High frequency transformer is an important part of the isolated switching power supply, and the design of the high-frequency transformer is also a key technology of the switching power supply. In the actual application test, if the design of the high-frequency transformer is not reasonable or the manufacturing process is incorrect, the switching power supply will be damaged. The cause of the failure is the magnetic saturation of the high-frequency transformer.

I.High frequency transformer magnetic saturation test methed:

According to our production experience, the easiest way to test magnetic saturation of high frequency transformers is to use an oscilloscope, which can measure whether the current slope of the primary winding has abrupt changes.

First, a square wave signal of 1 ~ 3kHz is generated by the square wave signal generator, and then the power signal within ± 10 ~ 20V and ± 10A is output through the AC power amplifier with overcurrent protection, and then added to the sampling resistor R0 through the primary winding. Finally, use an oscilloscope to observe the voltage waveform on R0. When magnetic saturation does not occur, the voltage waveform UR0 observed from R0 with an oscilloscope should be a triangular wave voltage. If the observed UR0 waveform shows a small peak voltage at the top, it proves that the current slope of the primary winding begins to change suddenly, thus It is judged that the high frequency transformer reaches the critical magnetic saturation region.

II.Features of oscilloscope testing:

This method uses low voltage and large current to detect the critical magnetic saturation point. The output of the power amplifier can automatically limit the maximum output power. At the same time, the high-frequency transformer does not need to be connected to any peripheral components. It is easy to operate and has good safety.

In addition, there are many ways to prevent magnetic saturation of high-frequency transformers, mainly to appropriately reduce the inductance of the primary winding. When we making the transformer, we can choose a larger core(For example, the current core is EF25, we can change to ER28 ferrite core; if it is EE4215 core, it can be replaced by EE4220 core) and leaving a certain air gap width for the core can also prevent the core from entering the magnetic saturation state.

Your suggestions and opinions are appreciated--"Mycoil is your coil"