Patent ID: 7649755

Claim:
A switched mode power supply comprising a transformer having a primary winding and at least one secondary winding, a first rectifier means coupled to said secondary winding for providing a rectified voltage, a switching transistor arranged in series with said primary winding, and a control circuit with a driver stage coupled to a control input of the switching transistor for controlling an output voltage, the control circuit comprising an oscillator with a terminal, to which a first capacitor is coupled and the control circuit providing a reference voltage for charging said capacitor for determining the oscillation frequency of said oscillator for a start-up, phase, a start-up circuit coupled to a second capacitor for providing an operating voltage for the control circuit, a third rectifier means coupled between said first rectifier means an the second capacitor for charging the second capacitor during operation of the switched mode power supply, wherein said terminal is further coupled via a resistor to said rectified voltage at a node between said first rectifier means and third rectifier means, for providing an additional charge current for said capacitor for increasing the oscillation frequency of the oscillator during operation, with regard to the start-up phase.