An apparatus coupling a power source to a light emitting diode lamp includes a first part for receiving first voltage and current signals from the power source and a second part for supplying second voltage and current signals to the lamp. The first part includes a detection part for detecting a first amplitude reduction in at least one of the first signals, for example in the first voltage signal, and the second part includes an introduction part for, in response to a detection result, introducing a second amplitude reduction into at least one of the second signals, for example into the second current signal. As a result, the first part detects a first dimming state caused by the power source, and the second part introduces a second dimming state in response to the first part having detected the first dimming state, and the apparatus has self-dimming capabilities, to keep the grid stable.