METHOD AND DEVICE OF REDUCING AUDIBLE NOISE IN SWITCHING REGULATOR

摘要

PROBLEM TO BE SOLVED: To provide a switching regulator using ON/OFF control reducing audible noise under light load by regulating the current limit of the switching regulator. SOLUTION: In one embodiment, the switching regulator includes a state machine regulating the current limit of the switching regulator based on the pattern of a feedback signal value from the output of a power source to N cycles of preceding drive signals. The state machine regulates the current limit under light load so as to be lower without skipping the cycles in order to reduce an operating frequency range of the switching regulator within an audible frequency range until magnetic flux density passing through a transformer gets sufficiently smaller and generation of the audible noise is reduced.