There are four main reasons for switching transformer howling: transformer process problems, transformer loop problems, transformer core problems, and switching power supply load problems, which will be analyzed one by one below.

Process issues of Switching transformer:

① Dipping and drying is not in place, resulting in the magnetic core is not firm enough to cause mechanical vibration and sound;

② The length of the air gap is not suitable, resulting in the unstable working state of the transformer and making noise;

③ If the wire package is not tightly wound, it may cause noise;

④ There is an air gap in the magnetic core combination, which will cause air vibration at high frequencies and make noise (if the transformer is fully immersed in vacuum, it will generally not make a sound).

The loop problem of Switching transformer:

The loop problem of the Switching transformer means that the loop of the transformer oscillates, which causes the transformer to whine.

① The wiring of the circuit board is improper, which causes interference and vibration, resulting in noise;

② Improper setting of the parameters of the feedback loop will cause the loop to be unstable and cause vibration and sound;

The core problem of Switching transformer:

When the transformer core is saturated, the current in the coil increases, the transformer generates heat and generates self-excited oscillation, and the oscillation of the coil causes the vibration of the surrounding air to make a sound.

Load problem of switching power supply:

① In the case of no-load or light-load, the switching power supply will oscillate at some operating points, which is manifested as the howling of the transformer and the instability of the output.

② The transformer is working in a serious overload state, and it may burn out at any time-this is the origin of many power supplies "screaming" before burning out.