Techniques to reduce audible noise in a power supply transformer

摘要

This disclosure relates to a switching power supply with regulated voltage suppression to reduce transformer audio noise. A switched mode power supply (SMPS) may supply power at different levels according to output loads. A switching frequency of the SMPS may be adjusted according to the output load. The switching may be subject to a ringing suppression time, a maximum on time, and a maximum switching period. By controlling the switching frequency subject to these quantities, the audible noise of an SMPS may be reduced or eliminated.

主权项

1. A system comprising:
a switching power supply operable to be fed a zero crossing voltage and to generate an output voltage, said output voltage having a voltage level set using a modulated gate signal; a circuit to set a ringing suppression time of the modulated gate signal to a first time period when the zero crossing voltage is below a predetermined voltage threshold and to a second time period when the zero crossing voltage is above the predetermined voltage threshold, the ringing suppression time corresponding to an initial oscillation of the zero crossing voltage caused by the modulated gate signal switching the switching power supply; and a pulse generation circuit that is operable to generate a pulse signal and feed to a counter a pulse train comprising generated pulse signals, wherein the ringing suppression time is operable of being set using an output of the counter or the pulse signal, wherein the output of the counter is selected as the ringing suppression time when input supply voltage falls to a level below the predetermined voltage threshold, and wherein a duration of the pulse generation circuit is selected as the ringing suppression time when the input supply voltage rises to a level above the predetermined voltage threshold, the input supply voltage being the zero crossing voltage.