Patent ID: 7521910

Claim:
Method for measuring a switched current which is periodically switched on and off with use of a switch, and providing a measuring signal accurately reflecting said switched current, the method comprising: sensing said switched current with a current sensor to obtain an intermediate measuring signal corresponding to an AC part of said switched current, wherein the current sensor includes an AC current transformer having a primary winding coupled in series with the switch, the AC current transformer further having a secondary winding for providing the intermediate measuring signal; receiving a timing signal indicating the on and off periods of the switched current; during an off period of the switch, generating an auxiliary signal such that the sum of (i) said intermediate measuring signal during the off period and (ii) said auxiliary signal generated during the off period is equal to zero; and during an on period of the switch, summing (i) said intermediate measuring signal during the on period and (ii) said auxiliary signal that was generated during the off period; and providing the sum signal from the off period and from the on period as the measuring signal of the switched current, the measuring signal reflecting an actual value of the AC part and a DC part of the switched current.