Circuit and method for pulse width modulation by means of synchronized, self-oscillating pulse width modulators
View Patent ↗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.
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.