Patent ID: 7330018

Claim:
A step-down controller circuit having an input having a first and a second input terminal for the purpose of applying an input voltage (U c ); an output having a first and a second output terminal at which an output voltage (U a ) can be provided; a series circuit comprising a switch (S I ) and an inductance (L T ) which is coupled between the first input terminal and the first output terminal, the switch (S I ) having a control input (St) for the purpose of applying a control signal; a first diode (D 1 ) which is coupled between the junction point between the switch (S I ) and the inductance (L T ) and a reference potential such that, when the inductance (L T ) is freewheeling, a current flow through the first diode (D 1 ) is possible; characterized in that it also comprises a snubber network which comprises a snubber capacitor (C ent ), a second diode (D 2 ), a third diode (D 3 ) and an auxiliary inductance (L H ), a series circuit comprising the snubber capacitor (C ent ), the third diode (D 3 ) and the auxiliary inductance (L H ) being coupled in parallel with the inductance (L T ), and the second diode (D 2 ) being coupled with its first terminal to the reference potential and with its second terminal to the junction point between the snubber capacitor (C ent ) and the third diode (D 3 ), the second diode (D 2 ) being polarized, as the first diode (D 1 ), with respect to the reference potential, and the third diode (D 3 ) being polarized with respect to the second diode (D 2 ) such that a current flow through a series circuit comprising the second diode (D 2 ) and the third diode (D 3 ) is possible.