Active voice band noise filter

• US 8,937,465 B2
• Filed: 02/11/2011
• Issued: 01/20/2015
• Est. Priority Date: 02/11/2011
• Status: Active Grant

• Current Assignee: Alcatel-Lucent SA (Nokia Corporation)
• Original Assignee: Alcatel-Lucent SA (Nokia Corporation)
• Inventors: Fricker, Jean-Philippe
• Primary Examiner(s): Berhane, Adolf
• Assistant Examiner(s): GBLENDE, JEFFREY A
• Application Number:
  US13/025,787
• Publication Number:
  US 20120206116A1
• Time in Patent Office: 1,439 Days
• Field of Search: 323/223, 323/224, 323/234, 323/265, 323/271, 323/273, 323/274, 323/282, 323284-286
• US Class Current: 323/274
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 1/15 using active elements
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load

Abstract

Systems and methods for actively reducing or eliminating conducted noise from power provided to DC circuits include a current sensor, a boost converter, a buck converter, and energy supply capacitors. The current sensor senses the input current provided by the power source. The boost converter increases the voltage level above that provided by the power source while maintaining current at or near the level sensed by the current sensor, and while also maintaining a charge on the energy supply capacitors. The buck converter is powered by the output from the boost converter and provides an output voltage to a load. The operation of the boost converter and the buck converter may be controlled to maintain a continuous and low ripple current from the power source and to maintain a continuous and low ripple voltage to the load.

Claims

1. A circuit for actively filtering noise from power applied to a load, the circuit comprising:

a current sensor for sensing an input current;

a boost converter comprising a first inductor, a first diode, a first switch, and a first integrated circuit for operating the first switch, wherein the boost converter is adapted to provide a boost voltage that is at least as large as an input voltage to the buck converter;

at least one energy storage capacitor coupled to the circuit downstream of the boost converter;

a first feedback loop comprising a first zener diode, wherein the first feedback loop is adapted to provide feedback from an output of the boost converter to the first integrated circuit when the boost voltage exceeds a predetermined voltage level by a breakthrough voltage of the first zener diode;

a low-pass filter downstream of the first feedback loop; and

a buck converter comprising a second inductor, a second diode, a second switch and a second integrated circuit for operating the second switch, wherein the buck converter is adapted to provide an output voltage to the load at a predetermined output voltage level,

wherein the low-pass filter comprises a second zener diode and at least one filter capacitor coupled to the circuit and to ground, and

wherein the low-pass filter is adapted to provide feedback to the first integrated circuit via the first feedback loop.

2. The circuit according to claim 1, further comprising a voltage divider coupled to the circuit downstream of the buck converter, wherein the voltage divider comprises a second feedback loop for providing feedback to the second integrated circuit.

3. The circuit according to claim 1, wherein the predetermined voltage level is 12 volts (V).

4. The circuit according to claim 1, wherein the load comprises at least one fan.

5. The circuit according to claim 2, wherein the voltage divider further comprises two resistors coupled in series to the circuit downstream of the buck converter and to ground and a filtering capacitor coupled to the circuit and to ground,

wherein the filtering capacitor is coupled to the circuit between the two resistors.

6. The circuit according to claim 1, wherein the current sensor comprises a sense resistor, a gain resistor and a current amplifier.

7. The circuit according to claim 6, wherein the current amplifier further comprises an operational amplifier and at least one transistor.

8. The circuit according to claim 1, further comprising at least one bypass capacitor provided downstream of the current sensor and upstream of the boost converter.

9. The circuit according to claim 8, wherein the at least one bypass capacitor comprises a first bypass capacitor for providing high frequency impedance to the circuit and a second bypass capacitor for providing low frequency impedance to the circuit.

10. The circuit according to claim 9, wherein the first bypass capacitor has a first capacitance of approximately 0.1 microfarad, and

wherein the second bypass capacitor has a second capacitance of approximately 22 microfarad.

11. A cooling system comprising:

at least one fan; and

at least one filtering circuit,

wherein the at least one filtering circuit is configured to receive an input voltage and an input current,

wherein the at least one filtering circuit is configured to provide an output voltage and an output current to the at least one fan, and

wherein the at least one filtering circuit comprises;

a current sensor for sensing the input current;

a boost converter comprising a first inductor, a first diode, a first switch, and a first integrated circuit for operating the first switch, wherein the boost converter is adapted to provide a boost voltage that is at least as large as the input voltage to the buck converter;

at least one energy storage capacitor coupled to the at least one filtering circuit downstream of the boost converter;

a first feedback loop comprising a first zener diode, wherein the first feedback loop is adapted to provide feedback from an output of the boost converter to the first integrated circuit when the boost voltage exceeds a predetermined voltage level by a breakthrough voltage of the first zener diode;

a low-pass filter downstream of the first feedback loop; and

a buck converter comprising a second inductor, a second diode, a second switch and a second integrated circuit for operating the second switch, wherein the buck converter is adapted to provide the output voltage to the at least one fan at a predetermined output voltage level,

wherein the low-pass filter comprises a second zener diode and at least one filter capacitor coupled to the at least one filtering circuit and to ground, and

wherein the low-pass filter is adapted to provide feedback to the first integrated circuit via the first feedback loop.

12. The cooling system according to claim 11, wherein the filtering circuit further comprises a voltage divider coupled to the circuit downstream of the buck converter, and

wherein the voltage divider comprises a second feedback loop for providing feedback to the second integrated circuit.

13. The cooling system according to claim 12, wherein the voltage divider further comprises two resistors coupled in series to the circuit downstream of the buck converter and to ground and a filtering capacitor coupled to the circuit and to ground,

wherein the filtering capacitor is coupled to the circuit between the two resistors.

14. The cooling system according to claim 11, wherein the predetermined voltage level is 12 volts (V).

15. The cooling system according to claim 11, wherein the current sensor comprises a sense resistor, a gain resistor and a current amplifier.

16. The cooling system according to claim 11, wherein the current amplifier further comprises an operational amplifier and at least one transistor.

17. The cooling system according to claim 11, further comprising at least one bypass capacitor provided downstream of the current sensor and upstream of the boost converter.

18. The cooling system according to claim 17, wherein the at least one bypass capacitor comprises a first bypass capacitor for providing high frequency impedance to the circuit and a second bypass capacitor for providing low frequency impedance to the circuit.

19. The cooling system according to claim 18, wherein the first bypass capacitor has a first capacitance of approximately 0.1 microfarad, and

wherein the second bypass capacitor has a second capacitance of approximately 22 microfarad.

20. The cooling system according to claim 11, wherein the at least one fan is provided in a tray.