Patent ID: 8704455

Claim:
A method, comprising: determining a sampling time to take a sample of a first current on a primary side of a transformer, wherein the sampling time is determined based on a turn on time of a switch coupled to the primary side; taking the sample of the first current on the primary side of the transformer at the sampling time; calculating an area of a second current on a secondary side of the transformer using i) the sample of the first current taken on the primary side and ii) a turn ratio of the transformer; and outputting a signal to control the turn on time for the switch, wherein the signal controls the turn on time for the switch based on the calculated area of the second current, wherein calculating the area of the second current on the secondary side of the transformer includes calculating the area of the second current according to I P ⁡ ( T ON 2 ) N * T OFF ⁡ ( t ) , where I p corresponds to the sample taken of the first current, T ON corresponds to the turn on time of the switch, N corresponds to the turn ratio of the transformer, and T OFF corresponds to a turn off time of the switch.