A driving circuit and a method for operating the driving circuit is provided for a lamp, the lamp includes a lighting unit, and a first and a second pair of connection pins for coupling the driving circuit to a power supply unit. The driving circuit includes a pre-heating detection circuit and a protection circuit. The pre-heating detection circuit is coupled to the first pair of connection pins and configured to detect a voltage between the first pair of connection pins and output a reference voltage. The protection circuit includes a switching circuit connected in series with the lighting unit, the protection circuit is configured to compare the reference voltage with an input voltage of the lamp and turn on the switching circuit to light the lighting unit when the input voltage of the lamp is greater than the reference voltage.

The present invention relates to a LED tube (1) for retrofitting in a fluorescent tube lighting fixture having a preheat phase during which the fluorescent tube lighting fixture is arranged to preheat filaments of a fluorescent tube, the LED tube (1) comprising: an array of LEDs (2), a LED driver (4) for driving the array of LEDs (2), a first pair of contact pins (8, 0) at a first end (12) of the LED tube (1) and a second pair of contact pins (14, 16) at a second end (18) of the LED tube (1) for connecting the LED tube (1) electronically and mechanically to the fluorescent tube lighting fixture, the first pair of contact pins (8, 10) being connected forming a first circuitry, the second pair of contact pins (14, 16) being connected forming a second circuitry, the LED driver (4) being connected between the first circuitry and the second circuitry, and a temperature controlled switch (20) having an open state and a closed state, and being arranged to adapt the closed state when heated, such that a current path between the first circuitry and the second circuitry is obtained, wherein a preheat current passing between the first pair of contact pins (8, 10) during the preheat phase of the fluorescent tube lighting fixture is arranged to heat the temperature controlled switch.

An electronic ballast with power thermal cutback including an electronic ballast operably connected to provide power to a lamp, the electronic ballast having a PFC converter (HO) operable to receive a PFC input voltage (112) and operable to provide a DC bus voltage on a DC bus (114); a DC/AC converter (120) operable to receive the DC bus voltage from the DC bus (114) and to provide AC power (122) to the lamp (140) at an AC output frequency; a compensator (130) responsive to an electronic ballast condition parameter, the compensator (130) being operable to provide a compensator signal to at least one of the PFC converter (110) and the DC/AC converter (120). At least one of the PFC converter (110) and the DC/AC converter (120) is responsive to the compensator signal to reduce the power to the lamp (140) when the electronic ballast condition parameter passes a threshold.