The following is a summary of the countermeasures against the howling of the power inductor of the DC-DC converter.
Key 1: avoid audible frequency current flowing through human ears
The most basic countermeasure is to avoid the audible frequency current flowing through the human ear.
However, when intermittent operation for the purpose of energy saving and the DC-DC converter with variable frequency mode cannot avoid the energization of the audible frequency of the human ear, please try the following mute countermeasures.
Key 2: no magnetic body is placed around
No magnetic body (shield, etc.) that may be affected by leakage magnetic flux is placed near the inductor. When it is necessary to approach, a shielded inductor (closed magnetic circuit structure) with less leakage magnetic flux shall be used, and attention shall be paid to the placement direction.
Key 3: stagger natural vibration number
Sometimes the howling can be reduced by staggering the natural vibration number or increasing the vibration number. For example, by changing the shape, type, layout, substrate fastening and other conditions of the inductor, the natural vibration number of the whole assembly including the substrate will change. In addition, howling is common in large power inductors with a size of more than 7 mm. By using a small power inductor less than 5mm, the natural vibration number will be increased, and the howling can be reduced.
Key 4: replace with metal integrated molding
As described above, in the full screen type power inductor, the drum core and the shield core attract each other due to magnetism, so that howling occurs at the gap. At the same time, in the unshielded power inductor, the wire vibration caused by leakage magnetic flux will cause howling.
To solve the howling problem of this kind of power inductor, it is an effective solution to replace it with metal integrated type. This is a power inductor which is integrally formed by embedding an air core coil in a soft magnetic metal magnetic powder. Since there is no gap, the magnetic cores will not attract each other. Meanwhile, since the coil is integrated with the magnetic body when the coil is fixed, the problem of winding vibration caused by magnetic flux can also be avoided. In addition, TDK products also use metal magnetic materials with small magnetostriction, so the vibration caused by magnetostriction can be suppressed. It is expected to reduce the howling by replacing unshielded or fully shielded products.
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