Patent ID: 7167381

Claim:
A power supply unit comprising: a switching device ( 18 ) for converting an intermediate circuit voltage (U z ) into a switched voltage (U WR ); a resonant circuit ( 20 ) that is fed by the switched voltage (U WR ) and has a transformer (T) for supplying an output voltage; and a control device ( 30 , 32 ) for setting at least one correcting variable (T PW ), the control device being configured for converting the correcting variable (T PW ) into values of wait time interval (T W ) and active phase time interval (T P ) for actuating the switching device ( 18 ) according to a non-linear relationship between T p , T W and T PW for three operating modes of mixed mode modulation, the three operating modes corresponding to low output power, medium output power, and high output power modes, wherein the control device ( 30 , 32 ) is configured to process sample values of at least a first actual value (U out ) which depends on the output voltage, and to calculate a time difference value (ΔU out ) from two sample values, wherein the time difference value (ΔU out ) is multiplied by a first controller coefficient (k out ) and the result is used in the calculation of the correcting variable (T PW ), and wherein the value of the first controller coefficient (k out ) is changeable as a function of the operating point of the power supply unit.