Power supplies and methods for reducing common mode noise

A method of reducing common mode noise in a switched-mode power supply, the power supply including an input for receiving an input voltage from a voltage source, an output for providing an output voltage to a load, and a transformer having a primary winding, a secondary winding, and a conductive shield disposed between the primary winding and the secondary winding, the method comprising:

• measuring a common mode noise between the primary winding and the secondary winding of the transformer;
• automatically generating an adjustable neutralization signal in response to the measured common mode noise between the primary winding and the secondary winding of the transformer by adjusting at least one of a potentiometer, an adjustable gain amplifier and a second transformer;
• and
• applying the adjustable neutralization signal to the conductive shield to reduce the common mode noise between the primary winding and the secondary winding of the transformer, wherein the neutralization signal has substantially the same amplitude and opposite phase of the measured common mode noise.