Abstract: A device and a method for operating a low power switch mode power supply, where DC input power is converted to AC power by an oscillator, which AC power is transformed to an AC voltage and AC current, which output power is converted into DC power, where the DC voltage is used as a feedback signal for controlling the oscillator. It is the objective of the invention to reduce a standby power consumption of power consuming devices. The oscillator comprises a first and a second current loop, which first current loop generates an activation current for the second current loop, where the primary coil of a transformer is part of the second current loop, and where the second loop comprises a current/voltage measuring system and generates increasing current in the second current loop and closes the current flow in the second current loop.