Method and apparatus for reducing audible acoustical noise in a power supply transformer by shaping the waveform of a primary side inductor current
AssigneeSemiconductor Components Industries, LLC
InventorFrancois L'Hermite
Life of this patent
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Abstract
An apparatus for reducing audible noise in a power supply (16) is provided. The apparatus comprises a shaper circuit (258) located on the secondary side (204) of a transformer (200) that is operable to control the shape of the current through a primary side inductor (222). By changing the shape of the current, acoustical noise is reduced in the transformer (200).
Claims18
An apparatus for reducing acoustical noise in a transformer comprising shape circuit located on the secondary side of the transformer and operable to shape the waveform of a current through a primary side inductor wherein the shaper circuit further comprises:
- an operational amplifier operable to compare an output voltage with a reference voltage;
- an end-of-pulse block operable to initiate an end of pulse signal when the output voltage exceeds the reference voltage;
- and
- a shaper network operable to receive the end of pulse signal and produce an output signal that will shape the current pulse through the primary side inductor.
A method for reducing noise in a transformer comprising:
- shaping the waveform of a current through a primary side inductor until an output voltage exceeds a reference voltage using a start network on a primary side;
- and
- using a secondary side shaper to shape the waveform of the current through the primary side inductor, wherein the step of using a secondary side shaper further comprises
- shaping an input voltage waveform using a shaper network, and
- outputting a shaped voltage after the input voltage exceeds a fixed level, wherein the step of outputting a shaped voltage further comprises producing a sinusoidal shaped current through the primary inductor.
A transformer comprising:
- a primary side including:
- a primary inductor;
- a soft start capacitor operable to control the shape of a current through the primary inductor in the first part of a standby phase;
- and
- a secondary side including:
- a first secondary inductor magnetically coupled to the primary inductor;
- a second secondary inductor magnetically coupled to the primary inductor;
- a third secondary inductor magnetically coupled to the primary inductor;
- a shaper circuit operable to control the shape of a current flowing through a primary inductor in the second part of the standby phase.
Dependencies are inferred from the claim text.