Reducing noise from unshielded coupling in switch mode power supply

A switch mode power supply comprises a power input 102, a switch 104, a transformer 150, and a power output 118. The transformer has a primary winding 152 coupled to said power input via said switch, and a secondary winding 156 coupled to said power output. The transformer further comprises an auxiliary winding 154 and a coupling structure 161 capacitatively coupled to said secondary winding of said transformer; wherein said coupling structure does not comprise a shield or screen between said primary and secondary windings. The switch mode power supply further comprises a coupling capacitor 162 connected between said coupling structure and said auxiliary winding to provide a noise suppression voltage from said auxiliary winding to said secondary winding to at least partially cancel a common mode noise voltage on said secondary winding from unshielded coupling from said primary winding.

Noise reduction systems and methods