A power converter powers an LED fixture from a power supply, and comprises a primary circuit a primary winding; and a switch in series connection with the primary winding to in a conductive state of the switch connect the primary winding to the power supply; a secondary circuit comprising a secondary winding that is magnetically coupled with the primary winding for providing power to the LED fixture in response to a switching of the switch; the power converter further comprising: the power converter further comprising: a sensing circuit configured to generate a signal representative of the output voltage of the secondary winding, an edge of the signal representing an edge of the output voltage of the secondary winding in response to the switching of the switch; and a detecting circuit configured to derive timing data from the edges of the signal, to estimate a load of the power converter from at least one output parameter of the power converter, and to determine a momentary value of a voltage of the power supply from the timing data and the estimated load of the power converter.