US Patent 10122252 Supply voltage management

A method for the start-up and/or the maintenance of a supply voltage for a driver circuit for a solid state light source is described. The driver circuit comprises a switched-mode power converter with a switch and a transformer. The switched-mode power converter converts an input voltage into an output voltage. The driver circuit has a controller which generates a gate control signal for putting the power converter switch into an on-state or an off-state. The driver circuit comprises a supply voltage capacitor to provide a voltage to the controller. A primary coil of the transformer is arranged in series with the power converter switch. A secondary coil arrangement of the transformer provides the output voltage. and is coupled to the supply voltage capacitor via a supply voltage transistor which is controlled such that the supply voltage provided by the supply voltage capacitor lies within a pre-determined voltage interval.