US 8,618,881 B2Granted

Class-D power amplifier

AssigneeYamaha Corporation

InventorsToshiro Mayuzumi, Takeshi Togawa

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Abstract

A class-D power amplifier includes a switching power source section, a synchronization signal generation section and a class-D power amplifying section. The synchronization signal generation section takes out of the switching power source section a clock signal having a second frequency which is “n” times of a first frequency. The class-D power amplifying section includes a comparator which compares an input signal with a feedback signal, a second switching section which switches a power source fed from the synchronization signal generation section, a filter section which smoothes an output signal from the second switching section, and a combining section which combines a delayed output signal with a clock signal from the synchronization signal generation section to generate the feedback signal. The class-D power amplifying section is adjusted so as to cause self-oscillating operation at a frequency substantially identical with the second frequency, when a level of the output signal from the filter section is low.

Claims11

Dependent claims

A class-D power amplifier comprising:

a switching power source section that includes:
a first switching section which switches a DC power source output having a predetermined voltage at a first frequency;
a transformer section which inputs an output from the first switching section to a primary coil thereof and takes out a converted output from a secondary coil thereof;
a rectification section which rectifies the converted output taken out of the secondary coil of the transformer section;
and
a feedback section which controls switching of the first switching section by applying a feedback to the first switching section from the rectification section to maintain a voltage of the converted output from the rectification section constant;
a synchronization signal generation section that includes a filter circuit which takes out of the switching power source section a clock signal having a second frequency which is “n” times of the first frequency, wherein “n” is an integer of two or more;
and
a class-D power amplifying section that includes:
a comparator which compares an input signal with a feedback signal;
a second switching section which switches a power source fed from the rectification section according to an output from the comparator;
a filter section which smoothes an output from the second switching section to form an output signal;
and
a combining section which delays a phase of the output signal from the filter section and which combines the delayed output signal with a clock signal from the synchronization signal generation section to generate the feedback signal,
wherein the class-D power amplifying section is tuned so as to cause self-oscillating operation at a frequency which is substantially identical with the second frequency, where a level of the output signal from the filter section is lower than that of the clock signal from the synchronization signal generation section.

12 more elements

Dependencies are inferred from the claim text.