Patent ID: 8310326

Claim:
A method, comprising: calculating a first number of turns of a shield winding included in an energy transfer element of a power supply, wherein the first number of turns of the shield winding is greater than zero and is calculated for the power supply to have a low noise current in an input conductor of the power supply; increasing the first number of turns for the shield winding to a second number of turns, wherein the second number of turns is greater than the first number of turns; operating the power supply to generate a first voltage waveform of a voltage between the input conductor and an output conductor of the power supply; after operating the power supply to generate the first voltage waveform, inserting an impedance between the shield winding and the input conductor of the power supply; and reducing the noise current in the input conductor by adjusting a value of the impedance until a second voltage waveform of the voltage between the input conductor and the output conductor of the power supply reverses polarity to be the opposite of a polarity of the first voltage waveform in response to the adjusting of the value of the impedance.