Startup circuit for DC-DC converter

A startup circuit for use in a DC-DC converter having an input voltage terminal and an output voltage terminal, with the output voltage terminal connected to an output capacitor and with said converter including a pass transistor for transferring charge from the input terminal to the output terminal so that the output voltage increases to a voltage equal to the input voltage during converter startup, said start up circuit comprising:

• a pass transistor control circuit configured to cause the pass transistor to conduct an output current during start up when the output terminal voltage is approaching a final regulated voltage, said output current being adjusted so as to maintain power dissipation in the converter within ±20% of a dissipation level for a duration of at least half a time required for the output voltage to increase from a value equal to 10% on the input voltage to a value equal to 90% of the input voltage.