Abstract: A retrofit Light Emitting Diode, LED, tube for replacing a fluorescent tube, wherein said retrofit LED tube is arranged to be connected to a ballast, said retrofit LED tube comprising a ballast determining unit arranged for identifying a type of ballast connected to said retrofit LED tube by controlling an output voltage of said power rectifier to a first voltage and measuring a first current provided by said power rectifier, controlling said output voltage of said power rectifier to a second voltage and measuring a second current provided by said power rectifier, wherein said second voltage differs from said first voltage and determining said type of ballast based on said first and second output voltages and said measured first and second currents, wherein said ballast determining unit is further arranged to configure said configurable matching circuit based on said determined type of ballast.

Abstract: A retrofit Light Emitting Diode, LED, tube for replacing a fluorescent tube, wherein said retrofit LED tube is arranged to be connected to a ballast, said retrofit LED tube comprising a ballast determining unit arranged for identifying a type of ballast connected to said retrofit LED tube by controlling an output voltage of said power rectifier to a first voltage and measuring a first current provided by said power rectifier, controlling said output voltage of said power rectifier to a second voltage and measuring a second current provided by said power rectifier, wherein said second voltage differs from said first voltage and determining said type of ballast based on said first and second output voltages and said measured first and second currents, wherein said ballast determining unit is further arranged to configure said configurable matching circuit based on said determined type of ballast.

Abstract: A method for operating a fluorescent lamp (5) having a nominal power (WLa) and stabilized with an EM ballast (B) comprises the steps of during normal operation, short-circuiting the lamp during a closing time interval (CTI) during each current period in order to operate the lamp at a reduced power. The method comprises the step of detecting whether the lamp is stabilized by means of an inductive ballast or by means of a capacitive ballast. If it is found that the ballast is capacitive, the timing of the closing time interval (CTI) is set such that the closing time interval (CTI) has a first closing time segment (CTS1) immediately before a zero-crossing of the current, having a first duration (?1) higher than zero, and a second closing time segment (CTS2) immediately after said zero-crossing of the current, having a second duration (?2) higher than zero.

Abstract: A method for operating a fluorescent lamp (5) having a nominal power (WLa) and stabilized with an EM ballast (B) comprises the steps of during normal operation, short-circuiting the lamp during a closing time interval (CTI) during each current period in order to operate the lamp at a reduced power. The method comprises the step of detecting whether the lamp is stabilized by means of an inductive ballast or by means of a capacitive ballast. If it is found that the ballast is capacitive, the timing of the closing time interval (CTI) is set such that the closing time interval (CTI) has a first closing time segment (CTS1) immediately before a zero-crossing of the current, having a first duration (?1) higher than zero, and a second closing time segment (CTS2) immediately after said zero-crossing of the current, having a second duration (?2) higher than zero.