초록 ▼

A circuit controls the low frequency load currents drawn by components of telecommunications systems. The circuit includes a power converter, a first sense circuit, a second sense circuit, a comparator, and a power converter control circuit. The power converter control circuit controls the power con

A circuit controls the low frequency load currents drawn by components of telecommunications systems. The circuit includes a power converter, a first sense circuit, a second sense circuit, a comparator, and a power converter control circuit. The power converter control circuit controls the power converter's duty cycle in accordance with the input signal compared to a reference. In this manner, the low frequency load currents may be easily and economically controlled.

대표청구항 ▼

1. 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 sa

1. 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; ande) 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.2. A circuit as defined in claim 1, further comprising an input amplifier for amplifying said input signal.3. A circuit as defined in claim 2, wherein said comparator further includes a difference amplifier for amplifying said difference.4. A circuit as defined in claim 3, wherein said input amplifier and said difference amplifier amplify said input signal and said difference, respectively, to a common order of magnitude.5. A circuit as defined in claim 1, further comprising a high frequency filter, coupled between said DC power supply and said power converter, for reducing a high frequency noise component introduced by switching of said power converter.6. A circuit as defined in claim 1, wherein said load circuit comprises a fan for cooling said telecommunications system.7. 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) power converter means for converting an input voltage to a desired output voltage by repeatedly switching said input voltage on and off;b) first sense circuit means for sensing an input signal to said power converter means wherein the first sense circuit means includes low pass filter means for providing an average value of the input signal;c) second sense circuit means for sensing a load signal at said load circuit;d) comparator means, coupled to said second sense circuit means, 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 means having a limited bandwidth compared to an AC load requirement; ande) power converter control circuit means, having inputs connected to said first sense circuit and to said comparator output, and output connected to said power converter, for controlling a duty cycle of switching of said power converter means in accordance with a relationship between said input signal and said difference signal of said comparator means.8. A circuit as defined in claim 7, further comprising an input amplifier means for amplifying said input signal.9. A circuit as defined in claim 8, wherein said comparator means further includes difference amplifier means for amplifying said difference.10. A circuit as defined in claim 9, wherein said input amplifier means and said difference amplifier means amplify said input signal and said difference, respectively, to a common order of magnitude.11. A circuit as defined in claim 7, further comprising high frequency filter means, coupled between said DC power supply and said power converter means, for reducing a high frequency noise component introduced by switching of said power converter means.12. A circuit as defined in claim 7, wherein said load circuit comprises fan means for cooling said telecommunications system.