Apparatus and method of controlling low frequency load currents drawn from a DC source in a telecommunications system

• US 20040204173A1
• Filed: 10/03/2002
• Published: 10/14/2004
• Est. Priority Date: 05/31/2002
• Status: Active Grant

• Current Assignee: Catena Networks, Inc. (Ciena Corporation), Potentia Telecom Power Incorporated
• Original Assignee: Catena Networks, Inc. (Ciena Corporation), Potentia Telecom Power Incorporated
• Inventors: Orr, Raymond, Xu, Kai, Liu, Yan-Fei
• Granted Patent: US 6,980,783 B2
• Time in Patent Office: Days
• US Class Current: 455/572
• CPC Class Codes: H02M 1/0009 Devices or circuits for detecting current in a converter
• CPC Class Codes: H02M 1/0022 the disturbance parameters being input voltage fluctuations
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators

Abstract

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.

Claims

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 that converts an input voltage to a desired output voltage by repeatedly switching said input voltage on and off;

b) a first sense circuit that senses an input signal to said power converter;

c) a second sense circuit that senses a load signal at said load circuit;

d) a comparator, coupled to said second sense circuit, that determines and provides as its output a difference signal representative of a difference between said load signal at said load circuit and a predefined reference voltage, wherein said comparator has a limited bandwidth as compared to an AC load requirement;

e) a power converter control circuit, having its inputs coupled to said first sense circuit and said comparator output, and its output coupled to said power converter, that controls 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, wherein said first sense circuit further includes a low pass filter that provides an average value of said input signal.

3. A circuit as defined in claim 2, further comprising an input amplifier that amplifies said input signal.

4. A circuit as defined in claim 3, wherein said comparator further includes a difference amplifier that amplifies said difference.

5. A circuit as defined in claim 4, wherein said input amplifier and said difference amplifier amplify said input signal and said difference, respectively, to a common order of magnitude.

6. A circuit as defined in claim 1, further comprising a high frequency filter, coupled between said DC power supply and said power converter, that reduces a high frequency noise component introduced by switching of said power converter.

7. A circuit as defined in claim 1, wherein said load circuit comprises a fan that cools said telecommunications system.

8. 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;

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 its output a difference signal representative of a difference between said load signal at said load circuit and a predefined reference voltage, wherein said comparator means has a limited bandwidth as compared to an AC load requirement;

e) power converter control circuit means, having its inputs coupled to said first sense circuit and said comparator output, and its output coupled 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.

9. A circuit as defined in claim 8, wherein said first sense circuit means further includes low pass filter means for providing an average value of said input signal.

10. A circuit as defined in claim 9, further comprising an input amplifier means for amplifying said input signal.

11. A circuit as defined in claim 10, wherein said comparator means further includes difference amplifier means for amplifying said difference.

12. A circuit as defined in claim 11, wherein said input amplifier means and said difference amplifier means amplify said input signal and said difference, respectively, to a common order of magnitude.

13. A circuit as defined in claim 8, 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.

14. A circuit as defined in claim 8, wherein said load circuit comprises fan means for cooling said telecommunications system.