Patent ID: 7218066

Claim:
Detector ( 100 ) for sensing a current and for generating an output signal (S D ) indicative of said current crossing zero, the detector comprising a transformer ( 110 ) having a primary winding ( 111 ) for receiving the current to be sensed and further comprising a secondary winding ( 112 ) inductively coupled to said primary winding ( 111 ), the transformer ( 110 ) being designed such as to be magnetically saturated already at a very low current saturation level; a first diode ( 113 ) having a first terminal (anode) coupled to a first end terminal of the secondary winding ( 112 ); a second diode ( 114 ) having a first terminal (anode) coupled to a second end terminal of the secondary winding ( 112 ) and having its second terminal (cathode) connected to the second terminal (cathode) of the first diode ( 113 ); a resistor ( 115 ) having one terminal connected to the node between said two diodes ( 113 , 114 ) and having its other terminal coupled to a central tap of the secondary winding ( 112 ).