Audio frequency deadband system and method for switch mode regulators operating in discontinuous conduction mode
First Claim
1. A method of reducing audible noise of a switching regulator having a switching period that varies with load conditions, comprising:
- operating the switching regulator in a super-sonic discontinuous conduction mode when the switching period is greater than a first threshold and less than a second threshold;
operating the switching regulator in an audio discontinuous conduction mode when the switching period is at least said second threshold and when a sub-sonic threshold condition is false; and
while operating the switching regulator in the audio discontinuous conduction mode, transitioning to operating the switching regulator in a sub-sonic discontinuous conduction mode when the sub-sonic threshold condition becomes true.
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Accused Products
Abstract
A controller for controlling operation of a switching regulator including a modulator, a discontinuous conduction mode (DCM) controller, an audible DCM (ADCM) controller, and a sub-sonic discontinuous conduction mode (SBDCM) controller. The modulator generally operates in a continuous conduction mode. The DCM controller modifies operation to DCM during low loads. The ADCM controller detects when the switching frequency is less than a super-sonic frequency threshold and modifies operation to maintain the switching frequency at a super-sonic frequency level. The SBDCM controller detects a sub-sonic operating condition during ADCM operation and responsively inhibits operation of the ADCM mode controller to allow a SBDCM mode within a sub-sonic switching frequency range. The SBDCM operating mode allows for efficient connected standby operation. The SBDCM controller allows operation to return to other modes when the switching frequency increases above the sub-sonic level.
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Citations
19 Claims
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1. A method of reducing audible noise of a switching regulator having a switching period that varies with load conditions, comprising:
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operating the switching regulator in a super-sonic discontinuous conduction mode when the switching period is greater than a first threshold and less than a second threshold; operating the switching regulator in an audio discontinuous conduction mode when the switching period is at least said second threshold and when a sub-sonic threshold condition is false; and while operating the switching regulator in the audio discontinuous conduction mode, transitioning to operating the switching regulator in a sub-sonic discontinuous conduction mode when the sub-sonic threshold condition becomes true. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A method to mitigate audible noise during a light load in a synchronous switching regulator operating in a discontinuous conduction mode including a main switch, a synchronous switch and an inductor comprising:
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operating the switching regulator in a variable switching period discontinuous mode while a switching period is below a first switching period threshold in which the switching period increases as the light load decreases; maintaining the switching period at substantially the first switching period threshold while the light load decreases by allowing an inductor current to be negative for a period of time during every switching cycle; operating the switching regulator in the variable switching period discontinuous mode while the variable switching period is above a second switching period threshold which is greater than the first switching period threshold; and preventing the inductor current from going negative while the switching period is above the second switching period threshold.
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Specification