Switched-mode power supply device having an input for receiving an AC voltage input signal, an output for providing a DC voltage signal and/or a direct-current signal to a downstream consumer, a transformer having a primary winding and a secondary winding, and resonant converter means assigned to the primary side of the transformer, which resonant converter means form an LLC topology with inclusion of the primary winding and can be actuated with a variable-frequency control signal on the primary side by means of a control unit, wherein the control unit, which is realized by means of an integrated and/or programmable circuit component, generates the control signal in reaction to and as a function of a zero-crossing detection signal generated from the AC voltage input signal, a current flowing in the transformer windings, in particular on the secondary side, and a constant and/or predeterminable preset signal for an output current flowing at the output, in such a way that regulating means associated with the control unit regulate the output current to the preset signal, and a phase of an input current flowing in the input is synchronized to the phase of the AC voltage input signal, wherein means for generating a sinusoidal signal profile are associated with the regulating means, which signal profile-generating means are independent of the AC voltage input signal and act independently thereof.