System and method for controlling variations of switching frequency

• US 20060221646A1
• Filed: 04/07/2005
• Published: 10/05/2006
• Est. Priority Date: 03/30/2005
• Status: Active Grant

• Current Assignee: On-Bright Electronics (Shanghai) Co., Ltd. (Orthosie Investment Holdings Ltd.)
• Original Assignee: On-Bright Electronics (Shanghai) Co., Ltd. (Orthosie Investment Holdings Ltd.)
• Inventors: Ye, Jun, Zhao, Shifeng, Chen, Zhiliang, Fang, Lieyi, Zhu, Zhen
• Granted Patent: US 7,684,462 B2
• Time in Patent Office: Days
• US Class Current: 363/13
• CPC Class Codes: H02M 1/44 Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H03K 7/08 Duration or width modulation ; Duty cycle modulation

Abstract

System and method for providing frequency control to a power converter. The system includes a pseudorandom signal generator configured to generate a digital signal. The digital signal is associated with at least an N-bit datum, and N is a positive integer. Additionally, the system includes a digital-to-analog converter configured to receive the digital signal and generate a first control signal, an output signal generator configured to receive the first control signal and generate at least a first output signal associated with a frequency, and a pulse-width-modulation generator configured to receive at least the first output signal. The N-bit datum represents a pseudorandom number.

Claims

1. A system for providing frequency control to a power converter, the system comprising:

a pseudorandom signal generator configured to generate a digital signal, the digital signal associated with at least an N-bit datum, N being a positive integer;

a digital-to-analog converter configured to receive the digital signal and generate a first control signal;

an output signal generator configured to receive the first control signal and generate at least a first output signal associated with a frequency;

a pulse-width-modulation generator configured to receive at least the first output signal;

wherein the N-bit datum represents a pseudorandom number.

2. The system of claim 1 wherein

the pseudorandom signal generator includes an m-stage M-sequence generator, m being a positive integer;

the m-stage M-sequence generator is configured to receive the first output signal.

3. The system of claim 1 wherein:

the first output signal is associated with a first signal strength;

the frequency is inversely proportional to a first time period and a second time period;

the first signal strength during a first time period is different from the first signal strength during the second time period.

4. The system of claim 1 wherein the output signal generator is configured to change the frequency with respect to time within a predetermined frequency range.

5. The system of claim 4 wherein the frequency is associated with a mean frequency for a predetermined time period.

6. The system of claim 1 wherein the first control signal includes a pseudorandom signal.

7. The system of claim 6 wherein the output signal generator is further configured to change the frequency with respect to time based on at least information associated with the pseudorandom signal.

8. The system of claim 7 wherein the frequency changes randomly with respect to time.

9. The system of claim 1 wherein the first control signal is in at least one domain selected from a group consisting of a voltage domain and a current domain.

10. The system of claim 1 wherein the pulse-width-modulation generator is configured to control a switching frequency and a pulse width for a power converter based on at least information associated with the first output signal.

11. The system of claim 1, and further comprising a first controller configured to receive a load signal and generate a second control signal, the load signal indicating an output load for a power converter.

12. The system of claim 11 wherein:

the frequency changes with respect to time;

the frequency is associated with a mean frequency.

13. The system of claim 12 wherein the output signal generator is further configured to receive the second control signal and determine the mean frequency based on at least information associated with the second control signal.

14. The system of claim 1, and further comprising a compensation system configured to receive an input signal for a power converter and generate a third control signal.

15. The system of claim 14 wherein:

the output signal generator is further configured to receive the third control signal and generate a second output signal associated with a slope;

wherein the generate a second output signal includes determine the slope based on at least information associated with the third control signal.

16. The system of claim 15 wherein the pulse-width-modulation generator uses the second output signal to perform a slope compensation for a feedback loop.

17. The system of claim 16 wherein the slope compensation is associated with a slope compensation ratio, the slope compensation ratio being constant with respect to the input signal.

18. The system of claim 14 wherein the compensation system comprises:

a sensing system configured to receive the input signal and generate a fourth control signal;

a compensation controller configured to receive the fourth control signal and output the third control signal.

19. A system for providing a pseudorandom signal, the system comprising:

a shift register configured to receive a first input signal and a second input signal and generate a digital signal, the shift register including m flip-flops, m being a positive integer;

a processing device configured to receive a plurality of signals and generate the first input signal, the plurality of signals representing data stored in a plurality of flip-flops respectively, the plurality of flip-flops being selected from the m flip-flops;

a digital-to-analog converter configured to receive the digital signal and generate an analog signal associated with a signal strength;

wherein;

the digital signal represents at least an N-bit datum, N being a positive integer;

the N-bit datum corresponds to N flip-flops, the N flip-flops being selected from the m flip-flops.

20. The system of claim 19 wherein the processing device is configured to perform an exclusive-OR operation.

21. The system of claim 19 wherein the digital-to-analog converter is further configured to receive a control signal and determine a first range for the signal strength.

22. The system of claim 21, and further comprising:

an output signal generator configured to receive the analog signal and generate at least an output signal associated with a frequency;

a pulse-width-modulation generator configured to receive at least the output signal;

wherein the output signal and the second input signal are the same.

23. The system of claim 22 wherein the frequency changes within a second range, the second range corresponding to the first range.

24. A method for providing frequency control to a power converter, the method comprising:

generating a digital signal, the digital signal associated with at least an N-bit datum, N being a positive integer;

receiving the digital signal;

processing information associated with the digital signal;

generating a first control signal based on at least information associated with the digital signal, the first control signal being an analog signal;

receiving the first control signal;

processing information associated with the first control signal;

generating at least a first output signal related to a frequency based on at least information associated with the first control signal;

wherein the N-bit datum represents a pseudorandom number.

25. The method of claim 24 wherein the generating a digital signal includes generating the digital signal based on at least information associated with the first output signal.

26. The method of claim 24 wherein:

the first output signal is associated with a first signal strength;

the frequency is inversely proportional to a first time period and a second time period;

the first signal strength during a first time period is different from the first signal strength during the second time period.

27. The method of claim 24 wherein the frequency changes with respect to time within a predetermined frequency range.

28. The method of claim 27 wherein the frequency is associated with a mean frequency for a predetermined time period.

29. The method of claim 24 wherein the first control signal includes a pseudorandom signal.

30. The method of claim 29 wherein the frequency changes with respect to time based on at least information associated with the pseudorandom signal.

31. The method of claim 30 wherein the frequency changes randomly with respect to time.

32. The method of claim 24, and further comprising:

processing information associated with the first output signal;

adjusting a switching frequency for a power converter based on at least information associated with the first output signal.

33. A method for providing a pseudorandom signal, the method comprising:

receiving a plurality of signals from a shift register;

processing information associated with the plurality of signals;

generating a first input signal based on at least information associated with the plurality of signals;

receiving the first input signal and a second input signal by the shift register;

processing information associated with the first input signal and the second input signal;

generating a digital signal based on at least information associated with the first input signal and the second input signal by an M-sequence process;

processing information associated with the digital signal;

generating an analog signal related to a signal strength based on at least information associated with the digital signal;

wherein;

the digital signal represents at least an N-bit datum, N being a positive integer;

the N-bit datum represents a pseudorandom number.

34. The method of claim 33 wherein the generating a first input signal includes performing an exclusive-OR operation.

35. The method of claim 33, and further comprising:

receiving a control signal;

processing information associated with the control signal;

determining a first range for the signal strength based on at least information associated with the control signal.

36. The method of claim 35, and further comprising:

receiving the analog signal;

processing information associated with the analog signal;

generating at least an output signal related to a frequency based on at least information associated with the analog signal;

wherein the output signal and the second input signal are the same.

37. The method of claim 36 wherein the frequency changes within a second range, the second range corresponding to the first range.