ACTIVE VOICE BAND NOISE FILTER

• US 20120206116A1
• Filed: 02/11/2011
• Published: 08/16/2012
• Est. Priority Date: 02/11/2011
• Status: Active Grant

• Current Assignee: Alcatel-Lucent SA (Nokia Corporation)
• Original Assignee: Alcatel-Lucent USA, Inc. (Nokia Corporation)
• Inventors: Fricker, Jean-Philippe
• Granted Patent: US 8,937,465 B2
• Time in Patent Office: Days
• US Class Current: 323/271
• 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 filtering circuit comprising:

a current sensor for sensing a current;

a boost converter comprising a boost inductor, a boost switch, a boost diode and at least one energy storage capacitor; and

a buck converter comprising a buck inductor, a buck switch and a buck diode,

wherein the current sensor, the boost converter and the buck converter are connected in series.

2. The filtering circuit of claim 1, further comprising an integrated circuit coupled to the boost switch, wherein the integrated circuit is adapted to control the operation of the boost switch in order to provide a boost voltage to the buck converter.

3. The filtering circuit of claim 2, wherein the boost converter further comprises a feedback loop for providing feedback from an output of the boost converter to the integrated circuit.

4. The filtering circuit of claim 1 further comprising a voltage filter, wherein the voltage filter is connected downstream of the boost converter and comprises at least one capacitor coupled to ground.

5. The filtering circuit of claim 1, wherein the boost switch comprises a transistor.

6. The filtering circuit of claim 5, wherein the transistor is a metal-oxide semiconductor field effect transistor, and wherein the boost switch is adapted to be controlled by manipulating a gate voltage applied to the transistor.

7. The filtering circuit of claim 1, further comprising an integrated circuit coupled to the buck switch, wherein the integrated circuit is adapted to control the operation of the buck switch in order to provide the predetermined output voltage to a load.

8. The filtering circuit of claim 7, further comprising an output voltage divider downstream of the buck converter, wherein the output voltage divider is adapted to provide feedback from an output of the buck converter to the integrated circuit.

10. The filtering circuit of claim 1 further comprising at least one bypass capacitor downstream of the current sensor and upstream of the boost converter, wherein the at least one bypass capacitor is coupled to the circuit and to ground.

11. The filtering circuit of claim 1 further comprising at least one bypass capacitor downstream of the buck converter, wherein the at least one bypass capacitor is coupled to the circuit and to ground.

12. 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, at least one energy storage capacitor, 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 boost converter, and wherein the at least one energy storage capacitor is 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.

13. The circuit according to claim 12, 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.

14. The circuit according to claim 12, 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.

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

16. The circuit according to claim 12, wherein the load comprises at least one fan.

17. A method for actively filtering conducted noise from power delivered to a load from a power supply, the method comprising:

providing an input voltage and an input current to a boost converter from a power source;

operating the boost converter to provide a boost voltage to a buck converter, wherein the boost voltage equals or exceeds the input voltage;

maintaining a predetermined charge level on at least one energy storage capacitor using the boost voltage;

providing the boost voltage to a buck converter; and

operating the buck converter to provide power to the load at a predetermined voltage level.

18. The method according to claim 17, wherein the operation of the boost converter is controlled by an integrated circuit, and wherein the method further comprises the steps of providing feedback from the output of the boost converter to the integrated circuit, and operating the boost converter to increase or decrease the boost voltage based on the feedback.

19. The method according to claim 17, wherein the at least one energy storage capacitor is coupled between a common node and ground, wherein the common node is between the boost converter and the buck converter.

20. The method according to claim 17, wherein the predetermined voltage level is 12 volts (V).