Embodiments relate to a LED lighting system comprising a power supply circuit for supplying a power supply current to a LED strip (200). The power supply circuit (100) includes input terminals (K1, K2) for receiving a power voltage from a power supply voltage, output terminals (K3, K4) connected to the input terminals of the LED strip (200), a sensing module (106) coupled between the output terminals (K3, K4) for measuring an impedance of the LED strip (200). The sensing module is adapted to drive a switch (104) and to transmit a measured impedance value to a driver module (108). The driver module (108) is adapted to generate the power supply current depending on the length of the LED strip (200), as reflected by the measured impedance value.