Patent ID: 8817493

Claim:
A method for controlling a voltage across a primary coil in an adapter transformer, comprising: during each of one or more intervals, applying a first voltage pulse across the primary coil in a start direction, wherein the start direction alternates between a first direction and a second direction each interval; applying a predetermined number of subsequent voltage pulses across the primary coil, wherein the subsequent voltage pulses alternate between the first direction and the second direction; applying a last voltage pulse voltage across the primary coil; and reducing the voltage across the primary coil for a predetermined time; wherein at least one of a frequency at which the direction of the predetermined number of subsequent voltage pulses across the primary coil is alternated, the predetermined number of times the direction of the voltage pulse across the primary coil is alternated, and the predetermined time that the voltage across the primary coil is reduced is changed based on a power demand from the adapter transformer.