Switching controller capable of reducing acoustic noise for power converters

Abstract

The present invention provides a switching controller capable of reducing acoustic noise of a transformer for a power converter. The switching controller includes a switching circuit, a comparison circuit, an activation circuit, and an acoustic-noise eliminating circuit. The acoustic-noise eliminating circuit comprises a first-check circuit, a second-check circuit, a pulse-shrinking circuit, and a limit circuit. The first-check circuit receives a switching-current signal which is correlated to a switching current of the power converter and a PWM signal to generate a trigger signal. The second-check circuit receives the trigger signal to generate a control signal. When the frequency of the trigger signal falls into audio band, the control signal will be enabled to limit the switching current. Therefore, the acoustic noise of the transformer can be eliminated.

Dependencies are inferred from the claim text.