Self oscillating modulator
There is described a self oscillating modulator circuit comprising at least two coupled self oscillating loop modules, that achieved a good efficiency and a good linearity.
1. A self-oscillating modulator circuit comprising:
at least two class D self-oscillating loop modules, each module comprising an hysteresis comparator, and each module being configured for receiving a respective input signal and outputting a respective two-level signal;
coupling means connecting said at least two class D self-oscillating loop modules, ahead of the hysteresis comparator of each module, for synchronizing said at least two class D self-oscillating loop modules; and
summing means for summing the respective output signals of each of said at least two class D self-oscillating loop modules and for outputting a multi-level modulated output signal.
2. The circuit according to claim 1 , wherein each of the at least two class D self-oscillating loop modules comprise:
an integrator module, the output of which is connected to the hysteresis comparator;
a class D amplifier, the input of which is connected to the output of the hysteresis comparator; and
a comparator for comparing the input signal of the class D self-oscillating loop module with the output of the class D amplifier, the output of the comparator being connected to the input of the integrator module.
3. The circuit according to claim 1 , wherein the coupling means comprises:
a voltage divider connected between the respective inputs of the hysteresis comparators of the class D self-oscillating loop modules, for coupling said modules.
4. The circuit according to claim 1 ,
wherein said at least two class D self-oscillating loop modules are configured for receiving respective input signals being in phase opposition.
5. An audio amplifier comprising a circuit according to claim 1 .
6. An audio device comprising the audio amplifier according to claim 5 .
7. A method of generating a multi-level modulated output signal in a self-oscillating modulator circuit, the method comprising:
outputting from at least two class D self-oscillating loop modules comprising an hysteresis comparator, respective two-level signals from respective input signals,
coupling said at least two class D self-oscillating loop modules, ahead of the hysteresis comparator of each module, for synchronizing said at least two class D self-oscillating loop modules, and
summing the respective output signals of each of said at least two class D self-oscillating loop modules; and
outputting a multi-level modulated output signal.
8. The method according to claim 7 , wherein each of the at least two class D self-oscillating loop modules comprise an integrator module, the output of which is connected to the hysteresis comparator, and a class D amplifier, the input of which is connected to the output of the hysteresis comparator, the method further comprising:
comparing the input signal of the class D self-oscillating loop module with the output of the class D amplifier, the output of the comparator being connected to the input of the integrator module.
9. The method according to claim 7 , further comprising:
coupling said at least two class D self-oscillating loop modules by a voltage divider which is connected between the respective inputs of the hysteresis comparators of the class D self-oscillating loop modules.
10. The method according to claim 7 , further comprising:
receiving said respective input signals in phase opposition.
11. A self-oscillating modulator circuit comprising:
at least two class D self-oscillating loop modules, each module comprising an hysteresis comparator, and each module being configured to receive a respective input signal and to output a respective two-level signal;
a coupling element which connects said at least two class D self-oscillating loop modules, ahead of the hysteresis comparator of each module, for synchronizing said at least two class D self-oscillating loop modules, and
a summer for summing the respective output signals of each of said at least two class D self-oscillating loop modules and for outputting a multi-level modulated output signal.
12. The circuit according to claim 11 , wherein each of the at least two class D self-oscillating loop modules comprise:
an integrator module, the output of which is connected to the hysteresis comparator;
a class D amplifier, the input of which is connected to the output of the hysteresis comparator; and
a comparator for comparing the input signal of the class D self-oscillating loop module with the output of the class D amplifier, the output of the comparator being connected to the input of the integrator module.
13. The circuit according to claim 11 , wherein said coupling element comprises:
a voltage divider connected between the respective inputs of the hysteresis comparators of the class D self-oscillating loop modules, for coupling said modules.
14. The circuit according to claim 11 ,
wherein each of said at least two class D self-oscillating loop modules are configured for receiving respective input signals being in phase opposition.