System and method for providing power via a spurious-noise-free switching device

1. A method of generating power from a switching device, the method comprising:

generating an oscillating signal in the form of a series of pulse trains;

randomly changing the switching frequency, or the on-time, or both the switching frequency and the on-time of the switching device;

causing the switching device to change from a first frequency among a plurality of frequencies to a second frequency among the plurality of frequencies only at the end of a pulse train of the first frequency; and

causing the second frequency to start at the beginning of its first pulse train such that no switching duty-cycle disturbance occurs at the time of the change from first to second frequency; and

eliminating spurious noise by ensuring that a spur elimination condition governing the relationship between the plurality of frequencies is satisfied;

wherein the spur elimination condition is satisfied when the ratio of the first frequency multiplied by the number of cycles of its pulse train to any other of the plurality of frequencies equals a rational number that is not an integer.

2. The method of claim 1 , wherein randomly changing the switching frequency of the switching device comprises randomly changing the switching frequency of the switching device after one cycle at each frequency.

3. The method of claim 2 , wherein the spur elimination condition is satisfied when the ratio of the first frequency to any other of the plurality of frequencies equals a rational number that is not an integer.

4. The method of claim 1 , further comprising:

controlling the switching device using pulse-width modulation;

generating an end-of-cycle signal at the end of each pulse train; and

using the end-of-cycle signal to trigger a random number generator whose output determines a frequency of the pulse train.

5. The method of claim 1 , further comprising:

controlling the switching device using pulse-frequency modulation;

generating a beginning-of-pulse signal;

using a delay circuit to generate an end-of-pulse signal; and

using the end-of-pulse signal to trigger a random number counter whose output determines an off-time for each cycle of the pulse train.

6. The method of claim 1 , wherein randomly changing the switching frequency, or the on-time, or both the switching frequency and the on-time of the switching device comprises randomly changing the switching frequency, or the on-time, or both the switching frequency and the on-time of one of a buck converter, a boost converter, flyback converter, an inverting buck-boost converter, and a non-inverting buck-boost converter.

7. The method of claim 1 , wherein randomly changing the switching frequency, or the on-time, or both the switching frequency and the on-time of the switching device comprises randomly changing the switching frequency, or the on-time, or both the switching frequency and the on-time of a Class-D amplifier.

8. The method of claim 1 , wherein randomly changing the switching frequency, or the on-time, or both the switching frequency and the on-time of the switching device comprises randomly changing the switching frequency, or the on-time, or both the switching frequency and the on-time of one of a supply modulator and a polar power amplifier.

9. The method of claim 1 , wherein satisfying the spur elimination condition governing the relationship between the plurality of frequencies results in a reduction in electromagnetic interference (EMI).

10. A method of generating power from a switching device, the method comprising:

generating an oscillating signal in the form of a series of pulse trains;

randomly changing the switching frequency, or the on-time, or both the switching frequency and the on-time of the switching device;

causing the switching device to change from a first frequency among a plurality of frequencies to a second frequency among the plurality of frequencies; and

eliminating spurious noise by ensuring that a spur elimination condition governing the relationship between the plurality of frequencies is satisfied;

wherein the spur elimination condition is satisfied when the ratio of the first frequency multiplied by the number of cycles of its pulse train to any other of the plurality of frequencies equals a rational number that is not an integer.

11. The method of claim 10 , wherein randomly changing the switching frequency of the switching device comprises randomly changing the switching frequency of the switching device after one cycle at each frequency.

12. The method of claim 11 , wherein the spur elimination condition is satisfied when the ratio of the first frequency to any other of the plurality of frequencies equals a rational number that is not an integer.

13. The method of claim 10 , further comprising:

controlling the switching device using pulse-width modulation;

generating an end-of-cycle signal at the end of each pulse train; and

using the end-of-cycle signal to trigger a random number generator whose output determines a frequency of the pulse train.

14. The method of claim 10 , further comprising:

controlling the switching device using pulse-frequency modulation;

generating a beginning-of-pulse signal;

using a delay circuit to generate an end-of-pulse signal; and

using the end-of-pulse signal to trigger a random number counter whose output determines an off-time for each cycle of the pulse train.

15. The method of claim 10 , wherein randomly changing the switching frequency, or the on-time, or both the switching frequency and the on-time of the switching device comprises randomly changing the switching frequency, or the on-time, or both the switching frequency and the on-time of one of a buck converter, a boost converter, flyback converter, an inverting buck-boost converter, and a non-inverting buck-boost converter.