Method and apparatus for reducing audio noise in a switching regulator
First Claim
1. A method, comprising:
- switching a power switch coupled to an energy transfer element of the power supply with a drive signal to regulate an amount of power delivered to a load at an output of the power supply;
adjusting a frequency of the drive signal to a frequency value outside an audible frequency range in response to changes in the load;
limiting a current flow through the power switch to one of a plurality of current limit settings in response to the changes in the load to maintain the frequency of the drive signal to a frequency value outside the audible frequency range.
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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
6 Claims
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1. A method, comprising:
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switching a power switch coupled to an energy transfer element of the power supply with a drive signal to regulate an amount of power delivered to a load at an output of the power supply;
adjusting a frequency of the drive signal to a frequency value outside an audible frequency range in response to changes in the load;
limiting a current flow through the power switch to one of a plurality of current limit settings in response to the changes in the load to maintain the frequency of the drive signal to a frequency value outside the audible frequency range. - View Dependent Claims (2, 3, 4, 5, 6)
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Specification