Method and apparatus for reducing audio noise in a switching regulator
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Abstract
A switching regulator utilizing on/off control that reduces audio noise at light loads by adjusting the current limit of the switching regulator. In one embodiment, a switching regulator includes a state machine that adjusts the current limit of the switching regulator based on a pattern of feedback signal values from the output of the power supply for a preceding N cycles of the drive signal. The state machine adjusts the current limit lower at light loads such that cycles are not skipped to reduce the operating frequency of the switching regulator into the audio frequency range until the flux density through the transformer is sufficiently low to reduce the generation of audio noise.
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Citations
40 Claims
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1-32. -32. (canceled).
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33. A method, comprising:
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switching a power switch coupled in series with an energy transfer element of a power supply to regulate energy delivered to an output of the power supply;
selecting one of a plurality of states of a state machine in response to the output of the power supply, each one of the plurality of states having respective current limit value; and
limiting a current through the power switch in response to the respective current limit value of the selected one of the plurality of states of the state machine. - View Dependent Claims (34, 35, 36, 37, 38, 39, 40)
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Specification