POWER FACTOR CORRECTION CONTROLLER WITH DIGITAL FIR FILTER OUTPUT VOLTAGE SAMPLING

• US 20080272756A1
• Filed: 12/31/2007
• Published: 11/06/2008
• Est. Priority Date: 05/02/2007
• Status: Abandoned Application

• Current Assignee: Cirrus Logic Incorporated
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Melanson, John L.
• Application Number:
  US11/967,276
• Publication Number:
  US 20080272756A1
• Time in Patent Office: Days
• US Class Current: 323/282
• CPC Class Codes: H02M 1/4225 using a non-isolated boost converter
• CPC Class Codes: H03M 3/476 Non-linear conversion systems
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
• CPC Class Codes: Y02P 80/10 Efficient use of energy, e.g. using compressed air or pressurized fluid as energy carrier

Abstract

A power control system includes a digital FIR filter in an output voltage feedback loop of a switching power converter. A feedback loop includes an output voltage signal of the switching power converter. The output voltage signal includes direct current (DC) and alternating current (AC) components. The FIR filter provides discrete samples of an output voltage feedback signal to a switch state controller that allows the switch state controller to generate a control signal that reflects a relatively quick response to changes in the output voltage signal while reducing an influence of the AC component. In at least one embodiment, the FIR filter is configured to generate the discrete samples at a sampling frequency f_s, the sampling frequency f_s is approximately an integer multiple of a line frequency f_L, and the line frequency f_L is a frequency of a line input voltage supplied to the switching power converter.

Claims

1. An apparatus comprising:

a FIR filter to generate discrete samples of an output voltage feedback signal associated with an output voltage of a switching power converter, wherein the FIR filter is configured to generate the discrete samples at a sampling frequency f_s, the sampling frequency f_s is approximately an integer multiple of a line frequency f_L, and the line frequency f_L is a frequency of a line input voltage supplied to the switching power converter; and

a switch state controller, coupled to the FIR filter, wherein the switch state controller is configured to;

receive a signal associated with the discrete samples generated by the FIR filter;

use the received signal to generate a control signal to provide power factor correction and to regulate the output voltage of the switching power converter; and

provide the control signal to the switching power converter.

2. The apparatus of claim 1 wherein the output voltage feedback signal represents the output voltage of the switching power converter, the apparatus further comprising:

an error generator coupled between the FIR filter and the switch state controller, wherein the error generator is configured to generate the signal received by the switch state controller from a difference between the discrete samples generated by the FIR filter and a reference voltage.

3. The apparatus of claim 1 further comprising:

an error generator to generate the output voltage feedback signal from a difference between an output voltage of the switching power converter and a reference signal.

4. The apparatus of claim 1 wherein the FIR filter includes N taps, wherein N is an integer greater than or equal to 2, and N=f_s/(2·

f_L).

5. The apparatus of claim 4 wherein the discrete samples generated by the FIR filter have a sampling frequency in the range of the line frequency f_L to N·

line frequency f_L wherein N is an integer equal to or greater than one.

6. The apparatus of claim 1 wherein the discrete samples generated by the FIR filter have a sampling frequency equal to the line frequency f_L.

7. The apparatus of claim 1 wherein the FIR filter is a boxcar filter that includes a notch at approximately twice the line frequency f_L.

8. The apparatus of claim 1 wherein the frequency f_s is a member of the group consisting of (i) the line input voltage frequency, (ii) 2 times the line input voltage frequency, and (iii) 4 times the line input voltage frequency.

9. The apparatus of claim 1 wherein the FIR filter is a box car filter having a sampling frequency f_s selected from the group consisting of f_s=f_L, f_s=2·

f_L, and f_s=4·

f_L, and a number of taps, corresponding to the sampling frequency f_s, selected from the group Number of Taps as set forth in Table 2;

Sampling Frequency f_s Number of Taps f_s = f_L 1 f_s = 2 ·

f_L 1 or 2 f_s = 4 ·

f_L 1, 2, or 4

10. The apparatus of claim 1 further comprising:

an input to (i) couple to an output voltage node of the switching power converter and (ii) to receive an output voltage feedback signal corresponding to the output voltage at the output voltage node; and

wherein the switch state controller is further configured to;

respond to changes in the output voltage feedback signal at the frequency f_s.

11. The apparatus of claim 1 further comprising:

a sampler to sample the output voltage at frequency f_s and to generate the output voltage feedback signal.

12. The apparatus of claim 1 further comprising:

an input terminal to receive a signal representing an input current to the switching power converter;

wherein the switch state controller is further configured to also use the signal representing the input current to the switching power converter to generate the control signal to provide power factor correction and to regulate the output voltage.

13. A method of regulating an output voltage of a switching power converter, the method comprising:

generating discrete samples of an output voltage feedback signal associated with an output voltage of a switching power converter using a FIR filter, wherein the FIR filter is configured to generate the discrete samples at a sampling frequency f_s, the sampling frequency f_s is approximately an integer multiple of a line frequency f_L, and the line frequency f_L is a frequency of a line input voltage supplied to the switching power converter;

receiving a signal associated with the discrete samples generated by the FIR filter;

using the received signal to generate a control signal to provide power factor correction and to regulate the output voltage of the switching power converter; and

providing the control signal to the switching power converter.

14. The method of claim 13 wherein the output voltage feedback signal represents the output voltage of the switching power converter, the method further comprising:

generating the signal received by the switch state controller from a difference between the discrete samples generated by the FIR filter and a reference voltage.

15. The method of claim 13 further comprising:

generating the output voltage feedback signal from a difference between an output voltage feedback signal of the switching power converter and a reference signal.

16. The method of claim 13 wherein the FIR filter includes N taps, wherein N is an integer greater than or equal to 2 and N=f_s/(2·

f_L).

17. The method of claim 16 wherein the discrete samples generated by the FIR filter have a sampling frequency in the range of the line frequency f_L to N·

line frequency f_L.

18. The method of claim 13 wherein the discrete samples generated by the FIR filter have a sampling frequency equal to the line frequency f_L.

19. The method of claim 13 wherein the FIR filter has a low pass transfer function with a notch at approximately the sampling frequency f_s.

20. The method of claim 13 wherein the FIR filter is a boxcar filter that includes a notch at approximately twice the line frequency f_L.

21. The method of claim 13 wherein the frequency f_s is a member of the group consisting of (i) the line input voltage frequency, (ii) 2 times the line input voltage frequency, and (iii) 4 times the line input voltage frequency.

22. The method of claim 13 wherein the FIR filter is a box car filter having a sampling frequency f_s selected from the group consisting of f_s=f_L, f_s=2·

f_L, and f_s=4·

f_L, and a number of taps, corresponding to the sampling frequency f_s, selected from the group Number of Taps as set forth in the following table;

Sampling Frequency f_s Number of Taps f_s = f_L 1 f_s = 2 ·

f_L 1 or 2 f_s = 4 ·

f_L 1, 2, or 4

23. The method of claim 13 further comprising:

receiving an output voltage feedback signal corresponding to the output voltage of the switching power converter;

responding to changes in the output voltage feedback signal at the frequency f_s.

24. The method of claim 13 further comprising:

sampling the output voltage at frequency f_s; and

generating the output voltage feedback signal.

25. The method of claim 13 further comprising:

receiving a signal representing an input current to the switching power converter; and

using the signal representing an input current to the switching power converter to generate the control signal to provide power factor correction and to regulate the output voltage.

26. An apparatus for regulating an output voltage of a switching power converter, the apparatus comprising:

a FIR filter to generate discrete samples of an output voltage feedback signal associated with an output voltage of a switching power converter, wherein the FIR filter is configured to generate the discrete samples at a sampling frequency f_s, the sampling frequency f_s is approximately an integer multiple of a line frequency f_L, and the line frequency f_L is a frequency of a line input voltage supplied to the switching power converter;

means for receiving a signal associated with the discrete samples generated by the FIR filter;

means for using the received signal to generate a control signal to provide power factor correction and to regulate the output voltage of the switching power converter; and

means for providing the control signal to the switching power converter.