Patent ID: 7672149

Claim:
A device ( 1 ) for feeding electrical energy from an energy source with variable source voltage into an electric power supply network ( 15 ), said device ( 1 ) including a transformer ( 112 ) for galvanic isolation, a resonant inverter ( 11 ) with semi-conductor switches (a-d; A, B), one or several resonant capacitors ( 17 ; 18 , 19 ; 20 , 21 ) and one rectifier ( 113 ), characterized in that the device ( 1 ) does not comprise a boost chopper or a buck chopper, and that the resonant inverter ( 11 ) is operated in a full resonant mode if an operating voltage is in a maximum power operation point (MPP) that exists in normal operation, whereby in the maximum power point (MPP) the current from the transformer ( 112 ) is a current made from sinusoidal half-waves, and the resonant inverter ( 11 ) is operated in a hard-switching mode if the voltages exceed the maximum operation point (MPP), so that the current from the transformer ( 112 ) comprises sine-wave portions, whereby the hard-switching mode only occurs in a start-up phase.