US Patent 9480123 LED retrofit lamp

The present invention relates to an LED retrofit lamp adapted for operation with an alternating current. The LED lamp comprises an LED unit, first and second switching devices (e.g., first and second relays), a startup voltage supply unit (1010) coupled in parallel to the first switching device, an ignition detection unit (1020) coupled in parallel to the second switching device, and a switch drive unit (1030) for setting the first and second switching devices to a conducting state. If one of the first and second switching devices is shorted either no startup supply voltage or no detection signal is provided, such that the failure is indicated externally to a user.