In a resonance converter for driving variable loads at first an input
signal provided by a switch controlled by control means is converted to
an output signal by a transformer. The transformer is dimensioned and
connected such that a downward transformation ratio between input signal
and output signal is between 5:1 and 100:1 when providing nominal power
to the variable load. The switching frequency of the switch is controlled
on the basis of a phase shift between a switch current and a load current
at variable load and/or variable input voltage, a quantity dependent on
the input voltage, as well as a quantity dependent on the output voltage.
The inventive resonance converter further enables driving variable loads
efficiently with the aid of a transformer.