Patent ID: 6980783

Claim:
In a telecommunications system, a circuit for reducing low frequency noise currents drawn from a DC power supply by a load circuit using AC power at low frequencies, said circuit comprising: a) a power converter for converting an input voltage to a desired output voltage by repeatedly switching said input voltage on and off; b) a first sense circuit for sensing an input signal to said power converter wherein the first sense circuit includes a low pass filter for providing an average value of the input signal; c) a second sense circuit for sensing a load signal at said load circuit; d) a comparator, coupled to said second sense circuit, for determining and providing as an output a difference signal representative of a difference between said load signal at said load circuit and a predefined reference voltage, said comparator having a limited bandwidth compared to an AC load requirement; and e) a power converter control circuit, having inputs connected to said first sense circuit via said low pass filter and to said comparator output, and output connected to said power converter, for controlling a duty cycle of switching of said power converter in accordance with a relationship between said input signal and said difference signal of said comparator.