Start up circuit for commutation power supplies

摘要

The present invention relates to a start up circuit for commutation power supplies (PWM) or DC/DC converters and to a commutation type power supply comprising such a start up circuit. In an embodiment the start up circuit for commutation power supplies having an input terminal (In) and an output terminal (OUT) comprises: a first current generator (41) able to supply a first prefixed current (I) connected between said input terminal (In) and a first node (45); said first node (45) is coupled to said output terminal (OUT); characterized by further comprising a second current generator (42) able to supply a second prefixed current (K*I) connected between said input terminal (In) and a first terminal of a first controlled switch (44); the value of said second prefixed current (K*I) is greater than or equal to the value of said first prefixed current (I); a second terminal of said first controlled switch (44) is connected to said first node (45); a control circuit (43, V3) of said first controlled switch (44) able to maintain closed said first controlled switch (44) in the case in which the voltage on said output terminal (OUT) is lower than a first prefixed voltage (V3). (FIG. 4).