Patent ID: 7521990
Filing Date: 2009-04-21
Classification: H03K,H04B

Abstract:
1. An electronic noise-filtering circuit for removing noise from the neural leg of an alternating current power source, wherein the alternating current has a substantially fixed frequency and is delivered to a load circuit by way of three electrical conductors, with said system including generator for generating the alternating current and receiving returned alternating current, The generator being electrically connected to a hot first conductor for carrying the alternating current to the load circuit and a neutral second conductor for returning the alternating current from the load circuit to the generator, and a ground third conductor for providing a current oath to Earth ground, and wherein the load circuit receives the alternating current via the hot first conductor and returns the alternating electrical current via the neutral second conductor and has a local Earth around connection electrically connected to the ground third conductor, said noise-filtering circuit comprising: a first input terminal for connecting to said hot first conductor; a second input terminal for connecting to said neutral second conductor; a third input terminal for connecting to said ground third conductor; an output terminal for connecting to said neutral second conductor; first and second rectifying diodes; an operational amplifier; and a transformer; wherein said first input terminal and said second input terminal are connected across the primary windings of said transformer; one side of the secondary winding of said transformer being connected to said second input terminal, and the other side of said secondary winding of said transformer being connected to the anode of said first rectifying diode and the cathode of said second rectifying diode; said transformer sending to said anode of said first rectifying diode and said cathode of said second rectifying diode either a stepped-down or boosted version of the alternating current signal received across said hot first conductor; said first rectifying diode passing only the positive half of the alternating current signal to a positive power source input of said operational amplifier, and said second rectifying diode passing only the negative half of the alternating current signal to a negative power source input of said operational amplifier; said third input terminal being directly in communication with a non-inverting input of said operational amplifier; said operational amplifier being arranged for unity gain throughput; said operational amplifier receives and amplifies the voltage on said ground third conductor; the output of said operational amplifier being in communication with said output terminal through which the amplified version of said voltage on said ground third conductor is delivered to said neutral second conductor, thereby eliminating, on the load circuit side of said noise-filtering circuit the noise-generated instantaneous differences in voltage between said ground third conductor and said second neutral conductor.