Method and apparatus for reducing audio noise in a switching regulator
First Claim
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1. A circuit, comprising:
- a power switch coupled between a first terminal and a second terminal, the first terminal to be coupled to an energy transfer element of a power supply and the second terminal to be coupled to a supply rail of the power supply;
a drive signal generator circuit coupled to a third terminal to receive an input signal, the drive signal generator to generate a drive signal coupled to control switching of the power switch in response to the input signal to regulate the output of the power supply; and
a current limit circuit coupled to the power switch and the drive signal generator circuit to control the drive signal to limit a current flow through the power switch, the current limit circuit including a state machine having a plurality of states and adapted to send signals to current limit adjustment circuitry included in the current limit circuit to adjust a plurality of current limit settings for the power switch in response to the input signal.
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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.
51 Citations
7 Claims
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1. A circuit, comprising:
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a power switch coupled between a first terminal and a second terminal, the first terminal to be coupled to an energy transfer element of a power supply and the second terminal to be coupled to a supply rail of the power supply;
a drive signal generator circuit coupled to a third terminal to receive an input signal, the drive signal generator to generate a drive signal coupled to control switching of the power switch in response to the input signal to regulate the output of the power supply; and
a current limit circuit coupled to the power switch and the drive signal generator circuit to control the drive signal to limit a current flow through the power switch, the current limit circuit including a state machine having a plurality of states and adapted to send signals to current limit adjustment circuitry included in the current limit circuit to adjust a plurality of current limit settings for the power switch in response to the input signal. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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Specification