Circuit and Method for Pulse Width Modulation by Means of Synchronized, Self-Oscillating Pulse Width Modulators

• US 20070286273A1
• Filed: 06/08/2007
• Published: 12/13/2007
• Est. Priority Date: 06/09/2006
• Status: Active Grant

• Current Assignee: Maxlinear Incorporated
• Original Assignee: Infineon Technologies AG
• Inventors: Walter, Sergio, Clara, Martin, Wiesbauer, Andreas, San Segundo Bello, David, Poetscher, Thomas
• Granted Patent: US 7,486,155 B2
• Time in Patent Office: Days
• US Class Current: 375/238
• CPC Class Codes: H03F 2200/351 Pulse width modulation being used in an amplifying circuit
• CPC Class Codes: H03F 3/217 Class D power amplifiers; Switching amplifiers
• CPC Class Codes: H03K 7/08 Duration or width modulation ; Duty cycle modulation

Abstract

A pulse width modulator circuit has two self-oscillating pulse width modulators and a synchronization circuit for synchronizing the two self-oscillating pulse width modulators. It also comprises an auxiliary-signal generating circuit for generating an auxiliary signal which is coupled into the two self-oscillating pulse width modulators.

Claims

1. A pulse width modulator circuit comprising:

two self-oscillating pulse width modulators;

a synchronization circuit for synchronizing the two self-oscillating pulse width modulators; and

an auxiliary-signal generating circuit for generating an auxiliary signal that is coupled into the two self-oscillating pulse width modulators.

2. The pulse width modulator circuit according to claim 1, wherein the auxiliary-signal generating circuit superimposes the auxiliary signal on input signals of the self-oscillating pulse width modulators.

3. The pulse width modulator circuit according to claim 1, wherein the auxiliary-signal generating circuit couples the auxiliary signal into the self-oscillating pulse width modulators separately from the input signals.

4. The pulse width modulator circuit according to claim 3, wherein:

the self-oscillating pulse width modulators have loop filters; and

the auxiliary-signal generating circuit couples the auxiliary signal into the self-oscillating pulse width modulators via the loop filters.

5. The pulse width modulator circuit according to claim 1, wherein the pulse width modulator circuit couples the auxiliary signal generated by the auxiliary-signal generating circuit to the self-oscillating pulse width modulators only when a signal level of one or both input signals of the self-oscillating pulse width modulators is below a threshold value.

6. The pulse width modulator circuit according to claim 5, wherein the pulse width modulator circuit comprises a measuring circuit for determining the signal level of one or both input signals.

7. The pulse width modulator circuit according to claim 1, wherein the auxiliary-signal generating circuit generates a DC auxiliary signal.

8. The pulse width modulator circuit according to claim 1, wherein the auxiliary-signal generating circuit generates an AC auxiliary signal.

9. The pulse width modulator circuit according to claim 1, wherein the synchronization circuit comprises:

a phase offset detector for determining a quantity that is characteristic of a skew between signal pulse centers of signals generated by the self-oscillating pulse width modulator; and

a frequency control circuit for adjusting frequencies of the self-oscillating pulse width modulators based on the quantity determined.

10. A three-valued pulse width modulator, comprising:

two self-oscillating pulse width modulators;

a synchronization circuit for synchronizing the two self-oscillating pulse width modulators;

a circuit for combining two-valued pulse-width modulated signals generated by the two self-oscillating pulse width modulators into a three-valued pulse-width modulated signal; and

an auxiliary-signal generating circuit for generating an auxiliary signal that is coupled into the two self-oscillating pulse width modulators.

11. The three-valued pulse width modulator according to claim 10, wherein the auxiliary-signal generating circuit superimposes the auxiliary signal on input signals of the self-oscillating pulse width modulators.

12. The three-valued pulse width modulator according to claim 10, wherein the auxiliary-signal generating circuit couples the auxiliary signal into the self-oscillating pulse width modulators separately from the input signals.

13. The three-valued pulse width modulator according to claim 12, wherein:

the self-oscillating pulse width modulators have loop filters; and

the auxiliary-signal generating circuit couples the auxiliary signal into the self-oscillating pulse width modulators via the loop filters.

14. The three-valued pulse width modulator according to claim 10, wherein the three-valued pulse width modulator couples the auxiliary signal generated by the auxiliary-signal generating circuit into the self-oscillating pulse width modulators only when a signal level of one or both input signals of the self-oscillating pulse width modulators is below a threshold value.

15. The three-valued pulse width modulator according to claim 14, wherein the pulse width modulator circuit comprises a measuring circuit for determining the signal level of one or both input signals.

16. The three-valued pulse width modulator according to claim 10, wherein the synchronization circuit comprises:

a phase offset detector for determining a quantity that is characteristic of a skew between signal pulse centers of signals generated by the self-oscillating pulse width modulators; and

a frequency control circuit for adjusting frequencies of the self-oscillating pulse width modulators based on the quantity determined.

17. A pulse width modulator circuit comprising:

two self-oscillating pulse width modulators;

a synchronization circuit that is coupled to synchronization inputs of the two self-oscillating pulse width modulators and synchronizes these; and

an auxiliary-signal generating circuit, outputs of which are coupled to signal inputs of the self-oscillating pulse width modulators and couples an auxiliary signal into the signal inputs of the self-oscillating pulse width modulators.

18. The pulse width modulator circuit according to claim 17, wherein the pulse width modulator circuit couples the auxiliary signal generated by the auxiliary-signal generating circuit into the self-oscillating pulse width modulators only when the signal level of one or both input signals of the self-oscillating pulse width modulators is below a threshold value.

19. The pulse width modulator circuit according to claim 18, wherein the synchronization circuit comprises:

a phase offset detector for determining a quantity that is characteristic of a skew between signal pulse centers of signals generated by the self-oscillating pulse width modulators; and

a frequency control circuit for adjusting frequencies of the self-oscillating pulse width modulators in dependence on the quantity determined.

20. A pulse width modulator circuit comprising:

two self-oscillating pulse width modulators;

a synchronization circuit that is coupled to synchronization inputs of the two self-oscillating pulse width modulators; and

an auxiliary-signal generating circuit, outputs of the auxiliary signal generating circuit being coupled to auxiliary-signal inputs of the self-oscillating pulse width modulators, in order to couple an auxiliary signal into the self-oscillating pulse width modulators, the auxiliary-signal inputs being separate from signal inputs of the self-oscillating pulse width modulators.

21. The pulse width modulator circuit according to claim 20, wherein the pulse width modulator circuit couples the auxiliary signal generated by the auxiliary-signal generating circuit into the self-oscillating pulse width modulators only when the signal level of one or both input signals of the self-oscillating pulse width modulators is below a threshold value.

22. The pulse width modulator circuit according to claim 20, wherein the synchronization circuit comprises:

a phase offset detector for determining a quantity that is characteristic of a skew between signal pulse centers of signals generated by the self-oscillating pulse width modulators; and

a frequency control circuit for adjusting frequencies of the self-oscillating pulse width modulators based on the quantity determined.

23. A circuit arrangement comprising:

a digital data pump;

a digital/analog converter following the digital data pump; and

a pulse width modulator circuit, following the digital/analog converter, the pulse width modulator comprising;

two self-oscillating pulse width modulators; and

a synchronization circuit for synchronizing the two self-oscillating pulse width modulators, wherein;

an auxiliary-signal generating circuit for generating an auxiliary signal that is coupled into the two self-oscillating pulse width modulators is provided in a digital data pump.

24. A method for the pulse width modulation of two signals, the method comprising:

supplying two signals to a self-oscillating pulse width modulator;

coupling an auxiliary signal into the two self-oscillating pulse width modulators; and

synchronizing the two self-oscillating pulse width modulators using the auxiliary signal.

25. The method according to claim 24, wherein the auxiliary signal is superimposed on the input signals of the self-oscillating pulse width modulators.

26. The method according to claim 24, wherein the auxiliary signal is coupled into the self-oscillating pulse width modulators via auxiliary-signal inputs that are provided additionally to the inputs of the input signals.

27. The method according to claim 24, wherein the auxiliary signal is coupled into the self-oscillating pulse width modulators only when the signal level of at least one or both input signals of the self-oscillating pulse width modulators is below a threshold value.

28. A method for generating a three-valued pulse-width modulated signal from two input signals, the method comprising:

supplying each input signal to a self-oscillating pulse width modulator;

coupling an auxiliary signal into the two self-oscillating pulse width modulators;

synchronizing the two self-oscillating pulse width modulators; and

combining the output signals of the self-oscillating pulse width modulators to generate the three-valued pulse-width modulated signal.