of claim 1 wherein step d) comprises operating the lamp by applying a radiofrequency signal and repeating from step b) until at least one operating parameter is measured to operate the lamp by applying a low-frequency signal to the lamp.
5. The method of claim 1 , wherein the at least one operating parameter is at least one feature of a current through the lamp and/or of a voltage present across the lamp.
6. The method of claim 5 , wherein the at least one feature is the symmetry of the amplitude of the current through the lamp or that of the voltage across the lamp with respect to a zero value.
7. The method of claim 5 , wherein the at least one feature is a DC component of the current through the lamp or of the voltage across the lamp.
8. The method of claim 5 , wherein the at least one feature is the absolute value of the amplitude of the voltage across the lamp and/or an absolute value of the amplitude of the current through the lamp.